Introducción temprana de la noción de medida y del análisis sistémico y del reconocimiento de variables a través de la medida

La experiencia de innovación que se relata, consistió en el diseño de experiencias que permitan estudiar sistemas simples con respuesta lineal que puedan servir de modelo de sistemas más complejos relacionados con el interés de alumnos que ingresan a las carreras de Ingeniería; La formación de un grupo de trabajo conjunto con la participación de docentes de Introducción a la Ingeniería, Física I y Matemática B; y el diseño e implementación de trabajos de laboratorio sobre introducción al uso de instrumentos de medida para su realización en Introducción a la Ingeniería.Facultad de Ingenierí

Conformational studies of substituted nitroanilines : Geometry of 2-methyl-5-nitroaniline

The title compound (C7H8N2O2), is monoclinic, space group P21/n, witha=9.552(2),b=5.677(2),c=13.586(3)A, β=92.68(2)0, andDx=1.374 g-cm−3 forZ=4. The refinement converged toR=0.043,wR=0.038. The molecule is approximately planar, with dihedral angles of 3.7(2.1)0 between the amino group and the aromatic ring, and 3.2(2)0 between the nitro group and the ring. According to the UV spectrum in solution, the molecular geometry indicates weak intramolecular charge transfer. The three-dimensional structure is stabilized by three intermolecular H bonds. A bifurcated one induces the formation of chains along$[10\bar 1]$, while the other two link molecules that belong to adjacent chains and are related by an inversion center.Facultad de Ciencias Exacta

La innovación como proceso: aplicación a la enseñanza de temas introductórios de Termodinámica

El presente trabajo muestra algunos resultados de un primer análisis de las actividades incluidas en una propuesta innovadora sobre temas de Termodinámica. Esta propuesta contempló aspectos conceptuales y metodológicos de temas básicos comprendidos en un curso introductorio. La propuesta incluyó modificaciones no sólo en la presentación de los conceptos sino también en la actividad desarrollada en clase por los alumnos y en la ejercitación posterior. Estuvo enmarcada en un proceso que involucró a dos cátedras de distintos niveles de una misma Facultad y se caracterizó por una realimentación entre la implementación de los cambios y la evaluación del aprendizaje logrado. El análisis de una evaluación sistemática de la incorporación de conceptos, tale como energía, trabajo y calor, mostró, junto a una mejor incorporación y persistencia en el tiempo de los conceptos indagados, la necesidad de un cuidadoso diseño de los instrumentos de evaluación.Some of the results obtained through the analysis of activities included in an innovative proposal on the teaching of thermodynamics at an introductory level are shown. This proposal dealt with conceptual and methodological aspects about basic concepts and included changes in the way these concepts were introduced and in-classroom student activities. The innovative process, involving two courses of different level which belong to the same School, was characterized by a constant feedback between implementation of changes and evaluation of student achievement. The systematic assessment done through testing of concepts such as energy, work and heat has shown not only a better incorporation and permanence of the inquired concepts but also suggests the need of careful survey design.Fil: Bordogna, C.. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Fisicomatemática; ArgentinaFil: Cotignola, M. I.. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Fisicomatemática; ArgentinaFil: Punte, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Capannini, O. M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentin

Difficulties in Learning Thermodynamic Concepts : Are They Linked to the Historical Development of this Field?

Students' misunderstanding of basic thermodynamic concepts is analysed on historical grounds. The persistence of some ideas from the caloric model are found to be reinforced by magnitude names and unit definitions that were brought up at the early stages of thermodynamic development. The failure of many popular textbooks to make a clear distinction between internal energy and heat is also explored and related to Students' learning difficulties. Some hints that may help to improve Students' understanding are presented.Investigación en Metodologías Alternativas para la Enseñanza de las Ciencia

Non-Bonded Intermolecular Interactions and Crystal Stability of trans -1,4-Cyclohexanedicarboxylic Acid, 1,4-dibromo

Molecular geometry, crystal packing and thermal stability of trans-1,4-cyclohexanedicarboxylic acid, 1,4-dibromo (I) are examined, in order to analyse the relative influence of the different intermolecular interactions at play. From a comparison with the corresponding properties of trans1,4-cyclohexanedicarboxylic acid (II), some insights on the results of the competition between Br and carboxylic groups are obtained. In the crystalline state, the molecules of both compounds present chair centrosymmetric geometry and build infinite chains through ring hydrogen bonds involving the carboxylic groups. These groups are axial in I and equatorial in II, giving rise to different assembly of the chains. In both compounds there is in general good agreement between the in-crystal geometry and the B3LYP/LanL2DZ optimized geometry of the corresponding isolated molecule. The only significant differences are related to the carboxylic groups. The intermolecular contacts in I have been rationalized on the basis of a graph set analysis. A molecular dynamics based method has been used to analyse the temperature dependence of the mean life time of the different kinds of hydrogen bonds characterized in I. It has been found that the O–H⋅ ⋅O and C–H⋅ ⋅O(carbonyl) interactions are the main source of thermal stability. The melting point of I determined within this approach agrees very well with the experimental value.Instituto de Física La PlataFacultad de Ingenierí

3-ethoxycarbonyl-4-hydroxy-6-(methoxy-methoxy)-1-methyl-2-quinolone

In the title compound, C15H17NO6, the formation of an intramolecular O-H⋯O resonance-assisted hydrogen bond extends the delocalization of the electronic system beyond the two quinoline fused rings.Facultad de Ciencias Exacta

The influence of Ni(II) on brushite structure stabilization

Brushite samples doped with Ni(II) in different concentrations, from 5% to 20%, were prepared in aqueous solution at pH = 7 and at two temperatures: 25 and 37 °C. The solid samples were characterized by chemical analysis, infrared spectroscopy (FTIR) and x-ray powder diffraction (XRPD). Chemical analysis has shown Ni(II) almost complete incorporation to the solid phase up to 15%. X-ray diffraction patterns have allowed to identify brushite phase with almost no modification of the line breadth and only small shifts of lines positions with increasing Ni(II) incorporation up to 15%. For larger Ni(II) concentration, in solution, a mixture of phases has been detected. Infrared spectra have supported diffraction results. For Ni(II) 20% and over the characteristic bands of HPO2-4 anions tend to vanish, and the typical shaped PO3=4 bands are observed. These results have allowed to establish that the presence of low levels of Ni in the synthetic process not only helps brushite formation; but, also prevents brushite from apatite conversion and, in addition, preserves brushite crystallinity. According to these findings, it is possible to propose that nickel traces present in the urinary system might be a trigger to brushite stone formation and/or growth, rather than the expected brushite conversion to hydroxyapatite. This outcome would explain the recurrent detection of difficult to treat brushite stones, observed in the last three decades.Centro de Química InorgánicaInstituto de Física La Plat

The influence of Ni(II) on brushite structure stabilization

Brushite samples doped with Ni(II) in different concentrations, from 5% to 20%, were prepared in aqueous solution at pH = 7 and at two temperatures: 25 and 37 °C. The solid samples were characterized by chemical analysis, infrared spectroscopy (FTIR) and x-ray powder diffraction (XRPD). Chemical analysis has shown Ni(II) almost complete incorporation to the solid phase up to 15%. X-ray diffraction patterns have allowed to identify brushite phase with almost no modification of the line breadth and only small shifts of lines positions with increasing Ni(II) incorporation up to 15%. For larger Ni(II) concentration, in solution, a mixture of phases has been detected. Infrared spectra have supported diffraction results. For Ni(II) 20% and over the characteristic bands of HPO2-4 anions tend to vanish, and the typical shaped PO3=4 bands are observed. These results have allowed to establish that the presence of low levels of Ni in the synthetic process not only helps brushite formation; but, also prevents brushite from apatite conversion and, in addition, preserves brushite crystallinity. According to these findings, it is possible to propose that nickel traces present in the urinary system might be a trigger to brushite stone formation and/or growth, rather than the expected brushite conversion to hydroxyapatite. This outcome would explain the recurrent detection of difficult to treat brushite stones, observed in the last three decades.Centro de Química InorgánicaInstituto de Física La Plat

Role of weak C—H…O and strong N—H…O inter­molecular inter­actions on the high-symmetry mol­ecular packing of trans-cyclo­hexane-1,4-dicarboxamide

An unpredicted fourfold screw N—H.O hydrogen bond C(4) motif in a primary dicarboxamide (trans-cyclo­hexane-1,4-dicarboxamide, C8H14N2O2) was investigated by single-crystal X-ray diffraction and IR and Raman spectroscopies. Electron-density topology and inter­molecular energy analyses determined from ab initio calculations were employed to examine the influence of weak C—H.O hydrogen-bond inter­actions on the peculiar arrangement of mol­ecules in the tetra­gonal P43212 space group. In addition, the way in which the co-operative effects of those weak bonds might modify their relative influence on mol­ecular packing was estimated from cluster calculations. Based on the results, a structural model is proposed which helps to rationalize the unusual fourfold screw mol­ecular arrangement.Fil: Garcia Reyes, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Fantoni, Adolfo Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Barón, Máximo. Universidad de Belgrano. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Romano, Rosana Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; ArgentinaFil: Punte, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin

Role of weak C—H…O and strong N—H…O inter­molecular inter­actions on the high-symmetry mol­ecular packing of trans-cyclo­hexane-1,4-dicarboxamide

An unpredicted fourfold screw N—H.O hydrogen bond C(4) motif in a primary dicarboxamide (trans-cyclo­hexane-1,4-dicarboxamide, C8H14N2O2) was investigated by single-crystal X-ray diffraction and IR and Raman spectroscopies. Electron-density topology and inter­molecular energy analyses determined from ab initio calculations were employed to examine the influence of weak C—H.O hydrogen-bond inter­actions on the peculiar arrangement of mol­ecules in the tetra­gonal P43212 space group. In addition, the way in which the co-operative effects of those weak bonds might modify their relative influence on mol­ecular packing was estimated from cluster calculations. Based on the results, a structural model is proposed which helps to rationalize the unusual fourfold screw mol­ecular arrangement.Instituto de Física La PlataCentro de Química InorgánicaFacultad de Ingenierí