A Study of Asian Dust Events Using Surface, Satellite, and Aircraft Measurements During Intex-B

Asian dust events occur frequently during the northern hemisphere spring season. Some of these events can transport dust downwind to North America within 7 days’ time and turn a regional impact into one of a much larger scale. To further quantify the transpacific transport and evolution of Asian dust to North America and assess the impact on regional climate, NASA led a field experiment called the Intercontinental Chemical Transport Experiment - Phase B (INTEX-B) during April-May 2006 over the eastern Pacific Ocean. This study documents the physical and optical properties of Asian dust, as well as its strength and evolution from its source near the Gobi desert to its sink in North America, during INTEX-B using surface, satellite and DC-8 aircraft measurements. A total of 11 dust events have been identified and summarized. Two dust events, originating from the Gobi desert on 7 and 17 April 2006, have been extensively analyzed, and their trajectories, strength and evolution have been tracked. For the strong Asian dust episode on 17 April 2006, the observed total downwelling shortwave (SW) flux over Xianghe, a site near Beijing, is only 46% of the clear-sky value with almost no direct transmission, and nearly double the diffuse SW clear-sky value. The surface averaged aerosol optical depth (AOD) increased from 0.17 (clear-sky) to 4.0, and the Angstrom exponent (AE) dropped from 1.26 (clear-sky) to below 0.1. This event was also captured by satellite and the UND/NASA DC-8 over the eastern Pacific Ocean from 23-24 April 2006. By this time, its strength degraded due to dispersion and larger particles settling out. The DC-8 observed this dust plume with higher averaged aerosol scattering ratios of 10.5 at 1064 nm and 2.0 at 588 nm and a depolarization of 25%. The DC-8 nephelometer also observed this dust event in-situ and confirmed that the highest scattering coefficient ranged from 80-100 mm\u271. When this dust transported to North America, its AOD values decreased from a mean of 2.0 over the source region to 0.2 over North America

Measurement of the Temperature Dependence of the Casimir-Polder Force

We report on the first measurement of a temperature dependence of the Casimir-Polder force. This measurement was obtained by positioning a nearly pure 87-Rb Bose-Einstein condensate a few microns from a dielectric substrate and exciting its dipole oscillation. Changes in the collective oscillation frequency of the magnetically trapped atoms result from spatial variations in the surface-atom force. In our experiment, the dielectric substrate is heated up to 605 K, while the surrounding environment is kept near room temperature (310 K). The effect of the Casimir-Polder force is measured to be nearly 3 times larger for a 605 K substrate than for a room-temperature substrate, showing a clear temperature dependence in agreement with theory.Comment: 4 pages, 4 figures, published in Physical Review Letter

Stagnate summers : climate induced changes in physical mixing parameters in Missouri reservoirs

Lakes and reservoirs are important environmental sentinels for climate change. As air temperatures rise so do the temperatures of these water bodies affecting their physical, chemical, and biological properties. Being used for drinking water supplies, fisheries, and human recreation, these long term potential changes can be an important factor for their use. Climate change has been associated with altering physical reservoir parameters, such as mixing depth, water temperatures, and water chemistry. Using a historical dataset to find both break points and monotonic trends that may indicate climate having influenced our reservoirs we found little in terms of monotonic trends. However, we did witness changes in all systems in regards to break points for almost every parameter. Our systems cannot directly correlate to having had climate change based effects, as we can neither support or refute its evidence in our reservoirs as changes relating to climate do not only impact physical parameters but also animal and plant communities, and social factors such as use (influenced by cyanobacteria blooms). It is even plausible that increased in reservoir production and turbidity could lead to shifts in physical trends that would otherwise be different in non-affected reservoirs. Over all more information is needed to create a better picture of exactly how climate change is impacting the physical mixing parameters in Missouri reservoirs as they are complex and varied systems.Cody Kimbell, John R. Jones, Daniel Obrecht, and Rebecca North (University of Missouri, Columbia

Automatic extraction of prosodic features for automatic language identification

The aim of this study is to propose a new approach to Automatic Language Identification: it is based on rhythmic modelling and fundamental frequency modelling and does not require any hand labelled data. First we need to investigate how prosodic or rhythmic information can be taken into account for Automatic Language Identification. A new automatically extracted unit, the pseudo syllable, is introduced. Rhythmic and intonative features are then automatically extracted from this unit. Elementary decision modules are defined with gaussian mixture models. These prosodic modellings are combined with a more classical approach, a vocalic system acoustic modelling. Experiments are conducted on the five European languages of the MULTEXT corpus: English, French, German, Italian and Spanish. The relevance of the rhythmic parameters and the efficiency of each system (rhythmic model, fundamental frequency model and vowel system model) are evaluated. The influence of these approaches on the performances of automatic language identification system is addressed. We obtain 91 % of correct identification with 21 s. utterances using all the information sources.Le but de cette étude est de proposer une nouvelle approche pour l’identification automatique des langues, basée sur une modélisation du rythme, ne nécessitant pas de données étiquetées manuellement. Il faut tout d’abord savoir comment apporter des informations sur la prosodie, le rythme pour l’identification automatique des langues. Pour répondre à cette question nous avons introduit une nouvelle unité, la pseudo-syllabe, qui est automatiquement extraite. Des paramètres rythmiques et intonatifs sont alors calculés à partir de cette unité. Des modèles élémentaires pour chaque type de paramètres sont définis en utilisant des mélanges de lois gaussiennes. Ces modélisations de la prosodie sont couplées à une approche plus classique utilisant une modélisation acoustique des systèmes vocaliques. Les expériences sont menées sur les cinq langues européennes du corpus MULTEXT. L’intérêt des paramètres rythmiques, et l’efficacité de chaque système (modèle rythmique, modèle de la fréquence fondamentale et modèle vocalique) sont évalués. L’impact de ces approches sur les performances d’identification est analysé. Nous obtenons des résultats de 91% d’identification correcte avec des fichiers de 21 secondes

Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror

We present experimental results showing the diffuse reflection of a Bose-Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions.Comment: submitted to J Phys B, 10 pages, 6 figure

A trapped-ion local field probe

We introduce a measurement scheme that utilizes a single ion as a local field probe. The ion is confined in a segmented Paul trap and shuttled around to reach different probing sites. By the use of a single atom probe, it becomes possible characterizing fields with spatial resolution of a few nm within an extensive region of millimeters. We demonstrate the scheme by accurately investigating the electric fields providing the confinement for the ion. For this we present all theoretical and practical methods necessary to generate these potentials. We find sub-percent agreement between measured and calculated electric field values

Interparticle interactions:Energy potentials, energy transfer, and nanoscale mechanical motion in response to optical radiation

In the interactions between particles of material with slightly different electronic levels, unusually large shifts in the pair potential can result from photoexcitation, and on subsequent electronic excitation transfer. To elicit these phenomena, it is necessary to understand the fundamental differences between a variety of optical properties deriving from dispersion interactions, and processes such as resonance energy transfer that occur under laser irradiance. This helps dispel some confusion in the recent literature. By developing and interpreting the theory at a deeper level, one can anticipate that in suitable systems, light absorption and energy transfer will be accompanied by significant displacements in interparticle separation, leading to nanoscale mechanical motion

Hierarchical Hidden Markov Model in Detecting Activities of Daily Living in Wearable Videos for Studies of Dementia

International audienceThis paper presents a method for indexing activities of daily living in videos obtained from wearable cameras. In the context of dementia diagnosis by doctors, the videos are recorded at patients' houses and later visualized by the medical practitioners. The videos may last up to two hours, therefore a tool for an efficient navigation in terms of activities of interest is crucial for the doctors. The specific recording mode provides video data which are really difficult, being a single sequence shot where strong motion and sharp lighting changes often appear. Our work introduces an automatic motion based segmentation of the video and a video structuring approach in terms of activities by a hierarchical two-level Hidden Markov Model. We define our description space over motion and visual characteristics of video and audio channels. Experiments on real data obtained from the recording at home of several patients show the difficulty of the task and the promising results of our approach

Observation of the thermal Casimir force

Quantum theory predicts the existence of the Casimir force between macroscopic bodies, due to the zero-point energy of electromagnetic field modes around them. This quantum fluctuation-induced force has been experimentally observed for metallic and semiconducting bodies, although the measurements to date have been unable to clearly settle the question of the correct low-frequency form of the dielectric constant dispersion (the Drude model or the plasma model) to be used for calculating the Casimir forces. At finite temperature a thermal Casimir force, due to thermal, rather than quantum, fluctuations of the electromagnetic field, has been theoretically predicted long ago. Here we report the experimental observation of the thermal Casimir force between two gold plates. We measured the attractive force between a flat and a spherical plate for separations between 0.7 $\mu$m and 7 $\mu$m. An electrostatic force caused by potential patches on the plates' surfaces is included in the analysis. The experimental results are in excellent agreement (reduced $\chi^2$ of 1.04) with the Casimir force calculated using the Drude model, including the T=300 K thermal force, which dominates over the quantum fluctuation-induced force at separations greater than 3 $\mu$m. The plasma model result is excluded in the measured separation range.Comment: 6 page

Casimir force on amplifying bodies

Based on a unified approach to macroscopic QED that allows for the inclusion of amplification in a limited space and frequency range, we study the Casimir force as a Lorentz force on an arbitrary partially amplifying system of linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate that the force on a weakly polarisable/magnetisable amplifying object in the presence of a purely absorbing environment can be expressed as a sum over the Casimir--Polder forces on the excited atoms inside the body. As an example, the resonant force between a plate consisting of a dilute gas of excited atoms and a perfect mirror is calculated