Fiber-diffraction Interferometer using Coherent Fiber Optic Taper

We present a fiber-diffraction interferometer using a coherent fiber optic taper for optical testing in an uncontrolled environment. We use a coherent fiber optic taper and a single-mode fiber having thermally-expanded core. Part of the measurement wave coming from a test target is condensed through a fiber optic taper and spatially filtered from a single-mode fiber to be reference wave. Vibration of the cavity between the target and the interferometer probe is common to both reference and measurement waves, thus the interference fringe is stabilized in an optical way. Generation of the reference wave is stable even with the target movement. Focus shift of the input measurement wave is desensitized by a coherent fiber optic taper

Measurements of Surface Diffusivity and Coarsening During Pulsed Laser Deposition

Pulsed Laser Deposition (PLD) of homoepitaxial SrTiO3 was studied with in-situ x-ray specular reflectivity and surface diffuse x-ray scattering. Unlike prior reflectivity-based studies, these measurements access both the time- and the length-scales of the evolution of the surface morphology during growth. In particular, we show that this technique allows direct measurements of the diffusivity for both inter- and intra-layer transport. Our results explicitly limit the possible role of island break-up, demonstrate the key roles played by nucleation and coarsening in PLD, and place an upper bound on the Ehrlich-Schwoebel (ES) barrier for downhill diffusion

X-ray scattering from surfaces: discrete and continuous components of roughness

Incoherent surface scattering yields a statistical description of the surface, due to the ensemble averaging over many independently sampled volumes. Depending on the state of the surface and direction of the scattering vector relative to the surface normal, the height distribution is discrete, continuous, or a combination of the two. We present a treatment for the influence of multimodal surface height distributions on Crystal Truncation Rod scattering. The effects of a multimodal height distribution are especially evident during in situ monitoring of layer-by-layer thin-film growth via Pulsed Laser Deposition. We model the total height distribution as a convolution of discrete and continuous components, resulting in a broadly applicable parameterization of surface roughness which can be applied to other scattering probes, such as electrons and neutrons. Convolution of such distributions could potentially be applied to interface or chemical scattering. Here we find that this analysis describes accurately our experimental studies of SrTiO3 annealing and homoepitaxial growth.Comment: 15 pages, 7 figure

The impact of clinical clerkships on medical students’ attitudes toward contraception and abortion: a pilot study

Objective: Investigate the impact of clinical clerkships on medical students’ attitudes toward contraception and abortion. Methods: As part of their required curriculum, second-year medical students at the University of Iowa complete an anonymous survey that presents eight questions involving specific contraception and abortion scenarios. In this pilot study, all 159 members of the Class of 2013 who had previously completed this required anonymous survey were invited to re-take the survey at the conclusion of their fourth year. Additional questions, asking the students if they felt that clinical clerkships had changed their perspectives on contraception and abortion in general, were included. Results: Of the 159 members of the Class of 2013, 42 volunteered to participate, for a response rate of 26%. Twenty students (47.62%) felt that clinical clerkships had changed their perspectives on contraception and thirteen students (39.95%) felt that clinical clerkships had changed their perspectives on abortion. The percentage of students who felt comfortable referring a patient to a colleague for an abortion increased significantly from 71.33% to 90.48% (p=0.024). Responses to the other seven questions included in the survey did not differ significantly pre and post-clerkships. Conclusions: This pilot study, although limited by a low response rate, suggests that clinical clerkships have the ability to impact medical students’ attitudes toward contraception and abortion in general, as well as toward specific scenarios involving abortion

UHB demonstrator interior noise control flight tests and analysis

The measurement and analysis of MD-UHB (McDonnell Douglas Ultra High Bypass) Demonstrator noise and vibration flight test data are described as they relate to passenger cabin noise. The analyses were done to investigate the interior noise characteristics of advanced turboprop aircraft with aft-mounted engines, and to study the effectiveness of selected noise control treatments in reducing passenger cabin noise. The UHB Demonstrator is an MD-80 test aircraft with the left JT8D engine replaced with a prototype UHB engine. For these tests, the UHB engine was a General Electric Unducted Fan, with either 8x8 or 10x8 counter-rotating propeller configurations. Interior noise level characteristics were studied for several altitudes and speeds, with emphasis on high altitude (35,000 ft), high speed (0.75 Mach) cruise conditions. The effectiveness of several noise control treatments was evaluated based on cabin noise measurements. The important airborne and structureborne transmission paths were identified for both tonal and broadband sources using the results of a sound intensity survey, exterior and interior noise and vibration data, and partial coherence analysis techniques. Estimates of the turbulent boundary layer pressure wavenumber-frequency spectrum were made, based on measured fuselage noise levels

Which missing value imputation method to use in expression profiles: a comparative study and two selection schemes

<p>Abstract</p> <p>Background</p> <p>Gene expression data frequently contain missing values, however, most down-stream analyses for microarray experiments require complete data. In the literature many methods have been proposed to estimate missing values via information of the correlation patterns within the gene expression matrix. Each method has its own advantages, but the specific conditions for which each method is preferred remains largely unclear. In this report we describe an extensive evaluation of eight current imputation methods on multiple types of microarray experiments, including time series, multiple exposures, and multiple exposures × time series data. We then introduce two complementary selection schemes for determining the most appropriate imputation method for any given data set.</p> <p>Results</p> <p>We found that the optimal imputation algorithms (LSA, LLS, and BPCA) are all highly competitive with each other, and that no method is uniformly superior in all the data sets we examined. The success of each method can also depend on the underlying "complexity" of the expression data, where we take complexity to indicate the difficulty in mapping the gene expression matrix to a lower-dimensional subspace. We developed an entropy measure to quantify the complexity of expression matrixes and found that, by incorporating this information, the entropy-based selection (EBS) scheme is useful for selecting an appropriate imputation algorithm. We further propose a simulation-based self-training selection (STS) scheme. This technique has been used previously for microarray data imputation, but for different purposes. The scheme selects the optimal or near-optimal method with high accuracy but at an increased computational cost.</p> <p>Conclusion</p> <p>Our findings provide insight into the problem of which imputation method is optimal for a given data set. Three top-performing methods (LSA, LLS and BPCA) are competitive with each other. Global-based imputation methods (PLS, SVD, BPCA) performed better on mcroarray data with lower complexity, while neighbour-based methods (KNN, OLS, LSA, LLS) performed better in data with higher complexity. We also found that the EBS and STS schemes serve as complementary and effective tools for selecting the optimal imputation algorithm.</p

Equilibrium Disk-Bulge-Halo Models for the Milky Way and Andromeda Galaxies

We describe a new set of self-consistent, equilibrium disk galaxy models that incorporate an exponential disk, a Hernquist model bulge, an NFW halo and a central supermassive black hole. The models are derived from explicit distribution functions for each component and the large number of parameters permit detailed modeling of actual galaxies. We present techniques that use structural and kinematic data such as radial surface brightness profiles, rotation curves and bulge velocity dispersion profiles to find the best-fit models for the Milky Way and M31. Through N-body realizations of these models we explore their stability against the formation of bars. The models permit the study of a wide range of dynamical phenomenon with a high degree of realism.Comment: 58 pages, 20 figures, submitted to the Astrophysical Journa

Quasi Stable Black Holes at the Large Hadron Collider

We adress the production of black holes at LHC and their time evolution in space times with compactified space like extra dimensions. It is shown that black holes with life times of hundred fm/c can be produced at LHC. The possibility of quasi-stable remnants is discussed.Comment: 4 pages, 3 figures, typos removed, omitted factors included, accepted for publicatio

Necessary Optimality Conditions for Higher-Order Infinite Horizon Variational Problems on Time Scales

We obtain Euler-Lagrange and transversality optimality conditions for higher-order infinite horizon variational problems on a time scale. The new necessary optimality conditions improve the classical results both in the continuous and discrete settings: our results seem new and interesting even in the particular cases when the time scale is the set of real numbers or the set of integers.Comment: This is a preprint of a paper whose final and definite form will appear in Journal of Optimization Theory and Applications (JOTA). Paper submitted 17-Nov-2011; revised 24-March-2012 and 10-April-2012; accepted for publication 15-April-201

Reconstructing the spectrum of the pregalactic density field from astronomical data

In this paper we evaluate the spectrum of the pregalactic density field on scales $1h^{-1}Mpc < r < 100h^{-1}$Mpc from a variety of astronomical data. APM data on $w(\theta)$ in six narrow magnitude is used, after correcting to possible evolutionary effects, to constrain the spectrum of galaxy clustering on scales $10h^{-1}Mpc < r < 50-100h^{-1}Mpc$. Fitting power spectra of CDM models to the data at all depths requires $\Omega h=0.2$ if the primordial index $n=1$ and $\Omega h=0.3$ if the spectrum is tilted with $n=0.7$. Then we compare the peculiar velocity field predicted by the APM spectrum of galaxy (light) distribution with the actual velocity data. The two fields are consistent and the comparison suggests that the bias factor is scale independent with $\Omega^{0.6}/b\simeq$(0.2-0.3). The next dataset used comes from the cluster correlation data. We calculate in detail the amplification of the cluster correlation function due to gravitational clustering and use the data on both the slope of the cluster correlation function and its amplitude-richness dependence. Cluster masses are normalized using the Coma cluster. We find that CDM models are hard to reconcile with all the three datasets: APM data on $w(\theta)$, the data on cluster correlation function, and the data on the latter's amplitude-richness dependence. We show that the data on the amplitude-richness dependence can be used directly to obtain the spectrum of the pregalactic density field. Applying the method to the data, we recover the density field on scales between 5 and 25$h^{-1}$Mpc whose slope is in good agreement with the APM data on the same scales. Requiring the two amplitudes to be the same, fixes the value of $\Omega$ to be 0.3 in agreement with observations of the dynamics of the Coma cluster. Finally we use the dataComment: to be published in Ap.J - minor revision + typos correcte