1,355,409 research outputs found
Regímenes de memoria y usos políticos y sociales del tiempo pasado : conversación con Mario Rufer.
No full textMario Rufer es profesor-investigador en la Universidad Autónoma Metropolitana - Xochimilco, México, donde fundó y coordinó hasta 2020 el Doctorado en Humanidades. Sus investigaciones versan sobre los estudios culturales y poscoloniales en América Latina; sobre patrimonio, memoria y archivo; y sobre usos públicos del pasado y del tiempo en México, Suráfrica y Argentina. En ese marco ha escrito también sobre museos, exhibiciones y narrativas de nación ([email protected]). Cristóbal Gnecco es profesor del departamento de Antropología de la Universidad del Cauca, donde coordina el Doctorado en Antropología ([email protected]). Iniciamos esta conversación en Popayán (Colombia) en abril de 2019, cuando Mario fue profesor visitante en el Doctorado en Antropología de la Universidad del Cauca, y la continuamos a lo largo de varios meses por medios remotos. La versión en video, aunque muy diferente, puede verse en https://www.youtube.com/watch?v=e3Jv1nm9GA
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[Tom Rufer portrait picture]
No full textPhotograph of Tom Rufer, Director of the University Union at UNT, sitting for a side-profile portrait picture. He is wearing a vertical striped shirt, a patterned tie, and glasses
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[Tom Rufer at auditorium entrance]
No full textPhotograph of Tom Rufer, the Union Director, standing near the entrance to an auditorium in the University Union building. He is holding a set of papers and students are visible through the doors along with a large projection screen
Der Rufer
No full textText. Images. Audio of Der Rufer for percussion quartet.NOTE: Der RuferDer Rufer, for percussion quartet was written for and dedicated to Olaf Tzschoppe and the Bremer Schlagzeugensemble and is the first result of a planned, long-term collaboration between Lund University/Malmö Academy of Music and the European Spallation Source, a multi-disciplinary research facility based on the world’s most powerful neutron source. ESS will enable scientific breakthroughs in research related to materials, energy, health and the environment, and addressing some of the most important societal challenges of our time. In the first step of this cooperation, I collaborated with John Weisend, Deputy Head of Accelerator Projects at ESS looking at the issues surrounding turbulence in superfluid helium.The title, Der Rufer refers to a sculpture in Bremen by Gerhard Marcks (1889 – 1981) that refers to a Greek Herald from Homer’s Iliad. On the base of the sculpture is written: Der Rufer is modeled on the figure of the stentor (Herald, bard, or crier) who shouted as loudly as fifty men in a generous and brazen voice (Homer, Iliad, 730 BC).For some time, I have been interested in the motions of turbulence in fluids and was intrigued to enter into discussions about perhaps one of the greatest discoveries in physics in the first half of the 20th century, that of superfluidity. Superfluid helium (also known as He II) occurs when liquid helium is cooled to within 2.172 degrees of absolute zero (absolute zero is about -273° C). In this ultra-cool region, helium can flow without viscosity or friction, but seldom without turbulence. As I learned through discussions and readings of the literature, superfluidity refers to the flow of a fluid through a tube or pipe with no friction or viscosity. Let’s compare for a second that of normal helium fluid flow that has viscosity and thus friction near the walls of a tube or pipe. An important property for many mechanical systems, including musical instruments, viscosity refers to the measure of the resistance of some element to deformation, or how thick or sticky something is. For example, syrup is higher in viscosity than water. This is how most fluids (including airflow) react in the real world.But, fluids with zero viscosity are extremely rare. When a fluid is produced with zero viscosity this means the fluid can flow without any loss of kinetic energy. What this means is that if you started water flowing in a small capillary tube the flow will eventually stop since atoms in the liquid will collide with one another and with the tube wall and slow down. But if you did that with superfluid helium and come back 10 years later, the liquid will still be moving.Superfluid helium features other amazing behaviors, like the ability of a fluid to flow up the side of a wall or to fit into and flow through impossibly small, molecular-wide spaces, or for the body of the fluid to remain steady when a container is spun, or to produce a frictionless fountain that will flow forever. In my composition Der Rufer, I loosely modeled eight principles involved in ultra-cold physics
Der Rufer [Elektronisk resurs]
No full textText. Images. Audio of Der Rufer for percussion quartet. NOTE: Der Rufer Der Rufer, for percussion quartet was written for and dedicated to Olaf Tzschoppe and the Bremer Schlagzeugensemble and is the first result of a planned, long-term collaboration between Lund University/Malmö Academy of Music and the European Spallation Source, a multi-disciplinary research facility based on the world’s most powerful neutron source. ESS will enable scientific breakthroughs in research related to materials, energy, health and the environment, and addressing some of the most important societal challenges of our time. In the first step of this cooperation, I collaborated with John Weisend, Deputy Head of Accelerator Projects at ESS looking at the issues surrounding turbulence in superfluid helium. The title, Der Rufer refers to a sculpture in Bremen by Gerhard Marcks (1889 – 1981) that refers to a Greek Herald from Homer’s Iliad. On the base of the sculpture is written: Der Rufer is modeled on the figure of the stentor (Herald, bard, or crier) who shouted as loudly as fifty men in a generous and brazen voice (Homer, Iliad, 730 BC). For some time, I have been interested in the motions of turbulence in fluids and was intrigued to enter into discussions about perhaps one of the greatest discoveries in physics in the first half of the 20th century, that of superfluidity. Superfluid helium (also known as He II) occurs when liquid helium is cooled to within 2.172 degrees of absolute zero (absolute zero is about -273° C). In this ultra-cool region, helium can flow without viscosity or friction, but seldom without turbulence. As I learned through discussions and readings of the literature, superfluidity refers to the flow of a fluid through a tube or pipe with no friction or viscosity. Let’s compare for a second that of normal helium fluid flow that has viscosity and thus friction near the walls of a tube or pipe. An important property for many mechanical systems, including musical instruments, viscosity refers to the measure of the resistance of some element to deformation, or how thick or sticky something is. For example, syrup is higher in viscosity than water. This is how most fluids (including airflow) react in the real world. But, fluids with zero viscosity are extremely rare. When a fluid is produced with zero viscosity this means the fluid can flow without any loss of kinetic energy. What this means is that if you started water flowing in a small capillary tube the flow will eventually stop since atoms in the liquid will collide with one another and with the tube wall and slow down. But if you did that with superfluid helium and come back 10 years later, the liquid will still be moving. Superfluid helium features other amazing behaviors, like the ability of a fluid to flow up the side of a wall or to fit into and flow through impossibly small, molecular-wide spaces, or for the body of the fluid to remain steady when a container is spun, or to produce a frictionless fountain that will flow forever. In my compositionDer Rufer, I loosely modeled eight principles involved in ultra-cold physics
Scotland’s international competitiveness within Western Europe
No full textThe paper measures regional competitiveness of Scotland in comparison to ten EU regions and small countries using the International Benchmarking Index Family (‘IB Index Family’) developed by BAK Basel Economics.1 The IB Index Family contains an index with three dimensions of competitiveness: Performance, Attractiveness and Structural Potential. The Performance Index measures recent economic success; the Attractiveness Index measures how well a region is an attractive location to companies and highly-qualified individuals; and the Structural Potential Index estimates future potential economic growth based on current economic structure. The application of the IB Index Family provides a first-step into a more in-depth benchmarking of the competitiveness of a region, which is necessary when working towards detailed policy conclusions. The paper explains these measurement tools and applies them in a short benchmarking analysis of Scotland and ten EU regions and small nations (e.g. Ireland, Norway, Western Sweden etc.)
Magma generation at the easternmost section of the Hellenic arc: Hf, Nd, Pb and Sr isotope geochemistry of Nisyros and Yali volcanoes (Greece)
No full textGeochemical and petrographical studies of lavas and ignimbrites from the Quaternary Nisyros–Yali volcanic system in the easternmost part of the Hellenic arc (Greece) reveal insight into magma generating processes. A compositional gap between 61 and 68 wt.% SiO2 is recognized that coincides with the stratigraphic distinction between pre-caldera and post-caldera volcanic units. Trace element systematics support the subdivision of Nisyros and Yali volcanic units into two distinct suites of rocks. The variation of Nd and Hf present day isotope data and the fact that they are distinct from the isotope compositions of MORB rule out an origin by pure differentiation and require assimilation of a crustal component. Lead isotope ratios of Nisyros and Yali volcanic rocks support mixing of mantle material with a lower crust equivalent. However, 87Sr/86Sr ratios of 0.7036–0.7048 are incompatible with a simple binary mixing scenario and give low depleted mantle extraction ages (<0.1 Ga), in contrast with Pb model ages of 0.3 Ga and Hf and Nd model ages of ca. 0.8 Ga. The budget of fluid-mobile elements Sr and Pb is likely to be dominated by abundant hydrous fluids characterised by mantle-like Sr isotope ratios. Late stage fluids probably were enriched in CO2, needed to explain the high Th concentrations. The occurrence of hydrated minerals (e.g., amphibole) in the first post-caldera unit with the lowermost 87Sr/86Sr ratio of 0.7036±2 can be interpreted as the result of the increased water activity in the source. The presence of two different plagioclase phenocryst generations in the first lava subsequent to the caldera-causing event is indicative for a longer storage time of this magma at a shallower level. A model capable of explaining these observations involves three evolutionary stages. First stage, assimilation of lower crustal material by a primitive magma of mantle origin (as modelled by Nd–Hf isotope systematics). This stage ended by an interruption in replenishment that led to an increase of crystallization and, hence, an increase in viscosity, suppressing eruption. During this time gap, differentiation by fractional crystallization led to enrichment of incompatible species, especially aqueous fluids, to silica depolymerisation and to a decrease in viscosity, finally enabling eruption again in the third stage
Piezoelectric MEMS Acoustic Transducer with Electrically-Tunable Resonant Frequency
No full textThe paper presents a technique to obtain an electrically-tunable matching between the series and parallel resonant frequencies of a piezoelectric MEMS acoustic transducer to increase the effectiveness of acoustic emission/detection in voltage-mode driving and sensing. The piezoelectric MEMS transducer has been fabricated using the PiezoMUMPs technology, and it operates in a plate flexural mode exploiting a 6 mm × 6 mm doped silicon diaphragm with an aluminum nitride (AlN) piezoelectric layer deposited on top. The piezoelectric layer can be actuated by means of electrodes placed at the edges of the diaphragm above the AlN film. By applying an adjustable bias voltage Vb between two properly-connected electrodes and the doped silicon, the d31 mode in the AlN film has been exploited to electrically induce a planar static compressive or tensile stress in the diaphragm, depending on the sign of Vb, thus shifting its resonant frequency. The working principle has been first validated through an eigenfrequency analysis with an electrically induced prestress by means of 3D finite element modelling in COMSOL Multiphysics®. The first flexural mode of the unstressed diaphragm results at around 5.1 kHz. Then, the piezoelectric MEMS transducer has been experimentally tested in both receiver and transmitter modes. Experimental results have shown that the resonance can be electrically tuned in the range Vb = ±8 V with estimated tuning sensitivities of 8.7 ± 0.5 Hz/V and 7.8 ± 0.9 Hz/V in transmitter and receiver modes, respectively. A matching of the series and parallel resonant frequencies has been experimentally demonstrated in voltage-mode driving and sensing by applying Vb = 0 in transmission and Vb = −1.9 V in receiving, respectively, thereby obtaining the optimal acoustic emission and detection effectiveness at the same operating frequency
Conferencia magistral Hacia una teoría de la horizontalidad
No full textLa Plataforma para el Diálogo. La horizontalidad en la investigación social interdisciplinaria desde el conocimiento generado por la Red CALAS invitan a la Conferencia magistral: hacia una teoría de la horizontalidad. Con la participación de: Rufer Mario y Sarah Corona, el lunes 23 de septiembre de 2024 a las 09h45 (hora Ecuador) : FLACSO Ecuador, Quito
Modeling and Measurement of an Ultrasound Power Delivery System for Charging Implantable Devices Using an AlN-Based pMUT as Receiver
No full textUltrasound power delivery can be considered a convenient technique for charging implantable medical devices. In this work, an intra-body system has been modeled to characterize the phenomenon of ultrasound power transmission. The proposed system comprises a Langevin transducer as transmitter and an AlN-based square piezoelectric micro-machined ultrasonic transducer as receiver. The medium layers, in which elastic waves propagate, were made by polydimethylsiloxane to mimic human tissue and stainless steel to replace the case of the implantable device. To characterize the behavior of the transducers, measurements of impedance and phase, velocity and displacement, and acoustic pressure field were carried out in the experimental activity. Then, voltage and power output were measured to analyze the performance of the ultrasound power delivery system. For a root mean square voltage input of approximately 35 V, the power density resulted in 21.6 mu W cm(-2). Such a result corresponds to the data obtained with simulation through a one-dimensional lumped parameter transmission line model. The methodology proposed to develop the ultrasound power delivery (UPD) system, as well as the use of non-toxic materials for the fabrication of the intra-body elements, are a valid design approach to raise awareness of using wireless power transfer techniques for charging implantable devices
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