Laser induced strong-field ionization gas jet tomography

We introduce a novel in-situ strong field ionization tomography approach for characterizing the spatial density distribution of gas jets. We show that for typical intensities in high harmonic generation experiments, the strong field ionization mechanism used in our approach provides an improvement in the resolution close to factor of 2 (resolving about 8 times smaller voxel volume), when compared to linear/single-photon imaging modalities. We find, that while the depth of scan in linear tomography is limited by resolution loss due to the divergence of the driving laser beam, in the proposed approach the depth of focus is localized due to the inherent physical nature of strong-field interaction and discuss implications of these findings. We explore key aspects of the proposed method and compare it with commonly used single- and multi-photon imaging mechanisms. The proposed method will be particularly useful for strong field and attosecond science experiments.Comment: 8 pages, 3 figure

CFD modelling of a mixing chamber for the realisation of functionally graded scaffolds

Biological tissues are characterised by spatially distributed gradients, intricately linked with functions. It is widely accepted that ideal tissue engineered scaffolds should exhibit similar functional gradients to promote successful tissue regeneration. Focusing on bone, in previous work we proposed simple methods to obtain osteochondral functionally graded scaffolds (FGSs), starting from homogeneous suspensions of hydroxyapatite (HA) particles in gelatin solutions. With the main aim of developing an automated device to fabricate FGSs, this work is focused on designing a stirred tank to obtain homogeneous HA-gelatin suspensions. The HA particles transport within the gelatin solution was investigated through computational fluid dynamics (CFD) modelling. First, the steady-state flow field was solved for the continuous phase only. Then, it was used as a starting point for solving the multi-phase transient simulation. CFD results showed that the proposed tank geometry and setup allow for obtaining a homogeneous suspension of HA micro-particles within the gelatin solution

Design and Validation of an Open-Hardware Print-Head for Bioprinting Application

In the last decades drop-on-demand inkjet technology played an increasing role in industrial and medical applications. This is due to the ability to deposit a small amount of material in precisely defined position. In the field of Biofabrication, inkjet printers are used to build 2D and 3D scaffolds and gels with biological molecules, including living cells. Several works, including seminal papers on inkjet bioprinting, were carried out with modified office printers. These printers have fixed structural characteristics and operating size, especially on the print-head, limiting the range of materials that can be dispensed. The aim of the present work is the design and fabrication of an open-source piezoelectric inkjet print-head, optimized for the bioprinting field. This low-cost, reproducible, reliable, versatile and biocompatible device will enable various research laboratories to work with a shared device; the open source allowing for parts to be modified to suit specific needs. The design was carried out by Finite Element (FE) modelling of the piezoelectric, mechanical, fluid dynamics and their coupling. The design was optimized for shear rate, which we minimized in order to be able to print cells. The mechanical frame of the printer was designed and built using a low-cost 3D printer. The nozzle plate was fabricated from a polycarbonate disc coated with biocompatible silicone, to increase the hydrophobicity of the outer surface of the disc, preventing ink adhesion on the edge of the nozzle; the refilling system, and the electronic control were also part of the project and will be freely available to download. The FE models were validated with ad-hoc experiments, printing water, gelatin solution, and cell culture media, by modulating the wave power in amplitude, frequency and duty cycle. The tests showed a large working window both respect to viscosity and to surface tension. Finally Human Skin Fibroblasts (ATCC-CRL- 2522, Teddington UK), suspended in culture media, were printed. Cell viability, assessed by CellTiter-Blue and LIVE / DEAD tests, resulted comparable with the control, demonstrating the validity of the first open source piezoelectric inkjet print-head for biofabrication

¿Sobre qué nos enseñan los errores de nuestros alumnos?. 25 años después…

Quienes presentamos el trabajo integramos un proyecto de investigación “Dificultades en el aprendizaje de la matemática básica en carreras de ingeniería” (Faculta de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario) que tiene entre sus objetivos diseñar e implementar estrategias didácticas que contribuyan a: Acortar distancias entre niveles educativos, Corregir errores arraigados, Retener a los ingresantes a la Facultad, Comprometer al estudiante en su formación, incentivando su independencia y creatividad, Comprometer a los docentes en el abordaje e implementación de alternativas didácticas más eficaces

Dificultades en el aprendizaje de matemática. Obstáculos y errores en el aprendizaje del concepto de dependencia e independencia lineal

En el marco del proyecto de investigación del que formamos parte: “Dificultades en la enseñanza-aprendizaje de matemática en carreras no matemáticas”, ubicamos este trabajo que presentamos como reporte de investigación, ya que da cuenta del diseño de aquellos ciclos que se corresponden con el análisis a priori de una situación de aprendizaje, la recolección de datos en la propia situación y el análisis a posteriori de los resultados. Nos ocupamos en esta etapa del análisis de los errores puestos de manifiesto por los alumnos de 1º año de las carreras de Ingeniería, en relación a un tema específico del Álgebra Lineal, como es Dependencia e Independencia Lineal

CO2\mathrm{CO_2} exploding clusters dynamics probed by XUV fluorescence

Clusters excited by intense laser pulses are a unique source of warm dense matter, that has been the subject of intensive experimental studies. The majority of those investigations concerns atomic clusters, whereas the evolution of molecular clusters excited by intense laser pulses is less explored. In this work we trace the dynamics of $\mathrm{CO_2}$ clusters triggered by a few-cycle 1.45-$\mu$m driving pulse through the detection of XUV fluorescence induced by a delayed 800-nm ignition pulse. Striking differences among fluorescence dynamics from different ionic species are observed

“Aprender a aprender” – una experiencia en geometría analítica

El análisis de las manifestaciones de los alumnos, registradas a través de encuestas y entrevistas, acerca de sus dificultades para asumir con autonomía el propio aprendizaje, nos llevó a iniciar una investigación con el objetivo de elaborar actividades facilitadoras para aprender significativamente, para “aprender a aprender”. Constituimos un equipo, involucrando a otros docentes de las cátedras de Álgebra y Geometría Analítica, orientando nuestras acciones por una parte a la discusión sobre los obstáculos que traban el aprendizaje, atribuibles a dificultades intrínsecas de la disciplina en estudio o a las propias posibilidades del alumnos o a errores pedagógicos y por otra parte a la búsqueda y selección de metodologías válidas para el logro de nuestro objetivo

Touch sensor for social robots and interactive objects affective interaction

The recognised importance of physical experience in empathic exchanges has led to the development of touch sensors for human–robot affective interaction. Most of these sensors, implemented as matrix of pressure sensors, are rigid, cannot be fabricated in complex shapes, cannot be subjected to large deformations, and usually allow to capture only the contact event, without any information about the interaction context. This paper presents a tactile flux sensor able to capture the entire context of the interaction including gestures and patterns. The sensor is made of alternate layers of sensitive and insulating silicone: the soft nature of the sensor makes it adaptable to complex and deformable bodies. The main features from electrical signals are extracted with the principal component analysis, and a self-organising neural network is in charge for the classification and spatial identification of the events to acknowledge and measure the gesture. The results open to interesting applications, which span from toy manufacturing, to human-robot interaction, and even to sport and biomedical equipment and applications

Studying the universality of field induced tunnel ionization times via high-order harmonic spectroscopy

High-harmonics generation spectroscopy is a promising tool for resolving electron dynamics and structure in atomic and molecular systems. This scheme, commonly described by the strong field approximation, requires a deep insight into the basic mechanism that leads to the harmonics generation. Recently, we have demonstrated the ability to resolve the first stage of the process -- field induced tunnel ionization -- by adding a weak perturbation to the strong fundamental field. Here we generalize this approach and show that the assumptions behind the strong field approximation are valid over a wide range of tunnel ionization conditions. Performing a systematic study -- modifying the fundamental wavelength, intensity and atomic system -- we observed a good agreement with quantum path analysis over a range of Keldysh parameters. The generality of this scheme opens new perspectives in high harmonics spectroscopy, holding the potential of probing large, complex molecular systems.Comment: 11 pages, 5 figure

Molecular Imprinting Strategies for Tissue Engineering Applications: A Review

Tissue Engineering (TE) represents a promising solution to fabricate engineered constructs able to restore tissue damage after implantation. In the classic TE approach, biomaterials are used alongside growth factors to create a scaffolding structure that supports cells during the construct maturation. A current challenge in TE is the creation of engineered constructs able to mimic the complex microenvironment found in the natural tissue, so as to promote and guide cell migration, proliferation, and differentiation. In this context, the introduction inside the scaffold of molecularly imprinted polymers (MIPs)-synthetic receptors able to reversibly bind to biomolecules-holds great promise to enhance the scaffold-cell interaction. In this review, we analyze the main strategies that have been used for MIP design and fabrication with a particular focus on biomedical research. Furthermore, to highlight the potential of MIPs for scaffold-based TE, we present recent examples on how MIPs have been used in TE to introduce biophysical cues as well as for drug delivery and sequestering