High-Sensitivity Measurement of 3He-4He Isotopic Ratios for Ultracold Neutron Experiments

Research efforts ranging from studies of solid helium to searches for a neutron electric dipole moment require isotopically purified helium with a ratio of 3He to 4He at levels below that which can be measured using traditional mass spectroscopy techniques. We demonstrate an approach to such a measurement using accelerator mass spectroscopy, reaching the 10e-14 level of sensitivity, several orders of magnitude more sensitive than other techniques. Measurements of 3He/4He in samples relevant to the measurement of the neutron lifetime indicate the need for substantial corrections. We also argue that there is a clear path forward to sensitivity increases of at least another order of magnitude.Comment: 11 pages, 10 figure

An Optomechanical Oscillator on a Silicon Chip

The recent observation on radiation-pressure-driven self-sustained oscillation in high-Q optical microresonators has created new possibilities for development of photonic devices that benefit from unique functionalities offered by these “optomechanical oscillators” (OMOs). Here, we review the physics, fundamental characteristics, and potential applications of OMOs using the silica microtoroidal OMO as an example

High-sensitivity measurement of ^3He−^4He isotopic ratios for ultracold neutron experiments

Research efforts ranging from studies of solid helium to searches for a neutron electric dipole moment require isotopically purified helium with a ratio of ^3He to ^4He at levels below that which can be measured using traditional mass spectroscopy techniques. We demonstrate an approach to such a measurement using accelerator mass spectroscopy, reaching the 10^(−14) level of sensitivity, several orders of magnitude more sensitive than other techniques. Measurements of ^3He/^4He in samples relevant to the measurement of the neutron lifetime indicate the need for substantial corrections. We also argue that there is a clear path forward to sensitivity increases of at least another order of magnitude

Ontologies and Information Extraction

This report argues that, even in the simplest cases, IE is an ontology-driven process. It is not a mere text filtering method based on simple pattern matching and keywords, because the extracted pieces of texts are interpreted with respect to a predefined partial domain model. This report shows that depending on the nature and the depth of the interpretation to be done for extracting the information, more or less knowledge must be involved. This report is mainly illustrated in biology, a domain in which there are critical needs for content-based exploration of the scientific literature and which becomes a major application domain for IE

TRPV1 channels are critical brain inflammation detectors and neuropathic pain biomarkers in mice

The capsaicin receptor TRPV1 has been widely characterized in the sensory system as a key component of pain and inflammation. A large amount of evidence shows that TRPV1 is also functional in the brain although its role is still debated. Here we report that TRPV1 is highly expressed in microglial cells rather than neurons of the anterior cingulate cortex and other brain areas. We found that stimulation of microglial TRPV1 controls cortical microglia activation per se and indirectly enhances glutamatergic transmission in neurons by promoting extracellular microglial microvesicles shedding. Conversely, in the cortex of mice suffering from neuropathic pain, TRPV1 is also present in neurons affecting their intrinsic electrical properties and synaptic strength. Altogether, these findings identify brain TRPV1 as potential detector of harmful stimuli and a key player of microglia to neuron communication

Assessing the geometry and tuning properties of historical timbilas through non-destructive reverse engineering techniques

Timbilas are xylophones finely manufactured and tuned by the Chopi people from Mozambique. In the context of a research project, we aim at assessing the construction and acoustical features of a set of historical instruments by developing non-destructive characterization techniques based on reverse engineering, with main objectives to assess their original tuning and musical scale. In this thesis, we present the methodology and workflow that have been developed for the study of the collection of historical timbilas of the National Museum of Ethnology of Lisbon, which is the world's largest collection of the Mozambican instrument. In a first stage, contactless geometrical measurements were performed on a ninebar timbila by using 3D scanning Technology, resulting in a detailed geometrical description of the instrument bars. In a second stage, the 3D collected geometrical data was used as input to Finite Element computations in order to calculate the modal frequencies and mode shapes of each bar of the instrument. Results stemming from our modal computations were compared with modal data obtained from vibrational measurements, proving the efficiency of the proposed approach. Final stage was using the data as input for developing a sound synthesis model for recreating the sound of the timbila bars.Timbilas são xilofones cuidadosamente construídos e afinados pelos Chopes, povo de Moçambique que cultiva uma das mais importantes tradições musicais do sul da África. No contexto de um projeto interdisciplinar de investigação, objetivamos avaliar as características geométricas e acústicas de alguns exemplares históricos, desenvolvendo técnicas não-destrutivas de caracterização baseadas num processo de engenharia reversa, com o principal objetivo de avaliar a afinação e a escala musical de um conjunto de instrumentos. A metodologia desenvolvida consiste no levantamento preciso da geometria das barras a partir de tecnologia de imagens scanner 3D, resultando numa descrição detalhada de sua morfologia. Num segundo passo, realizamos cálculos modais a partir de um modelo por Elementos Finitos 3D construido a partir dos dados coletados, a fim de calcular as frequências modais e formas vibratórias das principais ressonâncias de cada barra do instrumento. Os resultados dos cálculos modais foram finalmente comparados com os valores de parâmetros modais identificados a partir de medições vibratórias, demonstrando a utilidade e eficácia da metodologia proposta. O estágio final foi a utilização dos dados para criar um modelo de síntese sonora para as barras da timbila