Detection of magnetic moment in thin films with a home-made vibrating sample magnetometer

This paper explores the optimization of an array of pick-up coils in a home-made vibrating sample magnetometer for the detection of magnetic moment in thin films. Sensitivity function of a 4-coils Mallinson configuration was numerically studied for the determination of the physical dimensions that enhance the sensitivity of the magnetometer. By performing numerical simulations using the Biot-Savart law combined with the principle of reciprocity we were able to determine the maximum values of sensitivity and the influence of the separation of the coils on the sensitivity function. After the optimization of the pick-up coils, the vibrating sample magnetometer was able to detect the magnetic moment of a 100 nm-thickness Fe19Ni81 magnetic thin film along and perpendicular to the in-plane anisotropy easy axis. The implemented vibrating sample magnetometer is able to detect changes in the magnetic moment of ∼2 × 10-4 emu.Fil: Jordán, D.. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: González Chávez, D.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Laura, D.. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: Leon Hilario, Ludwin Misael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: Monteblanco, E.. Universite de Lorraine; FranciaFil: Gutarra Espinoza, Abel. Universidad Nacional de Ingeniería. Facultad de Ciencias; PerúFil: Aviles Felix, Luis Steven. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Cellulose Microfibres Obtained from Agro-Industrial Tara Waste for Dye Adsorption in Water

Microfibres of cellulose were extracted from tara residues (TR), obtained after the production process, and used to remove dyes in aqueous solution. Caesalpinia spinosa (Molina) Kuntze or Tara spinosa, commonly known as tara, is a thorny shrub native to Peru. For these purposes, tara residues (TR) from the production process are used to extract cellulose microfibres (CMF). First, TR are treated in basic mediums; then, they are transferred to an acidic medium. Finally, they are ground in a cutting mill for a short period of time. Scanning electron microscopy was used to characterize CMF. Fibre sizes of approximately 10 µm in length and 300–500 nm in diameter were observed. The crystallinity index calculated from X-ray patterns was defined at 77%. Infrared spectroscopy showed that treating TR with chemical products produces TR delignification. The dye adsorption tests (basic yellow, basic blue 41, basic blue 9 and basic green 4) in water demonstrated that isotherms adjust to the Langmuir model, with maximum respective adsorption values of 43.6, 45.5, 75.0 and 112.2 mg.g-1 for each dye

Identification of rare-earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains significant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identification of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Five (5) samples extracted from different locations at the Capacsaya site were characterized and identified K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO4. Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efficient separation of the K-feldspar phase in the particle size range 75–150 μ m.Fil: Ochoa, J.. Universidad Nacional de Ingeniería; PerúFil: Monteblanco, E.. Commissariat A L Energie Atomique Et Aux Energies Alternatives.; FranciaFil: Cerpa, L.. Instituto Geológico Minero y Metalúrgico; PerúFil: Gutarra Espinoza, Abel. Universidad Nacional de Ingenieria; PerúFil: Aviles Felix, Luis Steven. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentin

Propriétés structurelles et électroniques du graphène sur SiC(0001) étudiées par microscopie combinée STM/AFM

Le graphène, un feuillet élémentaire de graphite, est un matériau très étudié par la communauté scientifique car ses propriétés physiques sont nouvelles et uniques. Il apparaît comme un matériau très prometteur pour des applications technologiques. Nous présentons une étude des propriétés structurelles et électroniques du graphène épitaxial sur 6H-SiC(0001) au moyen d un microscope STM/AFM combiné basé sur un diapason en quartz avec une pointe conductrice en Pt/Ir ou en fibre de carbone. Les pointes fabriquées par attaque électrochimique présentent un rayon d apex de quelques nanomètres et ont été caractérisées par SEM, TEM et émission électronique par effet de champ. On s est d abord focalisé sur les propriétés d un échantillon qui présente des terrasses partiellement recouvertes de graphène. Dans ce cas, l image STM ne donne pas la topographie de la surface. Celle-ci est donnée par l AFM en mode répulsif. Les différentes propriétés électroniques de chaque terrasse sont confirmées par des mesures spectroscopiques I=f(V). Puis, l étude à haute résolution par FM-AFM sur une terrasse lisse a révélé la structure ondulée et périodique de la reconstruction 6 3x6 3R30 du SiC(0001) recouverte de graphène. Nous montrons que les maxima des nappes d iso-densité locale d états électroniques au niveau de Fermi observés dans l image STM ne se superposent pas avec les zones associées aux maxima des nappes d iso-densité d états totaux (Topographie AFM). Ils apparaissent décalés de ~1 nm le long de la direction [11] de la quasi-maille 6x6 de la reconstruction 6 3x6 3R30. Comme l amplitude mesurée des ondulations de la surface augmente avec le gradient de force appliqué, on montre que la surface du graphène est déformée par la pointe AFM. Cette déformation qui modifie le couplage électronique entre le graphène et la couche tampon influence fortement le contraste des images STM/AFM. Les conséquences de cette déformation sur les images STM résolvant le réseau du graphène sont aussi discutées.The graphene, a basic sheet of graphite, is a new material intensively studied by the scientific community because of its new and unique physical properties. Furthermore it appears as a very promising material for technological applications. We present a study of structural and electronic properties of epitaxial graphene on 6H-SiC(0001) using a combined STM/AFM microscope based on a quartz tuning fork with a conductive tip. The tips made from electrochemical etched Pt/Ir wire or carbon fiber have an apex radius of few nanometers and were characterized by SEM, TEM and by field electron emission. First, we focused on the properties of a sample showing terraces partially covered with graphene. In this case, the STM images do not provide the real surface topography, which is given by the AFM topography working in repulsive mode. The electronic properties of each terrace are confirmed by local spectroscopic I=f(V) measurements. Then, the high-resolution FM-AFM study on a smooth terrace revealed the corrugated structure due to the periodic 6 3x6 3R30 reconstruction of SiC (0001) covered with graphene. We show that the maxima of the local density of electronic states at the Fermi level observed in STM image do not overlap with the zones associated with maxima of total states density (AFM Topography). They appear shifted by ~1 nm along the direction [11] of the 6x6 nanomesh of the 6 3x6 3R30 reconstruction. As the corrugation amplitude of the surface increases with the applied force gradient, we show that the surface of graphene is distorted by the AFM tip. This deformation modifies the electronic coupling between the graphene and the buffer layer and strongly influences the contrast in STM/AFM images. The consequences of this deformation are also discussed in the STM images showing the lattice of graphene.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Identification of rare earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains signifcant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identifcation of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray difraction analyses. Five (5) samples extracted from diferent locations at the Capacsaya site were characterized and identifed K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO4. Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efcient separation of the K-feldspar phase in the particle size range 75–150 μm

Análisis y diagnóstico térmico en viviendas altoandinas del Perú

El objeto de la investigación que genera este trabajo es diagnosticar la situación térmica actual de cada una de dos viviendas alto andinas del Perú, identificar flujos de calor producidos en ellas y proyectar el mejoramiento térmico correspondiente. Se ha seguido una metodología experimental y analítica apoyada con simulaciones aplicadas a partes específicas de la vivienda. La base de datos experimentales la constituye mediciones y registros automáticos hechos durante 40 a 50 días continuos a partir del 11 de junio de 2008, cuyo procesamiento permite afirmar que las condiciones del ambiente interior de ambas viviendas es severamente frío la mayor parte del día, en el mejor de los casos, se registra 15°C al medio día y -5°C en horas de la madrugada. En aparente contradicción se obtienen potenciales de energía solar ganable por cada vivienda, que podrían ser suficientes para conseguir en ellas las condiciones de confort requeridas, mas paralelamente, se comprueba la existencia de filtraciones de aire elevadas que juegan un papel contrario. En suma, la percepción concluyente es que ambas viviendas requieren de mayor protección contra el enfriamiento que agregados diversos que incrementen su calentamiento.The purpose of the research that stems from this work is to diagnose the current thermal situation of each and every dwelling in the highlands of Peru, to identify heat flows produced inside them and to forecast their thermal improvement. An experimental and analytical methodology has been used, supported by simulations applied to specific parts of the house. The experimental database is constituted by automatic measurements and records taken during 40 to 50 days in a row as from June 11, 2008, and is processing allows to affirm that the conditions of the indoor environment in both houses is severely cold most of the day, being the highest temperatures 15 C at noon and -5 C in the early morning. In apparent contradiction, enough values on net energy entering to the house for thermal comfort were found. But at the same time the existence of elevated air filtrations that play an opposed role is proved. To sum up, the conclusion is that both houses require more protection against cooling instead of diverse mechanisms that increase its warming.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Análisis y diagnóstico térmico en viviendas altoandinas del Perú

El objeto de la investigación que genera este trabajo es diagnosticar la situación térmica actual de cada una de dos viviendas alto andinas del Perú, identificar flujos de calor producidos en ellas y proyectar el mejoramiento térmico correspondiente. Se ha seguido una metodología experimental y analítica apoyada con simulaciones aplicadas a partes específicas de la vivienda. La base de datos experimentales la constituye mediciones y registros automáticos hechos durante 40 a 50 días continuos a partir del 11 de junio de 2008, cuyo procesamiento permite afirmar que las condiciones del ambiente interior de ambas viviendas es severamente frío la mayor parte del día, en el mejor de los casos, se registra 15°C al medio día y -5°C en horas de la madrugada. En aparente contradicción se obtienen potenciales de energía solar ganable por cada vivienda, que podrían ser suficientes para conseguir en ellas las condiciones de confort requeridas, mas paralelamente, se comprueba la existencia de filtraciones de aire elevadas que juegan un papel contrario. En suma, la percepción concluyente es que ambas viviendas requieren de mayor protección contra el enfriamiento que agregados diversos que incrementen su calentamiento.The purpose of the research that stems from this work is to diagnose the current thermal situation of each and every dwelling in the highlands of Peru, to identify heat flows produced inside them and to forecast their thermal improvement. An experimental and analytical methodology has been used, supported by simulations applied to specific parts of the house. The experimental database is constituted by automatic measurements and records taken during 40 to 50 days in a row as from June 11, 2008, and is processing allows to affirm that the conditions of the indoor environment in both houses is severely cold most of the day, being the highest temperatures 15 C at noon and -5 C in the early morning. In apparent contradiction, enough values on net energy entering to the house for thermal comfort were found. But at the same time the existence of elevated air filtrations that play an opposed role is proved. To sum up, the conclusion is that both houses require more protection against cooling instead of diverse mechanisms that increase its warming.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Análisis y diagnóstico térmico en viviendas altoandinas del Perú

El objeto de la investigación que genera este trabajo es diagnosticar la situación térmica actual de cada una de dos viviendas alto andinas del Perú, identificar flujos de calor producidos en ellas y proyectar el mejoramiento térmico correspondiente. Se ha seguido una metodología experimental y analítica apoyada con simulaciones aplicadas a partes específicas de la vivienda. La base de datos experimentales la constituye mediciones y registros automáticos hechos durante 40 a 50 días continuos a partir del 11 de junio de 2008, cuyo procesamiento permite afirmar que las condiciones del ambiente interior de ambas viviendas es severamente frío la mayor parte del día, en el mejor de los casos, se registra 15°C al medio día y -5°C en horas de la madrugada. En aparente contradicción se obtienen potenciales de energía solar ganable por cada vivienda, que podrían ser suficientes para conseguir en ellas las condiciones de confort requeridas, mas paralelamente, se comprueba la existencia de filtraciones de aire elevadas que juegan un papel contrario. En suma, la percepción concluyente es que ambas viviendas requieren de mayor protección contra el enfriamiento que agregados diversos que incrementen su calentamiento.The purpose of the research that stems from this work is to diagnose the current thermal situation of each and every dwelling in the highlands of Peru, to identify heat flows produced inside them and to forecast their thermal improvement. An experimental and analytical methodology has been used, supported by simulations applied to specific parts of the house. The experimental database is constituted by automatic measurements and records taken during 40 to 50 days in a row as from June 11, 2008, and is processing allows to affirm that the conditions of the indoor environment in both houses is severely cold most of the day, being the highest temperatures 15 C at noon and -5 C in the early morning. In apparent contradiction, enough values on net energy entering to the house for thermal comfort were found. But at the same time the existence of elevated air filtrations that play an opposed role is proved. To sum up, the conclusion is that both houses require more protection against cooling instead of diverse mechanisms that increase its warming.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Assessment of cellulose nanofibers from bolaina blanca wood obtained at three shaft heights

This study evaluated cellulose nanofibers from bolaina blanca wood (Guazuma crinita) obtained at different heights of the longitudinal axis of the shaft of trees from a three-and-a-half-year-old plantation. The wood was subjected to pulping, bleaching and subsequent mechanical milling using a Changsha Samy XYQM-2L planetary ball mill to obtain cellulose nanofibers. The product was characterised using analytical techniques: scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy. Additionally, the degree of polymerisation was determined. The effect of longitudinal position on cellulose nanofibers characteristics was evaluated by comparing means using ANOVA and Kruskal–Wallis statistical tests. The yield of cellulose nanofibers production from the high, middle and basal sections was 32,1 %, 33,6 % and 31 %, respectively. The obtained cellulose nanofibers exhibited a significantly larger diameter for the high zone (84 nm) compared with the middle (75 nm) and basal (69 nm) zones; the length remained above the micrometre range. With respect to degree of polymerisation, a decrease was evidenced with respect to the increase in shaft height; the basal zone exhibited a degree of polymerisation of 300, a significantly higher value than the middle and high zones, which exhibited degree of polymerisation of 249 and 211, respectively. The product showed typical cellulose type I polymorphism and crystallinity indexes of 76 %, 93 % and 96 % for the high, middle and basal sections, respectively. Regarding the thermostability of cellulose nanofibers, the maximum degradation rate of cellulose nanofibers occurred between 335 °C and 341 °C, with cellulose nanofibers from the basal area being the most stable. The adsorption of the methylene blue dye on cellulose nanofibers was evaluated; an efficiency > 60 % was found

Exportación de sirope de agave cordillerensis orgánico para el mercado alemán

El presente trabajo tiene por objetivo general determinar la viabilidad económica-financiera de una empresa productora y exportadora de sirope de Agave cordillerensis orgánico con destino a Alemania, considerando como objetivos específicos: - Investigar la oferta de de sirope de agave actual y potencial desde el Perú. - Investigar la demanda en el mercado alemán. - Analizar los factores internos y externos. - Desarrollar planes de operaciones, de recursos humanos y comercial. - Desarrollar y evaluar un Plan Económico Financiero. La cadena productiva se inicia en una zona altoandina cercana a Huancayo, mediante el acopio de aguamiel con certificación orgánica, siendo trasladado a la planta procesadora, a fin de obtener el producto exportable como granel. Se identificó Alemania como mercado objetivo por potencial y entorno favorables. El análisis comparativo entre producto mexicano (líder) y peruano determinó que éste último tiene menor contenido de fructosa y mayor contenido de fructooligosacáridos, lo cual permite ofrecer un producto más saludable. En cuanto a la evaluación económica-financiera, se concluye que el plan de negocios en cuestión resulta una oportunidad de negocios atractiva y rentable. Este trabajo de investigación busca servir como referencia para impulsar la industria y la exportación del agave en el Perú