What Kind of Scientist Are You? Science and Interdisciplinary Research

Scientific research that crosses disciplinary boundaries (“interdisciplinary research”) – and in particular, research that crosses academic boundaries to engage with industry, government and non-government agencies, and the broader public – can be rewarding personally and yield novel approaches and findings. While the scholarly literature suggests that interdisciplinary approaches are of immense value, interdisciplinary research carries challenges to academics, particularly in terms of funding and in relation to finding an academic “home.” In this article, the author outlines what is meant by interdisciplinary research and reflects on her career leading from graduate school to tenure. She illustrates how the interdisciplinary projects she has been involved in have been both rewarding and challenging. While not every scientist must be interdisciplinary, she concludes that being open to such an approach has many advantages.La recherche scientifique qui dépasse les frontières disciplinaires (la recherche « interdisciplinaire ») —et, particulièrement, celle qui dépasse les frontières académiques pour s’engager avec l’industrie, les agences gouvernementales et nongouvernementales et le public—peuvent être personnellement enrichissantes et engendrer de nouvelles approches et résultats. Même si la littérature académique indique que les approches interdisciplinaires ont beaucoup de mérite, la recherche interdisciplinaire pose des défis aux universitaires, notamment par rapport à l’obtention de subventions et la possibilité de trouver un chez-soi académique. Dans cet article, l’auteure décrit ce que l’on entend par recherche interdisciplinaire et réfléchit sur son propre parcours, des études supérieures à la titularisation. Elle montre ainsi comment les projets interdisciplinaires auxquels elle a participé ont été à la fois enrichissants et stimulants pour elle. Elle conclut que, bien que chaque savant ne doive pas être interdisciplinaire, être ouvert à une telle approche a plusieurs avantages

A universal ionization threshold for strongly driven Rydberg states

We observe a universal ionization threshold for microwave driven one-electron Rydberg states of H, Li, Na, and Rb, in an {\em ab initio} numerical treatment without adjustable parameters. This sheds new light on old experimental data, and widens the scene for Anderson localization in light matter interaction.Comment: 4 pages, 1 figur

A new chiral electro-optic effect: Sum-frequency generation from optically active liquids in the presence of a dc electric field

We report the observation of sum-frequency signals that depend linearly on an applied electrostatic field and that change sign with the handedness of an optically active solution. This recently predicted chiral electro-optic effect exists in the electric-dipole approximation. The static electric field gives rise to an electric-field-induced sum-frequency signal (an achiral third-order process) that interferes with the chirality-specific sum-frequency at second-order. The cross-terms linear in the electrostatic field constitute the effect and may be used to determine the absolute sign of second- and third-order nonlinear optical susceptibilities in isotropic media.Comment: Submitted to Physical Revie

Ultrasonographic features of children presenting with abdominal pain : normal versus abnormal

This thesis describes five ultrasonogaphic studies in children with abdominal pain. The normal appendix can be visualized by ultrasound in 82% of the children without abdominal complaints, according to the first study. In cases of non-depiction of the appendix in children with a clinical suspicion of appendicitis, the ultrasonographic presence of secondary signs of appendicitis is a strong indicator of this diagnosis. In the absence of these ultrasonographic signs acute appendicitis can be ruled out. The third study shows that increased renal cortex echogenicity in children with acute illness is a transient feature and does not necessarily indicate renal disease. It should alert the radiologist to search the abdomen more thoroughly for a cause of the acute illness, such as appendicitis. The fourth study showed that ultrasonography can differentiate between ileoileal and ileocolic intussusceptions. The diameter and the length of the intussusception are the main criteria. Finally, the last study shows no relation between enlarged mesenteric lymph nodes and parasitic intestinal infections in children with recurrent abdominal pain. In addition, this study shows organic abnormalities in less than 5% of the children with recurrent abdominal pain at ultrasound.Guerbet Nederland B.V., Toshiba Medical Systems Nederland B.V., MEDRAD B.V., Leuwico Nederland B.V., Foundation Imago OegstgeestUBL - phd migration 201

Light scattering from an amplifying medium bounded by a randomly rough surface: A numerical study

We study by numerical simulations the scattering of $s$-polarized light from a rough dielectric film deposited on the planar surface of a semi-infinite perfect conductor. The dielectric film is allowed to be either active or passive, situations that we model by assigning negative and positive values, respectively, to the imaginary part $\epsilon_2$ of the dielectric constant of the film. We study the reflectance ${\cal R}$ and the total scattered energy ${\cal U}$ for the system as functions of both $\epsilon_2$ and the angle of incidence of the light. Furthermore, the positions and widths of the enhanced backscattering and satellite peaks are discussed. It is found that these peaks become narrower and higher when the amplification of the system is increased, and that their widths scale linearly with $\epsilon_2$. The positions of the backscattering peaks are found to be independent of $\epsilon_2$, while we find a weak dependence on this quantity in the positions of the satellite peaks.Comment: Revtex, 9 pages, 9 figure

Coherent backscattering of light by atoms in the saturated regime

We present the first calculation of coherent backscattering with inelastic scattering by saturated atoms. We consider the scattering of a quasi-monochromatic laser pulse by two distant atoms in free space. By restricting ourselves to scattering of two photons, we employ a perturbative approach, valid up to second order in the incident laser intensity. The backscattering enhancement factor is found to be smaller than two (after excluding single scattering), indicating a loss of coherence between the doubly scattered light emitted by both atoms. Since the undetected photon carries information about the path of the detected photon, the coherence loss can be explained by a which-path argument, in analogy with a double-slit experiment.Comment: 16 pages, 10 figure

Smoothing effect and delocalization of interacting Bose-Einstein condensates in random potentials

We theoretically investigate the physics of interacting Bose-Einstein condensates at equilibrium in a weak (possibly random) potential. We develop a perturbation approach to derive the condensate wavefunction for an amplitude of the potential smaller than the chemical potential of the condensate and for an arbitrary spatial variation scale of the potential. Applying this theory to disordered potentials, we find in particular that, if the healing length is smaller than the correlation length of the disorder, the condensate assumes a delocalized Thomas-Fermi profile. In the opposite situation where the correlation length is smaller than the healing length, we show that the random potential can be significantly smoothed and, in the meanfield regime, the condensate wavefunction can remain delocalized, even for very small correlation lengths of the disorder.Comment: The word "screening" has been changed to "smoothing" to avoid confusions with other effects discussed in the literature. This does not affect the content of paper, nor the results, nor the physical discussio

Determination of the diffusion constant using phase-sensitive measurements

We apply a pulsed-light interferometer to measure both the intensity and the phase of light that is transmitted through a strongly scattering disordered material. From a single set of measurements we obtain the time-resolved intensity, frequency correlations and statistical phase information simultaneously. We compare several independent techniques of measuring the diffusion constant for diffuse propagation of light. By comparing these independent measurements, we obtain experimental proof of the consistency of the diffusion model and corroborate phase statistics theory.Comment: 9 pages, 8 figures, submitted to Phys. Rev.

Hydrated Electron Dynamics at a Five Femtosecond Time Scale

Hydrated electrons are studied by frequency resolved pump probe with 5 fs time resolution in the spectral range from 600 nm to 1000 nm. A recurrence detected in the pumpprobe signal at —40 fs is tentatively assigned to coupling to librational motions in the electron's solvent cage

Propagation inhibition and wave localization in a 2D random liquid medium

Acoustic propagation and scattering in water containing many parallel air-filled cylinders is studied. Two situations are considered and compared: (1) wave propagating through the array of cylinders, imitating a traditional experimental setup, and (2) wave transmitted from a source located inside the ensemble. We show that waves can be blocked from propagation by disorders in the first scenario, but the inhibition does not necessarily imply wave localization. Furthermore, the results reveal the phenomenon of wave localization in a range of frequencies.Comment: Typos in Fiures are correcte