On the impossibility of representing infinite utility streams

We show that, independently of the topology chosen on the set of all infinity utility streams, there is no Social Welfare Function preserving the von Weizsäcker’s overtaking criterion. With our proof we extend the impossibility result of Basu and Mitra

Features of spin-charge separation in the equilibrium conductance through finite rings

We calculate the conductance through rings with few sites $L$ described by the $t-J$ model, threaded by a magnetic flux $\Phi$ and weakly coupled to conducting leads at two arbitrary sites. The model can describe a circular array of quantum dots with large charging energy $U$ in comparison with the nearest-neighbor hopping $t$. We determine analytically the particular values of $\Phi$ for which a depression of the transmittance is expected as a consequence of spin-charge separation. We show numerically that the equilibrium conductance at zero temperature is depressed at those particular values of $\Phi$ for most systems, in particular at half filling, which might be easier to realize experimentally.Comment: 8 pages, 7 figure

Putative morphometric evidence of the presence of Acipenser naccarii Bonaparte, 1836 in Iberian rivers, or why ontogenetic allometry needs adequate treatment

He ampliado mi análisis inicial (Rincón, 2000) de los datos publicados sobre la morfometría de esturiones procedentes de aguas de la península Ibérica y de una piscifactoría, presentados como prueba del carácter nativo tanto de Acipenser naccarii Bonaparte, 1836 como de Acipenser sturio L., 1758 en la cuenca del Guadalquivir (Garrido-Ramos et al., 1997), aplicando las mismas técnicas uni- y multivariantes de ajuste de alometrías a una base de datos ampliada con un mayor número de ejemplares de A. naccarii. Como ya ocurrió, la representación gráfica de las diversas medidas cefálicas frente a la longitud total (todas transformadas a logaritmos) y de los componentes principales extraídos por ACP, realizados usando tanto la matriz de covarianza como la de correlación, no ofrecieron indicación alguna de la existencia de dos grupos morfológicamente distintos dentro de los esturiones capturados en aguas de la Península. Además, el relativamente débil (en cuanto a proporción de la varianza total que asumía) gradiente en la anchura del morro que separaba al único ejemplar de piscifactoría de los esturiones salvajes que hallé (Rincón, 2000), fue identificado de nuevo, ahora evidente y nítido, por todas las técnicas anteriores. Finalmente, un AFD mostró que tal diferencia permitía una casi perfecta, altamente significativa, distinción entre los especímenes de piscifactoría y los salvajes, mientras que no hubo gradiente morfométrico estadísticamente significativo que separase los supuestos dos grupos de esturiones salvajes ibéricos. El examen en la base de datos ampliada de las dos variables compuestas que Garrido-Ramos et al. (1997) usaron para distinguir tales dos grupos, confirmó que ambas se hallan gravemente influidas por la alometría ontogenética, llevando, por tanto, a la asignación de los ejemplares grandes o pequeños a grupos distintos. Concluyo, pues, que no hay evidencia morfológica alguna que apoye el supuesto carácter de especie autóctona de A. naccarii en la península Ibérica.I have extended my initial analyses (Rincón, 2000) of a published morphometric data set of sturgeons caught in Iberian rivers and from a fish farm, claimed to prove the native status of both Acipenser naccarii Bonaparte, 1836 and Acipenser sturio L., 1758 in the Guadalquivir basin (Garrido- Ramos et al., 1997), by applying the same uni- and multivariate techniques for allometric adjustment to a database expanded with further A. naccarii specimens. As previously, neither log-log scatterplots of head measurement vs. total length, nor graphical representation of the scores of individual specimens on the principal components (PC) extracted by PCAs performed on the covariance and correlation matrix, respectively, offered any suggestion of the existence of two morphologically dissimilar groups within wild Iberian sturgeons. In addition, the relatively weak (in terms of total variance accounted for) gradient in snout width that separated the one farmed Adriatic sturgeon from the wild fish found in my previous work (Rincón, 2000) was again detected, now clear and distinct, by all those techniques. Furthermore, a DFA showed that such dissimilarity produced almost perfect, highly statistically significant discrimination between farmed and wild fish, while there was no significant gradient separating the two supposed groups of wild Iberian sturgeons. Examination of the two composite variables that Garrido-Ramos et al. (1997) used to separate those groups in the extended database confirmed that they were negatively affected by ontogenetic allometry, therefore leading to the ascription of large and small specimens to different groups. I conclude that there is no morphological evidence to support the claimed autocthonous status of A. naccarii in the Iberian Peninsula.Instituto Español de Oceanografí

On the impossibility of representing infinite utility streams

We show that, independently of the topology chosen on the set of all infinity utility streams, there is no Social Welfare Function preserving the von Weizsäcker’s overtaking criterion. With our proof we extend the impossibility result of Basu and Mitra.

Optical Absorptivity versus Molecular Composition of Model Organic Aerosol Matter

Aerosol particles affect the Earth’s energy balance by absorbing and scattering radiation according to their chemical composition, size, and shape. It is generally believed that their optical properties could be deduced from the molecular composition of the complex organic matter contained in these particles, a goal pursued by many groups via high-resolution mass spectrometry, although: (1) absorptivity is associated with structural chromophores rather than with molecular formulas, (2) compositional space is a small projection of structural space, and (3) mixtures of polar polyfunctional species usually exhibit supramolecular interactions. Here we report a suite of experiments showing that the photolysis of aqueous pyruvic acid (a proxy for aerosol α-dicarbonyls absorbing at λ > 300 nm) generates mixtures of identifiable aliphatic polyfunctional oligomers that develop absorptions in the visible upon standing in the dark. These absorptions and their induced fluorescence emissions can be repeatedly bleached and retrieved without carbon loss or ostensible changes in the electrospray mass spectra of the corresponding mixtures and display unambiguous signatures of supramolecular effects. The nonlinear additivity of the properties of the components of these mixtures supports the notion that full structural speciation is insufficient and possibly unnecessary for understanding the optical properties of aerosol particles and their responses to changing ambient conditions

Spin-charge separation in strongly interacting finite ladder rings

We study the conductance through Aharonov-Bohm finite ladder rings with strongly interacting electrons, modelled by the prototypical t-J model. For a wide range of parameters we observe characteristic dips in the conductance as a function of magnetic flux, predicted so far only in chains which are a signature of spin and charge separation. These results open the possibility of observing this peculiar many-body phenomenon in anisotropic ladder systems and in real nanoscopic devices.Comment: 4 pages, 6 figure

The lattice R-tors for perfect rings

We define ̃F in R-tors by r ̃F σ iff the class of r-codivisible modules coincides with the class of σ -codivisible modules. We prove that if R is left perfect ring (resp. semiperfect ring) then every [r] f Є R-tors/ ̃F (resp. [X]F and [ε]F) is a complete sublattice of R-tors We describe the largest element in [r] as X(Rad R/t,(Rad R)) and the least element of [r] as ε (t r(RadR)) Using these results we give a necessary and sufficient condition for the central splitting of Goldman torsion theory when R is semiperfect. We prove that for a QF ring R the least element of [X] ̃F is the Goldie torsion theory. This can be used to prove that for a QF ring ̃F and ̃T are equal, where r ̃T o iff the class of r-injective modules coincides with the class of σ-injective modules

Thermochromism of Model Organic Aerosol Matter

Laboratory experiments show that the optical absorptivity of model organic matter is not an intrinsic property, but a strong function of relative humidity, temperature, and insolation. Suites of representative polyfunctional C_(x)H_(y)O_(z) oligomers in water develop intense visible absorptions upon addition of inert electrolytes. The resulting mixtures reach mass absorption cross sections σ(532 nm) ~ 0.1 m^(2)/gC in a few hours, absorb up to 9 times more solar radiation than the starting material, can be half-bleached by noon sunlight in ~ 1 h, and can be repeatedly recycled without carbon loss. Visible absorptions red-shift and evolve increasingly faster in subsequent thermal aging cycles. Thermochromism and its strong direct dependences on ionic strength and temperature are ascribed to the dehydration of >CH−C(OH)C═C< unsaturations by a polar E1 mechanism, and bleaching to photoinduced retrohydration. These transformations are deemed to underlie the daily cycles of aerosol absorption observed in the field, and may introduce a key feedback in the earth’s radiative balance

A Grammar Compression Algorithm based on Induced Suffix Sorting

We introduce GCIS, a grammar compression algorithm based on the induced suffix sorting algorithm SAIS, introduced by Nong et al. in 2009. Our solution builds on the factorization performed by SAIS during suffix sorting. We construct a context-free grammar on the input string which can be further reduced into a shorter string by substituting each substring by its correspondent factor. The resulting grammar is encoded by exploring some redundancies, such as common prefixes between suffix rules, which are sorted according to SAIS framework. When compared to well-known compression tools such as Re-Pair and 7-zip, our algorithm is competitive and very effective at handling repetitive string regarding compression ratio, compression and decompression running time

Ionic behavior assessment of surface-active compounds from corn steep liquor by exchange resins

Depending on their ionic nature, biosurfactants can be classified as nonionic, anionic, cationic, or amphoteric. The ionic behavior of biosurfactants is an important characteristic that dictates their use in industrial applications. In this work, a biosurfactant extract obtained from corn steep liquor was subjected to anionic or cationic resins, in order to study the ionic behavior under different operational conditions using response surface methodology. The independent variables included in the study are the dilution of biosurfactant solution, the amount of cationic or anionic resin, and the extraction time, whereas the dependent variables studied consisted of the surface tension of biosurfactant aqueous solution, after contacting with anionic or cationic resin. The results showed that biosurfactant extracted from corn steep liquor is amphoteric, since both resins were able to entrap this biosurfactant, making it particularly suited for use in personal care preparations for sensitive skin.Peer ReviewedPostprint (author's final draft