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Papers by Cristian Esteban Neira Rivera

Revista Latinoamericana De Hipertension, Jun 29, 2018

Las enfermedades del area colorrectal cada vez son mas frecuentespor multiples razones. Las patol... more Las enfermedades del area colorrectal cada vez son mas frecuentespor multiples razones. Las patologias mas incidentesen dicha area son el cancer de colon y recto, referente alas cuales diferentes estudios han reportado la importanciaque poseen los sistemas de puntuacion para la valoraciondel paciente que sera sometido a la cirugia. Estos sistemasde puntuacion poseen diferentes factores que son capacesde interaccionar entre ellos mismos, con el fin de disminuirel riesgo de complicaciones durante y posterior a la cirugia.Dentro de los factores de riesgo asociados a una evoluciontorpida en la cirugia colorrectal se encuentran: la edad, elsexo, cirugia abdominal previa, valor de las puntuaciones deriesgo predictivo existentes, la obesidad, comorbilidades ylimpieza del intestino previa a la cirugia e incision abdominal,los cuales se exponen en la siguiente revision bibliografica.

Tecnura, 2013

Algunos metodos de calculo en el flujo espa-cialmente variado generan incertidumbre por la variab... more Algunos metodos de calculo en el flujo espa-cialmente variado generan incertidumbre por la variabilidad de la formulacion. En el caso de vertederos laterales de seccion constante en canales prismaticos con descarga decreciente, algunas de las formulas difieren en su forma y resultados, por la naturaleza y desarrollo de los calculos. Por lo tanto, en este articulo se estudian soluciones para unificar criterios, con ayuda del analisis dimensional, mediciones de laboratorio y modelos teoricos de investigaciones realizadas en Chile, Italia y Colombia.En esta publicacion se emplea el teorema n de Vaschy-Buckingham, que utiliza los principios del analisis dimensional para la solucion de problemas fisicos.

This research was based on the preparation of a production car to be used, on the street, as well... more This research was based on the preparation of a production car to be used, on the street, as well as in amateur competitions as Mountain climbs, Trackdays and Drag racing, in order to improve performance and achieve results in terms of increased power performance, stability, braking and safety. The project was framed on the basis of searching and demanding to have a modified vehicle prepared to fulfill appropriate safety standards, as well as the environmental and traffic rules that govern our country, using automotive knowledge learned during the past four years and several modifications to standard cars. Data compilation of the best manufacturers of each segment were used for the development of the project to obtain the required improvements by combining highest quality parts in the international market, resulting in the desired outcome of this project. Thus, it was concluded that the combining of all the systems used in this project emerge an everyday car capable of delivering more power along with stability and security, in order to race with any high-end sport car.

Congreso De Economia Administracion Y Tecnologia, Oct 10, 2014

The Scientific World Journal, 2015

We associate some (old) convergent series related to definite integrals with the cyclotomic equat... more We associate some (old) convergent series related to definite integrals with the cyclotomic equationxm-1=0, for several natural numbersm; for example, form=3,x3-1=(x-1)(1+x+x2)leads to∫01dx(1/(1+x+x2))=π/(33)=(1-1/2)+(1/4-1/5)+(1/7-1/8)+⋯. In some cases, we express the results in terms of the Dirichlet characters. Generalizations for arbitrarymare well defined but do imply integrals and/or series summations rather involved.

Reports on Mathematical Physics, 2013

Regular polytopes, the generalization of the five Platonic solids in 3 space dimensions, exist in... more Regular polytopes, the generalization of the five Platonic solids in 3 space dimensions, exist in arbitrary dimension n ≥ −1; now in dim. 2, 3 and 4 there are extra polytopes, while in general dimensions only the hyper-tetrahedron, the hyper-cube and its dual hyper-octahedron exist. We attribute these peculiarites and exceptions to special properties of the orthogonal groups in these dimensions: the SO(2) = U(1) group being (abelian and) divisible, is related to the existence of arbitrarilysided plane regular polygons, and the splitting of the Lie algebra of the O(4) group will be seen responsible for the Schläfli special polytopes in 4-dim., two of which percolate down to three. In spite of dim. 8 being also special (Cartan's triality), we argue why there are no extra polytopes, while it has other consequences: in particular the existence of the three division algebras over the reals R: complex C, quaternions H and octonions O is seen also as another feature of the special properties of corresponding orthogonal groups, and of the spheres of dimension 0,1,3 and 7.

Pramana, 2009

We propose to substitute Newton's constant G N for another constant G 2 , as if the gravitational... more We propose to substitute Newton's constant G N for another constant G 2 , as if the gravitational force would fall off with the 1/r law, instead of the 1/r 2 ; so we describe a system of natural units with G 2 , c and. We adjust the value of G 2 so that the fundamental length L = L Pl is still the Planck's length and so GN = L × G2. We argue for this system as (1) it would express longitude, time and mass without square roots; (2) G 2 is in principle disentangled from gravitation, as in (2 + 1) dimensions there is no field outside the sources. So G 2 would be truly universal; (3) modern physics is not necessarily tied up to (3 + 1)-dim. scenarios and (4) extended objects with p = 2 (membranes) play an important role both in M-theory and in F-theory, which distinguishes three (2, 1) dimensions. As an alternative we consider also the clash between gravitation and quantum theory; the suggestion is that non-commutative geometry [xi, xj] = Λ 2 θij would cure some infinities and improve black hole evaporation. Then the new length Λ shall determine, among other things, the gravitational constant G N .

Physics of Particles and Nuclei, 2011

We make an attempt to describe the spectrum of masses of elementary particles, as it comes out em... more We make an attempt to describe the spectrum of masses of elementary particles, as it comes out empirically in six distinct scales. We argue for some rather well defined mass scales, like the electron mass: it seems to us that there is a minimum mass associated to any electric charge, so we elaborate on this assumption; indeed, some scales of masses will cover also masses of composite particles or mass differences. We extend some plausibility arguments for other scales, as binding or self-energy effects of the microscopic forces, plus some speculative uses, here and there, of gravitation. We also consider briefly exotics like supersymmetry and extra dimensions in relation to the mass scale problem, including some mathematical arguments (e.g. triality), which might throw light on the three-generation problem. The paper is rather tentative and speculative and does not make many predictions, but it seems to explain some features of the particle spectrum.

Blood, 2003

It has been proposed that paroxysmal nocturnal hemoglobinuria (PNH) cells may proliferate through... more It has been proposed that paroxysmal nocturnal hemoglobinuria (PNH) cells may proliferate through their intrinsic resistance to immune attack. To evaluate this hypothesis, we examined the impact of alloimmune pressure on PNH and normal cells in the clinical setting of nonmyeloablative allogeneic hematopoietic cell transplantation (HCT). Five patients with severe PNH underwent HCT from an HLA-matched family donor after conditioning with cyclophosphamide and fludarabine. PNH neutrophils (CD15+/CD66b–/CD16–) were detected in all patients at engraftment, but they subsequently declined to undetectable levels in all cases by 4 months after transplantation. To test for differences in susceptibility to immune pressure, minor histocompatibility antigen (mHa)–specific T-cell lines or clones were targeted against glycosylphosphatidylinositol (GPI)–negative and GPI-positive monocyte and B-cell fractions purified by flow cytometry sorting. Equivalent amounts of interferon-γ (IFN-γ) were secreted...