Large B-Fields and Noncommutative Solitons

The purpose of this talk is to review a few issues concerning noncommutativity arising from String Theory. In particular, it is shown how in Type IIB Theory, the annihilation of a D3-\bar{D3} brane pair yields a D1-string. This object, in the presence of a large B-field and fermions, happens to be a complex noncommutative soliton endowed with superconductivity.Comment: 5 pages, latex, no figures, talk delivered at the `VIII Workshop on Particles and Fields', Zacatecas, Mexico; November 200

Strict calculation of the light statistics at the output of a travelling wave optical amplifier

A new method for calculating the probability density function of the photon number propagating through a travelling wave optical amplifier with no restriction on its working regime (linear and nonlinear) is reported. The authors show that the widely used Gaussian approximation of the probability density function does not match the real statistics if the incident optical power is small.Peer ReviewedPostprint (published version

Practical method for modelling the nonlinear behaviour of a travelling wave semiconductor optical amplifier

The authors present a simple model of a travelling wave semiconductor optical amplifier with an appreciable degree of saturation. The model uses a particular way of linearising the total carrier recombination R(N) to find useful expressions for the saturation parameter and/or the carrier lifetime. By combining these expressions and the gain measurements realised, it is possible to establish the dependence between the mentioned parameters and the input optical power.Peer ReviewedPostprint (published version

Compensatory education for disadvantaged Mexican students : an impact evaluation using propensity score matching

The authors use propensity score matching to evaluate the effectiveness of CONAFE, a compensatory education program in Mexico, in improving student test scores and lowering repetition and failure rates. They find that CONAFE is most effective in improving primary school math learning and secondary school Spanish learning. Secondary education delivered by way of television to remote communities and bilingual education for indigenous students are both shown to improve student achievement. CONAFE also lowers primary school repetition and failure rates. The authors conclude that this compensatory education program can effectively improve short-term learning results for disadvantaged students, but that improvement varies by the subject of instruction and the demographics of students taught.Primary Education,Gender and Education,Health Monitoring&Evaluation,Teaching and Learning,Public Health Promotion,Teaching and Learning,Gender and Education,Primary Education,Health Monitoring&Evaluation,Girls Education

Analysis of competitiveness in Colombian family businesses

Purpose: Building on the resource-based view and the configuration theory, the purpose of this study uses a systemic and multidimensional competitiveness index (CI) i.e. that incorporates system constraints among the 10 competitive pillars that form the index to assess the competitiveness level and the connection between competitiveness and economic performance [return on assets (ROA)] in family businesses (FBs). Design/methodology/approach: For the empirical application, the use a unique primary data set drawn from the global competitiveness project (www.gcp.org) that includes information for 77 Colombian FBs for 2017. Cluster analysis is used to evaluate the potential relationship between competitiveness, the configuration of competitive pillars and economic performance (ROA). Findings: The results for the CI show that the main competitive strengths of the analysed firms are related to the introduction of product innovations and networks (suppliers and customers), while the limited use of technologies in their operations and the low online presence are the main competitive weaknesses of these firms. Additionally, the findings of the cluster analysis reveal that different configurations of competitiveness pillars are associated with different performance levels. Therefore, the results contribute to identifying how specific strategies aimed at improving different resources or capabilities contribute to enhance business competitiveness, and ultimately, performance. Originality/value: By using an index number that takes into account the multiple interactions between resources and capabilities, the proposed analysis not only sheds light on the drivers of competitiveness i.e. resources and capabilities, and its connection to performance but also contributes to understanding the boundaries of the businesses’ competitiveness system, as well as the strategies that can potentially enhance competitiveness, and subsequently, business performance.Peer ReviewedPreprin

Strategies for monitoring the hydrogen production in a PEM electrolyser

The growing interest in the use of hydrogen as an energy resource has led to the search for new ways to produce it. In order to alleviate and mitigate the greenhouse gases emissions caused by the use of fossil fuels, one of the methods of hydrogen production is through PEM electrolysers. Using electricity, which can come from renewable energy sources, water can be dissociated generating oxygen and hydrogen. However, this hydrogen produc- tion method still does not present competitive costs with respect to other methods that do generate greenhouse gases, such as natural gas reforming. Within the scope of opening a new research line about electrolysers, this project lays the foundations for research from a thermodynamic point of view, which will continue in the future with more works. The PEM electrolyser used in this project corresponds to an academic demonstration experiment that has a single cell. The first variables necessary to monitor are the voltage and current applied to the electrolyser, to later monitor the operating temperature of the electrolyser and the hydrogen production. During the experimental stage carried out in the laboratory, an Arduino microcontroller has been used to collect data digitally, since it allows a high sampling rate, except for the production of hydrogen, which has been carried out analogically. Finally, the current and voltage have been measured thanks to the INA219 module and the temperature through thermocouples and MAX31855 modules. To establish and maintain the operating temperature of the electrolyser constant, an external hydraulic circuit has been made, manu- facturing a heat exchanger through which the heated water with impurities from a water bath circulates, heating the distilled water which with the electrolyser is fed. One of the long-term objectives of the open research line is the thermodynamic monitoring of the reaction, trying to measure the temperature values inside the electrolyser and not only in the inlet or outlet tubes. This would allow studying the influence of the geometry of the water channels on the operation of the electrolyser. As the laboratory has a thermal imaging camera and the electrolyser used has a methacrylate casing, a test has been carried out but it has been possible to verify that the methacrylate used by the manufacturer is not transparent to the infrared radiation detected by the camera, being impossible to accurately measure the evolution of the temperature caused by the electrochemical reaction. Finally, the polarization curves of the electrolyser at different operating temperatures have been obtained, being able to verify that the higher the inlet water temperature, the higher the voltage applied to the electrolyser is at the same current density. This difference is more accused when the current density is higher. A correlation has also been found between the polarization voltage of the electrolyser during its startup depending on the current rate applied, and moreover, once the electrolyser is turned off, it remains polarized for about 7 hours. However, the hydrogen monitoring method used has not been adequate since the Faraday efficiency obtained does not have a logical valueEn los últimos años el creciente interés en el uso de hidrógeno como recurso energético ha propiciado la búsqueda de nuevas formas para su producción. Con el fin de paliar y mitigar la emisión de gases de efecto invernadero por el uso de combustibles fósiles, uno de los métodos de producción de hidrógeno es mediante electrolizadores PEM. Usando electricidad, pudiendo provenir de fuentes de energía renovables, se puede disociar agua generando oxígeno e hidrógeno. Sin embargo, este método de producción de hidrógeno aún no presenta unos costes competitivos con respecto a otros métodos que si generan gases de efecto invernadero como puede ser el reformado de gas natural. En el ámbito de la apertura de una nueva línea de investigación en los electrolizadores, este proyecto senta las bases para la investigación desde un punto termodinámico de los electrolizadores, que continuará con más trabajos futuros. El electrolizador PEM utilizado en este proyecto corresponde a un experimento de demostración académica que dispone de una única celda. Las primeras variables necesarias a monitorizar corresponden con el voltaje y la corriente aplicadas al electrolizador, para más tarde monitorizar la temperatura de operación del electrolizador y la producción de hidrógeno. Durante la fase experimental realizada en el laboratorio se ha utilizado un microcontrolador arduino para la toma de datos de forma digital ya que esto permite tener una tasa de muestreo elevada, a excepción de la producción de hidrógeno que se ha realizado de forma analógica. Finalmente, la corriente y el voltaje han sido medidos gracias al módulo INA219 y la temperatura mediante termopares y módulos MAX31855. Para establecer y mantener constante la temperatura de operación del electrolizador, se ha realizado un circuito hidráulico externo, fabricando un intercambiador de calor por el que circula el agua con impurezas del baño térmico y que calienta el agua destilada de entrada al electrolizador. Uno de los objetivos a largo plazo de la línea de investigación abierta es la monitorización termodinámica de la reacción, tratando de medir los valores de temperatura dentro del electrolizador y no sólo en los tubos de entrada o salida. Esto permitiría estudiar la influencia de la geometría de los canales de agua en la operación del electrolizador. Como en el laboratorio se dispone de una cámara térmica y el electrolizador utilizado dispone de un carcasa de metacrilato, se ha realizado una prueba pero se ha podido comprobar que el metacrilato utilizado por el fabricante no es transparente a la radiación infrarroja que detecta la cámara, siendo imposible medir de forma precisa la evolución de la temperatura causada por la reacción electroquímica. Finalmente se han obtenido las curvas de polarización del electrolizador a diferentes temperaturas de operación, pudiendo comprobar que a mayor temperatura del agua de entrada, el voltaje aplicado al electrolizador a una misma densidad de corriente es superior. Siendo esta diferencia más notable cuando la densidad de corriente es mayor. También se ha encontrado correlación entre el voltaje de polarización del electrolizador durante su arranque en función de la velocidad con que se aplica la corriente, y que una vez se apaga el electrolizador, este permanece polarizado durante unas 7 horas. Sin embargo, el método de monitorización de hidrógeno utilizado no ha sido el correcto ya que la eficiencia de Faraday obtenida no tiene un resultado lógicoEn els últims anys el creixent interès en l’ús d’hidrogen com a recurs energètic ha propiciat la cerca de noves formes per a la seva producció. Amb la finalitat de pal·liar i mitigar l’emissió de gasos d’efecte d’hivernacle per l’ús de combustibles fòssils, un dels mètodes de producció d’hidrogen és mitjançant electrolizadores PEM. Usant electricitat, podent provenir de fonts d’energia renovables, es pot dissociar aigua generant oxigen i hidrogen. No obstant això, aquest mètode de producció d’hidrogen encara no presenta uns costos competitius respecte a altres mètodes que si generen gasos d’efecte d’hivernacle com pot ser el reformat de gas natural. En l’àmbit de l’obertura d’una nova línia de recerca en els electrolizadores, aquest projecte senta les bases per a la recerca des d’un punt termodinàmic dels electrolizadores, que continuarà amb més treballs futurs. El electrolizador PEM utilitzat en aquest projecte correspon a un experiment de demostració acadèmica que disposa d’una única cel·la. Les primeres variables necessàries a monitorar corresponen amb el voltatge i el corrent aplicades al electrolizador, per a més tard monitorar la temperatura d’operació del electrolizador i la producció d’hidrogen. Durant la fase experimental realitzada en el laboratori s’ha utilitzat un microcontrolador arduino per a la presa de dades de manera digital ja que això permet tenir una taxa de mostreig elevada, a excepció de la producció d’hidrogen que s’ha realitzat de manera analògica. Finalment, el corrent i el voltatge han estat mesurats gràcies al mòdul INA219 i la temperatura mitjançant termoparells i mòduls MAX31855. Per a establir i mantenir constant la temperatura d’operació del electrolizador, s’ha realitzat un circuit hidràulic extern, fabricant un bescanviador de calor pel qual circula l’aigua amb impureses del bany tèrmic i que escalfa l’aigua destil·lada d’entrada al electrolizador. Un dels objectius a llarg termini de la línia de recerca oberta és el monitoratge termodinàmic de la reacció, tractant de mesurar els valors de temperatura dins del electrolizador i no sols en els tubs d’entrada o sortida. Això permetria estudiar la influència de la geometria dels canals d’aigua en l’operació del electrolizador. Com en el laboratori es disposa d’una cambra tèrmica i el electrolizador utilitzat disposa d’un carcassa de metacrilat, s’ha realitzat una prova però s’ha pogut comprovar que el metacrilat utilitzat pel fabricant no és transparent a la radiació infraroja que detecta la càmera, sent impossible mesurar de manera precisa l’evolució de la temperatura causada per la reacció electroquímica. Finalment s’han obtingut les corbes de polarització del electrolizador a diferents temperatures d’operació, podent comprovar que a major temperatura de l’aigua d’entrada, el voltatge aplicat al electrolizador a una mateixa densitat de corrent és superior. Sent aquesta diferència més notable quan la densitat de corrent és major. També s’ha trobat cor- relació entre el voltatge de polarització del electrolizador durant la seva arrencada en funció de la velocitat amb què s’aplica el corrent, i que una vegada s’apaga el electrolizador, aquest roman polaritzat durant unes 7 hores. No obstant això, el mètode de monitoratge d’hidrogen utilitzat no ha estat el correcte ja que l’eficiència de Faraday obtinguda no té un resultat lògi

S.T.E.A.M. Career Night

Partnering with the Multi-Ethnic Engineering and Science Association (MESA) tutoring service in the College of Engineering, 20 local underrepresented youth and their parents had the opportunity to interact with science professionals. The kids participated in demonstrations of sorts by various panelist members and groups which include science writers, outreach and education researchers, and professors at the University of Iowa. The presenters went through explaining their career paths and what their jobs entail. They then had the opportunity during a Q&A session to ask more about the career paths and jobs of their demonstrators. The children were provided free dinner courtesy of MESA and at the end of the two-night program gifts were given thanks to donations from the Latham family, UICCU, and BLICK art materials. From this event, I hoped to encourage students from a broad spectrum of interest, to see that science isn\u27t for the elite, or for people of certain groups, but that it is full of opportunities and when you have a passion, you can make a job from it