Aunque no tan explotados educacionalmente hoy en día como debiera ser, los juguetes resultan recursos muy útiles en cursos de ciencias e ingenierías. Un juguete ampliamente conocido, el Slinky®, es utilizado en el presente artículo para explicar de manera sencilla importantes principios físicos y mostrar como ellos han sido aplicados en desarrollos científicos y tecnológicos

Though not so much nowadays educationally exploited as it should be, toys are very useful resources in courses in science and engineering. A widely known toy, the Slinky®, is used through this article to explain in a simple way important physical principles and to show how they have been applied for scientific and technological developments

Los procesos de enseñanza en ingeniería han venido evolucionando desde la llamada clase magistral, con un formato casi que inflexible y que en buena proporción aun hoy en día presentan los conceptos y principios de manera abstracta y sin relación con la realidad que el estudiante conoce, a un esquema más pedagógico que permite una mayor conexión con el entorno. Un muy bien conocido y representativo juguete se usa en este artículo para mostrar como ejemplos relacionados de la vida real que rodean la vida de los estudiantes pueden usarse para complementar los conceptos teóricos, en este caso físicos, y desarrollos matemáticos que rodean un tema específico, contribuyendo así positivamente a la motivación para el estudio y análisis de sistemas más complejos

Learning processes in engineering had been evolving from the so-called master class, with an almost inflexible format and that presented, still nowadays in great proportion, concepts and principles in an abstract way and without relation to the reality the student knows, to a more pedagogical scheme which allows greatest connection with the environment. One well-known and representative toy is used in this article to show how real-life related examples surrounding the students' world can be used in order to complement theoretical concepts, in this case physical, and mathematical developments around a specific subject, positively contributing so to the motivation for the studying and analysis of more complex systems

A very little known aspect of the scientific career of Regnault is his contribution to the emerging organic chemistry in the first half of the nineteenth century. The purpose of this article is not only to describe two of his most important researches in this field, as were the discovery of two series of halogenated derivates of certain organic compounds and the precise identification of some of the then recently discovered alkaloids, but also the main features that identified his research method. With the involvement in these subjects, Regnault unintentionally positioned himself in the midst of some of the polemics about the classification of organic compounds that characterized this age of science.

Duas diferentes linhas de pesquisa deram significativa contribuicao à descoberta da supercondutividade: a liquefação de gases e os estudos da dependência da condutividade ou resistencia elétrica com a temperatura, em metais puros ou ligas. Diferentes artigos descrevem e discutem as conquistas da liquefação ao passo que a segunda não recebeu, contudo, a mesma atenção. Este artigo busca preencher esta lacuna, apresentando um histórico detalhado da evolução de idéias, das primeiros resultados experimentais e dos pesquisadores nelas envolvidos.

Two different lines of research had significant contributions to the discovery of superconductivity: the liquefaction of gases and the studies of the temperature dependence of the electrical conductivity, or resistance, of pure metals and alloys. Different publications have described and discussed the achievements in the first one of these subjects. The second subject had not received, however, the same attention. This article tries to fill this gap by presenting an account showing details of the evolution of the ideas, the first essentially experimental contributions to the subject and their corresponding responsible persons.

A liquefação do hélio e a descoberta da supercondutividade são dois das mais surpreendentes desenvolvimentos da física de baixas temperaturas. O fato que ambas ocorreram no laboratório de Kammerlingh Onnes em Leiden, na Holanda, não é mera coincidência: o primeiro foi indispensável para que os pesquisadores pudessem chegar à segunda. Do mesmo modo, a liquefação do hélio culminou após décadas de esforços em liquefazer os chamados "gases permanentes". Um estudo mais completo deste assunto requer a discussão de estudos que se estenderam por mais de 50 anos, ligando pesquisadores de diferentes países europeus.

Liquefaction of helium and the discovery of superconductivity are two of the most striking developments in low temperature physics. The fact that both were carried out in the laboratories of Kamerlingh Onnes at Leiden is not mere coincidence; the first one was indispensable for the researches that led to the second one. On the same way, liquefaction of helium was the consequence of several decades of efforts addressed to the process for liquefy the so-called then 'permanent gases'. A whole study of this remarked subject must then include developments that extended, in his decisive step, more than a half of a century and that connect researches of many scientists throughout several European countries.

La incorporación de ayudas filtrantes o coadyuvantes en los procesos de filtración ha incrementado la eficiencia de remoción de las impurezas suspendidas en los licores resultantes de las etapas de evaporación y cristalización en el proceso de obtención de azúcar refinada. La reducción de su vida útil a un solo ciclo de utilización implica, sin embargo, evidentes inconvenientes para su aplicación industrial. El objetivo principal de este estudio fue la identificación y validación del uso de un hidrociclón como una alternativa técnica y económicamente factible para la recuperación parcial de estos materiales. La investigación se basó en las características físicas de los componentes del deshecho resultante del proceso de filtración (ayudas filtrantes, carbón activado, sacarosa, agua e impurezas), y la cantidad de sólidos suspendidos en la corriente.

The incorporation of filter aids in the filtration processes has increased the removal's efficiency of suspended impurities in the liquors resulting from the evaporation and crystallization steps in the refining sugar process. Nevertheless, the reduction in its lifetime to only one utilization cycle implies obvious disadvantages for its industrial application. The main objective of this work was the identification and validation of the use of a hydrocyclone as a technical and economical feasible alternative for partial recovering of these materials. The research based on the physical characteristics of the waste components (filter aids, activated carbon, saccharose, water and other impurities) and the amount of suspended solids in the flow.

Eugène Bourdon is the almost unknown inventor of one of the instruments most known by engineers around the World. From its introduction around the middle of XIX century, the Bourdon manometer or tube has been the most employed instrument for measuring pressure at laboratory and industrial scales. Its appearance in the European market, following by that in America, became a starting point for the gradual but firm replacement of the by then very usual mercury manometer through an element that worked based on a different physical principle. Its invention, oblivious to all the by then usual priority polemics around scientific and technological events, subsequently allowed developments in instrumentation and process-control related subjects.

Eugène Bourdon es el casi desconocido inventor de uno de los instrumentos más conocidos por ingenieros en todo el mundo. El manómetro, o tubo de Bourdon, ha sido el equipo más utilizado para la medición de presión a escalas de laboratorio e industrial desde su introducción a mediados del siglo XIX. Su aparición en el mercado europeo, y casi inmediatamente después en el americano, se constituyó en el punto de partida para el paulatino pero firme reemplazo del por ese entonces muy común manómetro de mercurio por un elemento que respondía a la aplicación de un principio físico diferente. Su invención, para nada ajena a las usuales polémicas de prioridad de la época surgidas alrededor de importantes eventos científicos y tecnológicos, permitió subsecuentemente desarrollos en áreas relacionadas de instrumentación y control de procesos.

The formulation of the so-called law of rectilinear diameter for the determination of the critical volume of substances in the concluding decades of the nineteenth century became in a very useful and acceptably exact alternative tool for researchers in the field of critical phenomena. Its corresponding original expression, and even those of its early few modifications, were so mathematically simple that their use did not limit to exclusively contribute to remove the by then experimental obstacle for the estimating of this critical parameter, but also extended along several decades in the increasing applications of the principle of corresponding states.

Cryoscopy is considered one of the foundations of the modern theory of solutions and of physical chemistry. This paper shows in order the first regularities pointed out by several scientists on the subject, in the first chapter of its birth as a scientific discipline. The study is focused on the identification of the different steps that helped, first qualitatively and then quantitatively, to adjust the different classes of possible solutions, including those that formed hydrates, to a basic formulation that the French scientist François-Marie Raoult would later generalize in the law that bears his name.

Many students and professionals in chemistry and chemical engineering related the name Kwong with one of the most remarkable equations of state with two parameters. In the same way, very few people know who Kowng was. This article shows some of the unknown personal and professional facts of Joseph Neng Shun Kwong, a person who devoted almost four decades of his life to the industrial research in the adhesives industry.

The name of Otto Redlich is generally remembered as co-author of one of most used equations of state for the calculation of volumetric and thermodynamic properties of pure substances and their mixtures. Nevertheless, he made also important contributions in different areas of chemistry and chemical engineering. Pursuits of race and religious order forced him and his family to leave his native Austria and emigrate to the United States. His professional career included both academic and industrial research achievements.