Single-Particle Self-Excited Oscillator

Electronic feedback is used to self-excite the axial oscillation of a single electron in a Penning trap. Large, stable, easily detected oscillations arise even in an anharmonic potential. Amplitudes are controlled by adjusting the feedback gain, and frequencies can be made nearly independent of amplitude fluctuations. Quantum jump spectroscopy of a perpendicular cyclotron motion reveals the absolute temperature and amplitude of the self-excited oscillation. The possibility to quickly measure parts per billion frequency shifts could open the way to improved measurements of e-, e+, p, and [overline p] magnetic moments

Optimal Exploitation of the Sentinel-2 Spectral Capabilities for Crop Leaf Area Index Mapping

The continuously increasing demand of accurate quantitative high quality information on land surface properties will be faced by a new generation of environmental Earth observation (EO) missions. One current example, associated with a high potential to contribute to those demands, is the multi-spectral ESA Sentinel-2 (S2) system. The present study focuses on the evaluation of spectral information content needed for crop leaf area index (LAI) mapping in view of the future sensors. Data from a field campaign were used to determine the optimal spectral sampling from available S2 bands applying inversion of a radiative transfer model (PROSAIL) with look-up table (LUT) and artificial neural network (ANN) approaches. Overall LAI estimation performance of the proposed LUT approach (LUTN₅₀) was comparable in terms of retrieval performances with a tested and approved ANN method. Employing seven- and eight-band combinations, the LUTN₅₀ approach obtained LAI RMSE of 0.53 and normalized LAI RMSE of 0.12, which was comparable to the results of the ANN. However, the LUTN50 method showed a higher robustness and insensitivity to different band settings. Most frequently selected wavebands were located in near infrared and red edge spectral regions. In conclusion, our results emphasize the potential benefits of the Sentinel-2 mission for agricultural applications

Measurement of spontaneous emission from a two-dimensional photonic band gap defined microcavity at near-infrared wavelengths

An active, photonic band gap-based microcavity emitter in the near infrared is demonstrated. We present direct measurement of the spontaneous emission power and spectrum from a microcavity formed using a two-dimensional photonic band gap structure in a half wavelength thick slab waveguide. The appearance of cavity resonance peaks in the spectrum correspond to the photonic band gap energy. For detuned band gaps, no resonances are observed. For devices with correctly tuned band gaps, a two-time enhancement of the extraction efficiency was demonstrated compared to detuned band gaps and unpatterned material

RGB-D based framework to Acquire, Visualize and Measure the Human Body for Dietetic Treatments

This research aims to improve dietetic-nutritional treatment using state-of-the-art RGB-D sensors and virtual reality (VR) technology. Recent studies show that adherence to treatment can be improved using multimedia technologies. However, there are few studies using 3D data and VR technologies for this purpose. On the other hand, obtaining 3D measurements of the human body and analyzing them over time (4D) in patients undergoing dietary treatment is a challenging field. The main contribution of the work is to provide a framework to study the effect of 4D body model visualization on adherence to obesity treatment. The system can obtain a complete 3D model of a body using low-cost technology, allowing future straightforward transference with sufficient accuracy and realistic visualization, enabling the analysis of the evolution (4D) of the shape during the treatment of obesity. The 3D body models will be used for studying the effect of visualization on adherence to obesity treatment using 2D and VR devices. Moreover, we will use the acquired 3D models to obtain measurements of the body. An analysis of the accuracy of the proposed methods for obtaining measurements with both synthetic and real objects has been carried out

The Central Laser Facility at the Pierre Auger Observatory

The Central Laser Facility is located near the middle of the Pierre Auger Observatory in Argentina. It features a UV laser and optics that direct a beam of calibrated pulsed light into the sky. Light scattered from this beam produces tracks in the Auger optical detectors which normally record nitrogen fluorescence tracks from cosmic ray air showers. The Central Laser Facility provides a "test beam" to investigate properties of the atmosphere and the fluorescence detectors. The laser can send light via optical fiber simultaneously to the nearest surface detector tank for hybrid timing analyses. We describe the facility and show some examples of its many uses.Comment: 4 pages, 5 figures, submitted to 29th ICRC Pune Indi

The dire disregard of measurement invariance testing in psychological science

In psychological science, self-report scales are widely used to compare means in targeted latent constructs across time points, groups, or experimental conditions. For these scale mean comparisons (SMC) to be meaningful and unbiased, the scales should be measurement invariant across the compared time points or (experimental) groups. Measurement invariance (MI) testing checks whether the latent constructs are measured equivalently across groups or time points. Since MI is essential for meaningful comparisons, we conducted a systematic review to check whether MI is taken seriously in psychological research. Specifically, we sampled 426 psychology articles with openly available data that involved a total of 918 SMCs to (1) investigate common practices in conducting and reporting of MI testing, (2) check whether reported MI test results can be reproduced, and (3) conduct MI tests for the SMCs that enabled sufficiently powerful MI testing with the shared data. Our results indicate that (1) 4% of the 918 scales underwent MI testing across groups or time and that these tests were generally poorly reported, (2) none of the reported MI tests could be successfully reproduced, and (3) of 161 newly performed MI tests, a mere 46 (29%) reached sufficient MI (scalar invariance), and MI often failed completely (89; 55%). Thus, MI tests were rarely done and poorly reported in psychological studies, and the frequent violations of MI indicate that reported group differences cannot be solely attributed to group differences in the latent constructs. We offer recommendations on reporting MI tests and improving computational reproducibility practices

Tebaldo Jorge Ricaldoni: ¿inventor o científico?

A fines del siglo XIX era reconocido en Argentina como sabio y maestro, inventor de un receptor de telegrafía sin hilos que se habría anticipado a Marconi, creador de un proyecto de submarino revolucionario que hubiera sido pionero en el mundo. Enrolado en el positivismo y allegado a la alta sociedad porteña, el ingeniero uruguayo Tebaldo Ricaldoni fue elegido por Joaquín V. González para crear el Instituto de Física de la naciente Universidad Nacional de La Plata. Después de una breve y conflictiva gestión, Ricaldoni fue desplazado por la contratación de científicos alemanes, que convirtieron el Instituto de Física en un centro científico al estilo europeo. A partir de entonces él se dedicó al dictado de clases en la UNLP y el Colegio Nacional de Buenos Aires, y al trabajo en su taller particular, con fondos propios y aporte privado. Publicó veinticinco libros de texto y desarrolló numerosos inventos, entre los que se destacan el submarino, un receptor de telegrafía sin hilos, un reductor de voltaje, una boya de salvataje, un panoramoscopio y un desvía torpedos. La trayectoria de Ricaldoni bien merece un lugar entre los que hicieron la historia de la ciencia en el río de La Plata.Museo de Físic

Cross-correlation image analysis for real-time particle tracking

Accurately measuring translations between images is essential in many fields, including biology, medicine, geography, and physics. Existing methods, including the popular FFT-based cross-correlation, are not suitable for real-time analysis, which is especially vital in feedback control systems. To fill this gap, we introduce a new algorithm which approaches shot-noise limited displacement detection and a GPU-based implementation for real-time image analysis.Comment: 4 pages, 3 figures, submitted to Optics Letter