Graduate Recital, Violin

The program consisted of musically and technically challenging pieces. Ballade, Sonata No. 3 Op. 27 By Eugene Ysaye is a very demanding and intense work where the tension is growing throughout the piece into a furious culmination. Sonata in A major for piano and violin by Cesar Franck is a romantic melancholic work that was composed as a wedding gift for Eugene Ysaye\u27s wedding. It prompts feelings of tenderness and nostalgia in 1st and 4th movement. The energetic and vigorous fantasia-like 3d movement follows the energetic and vigorous 2d movement. Strauss sonata for violin and piano is a very challenging piece that demands a very sensible and sensitive ensemble between the piano and the violin

Quantum K-theory of Quiver Varieties and Many-Body Systems

We define quantum equivariant K-theory of Nakajima quiver varieties. We discuss type A in detail as well as its connections with quantum XXZ spin chains and trigonometric Ruijsenaars-Schneider models. Finally we study a limit which produces a K-theoretic version of results of Givental and Kim, connecting quantum geometry of flag varieties and Toda lattice.Comment: v3: 33 pages, some clarifications and correction

Scanning near-field optical microscopy with new probes and feedback modes

Scanning Near-field Optical Microscopy (SNOM) technique enables to overcome Abbe diffraction limit of far-field optics as well as to obtain simultaneously optical and topographical images. While the optical resolution of the method is limited by the aperture size and is typically 50 - 100 nm, an excellent spatial resolution in a topography channel can be realized. Naturally, we need a convenient and precise method to control the distance between the tip and sample for the successful operation of any SNOM device. Nowadays, the most popular method of the SNOM tip-sample distance control is the shear force - based feedback employing a glass fiber attached to the quartz tuning fork (TF). However, the shear-force distance control method is far from the ideal one. The crosstalk between optical and topographical image can warp the results. The forces between the tip and sample are high and in many cases might be destructive. We report the realization of a new approach to the problem: bent sharpened glass optical fibers with carefully controlled sizes of the bent part and the radius of the curvature of the bending were prepared and experimentally exploited as SNOM probes. Detailed analysis of fiber vibration modes shows that realization of truly tapping mode of the probe dithering requires extreme caution. In case of using the second resonance, mode probes vibrate mostly in the shear-force mode unless the bending radius is rather small (0.3 mm) and the probe's tip is short. The probes having these characteristics were prepared and attached to the TF in the double resonance conditions, which enables to achieve a significant quality factor of the sensor. Another common problem of most aperture SNOMs is the fragility of the tip. We proposed and realized the use of different plastic fibers to solve this problem. These fibers look very promising for the use as SNOM probes and are characterized by much less fragility (compare glass and plastic) and greater ease of the tip preparation. For such preparation, hazardous treating with hydrofluoric acid, which remains the most popular approach to prepare SNOM probes from the glass fibers, can be entirely avoided. Fluorescence Resonance Energy Transfer (FRET) is one of the most promising ways to improve the spatial resolution of the SNOM, and the central part of the Thesis is devoted to the elaboration of FRET SNOM. The idea is to use a donor (acceptor) nanoparticle/molecule as local fluorescence center attached to the tip and measure the fluorescence induced by it in the sample (or vice versa) due to the FRET. Ten years ago, this idea was realized at the single molecule level with CdSe nanocrystals and appropriate dye molecules. Despite the high spatial resolution (better than 20 nm) attained in this experiment, it remains an isolated one, and this is for a valid reason: albeit rather large, the photostability of dye molecules and semiconductor nanocrystals still enables to use a single fluorescence center exploiting for imaging only a few minutes at best. Fluorescent centers with high photostability should be used to overcome this problem. Earlier, claimed to be very photostable and bright NV color centers in nanodiamond crystals were proposed. In the Thesis, we show that such a system is not suitable to realize a single fluorescent center FRET SNOM method. We propose to use specific rare-earth ions in crystals to achieve the goal, in particular, LuBO3(Tb) micro- and nanocrystals

Diseño y procesamiento de nuevos materiales compuestos Cerámica-metal (biocermets) para su uso en implantes médicos

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Aplicada. Fecha de lectura: 17 de marzo de 2016Hasta la fecha los biomateriales utilizados en implantes estructurales han sido seleccionados por sus propiedades mecánicas y por tener una influencia nula o muy pequeña en los tejidos vivos que los rodean. Estos materiales satisfacen exclusivamente las condiciones de carga impuestas en entornos fisiológicos pero no reproducen fielmente las propiedades mecánicas, químicas y la compleja arquitectura del hueso. La diferencia entre las propiedades elásticas correspondientes al implante y el hueso adyacente genera una desigual aplicación de carga que provoca la pérdida de fijación del implante y su posible rotura. La naturaleza magnética de los implantes de acero y los formados por aleaciones de Co-Cr provoca una interacción con los campos magnéticos durante las pruebas de diagnósticos realizadas por resonancia magnética nuclear (RMN), lo que da lugar a calentamiento y/o movimiento del implante o artefactos en las imágenes producidas. Las sensibilidad y/o alergias a los implantes metálicos y la posible relación con efectos cancerígenos desarrollados en un periodo corto de tiempo hacen imperativa la eliminación del uso de metales tóxicos en los implantes. Por otro lado, los materiales cerámicos que se utilizan hoy en día (alumina y circona) presentan problemas de fragilidad y envejecimiento. Además, los diferentes materiales usados en prótesis articulares (polímero principalmente) presentan importantes problemas clínicos debidos a su gran desgaste y la generación de partículas. Por lo tanto, tras décadas de investigación todavía existe la necesidad de desarrollar implantes con adecuadas propiedades mecánicas, biocompatibilidad, alta resistencia a la corrosion y bajo desgaste, así como una buena osteointegración. En la presente tesis se han desarrollado nuevos materiales multifuncionales con matrices cerámicas (3Y-TZP, Al2O3) con alta dureza, resistencia al desgaste e inercia química reforzados con un metal (Tántalo) no tóxico ni magnéticos mediante diferentes rutas de procesamiento de polvos (homogeneización en vía líquida o vaporización por láser) y sinterización (sin presión, prensado en caliente o por descarga de plasma) y con diferentes microarquitecturas (nano-micro-macro). Se han evaluado las propiedades mecánica tanto en condiciones críticas como subcríticas (fatiga) y las propiedades tribológicas, obteniéndose materiales con altas prestaciones mecánicas. Además también se han determinado las propiedades frente al envejecimiento acelerado, indicando que los materiales desarrollados tienen un comportamiento estable frente al envejecimiento. Por otro lado se ha evaluado su biocompatibilidad mediante estudios de proliferación celular in vitro (células madre mesenquimales humanas) e in vivo II (conejos y perros), que han puesto de manifiesto que estos materiales presentan una alto grado de biocompatibilidad. También, se han realizado estudios de RMN de los materiales implantados, demostrando su completa compatibilidad con esta técnica de diagnóstico. Esta nueva familia de biomateriales muestra una combinación óptima de propiedades (mecánicas, tribológicas y biológicas) que son obtenidas mediante una sinergia de mecanismos a multiples escalas. Esto abre la posibilidad de producir nuevos biomateriales con propiedades específicas para su uso en una gran variedad de aplicaciones como materiales implantables. Algunos ejemplos del rango de estas aplicaciones incluyen implantes articulares (rodilla, cadera, hombro, tobillo), implantes dentales (pernos y pilares), implantes espinales (fijación lumbar y cervical, mecanismos de estabilización, espaciadores, injertos de fusión), fijaciones óseas (tornillos, placas, etc.), y cirugía maxilofacial.Traditional biomaterials for hard tissue replacement up to now have been selected based on their mechanical properties and their ability to remain inert in vivo; this selection has provided materials that satisfy only physiological loading conditions but do not duplicate the mechanical, chemical, and architectural properties of bone. Mismatch of mechanical properties between an implant and surrounding bone may lead to stress and strain imbalances that cause implant loosening and eventual failure. Magnetic nature of stainless steel and cobalt-chromium implants provokes an interaction with the magnetic fields present during MR imaging that result in device movement, device heating or development of an artefact on the collected image. Sensitization and/or elicitation of contact allergy to orthopaedic metallic implants and possible carcinogenic (cancer causing) effects in the medium-short time, then in the near future any toxic metal containing implant has to be avoided. Ceramic implants (alumina and zirconia) present low toughness and susceptibility to flaws, when introduced either during processing or in service. Additionally, zirconia (Y-TZP) ceramics show aging problems. In spite of the various forms of materials combination used for prosthetic implants, the wear of the articulating surface has been the major problem encountered in clinics, especially in the case of total bone replacement. Therefore, after decades of research there is still a need for developing implants with suitable mechanical properties, biocompatibility, high corrosion resistance and low wear, as well as a good osseointegration. In the present PhD Thesis new multifunctional materials containing chemically inert nature, wear resistance and hardness ceramics (3Y-TZP, Al2O3) reinforced by non-toxic and non-magnetic metal (Tantalum) were fabricated by different routes of ceramic powders mixture preparation (wet mixing and laser vaporization) and sintering (without and with applied pressure). The variety of formed structural architectures from nano to micro-macro levels ensure excellent composites' mechanical properties under static and cyclic loading accompanied by a tribological performance. In comparison with commercially available tetragonal zirconia stabilized with 3 mol% of yttria, the obtained compositions showed significant enhancement of resistance towards low-temperature degradation. In vitro studies (mesenquimal cells) and in vivo studies in New Zealand white rabbits and Beagle dogs revealed that 3Y-TZP/Ta biocermets appeared to be biocompatible. Moreover, Magnetic Resonance Imaging (MRI) results confirmed compatibility of this diagnostic technique with the new developed biocermet. These new family of biomaterials has an optimal combination of properties (mechanical, tribological and biological) that have been developed using synergistic mechanisms at multiple lengths scales. This opens the possibility to produce novel biomaterials with such properties to make implants for a variety of different hard tissue replacement applications. Some examples of the range of applications include load bearing applications (hip, knee, shoulder, ankle), plates for fractures, dental implants (posts), screws and staples, spinal implants, maxillofacial surgery to name just a few

First direct identification of the barlens vertical structure in galaxy models

Applying spectral dynamics methods to one typical $N$-body model with a barlens, we dissect the modelled bar into separate components supported by completely different types of orbits. We identify at least four components: a narrow elongated bar, a boxy bar, and two components contributing to the barlens. We analyse the vertical structure of all components that make up the thick part of the bar, which has a boxy/peanut shape (B/P bulge). We show that the `peanut' shape is mainly due to the orbits that assemble the boxy part of the face-on bar. We associate the X-shape with the narrow and elongated bar. The wider part of the barlens with square-like isophotes contributes to the boxy shape of the B/P bulge when we observe the galaxy edge-on. However, the part of the barlens with rounded isophotes in the face-on view is a rather flat structure in the vertical direction without any significant off-centre protrusions. Thus, for the first time, we demonstrate that the rounded face-on barlens cannot be entirely associated with the B/P bulge.Comment: 5 pages, 5 figures, accepted to Astronomy and Astrophysics on March 26, 202