An iterative procedure for differential analysis of gene expression

Microarrays are a popular technology to study genes that are differentially expressed between two conditions. In this Note, we propose an iterative procedure to determine the biggest subset of non-differentially expressed genes. We prove a pseudo Markov relationship that allows practical computations. We obtain explicit expressions for FDR and the level of the proposed test at each step. To cite this article: A. Bar-Hen, S. Robin, C. R. Acad. Sci. Paris, Ser. I 337 (2003).     

Particle production from signature change

We consider the (massless) scalar field on 2-dimensional manifolds whose metric changes signature and which admit a spacelike isometry. Choosing the wave equation so that there will be a conserved Klein-Gordon product implicitly determines the junction conditions one needs to impose in order to obtain global solutions. The resulting mix of positive and negative frequencies produced by the presence of Euclidean regions depends only on the total width of the regions, and not on the detailed form of the metric.This essay received honorable mention in the 1991 competition of the Gravity Research Foundation.     

The maximum degree in a random tree and related problems

Meir and Moon studied the distribution of the maximum degree for simply generated families of trees. We have sharper results for the special case of labelled trees. © 1994 John Wiley & Sons, Inc.     

Measurement and analysis of the ν2 and ν4 infrared bands of 13CD4

A Fourier transform infrared spectrum of 91% ¹³CD₄ has been recorded between 885 and 1193 cm^?1 with a resolution of 0.04 cm^?1. The frequencies of 600 lines were measured with an accuracy of ±0.003 cm^?1. Of these, approximately 368 are assigned as allowed transitions in ν₄, 95 are forbidden ν₄ transitions, and 137 belong to ν₂; maximum upper state J values are 20 for ν₄ and 19 for ν₂. The ground state tensor constants D_t, H_4t, and H_6t were obtained by fitting them to four rotational transitions observed by Kreiner and Opferkuch in the infrared-microwave double-resonance spectrum. An interacting-band analysis of the $\text{ν}{}_2\text{ν}{}_4$ diad then yields 22 spectroscopic constants for these Coriolis-coupled fundamentals and fits the experimental frequencies with an rms deviation of 0.0055 cm^?1 for 432 unblended lines that were assigned unit weight. A ν₄P⁺(12) transition at 943.3812 cm^?1, nearly coincident with the 10P(22) emission of the ¹²C¹⁶O₂ laser, has been investigated by heterodyne spectroscopy and its detuning (?64 MHz) and absorption coefficient have been determined. Such coincidences may lead to the development of laser analytical techniques for ¹³CD₄, which is a useful nonradioactive atmospheric tracer. ¹³CD₄ transitions that are within 300 MHz of isotopic CO₂ laser lines are tabulated for this purpose and for use in double-resonance experiments.     

Current Interruption at Powers up to 1 GW with Crossed-Field Tubes

This paper describes the current interruption and voltage holdoff capabilities of a wide range of crossed-field tubes (XFTs). The XFTs investigated have active electrode areas ranging from 96 to 8000 cm2 with mean diameters from 2 to 56 cm. For the larger XFTs, currents up to 10 kA have been interrupted at voltages up to 100 kV, corresponding to a switched power of 1 GW. Experiments have shown the peak interruptible current to vary linearly with tube radius. The mechanism responsible for the limitation may be related to the self-generated magnetic field, but other factors are also shown to play a role.     

A study of energy transfer between electronically excited states using a picosecond laser pulse

By means of a novel picosecond polarization spectrometer we have determined that under conditions of normal pumping of organic systems a substantial annihilation of excited states occurs before the 6–8 ps duration of the pumping pulse. The effect is exposed by noting that prior to 6 ps the optical absorption of the S₁ transient produced by 353 nm pumping of 1,2-benzanthracene is caused to be depolarized at higher concentrations. In another case (xanthone) where no long range interactions can occur the depolarization of the spectra only occurred at low concentrations due to saturation effects.     

Pediatric Laryngotracheal Stenosis and Airway Reconstruction: A Review of Voice Outcomes, Assessment, and Treatment Issues

Laryngotracheal stenosis is defined as a congenital or acquired narrowing of the airway. Congenital causes may include subglottic membranous or cartilaginous narrowing. Acquired causes may include trauma due to prolonged endotracheal or tracheal intubation or laryngotracheal injury. Although advances have been made over the past 30 years in reconstructive surgeries to improve airway patency in these patients, long-term laryngeal function for voice production is not well defined in this population. This review examines causes, symptoms and signs, and methods for diagnosing laryngotracheal stenosis. Surgical management procedures are briefly summarized. The current literature on voice outcomes is summarized. The predominant voice characteristics in the population are presented, although results are challenged by the heterogeneity of voice presentation and paucity of data from instrumental measures. Considerations for subjective and instrumental assessment, measures of quality of life, instrumental methods, and treatment options specific to the needs of this population are discussed. Research strategies to identify long-term outcomes of surgical and behavioral treatments in this population are posed.     

Quantitative measurements of acoustic emissions from cavitation at the surface of a stone in response to a lithotripter shock wave

Measurements are presented of acoustic emissions from cavitation collapses on the surface of a synthetic kidney stone in response to shock waves (SWs) from an electrohydraulic lithotripter. A fiber optic probe hydrophone was used for pressure measurements, and passive cavitation detection was used to identify acoustic emissions from bubble collapse. At a lithotripter charging voltage of 20 kV, the focused SW incident on the stone surface resulted in a peak pressure of 43 +/- 6 MPa compared to 23 +/- 4 MPa in the free field. The focused SW incident upon the stone appeared to be enhanced due to the acoustic emissions from the forced cavitation collapse of the preexisting bubbles. The peak pressure of the acoustic emission from a bubble collapse was 34 +/- 15 MPa, that is, the same magnitude as the SWs incident on the stone. These data indicate that stresses induced by focused SWs and cavitation collapses are similar in magnitude thus likely play a similar role in stone fragmentation.     

Sample-specific diamagnetic and paramagnetic passive shimming

When homogenizing the static magnetic field over extended in vivo volumes, significant residual inhomogeneity can remain after spherical harmonic shim optimization. This is due to the low spatial orders of shims available on in vivo MR systems and the presence of higher-order inhomogeneity in the vicinity of anatomic air cavities. Mediation of this problem through the development of higher-order spherical harmonic shims is severely impeded by bore space limitations. Sample-specific passive shims are not limited to low-order spatial compensation and offer an alternative means to increased homogenization. Here, we present a novel construction protocol for sample-specific passive shims comprised of both diamagnetic (bismuth) and paramagnetic (zirconium) materials. A prototype shim is constructed and shown to significantly homogenize the mouse brain at 9.4 T. Further homogenization capabilities are simulated through alteration of the shim construction.