Disseny d'un prototip per a una bicicleta de descens

En aquest projecte es presenta el disseny d’un quadre per a una bicicleta de muntanya, pensada per a la competició de descens. El disseny d’aquest quadre es basa en la disposició d’una boixa amb canvi de marxes integrat. D’aquesta manera s’aconsegueix compactar el mecanisme de transmissió molt a prop del centre de gravetat, i disminuir el nombre d’elements exposats a impactes amb elements de l’entorn. El quadre també disposa d’un sistema de suspensió amb bieletes, que ha sigut dissenyat amb el software ―Linkage‖: un software que permet l’anàlisi de sistemes de suspensió en 2D, centrat per a bicicletes de muntanya. El disseny s’ha dut a terme amb AutoCad (2d) i en SolidWorks (3D), que també ha permès fer l’anàlisi d’elements finits amb les dades extretes de Linkage i anàlisis teòrics. La idea del projecte es la de construir un primer prototip que permeti realitzar les probes pertinents abans del disseny final per a la fabricació i comercialització

Polyurethane shape memory filament yarns: Melt spinning, carbon-based reinforcement, and characterization

The aim of this work was to develop and characterize polyurethane-based shape memory polymer filament yarns of a suitable diameter and thermo-mechanical performance for use in tailored multi-sectorial applications. Different polymer compositions – pure shape memory polyurethane and shape memory polyurethane composites with 0.3 and 0.5 wt.% of multi-walled carbon nanotubes or carbon black as additives – were studied. Filaments were obtained using a melt spinning process that allowed the production of the permanent and temporary shape of the shape memory polyurethane filament. Two drawing speeds (20 and 32¿m/min) were studied. Characterization techniques such as the tensile test, differential scanning calorimetry, and dynamic mechanical analysis were used to investigate the shape-memory effect of the filaments. Pure and additive shape memory polyurethane filament yarns of a controlled diameter were produced. The results indicated that the pure shape memory polyurethane on the temporary shape had the highest tensile strength (234¿MPa). Filaments with carbon black revealed a significant strain (335%) in the permanent shape with respect to the other filaments. The melt spinning process influenced the soft segment glass transition temperature (Tgs) significantly, with a decrease in the temporary shape (first heating) as compared to the permanent shape (second and third heating). However, only the 0.5% multi-walled carbon nanotubes additive clearly influenced the filament, increasing the Tgs by 10°C. The additives also influenced the shape-memory effect, obtaining an increased fixity ratio (up to 97%) with the multi-walled carbon nanotubes additive and an increased recovery ratio (up to 86%) with the carbon black additivePostprint (author's final draft

Design and characterization of reversible thermodynamic SMPU-based fabrics with improved comfort properties

In recent years, great efforts have been made to research and develop advanced thermodynamic textiles that can change their thermal behavior in response to external stimuli. More specifically, shape memory alloys and shape memory polymer coatings have used for thermal comfort applications. However, the use of shape memory polymers in the form of filament yarns integrated in the fabrics has not yet reported. These fabrics have some advantages related to versatility in shape design. The aim of this study was to develop woven SMPU-based fabrics with reversible thermodynamic properties induced by weft SMPU filament yarns interlaced into polyester (PES) fabrics. To this end, PES woven fabrics with different ratios of weft SMPU filament yarns (PES/SMPU 1:0; 3:1; 1:1; 1: 3, and 0:1) were developed and their thermodynamic properties (thermal resistance, water vapor resistance, and permeability index), shape memory effect, and mechanical performance were evaluated and compared to the 100% PES reference fabric. All the SMPU-based fabrics developed were classified as extremely breathable (water vapor resistance <6 m2 Pa/W) and thermally comfortable (water vapor permeability index <0.3). The fabrics integrating the SMPU filament yarns reacted dynamically to the temperature stimuli over and below Tg, whereas the 100% PES fabric showed passive thermodynamic behavior. This dynamism led to an improvement in thermal protection against an increase in ambient temperature, reaching values of 13.18 mK m2 /W in thermal resistance (PES/SMPU 0:1), while also maintaining good moisture management properties, reaching values of 5.19 m2 Pa/W in water vapor resistance (PES/SMPU 0:1)The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was financially supported by the Catalan Government through the funding grant ACCIO-Eurecat (Project PRIV – Confortex)Postprint (published version

δ-Opioid and dopaminergic processes in accumbens shell modulate the cholinergic control of predictive learning and choice

Decision-making depends on the ability to extract predictive information from the environment to guide future actions. Outcome-specific Pavlovian-instrumental transfer (PIT) provides an animal model of this process in which a stimulus predicting a particular outcome biases choice toward actions earning that outcome. Recent evidence suggests that cellular adaptations of δ-opioid receptors (DORs) on cholinergic interneurons (CINs) in the nucleus accumbens shell (NAc-S) are necessary for PIT. Here we found that modulation of DORs in CINs critically influences D1-receptor (D1R)-expressing projection neurons in the NAc-S to promote PIT. First, we assessed PIT-induced changes in signaling processes in dopamine D1- and D2-receptor-expressing neurons using drd2-eGFP mice, and found that PIT-related signaling was restricted to non-D2R-eGFP-expressing neurons, suggesting major involvement of D1R-neurons. Next we confirmed the role of D1Rs pharmacologically: the D1R antagonist SCH-23390, but not the D2R antagonist raclopride, infused into the NAc-S abolished PIT in rats, an effect that depended on DOR activity. Moreover, asymmetrical infusion of SCH-23390 and the DOR antagonist naltrindole into the NAc-S also abolished PIT. DOR agonists were found to sensitize the firing responses of CINs in brain slices prepared immediately after the PIT test. We confirmed the opioid-acetylcholinergic influence over D1R-neurons by selectively blocking muscarinic M4 receptors in the NAc-S, which tightly regulate the activity of D1Rs, a treatment that rescued the deficit in PIT induced by naltrindole. We describe a model of NAc-S function in which DORs modulate CINs to influence both D1R-neurons and stimulus-guided choice between goal-directed actions

Learning-related translocation of δ-opioid receptors on ventral striatal cholinergic interneurons mediates choice between goal-directed actions.

The ability of animals to extract predictive information from the environment to inform their future actions is a critical component of decision-making. This phenomenon is studied in the laboratory using the pavlovian-instrumental transfer protocol in which a stimulus predicting a specific pavlovian outcome biases choice toward those actions earning the predicted outcome. It is well established that this transfer effect is mediated by corticolimbic afferents on the nucleus accumbens shell (NAc-S), and recent evidence suggests that delta-opioid receptors (DORs) play an essential role in this effect. In DOR-eGFP knock-in mice, we show a persistent, learning-related plasticity in the translocation of DORs to the somatic plasma membrane of cholinergic interneurons (CINs) in the NAc-S during the encoding of the specific stimulus-outcome associations essential for pavlovian-instrumental transfer. Wefound that increased membrane DOR expression reflected both stimulus-based predictions of reward and the degree to which these stimuli biased choice during the pavlovian-instrumental transfer test. Furthermore, this plasticity altered the firing pattern of CINs increasing the variance of action potential activity, an effect that was exaggerated by DOR stimulation. The relationship between the induction of membrane DOR expression in CINs and both pavlovian conditioning and pavlovian-instrumental transfer provides a highly specific function for DOR-related modulation in the NAc-S, and it is consistent with an emerging role for striatal CIN activity in the processing of predictive information. Therefore, our results reveal evidence of a long-term, experience-dependent plasticity in opioid receptor expression on striatal modulatory interneurons critical for the cognitive control of action

Recuerdos de infancia : niñez y dictadura en Chile (1973-1990) / Childhood memories: chilhood and dictatorship in Chile (1973-1990)

This article presents the results of a research on the experience of childhood during the last civil-military dictatorship in Chile (1973-1990). The role of childhood memories in memory studies of the period is discussed. Perspectives of new studies on childhood are used to draw attention on aspects of daily life that are not readily apparent. Twenty-four open interviews were conducted to persons who experienced childhood during the dictatorship. Each interview was centered around an object (letter, personal diary, postcards, recordings, etc.) made or acquired by the interviewee between 1973 and 1990. In the conclusion there is a reflection about the role of the reconstruction of childhood memories through objects that serve as memory aids and these universal aspects of the experience of childhood in dictatorship. Keywords: Memory, civil-military dictatorship, childhood, material culture

Intrinsic defects and mid-gap states in quasi-one-dimensional Indium Telluride

Recently, intriguing physical properties have been unraveled in anisotropic semiconductors, in which the in-plane electronic band structure anisotropy often originates from the low crystallographic symmetry. The atomic chain is the ultimate limit in material downscaling for electronics, a frontier for establishing an entirely new field of one-dimensional quantum materials. Electronic and structural properties of chain-like InTe are essential for better understanding of device applications such as thermoelectrics. Here, we use scanning tunneling microscopy/spectroscopy (STM/STS) measurements and density functional theory (DFT) calculations to directly image the in-plane structural anisotropy in tetragonal Indium Telluride (InTe). As results, we report the direct observation of one-dimensional In1+ chains in InTe. We demonstrate that InTe exhibits a band gap of about 0.40 +-0.02 eV located at the M point of the Brillouin zone. Additionally, line defects are observed in our sample, were attributed to In1+ chain vacancy along the c-axis, a general feature in many other TlSe-like compounds. Our STS and DFT results prove that the presence of In1+ induces localized gap state, located near the valence band maximum (VBM). This acceptor state is responsible for the high intrinsic p-type doping of InTe that we also confirm using angle-resolved photoemission spectroscopy.Comment: n