Rational deformations of conformal mechanics

We study deformations of the quantum conformal mechanics of De Alfaro-Fubini-Furlan with rational additional potential term generated by applying the generalized Darboux-Crum-Krein-Adler transformations to the quantum harmonic oscillator and by using the method of dual schemes and mirror diagrams. In this way we obtain infinite families of isospectral and non-isospectral deformations of the conformal mechanics model with special values of the coupling constant $g=m(m+1)$, $m\in {\mathbb N}$, in the inverse square potential term, and for each completely isospectral or gapped deformation given by a mirror diagram, we identify the sets of the spectrum-generating ladder operators which encode and coherently reflect its fine spectral structure. Each pair of these operators generates a nonlinear deformation of the conformal symmetry, and their complete sets pave the way for investigation of the associated superconformal symmetry deformations.Comment: 37 pages, 3 figures; title changed, version to appear in PR

Factors determining the persistence of campesino corn farming: The case municipality of Libres, Puebla

The most important economic activity in the municipality of Libres Puebla, in terms of harvested area and production value, is the corn production. This activity is characterized by plots of less than two hectares, low application of modern inputs and rain-fed production. Even though these production systems faced adverse technical, political and market conditions in the last two decades, the production of white corn is sustained by small scale campesino farming systems, combining sustainable traditional practices including a multicrop systems, conservation and use of landrace corn seed,family labor, and use of income from non-agricultural activities to finance agriculture. In most cases, production economic costs are higher than economic benefits, but including social benefits, such as food security objectives and campesino preferences; total benefits overcome economic production costs

Uso de recursos digitales por profesores de matemáticas en secundaria: un estudio exploratorio

Se presentan resultados de una investigación sobre uso de recursos digitales por profesores de matemáticas de secundaria mexicanos. Una muestra de 81 profesores de 24 escuelas secundarias fue seleccionada para responder un cuestionario y entrevistas para explorar las formas de uso y selección de los recursos, las interacciones que los profesores establecen con los recursos, además de factores institucionales y creencias que determinan su uso. Los resultados muestran una escasa formación y actualización de los profesores en el uso de recursos digitales, atribuible en parte a condiciones institucionales, pero también a creencias y actitudes de los profesores hacia la tecnología, se observó un bajo nivel de integración de los recursos digitales en el proceso de enseñanza, principalmente con actividades centradas en la transmisión de contenidos

Ovary transplantation method resulting in high reproductive performance in mice

There are mutant and transgenic mouse strains which lack the ability to breed, but where the females have functional ovaries. Ovary transplantation is an important tool for maintaining and producing crosses with these non-breeding strains.We have evaluated an ovary transplantation method by transplanting ovaries from females belonging to a non-reproduetive BALB/cByJ mutant mouse strain, All transplanted mice, 10 BALB/c.C57BL/6By, produced offspring and 94% of the progeny originated from the transplanted ovaries. The mean litter size and the mating period needed for productive mating to occur were similar to what is observed for corresponding control mice

Hacia la innovación en educación estadística

Este grupo temático busca dar continuidad a los esfuerzos por consolidar una comunidad de profesores e investigadores en educación estadística a nivel nacional a través de este espacio y que se viene haciendo desde hace varios años en las EIME. En esta ocasión, el grupo se propone discutir las posibilidades de hacer innovación a partir de los resultados de investigación, el uso de la tecnología y la experiencia en el aula. Con esa intención en nuestro grupo se aborda la importancia de las ideas fundamentales de estocásticos en el aula, el desarrollo del pensamiento inferencial estadístico, las nuevas oportunidades que ofrece el Geogebra como herramienta tecnológica a favor del razonamiento estadístico y una experiencia didáctica de su uso

Captación de agua de lluvia en la Mixteca Poblana de México

En la región Mixteca Poblana de México, se ubica una de las Microrregiones de Atención Prioritaria (MAP), del Colegio de Postgraduados en Ciencias Agrícolas (Colpos-México) Campus Puebla, y presenta serias restricciones para la producción agrícola y pecuaria, debido a la falta de agu

An effective serum- and xeno-free chemically defined freezing procedure for human embryonic and induced pluripotent stem cells

BACKGROUND Both human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) bear a great potential in regenerative medicine. In addition to optimized clinical grade culture conditions, efficient clinical grade cryopreservation methods for these cells are needed. Obtaining good survival after thawing has been problematic. METHODS We used a novel, chemically defined effective xeno-free cryopreservation system for cryostorage and banking of hESCs and iPSCs. The earlier established slow freezing protocols have, even after recent improvements, resulted in low viability and thawed cells had a high tendency to differentiate. The medium is a completely serum and animal substance free product containing dimethylsulfoxide, anhydrous dextrose and a polymer as cryoprotectants. The cells were directly frozen at −70°C, without a programmed freezer. RESULTS The number of frozen colonies versus the number of surviving colonies differed significantly for both HS293 (χ2 = 9.616 with one degree of freedom and two-tailed P = 0.0019) and HS306 (χ2 = 8.801 with one degree of freedom and two-tailed P = 0.0030). After thawing, the cells had a high viability (90-96%) without any impact on proliferation and differentiation, compared with the standard freezing procedure where viability was much lower (49%). The frozen-thawed hESCs and iPSCs had normal karyotype and maintained properties of pluripotent cells with corresponding morphological characteristics, and expressed pluripotency markers after 10 passages in culture. They formed teratomas containing tissue components of the three germ layers. CONCLUSION The defined freezing-thawing system described here offers an excellent simple option for banking of hESCs and iPSC