Low-aberration beamline optics for synchrotron infrared nanospectroscopy

MCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESSynchrotron infrared nanospectroscopy is a recently developed technique that enables new possibilities in the broadband chemical analysis of materials in the nanoscale, far beyond the diffraction limit in this frequency domain. Synchrotron infrared ports have exploited mainly the high brightness advantage provided by electron storage rings across the whole infrared range. However, optical aberrations in the beam produced by the source depth of bending magnet emission at large angles prevent infrared nanospectroscopy to reach its maximum capability. In this work we present a low-aberration optical layout specially designed and constructed for a dedicated synchrotron infrared nanospectroscopy beamline. We report excellent agreement between simulated beam profiles (from standard wave propagation and raytracing optics simulations) with experimental measurements. We report an important improvement in the infrared nanospectroscopy experiment related to the improved beamline optics. Finally, we demonstrate the performance of the nanospectroscopy endstation by measuring a hyperspectral image of a polar material and we evaluate the setup sensitivity by measuring ultra-thin polymer films down to 6 nm thick.2691123811249MCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕE

Rolled-up tubes and cantilevers by releasing SrRuO3-Pr0.7Ca0.3MnO3 nanomembranes

Three-dimensional micro-objects are fabricated by the controlled release of inherently strained SrRuO3/Pr0.7Ca0.3MnO3/SrRuO3 nanometer-sized trilayers from SrTiO3(001) substrates. Freestanding cantilevers and rolled-up microtubes with a diameter of 6 to 8 μm are demonstrated. The etching behavior of the SrRuO3 film is investigated, and a selectivity of 1:9,100 with respect to the SrTiO3 substrate is found. The initial and final strain states of the rolled-up oxide layers are studied by X-ray diffraction on an ensemble of tubes. Relaxation of the sandwiched Pr0.7Ca0.3MnO3 layer towards its bulk lattice parameter is observed as the major driving force for the roll-up of the trilayers. Finally, μ-diffraction experiments reveal that a single object can represent the ensemble proving a good homogeneity of the rolled-up tubes

A virtual centre at the interface of basic and applied weather and climate research

The Hans-Ertel Centre for Weather Research is a network of German universities, research institutes and the German Weather Service (Deutscher Wetterdienst, DWD). It has been established to trigger and intensify basic research and education on weather forecasting and climate monitoring. The performed research ranges from nowcasting and short-term weather forecasting to convective-scale data assimilation, the development of parameterizations for numerical weather prediction models, climate monitoring and the communication and use of forecast information. Scientific findings from the network contribute to better understanding of the life-cycle of shallow and deep convection, representation of uncertainty in ensemble systems, effects of unresolved variability, regional climate variability, perception of forecasts and vulnerability of society. Concrete developments within the research network include dual observation-microphysics composites, satellite forward operators, tools to estimate observation impact, cloud and precipitation system tracking algorithms, large-eddy-simulations, a regional reanalysis and a probabilistic forecast test product. Within three years, the network has triggered a number of activities that include the training and education of young scientists besides the centre's core objective of complementing DWD's internal research with relevant basic research at universities and research institutes. The long term goal is to develop a self-sustaining research network that continues the close collaboration with DWD and the national and international research community

Rolled-Up Nanotech: Illumination-Controlled Hydrofluoric Acid Etching of AlAs Sacrificial Layers

<p>Abstract</p> <p>The effect of illumination on the hydrofluoric acid etching of AlAs sacrificial layers with systematically varied thicknesses in order to release and roll up InGaAs/GaAs bilayers was studied. For thicknesses of AlAs below 10 nm, there were two etching regimes for the area under illumination: one at low illumination intensities, in which the etching and releasing proceeds as expected and one at higher intensities in which the etching and any releasing are completely suppressed. The &#8220;etch suppression&#8221; area is well defined by the illumination spot, a feature that can be used to create heterogeneously etched regions with a high degree of control, shown here on patterned samples. Together with the studied self-limitation effect, the technique offers a way to determine the position of rolled-up micro- and nanotubes independently from the predefined lithographic pattern.</p

Predicting Ligand-Free Cell Attachment on Next-Generation Cellulose–Chitosan Hydrogels

There is a growing appreciation that engineered biointerfaces can regulate cell behaviors, or functions. Most systems aim to mimic the cell-friendly extracellular matrix environment and incorporate protein ligands; however, the understanding of how a ligand-free system can achieve this is limited. Cell scaffold materials comprised of interfused chitosan–cellulose hydrogels promote cell attachment in ligand-free systems, and we demonstrate the role of cellulose molecular weight, MW, and chitosan content and MW in controlling material properties and thus regulating cell attachment. Semi-interpenetrating network (SIPN) gels, generated from cellulose/ionic liquid/cosolvent solutions, using chitosan solutions as phase inversion solvents, were stable and obviated the need for chemical coupling. Interface properties, including surface zeta-potential, dielectric constant, surface roughness, and shear modulus, were modified by varying the chitosan degree of polymerization and solution concentration, as well as the source of cellulose, creating a family of cellulose–chitosan SIPN materials. These features, in turn, affect cell attachment onto the hydrogels and the utility of this ligand-free approach is extended by forecasting cell attachment using regression modeling to isolate the effects of individual parameters in an initially complex system. We demonstrate that increasing the charge density, and/or shear modulus, of the hydrogel results in increased cell attachment

Surface modified cellulose scaffolds for tissue engineering

We report the ability of cellulose to support cells without the use of matrix ligands on the surface of the material, thus creating a two-component system for tissue engineering of cells and materials. Sheets of bacterial cellulose, grown from a culture medium containing Acetobacter organism were chemically modified with glycidyltrimethylammonium chloride or by oxidation with sodium hypochlorite in the presence of sodium bromide and 2,2,6,6-tetramethylpipiridine 1-oxyl radical to introduce a positive, or negative, charge, respectively. This modification process did not degrade the mechanical properties of the bulk material, but grafting of a positively charged moiety to the cellulose surface (cationic cellulose) increased cell attachment by 70 compared to unmodified cellulose, while negatively charged, oxidised cellulose films (anionic cellulose), showed low levels of cell attachment comparable to those seen for unmodified cellulose. Only a minimal level of cationic surface derivitisation (ca 3 degree of substitution) was required for increased cell attachment and no mediating proteins were required. Cell adhesion studies exhibited the same trends as the attachment studies, while the mean cell area and aspect ratio was highest on the cationic surfaces. Overall, we demonstrated the utility of positively charged bacterial cellulose in tissue engineering in the absence of proteins for cell attachment

La competencia "aprender a aprender" en un contexto educativo de ingeniería

The objective of this thesis was to establish bases to characterize "learn to learn" competence and to promote it in an engineering educational context. It adopted the vision of educational psychology that establishes self-regulation in learning as the operative manifestation of this competence. The research was developed in three phases: obtaining a psychometric tool to characterize self-regulation in learning; the characterization of self-regulation in learning of the students; and, based on the results of the characterization, an educational intervention was designed, implemented and evaluated to facilitate that students use the learning strategy of selection and organization of the information . In the first phase in order to obtain the psychometric tool was translated, adapted and validated the Motivated Strategies for Learning Questionnaire - MSLQ following the guidelines of the International Test Commission (ITC). The result was the MSLQ-Colombia. With the participation of 1218 students and 12 engineering professors, the psychometric properties of MSLQ-Colombia were studied: construct validity, content validity, external validity and reliability; the MSLQ-Colombia was valid and reliable. In the characterization, second phase, the self-regulation of the motivation and the use of learning strategies of 1268 students were evaluated. It was found that students self-regulate their motivation highly: beliefs about learning control and task value were the aspects most self-regulated, while the learning orientation toward extrinsic goals and anxiety in the assessment were the least self-regulated. It was found that students used learning strategies in a non-uniform way, there were strategies frequently used and others occasionally used. The three strategies most used were the monitoring of learning, control of the place of study and effort regulation; the strategies least used were time management and selection and organization of information. The results of this phase also allowed to propose a new hypothesis to investigate the self-regulation in the learning: the self-regulation of some aspects of the motivation and the use of some strategies depend on the subject that the students are coursing; on the contrary, other aspects of motivation and other learning strategies do not depend on the subject. Educational intervention, the third phase, consisted in offering instruction at students on summarizing technique to facilitate them to select and organize the information of engineering technical texts; in addition, students practiced the production of abstracts and the teachers provided them feedback on the quality of these abstracts. The effects of the educational intervention were explored with a quasi-experimental investigation (experimental group: 177 students, control group: 65 students) that collected quantitative and qualitative evidences. The educational intervention facilitated that students increase positive and significantly, in a statistical sense, the writing of abstracts to select and organize the information; the quality of the abstracts also significantly improved. The intervention also impacted the use of strategies such as metacognition and resource management as time management. The results of this thesis provide solutions to the current problems of the "learn to learn" competence: practical contributions such as the MSLQ-Colombia and the didactic sequence of the educational intervention, empirical contributions such as the psychometric indexes of MSLQ-Colombia, the characterization of the self-regulation in learning of students and the impacts of educational intervention. Finally, this thesis sets a new integrative approach (hypothesis) of the previous ones about the research on the self-regulation in learning.El objetivo de esta Tesis fue establecer bases para caracterizar la competencia "aprender a aprender" y potenciarla en un contexto educativo de ingeniería. Se adoptó la visión de la psicología educativa que instaura la autorregulación en el aprendizaje como la manifestación operativa de esta competencia. La investigación se desarrolló en tres fases: obtención de una herramienta psicométrica para caracterizar la autorregulación en el aprendizaje; caracterización de la autorregulación en el aprendizaje de los estudiantes; y, a partir de los resultados de la caracterización, se diseñó, implementó y evaluó una intervención educativa para facilitar a los estudiantes usar la estrategia de aprendizaje selección y organización de la información. En la primera fase para obtener la herramienta psicométrica se tradujo, adaptó y validó el Motivated Strategies for Learning Questionnaire - MSLQ siguiendo las directrices de la International Test Commission (ITC). El resultado fue el MSLQ-Colombia. Con la participación de 1218 estudiantes y 12 profesores de ingeniería se estudiaron las propiedades psicométricas del MSLQ-Colombia: validez de constructo, validez de contenido, validez externa y confiabilidad; el MSLQ-Colombia resultó válido y confiable. En la caracterización, segunda fase, se valoró la autorregulación de la motivación y el uso de estrategias de aprendizaje de 1268 estudiantes. Se encontró que los estudiantes autorregulaban altamente su motivación: las creencias de control del aprendizaje y la valoración de la tarea fueron los aspectos que más autorregularon, mientras que la orientación del aprendizaje hacia metas extrínsecas y la ansiedad en la evaluación fueron los menos autorregulados. Se halló que los estudiantes usaban estrategias de aprendizaje de manera no uniforme, hubo estrategias de uso frecuente y otras de uso ocasional. Las tres estrategias más usadas fueron el monitoreo del aprendizaje, control del lugar de estudio y regulación del esfuerzo; las menos usadas fueron la gestión del tiempo y selección y organización de la información. Los resultados de esta fase también permitieron plantear una nueva hipótesis para investigar la autorregulación en el aprendizaje: la autorregulación de algunos aspectos de la motivación y el uso de algunas estrategias dependen de la asignatura que los estudiantes están cursando; por el contrario, otros aspectos de la motivación y otras estrategias de aprendizaje no dependen de la asignatura. La intervención educativa, tercera fase, consistió en ofrecer a los estudiantes instrucción sobre la técnica de resumir para facilitarles seleccionar y organizar la información de textos técnicos de ingeniería; asimismo, los estudiantes elaboraron resúmenes y se les brindó realimentación sobre la calidad de dichos resúmenes. Los efectos de la intervención educativa se exploraron con una investigación cuasi-experimental (grupo experimental: 177 estudiantes, grupo control: 65 estudiantes) que recolectó evidencias cuantitativas y cualitativas. La intervención educativa facilitó que los estudiantes incrementaran positiva y significativamente, en sentido estadístico, la escritura de resúmenes para seleccionar y organizar la información; los estudiantes también mejoraron significativamente la calidad de los resúmenes. La intervención también impactó el uso de estrategias como la metacognición y la administración de recursos como gestión del tiempo. Los resultados de esta Tesis aportan soluciones a las problemáticas actuales de la competencia "aprender a aprender": contribuciones prácticas como el MSLQ-Colombia y la secuencia didáctica de la intervención educativa; contribuciones empíricas como los índices psicométricos del MSLQ-Colombia, la caracterización de la autorregulación del aprendizaje de los estudiantes y los impactos de la intervención educativa. Por último, esta Tesis establece un nuevo enfoque (hipótesis) integrador de los anteriores en la investigación de la autorregulación del aprendizaje