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Search Results: 1 - 10 of 215765 matches for " Carlos E; "
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Cyanopolyynes as Organic Molecular Wires in the Interstellar Medium  [PDF]
Raul G. E. Morales, Carlos Hernández
International Journal of Astronomy and Astrophysics (IJAA) , 2012, DOI: 10.4236/ijaa.2012.24030
Abstract: Cyanopolyynes (H[C≡C]n-CN or HC2n+1N, where n = 1, 2, 3, …, n) are commonly observed in the interstellar medium (ISM) as well as in the envelopes of carbon-rich stars. These linear molecular structures can be well described with a one-dimensional conduction model, which considers the scattering processes of electrons through the charge transfer conduction bridge of the H[C≡C]n-molecular wire containing the CN group as an electron-acceptor terminal unit. Therefore, our results using this model enable a better understanding of the longest molecules observed in interstellar space and provide new insight into why these particular cyanopolyynes reach a maximum length, such as is observed from astronomical experimental spectral data and cosmological chemical models. Dipole moments and geometrical parameters of these cyanopolyynes were obtained from ab initio molecular orbital calculations using the restricted Hartree-Fock approach and 6-311G* basis set, in order to obtain the inner resistance as a new parameter of chemical reaction feasibility for this molecular series. Using this last molecular parameter, we have been able to analyze the possibility of identifying long molecular species that can be found under local thermodynamic equilibrium in some ISM such us HC25H, HC27H, and HC29N, which have not been observed at present.
Expected Radial Column Density of Methylcyanopolyynes in CW Leonis (IRC+10216)  [PDF]
Raul G. E. Morales, Carlos Hernández
International Journal of Astronomy and Astrophysics (IJAA) , 2015, DOI: 10.4236/ijaa.2015.53018
Abstract: Methylcyanopolyynes (CH3-[C≡C]n-CN) are a particular kind of linear molecular wires, where the first three oligomers have been detected in the interstellar medium, particularly in CW Leonis (IRC + 10216), as well as in the envelopes of carbon-rich stars in a similar way to the unsubstituted cyanopolyynes. Based on the projected natural distribution in cold clouds under LTE, we have determined the radial column density of new expected methylcyanopolyynes to be present in CW Leonis (IRC + 10216). By following, we have made use of the inner molecular resistances of the internal charge transfer process presenting in these oligomeric species in order to determine the reactivity trends between them. Therefore, geometrical parameters and dipole moments determinations for these methylcyanopolyynes involving the n = 1 to 14 molecular species were obtained from Ab initio molecular orbital calculations by means of a GAUSSIAN Program, using a restricted Hartree-Fock approach and 6-311G* basis set. Our results present a similar behavior observed in cyanopolyynes, where this series reaches a saturation level at the 14th oligomer with a maximum dipole moment of 8.21 ± 0.01 (Debyes). Thus, this molecular wire model permits us to comprehend how these methylcyanopolyynes reach a maximum length in such chemical environment, in agreement to the astronomical observations and cosmological chemical models. The following CH3C9N and CH3C11N oligomers in CW Leonis should be expected near to 3.52 × 1010 [cm2] and 1.82 × 1010 [cm2], respectively.
Alternative Derivation of the Mean-Field Equations for Composite Fermions  [PDF]
Edmundo C. Manavella, Carlos E. Repetto
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.612175
Abstract: The Hamiltonian describing a composite fermion system is usually presented in a phenomenological way. By using a classical nonrelativistic U(1) × U(1) gauge field model for the electromagnetic interaction of electrons, we show how to obtain the mean-field Hamiltonian describing composite fermions in 2 + 1 dimensions. In order to achieve this goal, the Dirac Hamiltonian formalism for constrained systems is used. Furthermore, we compare these results with the ones corresponding to the inclusion of a topological mass term for the electromagnetic field in the Lagrangian.
Can We Build Artificial Stem Cell Compartments?
Carlos E. Semino
Journal of Biomedicine and Biotechnology , 2003, DOI: 10.1155/s1110724303208019
Abstract: Animals carry stem cells throughout their entire life, from embryogenesis to senescence. Their function during development and adulthood consists basically of forming and sustaining functional tissues while maintaining a small self-renewing population. They reside in a complex three-dimensional environment consisting of other nearby cells extracellular matrix components, endogenous or exogenous soluble factors, and physical, structural, or mechanical properties of the tissues they inhabit. Can we artificially recreate tissue development such that stem cells can both self-renew and be instructed to mature properly? The main factors required to regulate the maintenance and differentiation of some types of stem cells are known. In addition, new bioengineered synthetic materials that mimic extracellular matrix components can be used as initial scaffolding for building stem cell microenvironments.
The role for autopsy in the intensive care unit: technological considerations
Carlos E Pompilio
Critical Care , 2010, DOI: 10.1186/cc9075
Abstract: The author declares that they have no competing interests.
On the origins of arrestin and rhodopsin
Carlos E Alvarez
BMC Evolutionary Biology , 2008, DOI: 10.1186/1471-2148-8-222
Abstract: We found that the arrestin clan is comprised of the Spo0M protein family in archaea and bacteria, and the arrestin and Vps26 families in eukaryotes. The previously known animal arrestins are members of the visual/beta subfamily, which branched from the founding "alpha" arrestins relatively recently. Curiously, we identified both the oldest visual/beta arrestin and opsin genes in Cnidaria (but not in sponges). The arrestin clan has 14 human members: 6 alphas, 4 visual/betas, and 4 Vps26 genes. Others recently showed that the 3D structure of mammalian Vps26 and the biochemical function of the yeast alpha arrestin PalF are similar to those of beta arrestins. We note that only alpha arrestins have PY motifs (known to bind WW domains) in their C-terminal tails, and only visual/betas have helix I in the Arrestin N domain.We identified ciliary opsins in Cnidaria and propose this subfamily is ancestral to all previously known animal opsins. That finding is consistent with Darwin's theory that eyes evolved once, and lends some support to Parker's hypothesis that vision triggered the Cambrian explosion of life forms. Our arrestin findings have implications on the evolution of GPCR signaling, and on the biological roles of human alpha arrestins.G protein coupled receptors (GPCRs) are arguably the most important proteins in human evolution and medicine [1]. The rhodopsin class of GPCRs alone is the most highly represented protein family in mammals [2]. Humans have on the order of 799 [3] to 1,282 [4] GPCRs, and they are the protein family most commonly targeted by clinical drugs. GPCRs are transmembrane receptors that mediate the majority of extracellular signaling in mammals. They can sense diverse types of signals, including hormones, lipids, olfactants, tastants, ions, light, and soluble and surface-anchored peptides. Despite the name, not all GPCRs signal through G proteins. And many or most GPCRs also signal through non-G protein-mediated pathways. The hallmark of GPCRs is
MáS ALLá DE LA SELECCIóN NATURAL
SARMIENTO M,CARLOS E;
Acta Biológica Colombiana , 2009,
Abstract: the explanation of the evolution of organisms through natural selection is the nucleus of the system of concepts of the biology thanks to is simplicity, its explanatory power and its coherence with an impressive amount of data. however, in some cases this model has become a by default discourse that does not allow to penetrate and discover much more complex processes. this difficulty has been pointed out by several authors and the present paper summarizes several of the alternatives or delimitations at several levels: the consequences of genetic neutralism are explored. the implications of the complex relationship between genotype and phenotype are studied since these may made difficult the use of simple genetic models for the study of evolution by natural selection. the proposal of extending a neutral model for morphological traits through the concept of functional equivalence is discussed. some of the controversial aspects of the use of the concept of adaptation are analyzed and the insightful effect of including the phylogenetic history in the explanation of the origin of the proposed adaptive characters is discussed. the consequences of these analyses are reviewed in four areas: adaptation, species definition, phylogenetic reconstructions and conservation. at no point this document denies the value of the model of evolution by natural selection but points out the importance of alternative models strongly supported by data rigorously analyzed.
A economia política da popula??o: poder e demografia no pensamento econ?mico britanico do século XVII
Suprinyak, Carlos E.;
Economia e Sociedade , 2008, DOI: 10.1590/S0104-06182008000300002
Abstract: in his lectures on governmentality, foucault argued that early modern period's political theorizing was characterized by a gradual change in the object of political power, from territories to populations. we try to link this idea to the development of seventeenth-century british economic thought, in which notions of population management are constantly present - beginning with early pamphleteers like mun and misselden, developing along the subsequent decades in a close relationship with doctrines such as the "political arithmetic" envisaged by petty, and culminating in the extensive use made by davenant of the demographic statistics compiled by gregory king. moreover, we try to expose the connection between demographic themes and some key concepts then adopted, in an effort to show that they were not mere subsidiaries to military concerns, but instead were a direct corollary to a widespread notion of labor as a creative force arguably the rudimentary origins of a labor theory of value.
águas urbanas
Tucci, Carlos E. M.;
Estudos Avan?ados , 2008, DOI: 10.1590/S0103-40142008000200007
Abstract: urban waters systems generally include both water supply & sanitation facilities (wss). sanitation refers to domestic and industrial sewage collecting and treatment; it does not include urban stormwater or solid waste management systems. urban water form components of a sustainable urban environment and the use of the integrated water resource management (iwrm) concepts are needed for planning, implementation and maintenance of urban infrastructure. in urban environment, iwrm is referred to specifically as integrated urban water management (iuwm). in this paper urban development and its relations with urban waters in brazil are assessed. management of water resources in brazil is developed by basins and the administration is federal or from the state. this article assess the alternatives of water management in the city and the basin in the brazilian institutional environment.
El devenir de Hegel hacia la Fenomenología del Espíritu
Rendón,Carlos E;
Ideas y Valores , 2008,
Abstract: this paper seeks to reconstruct the possible steps followed by hegel toward his phenomenology of mind. taking into account the historical variants of the process, this paper will try to determine the meaning and the relationship between these variants and the philosophical consolidation of the book. the development of the text does not follow a linear evolution, but rather shows unexpected but comprehensible continuities and ruptures. these contingencies will be decisive for some of the main formulations of the book itself, showing it as a “result” in the more hegelian sense of the word: as that which is intrinsically linked to its becoming.
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