Can simple models explain Zipf’s law for all exponents?

H. Simon proposed a simple stochastic process for explaining Zipf’s law for word frequencies. Here we introduce two similar generalizations of Simon’s model that cover the same range of exponents as the standard Simon model. The mathematical approach followed minimizes the amount of mathematical background needed for deriving the exponent, compared to previous approaches to the standard Simon’s model. Reviewing what is known from other simple explanations of Zipf’s law, we conclude there is no single radically simple explanation covering the whole range of variation of the exponent of Zipf’s law in humans. The meaningfulness of Zipf’s law for word frequencies remains an open question.Peer ReviewedPostprint (published version

Decoherence of spin qubits due to a nearby charge fluctuator in gate-defined double dots

The effects of a nearby two-level charge fluctuator on a double-dot two-spin qubit are studied theoretically. Assuming no direct tunneling between the charge fluctuator and the qubit quantum dots, the Coulomb couplings between the qubit orbital states and the fluctuator are calculated within the Hund-Mulliken framework to quadrupole-quadrupole order in a multipole expansion. We identify and quantify the coupling term that entangles the qubit to the fluctuator and analyze qubit decoherence effects that result from the decay of the fluctuator to its reservoir. Our results show that the charge environment can severely impact the performance of spin qubits, and indicate working points at which this decoherence channel is minimized. Our analysis also suggests that an ancillary double-dot can provide a convenient point for single-qubit operations and idle position, adding flexibility in the quantum control of the two-spin qubit.Comment: 19 pages, 9 figure

A new approach to texture coding using stochastic vector quantization

A new method for texture coding which combines 2-D linear prediction and stochastic vector quantization is presented in this paper. To encode a texture, a linear predictor is computed first. Next, a codebook following the prediction error model is generated and the prediction error is encoded with VQ, using an algorithm which takes into account the pixels surrounding the block being encoded. In the decoder, the error image is decoded first and then filtered as a whole, using the prediction filter. Hence, correlation between pixels is not lost from one block to another and a good reproduction quality can be achieved.Peer ReviewedPostprint (published version

Disclination-mediated thermo-optical response in nematic glass sheets

Nematic solids respond strongly to changes in ambient heat or light, significantly differently parallel and perpendicular to the director. This phenomenon is well characterized for uniform director fields, but not for defect textures. We analyze the elastic ground states of a nematic glass in the membrane approximation as a function of temperature for some disclination defects with an eye towards reversibly inducing three-dimensional shapes from flat sheets of material, at the nano-scale all the way to macroscopic objects, including non-developable surfaces. The latter offers a new paradigm to actuation via switchable stretch in thin systems.Comment: Specific results for spiral defects now added. References to Witten, Mahadevan and Ben Amar now added

The discovery of a highly polarized bipolar nebula

During a search for the optical counterparts of IRAS sources whose flux peaks at 25 microns, a small faint bipolar nebula was discovered in Monoceros at the position of IRAS 07131-0147. The CCD images display the object's considerable structure. The central star seems relatively free of closeby nebulosity: the two lobes have a bow-tie structure with those parts nearest to the star consisting of series of small knots. The outer parts of the lobes seem to be made up of filaments streaming away from knots. On the basis of its optical spectrum, the central star was classified as a M5-6 giant. In the IRAS color classification scheme of Van der Veen and Habing (1988), the central star is VIb which indicates that there are distinct hot and cold components of circumstellar dust and that the mass loss process may have temporarily abated. Therefore, it is proposed that the object is in the post main sequence stage of evolution and is a protoplanetary nebulae. Young protoplanetary nebulae have totally obscured central stars illuminating reflective lobes whereas older ones such as M2-9 have lobes seen in emission from gas ionized by the central hot star which is clearly visible. Since the central object of IRAS07131-0147 is a relatively unobscured late type star and the lobes are seen only by reflection, it is suggested that this nebula is a protoplanetary nebula in an evolutionary stage intermediate between that of CRL2688 and M2-9

Discurso de su excelencia, el embajador de la República de Los Cocos, ante la Asamblea Internacional

Discurso de su excelencia, el embajador de la República de Los Cocos, ante la Asamblea Internacional. Cantinflas en "Su Excelencia", México, 1967. Lopitos (Cantinflas) es un simple burócrata de la República de los Cocos. Sin embargo, la nación se ve envuelta en una serie de cambios en el poder donde el mismo Lopitos termina siendo nombrado como embajador. El nuevo dignatario enfrentará el conflicto entre los dos grandes bloques del poder: los "verdes" y "colorados" quienes, encabezados por Dolaronia (Obviamente EEUU) y Pepeslavia (Apuntando a José Stalin de la URSS), necesitan el voto del nuevo emisario en una asamblea internacional para dominar el mundo. El momento cúlmen de la película es cuando Lopitos tiene la posibilidad de dar un discurso oficial ante los "representantes del mundo", ya que aprovechará de hacer una crítica a los modelos económicos socialista y capitalista imperantes en los tiempos de la guerra fría, y a los comportamientos de las superpotencias Unión Soviética y Estados Unidos.Universidad Tecnológica de El Salvado

Esquizofrenia vs. acción cultural : una aproximación a la realidad contemporánea

Qué sucede en el mundo moderno con las instituciones que tienen como deber influir y guiar con una filosofía y verdades que le den sentido a la vida? De muchas formas se viene constatando que se ha perdido el sentido místico de la superación personal y hacia lo superior, que es la- base principal de todas las instituciones religiosas. -la pregunta es: "¿qué es lo que está pasando?" "¿qué ha hecho o están haciendo los líderes en estos campos tan importantes para la vida: y la superación del ser humano?" Y esto se observa en muchas religiones en el mundo entero. Al contrario de lo que se espera, las religiones se han vuelto o muy laicas o muy conservadoras, hasta llegar a extremos fundamentalistas pregonando una verdad única.Universidad Tecnológica de El Salvado