No description available.

L’expérience I.C.E a pour objectif de tester le principe d’équivalence faible (WEP) à la base de la théorie de la relativité générale d’Einstein et postulant l’équivalence entre masse inertielle et masse grave. Si ce principe a toujours été vérifié jusqu’à aujourd’hui, il est d’un intérêt fondamental pour la physique moderne de poursuivre les mesures avec une précision accrue. En effet, de nouvelles théories d’unification de la mécanique quantique et de la relativité générale prévoient une violation de ce principe. Pour réaliser un test du WEP, il suffit de comparer les accélérations de deux objets en chute libre dans un même champ de gravitation, et c’est ce que réalise l’expérience I.C.E à l’échelle quantique (à la différence de la mission spatiale Microscope qui à ce jour a pu vérifier le WEP avec des objets macroscopiques avec une sensibilité sur le paramètre de 2.10−14). Ainsi, l’expérience consiste à réaliser, par une méthode interférométrique, la mesure de l’accélération de deux espèces atomiques (87Rb et 39K) de masses et de compositions différentes, en chute libre dans une enceinte à vide. La sensibilité de la mesure des effets inertiels auxquels les atomes sont sensibles (accélérations et rotations) est d’autant plus grande que la durée de chute libre des atomes est élevée et que la température des nuages est faible. Or, sur Terre au laboratoire, les atomes finissent par tomber au fond de l’enceinte les contenant sous l’effet de la gravité, ce qui limite grandement la sensibilité de la mesure. C’est pourquoi il est intéressant de placer l’expérience dans un environnement de micropesanteur dans lequel les atomes restent au centre de la chambre à vide afin d’atteindre des temps d’interrogation beaucoup plus longs. A ce titre, l’expérience est embarquée jusqu’à plusieurs fois par an, à bord de l’avion Zéro-g de la société Novespace. Les durées de micropesanteur proposées permettent d’atteindre des temps d’interrogation théoriques de l’ordre de la seconde ce qui doit porter le niveau de sensibilité à 10−11. Cependant, nous sommes aujourd’hui très fortement limités par le niveau élevé de vibrations et de rotations de l’avion : la perte de contraste des franges d’interférence engendrée ainsi que le bruit de phase introduit, ne nous permettent pas de dépasser des temps d’interrogation de 5 ms en 0 g. En parallèle, le laboratoire s’est récemment doté d’un simulateur de microgravité sur lequel est montée l’expérience, donnant accès à des temps d’interrogation de plus de 200 ms avec des trajectoires paraboliques d’une très bonne répétabilité (de l’ordre de 3 mg). La cohérence d’une source atomique étant directement reliée à sa température, l’utilisation de nuages ultra-froids est d’un grand intérêt pour améliorer le contraste des franges d’interférence, d’autant plus pour les longs temps d’interrogation visés. Le présent manuscrit synthétise les travaux ayant permis de produire le tout premier condensat de Bose-Einstein (la source atomique ultime) de 87Rb en microgravité par une méthode tout optique, et ce, de manière répétable toutes les 13,5 secondes. Nous démontrons l’efficacité de note méthode de chargement du piège dipolaire basée sur l’association d’un refroidissement par mélasse grise et d’une modulation spatiale des faisceaux dipolaires. Ces résultats ouvrent la voie vers de futures mesures interférométriques très sensibles à grand facteur d’échelle. / The I.C.E experiment aims at testing the weak equivalence principle (WEP) underlying Einstein’s theory of general relativity and which postulates the equivalence between inertial mass and gravitationnal mass. If this principle has always been verified until today, it is of fundamental interest for physics to continue the measurements with greater precision. Indeed, new unifying theories of quantum mechanics and general relativity predict a violation of this principle. To carry out a test of the WEP, it suffices to compare the accelerations of two objects in free fall in the same gravitationnal field. This is what the I.C.E experiment, on the quantum scale, achieves (unlike the spatial Microscope mission, which to date has been able to verify the principle of equivalence with macroscopic objects with a sensitivity on of 2.10−14). Thus, the experiment consists in performing, by an interferometric method, the measurement of the acceleration of two atomic species (87Rb and 39K) of different mass and composition in free fall in a vacuum chamber. The measurement sensitivity of the inertial effects to which the atoms are sensitive (accelerations and rotations) is all the greater as the free fall time of the atoms is high and their temperature is low. But on Earth, in the laboratory, the atoms eventually fall to the bottom of the vacuum chamber containing them under the effect of gravity, which greatly limits the measurement sensitivity achievable. This is why it is interesting to place the experiment in a microgravity environment in which the atoms stay in the center of the vacuum chamber in order to reach much longer interrogation times. As such, several times a year, the experiment is put aboard the aircraft Zero-g of the Novespace company. The available microgravity durations make it possible to reach theoretical interrogation times of the order of one second, which should raise the sensitivity level to 10−11. However, we are today very strongly limited by the high level of vibrations of the aircraft as well as its rotations : the loss of contrast of the interference fringes and the phase noise caused, do not allow us to exceed 5 ms of interrogation times in 0 g. Since the coherence of an atomic source is directly related to its temperature, the use of ultra-cold clouds is of great interest to improve the contrast of the interference fringes, especially for the long interrogation times targeted. In parallel, the laboratory is now equipped with a microgravity simulator on which is mounted the experiment, giving access to interrogation times of more than 250 ms with parabolic trajectories of a very good repeatability (of the order of 3 mg). This manuscript synthesizes the work that produced the very first 87Rb Bose-Einstein condensate in microgravity by all-optical methods, with a repetition rate of 13,5 seconds. We demonstrate the efficiency of our dipole trap loading method based on the association of a grey molasses cooling and a spatial modulation of the dipole beams. These results pave the way for future highly sensitive interferometric measurements with a large scale factor.

UHF bands because more penetration can be achieved at low frequencies. Consequently, large antennas are required, which limits their use for small airborne applications. This thesis explores various GPR antenna designs for a bi-static system that are at least operational from 225 MHz to 255 MHz and suitable for small airborne applications. The 3D electromagnetic simulation software Ansys high-frequency structure simulator (HFSS) was used to simulate various sizes of strip dipole, triangular bowtie, half elliptical bowtie, and elliptical bowtie antennas. Several physical models were constructed to validate the return loss simulation results. Additionally, simulation data is included for a wire dipole and a helical antenna. The helical antenna proved to be too large for small airborne application, so focus was placed on the dipole and bowtie designs. The performance of the dipole and bowtie antenna models are compared by size, weight, return loss (𝑆11), peak gain, and the transmit-to-receive isolation. Out of the fourteen simulated models, twelve meet the bandwidth requirement with an average weight of 0.23 lbs. It is found that the strip dipole exhibited wider bandwidth characteristics than the triangular, elliptical, and half elliptical bowtie models, while maintaining similar weight and size. The smallest strip dipole model is 50 mm x 528 mm x 1 mm, weighs 0.17 lbs, and is operational from 225 MHz to 283 MHz. Two strip dipole test antennas were fabricated and tested. Test results confirm the simulation predictions.

No description available.

Three-dimensional linear ray theory is used to investigate internal waves interacting with a Lamb-Chaplygin pancake vortex dipole. These interactions involve waves propagating in the same (co-propagating) and opposite (counter-propagating) horizontal directions as the dipole translation. Co-propagating internal waves in the vertical symmetry plane between the vortices of the dipole can approach critical levels where the wave energy is absorbed by the dipole or where the waves are overturned and possibly break. As wave breaking cannot be simulated with this linear model, changes in wave steepness are calculated to aid in estimating the onset of breaking. Counter-propagating internal waves in the vertical symmetry plane can experience horizontal and vertical reflections, including turning points similar to waves in two-dimensional steady shear. Wave capture is also a possible effect of either type of interaction, depending on initial wave properties and positioning relative to the vortex dipole. Away from the vertical symmetry plane, a spanwise converging (focusing) and diverging (defocusing) of wave energy is observed in co- and counter-propagating interactions as symmetric off-center rays interact with the dipole's individual vortices. Some off-center rays experience multiple horizontal refractions similar to wave trapping.

The mismatch negativity (MMN) is a specific event-related potential (ERP) component used frequently in the observation of auditory processing. The MMN is elicited by a deviant stimulus randomly presented in the presence of repeating stimuli. The current study utilized the MMN response in order to determine the temporal (timing) and linguistic processing of natural and synthetic vowel stimuli. It was hypothesized that a significant MMN response would be elicited by natural and synthetic vowel stimuli. Brain mapping of the MMN response was hypothesized to yield temporal resolution information, which would provide detail regarding the sequential processing differences between natural and synthetic vowel stimuli. It was also hypothesized that the location of dipoles within the cortex would provide information pertaining to differences in cortical localization of processing for natural and synthetic stimuli. Vowel stimuli were presented to twenty participants (10 females and 10 males between the ages of 18 and 26 years) in a three-forced-choice response paradigm. Data from behavioral responses, reaction times, and ERPs were recorded for each participant. Results demonstrated that there were differences in the behavioral and electrophysiological responses between natural and synthesized vowels presented to young, normal hearing adults. In addition, significant MMN responses were evoked by both natural and synthetic vowel stimuli. Greater reaction times existed for the synthetic vowel phonemes compared to the natural vowel phonemes. Electrophysiological differences were primarily seen in the processing of the synthetic /u/ stimuli. Scalp distribution of cognitive processing was essentially the same for naturally produced phonemes. Processing of synthetic phonemes also had similar scalp distributions; however, the synthetic /u/ phoneme required more complex processing compared to the synthetic /æ/ phoneme. The most significant processing localizations were located in the superior temporal gyrus, which is known for its role in linguistic processing. Continued processing in the frontal lobe was observed, suggesting continual evaluation of natural and synthetic phonemes throughout processing.

No description available.

<p>Utilizing a genetic algorithm training of the atom dipole interaction model was performed to arrive at C,H, N, & O atomic polarizabilities that constitute a correction to semiempirical molecular polarizability calculations increasing the accuracy of these calculations to near parity with DFT at a fraction of the computational load.</p>

Indiana University-Purdue University Indianapolis (IUPUI) / Molecular polarizability plays a significant role in chemistry, biology, and medicine. Classical prediction of polarizability often relies on atomic-type specific polarizability optimized for training set molecules, which limits the calculations to systems of similar chemical environment. Although ab initio (AI) quantum mechanical (QM) methods are more transferable in predicting molecular polarizability, their high computational costs especially when used with large basis sets for obtaining quantitatively reliable results make them less practical. To obtain accurate QM polarizability in an efficient manner, we have developed a dual-level approach, where the polarizability (α) obtained from the efficient semiempirical QM (SE) method is corrected using a set of element-base atomic polarizabilities derived from the atomic dipole interaction model (ADIM) to reproduce the density functional theory (DFT) results. We have optimized the atomic polarizability correction parameters for CHON-containing systems using a small training set of molecules and tested the resulting SE-ADIM model on the neutral drug-like molecules in the QM7B database. SE-ADIM corrected AM1 showed substantial improvement with its relative percent error (RPE) compared to B3LYP reduced from 33.81% to 3.35%. To further test its robustness for larger molecules in broader chemical bonding situations, we applied this method to a collection of drug molecules from the e-Drug3D database. For the 1004 molecules tested, our SE-ADIM model, which only contains four empirical parameters, greatly reduces the RPE in AM1 polarizability relative to B3LYP from 26.8% to 2.9%. Error decomposition shows consistent improvements across molecules with diverse bond saturations, molecular sizes, and charge states. In addition, we have applied AlphaML, a promising machine learning (ML) technique for predicting molecular polarizability, to the e-Drug3D dataset to compare its performance with our SE-ADIM correction of AM1. We found SE-ADIM performs competitively with AlphaML bolstering our confidence in the value of our method. Errors distinct to AlphaML were also discovered. We found four molecules for which AlphaML predicts negative molecular polarizabilities, all of which were peroxides. In contrast, SE-ADIM has no such issue with these molecules or this chemical type. Finally, to improve performance of SE-ADIM when correcting AM1 molecular polarizability calculations for charged molecules, we introduce a charge dependent polarizability (CDP) enabled SE-ADIM. Training the CDP enabled SE-ADIM with a single additional parameter, B, we were able to reduce error in AM1 molecular polarizability calculations of charged molecules relative to B3LYP from 29.57% to 5.16%. By contrast, SE-ADIM without CDP corrected AM1 relative to B3LYP had an RPE of 8.56%. The most benefit of CDP was evident within negatively charged molecules where AM1 error relative to B3LYP fell from 32.20% to 3.77% while SE-ADIM without CDP enabled error for these same negative molecules was 10.06%.

Metallic films, in conjunction with biochemical-targeted probes, are expected to provide early diagnosis, targeted therapy and non-invasive monitoring for epidemiology applications [1-4]. The resonance wavelength peaks, both plasmonic and Wood-Rayleigh Anomalies (WRAs), in the scattering spectra are affected by the metallic architecture. As of today, much research has been devoted to extinction efficiency in the plasmonic region. However, Wood Rayleigh Anomalies (WRAs) typically occur at wavelengths associated with the periodic distance of the structures. A significant number of papers have already focused on the plasmonic region of the visible spectrum, but a less explored area of research was presented here; the desired resonance wavelength region was 400-500nm, corresponding to the WRA for the silver film with perforated hole with a periodic distance of 400nm. Simulations obtained from the discrete dipole approximation (DDA) method, show sharp spectral bands (either high or low scattering efficiencies) in both wavelength regions of the visible spectrum simulated from Ag film with cylindrical hole arrays. In addition, surprising results were obtained in the parallel scattering spectra, where the electric field is contained in the XY plane, when the angle between the metallic surface and the incident light was adjusted to 14 degrees; a bathochromic shift was observed for the WRA peak suggesting a hybrid resonance mode. Metallic films have the potential to be used in instrumental techniques for use as sensors, i.e. surface plasmon resonance affinity biosensors, but are not limited to such instrumental techniques. Although the research here was aimed towards affinity biosensors, other sensory designs can benefit from the optimized Ag film motifs. The intent of the study was to elucidate metal film motifs, when incorporated into instrumental analysis, allowing the quantification of genetic material in the visible region. Any research group that routinely benefits from quantification of various analytes in solution matrices will also benefit from this study, as there are a bewildering number of instrumental sensory methods and setups available.