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1

An unbiased measurement of the UV background and its evolution via the proximity effect in quasar spectra  

NASA Astrophysics Data System (ADS)

We investigated a set of high-resolution (R˜45 000), high signal-to-noise (S/N˜70) quasar spectra to search for the signature of the so-called proximity effect in the H I Ly? forest. The sample consists of 40 bright quasars with redshifts in the range 2.1 < z < 4.7. Using the flux transmission statistic, we determined the redshift evolution of the H I effective optical depth in the Lyman forest between 2? z? 4.5, finding good agreement with previous measurements based on smaller samples. We also see the previously reported dip in ?_eff(z) around redshift z˜ 3.3, but as the significance of that feature is only 2.6?, we consider this detection tentative. Comparing the flux transmission near each quasar with what was expected from the overall trend of ?_eff(z), we clearly detect the proximity effect not only in the combined quasar sample, but also towards each individual line of sight at high significance, albeit with varying strength. We quantify this strength using a simple prescription based on a fiducial value for the intensity of the metagalactic UV background (UVB) radiation field at 1 Ryd, multiplied by a free parameter that varies from QSO to QSO. The observed proximity effect strength distribution (PESD) is asymmetric, with an extended tail towards values corresponding to a weak effect. We demonstrate that this is not simply an effect of gravitational clustering around quasars, as the same asymmetry is already present in the PESD predicted for purely Poissonian variance in the absorption lines. We present the results of running the same analysis on simulated quasar spectra generated by a simple Monte-Carlo code. Comparing the simulated PESD with observations, we argue that the standard method of determining the UVB intensity J?_0 by averaging over several lines of sight is heavily biased towards high values of J?_0 because of the PESD asymmetry. Using instead the mode of the PESD provides an estimate of J?_0 that is unbiased with respect to his effect. For our sample we get a modal value for the UVB intensity of log J?_0 = -21.51± 0.15 (in units of erg cm-2 s-1 Hz-1 sr-1) for a median quasar redshift of 2.73. With J?_0 fixed we then corrected ?_eff near each quasar for local ionisation and estimated the amount of excess H I absorption attributed to gravitational clustering. On scales of ˜ 3 Mpc, only a small minority of quasars show substantial overdensities of up to a factor of a few in ?_eff; these are exactly the objects with the weakest proximity effect signatures. After removing those quasars residing in overdense regions, we redetermined the UVB intensity using a hybrid approach of sample averaging and statistical correction for the PESD asymmetry bias, arriving at log J?_0 = -21.46+0.14-0.21. This is the most accurate measurement of J?_0 to date. We present a new diagnostic based on the shape and width of the PESD that strongly supports our conclusion that there is no systematic overdensity bias for the proximity effect. This additional diagnostic breaks the otherwise unavoidable degeneracy of the proximity effect between UVB and overdensity. We then applied our hybrid approach to estimate the redshift evolution of the UVB intensity and found tentative evidence of a mild decrease in log J?_0 with increasing redshift, by a factor of ˜ 0.4 from z=2 to z=4. Our results are in excellent agreement with earlier predictions for the evolving UVB intensity, and they also agree well with other methods of estimating the UVB intensity. In particular, our measured UVB evolution is much slower than the change in quasar space densities between z=4 and z=2, supporting the notion of a substantial contribution of star-forming galaxies to the UVB at high redshift. Based on data collected at the European Southern Observatory and obtained from the ESO Science Archive. Appendix A is only available in electronic form at http://www.aanda.org

Dall'Aglio, A.; Wisotzki, L.; Worseck, G.

2008-11-01

2

Unbiased Longitudinal Processing of  

E-print Network

of disease-modifying therapies and may have a profound clinical impact. 1. Background Repeatability%). Average absolute percent thickness change: pvs. Long, Wilcoxon signed rank test) Unbiased to median image. Produces crisp unbiased template, common voxel space. Acknowledgements: Ellison Medical

Reuter, Martin

3

Universal mean moment rate profiles of earthquake ruptures  

SciTech Connect

Earthquake phenomenology exhibits a number of power law distributions including the Gutenberg-Richter frequency-size statistics and the Omori law for aftershock decay rates. In search for a basic model that renders correct predictions on long spatiotemporal scales, we discuss results associated with a heterogeneous fault with long-range stress-transfer interactions. To better understand earthquake dynamics we focus on faults with Gutenberg-Richter-like earthquake statistics and develop two universal scaling functions as a stronger test of the theory against observations than mere scaling exponents that have large error bars. Universal shape profiles contain crucial information on the underlying dynamics in a variety of systems. As in magnetic systems, we find that our analysis for earthquakes provides a good overall agreement between theory and observations, but with a potential discrepancy in one particular universal scaling function for moment rates. We primarily use mean field theory for the theoretical analysis, since it has been shown to be in the same universality class as the full three-dimensional version of the model (up to logarithmic corrections). The results point to the existence of deep connections between the physics of avalanches in different systems.

Mehta, Amit P.; Dahmen, Karin A.; Ben-Zion, Yehuda [Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 (United States); Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740 (United States)

2006-05-15

4

Unbiased shifts of Brownian motion  

E-print Network

Let $B=(B_t)_{t\\in\\R}$ be a two-sided standard Brownian motion. An \\emph{unbiased shift} of $B$ is a random time $T$, which is a measurable function of $B$, such that $(B_{T+t}-B_T)_{t\\in\\R}$ is a Brownian motion independent of $B_T$. We characterise unbiased shifts in terms of allocation rules balancing additive functionals of $B$. For any probability distribution $\

Last, Günter; Thorisson, Hermann

2011-01-01

5

From Unbiased Numerical Estimates to Unbiased Interval Estimates  

E-print Network

corresponding to possible samples x = (x1, . . . , xn). In other words, we need to estimate a probability Unbiased Estimates: A Brief Reminder Estimating parameters of a probability distribution: a practical measurements. Based on this sample, we want to estimate the original probability distribution. Let us formulate

Ward, Karen

6

Spectra  

NSDL National Science Digital Library

Learners construct a spectroscope out of a shoe box or mailing tube, diffraction grating, and other simple materials. They then use their spectroscope to observe spectra, the colors that make up light. Learners compare the spectra of various light sources. Use this activity to introduce learners to basic principles of light and color. Also, look at a related page about auroras to understand how distinguishing spectra of different atoms helps scientists understand the universe.

Exploratorium, The

2012-06-26

7

Spectra  

NSDL National Science Digital Library

Spectra is a very informative website about how astronomers use spectra to understand what stars are made of, their structures, and their evolution. The page begins with an introduction to the electromagnetic spectrum and then goes into great detail about the properties of light. Then it talks about how matter both creates and destroys radiation. Then it discusses how to interpret absorption and emission lines. The website ends with how astronomers use spectra to understand stars, galaxies, other objects in the universe.

Kaler, James

2004-07-16

8

Comparison of Moment Rates from GPS Observations and Late Quaternary Paleoearthquakes on the Wasatch Fault, Utah  

NASA Astrophysics Data System (ADS)

The Wasatch fault marks the boundary of stable North America and the extensional Basin and Range province, and is capable of producing large, M6-7 earthquakes. Velocities from the University of Utah Wasatch Front permanent GPS network are analyzed to determine horizontal strain rates and extension rates across the Wasatch fault zone, Utah. Extension rates across the fault decrease from 2.24 ± 0.04 mm/yr in the north to 1.89 ± 0.04 mm/yr to the south. Observed GPS velocities are interpolated into strain rates and mapped, revealing that the highest strain rates are at the southern fault at 0.05x10-6 1/yr across a ~100 km profile; strain rates to the north are 0.02x10-6 1/yr but spread over a wider, ~150 km profile, indicating that another fault, possibly the East Great Salt Lake fault and/or Oquirrh fault, may be contributing to deformation. We construct dislocation models to determine whether additional faults can be identified, and whether the Wasatch fault geometry (strike, dip, slip rate) varies between segments. Strain rates are converted to geodetic moment loading rates for north, central, and south segments of the fault and compared to the Late Quaternary moment loading rates from prehistoric earthquake magnitudes based on fault trenching studies and averaged over time. Geodetic moment rates increased from north to south, from ~7x1023 to 1x1024 dyne cm/yr, exceeding the geologic moment rates by factors of ~2-4. The geodetic rates represent contemporary deformation and offer an alternate method to assess elastic strain accumulation on the Wasatch fault under present-day tectonic stresses.

Puskas, C.; Smith, R. B.; Chang, W.; Cannaday, A.; DuRoss, C. B.

2011-12-01

9

moment rate functions. Journal of Geophysical Research, 104, Bridgman, P. W., 1945. Polymorphic transition and geological phe-  

E-print Network

. Polymorphic transition and geological phe- nomenon. American Journal of Science, 243A, 90­97. Dziewonski, A. M data for studies of global and regional seismicity. Journal of Geophysical Research, 86, 2825moment rate functions. Journal of Geophysical Research, 104, 863­894. Bridgman, P. W., 1945

Liu, Mian

10

Entanglement detection using mutually unbiased measurements  

E-print Network

We study the entanglement detection by using mutually unbiased measurements and provide a quantum separability criterion that can be experimentally implemented for arbitrary $d$-dimensional bipartite systems. We show that this criterion is more effective than the criterion based on mutually unbiased bases. For isotropic states our criterion becomes both necessary and sufficient.

Bin Chen; Teng Ma; Shao-Ming Fei

2014-07-01

11

Entanglement detection using mutually unbiased measurements  

NASA Astrophysics Data System (ADS)

We study entanglement detection by using mutually unbiased measurements and provide a quantum separability criterion that can be experimentally implemented for arbitrary d-dimensional bipartite systems. We show that this criterion is more effective than the criterion based on mutually unbiased bases. For isotropic states our criterion becomes both necessary and sufficient.

Chen, Bin; Ma, Teng; Fei, Shao-Ming

2014-06-01

12

A SPITZER UNBIASED ULTRADEEP SPECTROSCOPIC SURVEY  

SciTech Connect

We carried out an unbiased, spectroscopic survey using the low-resolution module of the infrared spectrograph (IRS) onboard Spitzer targeting two 2.6 square arcminute regions in the GOODS-North field. The IRS was used in a spectral mapping mode with 5 hr of effective integration time per pixel. One region was covered between 14 and 21 mum and the other between 20 and 35 mum. We extracted spectra for 45 sources. About 84% of the sources have reported detections by GOODS at 24 mum, with a median f {sub n}u(24 mum) approx 100 muJy. All but one source are detected in all four IRAC bands, 3.6 to 8 mum. We use a new cross-correlation technique to measure redshifts and estimate IRS spectral types; this was successful for approx60% of the spectra. Fourteen sources show significant polycyclic aromatic hydrocarbon emission, four mostly SiO absorption, eight present mixed spectral signatures (low PAH and/or SiO) and two show a single line in emission. For the remaining 17, no spectral features were detected. Redshifts range from z approx 0.2 to z approx 2.2, with a median of 1. IR luminosities are roughly estimated from 24 mum flux densities, and have median values of 2.2 x 10{sup 11} L{sub sun} and 7.5 x 10{sup 11} L{sub sun} at z approx 1 and z approx 2, respectively. This sample has fewer active galactic nuclei than previous faint samples observed with the IRS, which we attribute to the fainter luminosities reached here.

Bertincourt, B.; Lagache, G.; Puget, J-L. [Institut d'Astrophysique Spatiale (IAS), Universite Paris-Sud 11 and CNRS (UMR 8617), Batiment 121, F-91405 Orsay (France); Helou, G.; Appleton, P.; Ogle, P.; Brooke, T.; Sheth, K. [Spitzer Science Center, Infrared Processing and Analysis Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Smith, J-D. [Steward Observatory, University of Arizona, Tucson, AZ (United States); Dale, D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Harwit, M. [511 H Street, SW, Washington DC 20024-2725 (United States)] [Cornell University, Ithaca, NY (United States); Roussel, H., E-mail: benjamin.bertincourt@ias.u-psud.f, E-mail: guilaine.lagache@ias.u-psud.f, E-mail: jean-loup.puget@ias.u-psud.f [Institut d'Astrophysique de Paris, UPMC (Universite Paris 6), 75014 Paris (France)

2009-11-01

13

Best Linear Unbiased Estimate Motivation for BLUE  

E-print Network

1 Chapter 6 Best Linear Unbiased Estimate (BLUE) #12;2 Motivation for BLUE Except for Linear Model to a sub-optimal estimate BLUE is one such sub-optimal estimate Idea for BLUE: 1. Restrict estimate) Advantage of BLUE:Needs only 1st and 2nd moments of PDF Mean & Covariance Disadvantages of BLUE: 1. Sub

Fowler, Mark

14

Maximally Entangled States via Mutual Unbiased collective Bases  

E-print Network

Relative and center of mass cordinates are used to generalize mutually unbiased bases (MUB) and define mutually unbiased bases (MUCB). Maximal entangled states are given as product staes in the collective varibles

M. Revzen

2009-10-16

15

Uncertainty relations based on mutually unbiased measurements  

E-print Network

We derive uncertainty relation inequalities according to the mutually unbiased measurements. Based on the calculation of the index of coincidence of probability distribution given by $d+1$ MUMs on any density operator $\\rho$ in $\\mathbb{C}^{d}$, both state-dependent and state-independent forms of lower entropic bounds are given. Furthermore, we formulate uncertainty relations for MUMs in terms of R\\'{e}nyi and Tsallis entropies.

Bin Chen; Shao-Ming Fei

2014-07-25

16

Markovian Description of Unbiased Polymer Translocation  

E-print Network

We perform, with the help of cloud computing resources, extensive Langevin simulations which provide compelling evidence in favor of a general markovian framework for unbiased polymer translocation. Our statistical analysis consists of careful evaluations of (i) two-point correlation functions of the translocation coordinate and (ii) the empirical probabilities of complete polymer translocation (taken as a function of the initial number of monomers on a given side of the membrane). We find good agreement with predictions derived from the Markov chain approach recently addressed in the literature by the present authors.

Felipe Mondaini; L. Moriconi

2012-03-20

17

Arithmetic, mutually unbiased bases and complementary observables  

SciTech Connect

Complementary observables in quantum mechanics may be viewed as Frobenius structures in a dagger monoidal category, such as the category of finite dimensional Hilbert spaces over the complex numbers. On the other hand, their properties crucially depend on the discrete Fourier transform and its associated quantum torus, requiring only the finite fields that underlie mutually unbiased bases. In axiomatic topos theory, the complex numbers are difficult to describe and should not be invoked unnecessarily. This paper surveys some fundamentals of quantum arithmetic using finite field complementary observables, with a view considering more general axiom systems.

Sheppeard, M. D. [Oxford University Computing Laboratory, Wolfson Building, Parks Rd., Oxford OX1 3QD (United Kingdom)

2010-02-15

18

Unbiased Luminosity Calibrations for HIPPARCOS Data  

NASA Astrophysics Data System (ADS)

One of the main uses of the Hipparcos astrometric parameters is the calibration of stellar luminosities against colour indices. The high quality of Hipparcos parameters would however be useless if selection biases were not taken into account. Using parametrical probability density functions, a maximum likelihood algorithm has been developed. It takes into account limiting magnitude or limiting parallax in order to compute unbiased estimates of various parameters: absolute magnitude (as a function of colour indices, metallicity, v sin(i)), galactic scale height, and first- and second-order moment of the velocity ellipsoid. As a by-product, improved estimates of distances can be obtained. A multi-platform, tcl/tk based user interface has been built which allows to determine the relevant parameters using Hipparcos data. The algorithm is described, together with the adopted parametrical models, and several applications are given.

Arenou, F.; Gomez, A. E.

1997-08-01

19

Mutually unbiased bases and bound entanglement  

NASA Astrophysics Data System (ADS)

In this contribution we relate two different key concepts: mutually unbiased bases (MUBs) and entanglement. We provide a general toolbox for analyzing and comparing entanglement of quantum states for different dimensions and numbers of particles. In particular we focus on bound entanglement, i.e. highly mixed states which cannot be distilled by local operations and classical communications. For a certain class of states—for which the state-space forms a ‘magic’ simplex—we analyze the set of bound entangled states detected by the MUB criterion for different dimensions d and number of particles n. We find that the geometry is similar for different d and n, consequently the MUB criterion opens possibilities to investigate the typicality of positivity under partial transposition (PPT)-bound and multipartite bound entanglement more deeply and provides a simple experimentally feasible tool to detect bound entanglement.

Hiesmayr, Beatrix C.; Löffler, Wolfgang

2014-04-01

20

O Biased and Unbiased Diffusion in Fractal Media  

Microsoft Academic Search

Using a renormalization method first introduced by Machta, we study the random motion of a walker on different fractal structures. We analyze the biased and unbiased motion of such walkers in the presence of an external field and also in an unbiased environment respectively. We concentrate on two types of fractal structures: looples structures and structures that consist entirely of

Hernan Leonardo Martinez

1993-01-01

21

Cyclic mutually unbiased bases, Fibonacci polynomials and Wiedemann's conjecture  

E-print Network

We relate the construction of a complete set of cyclic mutually unbiased bases, i. e., mutually unbiased bases generated by a single unitary operator, in power-of-two dimensions to the problem of finding a symmetric matrix over F_2 with an irreducible characteristic polynomial that has a given Fibonacci index. For dimensions of the form 2^(2^k) we present a solution that shows an analogy to an open conjecture of Wiedemann in finite field theory. Finally, we discuss the equivalence of mutually unbiased bases.

Ulrich Seyfarth; Kedar S. Ranade

2011-04-01

22

Information-Disturbance Theorem for Mutually Unbiased Observables  

E-print Network

We derive a novel version of information-disturbance theorems for mutually unbiased observables. We show that the information gain by Eve inevitably makes the outcomes by Bob in the conjugate basis not only erroneous but random.

Takayuki Miyadera; Hideki Imai

2006-02-05

23

Concepts and Hypotheses Search-based Learning Unbiased Learning Concept Learning  

E-print Network

Concepts and Hypotheses Search-based Learning Unbiased Learning Concept Learning #12;Concepts and Hypotheses Search-based Learning Unbiased Learning 1 Concepts and Hypotheses Definitions Example Hypotheses 2 Search-based Learning Find-S List-then-Eliminate Candidate Elimination 3 Unbiased Learning Bias Unbiased

Kjellström, Hedvig

24

Concepts and Hypotheses Search-based Learning Unbiased Learning Concept Learning  

E-print Network

Concepts and Hypotheses Search-based Learning Unbiased Learning Concept Learning Concepts and Hypotheses Search-based Learning Unbiased Learning 1 Concepts and Hypotheses Definitions Example Hypotheses 2 Search-based Learning Find-S List-then-Eliminate Candidate Elimination 3 Unbiased Learning Bias Unbiased

Kjellström, Hedvig

25

Title: Unbiased one dimensional University Ranking application based preference ordering  

E-print Network

level of worldwide reputation. Since no adequate measure of competitiveness of university rankers1 Title: Unbiased one dimensional University Ranking ­ application based preference ordering Authors: András TELCS Professor of Quantitative Methods, University of Pannonia and Assoc. Prof

Telcs, András

26

Multi-scale Unbiased Diffeomorphic Atlas Construction on , Jens Kruger  

E-print Network

Multi-scale Unbiased Diffeomorphic Atlas Construction on Multi-GPUs Linh Ha , Jens Kr¨uger Sarang providing effective segmentation via registration of anatomical labels. The brain atlas construction Joshi Cl´audio T. Silva August 9, 2010 In this chapter, we present a high performance multi-scale 3D

Silva, Claudio T.

27

Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics  

E-print Network

Blue Moon sampling, vectorial reaction coordinates, and unbiased constrained dynamics Giovanni force in terms of a conditional expectation which can be computed by Blue Moon sampling Introduction Fifteen years ago the Blue Moon ensemble method was introduced to sample rare events that occur

Van Den Eijnden, Eric

28

ORIGINAL PAPER Towards an unbiased metabolic profiling of protozoan  

E-print Network

ORIGINAL PAPER Towards an unbiased metabolic profiling of protozoan parasites: optimisation of the analytical approach, consisting of hydrophilic interaction liquid chromatography coupled to LTQ-orbitrap mass is then extracted in cold chloroform/methanol/water 20/60/20 (v/v/v) for 1 h at 4 °C, resulting in both cell

Breitling, Rainer

29

Unbiased Identification of Nonlinear Sorption Characteristics by Soil Column Breakthrough  

E-print Network

Unbiased Identification of Nonlinear Sorption Characteristics by Soil Column Breakthrough, 35K65 \\Lambda submitted to Water Resources Research #12; 2 B. A. Igler, K. U. Totsche and P. Knabner column experiments are used to identify partitioning coefficients, ion­exchange or sorption isotherms

Gugat, Martin

30

Spitzer Observations of an Unbiased AGN Sample of the Local Universe  

NASA Astrophysics Data System (ADS)

We present our preliminary results of the analysis of Spitzer observations of the first unbiased AGN sample of the local universe. High column densities of absorbing material along our line of sight can significantly change the observed properties of AGNs. Thus, optical, infrared, and soft X-ray selected samples are hampered by extinction, star formation and absorption, respectively. Therefore an unbiased sample of AGNs is important to investigate the "hidden" nature of the nuclear source. The swift BAT survey in the 14-195 keV band represents a complete sample including Compton thin and previously unknown or non-famous AGNs that were missed from previous X-ray surveys in the 2-10 keV band. Our BAT AGN sample contains 130 objects (z < 0.05 and |b| >15 degrees) that have been observed with the Infrared Spectrograph (IRS) on board Spitzer (Spitzer observer proposal 30745 and 50588; PI: K.A. Weaver). This statistically significant unbiased AGN sample and the richness of the infrared spectrum provides a unique opportunity to test our understanding of AGN unification, classification and evolution in general. Strong polycyclic aromatic hydrocarbon (PAH) emission features at 6.2 and 11.25, and low ionization emission lines such as [Ne II] 12.81 are good indicators of stellar activity. On the other hand, high ionization emission lines such as [O IV] 25.89, [Ne III] 15.51 and [Ne V] 14.32,24.32 can be associated with the AGN. The line ratios between the high- and low-ionization emission lines can be used to measure the relative dominance of the AGN and to investigate the ionization state of the emission-line gas. We present the preliminary infrared spectra of our X-ray selected sample, different correlations and implication to the AGN classification and evolution.

Melendez, Marcio; Weaver, K. A.; Mushotzky, R. F.; Tueller, J.; Markwardt, C. B.; Kraemer, S.; Malumuth, E. M.; Armus, L.; Berghea, C.; Engle, K.; Dudik, R. P.; Winter, L. M.

2009-01-01

31

Building Unbiased Estimators from Non-Gaussian Likelihoods with Application to Shear Estimation  

E-print Network

We develop a general framework for generating estimators of a given quantity which are unbiased to a given order in the difference between the true value of the underlying quantity and the fiducial position in theory space around which we expand the likelihood. We apply this formalism to rederive the optimal quadratic estimator and show how the replacement of the second derivative matrix with the Fisher matrix is generic way of creating an unbiased estimator (if one does not modify the initial guess at the weight matrix $C^{-1}$ iteratively based estimates from the data, which generally creates a bias). Next we apply the approach to estimation of shear lensing, closely following the work of Bernstein and Armstrong (2014). Our first order estimator reduces to their estimator in the limit of zero shear, but it also naturally allows for the case of non-constant shear and the easy calculation of correlation functions or power spectra using standard methods. Both our first-order estimator and Bernstein and Armstro...

Madhavacheril, Mathew S; Sehgal, Neelima; Slosar, Anže

2014-01-01

32

Unbiased Estimation of Refractive State of Aberrated Eyes  

PubMed Central

To identify unbiased methods for estimating the target vergence required to maximize visual acuity based on wavefront aberration measurements. Experiments were designed to minimize the impact of confounding factors that have hampered previous research. Objective wavefront refractions and subjective acuity refractions were obtained for the same monochromatic wavelength. Accommodation and pupil fluctuations were eliminated by cycloplegia. Unbiased subjective refractions that maximize visual acuity for high contrast letters were performed with a computer controlled forced choice staircase procedure, using 0.125 diopter steps of defocus. All experiments were performed for two pupil diameters (3mm and 6mm). As reported in the literature, subjective refractive error does not change appreciably when the pupil dilates. For 3 mm pupils most metrics yielded objective refractions that were about 0.1D more hyperopic than subjective acuity refractions. When pupil diameter increased to 6 mm, this bias changed in the myopic direction and the variability between metrics also increased. These inaccuracies were small compared to the precision of the measurements, which implies that most metrics provided unbiased estimates of refractive state for medium and large pupils. A variety of image quality metrics may be used to determine ocular refractive state for monochromatic (635nm) light, thereby achieving accurate results without the need for empirical correction factors. PMID:21777601

Martin, Jesson; Vasudevan, Balamurali; Himebaugh, Nikole; Bradley, Arthur; Thibos, Larry

2011-01-01

33

Unbiased Categorical Classification of Pediatric Sleep Disordered Breathing  

PubMed Central

Study Objectives: To classify pediatric sleep disordered breathing (SDB) using unbiased approaches. In children, decisions regarding severity and treatment of SDB are conducted solely based on empirical observations. Although recognizable entities clearly exist under the SDB spectrum, neither the number of SDB categories nor their specific criteria have been critically defined. Design: retrospective cohort analysis and random prospective cohort Setting: community and clinical sample Patients or Participants: Urban 5- to 9-year-old community children undergoing overnight sleep study (NPSG), and a comparable prospectively recruited clinical SDB sample. Interventions: n/a Measurements and Results: Principal component analysis was used to identify the uniqueness of the polysomnographically derived measures that are routinely used in clinical settings: apnea-hypopnea index, apnea index, obstructive apnea index, nadir SpO2, spontaneous arousal index and respiratory arousal index. These measures were then incorporated using unbiased data mining approaches to further characterize and discriminate across categorical phenotypes. Of 1,133 subjects, 52.8% were habitual snorers. Six categorical phenotypes clustered without any a priori hypothesis. Secondly, a non-hierarchical model that incorporated 6 NPSG-derived measures enabled unbiased identification of algorithms that predicted these 6 severity-based clusters. Thirdly, a hierarchical model was developed and performed well on all severity-based clusters. Classification and predictive models were subsequently cross-validated statistically as well as clinically, using 2 additional datasets that included 259 subjects. Modeling reached ?93% accuracy in cluster assignment. Conclusions: Data-driven analysis of conventional NPSG-derived indices identified 6 distinct clusters ranging from a cluster with normal indices toward clusters with more abnormal indices. Categorical assignment of individual cases to any of such clusters can be accurately predicted using a simple algorithm. These clusters may further enable prospective unbiased characterization of clinical outcomes and of genotype-phenotype interactions across multiple datasets. Citation: Spruyt K; Verleye G; Gozal D. Unbiased categorical classification of pediatric sleep disordered breathing. SLEEP 2010;33(10):1341-1347. PMID:21061856

Spruyt, Karen; Verleye, Gino; Gozal, David

2010-01-01

34

Unbiased Water and Methanol Maser Surveys of NGC 1333  

NASA Astrophysics Data System (ADS)

We present the results of unbiased 22 GHz H2O water and 44 GHz class I CH3OH methanol maser surveys in the central 7' × 10' area of NGC 1333 and two additional mapping observations of a 22 GHz water maser in a ~3' × 3' area of the IRAS4A region. In the 22 GHz water maser survey of NGC 1333 with a sensitivity of ? ~ 0.3 Jy, we confirmed the detection of masers toward H2O(B) in the region of HH 7-11 and IRAS4B. We also detected new water masers located ~20'' away in the western direction of IRAS4B or ~25'' away in the southern direction of IRAS4A. We could not, however, find young stellar objects or molecular outflows associated with them. They showed two different velocity components of ~0 and ~16 km s-1, which are blue- and redshifted relative to the adopted systemic velocity of ~7 km s-1 for NGC 1333. They also showed time variabilities in both intensity and velocity from multi-epoch observations and an anti-correlation between the intensities of the blue- and redshifted velocity components. We suggest that the unidentified power source of these masers might be found in the earliest evolutionary stage of star formation, before the onset of molecular outflows. Finding this kind of water maser is only possible through an unbiased blind survey. In the 44 GHz methanol maser survey with a sensitivity of ? ~ 0.5 Jy, we confirmed masers toward IRAS4A2 and the eastern shock region of IRAS2A. Both sources are also detected in 95 and 132 GHz methanol maser lines. In addition, we had new detections of methanol masers at 95 and 132 GHz toward IRAS4B. In terms of the isotropic luminosity, we detected methanol maser sources brighter than ~5 × 1025 erg s-1 from our unbiased survey.

Lyo, A.-Ran; Kim, Jongsoo; Byun, Do-Young; Lee, Ho-Gyu

2014-11-01

35

Quadratic discrete Fourier transform and mutually unbiased bases  

E-print Network

The present chapter [submitted for publication in "Fourier Transforms, Theory and Applications", G. Nikolic (Ed.), InTech (Open Access Publisher), Vienna, 2011] is concerned with the introduction and study of a quadratic discrete Fourier transform. This Fourier transform can be considered as a two-parameter extension, with a quadratic term, of the usual discrete Fourier transform. In the case where the two parameters are taken to be equal to zero, the quadratic discrete Fourier transform is nothing but the usual discrete Fourier transform. The quantum quadratic discrete Fourier transform plays an important role in the field of quantum information. In particular, such a transformation in prime dimension can be used for obtaining a complete set of mutually unbiased bases.

Maurice Robert Kibler

2010-10-28

36

Walking in Facebook: A Case Study of Unbiased Sampling of OSNs  

E-print Network

Walking in Facebook: A Case Study of Unbiased Sampling of OSNs Minas Gjoka Networked Systems UC of Facebook users by crawling its social graph. In this quest, we consider and implement several candidate to the best of our knowledge unbiased sample of Facebook. Finally, we use one of our representative datasets

Markopoulou, Athina

37

Mutually unbiased projectors and duality between lines and bases in finite quantum systems  

SciTech Connect

Quantum systems with variables in the ring Z(d) are considered, and the concepts of weak mutually unbiased bases and mutually unbiased projectors are discussed. The lines through the origin in the Z(d)×Z(d) phase space, are classified into maximal lines (sets of d points), and sublines (sets of d{sub i} points where d{sub i}|d). The sublines are intersections of maximal lines. It is shown that there exists a duality between the properties of lines (resp., sublines), and the properties of weak mutually unbiased bases (resp., mutually unbiased projectors). -- Highlights: •Lines in discrete phase space. •Bases in finite quantum systems. •Duality between bases and lines. •Weak mutually unbiased bases.

Shalaby, M.; Vourdas, A., E-mail: a.vourdas@bradford.ac.uk

2013-10-15

38

Unbiased water and methanol maser surveys of NGC 1333  

E-print Network

We present the results of unbiased 22 GHz H2O water and 44 GHz class I CH3OH methanol maser surveys in the central 7x10 arcmin area of NGC 1333 and two additional mapping observations of a 22 GHz water maser in a ~3x3arcmin area of the IRAS4A region. In the 22 GHz water maser survey of NGC 1333 with sensitivity of sigma~0.3Jy, we confirmed masers toward H2O(B) in the region of HH 7-11 and IRAS4B. We also detected new water masers at ~20arcsec away in the western direction of IRAS4B or ~25arcsec away in the southern direction of IRAS4A. We could not however find young stellar objects or molecular outflows associated with them. They showed two different velocity components of ~0 and ~16 km/s, which are blue- and red-shifted relative to the adopted systemic velocity of ~7 km/s for NGC 1333. They also showed time variabilities in both intensity and velocity from multi-epoch observations and an anti-correlation between the intensities of the blue- and the red-shifted velocity components. We suggest that the uniden...

Lyo, A-Ran; Byun, Do-Young; Lee, Ho-Gyu

2014-01-01

39

Galois Unitaries, Mutually Unbiased Bases, and MUB-balanced states  

E-print Network

A Galois unitary is a generalization of the notion of anti-unitary operators. They act only on those vectors in Hilbert space whose entries belong to some chosen number field. For Mutually Unbiased Bases the relevant number field is a cyclotomic field. By including Galois unitaries we are able to remove a mismatch between the finite projective group acting on the bases on the one hand, and the set of those permutations of the bases that can be implemented as transformations in Hilbert space on the other hand. In particular we show that there exist transformations that cycle through all the bases in every dimension which is an odd power of an odd prime. (For even primes unitary MUB-cyclers exist.) These transformations have eigenvectors, which are MUB-balanced states (i.e. rotationally symmetric states in the original terminology of Wootters and Sussman) if and only if d = 3 modulo 4. We conjecture that this construction yields all such states in odd prime power dimension.

D. M. Appleby; Ingemar Bengtsson; Hoan Bui Dang

2014-09-29

40

Unbiased Approach for Virus Detection in Skin Lesions  

PubMed Central

To assess presence of virus DNA in skin lesions, swab samples from 82 squamous cell carcinomas of the skin (SCCs), 60 actinic keratoses (AKs), paraffin-embedded biopsies from 28 SCCs and 72 kerathoacanthomas (KAs) and fresh-frozen biopsies from 92 KAs, 85 SCCs and 92 AKs were analyzed by high throughput sequencing (HTS) using 454 or Ion Torrent technology. We found total of 4,284 viral reads, out of which 4,168 were Human Papillomavirus (HPV)-related, belonging to 15 known (HPV8, HPV12, HPV20, HPV36, HPV38, HPV45, HPV57, HPV59, HPV104, HPV105, HPV107, HPV109, HPV124, HPV138, HPV147), four previously described putative (HPV 915 F 06 007 FD1, FA73, FA101, SE42) and two putatively new HPV types (SE46, SE47). SE42 was cloned, sequenced, designated as HPV155 and found to have 76% similarity to the most closely related known HPV type. In conclusion, an unbiased approach for viral DNA detection in skin tumors has found that, although some new putative HPVs were found, known HPV types constituted most of the viral DNA. PMID:23840382

Bzhalava, Davit; Johansson, Hanna; Ekstrom, Johanna; Faust, Helena; Moller, Birgitta; Eklund, Carina; Nordin, Peter; Stenquist, Bo; Paoli, John; Persson, Bengt; Forslund, Ola; Dillner, Joakim

2013-01-01

41

Depicting qudit quantum mechanics and mutually unbiased qudit theories  

E-print Network

We generalize the ZX calculus to quantum systems of dimension higher than two. The resulting calculus is sound and universal for quantum mechanics. We define the notion of a mutually unbiased qudit theory and study two particular instances of these theories in detail: qudit stabilizer quantum mechanics and Spekkens-Schreiber toy theory for dits. The calculus allows us to analyze the structure of qudit stabilizer quantum mechanics and provides a geometrical picture of qudit stabilizer theory using D-toruses, which generalizes the Bloch sphere picture for qubit stabilizer quantum mechanics. We also use our framework to describe generalizations of Spekkens toy theory to higher dimensional systems. This gives a novel proof that qudit stabilizer quantum mechanics and Spekkens-Schreiber toy theory for dits are operationally equivalent in three dimensions. The qudit pictorial calculus is a useful tool to study quantum foundations, understand the relationship between qubit and qudit quantum mechanics, and provide a novel, high level description of quantum information protocols.

André Ranchin

2014-04-04

42

All-optical control of ultrafast photocurrents in unbiased graphene.  

PubMed

Graphene has recently become a unique playground for studying light-matter interaction effects in low-dimensional electronic systems. Being of strong fundamental importance, these effects also open a wide range of opportunities in photonics and optoelectronics. In particular, strong and broadband light absorption in graphene allows one to achieve high carrier densities essential for observation of nonlinear optical phenomena. Here, we make use of strong photon-drag effect to generate and optically manipulate ultrafast photocurrents in graphene at room temperature. In contrast to the recent reports on injection of photocurrents in graphene due to external or built-in electric field effects and by quantum interference, we force the massless charge carriers to move via direct transfer of linear momentum from photons of incident laser beam to excited electrons in unbiased sample. Direction and amplitude of the drag-current induced in graphene are determined by polarization, incidence angle and intensity of the obliquely incident laser beam. We also demonstrate that the irradiation of graphene with two laser beams of the same wavelength offers an opportunity to manipulate the photocurrents in time domain. The obtained all-optical control of the photocurrents opens new routes towards graphene based high-speed and broadband optoelectronic devices. PMID:24500084

Obraztsov, Petr A; Kaplas, Tommi; Garnov, Sergey V; Kuwata-Gonokami, Makoto; Obraztsov, Alexander N; Svirko, Yuri P

2014-01-01

43

Unbiased stereological method to assess proliferation throughout the subependymal zone.  

PubMed

The subependymal zone (SEZ), frequently named as adult subventricular zone (SVZ), is a niche of adult neural stem and progenitor cells that lines a large extension of the lateral ventricles of the brain. The majority of the studies do not analyze the SEZ throughout its entire extension. Instead, studies of cell populations within the SEZ typically focus their analysis on a narrow space between specific bregma coordinates that provides a perspective of only a small portion of the SEZ. We have previously proposed a standard division for the SEZ at the anterior-posterior and dorsal-ventral axes based on external brain anatomical hallmarks (Falcao et al., PLoS One 7:e38647, 2012). Herein, we describe in detail the procedure and a stereological approach that can be used to obtain an unbiased estimation of the SEZ cell proliferation under physiological and pathological conditions. This approach takes into consideration clear SEZ anatomical divisions, both on the anterior-posterior and dorsal-ventral axes, which will standardize future studies on the SEZ. PMID:23959988

Falcão, Ana Mendanha; Palha, Joana Almeida; Ferreira, Ana Catarina; Marques, Fernanda; Sousa, Nuno; Sousa, João Carlos

2013-01-01

44

On an unbiased and consistent estimator for mutation rates.  

PubMed

Spontaneous mutations are stochastic events. The mutation rate, defined as mutations per genome per replication, is generally very low, and it is widely accepted that spontaneous mutations occur at defined, but different, rates in bacteriophage and in bacterial, insect, and mammalian cells. The calculation of mutation rates has proved to be a significant problem. Mutation rates can be calculated by following mutant accumulation during growth or from the distribution of mutants obtained in parallel cultures. As Luria and Delbrück described in 1943, the number of mutants in parallel populations of bacterial cells varies widely depending on when a spontaneous mutation occurs during growth of the culture. Since 1943, many mathematical refinements to estimating rates, called estimators, have been described to facilitate determination of the mutation rate from the distribution or frequency of mutants detected following growth of parallel cultures. We present a rigorous mathematical solution to the mutation rate problem using an unbiased and consistent estimator. Using this estimator we demonstrate experimentally that mutation rates can be easily calculated by determining mutant accumulation, that is, from the number of mutants measured in two successive generations. Moreover, to verify the consistency of our estimator we conduct a series of simulation trials that show a surprisingly rapid convergence to the targeted mutation rate (reached between 25th and 30th generations). PMID:22326895

Niccum, Brittany A; Poteau, Roby; Hamman, Glen E; Varada, Jan C; Dshalalow, Jewgeni H; Sinden, Richard R

2012-05-01

45

An Unbiased Census of Active Galactic Nuclei in the Two Micron All Sky Survey  

NASA Astrophysics Data System (ADS)

We present an unbiased near-IR-selected AGN sample, covering 12.56 deg2 down to Ks~15.5, selected from the Two Micron All Sky Survey (2MASS). Our only selection effect is a moderate color cut (J-Ks>1.2) designed to reduce contamination from Galactic stars. We observed both pointlike and extended sources. Using the brute-force capabilities of the Two Degree Field multifiber spectrograph on the Anglo-Australian Telescope, we obtained spectra of 65% of the target list: an unbiased subsample of 1526 sources. Eighty percent of the 2MASS sources in our fields are galaxies, with a median redshift of 0.15. The remainder are K and M dwarf stars. We find tentative evidence that Seyfert 2 nuclei are more common in our IR-selected survey than in blue-selected galaxy surveys. We estimate that 5.1+/-0.7% of the galaxies have Seyfert 2 nuclei with H? equivalent widths greater than 0.4 nm, measured over a spectroscopic aperture of radius ~2.5 kpc. Blue-selected galaxy samples only find Seyfert 2 nuclei meeting these criteria in ~1.5% of galaxies. We find that 1.2+/-0.3% of our sources are broadline (type 1) AGNs, giving a surface density of 1.0+/-0.3 deg2, down to Ks<15.0. This is the same surface density of type 1 AGNs as optical samples down to B<18.5. Our type 1 AGNs, however, mostly lie at low redshifts, and host galaxy light contamination would make ~50% of them hard to find in optical QSO samples. We conclude that the type 1 AGN population found in the near-IR is not dramatically different from that found in optical samples. There is no evidence for a large population of AGNs that could not be found at optical wavelengths, although we can only place very weak constraints on any population of dusty high-redshift QSOs. In contrast, the incidence of type 2 (narrow-line) AGNs in a near-IR-selected galaxy sample seems to be higher than in a blue-selected galaxy sample.

Francis, Paul J.; Nelson, Brant O.; Cutri, Roc M.

2004-02-01

46

High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies  

NASA Astrophysics Data System (ADS)

A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations in most wavebands. These can only be quantified using a sample that is sufficiently unbiased to test orientation effects. Low-frequency radio emission is one way to select a close-to orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission.Recent Chandra, Spitzer and Herschel observations combined with multi-wavelength data for a complete sample of high-redshift (1 24.2) = 2.5:1.4:1 in these high-luminosity (log L(0.3-8keV) ~ 44-46) sources. These ratios are consistent with current expectations based on modelingthe Cosmic X-ray Background. A strong correlation with radio orientation constrains the geometry of the obscuring disk/torus to have a ~60 degree opening angle and ~12 degree Compton-thick cross-section. The deduced ~50% obscured fraction of the population contrasts with typical estimates of ~20% obscured in optically- and X-ray-selected high-luminosity samples. Once the primary nuclear emission is obscured, AGN X-ray spectra are frequently dominated by unobscured non-nuclear or scattered nuclear emission which cannot be distinguished from direct nuclear emission with a lower obscuration level unless high quality data is available. As a result, both the level of obscuration and the estimated instrinsic luminosities of highly-obscured AGN are likely to be significantly (*10-1000) underestimated for 25-50% of the population. This may explain the lower obscured fractions reported for optical and X-ray samples which have no independent measure of the AGN luminosity. Correcting AGN samples for these underestimated luminosities would result in flatter derived luminosity functions and potentially change their evolution.

Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

2014-08-01

47

X-ray Properties of an Unbiased Hard X-ray Detected Sample of AGN  

NASA Technical Reports Server (NTRS)

The SWIFT gamma ray observatory's Burst Alert Telescope (BAT) has detected a sample of active galactic nuclei (AGN) based solely on their hard X-ray flux (14-195keV). In this paper, we present for the first time XMM-Newton X-ray spectra for 22 BAT AGXs with no previously analyzed X-ray spectra. If our sources are a representative sample of the BAT AGN, as we claim, our results present for the first time global X-ray properties of an unbiased towards absorption (n(sub H) < 3 x 10(exp 25)/sq cm), local (< z >= 0.03), AGN sample. We find 9/22 low absorption (n(sub H) < 10(exp 23)/sq cm), simple power law model sources, where 4 of these sources have a statistically significant soft component. Among these sources, we find the presence of a warm absorber statistically significant for only one Seyfert 1 source, contrasting with the ASCA results of Reynolds (1997) and George et al. (1998), who find signatures of warm absorption in half or more of their Seyfert 1 samples at similar redshifts. Additionally, the remaining sources (13122) have more complex spectra, well-fit by an absorbed power law at E > 2.0 keV. Five of the complex sources (NGC 612, ESO 362-G018, MRK 417, ESO 506-G027, and NGC 6860) are classified as Compton-thick candidates. Further, we find four more sources (SWIFT J0641.3+3257, SWIFT J0911.2+4533, SWIFT J1200.8+0650, and NGC 4992) with properties consistent with the hidden/buried AGN reported by Ueda et al. (2007). Finally, we include a comparison of the XMM EPIC spectra with available SWIFT X-ray Telescope (XRT) observations. From these comparisons, we find 6/16 sources with varying column densities, 6/16 sources with varying power law indices, and 13/16 sources with varying fluxes, over periods of hours to months. Flux and power law index are correlated for objects where both parameters vary.

Winter, Lisa M.; Mushotzky, Richard F.; Tueller, Jack; Markwardt, Craig

2007-01-01

48

Antenna-coupled unbiased detectors for LW-IR regime  

NASA Astrophysics Data System (ADS)

At room temperature (300K), the electromagnetic (EM) radiation emitted by humans and other living beings peaks mostly in the long-wavelength infrared (LW-IR) regime. And since the atmosphere shows relatively little absorption in this band, applications such as target detection, tracking, active homing, and navigation in autonomous vehicles extensively use the LW-IR frequency range. The present research work is focused on developing antenna-based, uncooled, and unbiased detectors for the LW-IR regime. In the first part of this research, antenna-coupled metal-oxide-metal diodes (ACMOMD) are investigated. In response to the EM radiation, high-frequency antenna currents are induced in the antenna. An asymmetric-barrier Al-Al2O3-Pt MOM diode rectifies the antenna currents. Two different types of fabrication processes have been developed for ACMOMDs namely one-step lithography and two-step lithography. The major drawbacks of MOM-based devices include hard-to-control fabrication processes, generally very high zero-biased resistances, and vulnerability to electrostatic discharges, leading to unstable electrical characteristics. The second part of this research focuses on the development of unbiased LW-IR sensors based on the Seebeck effect. If two different metals are joined together at one end and their other ends are open-circuited, and if a non-zero temperature difference exists between the joined end and the open ends, then a non-zero open-circuit voltage can be measured between the open ends of the wires. Based on this effect, we have developed antenna-coupled nano-thermocouples (ACNTs) in which radiation-induced antenna currents produce polarization-dependent heating of the joined end of the two metals whereas the open ends remain at substrate temperature. This polarization-dependent heating induces polarization-dependent temperature difference between the joined end and the open ends of the metals leading to a polarization-dependent open-circuit voltage between the open ends of the metals. A CW CO2 laser tuned at 10.6 mum wavelength has been used for infrared characterization of these sensors. For these sensors, average responsivity of 22.7 mV/W, signal-to-noise (SNR) ratio of 29 dB, noise equivalent power (NEP) of 1.55 nW, and specific detectivity (D*) of 1.77x105 cm. Hz .W--1 were measured. ACNTs are expected to operate at frequencies much beyond 400 KHz. The third part of this research focuses on the effect of DC read-out interconnects on polarization characteristics of the planar dipole antennas. Different geometries of the interconnects present different electromagnetic boundary conditions to the antenna, and thus affect the far-field polarization characteristics of the antenna. Four designs of DC read-out interconnects are fabricated and their polarization-dependent IR responses are experimentally measured. The High Frequency Structure Simulator (HFSS) from ANSYS is used to simulate the polarization characteristics of the antenna with different read-out geometries.

Tiwari, Badri Nath

49

Estimating unbiased phenological trends by adapting site-occupancy models.  

PubMed

As a response to climate warming, many animals and plants have been found to shift phenologies, such as appearance in spring or timing of reproduction. However, traditional measures for shifts in phenology that are based on observational data likely are biased due to a large influence of population size, observational effort, starting date of a survey, or other causes that may affect the probability of detecting a species. Understanding phenological responses of species to climate change, however, requires a robust measure that could be compared among studies and study years. Here, we developed a new method for estimating arrival and departure dates based on site-occupancy models. Using simulated data, we show that our method provided virtually unbiased estimates of phenological events even if detection probability or the number of sites occupied by the species is changing over time. To illustrate the flexibility of our method, we analyzed spring arrival of two long-distance migrant songbirds and the length of the flight period of two butterfly species, using data from a long-term biodiversity monitoring program in Switzerland. In contrast to many birds that migrate short distances, the two long-distance migrant songbirds tended to postpone average spring arrival by -0.5 days per year between 1995 and 2012. Furthermore, the flight period of the short-distance-flying butterfly species apparently became even shorter over the study period, while the flight period of the longer-distance-flying butterfly species remained relatively stable. Our method could be applied to temporally and spatially extensive data from a wide range of monitoring programs and citizen science projects, to help unravel how species and communities respond to global warming. PMID:25230466

Roth, Tobias; Strebel, Nicolas; Amrhein, Valentin

2014-08-01

50

Unbiased reconstruction of a mammalian transcriptional network mediating the differential response to pathogens  

E-print Network

Models of mammalian regulatory networks controlling gene expression have been inferred from genomic data but have largely not been validated. We present an unbiased strategy to systematically perturb candidate regulators ...

Amit, Ido

51

Mutually unbiased measurements for high-dimensional time-bin based photonic states  

E-print Network

The task of measuring in two mutually unbiased bases is central to many quantum information protocols, as well as being of fundamental interest. Increasingly, there is an experimental focus on generating and controlling high-dimensional photonic states. One approach is to use the arrival time of a photon, which can be split into discrete time bins. An important problem associated with such states is the difficulty in experimentally realizing a measurement that is mutually unbiased with respect to the time-of-arrival. We propose a simple and compact scheme to measure in both the time of arrival basis and a basis that is approximately mutually unbiased with respect to the arrival time.

Thomas Brougham; Stephen M. Barnett

2013-11-12

52

An Unbiased Statistical Survey of Ibc Supernova Host Abundances  

NASA Astrophysics Data System (ADS)

Metallicity is a key parameter of the progenitors of Type Ib/c core-collapse supernovae. It has profound consequences for constraining their progenitor model and their connection to long-duration GRBs. Moreover, it constrains their delay-time distribution, which is imperative to modeling galactic chemical evolution. We employ deep follow-up observations from the LDSS-3 long-slit spectrograph of the Magellan telescopes to study a growing sample of more than two dozen Ibc host galaxies. These supernovae are not subject to bias due to the galaxy luminosity-metallicity relationship, as they were selected only from untargeted transient searches including Pan-STARRS, Nearby Supernova Factory, and the SDSS-II Supernova Survey. We employ strong line methods to determine the host galaxy oxygen abundance and are developing new statistical methods to produce an accurate understanding of the associated uncertainties, both random and systematic. We use the 2D long-slit spectra to provide additional information on the progenitor environment by exploring the abundance distribution as a function of host galaxy radius. We compare our sample to the host galaxies of SNe from targeted surveys to characterize the potential effects of bias. We compare to GRB hosts to explore the connection between Ib/c supernovae and long-duration GRB progenitors.

Sanders, Nathan; Soderberg, A. M.; Levesque, E. M.

2011-05-01

53

Encoding mutually unbiased bases in orbital angular momentum for quantum key distribution  

NASA Astrophysics Data System (ADS)

We encode mutually unbiased bases (MUBs) using the higher-dimensional orbital angular momentum (OAM) degree of freedom and illustrate how these states are encoded on a phase-only spatial light modulator (SLM). We perform (d - 1)- mutual unbiased measurements in both a classical prepare and measure scheme and on entangled photon pairs for dimensions ranging from d = 2 to 5. The calculated average error rate, mutual information and secret key rate show an increase in information capacity as well as higher generation rates as the dimension increases.

Dudley, A.; Mafu, M.; Goyal, S.; Giovannini, D.; McLaren, M.; Konrad, T.; Padgett, M. J.; Petruccione, F.; Lütkenhaus, N.; Forbes, A.

2014-02-01

54

Acceleration spectra for subduction zone earthquakes  

USGS Publications Warehouse

We estimate the source spectra of shallow earthquakes from digital recordings of teleseismic P wave groups, that is, P+pP+sP, by making frequency dependent corrections for the attenuation and for the interference of the free surface. The correction for the interference of the free surface assumes that the earthquake radiates energy from a range of depths. We apply this spectral analysis to a set of 12 subduction zone earthquakes which range in size from Ms = 6.2 to 8.1, obtaining corrected P wave acceleration spectra on the frequency band from 0.01 to 2.0 Hz. Seismic moment estimates from surface waves and normal modes are used to extend these P wave spectra to the frequency band from 0.001 to 0.01 Hz. The acceleration spectra of large subduction zone earthquakes, that is, earthquakes whose seismic moments are greater than 1027 dyn cm, exhibit intermediate slopes where u(w)???w5/4 for frequencies from 0.005 to 0.05 Hz. For these earthquakes, spectral shape appears to be a discontinuous function of seismic moment. Using reasonable assumptions for the phase characteristics, we transform the spectral shape observed for large earthquakes into the time domain to fit Ekstrom's (1987) moment rate functions for the Ms=8.1 Michoacan earthquake of September 19, 1985, and the Ms=7.6 Michoacan aftershock of September 21, 1985. -from Authors

Boatwright, J.; Choy, G.L.

1989-01-01

55

Walking in Facebook: A Case Study of Unbiased Sampling of OSNs  

Microsoft Academic Search

With more than 250 million active users, Facebook (FB) is currently one of the most important online social networks. Our goal in this paper is to obtain a representative (unbiased) sample of Facebook users by crawling its social graph. In this quest, we consider and implement several candidate techniques. Two approaches that are found to perform well are the Metropolis-Hasting

Minas Gjoka; Maciej Kurant; Carter T. Butts; Athina P. Markopoulou

2010-01-01

56

Reply to ''Comment on 'Mutually unbiased bases, orthogonal Latin squares, and hidden-variable models'''  

SciTech Connect

In this Reply to the preceding Comment by Hall and Rao [Phys. Rev. A 83, 036101 (2011)], we motivate terminology of our original paper and point out that further research is needed in order to (dis)prove the claimed link between every orthogonal Latin square of order being a power of a prime and a mutually unbiased basis.

Paterek, Tomasz [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore (Singapore); Dakic, Borivoje; Brukner, Caslav [Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Wien (Austria); Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Wien (Austria)

2011-03-15

57

A receding horizon unbiased FIR filter for discrete-time state space models  

Microsoft Academic Search

This paper concerns with a new linear finite impulse response (FIR) filter called the receding horizon unbiased FIR (RHUF) filter for the state estimation in discrete-time state space models. To obtain the RHUF filter, linearity, unbiasedness and FIR structure will be required beforehand in addition to a performance criteria of minimum variance. The RHUF filter is obtained by directly solving

Wook Hyun Kwon; Pyung Soo Kim; Soo Hee Han

2002-01-01

58

Atomic Spectra  

NSDL National Science Digital Library

This page from Hyperphysics contains images depicting the light emitted by several elements and their respective spectra. The page also provides a description of how the size of a holographic image scales with the wavelength of the light used to observe it.

Nave, Carl R.

2010-03-12

59

Atomic Spectra  

NSDL National Science Digital Library

This well-illustrated page from Hyperphysics contains the light emitted by several elements and their respective spectra as well. The page also provides a description of how the size of a holographic image scales with the wavelength of the light used to observe it.

Nave, Carl R.

2007-12-20

60

Atomic Spectra  

NSDL National Science Digital Library

In this Flash animation the user can view the atomic emission spectra (400-700nm) of eight different elements. A dragable marker allows the user to approximate the wavelength of the various spectral lines. The effect of resolution can be examined in the sodium spectrum in the region 550-600nm.

61

Weighted skewness and kurtosis unbiased by sample size and Gaussian uncertainties  

E-print Network

Central moments and cumulants are often employed to characterize the distribution of data. The skewness and kurtosis are particularly useful for the detection of outliers, the assessment of departures from normally distributed data, automated classification techniques and other applications. Robust definitions of higher order moments are more stable but might miss characteristic features of the data, as in the case of astronomical time series with rare events like stellar bursts or eclipses from binary systems. Weighting can help identify reliable measurements from uncertain or spurious outliers, so unbiased estimates of the weighted skewness and kurtosis moments and cumulants, corrected for sample-size biases, are provided under the assumption of independent data. The comparison of biased and unbiased weighted estimators is illustrated with simulations as a function of sample size, employing different data distributions and weighting schemes.

Rimoldini, Lorenzo

2014-01-01

62

The bias of the unbiased estimator: A study of the iterative application of the BLUE method  

NASA Astrophysics Data System (ADS)

The best linear unbiased estimator (BLUE) is a popular statistical method adopted to combine multiple measurements of the same observable taking into account individual uncertainties and their correlations. The method is unbiased by construction if the true uncertainties and their correlations are known, but it may exhibit a bias if uncertainty estimates are used in place of the true ones, in particular if those estimated uncertainties depend on measured values. This is the case for instance when contributions to the total uncertainty are known as relative uncertainties. In those cases, an iterative application of the BLUE method may reduce the bias of the combined measurement. The impact of the iterative approach compared to the standard BLUE application is studied for a wide range of possible values of uncertainties and their correlation in the case of the combination of two measurements.

Lista, Luca

2014-11-01

63

Test of mutually unbiased bases for six-dimensional photonic quantum systems  

PubMed Central

In quantum information, complementarity of quantum mechanical observables plays a key role. The eigenstates of two complementary observables form a pair of mutually unbiased bases (MUBs). More generally, a set of MUBs consists of bases that are all pairwise unbiased. Except for specific dimensions of the Hilbert space, the maximal sets of MUBs are unknown in general. Even for a dimension as low as six, the identification of a maximal set of MUBs remains an open problem, although there is strong numerical evidence that no more than three simultaneous MUBs do exist. Here, by exploiting a newly developed holographic technique, we implement and test different sets of three MUBs for a single photon six-dimensional quantum state (a “qusix”), encoded exploiting polarization and orbital angular momentum of photons. A close agreement is observed between theory and experiments. Our results can find applications in state tomography, quantitative wave-particle duality, quantum key distribution. PMID:24067548

D'Ambrosio, Vincenzo; Cardano, Filippo; Karimi, Ebrahim; Nagali, Eleonora; Santamato, Enrico; Marrucci, Lorenzo; Sciarrino, Fabio

2013-01-01

64

Stochastic Unbiased Minimum Mean Error Rate Algorithm for Decision Feedback Equalizers  

Microsoft Academic Search

Capitalizing on a well-known minimum mean-square error (MMSE) property for decision feedback equalization (DFE) along with the use of stochastic gradient approach, we formulate an adaptive minimum error rate (MER) algorithm for DFE over M-ary PAM channels to be named as stochastic unbiased minimum mean-error rate (SUMMER). Comparisons are made between our algorithm and existing MER algorithms in the literature.

Rainfield Yutian Yen

2007-01-01

65

Structure of the sets of mutually unbiased bases with cyclic symmetry  

NASA Astrophysics Data System (ADS)

Mutually unbiased bases that can be cyclically generated by a single unitary operator are of special interest, for they can be readily implemented in practice. We show that, for a system of qubits, finding such a generator can be cast as the problem of finding a symmetric matrix over the field {F}2 equipped with an irreducible characteristic polynomial of a given Fibonacci index. The entanglement structure of the resulting complete sets is determined by two additive matrices of the same size.

Seyfarth, U.; Sánchez-Soto, L. L.; Leuchs, G.

2014-11-01

66

Comment on ''Mutually unbiased bases, orthogonal Latin squares, and hidden-variable models''  

SciTech Connect

In a recent article Paterek, Dakic, and Brukner [Phys. Rev. A 79, 012109 (2009)] show an algorithm for generating mutually unbiased bases from sets of orthogonal Latin squares. They claim that this algorithm works for every set of orthogonal Latin squares. We show that the algorithm only works for particular sets of orthogonal Latin squares. Furthermore, the algorithm is a more readable version of work previously published [Phys. Rev. A 70, 062101 (2004)].

Hall, Joanne L.; Rao, Asha [School of Mathematical and Geospatial Sciences, RMIT University, GPO Box 2476V, Melbourne, 3001 (Australia)

2011-03-15

67

Mean king's problem with mutually unbiased bases and orthogonal Latin squares  

SciTech Connect

The mean king's problem with maximal mutually unbiased bases (MUB's) in general dimension d is investigated. It is shown that a solution of the problem exists if and only if the maximal number (d+1) of orthogonal Latin squares exists. This implies that there is no solution in d=6 or d=10 dimensions even if the maximal number of MUB's exists in these dimensions.

Hayashi, A.; Horibe, M.; Hashimoto, T. [Department of Applied Physics, Fukui University, Fukui 910-8507 (Japan)

2005-05-15

68

Unextendible Maximally Entangled Bases and Mutually Unbiased Bases in ? d ? ? d'  

NASA Astrophysics Data System (ADS)

We systematically study the unextendible maximally entangled basis in arbitrary bipartite spaces {C}d ? {C}^{d^' }} (dunbiased.

Nan, Hua; Tao, Yuan-Hong; Li, Lin-Song; Zhang, Jun

2014-08-01

69

Hierarchical unbiased group-wise registration for atlas construction and population comparison  

NASA Astrophysics Data System (ADS)

A novel hierarchical unbiased group-wise registration is developed to robustly transform each individual image towards a common space for atlas based analysis. This hierarchical group-wise registration approach consists of two main components, (1) data clustering to group similar images together and (2) unbiased group-wise registration to generate a mean image for each cluster. The mean images generated in the lower hierarchical level are regarded as the input images for the higher hierarchy. In the higher hierarchical level, these input images will be further clustered and then registered by using the same two components mentioned. This hierarchical bottom-up clustering and within-cluster group-wise registration is repeated until a final mean image for the whole population is formed. This final mean image represents the common space for all the subjects to be warped to in order for the atlas based analysis. Each individual image at the bottom of the constructed hierarchy is transformed towards the root node through concatenating all the intermediate displacement fields. In order to evaluate the performance of the proposed hierarchical registration in atlas based statistical analysis, comparisons were made with the conventional group-wise registration in detecting simulated brain atrophy as well as fractional anisotropy differences between neonates and 1-year-olds. In both cases, the proposed approach demonstrated improved sensitivity (higher t-scores) than the conventional unbiased registration approach.

Chen, Yasheng; Shen, Dinggang; Zhu, Hongtu; An, Hongyu; Gilmore, John; Lin, Weili

2009-02-01

70

atomic spectra 1 Atomic Spectra  

E-print Network

. Eisberg and Resnick: Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles, pp. 95-119, p286 Physics, pp. 88-93 (Rutherford nuclear model), 93-106 (atomic structure and electron spectra) 2. D. W. Preston and E. R. Dietz: The Art of Experimental Physics, pp. 397- 399, resolution of optical instruments

Glashausser, Charles

71

Generalized approach for using unbiased symmetric metrics with negative values: normalized mean bias factor and normalized mean absolute error factor  

EPA Science Inventory

Unbiased symmetric metrics provide a useful measure to quickly compare two datasets, with similar interpretations for both under and overestimations. Two examples include the normalized mean bias factor and normalized mean absolute error factor. However, the original formulations...

72

First unbiased spectral survey of a young and single massive protostar: CygX-N63  

NASA Astrophysics Data System (ADS)

We present an unbiased spectral survey of a unique massive protostar in the Cygnus-X region: CygX-N63, performed with the 30m IRAM telescope. We identified 48 molecules over 106 GHz of bandwidth. Two prebiotic molecules were found: CH_2NH (methanimine) and NH_2CHO (formamide) and several rare molecules, such as CF^+ (fluoromethylidynium) or PN (phosphorous nitride). The spectral profiles and the population diagrams of the molecules allowed us to identify three emission regions in the protostar: the envelope, the outflow and a hot core-like region.

Fechtenbaum, S.; Bontemps, S.

2013-11-01

73

An unbiased approach to identify endogenous substrates of "histone" deacetylase 8.  

PubMed

Despite being extensively characterized structurally and biochemically, the functional role of histone deacetylase 8 (HDAC8) has remained largely obscure due in part to a lack of known cellular substrates. Herein, we describe an unbiased approach using chemical tools in conjunction with sophisticated proteomics methods to identify novel non-histone nuclear substrates of HDAC8, including the tumor suppressor ARID1A. These newly discovered substrates of HDAC8 are involved in diverse biological processes including mitosis, transcription, chromatin remodeling, and RNA splicing and may help guide therapeutic strategies that target the function of HDAC8. PMID:25089360

Olson, David E; Udeshi, Namrata D; Wolfson, Noah A; Pitcairn, Carol Ann; Sullivan, Eric D; Jaffe, Jacob D; Svinkina, Tanya; Natoli, Ted; Lu, Xiaodong; Paulk, Joshiawa; McCarren, Patrick; Wagner, Florence F; Barker, Doug; Howe, Eleanor; Lazzaro, Fanny; Gale, Jennifer P; Zhang, Yan-Ling; Subramanian, Aravind; Fierke, Carol A; Carr, Steven A; Holson, Edward B

2014-10-17

74

Structure of the sets of mutually unbiased bases with cyclic symmetry  

E-print Network

Mutually unbiased bases that can be cyclically generated by a single unitary operator are of special interest, since they can be readily implemented in practice. We show that, for a system of qubits, finding such a generator can be cast as the problem of finding a symmetric matrix over the field $\\mathbb{F}_2$ equipped with an irreducible characteristic polynomial of a given Fibonacci index. The entanglement structure of the resulting complete sets is determined by two additive matrices of the same size.

Ulrich Seyfarth; Luis L. Sanchez-Soto; Gerd Leuchs

2014-04-11

75

New approach to finding the maximum number of mutually unbiased bases in $\\mathbb{C}^6$  

E-print Network

There has been great interest in finding sets of $m$ mutually unbiased bases which are compatible with a given space $\\mathbb{C}^d$, specially in physics due to their interesting applications in quantum information theory. Several general results have been obtained so far, but surprising results may occur for definite $(m,d)$-values. One such case that has remained an open question (the simplest case) is the one regarding the existence of $m=4$ mutually orthogonal bases for $d=6$. In the present work we introduce a new approach to the problem by translating it into an optimization procedure for a given pair $(m,d)$.

J. Batle

2013-12-14

76

Weighted skewness and kurtosis unbiased by sample size and Gaussian uncertainties  

NASA Astrophysics Data System (ADS)

Central moments and cumulants are often employed to characterize the distribution of data. The skewness and kurtosis are particularly useful for the detection of outliers, the assessment of departures from normally distributed data, automated classification techniques and other applications. Estimators of higher order moments that are robust against outliers are more stable but might miss characteristic features of the data, as in the case of astronomical time series exhibiting brief events like stellar bursts or eclipses of binary systems, while weighting can help identify reliable measurements from uncertain or spurious outliers. Furthermore, noise is an unavoidable part of most measurements and their uncertainties need to be taken properly into account during the data analysis or biases are likely to emerge in the results, including basic descriptive statistics. This work provides unbiased estimates of the weighted skewness and kurtosis moments and cumulants, corrected for biases due to sample size and Gaussian noise, under the assumption of independent data. A comparison of biased and unbiased weighted estimators is illustrated with simulations as a function of sample size and signal-to-noise ratio, employing different data distributions and weighting schemes related to measurement uncertainties and the sampling of the signal. Detailed derivations and figures of simulation results are presented in the Appendices available online.

Rimoldini, Lorenzo

2014-07-01

77

Construction of mutually unbiased bases with cyclic symmetry for qubit systems  

SciTech Connect

For the complete estimation of arbitrary unknown quantum states by measurements, the use of mutually unbiased bases has been well established in theory and experiment for the past 20 years. However, most constructions of these bases make heavy use of abstract algebra and the mathematical theory of finite rings and fields, and no simple and generally accessible construction is available. This is particularly true in the case of a system composed of several qubits, which is arguably the most important case in quantum information science and quantum computation. In this paper, we close this gap by providing a simple and straightforward method for the construction of mutually unbiased bases in the case of a qubit register. We show that our construction is also accessible to experiments, since only Hadamard and controlled-phase gates are needed, which are available in most practical realizations of a quantum computer. Moreover, our scheme possesses the optimal scaling possible, i.e., the number of gates scales only linearly in the number of qubits.

Seyfarth, Ulrich [Institut fuer Angewandte Physik, Technische Universitaet Darmstadt, Hochschulstrasse 4a, D-64289 Darmstadt (Germany); Ranade, Kedar S. [Institut fuer Quantenphysik, Universitaet Ulm, Albert-Einstein-Allee 11, D-89081 Ulm (Germany)

2011-10-15

78

The Herschel/HIFI unbiased spectral survey of the solar-mass protostar IRAS16293  

NASA Astrophysics Data System (ADS)

Unbiased spectral surveys are powerful tools to study the chemistry and the physics of star forming regions, because they can provide a complete census of the molecular content and the observed lines probe the physical structure of the source. While unbiased surveys at the millimeter and sub-millimeter wavelengths observable from ground-based telescopes have previously been performed towards several high-mass protostars, very little data exist on low-mass protostars, with only one such ground-based survey carried out towards this kind of object. However, since low-mass protostars are believed to resemble our own Sun's progenitor, the information provided by spectral surveys is crucial in order to uncover the birth mechanisms of low-mass stars and hence of our Sun. To help fill up this gap in our understanding, we carried out an almost complete spectral survey towards the solar-type protostar IRAS16293-2422 with the HIFI instrument onboard Herschel. The observations covered a range of about 700 GHz, in which a few hundreds lines were detected with more than 3? confidence interval certainty and identified. All the detected lines which were free from obvious blending effects were fitted with Gaussians to estimate their basic kinematic properties. Contrarily to what is observed in the millimeter range, no lines from complex organic molecules have been observed. In this work, we characterize the different components of IRAS16293-2422 (a known binary at least) by analyzing the numerous emission and absorption lines identified.

Bottinelli, S.; Caux, E.; Cecarelli, C.; Kahane, C.

2012-03-01

79

Sets of Mutually Unbiased Bases as Arcs in Finite Projective Planes?  

E-print Network

This note is a short elaboration of the conjecture of Saniga et al (J. Opt. B: Quantum Semiclass. 6 (2004) L19-L20) by regarding a set of mutually unbiased bases (MUBs) in a d-dimensional Hilbert space, d being a power of a prime, as an analogue of an arc in a (Desarguesian) projective plane of order d. Complete sets of MUBs thus correspond to (d+1)-arcs, i.e., ovals. The existence of two principally distinct kinds of ovals for d even and greater than four, viz. conics and non-conics, implies the existence of two qualitatively different groups of the complete sets of MUBs for the Hilbert spaces of corresponding dimensions.

Metod Saniga; Michel Planat

2004-09-27

80

Unbiased Reduced Density Matrices and Electronic Properties from Full Configuration Interaction Quantum Monte Carlo  

E-print Network

Properties that are necessarily formulated within pure (symmetric) expectation values are difficult to calculate for projector quantum Monte Carlo approaches, but are critical in order to compute many of the important observable properties of electronic systems. Here, we investigate an approach for the sampling of unbiased reduced density matrices within the Full Configuration Interaction Quantum Monte Carlo dynamic, which requires only small computational overheads. This is achieved via an independent replica population of walkers in the dynamic, sampled alongside the original population. The resulting reduced density matrices are free from systematic error (beyond those present via constraints on the dynamic itself), and can be used to compute a variety of expectation values and properties, with rapid convergence to an exact limit. A quasi-variational energy estimate derived from these density matrices is proposed as an accurate alternative to the projected estimator for multiconfigurational wavefunctions, ...

Overy, Catherine; Blunt, N S; Shepherd, James; Cleland, Deidre; Alavi, Ali

2014-01-01

81

An unbiased X-ray sampling of stars within 25 parsecs of the Sun  

NASA Technical Reports Server (NTRS)

A search of all of the Einstein Observatory IPC and HRI fields for untargeted stars in the Woolley, et al., Catalogue of the nearby stars is reported. Optical data and IPC coordinates, flux density F sub x, and luminosity L sub x, or upper limits, are tabulated for 126 single or blended systems, and HRI results for a few of them. IPC luminosity functions are derived for the systems, for 193 individual stars in the systems (with L sub x shared equally among blended components), and for 63 individual M dwarfs. These stars have relatively large X-ray flux densities that are free of interstellar extinction, because they are nearby, but they are otherwise unbiased with respect to the X-ray properties that are found in a defined small space around the Sun.

Johnson, H. M.

1985-01-01

82

Denoising PET Images Using Singular Value Thresholding and Stein's Unbiased Risk Estimate*  

PubMed Central

Image denoising is an important pre-processing step for accurately quantifying functional morphology and measuring activities of the tissues using PET images. Unlike structural imaging modalities, PET images have two difficulties: (1) the Gaussian noise model does not necessarily fit into PET imaging because the exact nature of noise propagation in PET imaging is not well known, and (2) PET images are low resolution; therefore, it is challenging to denoise them while preserving structural information. To address these two difficulties, we introduce a novel methodology for denoising PET images. The proposed method uses the singular value thresholding concept and Stein's unbiased risk estimate to optimize a soft thresholding rule. Results, obtained from 40 MRI-PET images, demonstrate that the proposed algorithm is able to denoise PET images successfully, while still maintaining the quantitative information. PMID:24505751

Bagci, Ulas; Mollura, Daniel J.

2014-01-01

83

A CURE for noisy magnetic resonance images: chi-square unbiased risk estimation.  

PubMed

n this article we derive an unbiased expression for the expected mean-squared error associated with continuously differentiable estimators of the noncentrality parameter of a chisquare random variable. We then consider the task of denoising squared-magnitude magnetic resonance image data, which are well modeled as independent noncentral chi-square random variables on two degrees of freedom. We consider two broad classes of linearly parameterized shrinkage estimators that can be optimized using our risk estimate, one in the general context of undecimated filterbank transforms, and another in the specific case of the unnormalized Haar wavelet transform. The resultant algorithms are computationally tractable and improve upon most state-of-the-art methods for both simulated and actual magnetic resonance image data. PMID:22491082

Luisier, Florian; Blu, Thierry; Wolfe, Patrick J

2012-08-01

84

Solution to the Mean King's problem with mutually unbiased bases for arbitrary levels  

E-print Network

The Mean King's problem with mutually unbiased bases is reconsidered for arbitrary d-level systems. Hayashi, Horibe and Hashimoto [Phys. Rev. A 71, 052331 (2005)] related the problem to the existence of a maximal set of d-1 mutually orthogonal Latin squares, in their restricted setting that allows only measurements of projection-valued measures. However, we then cannot find a solution to the problem when e.g., d=6 or d=10. In contrast to their result, we show that the King's problem always has a solution for arbitrary levels if we also allow positive operator-valued measures. In constructing the solution, we use orthogonal arrays in combinatorial design theory.

Gen Kimura; Hajime Tanaka; Masanao Ozawa

2006-04-13

85

FALCON: fast and unbiased reconstruction of high-density super-resolution microscopy data  

NASA Astrophysics Data System (ADS)

Super resolution microscopy such as STORM and (F)PALM is now a well known method for biological studies at the nanometer scale. However, conventional imaging schemes based on sparse activation of photo-switchable fluorescent probes have inherently slow temporal resolution which is a serious limitation when investigating live-cell dynamics. Here, we present an algorithm for high-density super-resolution microscopy which combines a sparsity-promoting formulation with a Taylor series approximation of the PSF. Our algorithm is designed to provide unbiased localization on continuous space and high recall rates for high-density imaging, and to have orders-of-magnitude shorter run times compared to previous high-density algorithms. We validated our algorithm on both simulated and experimental data, and demonstrated live-cell imaging with temporal resolution of 2.5 seconds by recovering fast ER dynamics.

Min, Junhong; Vonesch, Cédric; Kirshner, Hagai; Carlini, Lina; Olivier, Nicolas; Holden, Seamus; Manley, Suliana; Ye, Jong Chul; Unser, Michael

2014-04-01

86

FALCON: fast and unbiased reconstruction of high-density super-resolution microscopy data.  

PubMed

Super resolution microscopy such as STORM and (F)PALM is now a well known method for biological studies at the nanometer scale. However, conventional imaging schemes based on sparse activation of photo-switchable fluorescent probes have inherently slow temporal resolution which is a serious limitation when investigating live-cell dynamics. Here, we present an algorithm for high-density super-resolution microscopy which combines a sparsity-promoting formulation with a Taylor series approximation of the PSF. Our algorithm is designed to provide unbiased localization on continuous space and high recall rates for high-density imaging, and to have orders-of-magnitude shorter run times compared to previous high-density algorithms. We validated our algorithm on both simulated and experimental data, and demonstrated live-cell imaging with temporal resolution of 2.5 seconds by recovering fast ER dynamics. PMID:24694686

Min, Junhong; Vonesch, Cédric; Kirshner, Hagai; Carlini, Lina; Olivier, Nicolas; Holden, Seamus; Manley, Suliana; Ye, Jong Chul; Unser, Michael

2014-01-01

87

Optimal and unbiased FIR filtering in discrete time state space with smoothing and predictive properties  

NASA Astrophysics Data System (ADS)

We address p-shift finite impulse response optimal (OFIR) and unbiased (UFIR) algorithms for predictive filtering ( p > 0), filtering ( p = 0), and smoothing filtering ( p < 0) at a discrete point n over N neighboring points. The algorithms were designed for linear time-invariant state-space signal models with white Gaussian noise. The OFIR filter self-determines the initial mean square state function by solving the discrete algebraic Riccati equation. The UFIR one represented both in the batch and iterative Kalman-like forms does not require the noise covariances and initial errors. An example of applications is given for smoothing and predictive filtering of a two-state polynomial model. Based upon this example, we show that exact optimality is redundant when N ? 1 and still a nice suboptimal estimate can fairly be provided with a UFIR filter at a much lower cost.

Shmaliy, Yuriy S.; Ibarra-Manzano, Oscar

2012-12-01

88

Effects of corticosterone treatment and rehabilitation on the hippocampal formation of neonatal and adult rats. An unbiased stereological study  

Microsoft Academic Search

Elevations in the plasma levels of glucocorticoids are associated with cognitive impairments that have been ascribed to loss of neurons in the hippocampal formation. However, recent studies have strongly challenged this view. In order to clarify this issue, we have employed for the first time the optical fractionator and the Cavalieri principle, two unbiased stereological tools, to estimate respectively the

Nuno Sousa; Maria Dulce Madeira; Manuel M Paula-Barbosa

1998-01-01

89

Atomic-Level Characterization of the Ensemble of the A(142) Monomer in Water Using Unbiased Molecular  

E-print Network

Atomic-Level Characterization of the Ensemble of the A(1­42) Monomer in Water Using Unbiased and neurotoxic oligomers involved in Alzheimer's disease. Recent studies on the structural features of A in water the conformations accessible to A42 in explicit water solvent, under the ff99SB force field. Monitoring

Drineas, Petros

90

Galaxy and Stellar Spectra  

NSDL National Science Digital Library

In this activity students learn that galaxies shine on the basis of their intergrated stellar population, therefore, adding together different stellar spectra should reproduce the spectra of a galaxy. This activity contains an applet which allows one to add spectra of up to four different stars to produce a resultant spectra. To reproduce qualitatively a spectra of a galaxy one can add together and F main sequence star and a K Giant. The spectra are normalized by V-band luminosity.

Department, University O.

2005-06-17

91

Time-dependent tree-structured survival analysis with unbiased variable selection through permutation tests.  

PubMed

Incorporating time-dependent covariates into tree-structured survival analysis (TSSA) may result in more accurate prognostic models than if only baseline values are used. Available time-dependent TSSA methods exhaustively test every binary split on every covariate; however, this approach may result in selection bias toward covariates with more observed values. We present a method that uses unbiased significance levels from newly proposed permutation tests to select the time-dependent or baseline covariate with the strongest relationship with the survival outcome. The specific splitting value is identified using only the selected covariate. Simulation results show that the proposed time-dependent TSSA method produces tree models of equal or greater accuracy as compared to baseline TSSA models, even with high censoring rates and large within-subject variability in the time-dependent covariate. To illustrate, the proposed method is applied to data from a cohort of bipolar youths to identify subgroups at risk for self-injurious behavior. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25043382

Wallace, M L

2014-11-30

92

P7C3 and an unbiased approach to drug discovery for neurodegenerative diseases  

PubMed Central

A novel neuroprotective small molecule was discovered using a target-agnostic in vivo screen in living mice. This aminopropyl carbazole, named P7C3, is orally bioavailable, crosses the blood–brain barrier, and is non-toxic at doses several fold higher than the efficacious dose. The potency and drug-like properties of P7C3 were optimized through a medicinal chemistry campaign, providing analogues for detailed examination. Improved versions, such as (?)-P7C3-S243 and P7C3-A20, displayed neuro-protective properties in rodent models of Parkinson’s disease, amyotrophic lateral sclerosis, traumatic brain injury and age-related cognitive decline. Derivatives appended with immobilizing moieties may reveal the protein targets of the P7C3 class of neuroprotective compounds. Our results indicate that unbiased, in vivo screens might provide starting points for the development of treatments for neurodegenerative diseases as well as tools to study the biology underlying these disorders. PMID:24514864

McKnight, Steven L.; Ready, Joseph M.

2014-01-01

93

Characterization of high-dimensional entangled systems via mutually unbiased measurements.  

PubMed

Mutually unbiased bases (MUBs) play a key role in many protocols in quantum science, such as quantum key distribution. However, defining MUBs for arbitrary high-dimensional systems is theoretically difficult, and measurements in such bases can be hard to implement. We show experimentally that efficient quantum state reconstruction of a high-dimensional multipartite quantum system can be performed by considering only the MUBs of the individual parts. The state spaces of the individual subsystems are always smaller than the state space of the composite system. Thus, the benefit of this method is that MUBs need to be defined for the small Hilbert spaces of the subsystems rather than for the large space of the overall system. This becomes especially relevant where the definition or measurement of MUBs for the overall system is challenging. We illustrate this approach by implementing measurements for a high-dimensional system consisting of two photons entangled in the orbital angular momentum degree of freedom, and we reconstruct the state of this system for dimensions of the individual photons from d = 2 to 5. PMID:25166985

Giovannini, D; Romero, J; Leach, J; Dudley, A; Forbes, A; Padgett, M J

2013-04-01

94

How unbiased is non-targeted metabolomics and is targeted pathway screening the solution?  

PubMed

Metabolomics is only truly unbiased if the whole metabolome is captured. Current metabolomics technologies capture only a part of the metabolome and therefore produce inherently biased results. Important factors that introduce such bias into a metabolomic analysis may include but are not limited to, timing of sample collection, the sample collection procedure, sample processing, stabilization, stability and storage, extraction procedures, dilution of sample, type and number of analytical methods used, preferences of analytical assays for metabolites with certain physico-chemical properties, ion suppression (LC-MS), derivatization (GC-MS), sensitivity of the assay, range of reliable response and the ability to allow at least for semi-quantitative comparison. Consideration of the many computational, chemometric and biostatistical steps required to link changes in metabolite patterns to metabolic pathways and the additional bias and risks that these steps entail, brings up the question of whether or not screening for changes in known metabolic pathways using a set of validated, quantitative multiplexing LC-MS assays (targeted pathway screening, TAPAS) would be a more robust and reliable approach. Instead of non-selectively screening for changes in metabolite patterns, TAPAS screens for changes in metabolic pathways. Since such assays are designed for specific groups of metabolites, TAPAS can cover a larger number of metabolic pathways including metabolites of a wide variety of physicochemical properties and concentration ranges and thus, although based on suite of targeted assays, TAPAS may ultimately be a less biased strategy than current non-targeted metabolomics technologies. PMID:21466457

Christians, Uwe; Klawitter, Jelena; Hornberger, Andrea; Klawitter, Jost

2011-07-01

95

Orientation decoding in human visual cortex: new insights from an unbiased perspective.  

PubMed

The development of multivariate pattern analysis or brain "decoding" methods has substantially altered the field of fMRI research. Although these methods are highly sensitive to whether or not decodable information exists, the information they discover and make use of for decoding is often concealed within complex patterns of activation. This opacity of interpretation is embodied in influential studies showing that the orientation of visual gratings can be decoded from brain activity in human visual cortex with fMRI. Although these studies provided a compelling demonstration of the power of these methods, their findings were somewhat mysterious as the scanning resolution was insufficient to resolve orientation columns, i.e., orientation information should not have been accessible. Two theories have been put forth to account for this result, the hyperacuity account and the biased map account, both of which assume that small biases in fMRI voxels are the source of decodable information. In the present study, we use Hubel and Wiesel's (1972) classic ice-cube model of visual cortex to show that the orientation of gratings can be decoded from an unbiased representation. In our analysis, we identify patterns of activity elicited by the edges of the stimulus as the source of the decodable information. Furthermore, these activation patterns masquerade as a radial bias, a key element of the biased map account. This classic model thus sheds new light on the mystery behind orientation decoding by unveiling a new source of decodable information. PMID:24920640

Carlson, Thomas A

2014-06-11

96

TOWARD UNBIASED GALAXY CLUSTER MASSES FROM LINE-OF-SIGHT VELOCITY DISPERSIONS  

SciTech Connect

We study the use of red-sequence-selected galaxy spectroscopy for unbiased estimation of galaxy cluster masses by using a publicly available simulated galaxy catalog. We explore the impact of selection using galaxy color, projected separation from the cluster center, galaxy luminosity, and spectroscopic redshift. We identify and characterize each of the following sources of bias and scatter in velocity dispersion at fixed mass: the intrinsic properties of halos in the form of halo triaxiality, sampling noise, the presence of multiple kinematic populations within the cluster, and the effect of interlopers. We show that even in red-sequence and spectroscopically selected galaxy samples, the interloper fraction is significant, and that the variations in the interloper population from cluster to cluster provide the dominant contribution to the velocity dispersion scatter at fixed mass. We present measurements of the total scatter in dispersion at fixed mass as a function of the number of redshifts. Results indicate that improvements in scatter are modest beyond samples of {approx}30 redshifts per cluster. Our results show that while cluster velocity dispersions extracted from a few dozen red-sequence-selected galaxies do not provide precise masses on a single cluster basis, an ensemble of cluster velocity dispersions can be combined to produce a precise calibration of a cluster survey-mass-observable relation. Currently, disagreements in the literature on simulated subhalo velocity dispersion-mass relations place a systematic floor on velocity dispersion mass calibration at the 5% level in dispersion.

Saro, Alex; Mohr, Joseph J.; Bazin, Gurvan; Dolag, Klaus [Department of Physics, Ludwig-Maximilians-Universitaet, Scheinerstr. 1, D-81679 Muenchen (Germany)

2013-07-20

97

Unravelling the matrix effect of fresh sampled cells for in vivo unbiased FTIR determination of the absolute concentration of total lipid content of microalgae.  

PubMed

Over the past years, the substitution of the classical biochemical quantification techniques by Fourier transform infrared (FTIR) spectroscopy has been widely studied on microalgae because of its tremendous application potential for bioprocess monitoring. In the present work, mandatory aspects that have never been approached by FTIR end-users working onto fresh biomass were assessed. We demonstrated first that fresh cells' FTIR spectra main characteristics could be severely and unspecifically altered when the properties of the sampled biomass were not monitored. Microscopy indicated that important cell reorganization could occur when diminishing the cells density of the sample. Molecular probing approach suggested that such a modification could provoke an alteration of the hydrogen-bonding network of the sample. The sample heterogeneity was found to impact also the shape and intensity of the recorded FTIR bands, participating then to a matrix effect uncharacterized until now. In the second part of our study, we selected FTIR spectra not influenced by this matrix effect and the corresponding accurate calibration data obtained by the whole cell analytical procedure to elaborate an optimized total lipid quantification PLS-R model. Results demonstrated that our strategy could provide a small volume sampling (1 mL of fresh culture), rapid (within minutes), robust (physiological condition independent), and accurate (as accurate as the reference method could be) FTIR absolute quantification method to determine the fresh microalgae intracellular total lipid content. To validate our unbiased FTIR approach, a photobioprocess monitoring pipeline was developed and allowed assessing the effect of light attenuation on total lipid production by the marine microalga Nannochloropsis oculata. PMID:24788985

Coat, Rémy; Montalescot, Valeria; León, Esteban Serrano; Kucma, Delphine; Perrier, Candice; Jubeau, Sébastien; Thouand, Gérald; Legrand, Jack; Pruvost, Jérémy; Gonçalves, Olivier

2014-11-01

98

Finalizing host range determination of a weed biological control pathogen with best linear unbiased predictors and damage assessment  

Microsoft Academic Search

Colletotrichum gloeosporioides f. sp. salsolae (Penz.) Penz. & Sacc. in Penz. (CGS) is a facultative parasitic fungus being evaluated as a classical biological control\\u000a agent of Russian thistle or tumbleweed (Salsola tragus L.). In initial host range determination tests, Henderson’s mixed model equations (MME) were used to generate best linear\\u000a unbiased predictors (BLUPs) of disease severity reaction to CGS among

Dana K. BernerCraig; Craig A. Cavin

99

An unbiased method to build benchmarking sets for ligand-based virtual screening and its application to GPCRs.  

PubMed

Benchmarking data sets have become common in recent years for the purpose of virtual screening, though the main focus had been placed on the structure-based virtual screening (SBVS) approaches. Due to the lack of crystal structures, there is great need for unbiased benchmarking sets to evaluate various ligand-based virtual screening (LBVS) methods for important drug targets such as G protein-coupled receptors (GPCRs). To date these ready-to-apply data sets for LBVS are fairly limited, and the direct usage of benchmarking sets designed for SBVS could bring the biases to the evaluation of LBVS. Herein, we propose an unbiased method to build benchmarking sets for LBVS and validate it on a multitude of GPCRs targets. To be more specific, our methods can (1) ensure chemical diversity of ligands, (2) maintain the physicochemical similarity between ligands and decoys, (3) make the decoys dissimilar in chemical topology to all ligands to avoid false negatives, and (4) maximize spatial random distribution of ligands and decoys. We evaluated the quality of our Unbiased Ligand Set (ULS) and Unbiased Decoy Set (UDS) using three common LBVS approaches, with Leave-One-Out (LOO) Cross-Validation (CV) and a metric of average AUC of the ROC curves. Our method has greatly reduced the "artificial enrichment" and "analogue bias" of a published GPCRs benchmarking set, i.e., GPCR Ligand Library (GLL)/GPCR Decoy Database (GDD). In addition, we addressed an important issue about the ratio of decoys per ligand and found that for a range of 30 to 100 it does not affect the quality of the benchmarking set, so we kept the original ratio of 39 from the GLL/GDD. PMID:24749745

Xia, Jie; Jin, Hongwei; Liu, Zhenming; Zhang, Liangren; Wang, Xiang Simon

2014-05-27

100

Predicting Genetic Values: A Kernel-Based Best Linear Unbiased Prediction With Genomic Data  

PubMed Central

Genomic data provide a valuable source of information for modeling covariance structures, allowing a more accurate prediction of total genetic values (GVs). We apply the kriging concept, originally developed in the geostatistical context for predictions in the low-dimensional space, to the high-dimensional space spanned by genomic single nucleotide polymorphism (SNP) vectors and study its properties in different gene-action scenarios. Two different kriging methods [“universal kriging” (UK) and “simple kriging” (SK)] are presented. As a novelty, we suggest use of the family of Matérn covariance functions to model the covariance structure of SNP vectors. A genomic best linear unbiased prediction (GBLUP) is applied as a reference method. The three approaches are compared in a whole-genome simulation study considering additive, additive-dominance, and epistatic gene-action models. Predictive performance is measured in terms of correlation between true and predicted GVs and average true GVs of the individuals ranked best by prediction. We show that UK outperforms GBLUP in the presence of dominance and epistatic effects. In a limiting case, it is shown that the genomic covariance structure proposed by VanRaden (2008) can be considered as a covariance function with corresponding quadratic variogram. We also prove theoretically that if a specific linear relationship exists between covariance matrices for two linear mixed models, the GVs resulting from BLUP are linked by a scaling factor. Finally, the relation of kriging to other models is discussed and further options for modeling the covariance structure, which might be more appropriate in the genomic context, are suggested. PMID:21515573

Ober, Ulrike; Erbe, Malena; Long, Nanye; Porcu, Emilio; Schlather, Martin; Simianer, Henner

2011-01-01

101

Onset of Immune Senescence Defined by Unbiased Pyrosequencing of Human Immunoglobulin mRNA Repertoires  

PubMed Central

The immune system protects us from foreign substances or pathogens by generating specific antibodies. The variety of immunoglobulin (Ig) paratopes for antigen recognition is a result of the V(D)J rearrangement mechanism, while a fast and efficient immune response is mediated by specific immunoglobulin isotypes obtained through class switch recombination (CSR). To get a better understanding on how antibody-based immune protection works and how it changes with age, the interdependency between these two parameters need to be addressed. Here, we have performed an in depth analysis of antibody repertoires of 14 healthy donors representing different gender and age groups. For this task, we developed a unique pyrosequencing approach, which is able to monitor the expression levels of all immunoglobulin V(D)J recombinations of all isotypes including subtypes in an unbiased and quantitative manner. Our results show that donors have individual immunoglobulin repertoires and cannot be clustered according to V(D)J recombination patterns, neither by age nor gender. However, after incorporating isotype-specific analysis and considering CSR information into hierarchical clustering the situation changes. For the first time the donors cluster according to age and separate into young adults and elderly donors (>50). As a direct consequence, this clustering defines the onset of immune senescence at the age of fifty and beyond. The observed age-dependent reduction of CSR ability proposes a feasible explanation why reduced efficacy of vaccination is seen in the elderly and implies that novel vaccine strategies for the elderly should include the “Golden Agers”. PMID:23226220

Rubelt, Florian; Sievert, Volker; Knaust, Florian; Diener, Christian; Lim, Theam Soon; Skriner, Karl; Klipp, Edda; Reinhardt, Richard; Lehrach, Hans; Konthur, Zoltan

2012-01-01

102

An Unbiased Approach to Identifying Tau Kinases That Phosphorylate Tau at Sites Associated with Alzheimer Disease  

PubMed Central

Neurofibrillary tangles, one of the hallmarks of Alzheimer disease (AD), are composed of paired helical filaments of abnormally hyperphosphorylated tau. The accumulation of these proteinaceous aggregates in AD correlates with synaptic loss and severity of dementia. Identifying the kinases involved in the pathological phosphorylation of tau may identify novel targets for AD. We used an unbiased approach to study the effect of 352 human kinases on their ability to phosphorylate tau at epitopes associated with AD. The kinases were overexpressed together with the longest form of human tau in human neuroblastoma cells. Levels of total and phosphorylated tau (epitopes Ser(P)-202, Thr(P)-231, Ser(P)-235, and Ser(P)-396/404) were measured in cell lysates using AlphaScreen assays. GSK3?, GSK3?, and MAPK13 were found to be the most active tau kinases, phosphorylating tau at all four epitopes. We further dissected the effects of GSK3? and GSK3? using pharmacological and genetic tools in hTau primary cortical neurons. Pathway analysis of the kinases identified in the screen suggested mechanisms for regulation of total tau levels and tau phosphorylation; for example, kinases that affect total tau levels do so by inhibition or activation of translation. A network fishing approach with the kinase hits identified other key molecules putatively involved in tau phosphorylation pathways, including the G-protein signaling through the Ras family of GTPases (MAPK family) pathway. The findings identify novel tau kinases and novel pathways that may be relevant for AD and other tauopathies. PMID:23798682

Cavallini, Annalisa; Brewerton, Suzanne; Bell, Amanda; Sargent, Samantha; Glover, Sarah; Hardy, Clare; Moore, Roger; Calley, John; Ramachandran, Devaki; Poidinger, Michael; Karran, Eric; Davies, Peter; Hutton, Michael; Szekeres, Philip; Bose, Suchira

2013-01-01

103

Unbiased Transcriptional Comparisons of Generalist and Specialist Herbivores Feeding on Progressively Defenseless Nicotiana attenuata Plants  

PubMed Central

Background Herbivore feeding elicits dramatic increases in defenses, most of which require jasmonate (JA) signaling, and against which specialist herbivores are thought to be better adapted than generalist herbivores. Unbiased transcriptional analyses of how neonate larvae cope with these induced plant defenses are lacking. Methodology/Principal Findings We created cDNA microarrays for Manduca sexta and Heliothis virescens separately, by spotting normalized midgut-specific cDNA libraries created from larvae that fed for 24 hours on MeJA-elicited wild-type (WT) Nicotiana attenuata plants. These microarrays were hybridized with labeled probes from neonates that fed for 24 hours on WT and isogenic plants progressively silenced in JA-mediated defenses (N: nicotine; N/PI: N and trypsin protease inhibitors; JA: all JA-mediated defenses). H. virescens neonates regulated 16 times more genes than did M. sexta neonates when they fed on plants silenced in JA-mediated defenses, and for both species, the greater the number of defenses silenced in the host plant (JA > N/PI > N), the greater were the number of transcripts regulated in the larvae. M. sexta larvae tended to down-regulate while H. virescens larvae up- and down-regulated transcripts from the same functional categories of genes. M. sexta larvae regulated transcripts in a diet-specific manner, while H. virescens larvae regulated a similar suite of transcripts across all diet types. Conclusions/Significance The observations are consistent with the expectation that specialists are better adapted than generalist herbivores to the defense responses elicited in their host plants by their feeding. While M. sexta larvae appear to be better adapted to N. attenuata's defenses, some of the elicited responses remain effective defenses against both herbivore species. The regulated genes provide novel insights into larval adaptations to N. attenuata's induced defenses, and represent potential targets for plant-mediated RNAi to falsify hypotheses about the process of adaptation. PMID:20090945

Govind, Geetha; Mittapalli, Omprakash; Griebel, Thasso; Allmann, Silke; Bocker, Sebastian; Baldwin, Ian Thomas

2010-01-01

104

Unbiased estimation of chloroplast number in mesophyll cells: advantage of a genuine three-dimensional approach  

PubMed Central

Chloroplast number per cell is a frequently examined quantitative anatomical parameter, often estimated by counting chloroplast profiles in two-dimensional (2D) sections of mesophyll cells. However, a mesophyll cell is a three-dimensional (3D) structure and this has to be taken into account when quantifying its internal structure. We compared 2D and 3D approaches to chloroplast counting from different points of view: (i) in practical measurements of mesophyll cells of Norway spruce needles, (ii) in a 3D model of a mesophyll cell with chloroplasts, and (iii) using a theoretical analysis. We applied, for the first time, the stereological method of an optical disector based on counting chloroplasts in stacks of spruce needle optical cross-sections acquired by confocal laser-scanning microscopy. This estimate was compared with counting chloroplast profiles in 2D sections from the same stacks of sections. Comparing practical measurements of mesophyll cells, calculations performed in a 3D model of a cell with chloroplasts as well as a theoretical analysis showed that the 2D approach yielded biased results, while the underestimation could be up to 10-fold. We proved that the frequently used method for counting chloroplasts in a mesophyll cell by counting their profiles in 2D sections did not give correct results. We concluded that the present disector method can be efficiently used for unbiased estimation of chloroplast number per mesophyll cell. This should be the method of choice, especially in coniferous needles and leaves with mesophyll cells with lignified cell walls where maceration methods are difficult or impossible to use. PMID:24336344

Kubinova, Zuzana

2014-01-01

105

Degree Spectra of Alexandra A.  

E-print Network

Degree Spectra of Structures Alexandra A. Soskova DEGREE SPECTRA OF STRUCTURES CO-SPECTRA OF STRUCTURES PROPERTIES OF THE DEGREE SPECTRA AND CO-SPECTRA RELATIVE SPECTRA OF STRUCTURES PROPERTIES OF RELATIVE SPECTRA Degree Spectra of Structures Alexandra A. Soskova Faculty of Mathematics and Computer

Haase, Markus

106

Night Spectra Quest.  

ERIC Educational Resources Information Center

Presents the Night Spectra Quest, a pocket-sized chart that identifies in color the spectra of all the common night lights and has an integrally mounted, holographic diffraction grating to look through. (JRH)

Jacobs, Stephen

1995-01-01

107

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES  

E-print Network

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES MINIMAL PAIRS QUASI-MINIMAL DEGREE Minimal for Joint Spectra #12;DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES MINIMAL PAIRS QUASI-MINIMAL DEGREE DEGREE SPECTRA OF STRUCTURES Degree Spectra of Structures Let A = (N; R1, . . . , Rk

Soskova, Alexandra A.

108

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES  

E-print Network

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES PROPERTIES OF JOINT SPECTRA Properties of the Joint Spectra of Sequence of Structures Alexandra A. Soskova Department of Mathematics and Computer of Structures #12;DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES PROPERTIES OF JOINT SPECTRA

Soskova, Alexandra A.

109

Unbiased Estimate of Dark Energy Density from Type Ia Supernova Data  

NASA Astrophysics Data System (ADS)

Type Ia supernovae (SNe Ia) are currently the best probes of the dark energy in the universe. To constrain the nature of dark energy, we assume a flat universe and that the weak energy condition is satisfied, and we allow the density of dark energy, ?X(z), to be an arbitrary function of redshift. Using simulated data from a space-based SN pencil-beam survey, we find that by optimizing the number of parameters used to parameterize the dimensionless dark energy density, f(z)=?X(z)/?X(z=0), we can obtain an unbiased estimate of both f(z) and the fractional matter density of the universe, ?m. A plausible SN pencil-beam survey (with a square degree field of view and for an observational duration of 1 yr) can yield about 2000 SNe Ia with 0<=z<=2. Such a survey in space would yield SN peak luminosities with a combined intrinsic and observational dispersion of ?(mint)=0.16 mag. We find that for such an idealized survey, ?m can be measured to 10% accuracy, and the dark energy density can be estimated to ~20% to z~1.5, and ~20%-40% to z~2, depending on the time dependence of the true dark energy density. Dark energy densities that vary more slowly can be more accurately measured. For the anticipated Supernova/Acceleration Probe (SNAP) mission, ?m can be measured to 14% accuracy, and the dark energy density can be estimated to ~20% to z~1.2. Our results suggest that SNAP may gain much sensitivity to the time dependence of the dark energy density and ?m by devoting more observational time to the central pencil-beam fields to obtain more SNe Ia at z>1.2. We use both a maximum likelihood analysis and a Monte Carlo analysis (when appropriate) to determine the errors of estimated parameters. We find that the Monte Carlo analysis gives a more accurate estimate of the dark energy density than the maximum likelihood analysis.

Wang, Yun; Lovelace, Geoffrey

2001-12-01

110

A novel unbiased proteomic approach to detect the reactivity of cerebrospinal fluid in neurological diseases.  

PubMed

Neurodegenerative diseases, such as multiple sclerosis represent global health issues. Accordingly, there is an urgent need to understand the pathogenesis of this and other central nervous system disorders, so that more effective therapeutics can be developed. Cerebrospinal fluid is a potential source of important reporter molecules released from various cell types as a result of central nervous system pathology. Here, we report the development of an unbiased approach for the detection of reactive cerebrospinal fluid molecules and target brain proteins from patients with multiple sclerosis. To help identify molecules that may serve as clinical biomarkers for multiple sclerosis, we have biotinylated proteins present in the cerebrospinal fluid and tested their reactivity against brain homogenate as well as myelin and myelin-axolemmal complexes. Proteins were separated by two-dimensional gel electrophoresis, blotted onto membranes and probed separately with biotinylated unprocessed cerebrospinal fluid samples. Protein spots that reacted to two or more multiple sclerosis-cerebrospinal fluids were further analyzed by matrix assisted laser desorption ionization-time-of-flight time-of-flight mass spectrometry. In addition to previously reported proteins found in multiple sclerosis cerebrospinal fluid, such as ?? crystallin, enolase, and 14-3-3-protein, we have identified several additional molecules involved in mitochondrial and energy metabolism, myelin gene expression and/or cytoskeletal organization. These include aspartate aminotransferase, cyclophilin-A, quaking protein, collapsin response mediator protein-2, ubiquitin carboxy-terminal hydrolase L1, and cofilin. To further validate these findings, the cellular expression pattern of collapsin response mediator protein-2 and ubiquitin carboxy-terminal hydrolase L1 were investigated in human chronic-active MS lesions by immunohistochemistry. The observation that in multiple sclerosis lesions phosphorylated collapsin response mediator protein-2 was increased, whereas Ubiquitin carboxy-terminal hydrolase L1 was down-regulated, not only highlights the importance of these molecules in the pathology of this disease, but also illustrates the use of our approach in attempting to decipher the complex pathological processes leading to multiple sclerosis and other neurodegenerative diseases. PMID:21421798

Menon, Krishnakumar N; Steer, David L; Short, Martin; Petratos, Steven; Smith, Ian; Bernard, Claude C A

2011-06-01

111

THE OPTICALLY UNBIASED GAMMA-RAY BURST HOST (TOUGH) SURVEY. I. SURVEY DESIGN AND CATALOGS  

SciTech Connect

Long-duration gamma-ray bursts (GRBs) are powerful tracers of star-forming galaxies. We have defined a homogeneous subsample of 69 Swift GRB-selected galaxies spanning a very wide redshift range. Special attention has been devoted to making the sample optically unbiased through simple and well-defined selection criteria based on the high-energy properties of the bursts and their positions on the sky. Thanks to our extensive follow-up observations, this sample has now achieved a comparatively high degree of redshift completeness, and thus provides a legacy sample, useful for statistical studies of GRBs and their host galaxies. In this paper, we present the survey design and summarize the results of our observing program conducted at the ESO Very Large Telescope (VLT) aimed at obtaining the most basic properties of galaxies in this sample, including a catalog of R and K{sub s} magnitudes and redshifts. We detect the host galaxies for 80% of the GRBs in the sample, although only 42% have K{sub s} -band detections, which confirms that GRB-selected host galaxies are generally blue. The sample is not uniformly blue, however, with two extremely red objects detected. Moreover, galaxies hosting GRBs with no optical/NIR afterglows, whose identification therefore relies on X-ray localizations, are significantly brighter and redder than those with an optical/NIR afterglow. This supports a scenario where GRBs occurring in more massive and dusty galaxies frequently suffer high optical obscuration. Our spectroscopic campaign has resulted in 77% now having redshift measurements, with a median redshift of 2.14 {+-} 0.18. TOUGH alone includes 17 detected z > 2 Swift GRB host galaxies suitable for individual and statistical studies-a substantial increase over previous samples. Seven hosts have detections of the Ly{alpha} emission line and we can exclude an early indication that Ly{alpha} emission is ubiquitous among GRB hosts, but confirm that Ly{alpha} is stronger in GRB-selected galaxies than in flux-limited samples of Lyman break galaxies.

Hjorth, Jens; Malesani, Daniele; Fynbo, Johan P. U.; Kruehler, Thomas; Milvang-Jensen, Bo; Watson, Darach [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark); Jakobsson, Pall; Schulze, Steve [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik (Iceland); Jaunsen, Andreas O. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Gorosabel, Javier [Instituto de Astrofisica de Andalucia (IAA-CSIC), P.O. Box 03004, E-18080 Granada (Spain); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Michalowski, Michal J. [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Moller, Palle [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching by Muenchen (Germany); Tanvir, Nial R., E-mail: jens@dark-cosmology.dk [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

2012-09-10

112

Novel unbiased equations to calculate triglyceride-rich lipoprotein cholesterol from routine non-fasting lipids  

PubMed Central

Background Non-fasting triglyceride-rich lipoproteins cholesterol (TRL-C) contributes to cardiovascular risk, in that it includes remnant cholesterol (RC). TRL-C is computed as total C - [LDL-C?+?HDL-C]. Such calculation applies only if LDL-C is directly measured, or obtained from a non-Friedewald’s formula, a method as yet never benchmarked against independent markers of TRL burden. Methods The Discriminant Ratio (DR) methodology was used in 120 type 2 diabetic patients in order: (i) to compute TRL-C from non-fasting lipids; (ii) to establish the performance of TRL-C and TRL-C/apoA-I (vs. TG-based markers) to grade TRLs and atherogenic dyslipidemia (AD); and (iii) to relate TRL-C with non-fasting TG. Results Depending on apoB100 availability, TRL-C (mg/dL) can be derived from non-fasting lipids in two ways: (a) total cholesterol (TC) - [(0.0106 * TC - 0.0036 * TG?+?0.017 * apoB100 - 0.27) * 38.6] - HDL-C; and (b) TC - [(0.0106 * TC - 0.0036 * TG?+?0.017 * [0.65 * (TC - HDL-C)?+?6.3] - 0.27) * 38.6] - HDL-C. Discrimination between log[TG] and TRL-C was similar (DR 0.94 and 0.84, respectively), whereas that of log[TG]/HDL-C was better than TRL-C/apoA-I (DR 1.01 vs. 0.65; p 0.0482). All Pearson’s correlations between pairs reached unity, allowing formulation of two unbiased equivalence equations: (a) TRL-C?=?97.8 * log[TG] - 181.9; and (b) TRL-C/apoA-I?=?8.15 * (log[TG]/HDL-C) - 0.18. Conclusions TRL-C and log[TG] are as effective and interchangeable for assessing remnant atherogenic particles. For grading TRL-AD, it is best to use log[TG]/HDL-C, inherently superior to TRL-C/apoA-I, while measuring the same underlying variable. PMID:24612479

2014-01-01

113

Statistical Properties of Maximum Likelihood Estimators of Power Law Spectra Information  

NASA Technical Reports Server (NTRS)

A simple power law model consisting of a single spectral index, sigma(sub 2), is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at the knee energy, E(sub k), to a steeper spectral index sigma(sub 2) greater than sigma(sub 1) above E(sub k). The maximum likelihood (ML) procedure was developed for estimating the single parameter sigma(sub 1) of a simple power law energy spectrum and generalized to estimate the three spectral parameters of the broken power law energy spectrum from simulated detector responses and real cosmic-ray data. The statistical properties of the ML estimator were investigated and shown to have the three desirable properties: (Pl) consistency (asymptotically unbiased), (P2) efficiency (asymptotically attains the Cramer-Rao minimum variance bound), and (P3) asymptotically normally distributed, under a wide range of potential detector response functions. Attainment of these properties necessarily implies that the ML estimation procedure provides the best unbiased estimator possible. While simulation studies can easily determine if a given estimation procedure provides an unbiased estimate of the spectra information, and whether or not the estimator is approximately normally distributed, attainment of the Cramer-Rao bound (CRB) can only be ascertained by calculating the CRB for an assumed energy spectrum- detector response function combination, which can be quite formidable in practice. However, the effort in calculating the CRB is very worthwhile because it provides the necessary means to compare the efficiency of competing estimation techniques and, furthermore, provides a stopping rule in the search for the best unbiased estimator. Consequently, the CRB for both the simple and broken power law energy spectra are derived herein and the conditions under which they are stained in practice are investigated.

Howell, L. W., Jr.

2003-01-01

114

DEGREE SPECTRA OF STRUCTURES RELATIVE SPECTRA OF STRUCTURES  

E-print Network

DEGREE SPECTRA OF STRUCTURES RELATIVE SPECTRA OF STRUCTURES PROPERTIES OF RELATIVE SPECTRA Degree Spectra of Structures Alexandra A. Soskova Faculty of Mathematics and Computer Science Sofia University Leeds Logic Seminar Alexandra A. Soskova Degree Spectra of Structures #12;DEGREE SPECTRA OF STRUCTURES

Soskova, Alexandra A.

115

Spectra of stable sonoluminescence  

NASA Astrophysics Data System (ADS)

The continuous emission of picosecond pulses of light has been observed to originate from a bubble trapped at the pressure antinode of a resonant sound field in water and in water/glycerin mixtures. The spectra of this light in several solutions has been measured with a scanning monochrometer/photomultiplier detector system. The spectra are broadband and show strong emission in the UV region. A comparison of this measurement to two other independently produced spectra is made. The spectra are also modeled by a blackbody radiation distribution to determine an effective blackbody temperature and a size is deduced as if Sonoluminescence were characterized by blackbody radiation.

Lewis, Stephen D.

1992-12-01

116

Identification and characterization of Highlands J virus from a Mississippi sandhill crane using unbiased next-generation sequencing  

USGS Publications Warehouse

Advances in massively parallel DNA sequencing platforms, commonly termed next-generation sequencing (NGS) technologies, have greatly reduced time, labor, and cost associated with DNA sequencing. Thus, NGS has become a routine tool for new viral pathogen discovery and will likely become the standard for routine laboratory diagnostics of infectious diseases in the near future. This study demonstrated the application of NGS for the rapid identification and characterization of a virus isolated from the brain of an endangered Mississippi sandhill crane. This bird was part of a population restoration effort and was found in an emaciated state several days after Hurricane Isaac passed over the refuge in Mississippi in 2012. Post-mortem examination had identified trichostrongyliasis as the possible cause of death, but because a virus with morphology consistent with a togavirus was isolated from the brain of the bird, an arboviral etiology was strongly suspected. Because individual molecular assays for several known arboviruses were negative, unbiased NGS by Illumina MiSeq was used to definitively identify and characterize the causative viral agent. Whole genome sequencing and phylogenetic analysis revealed the viral isolate to be the Highlands J virus, a known avian pathogen. This study demonstrates the use of unbiased NGS for the rapid detection and characterization of an unidentified viral pathogen and the application of this technology to wildlife disease diagnostics and conservation medicine.

Ip, Hon S.; Wiley, Michael R.; Long, Renee; Gustavo, Palacios; Shearn-Bochsler, Valerie; Whitehouse, Chris A.

2014-01-01

117

Identification and characterization of Highlands J virus from a Mississippi sandhill crane using unbiased next-generation sequencing.  

PubMed

Advances in massively parallel DNA sequencing platforms, commonly termed next-generation sequencing (NGS) technologies, have greatly reduced time, labor, and cost associated with DNA sequencing. Thus, NGS has become a routine tool for new viral pathogen discovery and will likely become the standard for routine laboratory diagnostics of infectious diseases in the near future. This study demonstrated the application of NGS for the rapid identification and characterization of a virus isolated from the brain of an endangered Mississippi sandhill crane. This bird was part of a population restoration effort and was found in an emaciated state several days after Hurricane Isaac passed over the refuge in Mississippi in 2012. Post-mortem examination had identified trichostrongyliasis as the possible cause of death, but because a virus with morphology consistent with a togavirus was isolated from the brain of the bird, an arboviral etiology was strongly suspected. Because individual molecular assays for several known arboviruses were negative, unbiased NGS by Illumina MiSeq was used to definitively identify and characterize the causative viral agent. Whole genome sequencing and phylogenetic analysis revealed the viral isolate to be the Highlands J virus, a known avian pathogen. This study demonstrates the use of unbiased NGS for the rapid detection and characterization of an unidentified viral pathogen and the application of this technology to wildlife disease diagnostics and conservation medicine. PMID:24880070

Ip, Hon S; Wiley, Michael R; Long, Renee; Palacios, Gustavo; Shearn-Bochsler, Valerie; Whitehouse, Chris A

2014-09-01

118

Spectra from Space  

NSDL National Science Digital Library

This site from the Exploratorium provides information on telescopes and observatories such as the Hubble Space Telescope that are being used to study spectra from space. Gamma-ray, x-ray, ultraviolet, and infrared spectra are all examined. The purpose and discoveries made by each observatory are included along with related hands-on activities like a liquid crystal IR detector activity.

Felter, Neil

2008-05-13

119

Libraries of Stellar Spectra  

NSDL National Science Digital Library

This is a guide to online and abstract libraries of stellar spectra. This reference list also includes information about the spectra of Late-M, L, and T Dwarf stars, Morgan-Keenan spectral classification, the solar spectrum, spectrophotometric atlases, and automated and neural network classification.

2005-04-25

120

Myths and Truths Concerning Estimation of Power Spectra  

E-print Network

It is widely believed that maximum likelihood estimators must be used to provide optimal estimates of power spectra. Since such estimators require require of order N_d^3 operations they are computationally prohibitive for N_d greater than a few tens of thousands. Because of this, a large and inhomogeneous literature exists on approximate methods of power spectrum estimation. These range from manifestly sub-optimal, but computationally fast methods, to near optimal but computationally expensive methods. Furthermore, much of this literature concentrates on the power spectrum estimates rather than the equally important problem of deriving an accurate covariance matrix. In this paper, I consider the problem of estimating the power spectrum of cosmic microwave background (CMB) anisotropies from large data sets. Various analytic results on power spectrum estimators are derived, or collated from the literature, and tested against numerical simulations. An unbiased hybrid estimator is proposed that combines a maximum...

Efstathiou, G P

2004-01-01

121

Action spectra again?  

PubMed

Action spectroscopy has a long history and is of central importance to photobiological studies. Action spectra were among the first assays to point to chlorophyll as the molecule most responsible for plant growth and to DNA as the genetic material. It is useful to construct action spectra early in the investigation of new areas of photobiological research in an attempt to determine the wavelength limits of the radiation region causing the studied response. But due to the severe absorption of ultraviolet (UV) radiation by biological samples, UV action spectra were first limited to small cells (bacteria and fungi). Advances in techniques (e.g. single cell culture) and analysis allowed accurate action spectra to be reported even for mammalian cells. But precise analytical action spectra are often difficult to obtain when large, pigmented, or groups of cells are investigated. Here some action spectra are limited in interpretation and merely supply a wavelength vs effect curve. When polychromatic sources are employed, the interpretation of action spectra is even more complex and formidable. But such polychromatic action spectra can be more directly related to ambient responses. Since precise action spectra usually require the completion of a relatively large number of careful experiments using somewhat sophisticated equipment over a range of at least six wavelengths, they are often not pursued. But they remain central to the elucidation of the effect being studied. The worldwide community has agreed that stratospheric ozone is depleting, with the possibility of a consequent rise in the amount of UV-B (290-320 nm) reaching the earth's surface. It is therefore essential that new action spectra be completed for UV-B effects on a large variety of responses of human, animal, and aquatic plant systems. Combining these action spectra with the known amounts of UV-B reaching the biosphere can give rise to solar UV effectiveness spectra that, in turn, can give rise to estimates of effect. Preliminary estimates suggest that ozone layer depletion may seriously impact such important biological end-points as skin cancer, cataracts, the immune system, crop yields, and oceanic phytoplankton. So action spectra continue to play a central role in important photobiological research. PMID:1798760

Coohill, T P

1991-11-01

122

Spectra over complex terrain  

SciTech Connect

Spectra have been measured over land downwind of a water surface, over hilltops and escarpments, and over rolling farmland. The following hypotheses can be used to explain the differences between these spectra. (1) For wavelengths short compared to the fetch over the new terrain, spectral densities are in equilibrium with the new terrain. (2) For wavelengths long compared to this fetch, spectral densities remain unchanged if the ground is horizontal. If the flow is over a steep hill, the low-frequency structure is modified by distortion of the mean flow, with the longitudinal component losing energy relative to the lateral and vertical components. Because vertical-velocity spectra contain relatively less low-frequency energy than horizontal-velocity spectra, energetic vertical-velocity fluctuations tend to be in equilibrium with local terrain.

Panofsky, H.A.; Larko, D.; Lipschutz, R.; Stone, G.

1981-01-01

123

Revisiting AFLP fingerprinting for an unbiased assessment of genetic structure and differentiation of taurine and zebu cattle  

PubMed Central

Background Descendants from the extinct aurochs (Bos primigenius), taurine (Bos taurus) and zebu cattle (Bos indicus) were domesticated 10,000 years ago in Southwestern and Southern Asia, respectively, and colonized the world undergoing complex events of admixture and selection. Molecular data, in particular genome-wide single nucleotide polymorphism (SNP) markers, can complement historic and archaeological records to elucidate these past events. However, SNP ascertainment in cattle has been optimized for taurine breeds, imposing limitations to the study of diversity in zebu cattle. As amplified fragment length polymorphism (AFLP) markers are discovered and genotyped as the samples are assayed, this type of marker is free of ascertainment bias. In order to obtain unbiased assessments of genetic differentiation and structure in taurine and zebu cattle, we analyzed a dataset of 135 AFLP markers in 1,593 samples from 13 zebu and 58 taurine breeds, representing nine continental areas. Results We found a geographical pattern of expected heterozygosity in European taurine breeds decreasing with the distance from the domestication centre, arguing against a large-scale introgression from European or African aurochs. Zebu cattle were found to be at least as diverse as taurine cattle. Western African zebu cattle were found to have diverged more from Indian zebu than South American zebu. Model-based clustering and ancestry informative markers analyses suggested that this is due to taurine introgression. Although a large part of South American zebu cattle also descend from taurine cows, we did not detect significant levels of taurine ancestry in these breeds, probably because of systematic backcrossing with zebu bulls. Furthermore, limited zebu introgression was found in Podolian taurine breeds in Italy. Conclusions The assessment of cattle diversity reported here contributes an unbiased global view to genetic differentiation and structure of taurine and zebu cattle populations, which is essential for an effective conservation of the bovine genetic resources. PMID:24739206

2014-01-01

124

Toward unbiased determination of the redshift evolution of Lyman-alpha forest clouds  

NASA Technical Reports Server (NTRS)

The possibility of using D(sub A), the mean depression of a quasar spectrum due to Ly-alpha forest absorption, to study the number density evolution of the Ly-alpha forest clouds is examined in some detail. Current D(sub A) measurements are made against a continuum that is a power-law extrapolation from the continuum longward of Ly-alpha emission. Compared to the line-counting approach, the D(sub A)-method has the advantage that the D(sub A) measurements are not affected by line-blending effects. However, we find using low-redshift quasar spectra obtained with the Hubble Space Telescope (HST), where the true continuum in the Ly-alpha forest can be estimated fairly reliably because of the much lower density of the Ly-alpha forest lines, that the extrapolated continuum often deviates systematically from the true continuum in the forest region. Such systematic continuum errors introduce large errors in the D(sub A) measurements. The current D(sub A) measurements may also be significantly biased by the possible presence of the Gunn-Peterson absorption. We propose a modification to the existing D(sub A)-method, namely, to measure D(sub A) against a locally established continuum in the Ly-alpha forest. Under conditions that the quasar spectrum has good resolution and S/N to allow for a reliable estimate of the local continuum in the Ly-alpha forest, the modified D(sub A) measurements should be largely free of the systematic uncertainties suffered by the existing D(sub A) measurements. We also introduce a formalism based on the work of Zuo (1993) to simplify the application of the D(sub A)-method(s) to real data. We discuss the merits and limitations of the modified D(sub A)-method, and conclude that it is a useful alternative. Our findings that the extrapolated continuum from longward of Ly-alpha emission often deviates systematically from the true continuum in the Ly-alpha forest present a major problem in the study of the Gunn-Peterson absorption.

Lu, Limin; Zuo, Lin

1994-01-01

125

The absolute number of nerve cells in substantia nigra in normal subjects and in patients with Parkinson's disease estimated with an unbiased stereological method  

Microsoft Academic Search

Using an unbiased stereological technique, the total numbers of pigmented and non-pigmented neurons were estimated in the substantia nigra of seven patients with Parkinson's disease and seven control patients. Compared with the controls, in which the average total number of pigmented neurons was 550,000, the number of neurons was reduced by 66% in the patients. The average total number of

B Pakkenberg; A Møller; H J Gundersen; A Mouritzen Dam; H Pakkenberg

1991-01-01

126

Statistical Properties of Maximum Likelihood Estimators of Power Law Spectra Information  

NASA Technical Reports Server (NTRS)

A simple power law model consisting of a single spectral index, a is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at the knee energy, E(sub k), to a steeper spectral index alpha(sub 2) greater than alpha(sub 1) above E(sub k). The Maximum likelihood (ML) procedure was developed for estimating the single parameter alpha(sub 1) of a simple power law energy spectrum and generalized to estimate the three spectral parameters of the broken power law energy spectrum from simulated detector responses and real cosmic-ray data. The statistical properties of the ML estimator were investigated and shown to have the three desirable properties: (P1) consistency (asymptotically unbiased). (P2) efficiency asymptotically attains the Cramer-Rao minimum variance bound), and (P3) asymptotically normally distributed, under a wide range of potential detector response functions. Attainment of these properties necessarily implies that the ML estimation procedure provides the best unbiased estimator possible. While simulation studies can easily determine if a given estimation procedure provides an unbiased estimate of the spectra information, and whether or not the estimator is approximately normally distributed, attainment of the Cramer-Rao bound (CRB) can only he ascertained by calculating the CRB for an assumed energy spectrum-detector response function combination, which can be quite formidable in practice. However. the effort in calculating the CRB is very worthwhile because it provides the necessary means to compare the efficiency of competing estimation techniques and, furthermore, provides a stopping rule in the search for the best unbiased estimator. Consequently, the CRB for both the simple and broken power law energy spectra are derived herein and the conditions under which they are attained in practice are investigated. The ML technique is then extended to estimate spectra information from an arbitrary number of astrophysics data sets produced by vastly different science instruments. This theory and its successful implementation will facilitate the interpretation of spectral information from multiple astrophysics missions and thereby permit the derivation of superior spectral parameter estimates based on the combination of data sets.

Howell, L. W.

2002-01-01

127

WebSpectra  

NSDL National Science Digital Library

This site, created by Barry C. Fam and Craig A. Merlic of the University of California - Los Angeles, was established to provide chemistry students with a library of spectroscopy problems. Interpretation of spectra is a technique that requires practice - this site provides 1H NMR and 13C NMR, DEPT, COSY and IR spectra of various compounds for students to interpret. Hopefully, these problems will provide a useful resource to better understand spectroscopy. The page was given a "Top 5% Chemistry Site" award for its usefulness and content. This is a great resource for anyone interested in either biochemistry or chemistry.

Fam, Barry C.; Merlic, Craig A.

2009-05-07

128

Unbiased probing of the entire hepatitis C virus life cycle identifies clinical compounds that target multiple aspects of the infection  

PubMed Central

Over 170 million people are chronically infected by the hepatitis C virus (HCV) and at risk for dying from liver cirrhosis and hepatocellular carcinoma. Current therapy is expensive, associated with significant side effects, and often ineffective. Discovery of antiviral compounds against HCV traditionally involves a priori target identification followed by biochemical screening and confirmation in cell-based replicon assays. Typically, this results in the discovery of compounds that address a few predetermined targets and are prone to select for escape variants. To attempt to identify antiviral compounds with broad target specificity, we developed an unbiased cell-based screening system involving multiple rounds of infection in a 96-well format. Analysis of a publicly available library of 446 clinically approved drugs identified 33 compounds that targeted both known and previously unexplored aspects of HCV infection, including entry, replication, and assembly. Discovery of novel viral and cellular targets in this manner will broaden the therapeutic armamentarium against this virus, allowing for the development of drug mixtures that should reduce the likelihood of mutational escape. PMID:19995961

Gastaminza, Pablo; Whitten-Bauer, Christina; Chisari, Francis V.

2009-01-01

129

Parmeterization of spectra  

NASA Technical Reports Server (NTRS)

Following reception and analog to digital conversion (A/D) conversion, atmospheric radar backscatter echoes need to be processed so as to obtain desired information about atmospheric processes and to eliminate or minimize contaminating contributions from other sources. Various signal processing techniques have been implemented at mesosphere-stratosphere-troposphere (MST) radar facilities to estimate parameters of interest from received spectra. Such estimation techniques need to be both accurate and sufficiently efficient to be within the capabilities of the particular data-processing system. The various techniques used to parameterize the spectra of received signals are reviewed herein. Noise estimation, electromagnetic interference, data smoothing, correlation, and the Doppler effect are among the specific points addressed.

Cornish, C. R.

1983-01-01

130

Using propensity score matching to estimate an "unbiased effect-size" between women's employment and partner violence in Tanzania.  

PubMed

Estimates of the effect of employment on women's risk of partner violence in cross-sectional studies are subject to potential "self-selection bias." Women's personal choice of whether to pursue employment or not may create fundamental differences between the group of women who are employed and those who are not employed that standard regression methods cannot account for even after adjusting for confounding. The aim of this study is to demonstrate the utility of propensity score matching (PSM), a technique used widely in econometrics, to address this bias in cross-sectional studies. We use PSM to estimate an unbiased effect-size of women's employment on their risk of experiencing partner violence in urban and rural Tanzania using data from the 2010 Tanzania Demographic and Health Survey (DHS). Three different measures of women's employment were analyzed: whether they had engaged in any productive work outside of the home in the past year, whether they received payment in cash for this productive work, and whether their employment was stable. Women who worked outside of the home were significantly different from those who did not. In both urban and rural Tanzania, women's risk of violence appears higher among women who worked in the past year than among those who did not, even after using PSM to account for underlying differences in these two groups of women. Being paid in cash reversed this effect in rural areas whereas stability of employment reduced this risk in urban centers. The estimated size of effect varied by type of matching estimator, but the direction of the association remained largely consistent. This study's findings suggest substantial self-selection into employment. PSM methods, by compensating for this bias, appear to be a useful tool for estimating the relationship between women's employment and partner violence in cross-sectional studies. PMID:24729130

Vyas, Seema; Heise, Lori

2014-11-01

131

Unbiased fitting of B335 dust continuum observations: approach and evidence for variation of grain properties with position  

NASA Astrophysics Data System (ADS)

We present the first published unbiased, automated approach to fitting infrared observations of interstellar dust clouds for the purposes of constraining their underlying physical properties. The dust radiative transfer problem is solved self-consistently for a given set of physical inputs. Spherical geometry is chosen to minimize the run time, given the large number (~ millions) of models necessary. The model output is convolved with appropriate beams to produce simulated observations, which are then compared with observational data. A best fit is achieved using the Levenberg-Marquardt DNLS1 routine from the SLATEC library, to minimize the chi-squared deviation. The speed of the model allows a large number of initial starting conditions to be considered. While any number of parameters can be fitted, we concentrate on the dust density and grain property distribution. We apply the model to the well-studied source B335. While much of the envelope is well modelled by a power-law exponent ~1.5-1.9, we find potential evidence for a different inner structure for r < ~10arcsec, as well as an outer tenuous envelope for r > 120arcsec. We also find evidence of a variation in grain properties with radial position. The interior and exterior have larger concentrations of both thick ice mantles and bare grains. The properties in the interior would be consistent with a non-spherical structure seen by Harvey et al. (2003b) and Stutz et al. (2008), and the exterior would be consistent with incomplete refreezing of ice on to mantles after an evaporative event, such as a shock, in the last ~105 yr.

Doty, S. D.; Tidman, R.; Shirley, Y.; Jackson, A.

2010-08-01

132

Current Star Formation in the Perseus Molecular Cloud: Constraints from Unbiased Submillimeter and Mid-Infrared Surveys  

E-print Network

We present a census of the population of deeply embedded young stellar objects (YSOs) in the Perseus molecular cloud complex based on a combination of Spitzer Space Telescope mid-IR data from the c2d legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. The mid-IR sources detected at 24 micron and having [3.6]-[4.5] > 1 are located close to the center of the SCUBA cores, typically within 15" of their peaks. The narrowness of the spatial distribution of mid-IR sources around the peaks of the SCUBA cores suggests that no significant dispersal of the newly formed YSOs has occurred. This argues against the suggestion that motions of protostars regulate the time scales over which significant (Bondi-Hoyle) accretion can occur. The most deeply embedded YSOs are found in regions with high extinction, AV > 5, similar to the extinction threshold observed for the SCUBA cores. All the SCUBA cores with high concentrations have embedded YSOs, but not all cores with low concentrations are starless. An unbiased sample of 49 deeply embedded YSOs is constructed. Embedded YSOs are found in 40 of the 72 SCUBA cores with only three cores harboring multiple embedded YSOs within 15". The equal number of SCUBA cores with and without embedded YSOs suggests that the time scale for the evolution through the dense prestellar stages, where the cores are recognized in the submillimeter maps and have central densities of 5e4-1e5 cm^{-3}, is similar to the time scale for the embedded protostellar stages. The current star formation efficiency of cores is estimated to be approximately 10-15%. In contrast, the star formation efficiency averaged over the cloud life time and compared to the total cloud mass is only a few percent, reflecting also the efficiency in assembling cloud material into the dense cores forming stars.

Jes K. Jorgensen; Doug Johnstone; Helen Kirk; Philip C. Myers

2006-10-12

133

Unbiased Robust Template Estimation  

E-print Network

up the cortical sheet are for example manifested in aging, Alzheimer's disease, Huntington's disease of disease progression or onset; this is an active and important area of research. Longitudinal imaging-based biomarkers are thus of great potential utility in evaluating the efficiency of disease-modifying therapies

Reuter, Martin

134

Spectra From Space : Main Menu  

NSDL National Science Digital Library

On-line science lesson (grades 7 - 9) - students learn about satellite spectra research, electromagnetic spectrum, do hands-on activities. In this lesson students investigate satellite missions operating in four electromagnetic bands. Students learn about spectra and why satellites gather certain kinds of spectra from space by using the Internet and doing hands-on activities. From the University of California, Berkeley.

1997-01-01

135

Continuum Fitting HST QSO Spectra  

NASA Technical Reports Server (NTRS)

The Principal Component Analysis (PCA) method which we are using to fit and describe QSO spectra relies upon the fact that QSO continuum are generally very smooth and simple except for emission and absorption lines. To see this we need high signal-to-noise (S/N) spectra of QSOs at low redshift which have relatively few absorption lines in the Lyman-a forest. We need a large number of such spectra to use as the basis set for the PCA analysis which will find the set of principal component spectra which describe the QSO family as a whole. We have found that too few HST spectra have the required S/N and hence we need to supplement them with ground based spectra of QSOs at higher redshift. We have many such spectra and we have been working to make them suitable for this analysis. We have concentrated on this topic since 12/15/01.

Tytler, David; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

136

Cosmology from quasar spectra  

NASA Astrophysics Data System (ADS)

High resolution spectroscopy of high redshift quasar spectra enables us to investigate the properties of the intergalactic medium (IGM) and measure cosmological parameters from the Lya forest. Toward high precision cosmology, this dissertation presents the following four topics. (1) Principal Component Analysis (PCA) on quasar spectrum: We introduce the PCA to describe quasar emission lines and continua quantitatively, and we attempt to make a prediction of the continuum shape in the Lya forest using wavelengths redward of Lya emission. (2) Flux calibration of Keck HIRES data: On our way to achieve high accuracy measurement, it was necessary to develop new calibration schemes and explore the origin of systematic errors. My contribution includes the following and is discussed throughout the thesis: (i) the development of the flux calibration scheme, (ii) the discovery of three emission lines in the Lya forest, (iii) the establishment of high resolution standard star spectra, and (iv) the identification of ozone lines in the spectrum. (3) D/H measurement: We present precise measurements of the primordial deuterium to hydrogen ratio (D/ H) toward two quasars, HS0105+1619 and Q1243+3047, which constrains the baryon to photon ratio e = 5.9 +/- 0.5 x 10 -10 or the baryon density O b h 2 = 0.0214 +/- 0.0020 via the Big Bang Nucleosynthesis theory. (4) Studies of the Lya forest at z ~ 2: We also present the measurements of the total amount of neutral hydrogen absorption in the IGM. We compare our observed data with hydrodynamic simulations and find good agreement when we use the following cosmological parameters: H o = 71 kin s -1 Mpc -1 , O L = 0.73, O m = 0.27, O b = 0.044, the amplitude of the power spectrum s 8 = 0.9, and the photoinization rate G 912 = (1.44 +/- 0.11) x 10 -12 s -1 . We conclude that the measurements of the cosmological parameters from our primordial D/H measurements, recent WMAP satellite observation of the cosmic microwave background, and our the total amount of neutral hydrogen in the IGM at z ~ 2 are in a concordance with the LCDM model.

Suzuki, Nao

2005-11-01

137

THERMAL NEUTRON SPECTRA IN GRAPHITE  

Microsoft Academic Search

A pulsed, high-current, electron linear accelerator is used to excite ; thermal-neutron spectra in a graphite asemmbly. The steady-state energy spectra ; of neutrons are measured at several temperatures by pulsed-beam time-of-flight ; techniques. The measured spectra are compared with theoretical predictions which ; use free- and bound-carbon scattering kernels. The scattering kernel for carbon ; bound in graphite is

D. E. Parks; J. R. Beyster; N. F. Wikner

1962-01-01

138

Ion Signatures in Supernova Spectra  

E-print Network

A systematic survey of ions that could be responsible for features in the optical spectra of supernovae is carried out. Six different compositions that could be encountered in supernovae are considered. For each composition, the LTE optical depth of one of the strongest optical lines of each ion is plotted against temperature. For each ion that can realistically be considered as a candidate to produce identifiable features in supernova spectra, a sample synthetic spectrum is displayed. The optical depth plots and the synthetic spectra can provide guidance to studies of line identifications in the optical spectra of all types of supernovae during their photospheric phases.

K. Hatano; D. Branch; A. Fisher; J. Deaton; E. Baron

1998-09-18

139

Interpreting Chromosome Aberration Spectra  

NASA Technical Reports Server (NTRS)

Ionizing radiation can damage cells by breaking both strands of DNA in multiple locations, essentially cutting chromosomes into pieces. The cell has enzymatic mechanisms to repair such breaks; however, these mechanisms are imperfect and, in an exchange process, may produce a large-scale rearrangement of the genome, called a chromosome aberration. Chromosome aberrations are important in killing cells, during carcinogenesis, in characterizing repair/misrepair pathways, in retrospective radiation biodosimetry, and in a number of other ways. DNA staining techniques such as mFISH ( multicolor fluorescent in situ hybridization) provide a means for analyzing aberration spectra by examining observed final patterns. Unfortunately, an mFISH observed final pattern often does not uniquely determine the underlying exchange process. Further, resolution limitations in the painting protocol sometimes lead to apparently incomplete final patterns. We here describe an algorithm for systematically finding exchange processes consistent with any observed final pattern. This algorithm uses aberration multigraphs, a mathematical formalism that links the various aspects of aberration formation. By applying a measure to the space of consistent multigraphs, we will show how to generate model-specific distributions of aberration processes from mFISH experimental data. The approach is implemented by software freely available over the internet. As a sample application, we apply these algorithms to an aberration data set, obtaining a distribution of exchange cycle sizes, which serves to measure aberration complexity. Estimating complexity, in turn, helps indicate how damaging the aberrations are and may facilitate identification of radiation type in retrospective biodosimetry.

Levy, Dan; Reeder, Christopher; Loucas, Bradford; Hlatky, Lynn; Chen, Allen; Cornforth, Michael; Sachs, Rainer

2007-01-01

140

Projecting Spectra for Classroom Investigations.  

ERIC Educational Resources Information Center

Describes an inexpensive spectrum projector that makes high-dispersion, high-efficiency diffraction gratings using a holographic process. Discusses classroom applications such as transmission spectra, absorption spectra, reflection characteristics of materials, color mixing, florescence and phosphorescence, and break up spectral colors. (MDH)

Sadler, Philip

1991-01-01

141

Two components in meteor spectra  

Microsoft Academic Search

Through an analysis of fireball spectra it was found that meteor heads consist of two parts with quite different temperatures. The spectra of both parts can be fitted with a simple thermal equilibrium model. The temperature of the main spectrum is about 4000 K, and that of the second spectrum is about 10,000 K. There is little evidence for a

Jiri Borovicka

1994-01-01

142

SPECTROSCOPIC PROPERTIES OF STAR-FORMING HOST GALAXIES AND TYPE Ia SUPERNOVA HUBBLE RESIDUALS IN A NEARLY UNBIASED SAMPLE  

SciTech Connect

We examine the correlation between supernova (SN) host-galaxy properties and their residuals in the Hubble diagram. We use SNe discovered during the Sloan Digital Sky Survey-II Supernova Survey, and focus on objects at a redshift of z < 0.15, where the selection effects of the survey are known to yield a complete Type Ia supernova (SN Ia) sample. To minimize the bias in our analysis with respect to measured host-galaxy properties, spectra were obtained for nearly all hosts, spanning a range in magnitude of -23 < M{sub r} < -17. In contrast to previous works that use photometric estimates of host mass as a proxy for global metallicity, we analyze host-galaxy spectra to obtain gas-phase metallicities and star formation rates (SFRs) from host galaxies with active star formation. From a final sample of {approx}40 emission-line galaxies, we find that light-curve-corrected SNe Ia are {approx}0.1 mag brighter in high-metallicity hosts than in low-metallicity hosts. We also find a significant (>3{sigma}) correlation between the Hubble Residuals of SNe Ia and the specific SFR of the host galaxy. We comment on the importance of SN/host-galaxy correlations as a source of systematic bias in future deep SN surveys.

D'Andrea, Chris B.; Gupta, Ravi R.; Sako, Masao; Morris, Matt [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Nichol, Robert C.; Campbell, Heather; Lampeitl, Hubert [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Brown, Peter J.; Olmstead, Matthew D. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Frieman, Joshua A.; Kessler, Richard [Kavli Institute for Cosmological Physics, The University of Chicago, 5640 South Ellise Avenue, Chicago, IL 60637 (United States); Garnavich, Peter [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Jha, Saurabh W. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Marriner, John [Center for Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Smith, Mathew, E-mail: chris.dandrea@port.ac.uk [Astrophysics, Cosmology and Gravity Centre, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa)

2011-12-20

143

MODELING EXTRAGALACTIC FOREGROUNDS AND SECONDARIES FOR UNBIASED ESTIMATION OF COSMOLOGICAL PARAMETERS FROM PRIMARY COSMIC MICROWAVE BACKGROUND ANISOTROPY  

SciTech Connect

Using the latest physical modeling and constrained by the most recent data, we develop a phenomenological parameterized model of the contributions to intensity and polarization maps at millimeter wavelengths from external galaxies and Sunyaev-Zeldovich effects. We find such modeling to be necessary for estimation of cosmological parameters from Planck data. For example, ignoring the clustering of the infrared background would result in a bias in n{sub s} of 7{sigma} in the context of an eight-parameter cosmological model. We show that the simultaneous marginalization over a full foreground model can eliminate such biases, while increasing the statistical uncertainty in cosmological parameters by less than 20%. The small increases in uncertainty can be significantly reduced with the inclusion of higher-resolution ground-based data. The multi-frequency analysis we employ involves modeling 46 total power spectra and marginalization over 17 foreground parameters. We show that we can also reduce the data to a best estimate of the cosmic microwave background power spectra, with just two principal components (with constrained amplitudes) describing residual foreground contamination.

Millea, M.; Knox, L. [Department of Physics, University of California, Davis, CA 95616 (United States); Dore, O. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Dudley, J.; Holder, G. [Department of Physics, McGill University, Montreal, Quebec H3A 2T8 (Canada); Shaw, L. [Department of Physics, Yale University, New Haven, CT 06520-8120 (United States); Song, Y.-S. [Korea Institute for Advanced Study, Seoul 130-722 (Korea, Republic of); Zahn, O. [Berkeley Center for Cosmological Physics, Department of Physics, University of California, and Lawrence Berkeley National Labs, Berkeley, CA 94720 (United States)

2012-02-10

144

An unbiased method for the quantitation of disease phenotypes using a custom-built macro plugin for the program ImageJ.  

PubMed

Accurate evaluation of disease phenotypes is considered a key step to study plant-microbe interactions, as the rate of host colonization by the pathogenic microbe directly reflects whether the defense response of the plant is compromised. Although several techniques were developed to quantitate the amount of infection, only a few of them are inherently suitable for large disease screens. Here, I describe an unbiased method to quantitate disease phenotypes which manifest themselves by visible symptoms contrasting with the remaining unaffected parts of the host tissue. The method utilizes a macro plugin written for the image processing program "ImageJ" to calculate two values which determine the disease index for a specific treatment. In case the disease symptoms are not clear, a transgenic pathogenic fungus expressing the GUS gene is suitable for high-throughput disease screens, since staining for GUS activity facilitates an easy detection of the blue-stained pathogen. I illustrate the versatility of this method by analyzing a data set from a functional silencing screening experiment in resistant tomato that was inoculated with a GUS-expressing strain of the fungus Cladosporium fulvum. The method calculates a disease index for each silenced plant and thereby provides a basis for the unbiased identification of candidate host genes required for full resistance to this fungus. PMID:22183684

Abd-El-Haliem, Ahmed

2012-01-01

145

IntrAst2 (Petrovay) Spectra STELLAR SPECTRA  

E-print Network

. This is the spectrum (lat. spectrum = apparition -- cf. "ghost image") For an extended object these images overlap) Spectra Kirchhoff's laws of spectroscopy (1860): 1. The spectrum of a hot body (solid body or opaque

Petrovay, Kristóf

146

Absorption Spectra of Astaxanthin Aggregates  

E-print Network

Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption maximum of monomeric astaxanthin (470-495 nm depending on solvent) are caused by excitonic interaction between aggregated molecules. We applied molecular dynamics simulations to elucidate structure of astaxanthin dimer in water, and the resulting structure was used as a basis for calculations of absorption spectra. Absorption spectra of astaxanthin aggregates in hydrated dimethylsulfoxide were calculated using molecular exciton model with the resonance interaction energy between astaxanthin monomers constrained by semi-e...

Olsina, Jan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

2012-01-01

147

Skyshine spectra of gamma rays  

Microsoft Academic Search

A study of the spectra of gamma photons back-scattered in vertical direction by infinite air above ground (skyshine) is presented. The source for these measurements is a 650 Ci Cobalt-60 point-source and the skyshine spectra are reported for distances from 150 m to 325 m from the source, measured with a 5 cm NaI(T1) detector collimated with collimators of 12

J. Swarup

1980-01-01

148

Mutational spectra of human cancer  

Microsoft Academic Search

The purpose of this review is to summarize the evidence that can be used to reconstruct the etiology of human cancers from\\u000a mutations found in tumors. Mutational spectra of the tumor suppressor gene p53 (TP53) are tumor specific. In several cases, these mutational spectra can be linked to exogenous carcinogens, most notably for\\u000a sunlight-associated skin cancers, tobacco-associated lung cancers, and

Gerd P. Pfeifer; Ahmad Besaratinia

2009-01-01

149

Estimators of bottom reflectance spectra  

NASA Technical Reports Server (NTRS)

Estimators of in situ bottom spectral reflectance are calculated from multi-station optical field data gathered with standard instrumentation from different sites. These spectra are then compared to reflectance spectra measured in the laboratory of the bottom sediments collected in the field for the stations at these different sites. The relative fit of the estimated spectral curves to those measured in the laboratory was measured. The most accurate absolute estimation was provided by the single scattering irradiance model.

Estep, L.; Holloway, J.

1992-01-01

150

Unbiased screen for interactors of leucine-rich repeat kinase 2 supports a common pathway for sporadic and familial Parkinson disease.  

PubMed

Mutations in leucine-rich repeat kinase 2 (LRRK2) cause inherited Parkinson disease (PD), and common variants around LRRK2 are a risk factor for sporadic PD. Using protein-protein interaction arrays, we identified BCL2-associated athanogene 5, Rab7L1 (RAB7, member RAS oncogene family-like 1), and Cyclin-G-associated kinase as binding partners of LRRK2. The latter two genes are candidate genes for risk for sporadic PD identified by genome-wide association studies. These proteins form a complex that promotes clearance of Golgi-derived vesicles through the autophagy-lysosome system both in vitro and in vivo. We propose that three different genes for PD have a common biological function. More generally, data integration from multiple unbiased screens can provide insight into human disease mechanisms. PMID:24510904

Beilina, Alexandria; Rudenko, Iakov N; Kaganovich, Alice; Civiero, Laura; Chau, Hien; Kalia, Suneil K; Kalia, Lorraine V; Lobbestael, Evy; Chia, Ruth; Ndukwe, Kelechi; Ding, Jinhui; Nalls, Mike A; Olszewski, Maciej; Hauser, David N; Kumaran, Ravindran; Lozano, Andres M; Baekelandt, Veerle; Greene, Lois E; Taymans, Jean-Marc; Greggio, Elisa; Cookson, Mark R

2014-02-18

151

Mid-IR Properties of an Unbiased AGN Sample of the Local Universe. 1; Emission-Line Diagnostics  

NASA Technical Reports Server (NTRS)

\\Ve compare mid-IR emission-lines properties, from high-resolution Spitzer IRS spectra of a statistically-complete hard X-ray (14-195 keV) selected sample of nearby (z < 0.05) AGN detected by the Burst Alert Telescope (BAT) aboard Swift. The luminosity distribution for the mid-infrared emission-lines, [O IV] 25.89 microns, [Ne II] 12.81 microns, [Ne III] 15.56 microns and [Ne V] 14.32 microns, and hard X-ray continuum show no differences between Seyfert 1 and Seyfert 2 populations, although six newly discovered BAT AGNs are shown to be under-luminous in [O IV], most likely the result of dust extinction in the host galaxy. The overall tightness of the mid-infrared correlations and BAT luminosities suggests that the emission lines primarily arise in gas ionized by the AGN. We also compared the mid-IR emission-lines in the BAT AGNs with those from published studies of star-forming galaxies and LINERs. We found that the BAT AGN fall into a distinctive region when comparing the [Ne III]/[Ne II] and the [O IV]/[Ne III] quantities. From this we found that sources that have been previously classified in the mid-infrared/optical as AGN have smaller emission line ratios than those found for the BAT AGNs, suggesting that, in our X-ray selected sample, the AGN represents the main contribution to the observed line emission. Overall, we present a different set of emission line diagnostics to distinguish between AGN and star forming galaxies that can be used as a tool to find new AGN.

Weaver, K. A.; Melendez, M.; Muhotzky, R. F.; Kraemer, S.; Engle, K.; Malumuth. E.; Tueller, J.; Markwardt, C.; Berghea, C. T.; Dudik, R. P.; Winter, L. M.; Armus, L.

2010-01-01

152

Mid-IR Properties of an Unbiased AGN Sample of the Local Universe. I. Emission-Line Diagnostics  

NASA Astrophysics Data System (ADS)

We compare mid-IR emission-lines properties, from high-resolution Spitzer IRS spectra,of a statistically-complete hard X-ray (14-195 keV) selected sample of nearby (z < 0.05) AGN detected by the Burst Alert Telescope (BAT) aboard Swift. The luminosity distribution for the mid-infrared emission-lines, [O IV] 25.89 ?m, [Ne II] 12.81?m , [Ne III] 15.56 ?m and [Ne V] ?m, and hard X-ray show no differences between Seyfert 1 and Seyfert 2 populations, although six newly discovered BAT AGN are shown to be under-luminous in [O IV], most likely the result of dust extinction in the host galaxy. The correlations between all the mid-infrared emission lines and BAT luminosities are statistically significant. The mid-infrared emission line fluxes are highly correlated, with the worst correlations for [Ne V]-[Ne II] and [O IV]-[Ne II], as a result of enhanced [Ne II] in some sources due to nuclear stellar activity, however the tightness of these mid-infrared correlations suggests that the emission lines primarily arise in gas ionized by the AGN. We also compared the mid-IR emission-lines in the BAT AGNs with those from published studies of star-forming galaxies and LINERs. We found that [Ne III] an [O IV] lines do not unambiguously identify AGNs as stand-along diagnostics, however the BAT AGNs fall into a distinctive region when comparing the [Ne III]/[Ne II] and the [O IV]/[Ne III] quantities. While it is likely that detection of [Ne V] indicates the presence of an AGN, the [Ne V] line is weak compared to [O IV] and may not be detected in weak AGN. We suggest that a composite method using [Ne II], [Ne III], and [O IV] provides a more robust diagnostic.

Melendez, Marcio; Weaver, K.; Kraemer, S.; Mushotzky, R. F.; Tueller, J.; Markwardt, C. B.; Malumuth, E. M.; Engle, K.; Armus, L.; Berghea, C. T.; Dudik, R. P.; Winter, L. M.

2010-01-01

153

Myths and Truths Concerning Estimation of Power Spectra  

E-print Network

It is widely believed that maximum likelihood estimators must be used to provide optimal estimates of power spectra. Since such estimators require require of order N_d^3 operations they are computationally prohibitive for N_d greater than a few tens of thousands. Because of this, a large and inhomogeneous literature exists on approximate methods of power spectrum estimation. These range from manifestly sub-optimal, but computationally fast methods, to near optimal but computationally expensive methods. Furthermore, much of this literature concentrates on the power spectrum estimates rather than the equally important problem of deriving an accurate covariance matrix. In this paper, I consider the problem of estimating the power spectrum of cosmic microwave background (CMB) anisotropies from large data sets. Various analytic results on power spectrum estimators are derived, or collated from the literature, and tested against numerical simulations. An unbiased hybrid estimator is proposed that combines a maximum likelihood estimator at low multipoles and pseudo-C_\\ell estimates at high multipoles. The hybrid estimator is computationally fast, nearly optimal over the full range of multipoles, and returns an accurate and nearly diagonal covariance matrix for realistic experimental configurations (provided certain conditions on the noise properties of the experiment are satisfied). It is argued that, in practice, computationally expensive methods that approximate the N_d^3 maximum likelihood solution are unlikely to improve on the hybrid estimator, and may actually perform worse. The results presented here can be generalised to CMB polarization and to power spectrum estimation using other types of data, such as galaxy clustering and weak gravitational lensing.

G. Efstathiou

2003-07-30

154

QUALITATIVE INTERPRETATION OF GALAXY SPECTRA  

SciTech Connect

We describe a simple step-by-step guide to qualitative interpretation of galaxy spectra. Rather than an alternative to existing automated tools, it is put forward as an instrument for quick-look analysis and for gaining physical insight when interpreting the outputs provided by automated tools. Though the recipe is for general application, it was developed for understanding the nature of the Automatic Spectroscopic K-means-based (ASK) template spectra. They resulted from the classification of all the galaxy spectra in the Sloan Digital Sky Survey data release 7, thus being a comprehensive representation of the galaxy spectra in the local universe. Using the recipe, we give a description of the properties of the gas and the stars that characterize the ASK classes, from those corresponding to passively evolving galaxies, to H II galaxies undergoing a galaxy-wide starburst. The qualitative analysis is found to be in excellent agreement with quantitative analyses of the same spectra. We compare the mean ages of the stellar populations with those inferred using the code STARLIGHT. We also examine the estimated gas-phase metallicity with the metallicities obtained using electron-temperature-based methods. A number of byproducts follow from the analysis. There is a tight correlation between the age of the stellar population and the metallicity of the gas, which is stronger than the correlations between galaxy mass and stellar age, and galaxy mass and gas metallicity. The galaxy spectra are known to follow a one-dimensional sequence, and we identify the luminosity-weighted mean stellar age as the affine parameter that describes the sequence. All ASK classes happen to have a significant fraction of old stars, although spectrum-wise they are outshined by the youngest populations. Old stars are metal-rich or metal-poor depending on whether they reside in passive galaxies or in star-forming galaxies.

Sanchez Almeida, J.; Morales-Luis, A. B. [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); Terlevich, R.; Terlevich, E. [Instituto Nacional de Astrofisica, Optica y Electronica, Tonantzintla, Puebla (Mexico); Cid Fernandes, R., E-mail: jos@iac.es, E-mail: abml@iac.es, E-mail: rjt@ast.cam.ac.uk, E-mail: eterlevi@inaoep.mx, E-mail: cid@astro.ufsc.br [Departamento de Fisica-CFM, Universidade Federal de Santa Catarina, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil)

2012-09-10

155

AVIRIS spectra of California wetlands  

NASA Technical Reports Server (NTRS)

Spectral data gathered by the AVIRIS from wetlands in the Suisun Bay area of California on 13 October 1987 were analyzed. Spectra representing stands of numerous vegetation types (including Sesuvium verrucosum, Scirpus acutus and Scirpus californicus, Xanthium strumarium, Cynadon dactylon, and Distichlis spicata) and soil were isolated. Despite some defects in the data, it was possible to detect vegetation features such as differences in the location of the chlorophyll red absorption maximum. Also, differences in cover type spectra were evident in other spectral regions. It was not possible to determine if the observed features represent noise, variability in canopy architecture, or chemical constituents of leaves.

Gross, Michael F.; Ustin, Susan L.; Klemas, Vytautas

1988-01-01

156

Velocity determination from velocity spectra  

E-print Network

VELOCITY DETERMINATION FRON VELOCITY SPECTRA A Thesis by SUNG JIN YANG Submutted to the Graduate C:lleEe of Texas ASM University in partial fulfill sent of requirement for the degree of EASTER GF SCIENCE December 1973 Naj or Subject...: Ccophysics VELOCITY DETEPddINATION FROM VELOCITY SPECTRA A Thesis by SUNG JIN YANG Approved as to style and content by: ( Chai~ of C a0nitte ) (Read oi: Doper ent-IL irber) ( Meraber ) (i~ &r) Decen'bex' 1973 487460 ABSTRACT Velocity Determinati...

Yang, Sung Jin

2012-06-07

157

2014 SPECTRA (Speedy Consolidation and Transition) Program  

E-print Network

throughout their freshman year. Because the SPECTRA program is fast-paced, we require all SPECTRA students in the South. SPECTRA students enroll in classes, earn college credit, live in a residence hall on campus, residential hall living, and most costs associated with the SPECTRA program. In addition, participants

Kasman, Alex

158

Photoelectron Spectra of Halogenated Ethylenes  

Microsoft Academic Search

Photoelectron spectra of chloro-, fluoro- and chlorofluoroethylenes have been measured. Ionization potentials in the range 6 to 21 eV have been determined, and vibrational structure associated with many of the electronic transitions has been interpreted in terms of vibrations of the ion and correlated with those of the parent molecule. The various ionization potentials have been associated with specific orbitals

R. F. Lake; Harold Thompson

1970-01-01

159

Chlorophyll Spectra and Molecular Structure  

Microsoft Academic Search

DURING experiments on pigment orientation in chloroplasts and grana, it was necessary to determine the directions in which linearly polarized light is preferably absorbed in a pigment molecule. This preference corresponds to the directions of maximum transition probability of the electronic transitions which give rise to the different absorption bands in the spectra. By studying dichroism and polarization of fluorescence

J. C. Goedheer

1955-01-01

160

Inference of site frequency spectra from high-throughput sequence data: quantification of selection on nonsynonymous and synonymous sites in humans.  

PubMed

Sequencing errors and random sampling of nucleotide types among sequencing reads at heterozygous sites present challenges for accurate, unbiased inference of single-nucleotide polymorphism genotypes from high-throughput sequence data. Here, we develop a maximum-likelihood approach to estimate the frequency distribution of the number of alleles in a sample of individuals (the site frequency spectrum), using high-throughput sequence data. Our method assumes binomial sampling of nucleotide types in heterozygotes and random sequencing error. By simulations, we show that close to unbiased estimates of the site frequency spectrum can be obtained if the error rate per base read does not exceed the population nucleotide diversity. We also show that these estimates are reasonably robust if errors are nonrandom. We then apply the method to infer site frequency spectra for zerofold degenerate, fourfold degenerate, and intronic sites of protein-coding genes using the low coverage human sequence data produced by the 1000 Genomes Project phase-one pilot. By fitting a model to the inferred site frequency spectra that estimates parameters of the distribution of fitness effects of new mutations, we find evidence for significant natural selection operating on fourfold sites. We also find that a model with variable effects of mutations at synonymous sites fits the data significantly better than a model with equal mutational effects. Under the variable effects model, we infer that 11% of synonymous mutations are subject to strong purifying selection. PMID:21596896

Keightley, Peter D; Halligan, Daniel L

2011-08-01

161

Source spectra of seismic hum  

NASA Astrophysics Data System (ADS)

The observation of seismic hum from 2 to 20 mHz, also known as Earth's background free oscillations, has been established. Recent observations by broad-band seismometers show simultaneous excitation of Love waves (fundamental toroidal modes) and Rayleigh waves (fundamental spheroidal modes). The excitation amplitudes above 10 mHz can be explained by random shear traction sources on Earth's surface. With estimated source distributions, the most likely excitation mechanism is a linear coupling between ocean infragravity waves and seismic surface waves through seafloor topography. Observed Love and Rayleigh wave amplitudes below 5 mHz suggest that surface pressure sources could also contribute to their excitations, although the amplitudes have large uncertainties due to the high noise levels of the horizontal components. To quantify the observation, we develop a new method for estimation of the source spectra of random tractions on Earth's surface by modelling cross-spectra between pairs of stations. The method is to calculate synthetic cross-spectra for spatially isotropic and homogeneous excitations by random shear traction and pressure sources, and invert them with the observed cross-spectra to obtain the source spectra. We applied this method to the IRIS, ORFEUS, and F-net records from 618 stations with three components of broad-band seismometers for 2004-2011. The results show the dominance of shear traction above 5 mHz, which is consistent with past studies. Below 5 mHz, however, the spectral amplitudes of the pressure sources are comparable to those of shear traction. Observed acoustic resonance between the atmosphere and the solid Earth at 3.7 and 4.4 mHz suggests that atmospheric disturbances are responsible for the surface pressure sources, although non-linear ocean wave processes are also candidates for the pressure sources. Excitation mechanisms of seismic hum should be considered as a superposition of the processes of the solid Earth, atmosphere and ocean as a coupled system.

Nishida, Kiwamu

2014-10-01

162

An unbiased evaluation of CK2 inhibitors by chemoproteomics: characterization of inhibitor effects on CK2 and identification of novel inhibitor targets.  

PubMed

Recently protein kinases have emerged as some of the most promising drug targets; and therefore, pharmaceutical strategies have been developed to inhibit kinases in the treatment of a variety of diseases. CK2 is a serine/threonine-protein kinase that has been implicated in a number of cellular processes, including maintenance of cell viability, protection of cells from apoptosis, and tumorigenesis. Elevated CK2 activity has been established in a number of cancers where it was shown to promote tumorigenesis via the regulation of the activity of various oncogenes and tumor suppressor proteins. Consequently the development of CK2 inhibitors has been ongoing in preclinical studies, resulting in the generation of a number of CK2-directed compounds. In the present study, an unbiased evaluation of CK2 inhibitors 4,5,6,7-tetrabromo-1H-benzotriazole (TBB), 4,5,6,7-tetrabromo-1H-benzimidazole (TBBz), and 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT) was carried out to elucidate the mechanism of action as well as inhibitor specificity of these compounds. Utilizing a chemoproteomics approach in conjunction with inhibitor-resistant mutant studies, CK2alpha and CK2alpha' were identified as bona fide targets of TBB, TBBz, and DMAT in cells. However, inhibitor-specific cellular effects were observed indicating that the structurally related compounds had unique biological properties, suggesting differences in inhibitor specificity. Rescue experiments utilizing inhibitor-resistant CK2 mutants were unable to rescue the apoptosis associated with TBBz and DMAT treatment, suggesting the inhibitors had off-target effects. Exploitation of an unbiased chemoproteomics approach revealed a number of putative off-target inhibitor interactions, including the discovery of a novel TBBz and DMAT (but not TBB) target, the detoxification enzyme quinone reductase 2 (QR2). The results described in the present study provide insight into the molecular mechanism of action of the inhibitors as well as drug specificity that will assist in the development of more specific next generation CK2 inhibitors. PMID:18258654

Duncan, James S; Gyenis, Laszlo; Lenehan, John; Bretner, Maria; Graves, Lee M; Haystead, Timothy A; Litchfield, David W

2008-06-01

163

Hierarchical analysis of molecular spectra  

SciTech Connect

A novel representation of molecular spectra in terms of hierarchical trees has proven to be an important aid for the study of many significant problems in gas-phase chemical dynamics. Trees are generated from molecular spectra by monitoring the changes that occur in a spectrum as resolution is changed in a continuous manner. A tree defines a genealogy among all lines of a spectrum. This allows for a detailed understanding of the assignment of features of a spectrum that may be difficult to obtain any other way as well as an understanding of intramolecular energy transfer time scales, mechanisms, and pathways. The methodology has been applied to several problems: transition state spectroscopy, intramolecular energy transfer in highly excited molecules, high-resolution overtone spectroscopy, and the nature of the classical-quantum correspondence when there is classical chaos (``quantum chaos``).

Davis, M.J.

1996-03-01

164

Multiresolution of quasicrystal diffraction spectra.  

PubMed

A method for analyzing and classifying two-dimensional pure point diffraction spectra (i.e. a set of Bragg peaks) of certain self-similar structures with scaling factor beta > 1, such as quasicrystals, is presented. The two-dimensional pure point diffraction spectrum Pi is viewed as a point set in the complex plane in which each point is assigned a positive number, its Bragg intensity. Then, by using a nested sequence of self-similar subsets called beta-lattices, we implement a multiresolution analysis of the spectrum Pi. This analysis yields a partition of Pi simultaneously in geometry, in scale and in intensity (the 'fingerprint' of the spectrum, not of the diffracting structure itself). The method is tested through numerical explorations of pure point diffraction spectra of various mathematical structures and also with the diffraction pattern of a realistic model of a quasicrystal. PMID:19844031

Elkharrat, Avi; Gazeau, Jean Pierre; Dénoyer, Françoise

2009-11-01

165

Eigenvectors of optimal color spectra.  

PubMed

Principal component analysis (PCA) and weighted PCA were applied to spectra of optimal colors belonging to the outer surface of the object-color solid or to so-called MacAdam limits. The correlation matrix formed from this data is a circulant matrix whose biggest eigenvalue is simple and the corresponding eigenvector is constant. All other eigenvalues are double, and the eigenvectors can be expressed with trigonometric functions. Found trigonometric functions can be used as a general basis to reconstruct all possible smooth reflectance spectra. When the spectral data are weighted with an appropriate weight function, the essential part of the color information is compressed to the first three components and the shapes of the first three eigenvectors correspond to one achromatic response function and to two chromatic response functions, the latter corresponding approximately to Munsell opponent-hue directions 9YR-9B and 2BG-2R. PMID:24323262

Flinkman, Mika; Laamanen, Hannu; Tuomela, Jukka; Vahimaa, Pasi; Hauta-Kasari, Markku

2013-09-01

166

Moments of ambient Doppler spectra  

SciTech Connect

The author studied the first four moments (center of mass, standard deviation, skew, and kurtosis) of the Doppler spectra in ambient regions of LLNL-Hughes real aperture radar data collected during WCSEX91--92. The goal was to correlate trends in the moments with wind velocity and direction. Although the center of mass appears to increase when the wind is blowing into the radar antenna, no other conclusions have been drawn from the higher order moments.

Lehman, S.K.

1993-03-23

167

Pebbles and PebbleJuggler: software for accurate, unbiased, and fast measurement and analysis of nanoparticle morphology from transmission electron microscopy (TEM) micrographs.  

PubMed

Pebbles is a user-friendly software program which implements an accurate, unbiased, and fast method to measure the morphology of a population of nanoparticles (NPs) from TEM micrographs. The morphological parameters of the projected NP shape are obtained by fitting intensity models to the TEM micrograph. Pebbles can be used either in automatic mode, where both fitting and validation are reliably carried out with minimal human intervention, and in manual mode, where the user has full control on the fitting and validation steps. Accuracy in diameter measurement has been shown to be ?1%. When operated in automatic mode, Pebbles can be very fast. The effective speed of 1 NP s?¹ has been achieved in favorable cases (packed monolayer of NPs). Since Pebbles is based on a local modeling procedure, it successfully treats cases such as low contrast NPs, NPs with significant diffraction scattering, and inhomogeneous background which often make conventional thresholding procedures fail. Pebbles is accompanied by PebbleJuggler, a software program for the statistical analysis of the sets of best-fit NP models created by Pebbles. Effort has been devoted to make Pebbles and PebbleJuggler the most user-friendly and the least user-tedious we could. Pebbles and PebbleJuggler are available at http://pebbles.istm.cnr.it. PMID:22814937

Mondini, S; Ferretti, A M; Puglisi, A; Ponti, A

2012-09-01

168

Unbiased mm-wave Line Surveys of TW Hya and V4046 Sgr: The Enhanced C2H and CN Abundances of Evolved Protoplanetary Disks  

E-print Network

We have conducted the first comprehensive mm-wave molecular emission line surveys of the evolved circumstellar disks orbiting the nearby T Tauri stars TW Hya and V4046 Sgr AB. Both disks are known to retain significant residual gaseous components, despite the advanced ages of their host stars. Our unbiased broad-band radio spectral surveys of the TW Hya and V4046 Sgr disks were performed with the Atacama Pathfinder Experiment (APEX) 12 meter telescope and are intended to yield a complete census of bright molecular emission lines in the range 275-357 GHz (1.1-0.85 mm). We find that lines of 12CO, 13CO, HCN, CN, and C2H, all of which lie in the higher-frequency range, constitute the strongest molecular emission from both disks in the spectral region surveyed. The molecule C2H is detected here for the first time in both disks, as is CS in the TW Hya disk. The survey results also include the first measurements of the full suite of hyperfine transitions of CN N=3-2 and C2H N=4-3 in both disks. Modeling of these CN...

Kastner, Joel H; Rodriguez, David R; Punzi, Kristina; Forveille, Thierry

2014-01-01

169

Current Star Formation in the Ophiuchus and Perseus Molecular Clouds: Constraints and Comparisons from Unbiased Submillimeter and Mid-Infrared Surveys. II  

E-print Network

We present a census of the population of deeply embedded young stellar objects (YSOs) in the Ophiuchus molecular cloud complex based on a combination of Spitzer Space Telescope mid-infrared data from the "Cores to Disks" (c2d) legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. We have applied a method developed for identifying embedded protostars in Perseus to these datasets and in this way construct a relatively unbiased sample of 27 candidate embedded protostars with envelopes more massive than our sensitivity limit (about 0.1 M_sun). Embedded YSOs are found in 35% of the SCUBA cores - less than in Perseus (58%). On the other hand the mid-infrared sources in Ophiuchus have less red mid-infrared colors, possibly indicating that they are less embedded. We apply a nearest neighbor surface density algorithm to define the substructure in each of the clouds and calculate characteristic numbers for each subregion - including masses, star formation efficiencies, fraction of embedded sources etc. Generally the main clusters in Ophiuchus and Perseus (L1688, NGC1333 and IC348) are found to have higher star formation efficiencies than small groups such as B1, L1455 and L1448, which on the other hand are completely dominated by deeply embedded protostars. We discuss possible explanations for the differences between the regions in Perseus and Ophiuchus, such as different evolutionary timescales for the YSOs or differences, e.g., in the accretion in the two clouds.

Jes Jorgensen; Doug Johnstone; Helen Kirk; Philip Myers; Lori Allen; Yancy Shirley

2008-05-06

170

Infrared Spectra of Polycyclic Aromatic Hydrocarbons (PAHs)  

NASA Technical Reports Server (NTRS)

We have computed the synthetic infrared spectra of some polycyclic aromatic hydrocarbons containing up to 54 carbon atoms. The species studied include ovalene, circumcoronene, dicoronylene, and hexabenzocoronene. We report spectra for anions, neutrals, cations, and multiply charged cations.

Bauschlicher, Charles W., Jr.; Bakes, E. L. O.

2000-01-01

171

Action spectra for photosynthetic inhibition  

NASA Technical Reports Server (NTRS)

The ultraviolet action spectrum for photosynthesis inhibition was determined to fall between that of the general DNA action spectrum and the generalized plant action spectrum. The characteristics of this action spectrum suggest that a combination of pronounced increase in effectiveness with decreasing wavelength, substantial specificity for the UV-B waveband, and very diminished response in the UV-A waveband result in large radiation amplification factors when the action spectra are used as weighting functions. Attempted determination of dose/response relationships for leaf disc inhibition provided inconclusive data from which to deconvolute an action spectrum.

Caldwell, M. M.; Flint, S.; Camp, L. B.

1981-01-01

172

Turbulent Spectra of Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

We have used a newly developed automated detection algorithm for recognition of interplanetary (IP) shocks which is planned to be implemented on board the future Solar Orbiter mission. We have identified more than 800 IP shocks in the Wind measurements during a prolonged time interval (1995 - 2013) with this algorithm. In order to investigate the magnetic ?eld ?uctuations in the IP medium we use the Morlet wavelet transform. The fluxgate magnetometer on-board Wind with a sampling frequency of 10 Hz allows us to analyze both inertial ranges and kinetic scales. We have statistically compared turbulent spectra in upstream and downstream of IP shocks.

Kruparova, Oksana; Krupar, Vratislav; Nemecek, Zdenek; Safrankova, Jana

173

Identified hadron spectra from PHOBOS  

NASA Astrophysics Data System (ADS)

Transverse momentum spectra of pions, kaons and protons, as well as antiparticle to particle ratios near mid-rapidity from d+Au collisions at \\sqrt{s_{{\\rm NN}}} = 200\\,{\\rm GeV} have been measured by the PHOBOS experiment at RHIC. The transverse momentum range of particle identification was extended to beyond 3 GeV/c using the TOF detector and a new trigger system. The pseudorapidity dependence of the nuclear modification factor for charged hadrons in d+Au collisions is presented.

Veres, Gábor I.; PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Becker, B.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Harrington, A. S.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Lee, J. W.; Lin, W. T.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Roland, C.; Roland, G.; Sagerer, J.; Sarin, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wyslouch, B.; Zhang, J.

2004-08-01

174

IUE-newsips spectra of sigma Geminorum  

Microsoft Academic Search

The IUE spectra of sigma Gem have been taken from the NASA IUE archive using IDL (Interactive Data Language). The spectra have been observed in 1979-1986 period. All the spectra analysed in the present study have NEWSIPS reductions and consist of 25 LWP, 8 LWR and 5 SWP images in high resolution, and 2 LWP and 14 SWP images in

F. Ekmekçi; O. Karakus

2002-01-01

175

Mass Spectra Alignments and their Significance  

E-print Network

Mass Spectra Alignments and their Significance Sebastian B¨ocker1, Hans-Michael Kaltenbach2 1 Research, Universit¨at Bielefeld B¨ocker, Kaltenbach Mass Spectra Alignments CPM 2005 #12;Overview Mass¨ocker, Kaltenbach Mass Spectra Alignments CPM 2005 #12;Overview Mass Spectrometry in Proteomics Protein

Lonardi, Stefano

176

Synthetic spectra of CP stars compared with UVES spectra  

NASA Astrophysics Data System (ADS)

Results from spectral analyses of some HgMn stars observed with UVES at high resolution and high S/N are available on-line in the form of plots showing superimposed observed and LTE-computed spectra. The material is available on line at http://wwwuser.oat.ts.astro.it/castelli/stars.html. The ranges studied are divided into 6Å wide intervals. The plots have identifications, excitation potential of the lower level, and predicted line intensities written above the lines. Complete analyses covering the 3050 - 9500Å region have been performed for two stars, HD175640 and HR6000. The on-line plots show the quality of the agreement between observations and computations and can be used as a template for other stars of the same spectral type. For instance, HD175640 and HR6000 are excellent examples of a very overabundant Mn ([+2.4]) star and of a very overabundant Fe ([+0.7]) star, respectively.

Castelli, F.; Hubrig, S.

2008-04-01

177

Molecular Interactions between the Specialist Herbivore Manduca sexta (Lepidoptera, Sphigidae) and Its Natural Host Nicotiana attenuata. VIII. An Unbiased GCxGC-ToFMS Analysis of the Plant's Elicited Volatile Emissions  

Microsoft Academic Search

Treating wounds in Nicotiana attenuata leaves with Manduca sexta oral secretions (W1OS) mimics most changes elicited by M. sexta herbivory, but an unbiased analysis of the effect of the different OS constituents on volatile emissions is lacking. We used two-dimensional gas chromatography\\/time-of-flight (GCxGC-ToF) mass spectrometry combined with multivariate statistics to parse volatiles into regulatory patterns. Volatiles released by wounding alone

Emmanuel Gaquerel; Alexander Weinhold; Ian T. Baldwin

2009-01-01

178

Pebbles and PebbleJuggler: software for accurate, unbiased, and fast measurement and analysis of nanoparticle morphology from transmission electron microscopy (TEM) micrographs  

NASA Astrophysics Data System (ADS)

Pebbles is a user-friendly software program which implements an accurate, unbiased, and fast method to measure the morphology of a population of nanoparticles (NPs) from TEM micrographs. The morphological parameters of the projected NP shape are obtained by fitting intensity models to the TEM micrograph. Pebbles can be used either in automatic mode, where both fitting and validation are reliably carried out with minimal human intervention, and in manual mode, where the user has full control on the fitting and validation steps. Accuracy in diameter measurement has been shown to be <~1%. When operated in automatic mode, Pebbles can be very fast. The effective speed of 1 NP s-1 has been achieved in favorable cases (packed monolayer of NPs). Since Pebbles is based on a local modeling procedure, it successfully treats cases such as low contrast NPs, NPs with significant diffraction scattering, and inhomogeneous background which often make conventional thresholding procedures fail. Pebbles is accompanied by PebbleJuggler, a software program for the statistical analysis of the sets of best-fit NP models created by Pebbles. Effort has been devoted to make Pebbles and PebbleJuggler the most user-friendly and the least user-tedious we could. Pebbles and PebbleJuggler are available at http://pebbles.istm.cnr.it.Pebbles is a user-friendly software program which implements an accurate, unbiased, and fast method to measure the morphology of a population of nanoparticles (NPs) from TEM micrographs. The morphological parameters of the projected NP shape are obtained by fitting intensity models to the TEM micrograph. Pebbles can be used either in automatic mode, where both fitting and validation are reliably carried out with minimal human intervention, and in manual mode, where the user has full control on the fitting and validation steps. Accuracy in diameter measurement has been shown to be <~1%. When operated in automatic mode, Pebbles can be very fast. The effective speed of 1 NP s-1 has been achieved in favorable cases (packed monolayer of NPs). Since Pebbles is based on a local modeling procedure, it successfully treats cases such as low contrast NPs, NPs with significant diffraction scattering, and inhomogeneous background which often make conventional thresholding procedures fail. Pebbles is accompanied by PebbleJuggler, a software program for the statistical analysis of the sets of best-fit NP models created by Pebbles. Effort has been devoted to make Pebbles and PebbleJuggler the most user-friendly and the least user-tedious we could. Pebbles and PebbleJuggler are available at http://pebbles.istm.cnr.it. Electronic supplementary information (ESI) available: Supplementary material (probability of diffraction scattering from crystalline NPs; figures related to the accuracy testing of the intensity models; results of fitting supported NPs and inhomogeneous NPs; figure showing the results of fitting TEM micrographs in automatic mode with Sguess/Dguess = 0.75; dependence of the fitting procedure throughput and completeness on the spacing Sguess of the guess center grid). See DOI: 10.1039/c2nr31276j

Mondini, S.; Ferretti, A. M.; Puglisi, A.; Ponti, A.

2012-08-01

179

Optical spectra and covalent chemistry of fulleropyrrolidines  

Microsoft Academic Search

Low-temperature vibronic spectra of two fulleropyrrolidines (1-methyl-3,4-FP and 1-methyl-2(4-pyridine)-3,4-FP) embedded in crystalline toluene matrix have been studied. Two-component composition of the spectra has been established and charge-transfer-excitation origin of the structureless component has been suggested. Fine-structured Shpol'skii spectra were observed for 1-methyl-3,4-FP, which made possible to perform the vibrational analysis of its vibronic spectra. General similarities of the absorption spectra

B. S. Razbirin; A. N. Starukhin; D. K. Nelson; E. F. Sheka; Me Prato

2007-01-01

180

An unbiased resource of novel SNP markers provides a new chronology for the human Y chromosome and reveals a deep phylogenetic structure in Africa.  

PubMed

Sequence diversity and the ages of the deepest nodes of the MSY phylogeny remain largely unexplored due to the severely biased collection of SNPs available for study. We characterized 68 worldwide Y chromosomes by high-coverage next-generation sequencing, including 18 deep-rooting ones, and identified 2386 SNPs, 80% of which were novel. Many aspects of this pool of variants resembled the pattern observed among genome-wide de novo events, suggesting that in the MSY, a large proportion of newly arisen alleles has survived in the phylogeny. Some degree of purifying selection emerged in the form of an excess of private missense variants. Our tree recapitulated the previously known topology, but the relative lengths of major branches were drastically modified and the associated node ages were remarkably older. We found significantly different branch lengths when comparing the rare deep-rooted A1b African lineage with the rest of the tree. Our dating results and phylogeography led to the following main conclusions: (1) Patrilineal lineages with ages approaching those of early AMH fossils survive today only in central-western Africa; (2) only a few evolutionarily successful MSY lineages survived between 160 and 115 kya; and (3) an early exit out of Africa (before 70 kya), which fits recent western Asian archaeological evidence, should be considered. Our experimental design produced an unbiased resource of new MSY markers informative for the initial formation of the anatomically modern human gene pool, i.e., a period of our evolution that had been previously considered to be poorly accessible with paternally inherited markers. PMID:24395829

Scozzari, Rosaria; Massaia, Andrea; Trombetta, Beniamino; Bellusci, Giovanna; Myres, Natalie M; Novelletto, Andrea; Cruciani, Fulvio

2014-03-01

181

Unbiased Mutagenesis of MHV68 LANA Reveals a DNA-Binding Domain Required for LANA Function In Vitro and In Vivo  

PubMed Central

The Latency-Associated Nuclear Antigen (LANA), encoded by ORF73, is a conserved gene among the ?2-herpesviruses (rhadinoviruses). The Kaposi's Sarcoma-Associated Herpesvirus (KSHV) LANA is consistently expressed in KSHV-associated malignancies. In the case of the rodent ?2-herpesvirus, murine gammaherpesvirus 68 (MHV68), the LANA homolog (mLANA) is required for efficient virus replication, reactivation from latency and immortalization of murine fetal liver-derived B cells. To gain insights into mLANA function(s), knowing that KSHV LANA binds DNA and can modulate transcription of a variety of promoters, we sought out and identified a mLANA-responsive promoter which maps to the terminal repeat (TR) of MHV68. Notably, mLANA strongly repressed activity from this promoter. We extended these analyses to demonstrate direct, sequence-specific binding of recombinant mLANA to TR DNA by DNase I footprinting. To assess whether the DNA-binding and/or transcription modulating function is important in the known mLANA phenotypes, we generated an unbiased library of mLANA point mutants using error-prone PCR, and screened a large panel of mutants for repression of the mLANA-responsive promoter to identify loss of function mutants. Notably, among the mutant mLANA proteins recovered, many of the mutations are in a predicted EBNA-1-like DNA-binding domain. Consistent with this prediction, those tested displayed loss of DNA binding activity. We engineered six of these mLANA mutants into the MHV68 genome and tested the resulting mutant viruses for: (i) replication fitness; (ii) efficiency of latency establishment; and (iii) reactivation from latency. Interestingly, each of these mLANA-mutant viruses exhibited phenotypes similar to the mLANA-null mutant virus, indicating that DNA-binding is critical for mLANA function. PMID:22969427

Paden, Clinton R.; Forrest, J. Craig; Tibbetts, Scott A.; Speck, Samuel H.

2012-01-01

182

Higher-Order Septin Assembly Is Driven by GTP-Promoted Conformational Changes: Evidence From Unbiased Mutational Analysis in Saccharomyces cerevisiae  

PubMed Central

Septin proteins bind GTP and heterooligomerize into filaments with conserved functions across a wide range of eukaryotes. Most septins hydrolyze GTP, altering the oligomerization interfaces; yet mutations designed to abolish nucleotide binding or hydrolysis by yeast septins perturb function only at high temperatures. Here, we apply an unbiased mutational approach to this problem. Mutations causing defects at high temperature mapped exclusively to the oligomerization interface encompassing the GTP-binding pocket, or to the pocket itself. Strikingly, cold-sensitive defects arise when certain of these same mutations are coexpressed with a wild-type allele, suggestive of a novel mode of dominance involving incompatibility between mutant and wild-type molecules at the septin–septin interfaces that mediate filament polymerization. A different cold-sensitive mutant harbors a substitution in an unstudied but highly conserved region of the septin Cdc12. A homologous domain in the small GTPase Ran allosterically regulates GTP-binding domain conformations, pointing to a possible new functional domain in some septins. Finally, we identify a mutation in septin Cdc3 that restores the high-temperature assembly competence of a mutant allele of septin Cdc10, likely by adopting a conformation more compatible with nucleotide-free Cdc10. Taken together, our findings demonstrate that GTP binding and hydrolysis promote, but are not required for, one-time events—presumably oligomerization-associated conformational changes—during assembly of the building blocks of septin filaments. Restrictive temperatures impose conformational constraints on mutant septin proteins, preventing new assembly and in certain cases destabilizing existing assemblies. These insights from yeast relate directly to disease-causing mutations in human septins. PMID:24398420

Weems, Andrew D.; Johnson, Courtney R.; Argueso, Juan Lucas; McMurray, Michael A.

2014-01-01

183

The Optically Unbiased GRB Host (TOUGH) Survey. V. VLT/X-shooter Emission-line Redshifts for Swift GRBs at z ~ 2  

NASA Astrophysics Data System (ADS)

We present simultaneous optical and near-infrared (NIR) spectroscopy of 19 Swift ?-ray burst (GRB) host galaxies observed with the VLT/X-shooter with the aim of measuring their redshifts. Galaxies were selected from The Optically Unbiased GRB Host (TOUGH) survey (15 of the 19 galaxies) or because they hosted GRBs without a bright optical afterglow. Here we provide emission-line redshifts for 13 of the observed galaxies with brightnesses between F606W > 27 mag and R = 22.9 mag (median \\tilde{R}=24.6\\,{mag}). The median redshift is \\tilde{z}=2.1 for all hosts and \\tilde{z}=2.3 for the TOUGH hosts. Our new data significantly improve the redshift completeness of the TOUGH survey, which now stands at 77% (53 out of 69 GRBs). They furthermore provide accurate redshifts for nine prototype dark GRBs (e.g., GRB 071021 at z = 2.452 and GRB 080207 at z = 2.086), which are exemplary of GRBs where redshifts are challenging to obtain via afterglow spectroscopy. This establishes X-shooter spectroscopy as an efficient tool for redshift determination of faint, star-forming, high-redshift galaxies such as GRB hosts. It is hence a further step toward removing the bias in GRB samples that is caused by optically dark events, and provides the basis for a better understanding of the conditions in which GRBs form. The distribution of column densities as measured from X-ray data (N H, X), for example, is closely related to the darkness of the afterglow and skewed toward low N H, X values in samples that are dominated by bursts with bright optical afterglows. Based on observations collected at the European Southern Observatory, Paranal, Chile, Program IDs: 177.A-0591, 080.A-0825, 084.A-0303, 086.B-0954, 087.B-0737, and 088.A-0644.

Krühler, Thomas; Malesani, Daniele; Milvang-Jensen, Bo; Fynbo, Johan P. U.; Hjorth, Jens; Jakobsson, Páll; Levan, Andrew J.; Sparre, Martin; Tanvir, Nial R.; Watson, Darach J.

2012-10-01

184

INVESTIGATION Coupling Unbiased Mutagenesis to  

E-print Network

microtubule attachments made by the Ndc80 complex. Finally, we defined a C-terminal segment of Ndc80 required and severe chromosome segregation defects (reviewed in Kline-Smith et al. 2005). Mirroring kinetochore

Dunham, Maitreya

185

Pressure spectra and cross spectra at an area contraction in a ducted combustion system  

NASA Technical Reports Server (NTRS)

Pressure spectra and cross-spectra at an area contraction in a liquid fuel, ducted, combustion noise test facility are analyzed. Measurements made over a range of air and fuel flows are discussed. Measured spectra are compared with spectra calculated using a simple analytical model.

Miles, J. H.; Raftopoulos, D. D.

1980-01-01

186

Brane Constructions and BPS Spectra  

NASA Astrophysics Data System (ADS)

The object of this work is to exploit various constructions of string theory and M-theory to yield new insights into supersymmetric theories in both four and three dimensions. In 4d, we extend work on Seiberg-Witten theory to study and compute BPS spectra of the class of complete N = 2 theories. The approach we take is based on the program of geometric engineering, in which 4d theories are constructed from compactifications of type IIB strings on Calabi-Yau manifolds. In this setup, the natural candidates for BPS states are D3 branes wrapped on supersymmetric 3-cycles in the Calabi-Yau. Our study makes use of the mathematical structure of quivers, whose representation theory encodes the notion of stability of BPS particles. Except for 11 exceptional cases, all complete theories can be constructed by wrapping stacks of two M5 branes on Riemann surfaces. By exploring the connection between quivers and M5 brane theories, we develop a powerful algorithm for computing BPS spectra, and give an in-depth study of its applications. In particular, we compute BPS spectra for all asymptotically free complete theories, as well as an infinite set of conformal SU(2)k theories with certain matter content. From here, we go on to apply the insight gained from our 4d study to 3d gauge theories. We consider the analog of the M5 brane construction in the case of 3d N = 2 theories: pairs of M5 branes wrapped on a 3-manifold. Using the ansantz of R-flow, we study 3-manifolds consisting of Riemann surfaces fibered over R. When the construction is non-singular, the resulting IR physics is described by a free abelian Chern-Simons theory. The mathematical data of a tangle captures the data of the gauge theory, and the Reidemeister equivalances on tangles correspond to dualities of physical descriptions. To obtain interacting matter, we allow singularities in the construction. By extending the tangle description to these singular cases, we find a set of generalized Reidemeister moves that capture non-trivial mirror symmetries of 3d gauge theories. These results give a geometric origin to these well-known 3d dualities.

Rastogi, Ashwin

187

Vibrational Spectra of Chlorinated Poly  

NASA Astrophysics Data System (ADS)

In order to refine the force field for secondary chlorides which is applicable to chlorinated poly (vinyl chloride), CPVC, 2,3,4-trichloro-pentanes and 2,2,3-trichloro -butane were synthesized. To avoid trouble upon separation of a meso and racemic isomer mixture of 2,3,4-trichloro -pentanes, we used a new method to obtain each isomer exclusively. Each isomer was identified by NMR. However, to confirm the identification, one of the tosylates, which is a precursor to be converted to the meso form, was structurally determined by X-ray crystallography. The ir and Raman spectra were observed for both isomers of 2,3,4-trichloro-pentanes and 2,2,3-trichloro-butane at room temperature and in the crystalline states. The force constant refinement procedure was divided into two steps. In the first step, force constants related to adjacently chlorinated units such as -CHCl-CHCl-CHCl - were refined by using meso and racemic isomers of 2,3,4 -trichloro-pentanes, meso and racemic isomers of 2,4-dichloro -pentanes, and two trans isomers (MRSM, MRRM) of 2,3-dichloro -butanes. In the next step, the force constants related to CCl_2 were refined by using trans and gauche isomers of 2,2-dichloro-butane, 2,2-dichloro -propane, and trans, gauche and gauche (-) forms of 2,2,3-trichloro-butane. The final refined force constants are tabulated. To validate the transferability of the refined force constants, the normal frequencies were calculated for 2-chloro-butane, 3-chloro-pentane, and syndiotactic, isotactic, and heterotactic isomers of 2,4,6-trichloro-heptanes, as well as syndiotactic PVC. The calculated bands well matched the observed bands. In particular, C-Cl stretches, which are sensitive to the conformation, were predicted within 5 cm^{-1} . The ir and Raman spectra of PVC and CPVC for the five different chlorine contents, 57.70%, 61.48%, 63.34%, 67.92%, and 70.92% were observed. To elucidate these spectra, normal mode analyses (NMA) were conducted for tetrad PVC fragments (010101010), and for CPVC fragments such as (010111010), (011111010), (0102010), (0121010), (0121110), (010202010), and (010202110). (Numerical designation was used for the three carbons in CPVC: CH_2 = 0, CHCl = 1, CCl_2 = 2). According to the NMA, CH_2 groups of the center r unit of r-r-m, and m-r-m heterotactic PVC tetrads were chlorinated in the early stages of the reaction.

Chough, Sung Hyo

188

NMR spectra of transient radicals  

SciTech Connect

A time-resolved method for the study of structure and spin dynamics of transient radicals in liquids is described. Pulsed electron beam or pulsed laser irradiation is used to create transient radicals in solution. Irradiation is carried out in the field of a variable electromagnet, and the diamagnetic products are transferred rapidly using a fast flow system to an NMR probe. During the radical reaction, a 0.5 to 10 ..mu..s rf pulse is applied to the reacting sample at an appropriate frequency, corresponding to a nuclear energy level spacing of the given radical. Nuclear spin level population changes in the radical are transferred to its reaction product and detected as intensity changes in their NMR spectra. The method is illustrated using radiolyzed sodium malonate.

Trifunac, A.D.; Chiu, T.M.; Nuttall, R.H.D.

1984-01-01

189

Graviton Spectra in String Cosmology  

E-print Network

We propose to uncover the signature of a stringy era in the primordial Universe by searching for a prominent peak in the relic graviton spectrum. This feature, which in our specific model terminates an $\\omega^3$ increase and initiates an $\\omega^{-7}$ decrease, is induced during the so far overlooked bounce of the scale factor between the collapsing deflationary era (or pre-Big Bang) and the expanding inflationary era (or post-Big Bang). We evaluate both analytically and numerically the frequency and the intensity of the peak and we show that they may likely fall in the realm of the new generation of interferometric detectors. The existence of a peak is at variance with ordinarily monotonic (either increasing or decreasing) graviton spectra of canonical cosmologies; its detection would therefore offer strong support to string cosmology.

Massimo Galluccio; Marco Litterio; Franco Occhionero

1996-08-02

190

Reflectance spectra of primitive chondrites  

NASA Astrophysics Data System (ADS)

We are studying a wide sample of pristine carbonaceous chondrites from the NASA Antarctic collection in order to get clues on the physico-chemical processes occurred in the parent bodies of these meteorites. We are obtaining laboratory reflectance spectra of different groups of carbonaceous chondrites, but here we focus in CM and CI chondrites. We discuss the main spectral features that can be used to identify primitive carbonaceous asteroids by remote sensing techniques. Two different spectrometers were used covering the entire 0.3 to 30 ?m electromagnetic window. Only a handful of Near Earth Objects (NEOs) exhibit bands or features clearly associated with aqueous alteration. Among them are the target asteroids of Osiris Rex and Marco Polo-R missions.

Trigo-Rodríguez, J. M.; Moyano-Cambero, C. E.; Llorca, J.

2013-05-01

191

Quantifying on- and off-fault deformation in Tibet with geometric moment rates (Invited)  

Microsoft Academic Search

Interseismic GPS measurements from the greater Tibetan plateau region demonstrate that the relative motion between the Indian and Eurasian plates is partitioned across a boundary exceeding 1000 km in width. These geodetic observations have been used to argue that continental deformation may be described as ``diffuse'' or ``plate-like'', two apparently contradictory views. Generally, tests of these hypotheses have relied on

B. J. Meade; J. P. Loveless

2009-01-01

192

The Spitzer Atlas of Stellar Spectra  

E-print Network

We present the Spitzer Atlas of Stellar Spectra (SASS), which includes 159 stellar spectra (5 to 32 mic; R~100) taken with the Infrared Spectrograph on the Spitzer Space Telescope. This Atlas gathers representative spectra of a broad section of the Hertzsprung-Russell diagram, intended to serve as a general stellar spectral reference in the mid-infrared. It includes stars from all luminosity classes, as well as Wolf-Rayet (WR) objects. Furthermore, it includes some objects of intrinsic interest, like blue stragglers and certain pulsating variables. All the spectra have been uniformly reduced, and all are available online. For dwarfs and giants, the spectra of early-type objects are relatively featureless, dominated by Hydrogen lines around A spectral types. Besides these, the most noticeable photospheric features correspond to water vapor and silicon monoxide in late-type objects and methane and ammonia features at the latest spectral types. Most supergiant spectra in the Atlas present evidence of circumstell...

Ardila, David R; Makowiecki, Wojciech; Stauffer, John; Song, Inseok; Rho, Jeonghee; Fajardo-Acosta, Sergio; Hoard, D W; Wachter, Stefanie

2010-01-01

193

Passport examination by polarized infrared spectra.  

PubMed

In this study, a new nondestructive technique for passport examination is proposed. In this technique, linearly polarized light is used to measure Fourier transform infrared (FT-IR) reflectance spectra of films on the biographical data page. Thirty genuine and thirty-five counterfeit Japanese passports and five marketed films pasted on name cards were examined. The measured spectra were analyzed as follows. The absorption spectra were obtained by the Kramers-Kronig transformations of reflectance spectra. The peak ratios were then calculated from the absorption spectra by adding the peak areas at 1126 and 1263 cm(-1) and dividing the result by the peak area at 1727 cm(-1). When nonpolarized light was used, the samples could not be distinguished by comparing the peak ratios. However, when polarized light was used, they were successfully distinguished by the comparison. Therefore, polarized light is useful for the forensic discrimination of passport films by the measurement of FT-IR spectra. PMID:17567291

Sugawara, Shigeru

2007-07-01

194

THE SUZAKU VIEW OF THE SWIFT/BAT ACTIVE GALACTIC NUCLEI. II. TIME VARIABILITY AND SPECTRA OF FIVE 'HIDDEN' ACTIVE GALACTIC NUCLEI  

SciTech Connect

The fraction of Compton-thick sources is one of the main uncertainties left in understanding the active galactic nucleus (AGN) population. The Swift Burst Alert Telescope (BAT) all-sky survey for the first time gives us an unbiased sample of AGNs for all but the most heavily absorbed sources N {sub H} > 10{sup 25} cm{sup -2}). Still, the BAT spectra (14-195 keV) are time averaged over months of observations and therefore hard to compare with softer spectra from the Swift XRT or other missions. This makes it difficult to distinguish between Compton-thin and Compton-thick models. With Suzaku, we have obtained simultaneous hard (>15 keV) and soft (0.3-10 keV) X-ray spectra for five Compton-thick candidate sources. We report on the spectra and a comparison with the BAT and earlier XMM observations. Based on both flux variability and spectral shape, we conclude that these hidden sources are not Compton thick. We also report on a possible correlation between excess variance and Swift BAT luminosity from the 16 day binned light curves, which holds true for a sample of both absorbed (four sources), unabsorbed (eight sources), and Compton-thick (Circinus) AGNs, but is weak in the 64 day binned BAT light curves.

Winter, Lisa M. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309 (United States); Mushotzky, Richard F. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Terashima, Yuichi [Department of Physics, Ehime University, Matsuyama, Ehime 790-8577 (Japan); Ueda, Yoshihiro [Department of Astronomy, University of Kyoto, Kyoto 606-8502 (Japan)

2009-08-20

195

Exploiting the full potential of photometric quasar surveys: optimal power spectra through blind mitigation of systematics  

NASA Astrophysics Data System (ADS)

We present optimal measurements of the angular power spectrum of the XDQSOz catalogue of photometric quasars from the Sloan Digital Sky Survey. These measurements rely on a quadratic maximum likelihood estimator that simultaneously measures the auto- and cross-power spectra of four redshift samples, and provides minimum-variance, unbiased estimates even at the largest angular scales. Since photometric quasars are known to be strongly affected by systematics such as spatially-varying depth and stellar contamination, we introduce a new framework of extended mode projection to robustly mitigate the impact of systematics on the power spectrum measurements. This technique involves constructing template maps of potential systematics, decorrelating them on the sky, and projecting out modes which are significantly correlated with the data. Our method is able to simultaneously process several thousands of non-linearly correlated systematics, and mode projection is performed in a blind fashion. Using our final power spectrum measurements, we find a good agreement with theoretical predictions, and no evidence for further contamination by systematics. Extended mode projection not only obviates the need for aggressive sky and quality cuts, but also provides control over the level of systematics in the measurements, enabling the search for small signals of new physics while avoiding confirmation bias.

Leistedt, Boris; Peiris, Hiranya V.

2014-10-01

196

THE OPTICALLY UNBIASED GRB HOST (TOUGH) SURVEY. VI. RADIO OBSERVATIONS AT z {approx}< 1 AND CONSISTENCY WITH TYPICAL STAR-FORMING GALAXIES  

SciTech Connect

The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of {approx}825 M{sub Sun} yr{sup -1}, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least {approx}63% of GRB hosts have SFR < 100 M{sub Sun} yr{sup -1} and at most {approx}8% can have SFR > 500 M{sub Sun} yr{sup -1}. For the undetected hosts the mean radio flux (<35 {mu}Jy 3{sigma}) corresponds to an average SFR < 15 M{sub Sun} yr{sup -1}. Moreover, {approx}> 88% of the z {approx}< 1 GRB hosts have ultraviolet dust attenuation A{sub UV} < 6.7 mag (visual attenuation A{sub V} < 3 mag). Hence, we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A{sub UV} of GRB hosts are consistent with those of Lyman break galaxies, H{alpha} emitters at similar redshifts, and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z {approx}< 1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought.

Michalowski, M. J.; Dunlop, J. S. [SUPA (Scottish Universities Physics Alliance), Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Kamble, A.; Kaplan, D. L. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Hjorth, J.; Malesani, D.; Fynbo, J. P. U.; Kruehler, T. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark); Reinfrank, R. F. [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); Bonavera, L. [Instituto de Fisica de Cantabria, CSIC-Universidad de Cantabria, Avda. de los Castros s/n, E-39005 Santander (Spain); Castro Ceron, J. M. [Department of Radio Astronomy, Madrid Deep Space Communications Complex (INTA-NASA/INSA), Ctra. M-531, km. 7, E-28.294 Robledo de Chavela (Madrid) (Spain); Ibar, E. [UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Garrett, M. A. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Jakobsson, P. [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavik (Iceland); Levan, A. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Massardi, M. [INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Pal, S. [ICRAR, University of Western Australia, 35 Stirling Highway, Crawley, WA (Australia); Sollerman, J. [Oskar Klein Centre, Department of Astronomy, AlbaNova, Stockholm University, SE-10691 Stockholm (Sweden); Tanvir, N. R. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Van der Horst, A. J., E-mail: mm@roe.ac.uk [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098XH Amsterdam (Netherlands); and others

2012-08-20

197

X-ray spectra of supernova remnants  

NASA Technical Reports Server (NTRS)

X-ray spectra were obtained from fields in three supernova remnants with the solid state spectrometer of the HEAO 2 satellite. These spectra, which contain lines from K-shell transitions of several abundant elements with atomic numbers between 10 and 22, were compared with various models, including some of spectra that would be produced by adiabatic phase remnants when the time-dependence of the ionization is considered.

Szymkowiak, A. E.

1985-01-01

198

Principal Component Analysis of SDSS Stellar Spectra  

Microsoft Academic Search

We apply the Principal Component Analysis (PCA) to 140,000 stellar spectra obtained by SDSS. In order to avoid non-linear variation of spectra with effective temperature, we bin the sample into 0.02 mag wide intervals of the g-r color (-0.20spectra within the measurement noise.

Rosalie C. McGurk; Z. Ivezic; A. E. Kimball

2009-01-01

199

Energy spectra of quantum rings.  

PubMed

Quantum mechanical experiments in ring geometries have long fascinated physicists. Open rings connected to leads, for example, allow the observation of the Aharonov-Bohm effect, one of the best examples of quantum mechanical phase coherence. The phase coherence of electrons travelling through a quantum dot embedded in one arm of an open ring has also been demonstrated. The energy spectra of closed rings have only recently been studied by optical spectroscopy. The prediction that they allow persistent current has been explored in various experiments. Here we report magnetotransport experiments on closed rings in the Coulomb blockade regime. Our experiments show that a microscopic understanding of energy levels, so far limited to few-electron quantum dots, can be extended to a many-electron system. A semiclassical interpretation of our results indicates that electron motion in the rings is governed by regular rather than chaotic motion, an unexplored regime in many-electron quantum dots. This opens a way to experiments where even more complex structures can be investigated at a quantum mechanical level. PMID:11677600

Fuhrer, A; Lüscher, S; Ihn, T; Heinzel, T; Ensslin, K; Wegscheider, W; Bichler, M

2001-10-25

200

Functional Regression for Quasar Spectra  

E-print Network

The Lyman-alpha forest is a portion of the observed light spectrum of distant galactic nuclei which allows us to probe remote regions of the Universe that are otherwise inaccessible. The observed Lyman-alpha forest of a quasar light spectrum can be modeled as a noisy realization of a smooth curve that is affected by a `damping effect' which occurs whenever the light emitted by the quasar travels through regions of the Universe with higher matter concentration. To decode the information conveyed by the Lyman-alpha forest about the matter distribution, we must be able to separate the smooth `continuum' from the noise and the contribution of the damping effect in the quasar light spectra. To predict the continuum in the Lyman-alpha forest, we use a nonparametric functional regression model in which both the response and the predictor variable (the smooth part of the damping-free portion of the spectrum) are function-valued random variables. We demonstrate that the proposed method accurately predicts the unobserv...

Ciollaro, Mattia; Freeman, Peter; Genovese, Christopher; Lei, Jing; O'Connell, Ross; Wasserman, Larry

2014-01-01

201

Infrared spectra of protostellar collapse  

NASA Technical Reports Server (NTRS)

Theoretical models of the formation of low mass stars by cloud collapse predict that OI(63 micrometers) and IR rotational lines of CO and H2O dominate the cooling in the freefalling region 10-1000 AU from the protostar. The freefalling gas supersonically hits the protoplanetary disk orbiting the protostar, forming an accretion shock with strong IR emission in rotational lines of H2O and OH, and OI(63 microns). The accretion shock spectra and line profiles depend on the mass flux through the shock and the typical distance r-bar at which the freefalling gas strikes the disk. The line widths are of order the Keplerian speed, or approx. 10(r-bar/10AU)(exp -0.5) km/s, for the accretion shock lines, and less for the lines from the infalling gas. Measurements of the IR line fluxes and profiles from the freefalling gas and the accretion shock diagnoses how a protostar and disk are formed and requires high sensitivity and high spectral and spatial resolving power. SOFIA will be the optimum observatory for many of these lines, although ISO will contribute and the KAO may make a few pioneering detections.

Hollenbach, David J.; Ceccarelli, Cecilia; Neufeld, David A.; Tielens, Alexander G. G. M.

1995-01-01

202

Helium Spectra in Atonic Mechanics  

NASA Astrophysics Data System (ADS)

In our model of the helium atom, we postulate that the angular momentum of each electron divided by equals an integer, n, plus a fraction,?n. By minimizing the energy the energy of the helium atom, we find that the ?n values are a function of the total angular momenta, J, irrespective of the integer, n. We thus obtain a set of ?n values for the singlet and triplet states of helium. The ?n values are related to fractals. In our model, we made adjustments to the electron mass so that the calculated energy values agree with the seventeen values for the singlet 1s-ns configurations listed in NIST Atomic Spectra Database Levels Data. The adjustments to the electron mass were usually very close to unity except for the ground state for which the adjustment was ˜5%. (Adjustments like these suggest that we may be able to study three-body effects with spectral accuracy.) By doing this, we had good agreement with all of the NIST spectral values for helium (191 lines of He I, and 243 lines of He II). This conceptually and mathematically simple procedure can be used for other atoms.

Phillips, Alfred, Jr.

2008-03-01

203

Reflectance spectra of subarctic lichens  

NASA Technical Reports Server (NTRS)

Lichens constitute a major portion of the ground cover of high latitude environments, but little has been reported concerning their in situ solar spectral reflectance properties. Knowledge of these properties is important for the interpretation of remotely sensed observations from high latitude regions, as well as in studies of high latitude ecology and energy balance climatology. The spectral reflectance of common boreal vascular plants is similar to that of vascular plants of the midlatitudes. The dominant lichens, in contrast, display variable reflectance patterns in visible wavelengths. The relative reflectance peak at 0.55 microns, common to green vegetation, is absent or indistinct in spectra of pervasive boreal forest and tundra lichens, despite the presence of chlorophyll in the inner algal cells. Lichens of the dominant genus, Cladina, display strong absorption of ultraviolet energy and short-wavelength blue light relative to their absorption in other visible wavelengths. Since the Cladinae dominate both the surface vegetation in open woodlands of the boreal forest and the low arctic tundra, their unusual spectral reflectance patterns will enable accurate monitoring of the boreal forest-tundra ecotone and detection of its vigor and movement in the future.

Petzold, Donald E.; Goward, Samuel N.

1988-01-01

204

Spectra and pseudospectra for pipe Poiseuille flow  

Microsoft Academic Search

Numerically computed spectra and pseudospectra are presented for the linear operator that governs the temporal evolution of infinitesimal perturbations of laminar flow in an infinite circular pipe at Reynolds numbers 1000, 3000 and 10 000. The spectra lie strictly inside the stable complex half-plane, but the pseudospectra protrude significantly into the unstable half-plane, reflecting the large linear transient growth that

Anne E. Trefethen; Lloyd N. Trefethen; Peter J. Schmid

1994-01-01

205

DYNAMIC SPECTRA OF JUPITER'S DECAMETRIC EMISSION, 1961  

Microsoft Academic Search

Sources for the decametric emission from Jupiter are suggested and ; evidence for their existence presented. Dynamic spectra for negative and ; positive drift emission and composite spectra are displayed and discussed. An ; explanation of the emission based on Jupiter's possession of energetic radiation ; belts similar to earth's is presented. (D.C.W.);

James W. Warwick

1963-01-01

206

Spectra of Quarkonia at Finite Temperature  

E-print Network

Finite-temperature spectra of heavy quarkonia are calculated by combining potential model and thermofield dynamics formalisms. The mass spectra of the heavy quarkonia with various quark contents are calculated. It is found that binding mass of the quarkonium decreases as temperature increases.

D. U. Matrasulov; F. C. Khanna; Kh. T. Butanov; Kh. Yu. Rakhimov

2006-06-02

207

Mössbauer Spectra of Clays and Ceramics  

NASA Astrophysics Data System (ADS)

The physical, chemical and mineralogical aspects of the use of Mössbauer spectroscopy in studies of clay-based ceramics are described. Mössbauer spectra of pottery clays fired under oxidising, reducing and changing conditions are explained, and the possibilities of using Mössbauer spectra to derive information on the firing temperatures and the kiln atmosphere during firing in antiquity are discussed and illustrated by examples.

Wagner, F. E.; Wagner, U.

2004-06-01

208

Signal processing with higher-order spectra  

Microsoft Academic Search

The strengths and limitations of correlation-based signal processing methods are discussed. The definitions, properties, and computation of higher-order statistics and spectra, with emphasis on the bispectrum and trispectrum are presented. Parametric and nonparametric expressions for polyspectra of linear and nonlinear processes are described. The applications of higher-order spectra in signal processing are discussed

C. L. Nikias; J. M. Mendel

1993-01-01

209

POLLUX : a database of synthetic stellar spectra  

E-print Network

Synthetic spectra are needed to determine fundamental stellar and wind parameters of all types of stars. They are also used for the construction of theoretical spectral libraries helpful for stellar population synthesis. Therefore, a database of theoretical spectra is required to allow rapid and quantitative comparisons to spectroscopic data. We provide such a database offering an unprecedented coverage of the entire Hertzsprung-Russell diagram. We present the POLLUX database of synthetic stellar spectra. For objects with Teff 25 000 K). Their spectra are computed with CMF_FLUX. Both high resolution (R>150 000) optical spectra in the range 3 000 to 12 000 A and spectral energy distributions extending from the UV to near--IR ranges are presented. These spectra cover the HR diagram at solar metallicity. We propose a wide variety of synthetic spectra for various types of stars in a format that is compliant with the Virtual Observatory standards. A user--friendly web interface allows an easy selection of spectra...

Palacios, A; Josselin, E; Martins, F; Plez, B; Belmas, M; Lebre, A

2010-01-01

210

POLLUX: a database of synthetic stellar spectra  

Microsoft Academic Search

Aims: Synthetic spectra are needed to determine fundamental stellar and wind parameters of all types of stars. They are also used for the construction of theoretical spectral libraries helpful for stellar population synthesis. Therefore, a database of theoretical spectra is required to allow rapid and quantitative comparisons to spectroscopic data. We provide such a database offering an unprecedented coverage of

A. Palacios; M. Gebran; E. Josselin; F. Martins; B. Plez; M. Belmas; A. Lèbre

2010-01-01

211

STELLAR SPECTRA A. Basic Line Formation  

E-print Network

STELLAR SPECTRA A. Basic Line Formation R.J. Rutten Sterrekundig Instituut Utrecht February 6, 2007 classification ("Annie Cannon") 3 1.1 Stellar spectra morphology-Boltzmann calibration of the Harvard sequence ("Cecilia Payne") 7 2.1 Payne's line strength diagram

Walter, Frederick M.

212

The Science of Light: Stellar Spectra  

NSDL National Science Digital Library

This web page, part of the Annenberg Media Teachers' Labs, enables visitors to analyze the spectrum of a star and determine its composition. The site displays spectra of various elements and then shows a stellar spectrum, so the user can match spectral lines and identify elements in the star. Several samples of stellar spectra are provided.

2007-07-25

213

COMPUTER INTERPRETATION OF POLLUTANT MASS SPECTRA  

EPA Science Inventory

The objective of this research was to improve systems for computer examination of the mass spectra of unknown pollutants. For this we have developed a new probability based matching (PBM) system for the retrieval of mass spectra from a large data base, and have substantially impr...

214

Handbook of mass spectra of environmental contaminants  

Microsoft Academic Search

This handbook is a collection of the electron impact mass spectra of 394 commonly encountered environmental pollutants. Each page is devoted to the examination of a single pollutant, which is presented as a bar graph always starting at M\\/z = 40. Each spectra is determined by analyses of data in EPA data bases. The major fragment ions are correlated with

Hites

1985-01-01

215

Combinatorial Approaches for Mass Spectra Recalibration  

Microsoft Academic Search

Mass spectrometry has become one of the most popular analysis techniques in Proteomics and Systems Biology. With the creation of larger datasets, the automated recalibration of mass spectra becomes important to ensure that every peak in the sample spectrum is correctly assigned to some peptide and protein. Algorithms for recalibrating mass spectra have to be robust with respect to wrongly

Sebastian Böcker; Veli Mäkinen

2005-01-01

216

Mid-Infrared Spectra of Mercury  

NASA Technical Reports Server (NTRS)

Mid-infrared (8-13 microns) spectra of radiation emitted from the surface of solar system objects can be interpreted in terms of surface composition. However, the spectral features are weak, and require exceptionally high signal-to-noise ratio spectra to detect them. Ground-based observations of spectra in this region are plagued by strong atmospheric absorptions from water and ozone. High-altitude balloon measurements that avoid atmospheric absorptions can be affected by contamination of the optics by dust. We have developed a technique to obtain mid-infrared spectra of Mercury that minimizes these problems. The resulting spectra show evidence of transparency features that can be used to qualitatively characterize the surface composition. Additional information is contained in the original extended abstract.

Cooper, B.; Potter, A. E.; Killen, R. M.; Morgan, T. H.

2001-01-01

217

Thermal infrared spectra of the Moon  

NASA Technical Reports Server (NTRS)

Contrary to recent assertions in the literature, lunar emission spectra obtained at an altitude of 32 km with a balloon-borne telescope are virtually undistorted by atmospheric absorption, except in the ozone region. These spectra have been found to correlate closely with laboratory emission spectra of returned lunar samples measured in a simulated lunar environment. Thus, lunar spectra obtained with the balloon-borne telescope system are the standards against which groundbased spectral measurements of the Moon should be compared. Comparison of balloon-borne measurements with recent groundbased spectral measurements suggests that the latter suffer from some source of systematic error. When high-quality lunar spectra are available, they will be best interpreted by comparison with returned lunar samples, rather than terrestrial minerals or rocks, because of subtle spectral differences between lunar and terrestrial minerals perhaps associated with incipient alteration of the latter.

Salisbury, John W.; Murcray, D. G.; Williams, W. J.; Blatherwick, R. D.

1995-01-01

218

Principal Component Analysis of SDSS Stellar Spectra  

E-print Network

We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong non-linear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g-r color (-0.20spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration (SEGUE) Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS. The SDSS stellar spect...

McGurk, Rosalie C; Ivezic, Zeljko

2010-01-01

219

Photoelectron spectra of transition-metal carbonyl complexes: comparison with the spectra of adsorbed CO  

Microsoft Academic Search

(Received 27 January 1978) The uv and x-ray photoelectron spectra of carbon monoxide and transition-metal (TM) carbonyl complexes have been studied. The systematic changes in these spectra were recorded as the number of metal atoms in the complexes was increased and as the bonding configuration of the CO changed. The observations on TM carbonyl complexes are compared to the spectra

E. W. Plummer; W. R. Salaneck; J. S. Miller

1978-01-01

220

Optical spectra and covalent chemistry of fulleropyrrolidines  

NASA Astrophysics Data System (ADS)

Low-temperature vibronic spectra of two fulleropyrrolidines (1-methyl-3,4-FP and 1-methyl-2(4-pyridine)-3,4-FP) embedded in crystalline toluene matrix have been studied. Two-component composition of the spectra has been established and charge-transfer-excitation origin of the structureless component has been suggested. Fine-structured Shpol'skii spectra were observed for 1-methyl-3,4-FP, which made possible to perform the vibrational analysis of its vibronic spectra. General similarities of the absorption spectra of fulleropyrrolidines and C60 molecules along with significant difference in their details have been discussed. A detailed interpretation of the C60 spectra serves as a basis for analyzing the spectra of the derivatives. Quantum-chemical study is based on the effectively-unpaired-electron concept for the fullerene molecule. Computations have been performed for the singlet states of the molecules in unrestricted Hartree-Fock approximation implemented in AM1 semiempirical quantum chemical codes of the CLUSTER-Z1 software. The population of the HOMO and LUMO of the molecules under study alongside with the lowering of the molecules symmetry have been proposed to explain the spectral features observed.0

Razbirin, B. S.; Starukhin, A. N.; Nelson, D. K.; Sheka, E. F.; Prato, Me

221

Analysis of atmospheric spectra for trace gases  

NASA Technical Reports Server (NTRS)

The objective is the comprehensive analysis of high resolution atmospheric spectra recorded in the middle-infrared region to obtain simultaneous measurements of coupled parameters (gas concentrations of key trace constituents, total column amounts, pressure, and temperature) in the stratosphere and upper troposphere. Solar absorption spectra recorded at 0.002 and 0.02 cm exp -1 resolutions with the University of Denver group's balloon-borne, aircraft borne, and ground-based interferometers and 0.005 to 0.01 cm exp -1 resolution solar spectra from Kitt Peak are used in the analyses.

Rinsland, Curtis P.; Seals, Robert K., Jr.; Smith, Mary Ann H.; Goldman, Aaron; Murcray, David G.; Murcray, Frank J.

1990-01-01

222

Negative Ion Photoelectron Spectra of Halomethyl Anions  

NASA Astrophysics Data System (ADS)

Halomethyl anions undergo a significant geometry change upon electron photodetachment, resulting in multiple extended vibrational progressions in the photoelectron spectra. The normal mode analysis that successfully models photoelectron spectra when geometry changes are modest is unable to reproduce the experimental data using physically reasonable parameters. A three-dimensional anharmonic coupled-mode analysis was employed to accurately reproduce the observed vibrational structure. We present the 364 nm negative ion photoelectron spectra of the halomethyl anions CHX_2^- and CDX_2^- (X = Cl, Br, I) and report electron affinities, vibrational frequencies, and geometries.

Vogelhuber, Kristen M.; Wren, Scott W.; McCoy, Anne B.; Ervin, Kent M.; Lineberger, W. Carl

2009-06-01

223

Angular Power Spectra with Finite Counts  

E-print Network

Angular anisotropy techniques for cosmic diffuse radiation maps are powerful probes, even for quite small data sets. A popular observable is the angular power spectrum; we present a detailed study applicable to any unbinned source skymap S(n) from which N random, independent events are observed. Its exact variance, which is due to the finite statistics, depends only on S(n) and N; we also derive an unbiased estimator of the variance from the data. First-order effects agree with previous analytic estimates. Importantly, heretofore unidentified higher-order effects are found to contribute to the variance and may cause the uncertainty to be significantly larger than previous analytic estimates---potentially orders of magnitude larger. Neglect of these higher-order terms, when significant, may result in a spurious detection of the power spectrum. On the other hand, this would indicate the presence of higher-order spatial correlations, such as a large bispectrum, providing new clues about the sources. Numerical si...

Campbell, Sheldon S

2014-01-01

224

Microwave spectra of some volatile organic compounds  

NASA Technical Reports Server (NTRS)

A computer-controlled microwave (MRR) spectrometer was used to catalog reference spectra for chemical analysis. Tables of absorption frequency, peak absorption intensity, and integrated intensity are included for 26 volatile organic compounds, all but one of which contain oxygen.

White, W. F.

1975-01-01

225

Theoretical spectra of terrestrial exoplanet surfaces  

E-print Network

We investigate spectra of airless rocky exoplanets with a theoretical framework that self-consistently treats reflection and thermal emission. We find that a silicate surface on an exoplanet is spectroscopically detectable ...

Hu, Renyu

226

[Resonance raman spectra of linear polymer molecule].  

PubMed

The present paper summarizes the characteristics of resonance Raman spectra of the linear polymer molecule, and its relations with the molecular structure, including: electronic spectra(ultraviolet-visible absorption spectrum), Raman spectra characteristics and its relations with external field; Modulation relation between the electron energy gap and CC atom vibration; Several experimental results were obtained: The UV-visible absorption spectra are red-shifted with decreasing temperature, increasing solvent density and reducing solution concentration, and because the linear polymer molecule has high structured order, decreasing pi electron energy gap; extended pi electronic delocalization, large effective conjugation length, large intensity of the Raman activity, Ramrnan spectrum are red-shifted, with large scattering cross section. "Am plitude modes" are the ideal theory models to study the linear polymer molecule. PMID:25095421

Zhang, Xue; Li, Shuo; Liu, Tie-Cheng; Sun, Cheng-Lin; Li, Zuo-Wei

2014-05-01

227

Contribution to the study of turbulence spectra  

NASA Technical Reports Server (NTRS)

An apparatus suitable for turbulence measurement between ranges of 1 to 5000 cps and from 6 to 16,000 cps was developed and is described. Turbulence spectra downstream of the grills were examined with reference to their general characteristics, their LF qualities, and the effects of periodic turbulence. Medium and HF are discussed. Turbulence spectra in the boundary layers are similarly examined, with reference to their fluctuations at right angles to the wall, and to lateral fluctuations. Turbulence spectra in a boundary layer with suction to the wall is discussed. Induced turbulence, and turbulence spectra at high Reynolds numbers. Calculations are presented relating to the effect of filtering on the value of the correlations in time and space.

Dumas, R.

1979-01-01

228

PIA update: Correlation analyses of mass spectra  

NASA Technical Reports Server (NTRS)

The PIA instrument aboard the Giotto spacecraft (a time of flight spectrometer) has been presented elsewhere. The mass spectra used in this analysis were decoded and mass numbers assigned according to the presence of carbon and silver, using the global values for these elements in their spectral absence. The results presented here were obtained using a frequency of occurrence based on analysis which correlated how often mass numbers appear in the mass spectra and which mass numbers tend to occur together in the same spectra; no amplitude information is utilized. The data are presented as plots of mass vs coincident mass for different subsets of the PIA data set, with both axes having units of atomic mass. Frequency contours are plotted at approximately five percent contour intervals, relative to the maximum AMU occurrence in that plot. The plots presented are symmetrical about the matrix diagonal, i.e., every mass is coincident with itself in a given spectra.

Mason, L. W.; Clark, B. C.

1988-01-01

229

Numerical modelling of mineral impact ionisation spectra  

NASA Astrophysics Data System (ADS)

We present model mass spectra of fayalite, forsterite, enstatite, ferrosilite, magnesiohornblende, ferrohornblende, anorthites, albite and Mg-Al spinel, as would be generated by a medium resolution impact ionisation cosmic dust mass spectrometer. Spectral peak intensities are found using ion relative sensitivity factors (RSFs) derived for TOF-SIMS mineral analysis. We demonstrate that, although TOF-SIMS RSFs are a reasonable approximation for the RSFs of impact ionisation, the RSFs for some important elements, such as Si, may differ by up to a factor of four. However, the TOF-SIMS RSFs are in general a valuable tool for predicting the peak intensities of inorganic species in impact ionisation mass spectra of minerals and mineral mixtures. The model spectra are used to estimate the ability of a medium resolution mass spectrometer to discriminate between different mineral compositions, and compared with impact ionisation mass spectra of anorthite cosmic dust analogue particles.

Hillier, Jon K.; Fiege, K.; Trieloff, M.; Srama, R.

2013-12-01

230

POLLUX: a database of synthetic stellar spectra  

NASA Astrophysics Data System (ADS)

Aims: Synthetic spectra are needed to determine fundamental stellar and wind parameters of all types of stars. They are also used for the construction of theoretical spectral libraries helpful for stellar population synthesis. Therefore, a database of theoretical spectra is required to allow rapid and quantitative comparisons to spectroscopic data. We provide such a database offering an unprecedented coverage of the entire Hertzsprung-Russell diagram. Methods: We present the POLLUX database of synthetic stellar spectra. For objects with Teff ? 6000 K, MARCS atmosphere models are computed and the program TURBOSPECTRUM provides the synthetic spectra. ATLAS12 models are computed for stars with 7000 K ? Teff ? 15 000 K. SYNSPEC gives the corresponding spectra. Finally, the code CMFGEN provides atmosphere models for the hottest stars (Teff > 25 000 K). Their spectra are computed with CMF_FLUX. Both high resolution (R > 150 000) optical spectra in the range 3000 to 12 000 Å and spectral energy distributions extending from the UV to near-IR ranges are presented. These spectra cover the HR diagram at solar metallicity. Results: We propose a wide variety of synthetic spectra for various types of stars in a format that is compliant with the Virtual Observatory standards. A user-friendly web interface allows an easy selection of spectra and data retrieval. Upcoming developments will include an extension to a large range of metallicities and to the near-IR high resolution spectra, as well as a better coverage of the HR diagram, with the inclusion of models for Wolf-Rayet stars and large datasets for cool stars. The POLLUX database is accessible at http://pollux.graal.univ-montp2.fr/ and through the Virtual Observatory. Copy of database is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/516/A13

Palacios, A.; Gebran, M.; Josselin, E.; Martins, F.; Plez, B.; Belmas, M.; Lèbre, A.

2010-06-01

231

On the Photoelectron Spectra of Li4  

NASA Technical Reports Server (NTRS)

The most stable structure for Li4(-) is found to be the rhombus. Electron detachment from this structure does not seem able to fully explain the photoelectron spectra. The computed results are consistent with those Rao, Jena, and Ray who have proposed that the experimental spectra consists of a superposition of detachment from the Li4(-) rhombus and tetrahedron, forming the singlet and triplet states of Li4, respectively.

Bauschlicher, Charles W., Jr.; Arnold, James O. (Technical Monitor)

1996-01-01

232

Area spectra of near extremal black holes  

E-print Network

Motivated by Maggiore's new interpretation of quasinormal modes, starting from the first law of thermodynamics of black holes, we investigate area spectra of a near extremal Schwarzschild de sitter black hole and a higher dimensional near extremal Reissner-Nordstrom de sitter black hole. We show that the area spectra of all these black holes are equally spaced and irrelevant to the parameters of black holes.

Deyou Chen; Haitang Yang; Xiaotao Zu

2010-04-16

233

Diffuse emission and pathological Seyfert spectra  

NASA Technical Reports Server (NTRS)

In this annual ROSAT status report, the diffuse emission and spectra from Seyfert galaxies are examined. Three papers are presented and their contents include the soft x-ray properties and spectra of a binary millisecond pulsar, the PSPC and HRI observations of a Starburst/Seyfert 2 Galaxy, and an analysis of the possibility of x-ray luminous starbursts in the Einstein Medium Sensitivity Survey.

Halpern, Jules P.

1995-01-01

234

Artificial intelligence analysis of paraspinal power spectra  

Microsoft Academic Search

Objective. As an aid to discrimination of sufferers with back pain an artificial intelligence neural network was constructed to differentiate paraspinal power spectra.Design. Clinical investigation using surface electromyography.Method. The surface electromyogram power spectra from 60 subjects, 33 non-back-pain sufferers and 27 chronic back pain sufferers were used to construct a back propagation neural network that was then tested. Subjects were

CW Oliver; WJ Atsma

1996-01-01

235

Universality of spectra of black holes  

NASA Astrophysics Data System (ADS)

Using exclusively an action variable, we quantize a static, spherically symmetric black hole. The spacings of the quantized entropy spectrum and area spectrum are found to be equal to the values given by Bekenstein. Interestingly, we find the spectra are independent of the hairs of the black holes and the mode of motion of a particle outside the spacetime, which depends only on the intrinsic properties of the gravity. Our result shows that the spectra are universal provided the spacetime owns a horizon.

Zeng, Xiao-Xiong; Li, Qiang; Han, Yi-Wen

2014-11-01

236

Comparison of Spectra in Unsequenced Species  

Microsoft Academic Search

We introduce a new algorithm for the mass spectrometric identification of proteins. Experimental spectra obtained by tandem\\u000a MS\\/MS are directly compared to theoretical spectra generated from proteins of evolutionarily closely related organisms. This\\u000a work is motivated by the need of a method that allows the identification of proteins of unsequenced species against a database\\u000a containing proteins of related organisms. The

Freddy Cliquet; Guillaume Fertin; Irena Rusu; Dominique Tessier

2009-01-01

237

Beta spectra deconvolution for liquid scintillation counting  

Microsoft Academic Search

This study presents the first results of a deconvolution method for Liquid Scintillation complex spectra. The method has been\\u000a developed by means of the software MATLAB and is based on the utilization of Fourier Transforms. Its main target is to obtain\\u000a a fast calculation procedure capable to unfold complex spectra without requiring any preliminary knowledge of the peak shapes\\u000a of

Romolo Remetti; Alessandro Sessa

2011-01-01

238

Power and phase spectra for detonating cord  

SciTech Connect

A simple mathematical model is presented for a detonating cord seismic source. This model can be used for most configurations of detonating cord. Power and phase spectra are calculated. Numerical results are presented for a straight strand detonated in the center. Time delays associated with the initiation of vertically travelling energy at low frequencies can be determined from the phase spectra. 2 references, 5 figures.

Burkhard, N.R.

1983-11-01

239

Neutron sources and spectra from cold fusion  

Microsoft Academic Search

Deterministic methods are used to calculate the neutron and photon sources and spectra that would develop if fusion reactions were occurring in cold fusion experimental devices. The results from the calculations give the neutron and gamma spectra resulting from a 2.45-MeV and a 14.1 MeV neutron source. The neutron source strength from certain (gamma,n) and (alpha,n) reactions are also determined.

T. A. Parish; R. T. Perry; W. B. Wilson

1990-01-01

240

Matching Peptide Sequences with Mass Spectra  

Microsoft Academic Search

\\u000a We study a method of mapping both mass spectra and sequences to feature vectors and the correlation between them. The method\\u000a of calculating the feature vector from mass spectra is presented, together with a method for representing sequences. A correlation\\u000a metric comparing both representations is studied. It shows strong correlation between two representation for the same peptides.\\u000a It also demostrates

K. W. Lau; B. J. Stapley; S. Hubbard; H. Yin

2005-01-01

241

Absorption spectra reconstruction using Voigt profiles  

NASA Astrophysics Data System (ADS)

The identification of the components of algal absorption spectra can be made mathematically through either derivative or spectral deconvolution analyses. This work establishes a methodology for identifying phytoplankton pigments from absorption spectra by combining the derivative and spectral deconvolution methods and interpreting the results with the knowledge of the major light absorbing pigments. This was achieved a) by locating the position of the absorption peaks present in the spectra of different algal groups through the derivative analysis, b) by fitting a combination of Gaussian-Lorentzian or Voigt shaped bands, centered at these peaks, to the original spectra and c) by using pigment analysis via HPLC to provide the biological background for identifying these bands and peaks. The results of this study show that the derivative method can be used successfully in monocultures and natural populations to identify pigments by their individual absorption peaks. Secondly, a good agreement has been found between the original spectra and the reconstructed spectra which were a Voigt combination. The HPLC analysis provided the objective platform for the biological interpretation of the bands.

Aguirre-Gomez, R.; Weeks, Alison R.; Boxall, Simon R.

1997-02-01

242

Evaluation of kurtosis of JONSWAP spectra  

NASA Astrophysics Data System (ADS)

Typical random wind waves in the sea are characterized by broad-band spectra and quasi-Gaussian statistics. While the evolution of wave field spectra in the ocean is well studied, very little is known about how departure of wave statistics from Gaussian depends on characteristics of wave spectra. This information is needed for many applications but is very difficult to extract from observations outside laboratory. It is common to characterize the departure of wave statistics from Gaussianity by value of kurtosis, a fourth-order statistical moment. Non-zero values of kurtosis mean an increased or decreased probability of extreme waves (compared to that in a Gaussian sea), which is important for assessing the risk of freak waves and other applications. For quasi-Gaussian waves there are two contributions to kurtosis. The first one, C4(b), is due to bound harmonics, while the second one, "dynamic kurtosis" C4(d), is linked to nonlinear wave-wave interactions. Under standard weak turbulence assumptions Janssen (2003) derived expressions for both components of kurtosis in terms of energy spectra. However, since the evaluation of the resulting 6-dimensional integrals is technically challenging, it has not been implemented for any experimental wave spectra. Here we evaluate C4(d) and C4(b) for the JONSWAP spectra, a widely used family of parametrisations of the observed spectra. We choose the k-form of the JONSWAP spectrum with the peak at k = 1. The frequency spectra are considered in the range 0.5 < ? < 3. The magnitude of the spectra is specified by parameter ?, where ? is proportional to the square of the steepness. The range of ? corresponds to the range of steepness from 0.04 to 0.3. The JONSWAP parameter ? characterizing "peakedness" of the spectra. ? is taken from 1 to 10. Angular distributions of the (cos?)N type are considered for several values of N. Thus we find behaviour of both components of kurtosis in the three-dimensional parameter space (?,?,N) and their sensitivity to approximations of the spectral shape. This provides a good idea on the degree of departure of wave statistics from Gaussian for realistic wave fields.

Annenkov, Sergei; Shrira, Victor

2013-04-01

243

Linewidth and lifetime of atomic levels and the time evolution of spectra and coincidence spectra  

SciTech Connect

The time-dependent theory of an atomic cascade decay process is discussed. We show that it is useful to measure the spectra of the emitted particles (electrons or photons) as a function of time and introduce time-dependent spectra and time-dependent coincidence spectra. The analysis reveals that there are several timescales involved in the atomic cascades and in the respective spectra. The work prepares the ground for the discussion of molecules, clusters, and solids, where the nuclear dynamics strongly participate in the cascade decay process making it much more complex.

Chiang, Y.-C.; Kuleff, Alexander I.; Cederbaum, Lorenz S. [Theoretische Chemie, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany); Demekhin, Philipp V. [Institute fuer Physik, Experimental-Physik IV, Universitaet Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel (Germany); Scheit, Simona [Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba, 153-8902 Tokyo (Japan)

2010-03-15

244

Fingerprints of correlation in electronic spectra Lucia Reining  

E-print Network

Fingerprints of correlation in electronic spectra Lucia Reining Theoretical Spectroscopy Group #12 Interaction leads to........... additional excitations Fingerprints of correlation in electronic spectra #12

Botti, Silvana

245

Disk-averaged synthetic spectra of Mars.  

PubMed

The principal goal of the NASA Terrestrial Planet Finder (TPF) and European Space Agency's Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earthsized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of a Mars-like planet to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra. We explore the detectability as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPFC) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model. This model uses observational data as input to generate a database of spatially resolved synthetic spectra for a range of illumination conditions and viewing geometries. The model was validated against spectra recorded by the Mars Global Surveyor-Thermal Emission Spectrometer and the Mariner 9-Infrared Interferometer Spectrometer. Results presented here include disk-averaged synthetic spectra, light curves, and the spectral variability at visible and mid-infrared wavelengths for Mars as a function of viewing angle, illumination, and season. We also considered the differences in the spectral appearance of an increasingly ice-covered Mars, as a function of spectral resolution, signal-to-noise and integration time for both TPF-C and TPFI/ Darwin. PMID:16078866

Tinetti, Giovanna; Meadows, Victoria S; Crisp, David; Fong, William; Velusamy, Thangasamy; Snively, Heather

2005-08-01

246

Climatology of tropospheric vertical velocity spectra  

NASA Technical Reports Server (NTRS)

Vertical velocity power spectra obtained from Poker Flat, Alaska; Platteville, Colorado; Rhone Delta, France; and Ponape, East Caroline Islands using 50-MHz clear-air radars with vertical beams are given. The spectra were obtained by analyzing the quietest periods from the one-minute-resolution time series for each site. The lengths of available vertical records ranged from as long as 6 months at Poker Flat to about 1 month at Platteville. The quiet-time vertical velocity spectra are shown. Spectral period ranging from 2 minutes to 4 hours is shown on the abscissa and power spectral density is given on the ordinate. The Brunt-Vaisala (B-V) periods (determined from nearby sounding balloons) are indicated. All spectra (except the one from Platteville) exhibit a peak at periods slightly longer than the B-V period, are flat at longer periods, and fall rapidly at periods less than the B-V period. This behavior is expected for a spectrum of internal waves and is very similar to what is observed in the ocean (Eriksen, 1978). The spectral amplitudes vary by only a factor of 2 or 3 about the mean, and show that under quiet conditions vertical velocity spectra from the troposphere are very similar at widely different locations.

Ecklund, W. L.; Gage, K. S.; Balsley, B. B.; Carter, D. A.

1986-01-01

247

[Infrared and Raman spectra study on Tianhuang].  

PubMed

The Tianhuang stones, from Shoushan in China, were studied by using X-ray powder diffractometry (XRD), infrared (IR) spectroscopy and Raman spectroscopy to obtain the spectra characterization. Wave numbers 3621, 3629 and 3631 cm(-1) in the IR spectra and 3626, 3627 and 3632 cm(-1) in the Raman spectra are the characteristic peaks of dickitic Tianhuang, nacritic Tianhuang and illitic Tianhuang, respectively. Raman spectra assigned to OH are in good agreement with the IR results at 3550 -3750 cm(-1). Dickitic Tianhuang includes ordered dickite and disordered dickite. Compared with ordered dickite, the band assigned to OH3 of disordered dickite shifts to low-frequency by 8 cm(-1) and the relative intensity becomes stronger. The disorder structure may relate to the high level of Fe. The IR absorption spectra of nacritic Tianhuang superimposes strong peaks of dickite, indicating that IR absorption bands of dickite are stronger than that of nacrite at 3550-3750 cm(-1). The main mineral composition of illitic Tianhuang is 2M(1), while illite Tianhuang contains a small amount of 1M. All these characters provide a theoretical basis for the scientific identification of Tianhuang. PMID:23156769

Liu, Yun-gui; Chen, Tao

2012-08-01

248

Background noise spectra of global seismic stations  

SciTech Connect

Over an extended period of time station noise spectra were collected from various sources for use in estimating the detection and location performance of global networks of seismic stations. As the database of noise spectra enlarged and duplicate entries became available, an effort was mounted to more carefully select station noise spectra while discarding others. This report discusses the methodology and criteria by which the noise spectra were selected. It also identifies and illustrates the station noise spectra which survived the selection process and which currently contribute to the modeling efforts. The resulting catalog of noise statistics not only benefits those who model network performance but also those who wish to select stations on the basis of their noise level as may occur in designing networks or in selecting seismological data for analysis on the basis of station noise level. In view of the various ways by which station noise were estimated by the different contributors, it is advisable that future efforts which predict network performance have available station noise data and spectral estimation methods which are compatible with the statistics underlying seismic noise. This appropriately requires (1) averaging noise over seasonal and/or diurnal cycles, (2) averaging noise over time intervals comparable to those employed by actual detectors, and (3) using logarithmic measures of the noise.

Wada, M.M.; Claassen, J.P.

1996-08-01

249

Site frequency spectra from genomic SNP surveys.  

PubMed

Genomic survey data now permit an unprecedented level of sensitivity in the detection of departures from canonical evolutionary models, including expansions in population size and selective sweeps. Here, we examine the effects of seemingly subtle differences among sampling distributions on goodness of fit analyses of site frequency spectra constructed from single nucleotide polymorphisms. Conditioning on the observation of exactly two alleles in a random sample results in a site frequency spectrum that is independent of the scaled rate of neutral substitution (theta). Other sampling distributions, including conditioning on a single mutational event in the sample genealogy or randomly selecting a single mutation from a genealogy with multiple mutations, have distinct site frequency spectra that show highly significant departures from the predictions of the biallelic model. Some aspects of data filtering may contribute to significant departures of site frequency spectra from expectation, apart from any violation of the standard neutral model. PMID:19371756

Ganapathy, Ganeshkumar; Uyenoyama, Marcy K

2009-06-01

250

Neural Network Classification of Stellar Spectra  

NASA Astrophysics Data System (ADS)

The MK classification system as first proposed in 1943 by Morgan, Keenan & Kellman (1943) has been an important tool in stellar and galactic astrophysics. Currently, MK classification is a useful approach to obtaining general information on stellar spectra and selecting stars for further study. However, the existing manual methods of obtaining classifications are slow, making it infeasible for them to be applied to the vast numbers of spectra which will be obtained in future spectral surveys. In this project I investigate the application of artificial neural networks to the automation of MK spectral classification. For the purposes of this project, I digitized and reduced 100 objective prism plates taken from the Michigan Spectral Survey (Houk 1994). Using software I developed, I extracted a set of over 5000 spectra at a resolution of ~3 AA covering the wavelength range 3800-5200 AA (Bailer-Jones, Irwin & von Hippel 1997a). These spectra were used in conjunction with their two-dimensional classifications listed in Michigan Henry Draper Catalogue (Houk & Smith-Moore 1988 and references therein) to develop supervised neural network classifiers. I show that neural networks can give accurate spectral type classifications (1 sigma = 0.82 subtypes, sigmaRMS = 1.09 subtypes) across the full range of spectral types present in the database (B2-M7); I show also that the networks yield correct luminosity classes for over 95% of both dwarfs and giants with a high degree of confidence (Bailer-Jones, Irwin & von Hippel 1997b). The high level of reproducibility of neural network classifications is demonstrated and an analysis of the effect of the complexity of the neural network on its classifications is given. For the purposes of many analyses, stellar spectra contain a large amount of redundant (correlated) information. I investigate the application of Principal Components Analysis (PCA) to the optimal compression of spectra. I show that PCA can compress the spectra by a factor of over 30 whilst retaining more than 95% of the variance in the data set. Furthermore, this compression leads to no decrease in classifier performance, indicating that the PCA compression from 820 to 25 components results in no significant loss of relevant information. I also demonstrate how PCA acts as a filter of noise and bogus features in a spectrum and can be used to identify unusual spectra. The ultimate goal of stellar classification should be a physical parameterization of the stars. I examine the application of neural networks to the problem of obtaining physical parameters (Teff, log g etc.) directly from an observed spectrum, by training a neural network on synthetic spectra and then applying it to observed spectra (Bailer-Jones et al. 1997). By determining physical parameters in this way, any assumptions and limitations of an intermediate classification scheme are avoided. However, I have used the effective temperature (Teff) inferred by the networks to produce an accurate calibration of the MK system for dwarf, giant and sub-giant stars, based on the set of 5000 observed spectra. This calibration agrees well with a number of calibrations published in the literature. It is demonstrated through the metallicity dependence of the derived temperature calibration that the neural networks are sensitive to the metallicity features in the observed spectra. With further work it is likely that neural networks will be able to determine metallicity reliably using only the optical stellar spectrum.

Bailer-Jones, C. A. L.

1997-08-01

251

Consistency of the minimal supersymmetric GUT spectra  

SciTech Connect

We show that with proper accounting of convention-dependent phases the mass spectra evaluated by us in an earlier paper satisfy the trace, SU(5) reassembly and Goldstone counting consistency checks. Phase accounting shows that the transposition symmetry called Hermiticity will be manifest only if signs arising from the product of six phase factors are reinserted. This uncovers the errors in the claims of others (retracted in subsequent work) concerning the inconsistency of our results. The chiral multiplet spectra of the two calculations are equivalent. However our method also gives all gauge and gauge chiral spectra as well as a decomposition of all SO(10) minimal supersymmetric grand unified theory couplings, for both tensors and spinors, which are unavailable, even in principle, using the methods of the above papers.

Aulakh, Charanjit S. [Department of Physics, Panjab University, Chandigarh, India 160014 (India)

2005-09-01

252

Quantitative analysis of NMR spectra with chemometrics  

NASA Astrophysics Data System (ADS)

The number of applications of chemometrics to series of NMR spectra is rapidly increasing due to an emerging interest for quantitative NMR spectroscopy e.g. in the pharmaceutical and food industries. This paper gives an analysis of advantages and limitations of applying the two most common chemometric procedures, Principal Component Analysis (PCA) and Multivariate Curve Resolution (MCR), to a designed set of 231 simple alcohol mixture (propanol, butanol and pentanol) 1H 400 MHz spectra. The study clearly demonstrates that the major advantage of chemometrics is the visualisation of larger data structures which adds a new exploratory dimension to NMR research. While robustness and powerful data visualisation and exploration are the main qualities of the PCA method, the study demonstrates that the bilinear MCR method is an even more powerful method for resolving pure component NMR spectra from mixtures when certain conditions are met.

Winning, H.; Larsen, F. H.; Bro, R.; Engelsen, S. B.

2008-01-01

253

Multifrequency spectra of BL Lac objects  

NASA Technical Reports Server (NTRS)

A program to obtain simultaneous multifrequency spectra of BL Lacertae objects that are known X-ray sources is discussed. The IUE spectra are generally featureless and well-fitted by power law models. For the faintest exposures, Gaussian extraction of the spectrum can greatly impove the signal-to-noise. Most program objects vary in the ultraviolet, although the time scales are not known because of limited observing time. The broadband spectra of BL Lacs exhibit a range of characteristics but the curvature is always downward and the shape is generally smooth. This can be interpreted as synchrotron emission from a relativistic jet; different jet models are possible, and each allows a range of values for the bulk velocity, magnetic field strength, and electron density. Synchrotron models are not required, however an accretion disk model also gives a good fit to the ultraviolet-through-X-ray continuum.

Urry, C. M.; Kondo, Y.; Mufson, S. L.; Wandel, A.

1988-01-01

254

On the Individuality of Sleep EEG Spectra  

PubMed Central

Research in recent years has supported the hypothesis that many properties of the electroencephalogram (EEG) are specific to an individual. In this study, the intra- and inter-individual variations of sleep EEG signals were investigated. This was carried out by analyzing the stability of the average EEG spectra individually computed for the Rechtschaffen and Kales (RK) sleep stages. Six EEG channels were used to account for the topographical aspect of the analysis. Validity of the results was supported by considering a wide dataset of 174 subjects with normal sleep. Subjects spent two consecutive nights in the sleep laboratory during which EEG recordings were obtained. High similarity between average spectra of two consecutive nights was found considering an individual. More than 89% of the second night recordings were correctly assigned to their counterparts of the first night. The average spectra of sleep EEG computed for each RK sleep stage have shown a high degree of individuality. PMID:23997385

Lewandowski, Achim; Rosipal, Roman; Dorffner, Georg

2013-01-01

255

Combined and Comparative Analysis of Power Spectra  

NASA Astrophysics Data System (ADS)

In solar physics, especially in exploratory stages of research, it is often necessary to compare the power spectra of two or more time series. One may, for instance, wish to estimate what the power spectrum of the combined data sets might have been, or one may wish to estimate the significance of a particular peak that shows up in two or more power spectra. One may also on occasion need to search for a complex of peaks in a single power spectrum, such as a fundamental and one or more harmonics, or a fundamental plus sidebands, etc. Visual inspection can be revealing, but it can also be misleading. This leads one to look for one or more ways of forming statistics, which readily lend themselves to significance estimation, from two or more power spectra. We derive formulas for statistics formed from the sum, the minimum, and the product of two or more power spectra. A distinguishing feature of our formulae is that, if each power spectrum has an exponential distribution, each statistic also has an exponential distribution. The statistic formed from the minimum power of two or more power spectra is well known and has an exponential distribution. The sum of two or more powers also has a well-known distribution that is not exponential, but a simple operation does lead to an exponential distribution. Concerning the product of two or more power spectra, we find an analytical expression for the case n = 2, and a procedure for computing the statistic for n > 2. We also show that some quite simple expressions give surprisingly good approximations.

Sturrock, P. A.; Scargle, J. D.; Walther, G.; Wheatland, M. S.

2005-03-01

256

An improved algorithm for the retrieval of ocean wave spectra from synthetic aperture radar image spectra  

Microsoft Academic Search

An earlier algorithm for retrieving two-dimensional wave spectra from synthetic aperture radar (SAR) image spectra is improved by using a modified cost function and introducing an additional iteration loop in which the first-guess input spectrum is systematically updated. For this purpose a spectral partitioning scheme is applied in which the spectrum is decomposed into a finite number of distinct wave

S. Hasselmann; C. Brüning; K. Hasselmann; P. Heimbach

1996-01-01

257

What do spectra tell us about dynamics? How can we easily calculate spectra?  

E-print Network

· What do spectra tell us about dynamics? · How can we easily calculate spectra? · Case studies Frozen Gaussians Off-center guiding #12;The dream: provide a physically motivated basis set for chemical are guided by and act like classical trajectories; easy to run in many degrees of freedom #12;Many strategies

Simons, Jack

258

NMR spectra of androstane analogs of brassinosteroids  

NASA Astrophysics Data System (ADS)

We have used two-dimensional NMR spectroscopy to make a complete assignment of signals from the nuclei of hydrogen and carbon atoms in the spectra of brassinosteroids in the androstane series. We have confirmed the stereochemistry of the chiral centers and the structure of the molecules. We have studied the effect of the configuration of the 2,3-diol groups in the A ring of the steroids on the chemical shift of adjacent atoms in the 13C and 1H NMR spectra.

Baranovskii, A. V.; Litvinovskaya, R. P.; Aver'kova, M. A.; Khripach, N. B.; Khripach, V. A.

2007-09-01

259

Parallel Genetic Algorithm for Alpha Spectra Fitting  

NASA Astrophysics Data System (ADS)

We present a performance study of alpha-particle spectra fitting using parallel Genetic Algorithm (GA). The method uses a two-step approach. In the first step we run parallel GA to find an initial solution for the second step, in which we use Levenberg-Marquardt (LM) method for a precise final fit. GA is a high resources-demanding method, so we use a Beowulf cluster for parallel simulation. The relationship between simulation time (and parallel efficiency) and processors number is studied using several alpha spectra, with the aim of obtaining a method to estimate the optimal processors number that must be used in a simulation.

García-Orellana, Carlos J.; Rubio-Montero, Pilar; González-Velasco, Horacio

2005-01-01

260

Gravitational effects on planetary neutron flux spectra  

NASA Astrophysics Data System (ADS)

The effects of gravity on the planetary neutron flux spectra for planet Mars, and the lifetime of the neutron, were investigated using a modified one-dimensional diffusion accelerated neutral-particle transport code, coupled with a multigroup cross-section library tailored specifically for Mars. The results showed the presence of a qualitatively new feature in planetary neutron leakage spectra in the form of a component of returning neutrons with kinetic energies less than the gravitational binding energy (0.132 eV for Mars). The net effect is an enhancement in flux at the lowest energies that is largest at and above the outermost layer of planetary matter.

Feldman, W. C.; Drake, D. M.; O'dell, R. D.; Brinkley, F. W.; Anderson, R. C.

1989-01-01

261

Photoabsorption spectra of cationic mercury clusters  

SciTech Connect

The experimental photoabsorption spectra of singly charged cationic mercury clusters (Hg{sub N}{sup +}) show a sharp change in behavior at cluster size N=6. Both relativistic density functional theory (DFT) and wave function based methods reveal that this corresponds to a structural change from linear to three-dimensional isomers. The simulated electronic excitation spectra obtained from time-dependent relativistic DFT agree well with the experimental results. Our quantum theoretical treatment confirms the change from single electron-hole excitations in small linear clusters to plasmonlike collective transitions for the larger three-dimensional clusters.

Gaston, Nicola; Schwerdtfeger, Peter; Issendorff, Bernd von [Centre of Theoretical Chemistry and Physics, Institute of Fundamental Sciences, Massey University (Auckland Campus), Private Bag 102904, North Shore MSC, Auckland (New Zealand); Fakultaet fuer Physik, Universitaet Freiburg, H. Herderstrasse 3, D-79104 Freiburg (Germany)

2006-10-15

262

Principal Component Analysis of SDSS Stellar Spectra  

Microsoft Academic Search

We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra\\u000aobtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong\\u000anon-linear variation of spectra with effective temperature, the sample is\\u000abinned into 0.02 mag wide intervals of the g-r color (-0.20

Rosalie C. McGurk; Amy E. Kimball; Zeljko Ivezic

2010-01-01

263

Augmentation of ENDF/B fission product gamma-ray spectra by calculated spectra  

SciTech Connect

Gamma-ray spectral data of the ENDF/B-V fission product decay data file have been augmented by calculated spectra. The calculations were performed with a model using beta strength functions and cascade gamma-ray transitions. The calculated spectra were applied to individual fission product nuclides. Comparisons with several hundred measured aggregate gamma spectra after fission were performed to confirm the applicability of the calculated spectra. The augmentation was extended to a preliminary ENDF/B-VI file, and to beta spectra. Appendix C provides information on the total decay energies for individual products and some comparisons of measured and aggregate values based on the preliminary ENDF/B-VI files. 15 refs., 411 figs.

Katakura, J. (Japan Atomic Energy Research Inst., Tokai-mura, Naka-gun, Ibaraki-ken (Japan)) [Japan Atomic Energy Research Inst., Tokai-mura, Naka-gun, Ibaraki-ken (Japan); England, T.R. (Los Alamos National Lab., NM (United States)) [Los Alamos National Lab., NM (United States)

1991-11-01

264

Single site spectra of Zn porphin in triphenylene  

Microsoft Academic Search

Single site spectra of Zn porphin in triphenylene have been recorded at low temperature. There were three principal site species, each of which had slightly different fluorescence and absorption spectra. Because the spectra of each site were separately recorded, the confusion which resulted from the spectra of multiple site species in previous studies was eliminated. Vibrational assignments in the ground

Boris F. Kim; Joseph Bohandy

1977-01-01

265

SPECTRA: the sensor and its mission  

Microsoft Academic Search

The SPECTRA system will allow to achieve the scientific objectives by observing defined land targets in various spectral bands of the optical range of the electromagnetic spectrum from the Visible into the Thermal Infrared and with variable directions of observations. These observation capabilities are intended to provide a sampling of the Bi-directional Reflectance Distribution Function (BRDF) of the vegetation objects

U. del Bello

2002-01-01

266

Near infrared and ultraviolet spectra of TLEs  

NASA Astrophysics Data System (ADS)

We have found that sprites, beads and halos have similar optical spectra, but measurable differences in the near IR and near UV spectra. In particular, near infrared (NIR) and ultraviolet (UV) spectra of sprites, halos and beads corresponding to the first (1PG) and second positive (2PG) bands of N2 have been calculated for different observation altitudes from mountains (3.25 km) to airplanes (14 km), balloons (35 km) and space (nadir) platforms. The calculated non-equilibrium vibrational distribution functions (VDF) of the N2(B3?g) states in halos and beads show that the calculated NIR emissions produced through strong N2-1PG (B3?g ? A3?u+) transitions differ from the calculated sprite spectral emission patterns at ˜888 nm but particularly pronounced differences are found in the NIR spectral region at ˜1046 nm and ˜1231 nm corresponding to the N2-1PG (0,0) and (0,1) transitions, respectively. The blue - near UV spectra from N2-2PG (C3?u ? B3?g) transitions in halos and beads also exhibits slightly different spectral features when compared to the blue - near UV spectrum of sprites for bands originating from higher v-levels (v > 0) although they might not be above electronic noise level to be distinguished.

Gordillo-Vázquez, F. J.; Luque, A.; Simek, M.

2012-05-01

267

Phase noise spectra analysis for LC oscillators  

Microsoft Academic Search

This paper presents an analytical solution of the phase noise spectra for LC oscillators. Modeling noisy input processes as current impulse injections to the circuit, a linearized phase noise model is obtained by the Taylor series expansion method. For this linearized model, an analytic expression of the impulse sensitivity function (ISF) is derived. This is a new method to obtain

Hua Zhang; Dian Zhou; Yi Hu; Ruiming Li; Jianzhong Zhang

2005-01-01

268

Depolarized Rayleigh spectra of siloxane polymers  

Microsoft Academic Search

We report measurements of depolarized Rayleigh spectra IVH(?) of polyphenylmethyl siloxane (polymer A) in bulk and in carbon tetrachloride, of polydimethylphenylmethyl siloxane (copolymer B) in bulk, and of depolarized Rayleigh intensity IVH of polydiphenyl siloxane in carbon tetrachloride. From the temperature dependence and the concentration dependence of IVH, we were able to determine positive intermolecular and intramolecular static pair correlations

Y.-H. Lin; G. Fytas; B. Chu

1981-01-01

269

Squeezing spectra for nonlinear optical systems  

NASA Technical Reports Server (NTRS)

The squeezing spectra for the output fields of several intracavity nonlinear optical systems are obtained. It is shown that at critical points, e.g., the turning points for optical bistability, the threshold for parametric oscillation, and the self-pulsing instability in second-harmonic generation, perfect squeezing in the output field is, in principle, possible.

Collett, M. J.; Walls, D. F.

1985-01-01

270

Earth and Venus transmission spectra during transit  

E-print Network

Earth and Venus transmission spectra during transit 3rd Europlanet workshop ­ 4th PHC/Sakura meeting: Venus as a transiting exoplanet March 5 ­ 7 2012, Paris, France A. García Muñoz (Formerly at) Instituto de Astrofísica de Canarias, La Laguna, Spain Frank P. Mills (Venus work) The Australian National

Widemann, Thomas

271

CALCULATION OF ION ENERGY-DEPOSITION SPECTRA  

E-print Network

CALCULATION OF ION ENERGY-DEPOSITION SPECTRA IN SILICON, LITHIUM-FLUORIDE, BORON, AND BORON CARBIDE applications it is important to be able to calculate the energy deposited in the medium through which the ions for calculating the energy-deposition spectrum in various materials is presented and then applied to the design

Shultis, J. Kenneth

272

Combined and Comparative Analysis of Power Spectra  

E-print Network

In solar physics, especially in exploratory stages of research, it is often necessary to compare the power spectra of two or more time series. One may, for instance, wish to estimate what the power spectrum of the combined data sets might have been, or one may wish to estimate the significance of a particular peak that shows up in two or more power spectra. One may also on occasion need to search for a complex of peaks in a single power spectrum, such as a fundamental and one or more harmonics, or a fundamental plus sidebands, etc. Visual inspection can be revealing, but it can also be misleading. This leads one to look for one or more ways of forming statistics, which readily lend themselves to significance estimation, from two or more power spectra. We derive formulas for statistics formed from the sum, the minimum, and the product of two or more power spectra. A distinguishing feature of our formulae is that, if each power spectrum has an exponential distribution, each statistic also has an exponential distribution.

P. A. Sturrock; J. D. Scargle; G. Walther; M. S. Wheatland

2005-02-02

273

Atonic Mechanics of H and He Spectra  

NASA Astrophysics Data System (ADS)

We have created a new and simpler way to calculate atomic spectra than could be done with conventional quantum mechanics. Accordingly, we coin the term atonic mechanics. Spectra of hydrogen and helium are calculated. Atonic mechanics results are compared with NIST Atomic Spectra Database Levels Data He I taken from the NIST web site. Exact agreement is obtained, as we use an effective mass coefficient, m3, to account for three-body effects. The ground state (configuration 1s2 - term 1S) value of m3 is 0.9506109 where we expect three-body effects are strongest. The largest value of m3 is 1.0000868 (configuration 1s.5s - term 1S). As the outer electron energy further increases, m3 decreases monotonically to 0.9999242 where three-body effects diminish. This is for configuration 1s.15s - term 1S, the most energetic state that we considered. Although it is not done here, atonic mechanics may provide a way for modeling multi-body effects using atomic spectra.

Phillips, Alfred

2004-03-01

274

Disk-averaged synthetic spectra of Mars  

E-print Network

The principal goal of the NASA Terrestrial Planet Finder (TPF) and ESA Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earth-sized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of the planet Mars to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPF-C) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model which uses observational data as input to generate a database of spatially-resolved synthetic spectra for a range of illumination conditions (phase angles) and viewing geometries. Results presented here include disk averaged synthetic spectra, light-curves and the spectral variability at visible + mid-IR wavelengths for Mars as a function of viewing angle, illumination, season. We also considered the appearance of an increasingly frozen Mars and simulated its detection versus real Mars with TPF-C and TPF-I as a function of spectral resolving power, signal-to-noise, integration time.

Giovanna Tinetti; Victoria S. Meadows; David Crisp; William Fong; Thangasamy Velusamy; Heather Snively

2004-08-20

275

Correlation Functions Aid Analyses Of Spectra  

NASA Technical Reports Server (NTRS)

New uses found for correlation functions in analyses of spectra. In approach combining elements of both pattern-recognition and traditional spectral-analysis techniques, spectral lines identified in data appear useless at first glance because they are dominated by noise. New approach particularly useful in measurement of concentrations of rare species of molecules in atmosphere.

Beer, Reinhard; Norton, Robert H., Jr.

1989-01-01

276

Absorption spectra of cold dilute solid solutions  

SciTech Connect

Infrared absorption spectra have been obtained for some compounds trapped in crystalline solids by freezing liquid Xe, Kr, Ar, or CH/sub 4/ solutions. The optical quality of the solid solutions is good, and they have been cooled to approx.80 K in 1.35 cm sample thicknesses to study the absorption in fundamental vibrational bands of the solutes. In the cases discussed, the bands are narrow, with observed full widths at half-maximum absorbance 0.05--0.30 cm/sup -1/ greater than the instrumental resolution (0.18--0.29 cm/sup -1/). The spectra appear to be free of ''multiple site'' and solute aggregate absorptions. Spectra displaying isotropic splitting in bands of natural BCl/sub 3/, SeF/sub 6/, OsO/sub 4/, TiCl/sub 4/, and MoF/sub 6/ are presented, and band frequencies are compared with some results obtained in evaporative matrices, in the gas phase, and in liquid solutions. For this comparison we have obtained some spectra of SeF/sub 6/ and BCl/sub 3/ gas.

Holland, R.F.; Maier, W.B. II; Freund, S.; Beattie, W.H.

1983-06-01

277

SAMPI: Protein Identification with Mass Spectra Alignments  

Microsoft Academic Search

Background: Mass spectrometry based peptide mass fingerprints (PMFs) offer a fast, efficient, and robust method for protein identification. A protein is digested (usually by trypsin) and its mass spectrum is compared to simulated spectra for protein sequences in a database. However, existing tools for analyzing PMFs often suffer from missing or heuristic analysis of the significance of search results and

Hans-michael Kaltenbach; Andreas Wilke; Sebastian Böcker

2007-01-01

278

Mass Spectra Alignments and Their Significance  

Microsoft Academic Search

Mass Spectrometry has become one of the most popular analysis techniques in Genomics and Systems Biology. We investigate a general framework that allows the alignment (or matching) of any two mass spectra. In particular, we examine the alignment of a reference mass spectrum generated in silico from a database, with a measured sample mass spectrum. In this context, we assess

Sebastian Böcker; Hans-michael Kaltenbach

2005-01-01

279

Mass spectra alignments and their significance  

Microsoft Academic Search

Mass Spectrometry has become one of the most popular analysis techniques in Genomics and Systems Biology. We investigate a general framework that allows the alignment (or matching) of any two mass spectra. In particular, we examine the alignment of a reference mass spectrum generated in silico from a database, with a measured sample mass spectrum. In this context, we assess

Sebastian Böcker; Hans-michael Kaltenbach

2007-01-01

280

Photothermal deflection spectra of solid C 60  

Microsoft Academic Search

The optical absorption spectra of C60 single crystal and thin film in the weak- absorption region have been measured by photothermal deflection spectroscopy. The optical energy gaps, corresponding to optically forbidden transitions of weak absorption, were derived from Tauc plots. On comparison with the photothermal deflection spectrum of an amorphous semiconductor, the similarity suggests that the gap region of solid

Wei-ya Zhou; Si-shen Xie; Sheng-fa Qian; Gang Wang; Lu-xi Qian

1996-01-01

281

Spectra/Por Easy-to-Use  

E-print Network

dialysis which combine efficiency and convenience. They are pre-assembled dialy- sis tubes that floatSpectra/Por® Easy-to-Use Dialysis Membrane Products Micro DispoDialyzer® Float-A-Lyzer® DispoDialyzer® A Dialysis Device for Ultra Micro Volume Samples The Micro DispoDialyzer was developed for efficiently dia

Lebendiker, Mario

282

Variations on supersymmetry breaking and neutrino spectra  

SciTech Connect

The problem of generating light neutrinos within supersymmetric models is discussed. It is shown that the hierarchy of scales induced by supersymmetry breaking can give rise to suppression factors of the correct order of magnitude to produce experimentally allowed neutrino spectra.

Borzumati, F.; Hamaguchi, K.; Nomura, Y.; Yanagida, T.

2000-12-11

283

Processing and classification of protein mass spectra.  

PubMed

Among the many applications of mass spectrometry, biomarker pattern discovery from protein mass spectra has aroused considerable interest in the past few years. While research efforts have raised hopes of early and less invasive diagnosis, they have also brought to light the many issues to be tackled before mass-spectra-based proteomic patterns become routine clinical tools. Known issues cover the entire pipeline leading from sample collection through mass spectrometry analytics to biomarker pattern extraction, validation, and interpretation. This study focuses on the data-analytical phase, which takes as input mass spectra of biological specimens and discovers patterns of peak masses and intensities that discriminate between different pathological states. We survey current work and investigate computational issues concerning the different stages of the knowledge discovery process: exploratory analysis, quality control, and diverse transforms of mass spectra, followed by further dimensionality reduction, classification, and model evaluation. We conclude after a brief discussion of the critical biomedical task of analyzing discovered discriminatory patterns to identify their component proteins as well as interpret and validate their biological implications. PMID:16463283

Hilario, Melanie; Kalousis, Alexandros; Pellegrini, Christian; Müller, Markus

2006-01-01

284

The Transverse Proximity Effect in Quasar Spectra  

E-print Network

The Transverse Proximity Effect in Quasar Spectra G´abor Worseck Astrophysikalisches Institut field generated by the overall population of quasars and star-forming galaxies. In the vicinity of sources of UV photons, such as luminous high-redshift quasars, the UV radiation field is enhanced due

285

Chaotic spectra: How to extract dynamic information  

SciTech Connect

Nonlinear dynamics is applied to chaotic unassignable atomic and molecular spectra with the aim of extracting detailed information about regular dynamic motions that exist over short intervals of time. It is shown how this motion can be extracted from high resolution spectra by doing low resolution studies or by Fourier transforming limited regions of the spectrum. These motions mimic those of periodic orbits (PO) and are inserts into the dominant chaotic motion. Considering these inserts and the PO as a dynamically decoupled region of space, resonant scattering theory and stabilization methods enable us to compute ladders of resonant states which interact with the chaotic quasi-continuum computed in principle from basis sets placed off the PO. The interaction of the resonances with the quasicontinuum explains the low resolution spectra seen in such experiments. It also allows one to associate low resolution features with a particular PO. The motion on the PO thereby supplies the molecular movements whose quantization causes the low resolution spectra. Characteristic properties of the periodic orbit based resonances are discussed. The method is illustrated on the photoabsorption spectrum of the hydrogen atom in a strong magnetic field and on the photodissociation spectrum of H/sub 3//sup +/. Other molecular systems which are currently under investigation using this formalism are also mentioned. 53 refs., 10 figs., 2 tabs.

Taylor, H.S.; Gomez Llorente, J.M.; Zakrzewski, J.; Kulander, K.C.

1988-10-01

286

PIA update: Correlation analyses of mass spectra  

Microsoft Academic Search

The PIA instrument aboard the Giotto spacecraft (a time of flight spectrometer) has been presented elsewhere. The mass spectra used in this analysis were decoded and mass numbers assigned according to the presence of carbon and silver, using the global values for these elements in their spectral absence. The results presented here were obtained using a frequency of occurrence based

L. W. Mason; B. C. Clark

1988-01-01

287

LMM Auger primary excitation spectra of copper  

NASA Astrophysics Data System (ADS)

The shape and intensity of measured Auger peaks are strongly affected by extrinsic excitations due to electron transport out of the surface and to intrinsic excitations induced by the sudden creation of the two static core holes. Following a method developed for XPS in a previous work [N. Pauly, S. Tougaard, F. Yubero, Surf. Sci. 620 (2014) 17], we have calculated the effective energy-differential inelastic electron scattering cross-sections, including the effects of the surface and of the two core holes, within the dielectric response theory by means of the QUEELS-XPS software (QUantitative analysis of Electron Energy Losses at Surfaces for XPS). The Auger spectra are then modeled by convoluting this energy loss cross section with the primary excitation spectrum that accounts for all effects which are part of the initial Auger process, i.e. L-S coupling and vacancy satellite effects. The shape of this primary excitation spectrum is fitted to get close agreement between the theoretical and the experimental spectra obtained from X-ray excited Auger electron spectroscopy (XAES). We have performed these calculations of XAES spectra for various LMM Auger transitions of pure Cu (L3M45M45, L3M23M45, L3M23M23 and L2M45M45 transitions). We compare the resulting primary excitation spectra with theoretical results published in the literature and obtain reasonable quantitative agreement. In particular, we extract from experimental spectra quantitative intensities due to Coster-Kronig, shake-off and shake-up processes relative to the intensity from the “normal” Auger process.

Pauly, N.; Tougaard, S.; Yubero, F.

2014-12-01

288

Improved predictions of reactor antineutrino spectra  

SciTech Connect

Precise predictions of the antineutrino spectra emitted by nuclear reactors is a key ingredient in measurements of reactor neutrino oscillations as well as in recent applications to the surveillance of power plants in the context of nonproliferation of nuclear weapons. We report new calculations including the latest information from nuclear databases and a detailed error budget. The first part of this work is the so-called ab initio approach where the total antineutrino spectrum is built from the sum of all {beta} branches of all fission products predicted by an evolution code. Systematic effects and missing information in nuclear databases lead to final relative uncertainties in the 10-20% range. A prediction of the antineutrino spectrum associated with the fission of {sup 238}U is given based on this ab initio method. For the dominant isotopes we developed a more accurate approach combining information from nuclear databases and reference electron spectra associated with the fission of {sup 235}U, {sup 239}Pu, and {sup 241}Pu, measured at Institut Laue-Langevin (ILL) in the 1980s. We show how the anchor point of the measured total {beta} spectra can be used to suppress the uncertainty in nuclear databases while taking advantage of all the information they contain. We provide new reference antineutrino spectra for {sup 235}U, {sup 239}Pu, and {sup 241}Pu isotopes in the 2-8 MeV range. While the shapes of the spectra and their uncertainties are comparable to those of the previous analysis of the ILL data, the normalization is shifted by about +3% on average. In the perspective of the reanalysis of past experiments and direct use of these results by upcoming oscillation experiments, we discuss the various sources of errors and their correlations as well as the corrections induced by off-equilibrium effects.

Mueller, Th. A.; Lhuillier, D.; Letourneau, A. [Commissariat a l'Energie Atomique et aux Energies Alternatives, Centre de Saclay, IRFU/SPhN, FR-91191 Gif-sur-Yvette (France); Fallot, M.; Cormon, S.; Giot, L.; Martino, J.; Porta, A.; Yermia, F. [Laboratoire SUBATECH, Ecole des Mines de Nantes, Universite de Nantes, CNRS/IN2P3, 4 rue Alfred Kastler, FR-44307 Nantes Cedex 3 (France); Fechner, M.; Lasserre, T.; Mention, G. [Commissariat a l'Energie Atomique et aux Energies Alternatives, Centre de Saclay, IRFU/SPP, FR-91191 Gif-sur-Yvette (France)

2011-05-15

289

Raman spectra of carotenoids in natural products  

NASA Astrophysics Data System (ADS)

Resonance Raman spectra of naturally occurring carotenoids have been obtained from nautilus, periwinkle ( Littorina littorea) and clam shells under 514.5 nm excitation and these spectra are compared with the resonance Raman spectra obtained in situ from tomatoes, carrots, red peppers and saffron. The tomatoes, carrots and red peppers gave rise to resonance Raman spectra exhibiting a ?1 band at ca. 1520 cm -1, in keeping with its assignment to carotenoids with ca. nine conjugated carbon?carbon double bonds in their main chains, whereas the resonance Raman spectrum of saffron showed a ?1 band at 1537 cm -1 which can be assigned to crocetin, having seven conjugated carbon?carbon double bonds. A correlation between ?1 wavenumber location and effective conjugated chain length has been used to interpret the data obtained from the shells, and the wavenumber position (1522 cm -1) of the ?1 band of the carotenoid in the orange clam shell suggests that it contains nine conjugated double bonds in the main chain. However, the black periwinkle and nautilus shells exhibit ?1 bands at 1504 and 1496 cm -1, respectively. On the basis of the correlation between ?1 wavenumber location and effective conjugated chain length, this indicates that they contain carotenoids with longer conjugated chains, the former having ca. 11 double bonds and the latter ca. 13 or even more. Raman spectra of the nautilus, periwinkle and clam shells also exhibited a strong band at 1085 cm -1 and a doublet with components at 701 and 705 cm -1, which can be assigned to biogenic calcium carbonate in the aragonite crystallographic form.

Withnall, Robert; Chowdhry, Babur Z.; Silver, Jack; Edwards, Howell G. M.; de Oliveira, Luiz F. C.

2003-08-01

290

Improved predictions of reactor antineutrino spectra  

NASA Astrophysics Data System (ADS)

Precise predictions of the antineutrino spectra emitted by nuclear reactors is a key ingredient in measurements of reactor neutrino oscillations as well as in recent applications to the surveillance of power plants in the context of nonproliferation of nuclear weapons. We report new calculations including the latest information from nuclear databases and a detailed error budget. The first part of this work is the so-called ab initio approach where the total antineutrino spectrum is built from the sum of all ? branches of all fission products predicted by an evolution code. Systematic effects and missing information in nuclear databases lead to final relative uncertainties in the 10-20% range. A prediction of the antineutrino spectrum associated with the fission of U238 is given based on this ab initio method. For the dominant isotopes we developed a more accurate approach combining information from nuclear databases and reference electron spectra associated with the fission of U235, Pu239, and Pu241, measured at Institut Laue-Langevin (ILL) in the 1980s. We show how the anchor point of the measured total ? spectra can be used to suppress the uncertainty in nuclear databases while taking advantage of all the information they contain. We provide new reference antineutrino spectra for U235, Pu239, and Pu241 isotopes in the 2-8 MeV range. While the shapes of the spectra and their uncertainties are comparable to those of the previous analysis of the ILL data, the normalization is shifted by about +3% on average. In the perspective of the reanalysis of past experiments and direct use of these results by upcoming oscillation experiments, we discuss the various sources of errors and their correlations as well as the corrections induced by off-equilibrium effects.

Mueller, Th. A.; Lhuillier, D.; Fallot, M.; Letourneau, A.; Cormon, S.; Fechner, M.; Giot, L.; Lasserre, T.; Martino, J.; Mention, G.; Porta, A.; Yermia, F.

2011-05-01

291

ANALYSIS OF METHODS FOR DETECTING THE PROXIMITY EFFECT IN QUASAR SPECTRA  

SciTech Connect

Using numerical simulations of structure formation, we investigate several methods for determining the strength of the proximity effect in the H I Ly{alpha} forest. We analyze three high-resolution ({approx}10 kpc) redshift snapshots (z-bar=4,3, and 2.25) of a Hydro-Particle-Mesh simulation to obtain realistic absorption spectra of the H I Ly{alpha} forest. We model the proximity effect along the simulated sight lines with a simple analytical prescription based on the assumed quasar luminosity and the intensity of the cosmic UV background (UVB). We begin our analysis investigating the intrinsic biases thought to arise in the widely adopted standard technique of combining multiple lines of sight when searching for the proximity effect. We confirm the existence of these biases, albeit smaller than previously predicted with simple Monte Carlo simulations. We then concentrate on the analysis of the proximity effect along individual lines of sight. After determining its strength with a fiducial value of the UVB intensity, we construct the proximity effect strength distribution (PESD). We confirm that the PESD inferred from the simple averaging technique accurately recovers the input strength of the proximity effect at all redshifts. Moreover, the PESD closely follows the behaviors found in observed samples of quasar spectra. However, the PESD obtained from our new simulated sight lines presents some differences to that of simple Monte Carlo simulations. At all redshifts, we find a smaller dispersion of the strength parameters, the source of the corresponding smaller biases found when combining multiple lines of sight. After developing three new theoretical methods for recovering the strength of the proximity effect on individual lines of sight, we compare their accuracy to the PESD from the simple averaging technique. All our new approaches are based on the maximization of the likelihood function, albeit invoking some modifications. The new techniques presented here, in spite of their complexity, fail to recover the input proximity effect in an unbiased way, presumably due to some (unknown) higher order correlations in the spectrum. Thus, employing complex three-dimensional simulations, we provide strong evidence in favor of the PESD obtained from the simple averaging technique, as a method of estimating the UVB intensity, free of any intrinsic biases.

Dall'Aglio, Aldo [Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Gnedin, Nickolay Y., E-mail: adaglio@aip.d [Particle Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)

2010-10-10

292

The transit spectra of Earth and Jupiter  

NASA Astrophysics Data System (ADS)

In recent years, an increasing number of observations have been made of the transits of ‘Hot Jupiters’, such as HD 189733b, about their parent stars from the visible through to mid-infrared wavelengths, which have been modelled to derive the likely atmospheric structure and composition of these planets. As measurement techniques improve, the measured transit spectra of ‘Super-Earths’ such as GJ 1214b are becoming better constrained, allowing model atmospheric states to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets such as the Earth or cold planets like Jupiter, it is hoped that this might become practical in the coming decades and if so, it is of interest to determine what we might infer from such measurements. In this work we have constructed atmospheric models of the Solar System planets from 0.4 to 15.5 ?m that are consistent with ground-based and satellite observations and from these calculate the primary transit and secondary eclipse spectra (with respect to the Sun and typical M-dwarfs) that would be observed by a ‘remote observer’, many light years away. From these spectra we test what current retrieval models might infer about their atmospheric states and compare these with the ‘ground truths’ in order to assess: (a) the inherent uncertainties in transit spectra observations; (b) the relative merits of primary transit and secondary eclipse spectra; and (c) the advantages of acquiring directly imaged spectra of these planets. We find that observing secondary eclipses of the Solar System would not give sufficient information for determining atmospheric properties with 10 m-diameter telescopes from a distance of 10 light years, but that primary transits give much better information. We find that a single transit of Jupiter in front of the Sun could potentially be used to determine temperature and stratospheric composition, but for the Earth the mean atmospheric composition could only be determined if it were orbiting a much smaller M-dwarf. For both Jupiter and Earth we note that direct imaging with sufficient nulling of the light from the parent star theoretically provides the best method of determining the atmospheric properties of such planets.

Irwin, P. G. J.; Barstow, J. K.; Bowles, N. E.; Fletcher, L. N.; Aigrain, S.; Lee, J.-M.

2014-11-01

293

Semiclassical theory of weighted spectra for regular systems: Absorption spectra and decay rates  

Microsoft Academic Search

We derive a simple semiclassical representation to describe the large-scale structure of the spectrum of regular systems weighted by some arbitrary function W. Examples of weighted spectra are the width-weighted spectrum, which represents the decay rate of an unstable system, and the oscillator-strength-weighted spectrum, which represents the photoabsorption rate. Semiclassical representations of such spectra involve stationary-phase contributions, which are periodic

M. W. Beims; V. Kondratovich; J. B. Delos

2000-01-01

294

Raman spectra of shocked minerals. I - Olivine  

NASA Technical Reports Server (NTRS)

The Raman spectra of olivine contained in a chip of the Twin Sisters Peak (Washington) dunite shocked to 22.2 GPa is shown to be identical to that of unshocked olivine in the same rock. The Raman spectra of powder of the rock shocked to 20.1 GPa and of chips shocked to 59.5 GPa and 60.7 GPa display strong and broad low-frequency features with crests at 475/cm, 556/cm, and 572/cm, and broad high-frequency features near 1100/cm. It is suggested that these features are due to the formation of olivine glass with a considerable degree of three-dimensional Si-O-Si linkage having scattered domains of greatly variable grain size, internal structure, and chemical composition.

Heymann, D.; Celucci, T. A.

1988-01-01

295

Theoretical rotation-torsion spectra of HSOH.  

PubMed

Rotation-torsion spectra of HSOH, involving the vibrational ground state and the fundamental torsional state, have been simulated at T = 300 K. The simulations are carried out with the variational computer program TROVE in conjunction with recently reported ab initio potential energy and electric dipole moment surfaces. HSOH is a near-prolate-symmetric top at equilibrium and the simulated spectra are of perpendicular-band-type with strong R-branch and Q-branch transitions. Recently, an anomalous (b-type-transition)/(c-type-transition) intensity ratio in the vibrational-ground-state (r)Q(K(a))-branches of HSOH has been experimentally observed. Our calculations reproduce correctly the anomaly and show that it originates in the large-amplitude torsional motion of HSOH. We analyze our theoretical results in order to explain the effect and to provide unambiguous (b/c)-type-transition assignments. PMID:20526504

Yachmenev, Andrey; Yurchenko, Sergei N; Jensen, Per; Baum, Oliver; Giesen, Thomas F; Thiel, Walter

2010-08-01

296

High resolution derivative spectra in remote sensing  

NASA Technical Reports Server (NTRS)

The use of derivative spectra is an established technique in analytical chemistry for the elimination of background signals and for resolving overlapping spectral features. Application of this technique for tackling analogous problems such as interference from soil background reflectance in the remote sensing of vegetation or for resolving complex spectra of several target species within individual pixels in remote sensing is proposed. Methods for generating derivatives of high spectral resolution data are reviewed. Results of experiments to test the use of derivatives for monitoring chlorosis in vegetation show that derivative spectral indices are superior to conventional broad-band spectral indices such as the near-infrared/red reflectance ratio. Conventional broad-band indices are sensitive to both leaf cover as well as leaf color. New derivative spectral indices which were able to monitor chlorosis unambiguously were identified. Potential areas for the application of this technique in remote sensing are considered.

Demetriades-Shah, Tanvir H.; Steven, Michael D.; Clark, Jeremy A.

1990-01-01

297

Measurement and interpretation of plutonium spectra  

SciTech Connect

The atomic spectroscopic data available for plutonium are among the rickest of any in the periodic system. They include high-resolution grating and Fourier-transform spectra as well as extensive Zeeman and isotope-shift studies. We summarize the present status of the term analysis and cite the configurations that have been identified. A least-squares adjustment of a parametric Hamiltonian for configurations of both Pu I and Pu II has shown that almost all of the expected low levels are now known. The use of a model Hamiltonian applicable to both lanthanide and actinide atomic species has been applied to the low configurations of Pu I and Pu II making use of trends predicted by ab initio calculations. This same model has been used to describe the energy levels of Pu/sup 3 +/ in LaCl/sub 3/, and an extension has permitted preliminary calculations of the spectra of other valence states.

Blaise, J.; Fred, M.S.; Carnall, W.T.; Crosswhite, H.M.; Crosswhite, H.

1982-01-01

298

Specific heat of multifractal energy spectra.  

PubMed

Motivated by the self-similar character of energy spectra demonstrated for quasicrystals, we investigate the case of multifractal energy spectra, and compute the specific heat associated with simple archetypal forms of multifractal sets as generated by iterated maps. We considered the logistic map and the circle map at their threshold to chaos. Both examples show nontrivial structures associated with the scaling properties of their respective chaotic attractors. The specific heat displays generically log-periodic oscillations around a value that characterizes a single exponent, the "fractal dimension," of the distribution of energy levels close to the minimum value set to 0. It is shown that when the fractal dimension and the frequency of log oscillations of the density of states are large, the amplitude of the resulting log oscillation in the specific heat becomes much smaller than the log-periodic oscillation measured on the density of states. PMID:11461222

da Silva, L R; Vallejos, R O; Tsallis, C; Mendes, R S; Roux, S

2001-07-01

299

An approach to heavy quarkonium spectra  

NASA Astrophysics Data System (ADS)

An application of the recently introduced method [M. Çapak et al., J. Math. Phys. 52, 102102 (2011)] to the bound-state eigenvalue problem in the elementary quarkonium potential V(r) = -a/r + br + cr2 is described, proved and illustrated for c\\bar {c} and b\\bar {b} systems. The quasi- and conditionally-exactly solvable spin-averaged mass spectra of heavy quarkonia are obtained in compact forms. The comparison of the present predictions with those of other theories in the related literature, together with the available data, has shown the success of the model used in this work and also revealed that the use of different confinings in the perturbed Coulomb potential descriptions has no considerable effect on the mass spectra of such systems.

Cançelik, Y.; Gönül, B.

2014-10-01

300

Inflation and alternatives with blue tensor spectra  

NASA Astrophysics Data System (ADS)

We study the tilt of the primordial gravitational waves spectrum. A hint of blue tilt is shown from analyzing the BICEP2 and POLARBEAR data. Motivated by this, we explore the possibilities of blue tensor spectra from the very early universe cosmology models, including null energy condition violating inflation, inflation with general initial conditions, and string gas cosmology, etc. For the simplest G-inflation, blue tensor spectrum also implies blue scalar spectrum. In general, the inflation models with blue tensor spectra indicate large non-Gaussianities. On the other hand, string gas cosmology predicts blue tensor spectrum with highly Gaussian fluctuations. If further experiments do confirm the blue tensor spectrum, non-Gaussianity becomes a distinguishing test between inflation and alternatives.

Wang, Yi; Xue, Wei

2014-10-01

301

Model atmospheres, predicted spectra, and colors  

NASA Technical Reports Server (NTRS)

Theoretical models of stellar atmospheres and the process of forming a spectrum are reviewed with particular reference to the spectra of B stars. In the case of classical models the stellar atmosphere is though to consist of plane parallel layers of gas in which radiative and hydrostatic equilibrium exists. No radiative energy is lost or gained in the model atmosphere, but the detailed shape of the spectrum is changed as a result of the interactions with the ionized gas. Predicted line spectra using statistical equilibrium local thermodynamic equilibrium (LTE), and non-LTE physics are compared and the determination of abundances is discussed. The limitations of classical modeling are examined. Models developed to demonstrate what motions in the upper atmosphere will do to the spectrum and to explore the effects of using geometries different from plane parallel layer are reviewed. In particular the problem of radiative transfer is addressed.

1982-01-01

302

8- to 13-micron spectra of asteroids  

NASA Astrophysics Data System (ADS)

It is pointed out that thermal emission from asteroids reaches a maximum in the 10- to 20-micron region. In connection with the present investigation, a uniform set of spectra was obtained in the 8- to 13-micron region for 12 asteroids (together with additional observations of 19 Fortuna). These spectra provide a potentially valuable data set for future use (e.g., with IRAS data). The main conclusion from the obtained results is that diagnostic emission features of the type observed by Feierberg et al. (1983) are not common in C- and M-type asteroids. Optical studies of 19 Fortuna do not reveal any unusual properties which distinguish it from other C-type asteroids observed.

Green, S. F.; Eaton, N.; Aitken, D. K.; Roche, P. F.; Meadows, A. J.

1985-05-01

303

Multiphoton effects in coherent radiation spectra  

NASA Astrophysics Data System (ADS)

At measurements of the spectra of intense gamma radiation produced by ultrarelativistic electrons in periodic structures, pileup of arrivals to the detector of several photons from one electron can cause significant deviations of the measured spectrum from the classically evaluated one. The description of experiments then requires summation of all multiphoton contributions. We describe the corresponding resummation procedure for the photon spectral intensity, as well as for the photon multiplicity spectrum, and apply it to the study of radiation spectra with a mix of coherent and incoherent contributions. The impact of multiphoton effects on the radiation spectrum shape is investigated. The limit of high photon multiplicity for the coherent part of the radiation is explored in detail. A method for reconstruction of the underlying single-photon spectrum from the multiphoton one is formulated.

Bondarenco, M. V.

2014-07-01

304

Electronic and vibrational spectra of diphenylmethane  

NASA Astrophysics Data System (ADS)

From the critical analyses of Raman and infrared spectra, different normal modes of vibration of diphenylmethane (DPM) have been identified. The near ultraviolet absorption spectra of the molecule are found to consist of two band systems, one around 220 nm and the other around 270 nm with respective f-values 5.23×10 -2 and 6.44×10 -3. The first system is broad and shows few diffuse structures, whereas the later one exhibits very well-resolved structure. They are respectively assigned as 1La and 1Lb bands. The Raman excitation profiles of several normal modes have been analyzed to get structural and other information of different excited electronic states.

Mishra, T.; De, A. K.; Chattopadhyay, S.; Mallick, P. K.; Sett, P.

2005-02-01

305

Inflation and Alternatives with Blue Tensor Spectra  

E-print Network

We study the tilt of the primordial gravitational waves spectrum. A hint of blue tilt is shown from analyzing the BICEP2 and POLARBEAR data. Motivated by this, we explore the possibilities of blue tensor spectra from the very early universe cosmology models, including null energy condition violating inflation, inflation with general initial conditions, and string gas cosmology, etc. For the simplest G-inflation, blue tensor spectrum also implies blue scalar spectrum. In general, the inflation models with blue tensor spectra indicate large non-Gaussianities. On the other hand, string gas cosmology predicts blue tensor spectrum with highly Gaussian fluctuations. If further experiments do confirm the blue tensor spectrum, non-Gaussianity becomes a distinguishing test between inflation and alternatives.

Yi Wang; Wei Xue

2014-03-23

306

Combinatorial Approaches for Mass Spectra Recalibration  

Microsoft Academic Search

Mass spectrometry has become one of the most popular analysis techniques\\u000d\\u000a\\u0009in Proteomics and Systems Biology. With the creation of larger datasets,\\u000d\\u000a\\u0009the automated recalibration of mass spectra becomes important to\\u000d\\u000a\\u0009ensure that every peak in the sample spectrum is correctly assigned\\u000d\\u000a\\u0009to some peptide and protein. Algorithms for recalibrating mass spectra\\u000d\\u000a\\u0009have to be robust with respect to wrongly

Sebastian Bocker; Veli Makinen

2008-01-01

307

Surface Electronic Spectra Detected by Atomic Desorption  

SciTech Connect

Using continuously tunable laser excitation of KI we measure the velocity profiles and the yield of desorbing hyperthermal iodine atoms as a function of photon energy. Based on the theoretical model of desorption we demonstrate that these spectra display a signature of a surface exciton and constitute a new sensitive method of surface specific desorption spectroscopy. Our results demonstrate that creation of surface excitions can be a much more general phenomenon than was previously thought based on extant spectroscopic measurements.

Joly, Alan G.; Beck, Kenneth M.; Henyk, Matthias; Hess, Wayne P.; Sushko, Petr V.; Shluger, Alexander L.

2003-10-10

308

Dose spectra from energetic particles and neutrons  

NASA Astrophysics Data System (ADS)

spectra from energetic particles and neutrons (DoSEN) are an early-stage space technology research project that combines two advanced complementary radiation detection concepts with fundamental advantages over traditional dosimetry. DoSEN measures not only the energy but also the charge distribution (including neutrons) of energetic particles that affect human (and robotic) health in a way not presently possible with current dosimeters. For heavy ions and protons, DoSEN provides a direct measurement of the lineal energy transfer (LET) spectra behind shielding material. For LET measurements, DoSEN contains stacks of thin-thick Si detectors similar in design to those used for the Cosmic Ray Telescope for the Effects of Radiation. With LET spectra, we can now directly break down the observed spectrum of radiation into its constituent heavy-ion components and through biologically based quality factors that provide not only doses and dose rates but also dose equivalents, associated rates, and even organ doses. DoSEN also measures neutrons from 10 to 100 MeV, which requires enough sensitive mass to fully absorb recoil particles that the neutrons produce. DoSEN develops the new concept of combining these independent measurements and using the coincidence of LET measurements and neutron detection to significantly reduce backgrounds in each measurement. The background suppression through the use of coincidence allows for significant reductions in size, mass, and power needed to provide measurements of dose, neutron dose, dose equivalents, LET spectra, and organ doses. Thus, we introduce the DoSEN concept: a promising low-mass instrument that detects the full spectrum of energetic particles, heavy ions, and neutrons to determine biological impact of radiation in space.

Schwadron, Nathan; Bancroft, Chris; Bloser, Peter; Legere, Jason; Ryan, James; Smith, Sonya; Spence, Harlan; Mazur, Joe; Zeitlin, Cary

2013-10-01

309

Deconvolution of Alpha Spectra From Hot Particles  

Microsoft Academic Search

A computer code known as AASIFIT is developed to unfold complex alpha spectra. Peak shapes used in the fitting are obtained\\u000a from the simulations. In addition to activities of the nuclides present in the sample, the code can provide source characterization.\\u000a AASIFIT is applied for a nuclear bomb particle collected in Thule, Greenland. It is shown that direct alpha spectrometry

Roy Pöllänen; Tero Karhunen; Teemu Siiskonen; Harri Toivonen; Andreas Pelikan

310

Random Matrix Spectra as a Time Series  

E-print Network

Spectra of ordered eigenvalues of finite Random Matrices are interpreted as a time series. Dataadaptive techniques from signal analysis are applied to decompose the spectrum in clearly differentiated trend and fluctuation modes, avoiding possible artifacts introduced by standard unfolding techniques. The fluctuation modes are scale invariant and follow different power laws for Poisson and Gaussian ensembles, which already during the unfolding allows to distinguish the two cases.

Ruben Fossion; Gamaliel Torres Vargas; Juan Carlos López Vieyra

2013-11-21

311

Detection of climate forcing using emission spectra  

NASA Technical Reports Server (NTRS)

We discuss the use of thermal emission spectra recorded by satellites to construct climate indices that can detect the evolution of a specific climate forcing in a time series. The two important issues are selectivity against climate forcings other than one that is sought, and sensitivity to the required forcing. We show that indices with selectivity can be found, and that their sensitivity can be high.

Goody, Richard; Haskins, Robert; Abdou, Wedad; Chen, Luke

1995-01-01

312

Dynamical analysis of highly excited molecular spectra  

SciTech Connect

The goal of this program is new methods for analysis of spectra and dynamics of highly excited vibrational states of molecules. In these systems, strong mode coupling and anharmonicity give rise to complicated classical dynamics, and make the simple normal modes analysis unsatisfactory. New methods of spectral analysis, pattern recognition, and assignment are sought using techniques of nonlinear dynamics including bifurcation theory, phase space classification, and quantization of phase space structures. The emphasis is chaotic systems and systems with many degrees of freedom.

Kellman, M.E. [Univ. of Oregon, Eugene (United States)

1993-12-01

313

Island shadows in wave directional spectra  

NASA Astrophysics Data System (ADS)

Shadows of individual islands are observed in directional spectra sampled with a high resolution linear array at Torrey Pines Beach, California. A detailed investigation of the spectra indicates that the Channel Islands restrict the wave energy density to certain narrow directional sectors. A deep spectral trough, associated with San Clemente Island, is a predominant feature in the well resolved spectra (wave frequencies ˜0.06-0.15 Hz). Negligible values of energy density in the center of this directional `gap' were consistently observed in the range 0.082-0.114 Hz. Measurable but low gap energy density values are seen in the high and low frequency regimes. Generation of high frequency waves (f?0.13 Hz) by local winds generally smears the island windowing effects and even creates a spectral peak in a directional sector which is blocked from deep ocean exposure. Several estimation techniques are used in the directional spectrum analysis. These include the Maximum Likelihood Method (MLM) and two methods developed in this work. The two new techniques show significant improvement over the MLM in the definition of gaps in the spectrum. Although none of these methods is considered an `Optimal' estimator for general use, each displays some superior merit in particular directional spectrum estimation problems.

Pawka, S. S.

1983-03-01

314

Infrared Transmission Spectra for Extrasolar Giant Planets  

E-print Network

Among the hot Jupiters that transit their parent stars known to date, the two best candidates to be observed with transmission spectroscopy in the mid-infrared (MIR) are HD189733b and HD209458b, due to their combined characteristics of planetary density, orbital parameters and parent star distance and brightness. Here we simulate transmission spectra of these two planets during their primary eclipse in the MIR, and we present sensitivity studies of the spectra to the changes of atmospheric thermal properties, molecular abundances and C/O ratios. Our model predicts that the dominant species absorbing in the MIR on hot Jupiters are water vapor and carbon monoxide, and their relative abundances are determined by the C/O ratio. Since the temperature profile plays a secondary role in the transmission spectra of hot Jupiters compared to molecular abundances, future primary eclipse observations in the MIR of those objects might give an insight on EGP atmospheric chemistry. We find here that the absorption features caused by water vapor and carbon monoxide in a cloud-free atmosphere, are deep enough to be observable by the present and future generation of space-based observatories, such as Spitzer Space Telescope and James Webb Space Telescope. We discuss our results in light of the capabilities of these telescopes.

G. Tinetti; M. C. Liang; A. Vidal-Madjar; D. Ehrenreich; A. Lecavelier des Etangs; Y. Yung

2006-11-06

315

The Transit Spectra of Earth and Jupiter  

E-print Network

In recent years, a number of observations have been made of the transits of 'Hot Jupiters', such as HD 189733b, which have been modelled to derive atmospheric structure and composition. As measurement techniques improve, the transit spectra of 'Super-Earths' such as GJ 1214b are becoming better constrained, allowing model atmospheres to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets such as the Earth or cold planets like Jupiter, this may become practical in the coming decades and if so, it is of interest to determine what we might infer from such measurements. Here we have constructed atmospheric models of the Solar System planets from 0.4 - 15.5 microns that are consistent with ground-based and satellite observations and from these calculate the primary transit and secondary eclipse spectra (with respect to the Sun and typical M-dwarfs) that would be observed by a 'remote observer', many light years away. From these spectra we test ...

Irwin, Patrick G J; Bowles, Neil E; Fletcher, Leigh N; Aigrain, Suzanne; Lee, Jae-Min

2014-01-01

316

VARIABILITY IN OPTICAL SPECTRA OF {epsilon} ORIONIS  

SciTech Connect

We present the results of a time series analysis of 130 echelle spectra of {epsilon} Ori (B0 Ia), acquired over seven observing seasons between 1998 and 2006 at Ritter Observatory. The equivalent widths of H{alpha} (net) and He I {lambda}5876 were measured and radial velocities were obtained from the central absorption of He I {lambda}5876. Temporal variance spectra (TVS) revealed significant wind variability in both H{alpha} and He I {lambda}5876. The He I TVS have a double-peaked profile consistent with radial velocity oscillations. A periodicity search was carried out on the equivalent width and radial velocity data, as well as on wavelength-binned spectra. This analysis has revealed several periods in the variability with timescales of two to seven days. Many of these periods exhibit sinusoidal modulation in the associated phase diagrams. Several of these periods were present in both H{alpha} and He I, indicating a possible connection between the wind and the photosphere. Due to the harmonic nature of these periods, stellar pulsations may be the origin of some of the observed variability. Periods on the order of the rotational period were also detected in the He I line in the 1998-1999 season and in both lines during the 2004-2005 season. These periods may indicate rotational modulation due to structure in the wind.

Thompson, Gregory B. [Department of Physics, Adrian College, Adrian, MI 49221 (United States); Morrison, Nancy D., E-mail: gthompson@adrian.edu, E-mail: nmorris@utnet.utoledo.edu [Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft, Toledo, OH 43606 (United States)

2013-04-15

317

Infrared spectra of substituted polycylic aromatic hydrocarbons  

NASA Technical Reports Server (NTRS)

Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of 1-methylanthracene, 9-methylanthracene, 9-cyanoanthracene, 2-aminoanthracene, acridine, and their positive ions. The theoretical data are compared with matrix-isolation spectra for these species also reported in this work. The theoretical and experimental frequencies and relative intensities for the neutral species are in generally good agreement, whereas the positive ion spectra are only in qualitative agreement. Relative to anthracene, we find that substitution of a methyl or CN for a hydrogen does not significantly affect the spectrum other than to add the characteristic methyl C-H and C triple bond N stretches near 2900 and 2200 cm-1, respectively. However, addition of NH2 dramatically affects the spectrum of the neutral. Not only are the NH2 modes themselves strong, but this electron-withdrawing group induces sufficient partial charge on the ring to give the neutral molecule spectra characteristics of the anthracene cation. The sum of the absolute intensities is about four times larger for 2-aminoanthracene than those for 9-cyanoanthracene. Substituting nitrogen in the ring at the nine position (acridine) does not greatly alter the spectrum compared with anthracene.

Langhoff, S. R.; Bauschlicher, C. W. Jr; Hudgins, D. M.; Sandford, S. A.; Allamandola, L. J.

1998-01-01

318

DYNAMICAL ANALYSIS OF HIGHLY EXCITED MOLECULAR SPECTRA  

SciTech Connect

Spectra and internal dynamics of highly excited molecules are essential to understanding processes of fundamental importance for combustion, including intramolecular energy transfer and isomerization reactions. The goal of our program is to develop new theoretical tools to unravel information about intramolecular dynamics encoded in highly excited experimental spectra. We want to understand the formations of ''new vibrational modes'' when the ordinary normal modes picture breaks down in highly excited vibrations. We use bifurcation analysis of semiclassical versions of the effective Hamiltonians used by spectroscopists to fit complex experimental spectra. Specific molecular systems are of interest for their relevance to combustion and the availability of high-quality experimental data. Because of its immense importance in combustion, the isomerizing acetylene/vinylidene system has been the object of long-standing experimental and theoretical research. We have made significant progress in systematically understanding the bending dynamics of the acetylene system. We have begun to make progress on extending our methodology to the full bend-stretch vibrational degrees of freedom, including dynamics with multiple wells and above barrier motion, and time-dependent dynamics. For this, development of our previous methods using spectroscopic fitting Hamiltonians is needed, for example, for systems with multiple barriers.

Michael E. Kellman

2005-06-17

319

Low Temperature Reflectance Spectra of Titan Tholins  

NASA Technical Reports Server (NTRS)

Compositional interpretation of remotely obtained reflectance spectra of outer solar system surfaces is achieved by a variety of methods. These include matching spectral curves, matching spectral features, quantitative spectral interpretation, and theoretical modeling of spectra. All of these approaches rely upon laboratory measurements of one kind or another. The bulk of these laboratory measurements are obtained with the sample of interest at ambient temperatures and pressures. However, surface temperatures of planets, satellites, and asteroids in the outer solar system are significantly cooler than ambient laboratory conditions on Earth. The infrared spectra of many materials change as a function of temperature. As has been recently demonstrated it is important to assess what effects colder temperatures have on spectral properties and hence, compositional interpretations. Titan tholin is a solid residue created by energetic processing of H-, C-, and N-bearing gases. Such residues can also be created by energetic processing if the gases are condensed into ices. Titan tholin has been suggested as a coloring agent for several surfaces in the outer solar system. Here we report laboratory measurements of Titan tholin at a temperature of 100 K and compare these to measurements of the same sample near room temperature. At low temperature the absorption features beyond 1 micrometer narrow slightly. At wavelengths greater than approx. 0.8 micrometer the overall reflectance of the sample decreases slightly making the sample less red at low temperatures. We will discuss the implications of the laboratory measurements for interpretation of cold outer solar system surfaces.

Roush, T. L.; Dalton, J. B.; Fonda, Mark (Technical Monitor)

2001-01-01

320

The ultraviolet spectra of the Jovian aurora  

SciTech Connect

The ultraviolet spectra of molecular hydrogen H{sub 2} due to electron impact excitation are calculated and compared with the high-resolution (0.56 A) spectra of the Jovian aurora obtained with the {ital Hubble} {ital Space} {ital Telescope} Goddard High-Resolution Spectrograph. All the observed features are reproduced by electron impact excitation emissions of H{sub 2}, and the predicted intensities agree well with the observed intensities. Accurate molecular parameters are used, and effects of secondary electrons are included. The auroral emissions are reproduced by energetic electron impact excitation of H{sub 2} with a temperature of 400{endash}600 K. Large temperature gradients occur with respect to altitude within the auroral emission regions. The auroral spectra contain a cascade contribution to the Lyman band emission from high-lying {ital E} and {ital F} states that are populated by the low-energy secondary electrons produced as the energetic auroral electrons slow down. {copyright} {ital 1996 The American Astronomical Society.}

Liu, W.; Dalgarno, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

1996-08-01

321

Analysis of positron lifetime spectra in polymers  

NASA Technical Reports Server (NTRS)

A new procedure for analyzing multicomponent positron lifetime spectra in polymers was developed. It requires initial estimates of the lifetimes and the intensities of various components, which are readily obtainable by a standard spectrum stripping process. These initial estimates, after convolution with the timing system resolution function, are then used as the inputs for a nonlinear least squares analysis to compute the estimates that conform to a global error minimization criterion. The convolution integral uses the full experimental resolution function, in contrast to the previous studies where analytical approximations of it were utilized. These concepts were incorporated into a generalized Computer Program for Analyzing Positron Lifetime Spectra (PAPLS) in polymers. Its validity was tested using several artificially generated data sets. These data sets were also analyzed using the widely used POSITRONFIT program. In almost all cases, the PAPLS program gives closer fit to the input values. The new procedure was applied to the analysis of several lifetime spectra measured in metal ion containing Epon-828 samples. The results are described.

Singh, Jag J.; Mall, Gerald H.; Sprinkle, Danny R.

1988-01-01

322

IRAS Low Resolution Spectra of Asteroids  

NASA Technical Reports Server (NTRS)

Optical/near-infrared studies of asteroids are based on reflected sunlight and surface albedo variations create broad spectral features, suggestive of families of materials. There is a significant literature on these features, but there is very little work in the thermal infrared that directly probes the materials emitting on the surfaces of asteroids. We have searched for and extracted 534 thermal spectra of 245 asteroids from the original Dutch (Groningen) archive of spectra observed by the IRAS Low Resolution Spectrometer (LRS). We find that, in general, the observed shapes of the spectral continua are inconsistent with that predicted by the standard thermal model used by IRAS. Thermal models such as proposed by Harris (1998) and Harris et al.(1998) for the near-earth asteroids with the "beaming parameter" in the range of 1.0 to 1.2 best represent the observed spectral shapes. This implies that the IRAS Minor Planet Survey (IMPS, Tedesco, 1992) and the Supplementary IMPS (SIMPS, Tedesco, et al., 2002) derived asteroid diameters are systematically underestimated, and the albedos are overestimated. We have tentatively identified several spectral features that appear to be diagnostic of at least families of materials. The variation of spectral features with taxonomic class hints that thermal infrared spectra can be a valuable tool for taxonomic classification of asteroids.

Cohen, Martin; Walker, Russell G.

2002-01-01

323

From plasmon spectra of metallic to vibron spectra of dielectric nanoparticles.  

PubMed

Light interacts surprisingly differently with small particles than with bulk or gas phase materials. This can cause rare phenomena such as the occurence of a "blue moon". Spectroscopic particle phenomena of similar physical origin have also spawned countless applications ranging from remote sensing to medicine. Despite the broad interest in particle spectra, their interpretation still poses many challenges. In this Account, we discuss the challenges associated with the analysis of infrared, or vibron, extinction spectra of small dielectric particles. The comparison with the more widely studied plasmon spectra of metallic nano-particles reveals many common features. The shape, size, and architecture of particles influence the band profiles in vibron and plasmon spectra in similar ways. However, the molecular structure of dielectric particles produces infrared spectral features that are more diverse and detailed or even unique to vibron spectra. More complexity means higher information content, but that also makes the spectra more difficult to interpret. Conventional models such as classical electromagnetic theory with a continuum description of the wavelength-dependent optical constants are often no longer applicable to these spectra. In cases where accurate optical constants are not available and for ultrafine particles, where the molecular structure and quantum effects become essential, researchers must resort to molecular models for light-particle interaction that do not require the prior knowledge of optical constants. In this Account, we illustrate how vibrational exciton approaches combined with molecular dynamics simulations and solid-state density functional calculations provide a viable solution to these challenges. Molecular models reveal two important characteristics of vibron spectra of small molecularly structured particles. The band profiles in vibron spectra are largely determined by transition dipole coupling between the molecules in a particle. Below a specific particle size limit, conventional models fail. Molecular models explain many other phenomena in particle spectra, such as size, shape, and mixing effects, providing the foundation for a better understanding of the interaction of solar radiation with aerosols and clouds and for the design of dielectric nanomaterials. PMID:22738352

Preston, Thomas C; Signorell, Ruth

2012-09-18

324

Optimal construction of theoretical spectra for MS/MS spectra identification  

SciTech Connect

We derive the optimal number of peaks (defined as the minimum number that provides the required efficiency of spectra identification) in the theoretical spectra as a function of: (i) the experimental accuracy, , of the measured ratio m/z; (ii) experimental spectrum density; (iii) size of the database; (iv) number of peaks in the theoretical spectra; and (v) types of ions that the peaks represent. We show that if theoretical spectra are constructed including b and y ions alone, then for =0.5, which is typical for high throughput data, peptide chains of 8 amino acids or longer can be identified based on the positions of peaks alone, at a rate of false identification below 1%. To discriminate between shorter peptides, additional (e.g., intensity-inferred) information is necessary. We derive the dependence of the probability of false identification on the number of peaks in the theoretical spectra and on the types of ions that the peaks represent. Our results suggest that the class of mass spectrum identification problems for which more elaborate development of fragmentation rules (such as intensity model, etc.) is required, can be reduced to the problems that involve homologous peptides.

Fridman, Tamah [ORNL; Protopopescu, Vladimir A [ORNL; Hurst, Gregory {Greg} B [ORNL; Borziak, Andrei [ORNL; Gorin, Andrey A [ORNL

2005-01-01

325

Electronic spectra of radical cations and their correlation with photoelectron spectra—V. Pyrenes  

NASA Astrophysics Data System (ADS)

Optical absorption spectra of the radical cations of a variety of pyrenes, viz. pyrene, 1.2-benzopyrene, 3.4-benzopyrene, 1.2,3.4-dibenzopyrene, 1.2,4.5-dibenzopyrene, 3.4,9.10-dibenzopyrene, 1.2,4.5,8.9-tribenzopyrene, 1.2,3.4,9.10-tribenzopyrene, 1.2,3.4,6.7,9.10-tetrabenzopyrene, 3.4,9.10-dibenzonaphtho-(2'.3':1.2)pyrene and pyreno-(1'.2':1.2)pyrene, are reported. The results are analysed in the light of open-shell SCF?MO?LCI calculations. For the I-type transitions in radical cations, the correspondence between the optical and the photoelectron spectra is closely examined and it is found that, barring small matrix shifts, the overall agreement between the two types of spectra is excellent. Correlation diagrams for the calculated electronic transitions of radical cations of pyrenes are also sketched which clearly reveal a systematic trend in the movement of different types of transitions from one system to another. We have further established an interesting relation between the first vertical ionization potentials (IP 1's) of pyrenes and the energies of the so-called A type optical bands ( EA's) in their cation spectra, viz. IP 1 = (5.59±0.13) + (0.65±0.06) EA. From this expression, the first IP's of pyrenes can be reasonably estimated from the knowledge of the optical spectra of their cations.

Khan, Zahid H.

1989-01-01

326

Identifying Minerals from Their Infra-red Spectra.  

ERIC Educational Resources Information Center

Describes a British secondary school's use of a spectrometer to identify minerals. Discusses the origins of mineral spectra, the preparation of the specimen, the actual spectroscopic scanning, and the interpretation of the spectra. (TW)

Paterson, W. G.

1986-01-01

327

ABSENCE OF ABSOLUTELY CONTINUOUS SPECTRA FOR MULTIDIMENSIONAL SCHRODINGER OPERATORS WITH  

E-print Network

ABSENCE OF ABSOLUTELY CONTINUOUS SPECTRA FOR MULTIDIMENSIONAL SCHRODINGER OPERATORS WITH HIGH continuous spectra for multidimensional Schrodinger operators with high barriers. The result is formulated typical situations in which Schrodinger operators have singular spectrum, namely when their potential has

Stollmann, P.

328

Infrared absorption spectra, radiative efficiencies, and global warming potentials  

E-print Network

Infrared absorption spectra, radiative efficiencies, and global warming potentials absorption spectra, radiative efficiencies, and global warming potentials of perfluorocarbons: Comparison. (1995) and combined with atmospheric lifetimes from the literature to determine global warming

Wirosoetisno, Djoko

329

Atomic and Molecular Aspects of Astronomical Spectra  

NASA Astrophysics Data System (ADS)

In the first section we present the atomic part where a C2+ atomic target was prepared and used to generate theoretical data to investigate recombination lines arising from electron-ion collisions in thin plasma. R-matrix method was used to describe the C2+ plus electron system. Theoretical data concerning bound and autoionizing states were generated in the intermediate-coupling approximation. The data were used to generate dielectronic recombination data for C+ which include transition lines, oscillator strengths, radiative transition probabilities, emissivities and dielectronic recombination coefficients. The data were cast in a line list containing 6187 optically-allowed transitions which include many C II lines observed in astronomical spectra. This line list was used to analyze the spectra from a number of astronomical objects, mainly planetary nebulae, and identify their electron temperature. The electron temperature investigation was also extended to include free electron energy analysis to investigate the long-standing problem of discrepancy between the results of recombination and forbidden lines analysis and its possible connection to the electron distribution. In the second section we present the results of our molecular investigation; the generation of a comprehensive, calculated line list of frequencies and transition probabilities for H2D+. The line list contains over 22 million rotational-vibrational transitions occurring between more than 33 thousand energy levels and covers frequencies up to 18500 cm-1. About 15% of these levels are fully assigned with approximate rotational and vibrational quantum numbers. A temperature-dependent partition function and cooling function are presented. Temperature-dependent synthetic spectra for the temperatures T=100, 500, 1000 and 2000 K in the frequency range 0-10000 cm-1 were also generated and presented graphically.

Sochi, Taha

2012-11-01

330

Effect of Temperature on Jet Velocity Spectra  

NASA Technical Reports Server (NTRS)

Statistical jet noise prediction codes that accurately predict spectral directivity for both cold and hot jets are highly sought both in industry and academia. Their formulation, whether based upon manipulations of the Navier-Stokes equations or upon heuristic arguments, require substantial experimental observation of jet turbulence statistics. Unfortunately, the statistics of most interest involve the space-time correlation of flow quantities, especially velocity. Until the last 10 years, all turbulence statistics were made with single-point probes, such as hotwires or laser Doppler anemometry. Particle image velocimetry (PIV) brought many new insights with its ability to measure velocity fields over large regions of jets simultaneously; however, it could not measure velocity at rates higher than a few fields per second, making it unsuitable for obtaining temporal spectra and correlations. The development of time-resolved PIV, herein called TR-PIV, has removed this limitation, enabling measurement of velocity fields at high resolution in both space and time. In this paper, ground-breaking results from the application of TR-PIV to single-flow hot jets are used to explore the impact of heat on turbulent statistics of interest to jet noise models. First, a brief summary of validation studies is reported, undertaken to show that the new technique produces the same trusted results as hotwire at cold, low-speed jets. Second, velocity spectra from cold and hot jets are compared to see the effect of heat on the spectra. It is seen that heated jets possess 10 percent more turbulence intensity compared to the unheated jets with the same velocity. The spectral shapes, when normalized using Strouhal scaling, are insensitive to temperature if the stream-wise location is normalized relative to the potential core length. Similarly, second order velocity correlations, of interest in modeling of jet noise sources, are also insensitive to temperature as well.

Bridges, James E.; Wernet, Mark P.

2007-01-01

331

Chemically-assigned classification of aerosol mass spectra  

Microsoft Academic Search

An Algorithm for Discriminant Analysis of Mass Spectra—ADAMS—was created that classified aerosol mass spectra into dominant chemically-assigned classes, and grouped rare\\u000a cases in an outlier class. ADAMS was trained with ambient particulate matter (PM) mass spectra, and then validated through\\u000a classification tests on known spectra with random noise added, various standard chemicals, and salt-spiked polystyrene latex\\u000a microspheres. The classification results

Phillip V. Tan; Oscar Malpica; Greg J. Evans; Sandy Owega; Michael S. Fila

2002-01-01

332

SAR-ocean wave inversion using image cross spectra  

Microsoft Academic Search

Image cross-spectra obtained by combining pairs of single look SAR images are utilized in an inversion scheme for extracting the underlying ocean wave spectrum. The reasons for proposing the use of image cross-spectra instead of standard multilook spectra are twofold. First, the image cross-spectra are shown to significantly reduce the speckle noise level while preserving the spectral shape. Second, the

Geir Engen; Harald Johnsen

1995-01-01

333

Proposed reference irradiance spectra for solar energy systems testing  

Microsoft Academic Search

In 1982, the American Society for Testing and Materials (ASTM) adopted consensus standard solar terrestrial spectra (ASTM E891-82, E892-82) to provide standard spectra for photovoltaic (PV) performance applications. These spectra have been also used for other applications such as solar energy systems, fenestration, and materials degradation. These reference spectra were recomputed and the standards revised in 1987. The International Standards

C. A. Gueymard; D. Myers; K. Emery

2002-01-01

334

Multifractal spectra in homogeneous shear flow  

NASA Technical Reports Server (NTRS)

Employing numerical simulations of 3-D homogeneous shear flow, the associated multifractal spectra of the energy dissipation, scalar dissipation and vorticity fields were calculated. The results for (128) cubed simulations of this flow, and those obtained in recent experiments that analyzed 1- and 2-D intersections of atmospheric and laboratory flows, are in some agreement. A two-scale Cantor set model of the energy cascade process which describes the experimental results from 1-D intersections quite well, describes the 3-D results only marginally.

Deane, A. E.; Keefe, L. R.

1988-01-01

335

Covariance analysis of gamma ray spectra  

SciTech Connect

The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

Trainham, R.; Tinsley, J. [Special Technologies Laboratory of National Security Technologies, LLC, 5520 Ekwill Street, Santa Barbara, California 93111 (United States)

2013-01-15

336

Covariance Analysis of Gamma Ray Spectra  

SciTech Connect

The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

Trainham, R.; Tinsley, J.

2013-01-01

337

SIMULATION OF PARTICLE SPECTRA AT RHIC.  

SciTech Connect

A purely hadronic simulation is performed of the recently reported data from PHOBOS at energies of {radical}s = 56, 130 GeV using the relativistic heavy ion cascade LUCIFER which had previously given a good description of the NA49 inclusive spectra at {radical}s = 17.2 GeV/A. The results compare well with these early measurements at RHIC and indeed successfully predict the increase in multiplicity now seen by PHOBOS and the other RHIC detectors at the nominal maximum energy of {radical}s = 200 GeV/A, suggesting that evidence for quark-gluon matter remains elusive.

KAHANA,D.E.; KAHANA,S.H.

2001-09-04

338

Hölder exponent spectra for human gait  

NASA Astrophysics Data System (ADS)

The stride interval time series in normal human gait is not strictly constant, but fluctuates from step to step in a complex manner. More precisely, it has been shown that the control process for human gait is a fractal random phenomenon, that is, one with a long-term memory. Herein we study the Hölder exponent spectra for the slow, normal and fast gaits of 10 young healthy men in both free and metronomically triggered conditions and establish that the stride interval time series is more complex than a monofractal phenomenon. A slightly multifractal and non-stationary time series under the three different gait conditions emerges.

Scafetta, N.; Griffin, L.; West, B. J.

2003-10-01

339

Quantitative Analyses of Planetary Reflectance Spectra  

NASA Technical Reports Server (NTRS)

The development of a set of quantitative models to analyze planetary reflectance spectra as a function of microscopic and macroscopic mineral mixtures, particle size, and illumination geometry is considered. The approach has been to simplify more sophisticated algorithms to include the smallest number of parameters possible, consistent with being able to use them to produce useful results. This means that they should be able to model the data to within the accuracy obtainable by laboratory, telescopic, and space instrumentation (roughly 1%). The algorithms are ideally given in terms of parameters that are directly measureable (such as spectral reflectance or particle size).

Johnson, P. E.

1985-01-01

340

Systematics of Identified Hadron Spectra at PHENIX  

E-print Network

Mid-rapidity transverse momentum distributions for $\\pi^\\pm$, $K^\\pm$, p and $\\pbar$ are measured by the PHENIX experiment at RHIC in Au+Au, d+Au and p+p collisions at \\ssnn=200GeV up to ~2--4GeV. Also particle ratios of $\\pi^{-}/\\pi^{+}$, $K^{-}/K^{+}$, $\\pbar/p$, $p/\\pi$ and $\\pbar/\\pi$ are measured, as well as the nuclear modification factor, all as a function of \\pt and in every of the above collision systems. Finally, the measured p+p and Au+Au spectra are compared to the Buda-Lund hydro model.

M. Csanad

2005-05-01

341

Beamstrahlung spectra in next generation linear colliders  

SciTech Connect

For the next generation of linear colliders, the energy loss due to beamstrahlung during the collision of the e{sup +}e{sup {minus}} beams is expected to substantially influence the effective center-of-mass energy distribution of the colliding particles. In this paper, we first derive analytical formulae for the electron and photon energy spectra under multiple beamstrahlung processes, and for the e{sup +}e{sup {minus}} and {gamma}{gamma} differential luminosities. We then apply our formulation to various classes of 500 GeV e{sup +}e{sup {minus}} linear collider designs currently under study.

Barklow, T.; Chen, P. (Stanford Linear Accelerator Center, Menlo Park, CA (United States)); Kozanecki, W. (DAPNIA-SPP, CEN-Saclay (France))

1992-04-01

342

Techniques for classifying acoustic resonant spectra  

SciTech Connect

A second-generation nondestructive evaluation (NDE) system that discriminates between different types of chemical munitions is under development. The NDE system extracts features from the acoustic spectra of known munitions, builds templates from these features, and performs classification by comparing features extracted from an unknown munition to a template library. Improvements over first-generation feature extraction template construction and classification algorithms are reported. Results are presented on the performance of the system and a large data set collected from surrogate-filled munitions.

Roberts, R.S.; Lewis, P.S.; Chen, J.T.; Vela, O.A.

1995-12-31

343

IUE spectra of flares on AU Mic  

NASA Technical Reports Server (NTRS)

Some IUE spectra were obtained in August 1980 through a substantial part of the optical cycle of the BY Draconis-type, spotted M dwarf star, AU Mic. No modulation of the ultraviolet emission line fluxes in antiphase with the optical curve is detected. Simultaneous optical photometry of AU Mic shows remarkably poor correlation of optical flare strength and ultraviolet emission-line enhancements. The flares detected on AU Mic show considerable variety in the degree of enhancement in the various emission lines and optical continuum.

Butler, C. J.; ion lines and optical continuum.

1986-01-01

344

GENERAL RELATIVISTIC EFFECTS ON NONLINEAR POWER SPECTRA  

SciTech Connect

The nonlinear nature of Einstein's equation introduces genuine relativistic higher order corrections to the usual Newtonian fluid equations describing the evolution of cosmological perturbations. We study the effect of such novel nonlinearities on the next-to-leading order matter and velocity power spectra for the case of a pressureless, irrotational fluid in a flat Friedmann background. We find that pure general relativistic corrections are negligibly small over all scales. Our result guarantees that, in the current paradigm of standard cosmology, one can safely use Newtonian cosmology even in nonlinear regimes.

Jeong, Donghui [California Institute of Technology, Pasadena, CA 91125-1700 (United States); Gong, Jinn-Ouk [Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, 2333 CA Leiden (Netherlands); Noh, Hyerim [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Hwang, Jai-chan, E-mail: djeong@tapir.caltech.edu, E-mail: jgong@lorentz.leidenuniv.nl, E-mail: hr@kasi.re.kr, E-mail: jchan@knu.ac.kr [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701 (Korea, Republic of)

2011-01-20

345

Glow Sticks: Spectra and Color Mixing  

NASA Astrophysics Data System (ADS)

Glow sticks are a popular Halloween staple familiar to most of our students. The production of light via a chemical reaction is called "chemiluminescence," and glow sticks are often used as demonstrations and experiments in the chemistry classroom to study reaction rates as a function of temperature.1-3 A black light can be used to illuminate glow sticks that have not been cracked or those that are "dead" in order to demonstrate fluorescence in liquid chemicals.4 In this article, we present the use of glow sticks as an inexpensive demonstration of spectra and color addition.

Birriel, Jennifer; Birriel, Ignacio

2014-10-01

346

Neutrino spectra evolution during protoneutron star deleptonization  

NASA Astrophysics Data System (ADS)

The neutrino-driven wind, which occurs after the onset of a core-collapse supernova explosion, has long been considered as the possible site for the synthesis of heavy r-process elements in the Universe. Only recently, it has been possible to simulate supernova explosions up to ˜10seconds, based on three-flavor Boltzmann neutrino transport. These simulations show that the neutrino luminosities and spectra of all flavors are very similar and their difference even decreases during the deleptonization of the proto-neutron star. As a consequence, the ejecta are always proton rich which rules out the possible production of heavy r-process elements (Z>56). We perform a detailed analysis of the different weak processes that determine the neutrino spectra. Nonelectron flavor (anti)neutrinos are produced and interact only via neutral-current processes, while electron (anti)neutrinos have additional contributions from charge-current processes. The latter are dominated by ?e-absorption on neutrons and ?¯e-absorption on protons. At early times, charge-current processes are responsible for spectral differences between ?e, ?¯e and ??/?. However, as the region of neutrino decoupling moves to higher densities during deleptonization, charge-current reactions are suppressed by final state Pauli blocking. ?¯e absorption on protons is suppressed due to the continuously increasing chemical potential of the neutrons. ?e absorption on neutrons is blocked by the increasing degeneracy of the electrons. These effects result in negligible contributions from charge-current reactions on time scales on the order of tens of seconds, depending on the progenitor star. Hence, the neutrino spectra are mainly determined from neutral-current processes which do not distinguish between the different flavors and result in the convergence of the spectra. These findings are independent of the charge-current reaction rates used. It rules out the possibility of neutron-rich ejecta at late times and the production of heavy r-process elements from nonrotating and not magnetized proto-neutron stars.

Fischer, T.; Martínez-Pinedo, G.; Hempel, M.; Liebendörfer, M.

2012-04-01

347

A New approach to inclusive decay spectra.  

E-print Network

of the Standard Model, we must have a quantitative understanding of the spectra. Most of the rate of these decays is associated with jet–like kinematics, where the invariant mass of the hadronic system is small. It is well known that this important region... strategy has been to parametrize the spectrum based on available data, rather than to compute it. On the other hand, since total inclusive rates, as well as their first few moments, are theoretically described by the OPE [4,5] — and in particular, if O(?2/m...

Gardi, Einan; Andersen, Jeppe R

348

THE SPECTRA OF THE DOUBLY AND TRIPLY IONIZED RARE EARTHS  

Microsoft Academic Search

The present status of the knowledge of the structure of the spectra of ; the doubly and triply ionized spectra of the rare earths is derived partly from ; experimental data of the emission spectra of the free ions which provide the ; energy level scheme in great detail but are difficuit and laborious to analyze. ; For the lower

G. H. Dieke; H. M. Crosswhite

1963-01-01

349

Low energy particle composition. [energy spectra, particle emission - solar flares  

NASA Technical Reports Server (NTRS)

The energy spectra and composition of the steady or 'quiet-time' particle flux, whose origin is unknown was studied. Particles and photons which are associated with solar flares or active regions on the sun were also studied. Various detection techniques used to measure the composition and energy spectra of low energy particles are discussed. Graphs of elemental abundance and energy spectra are given.

Gloeckler, G.

1975-01-01

350

IRAS catalogues and atlases - Atlas of low-resolution spectra  

Microsoft Academic Search

The authors present plots of all 5425 spectra in the IRAS catalogue of low-resolution spectra. The LRS catalogue contains the average spectra of most IRAS point sources with 12 mum flux densities above 10 Jy. More than 95 percent of the LRS sources are stars, most of them with circumstellar envelopes.

F. M. Olnon; E. Raimond; G. Neugebauer; R. J. van Duinen; H. J. Habing; H. H. Aumann; D. A. Beintema; N. Boggess; J. Borgman; P. E. Clegg; F. C. Gillett; M. G. Hauser; J. R. Houck; R. E. Jennings; T. de Jong; F. J. Low; P. L. Marsden; S. R. Pottasch; B. T. Soifer; R. G. Walker; J. P. Emerson; M. Rowan-Robinson; P. R. Wesselius; B. Baud; C. A. Beichman; T. N. Gautier; S. Harris; G. K. Miley; E. Young

1986-01-01

351

Fast approximate Duplicate Detection for 2D-NMR Spectra  

E-print Network

Fast approximate Duplicate Detection for 2D-NMR Spectra Bj¨orn Egert1 , Steffen Neumann1. In contrast to 1D-NMR spectra, 2D-NMR spectra correlate the chemical shifts of 1 H and 13 C simultaneously a definition of duplicates with the desired robustness properties mandatory for 2D-NMR experiments. A major

Hinneburg, Alexander

352

Characterizing solar proton energy spectra for radiation effects applications  

Microsoft Academic Search

The Weibull distribution for smallest values is shown to be a useful description for solar proton event energy spectra. One advantage is its compact analytic expression, which allows easy conversion between differential and integral spectra. Another is its versatility, which is necessary for describing the highly variable spectra of concern. Furthermore, the Weibull distribution appears to be appropriate for use

M. A. Xapsos; J. L. Barth; E. G. Stassinopoulos; S. R. Messenger; R. J. Walters; G. P. Summers; E. A. Burke

2000-01-01

353

Ultraviolet Stellar and Cluster Spectra Compared to Theoretical Templates  

Microsoft Academic Search

As part of NASA and Hubble Treasury programs, we are generating theoretical spectra for globular clusters and galaxies from first principles. To check their validity, we are assessing how well they match high-resolution echelle spectra of the Sun and nearby stars. Once agreement is reasonable, spectra at fixed metallicity and light-element enhancement are coadded with weights representing the relative contribution

R. C. Peterson

2009-01-01

354

Extracting Salient Information from Mass Spectra of Prostate Cancer  

Microsoft Academic Search

This paper presents an application of multilevel wavelet analysis for high dimensional mass spectrometry data. Low frequency (approximation) coefficients, which contain major information contents of the mass spectra data, are extracted. Approximation of the spectra is reconstructed based on orthogonal wavelet approximation coefficients for locating the key m\\/z values of the mass spectra. Genetic algorithm is then used to select

Yihui Liu; Li Bai

2008-01-01

355

Theory of giant planet atmospheres and spectra  

NASA Astrophysics Data System (ADS)

Giant exoplanet atmospheres have now been studied by transit spectroscopy, spectroscopy and photometry at secondary eclipse, photometric light curves as a function of orbital phase, very high-resolution spectroscopic velocity measurements, and high-contrast imaging. Moreover, there is a correspondence between brown dwarf and giant planet atmospheres and spectra that has been profitably exploited for many years to better understand exoplanets. In this presentation, I endeavor to review the information extracted by these techniques about close-in giant exoplanet compositions and temperatures. Then, I will summarize the expected character of the spectra, light curves, and polarizations of the objects soon to be studied using high-contrast imaging by GPI, SPHERE, WFIRST-AFTA, and Subaru/HiCIAO as a function of mass, age, Keplerian elements, and birth properties (such as entropy). The goal will be to frame the theoretical discussion concerning what physical information can be gleaned in the next years about giant planet atmospheres by direct (or almost direct) imaging and characterization campaigns, and their role as stepping stones to the even more numerous sub-Neptunes, super-Earths, and Earths.

Burrows, Adam Seth

2014-06-01

356

Reflectance Spectra of Space Debris in GEO  

NASA Astrophysics Data System (ADS)

The space debris environment in the Geostationary Earth Orbit (GEO) region is mostly investigated by means of optical surveys. Such surveys revealed a considerable amount of debris in the size range of 10 centimeter to one meter. Some of these debris exhibit particularly high area-to-mass ratios as derived from the evolution of their orbits. In order to understand the nature and eventually the origin of these objects, observations allowing to derive physical characteristics like size, shape and material are required. Information on the shape and the attitude motion of a debris piece may be obtained by photometric light curves. The most promising technique to investigate the surface material properties is reflectance spectroscopy. This paper discusses preliminary results obtained from spectrometric observations of space debris in GEO. The observations were acquired at the 1-meter ESA Space Debris Telescope (ESASDT) on Tenerife with a low-resolution spectrograph in the wavelength range of 450-960 nm. The target objects were space debris of different types with brightness as small as magnitude 15. Some simple-shaped, intact "calibration objects" with known surface materials like the MSG-2 satellites were also observed. The spectra show shape variations expected to be caused by the different physical properties of the objects. The determination of the possible materials is still in a preliminary phase. Limitations of the acquisition process of the spectra and the subsequent analysis are discussed. Future steps planned for a better characterization of the debris from the observed data are briefly outlined.

Schildknecht, T.; Vannanti, A.; Krag, H.; Erd, C.

357

Spontaneously quenched ?-ray spectra from compact sources  

NASA Astrophysics Data System (ADS)

Aims: We have studied a mechanism for producing intrinsic broken power-law ?-ray spectra in compact sources. This is based on the principles of automatic photon quenching, according to which ?-rays are being absorbed on spontaneously produced soft photons whenever the injected luminosity in ?-rays lies above a certain critical value. Methods: We derived an analytical expression for the critical ?-ray compactness in the case of power-law injection. For the case where automatic photon quenching is relevant, we calculated analytically the emergent steady-state ?-ray spectra. We also performed numerical calculations in order to back up our analytical results. Results: We show that a spontaneously quenched power-law ?-ray spectrum obtains a photon index 3?/2, where ? is the photon index of the power-law at injection. Thus, large spectral breaks of the ?-ray photon spectrum, e.g. ?? ? 1, can be obtained by this mechanism. We also discuss additional features of this mechanism that can be tested observationally. Finally, we fit the multiwavelength spectrum of a newly discovered blazar (PKS 0447-439) by using such parameters to explain the break in the ?-ray spectrum by means of spontaneous photon quenching, under the assumption that its redshift lies in the range 0.1 < z < 0.24.

Petropoulou, M.; Arfani, D.; Mastichiadis, A.

2013-09-01

358

Infrared Spectra of Substituted Polycyclic Aromatic Hydrocarbons  

NASA Technical Reports Server (NTRS)

Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of 1-methylanthracene, 9-methylanthracene, 9-cyanoanthracene, 2-aminoanthracene, acridine, and their positive ions. The theoretical data are compared with matrix-isolation spectra for these species also reported in this work. The theoretical and experimental frequencies and relative intensities for the neutral species are in generally good agreement, whereas the positive ion spectra are only in qualitative agreement. Relative to anthracene, we find that substitution of amethyl or CN for a hydrogen does not significantly affect the spectrum other than to add the characteristic methyl C-H stretch and C-N stretch (near 2200/cm), respectively. However, addition of NH2 dramatically affects the spectrum of the neutral. Not only are the NH2 modes themselves strong, but this electron withdrawing group induces sufficient partial charge on the ring to give the neutral molecule characteristics of the anthracene cation spectrum. The sum of the absolute intensities is about four times larger for 2-aminoanthracene than for 9-cyanoanthracene. Substituting nitrogen in the ring at the nine position (acridine) does not greatly alter the spectrum compared with anthracene.

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Hudgins, Douglas M.; Sandford, Scott A.; Allamandola, Louis J.; Arnold, James O. (Technical Monitor)

1997-01-01

359

An atlas of selected calibrated stellar spectra  

NASA Technical Reports Server (NTRS)

Five hundred and fifty six stars in the IRAS PSC-2 that are suitable for stellar radiometric standards and are brighter than 1 Jy at 25 microns were identified. In addition, 123 stars that meet all of our criteria for calibration standards, but which lack a luminosity class were identified. An approach to absolute stellar calibration of broadband infrared filters based upon new models of Vega and Sirius due to Kurucz (1992) is presented. A general technique used to assemble continuous wide-band calibrated infrared spectra is described and an absolutely calibrated 1-35 micron spectrum of alpha(Tau) is constructed and the method using new and carefully designed observations is independently validated. The absolute calibration of the IRAS Low Resolution Spectrometer (LRS) database is investigated by comparing the observed spectrum of alpha(Tau) with that assumed in the original LRS calibration scheme. Neglect of the SiO fundamental band in alpha(Tau) has led to the presence of a specious 'emission' feature in all LRS spectra near 8.5 microns, and to an incorrect spectral slope between 8 and 12 microns. Finally, some of the properties of asteroids that effect their utility as calibration objects for the middle and far infrared region are examined. A technique to determine, from IRAS multiwaveband observations, the basic physical parameters needed by various asteroid thermal models that minimize the number of assumptions required is developed.

Walker, Russell G.; Cohen, Martin

1992-01-01

360

Cirrus Spectra of Low Surface Brightness Regions  

NASA Astrophysics Data System (ADS)

We have studied the galactic cirrus in low surface brightness regions using ISOPHOT raster maps at 90 microns, 150 microns and 180 microns. Observations are used to determine dust emission spectra and dust temperatures. The data extend to longer wavelengths than the IRAS observations. Compared with DIRBE data, the resolution and the sensitivity are better and this makes it possible to study faint cirrus emission in individual fields. We will discuss the calibration of the observations and present results of a comparison between ISOPHOT and DIRBE surface brightness values. The correspondence was found to be better than ~30%. At 90 microns the ISOPHOT surface brightnesses tend to be slightly higher than the DIRBE values while at longer wavelength the situation is reversed. Surface brightness variations caused by cirrus fluctuations make it possible to determine the spectrum of the dust emission. Cirrus spectra were obtained for six fields with surface brightnesses in the range 1--2 MJy sr-1 after the Zodiacal light and the contribution of extra-galactic sources have been subtracted. Assuming ?2 emissivity law the dust temperatures are in the range 18--20 K. Temperature variations can be seen even within individual fields. These values are higher than values from DIRBE but this can be explained by differences in the calibration.

Juvela, M.; Mattila, K.; Lemke, D.

361

Circular dichroism spectra of chiral gold nanoclusters  

NASA Astrophysics Data System (ADS)

Chiral structures have been found as the most stable isomers of bare (Au_28 and Au_55) and thiol-passivated [Au_28(SCH_3)_16 and Au_38(SCH_3)_24] gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure (HCM). From the calculated values of HCM, it is obtained that the thiol-passivation is a mechanism to induce or increase the chirality of the bare metal clusters (I.L. Garzon et al., Phys. Rev. B 66, 073403 (2002).). The circular dichroism (CD) spectra of gold nanoclusters with different HCM was calculated within the discrete-dipole approximation. The CD spectra show features that allow us to distinguish between different indexes of chirality. These results provide theoretical support for the existence of chirality in these compounds, and are consistent with the observed chiroptical activity, recently reported for glutathione-passivated gold nanoclusters (T.G. Schaaff and R.L. Whetten, J. Phys. Chem. B 104, 2630 (2000).).

Garzon, Ignacio L.; Roman-Velazquez, Carlos E.; Noguez, Cecilia

2003-03-01

362

Enhanced and Inhibited Gravity Wave Spectra.  

NASA Astrophysics Data System (ADS)

Balloon measurements were used to investigate gravity waves in the upper troposphere and lower stratosphere above the Canadian high Arctic. The amount of gravity wave activity in the stratosphere was found to be related to particular meteorological conditions that influence the generation and propagation of mountain waves. Enhanced wave activity was observed to occur when there was a small change in wind direction in the troposphere and high wind speed at the ground. These conditions correspond to strong wave generation by flow over the ground of upward-propagating waves that do not encounter critical level filtering. Inhibited wave activity was observed when the wind direction changed by more than 180° in the troposphere or when the wind speed was relatively weak at the ground. These conditions correspond to critical level filtering and weak generation of upward-propagating waves. The vertical wavenumber spectrum of perturbation potential energy was enhanced at all resolved scales when the conditions were favorable for upward wave propagation. The average enhanced spectral magnitude increased in proportion to the increase in N2 (buoyancy frequency squared) between the troposphere and stratosphere. When the background atmospheric conditions inhibited upward wave propagation the spectral magnitude did not change between the troposphere and stratosphere, despite a factor of 4 increase in N2. The enhanced spectra are consistent with the current gravity wave paradigm but the inhibited spectra are not so readily explained.

Whiteway, James A.

1999-05-01

363

Discriminating Dysarthria Type From Envelope Modulation Spectra  

PubMed Central

Purpose Previous research demonstrated the ability of temporally based rhythm metrics to distinguish among dysarthrias with different prosodic deficit profiles (J. M. Liss et al., 2009). The authors examined whether comparable results could be obtained by an automated analysis of speech envelope modulation spectra (EMS), which quantifies the rhythmicity of speech within specified frequency bands. Method EMS was conducted on sentences produced by 43 speakers with 1 of 4 types of dysarthria and healthy controls. The EMS consisted of the spectra of the slow-rate (up to 10 Hz) amplitude modulations of the full signal and 7 octave bands ranging in center frequency from 125 to 8000 Hz. Six variables were calculated for each band relating to peak frequency and amplitude and relative energy above, below, and in the region of 4 Hz. Discriminant function analyses (DFA) determined which sets of predictor variables best discriminated between and among groups. Results Each of 6 DFAs identified 2–6 of the 48 predictor variables. These variables achieved 84%–100% classification accuracy for group membership. Conclusions Dysarthrias can be characterized by quantifiable temporal patterns in acoustic output. Because EMS analysis is automated and requires no editing or linguistic assumptions, it shows promise as a clinical and research tool. PMID:20643800

Liss, Julie M.; LeGendre, Sue; Lotto, Andrew J.

2013-01-01

364

Millimeter wave absorption spectra of biological samples  

SciTech Connect

A solid-state computer-controlled system has been used to make swept-frequency measurements of absorption of biological specimens from 26.5 to 90.0 GHz. A wide range of samples was used, including solutions of DNA and RNA, and suspensions of BHK-21/C13 cells, Candida albicans, C krusei, and Escherichia coli. Sharp spectra reported by other workers were not observed. The strong absorbance of water (10--30 dB/mm) caused the absorbance of all aqueous preparations that we examined to have a water-like dependence on frequency. Reduction of incident power (to below 1.0 microW), elimination of modulation, and control of temperature to assure cell viability were not found to significantly alter the water-dominated absorbance. Frozen samples of BHK-21/C13 cells tested at dry ice and liquid nitrogen temperatures were found to have average insertion loss reduced to 0.2 dB/cm but still showed no reproducible peaks that could be attributed to absorption spectra. It is concluded that the special resonances reported by others are likely to be in error.

Gandhi, O.P.; Hagmann, M.J.; Hill, D.W.; Partlow, L.M.; Bush, L.

1980-01-01

365

A parametric scheme for the retrieval of two-dimensional ocean wave spectra from synthetic aperture radar look cross spectra  

Microsoft Academic Search

A parametric inversion scheme for the retrieval of two-dimensional (2-D) ocean wave spectra from look cross spectra acquired by spaceborne synthetic aperture radar (SAR) is presented. The scheme uses SAR observations to adjust numerical wave model spectra. The Partition Rescaling and Shift Algorithm (PARSA) is based on a maximum a posteriori approach in which an optimal estimate of a 2-D

J. Schulz-Stellenfleth; S. Lehner; D. Hoja

2005-01-01

366

1/ f? spectra in elementary cellular automata and fractal signals  

NASA Astrophysics Data System (ADS)

We systematically compute the power spectra of the one-dimensional elementary cellular automata introduced by Wolfram. On the one hand our analysis reveals that one automaton displays 1/f spectra though considered as trivial, and on the other hand that various automata classified as chaotic or complex display no 1/f spectra. We model the results generalizing the recently investigated Sierpinski signal to a class of fractal signals that are tailored to produce 1/f? spectra. From the widespread occurrence of (elementary) cellular automata patterns in chemistry, physics, and computer sciences, there are various candidates to show spectra similar to our results.

Nagler, Jan; Claussen, Jens Christian

2005-06-01

367

Spectra from a magnetic reconnection-heated corona in AGN  

E-print Network

We investigate a corona coupled with underlying disk through magnetic field and radiation field, and present emergent spectra calculated from Monte Carlo simulations. The spectra are determined for given black-hole mass and accretion rate. We find two types of solutions corresponding for hard spectrum and soft spectrum. In the hard-spectrum solution, the accretion energy is dominantly dissipated in the corona, supporting a strong corona above a cool disk; The hard X-ray spectral indices are around 1.1, same for different accretion rates. In the soft-spectrum solution, the accretion energy is mainly dissipated in the disk. The coronal temperature and density are quite low. Consequently, the spectra are dominated by the disk radiation peaking at UV and soft X-rays. For low-luminosity systems, there exists only the solution of hard spectra; While for high-luminosity systems, there exist both solutions of hard and soft spectra. For middle-luminosity systems, besides the hard spectra, moderately soft spectra composed of an inner soft-spectrum solution and an outer hard-spectrum solution may occur, the softness of which increases with increasing luminosity. The hard spectra are close to the observed spectra in Seyfert galaxies and radio-quiet QSOs. The composite spectra may account for the diversity of broad band spectra observed in narrow-line Seyfert 1 galaxies.

B. F. Liu; S. Mineshige; K. Ohsuga

2003-01-08

368

On the consistency of earthquake moment rates, geological fault data, and space geodetic strain: the United States  

Microsoft Academic Search

New and dense space geodetic data can now map strain rates over continental-wide areas with a useful degree of precision. Stable strain indicators open the door for space geodesy to join with geology and seismology in formulating improved estimates of global earthquake recurrence. In this paper, 174 GPS\\/VLBI velocities map United States' strain rates of 30.0 × 10-8 yr-1 with

Steven N. Ward

1998-01-01

369

The spectra spectroheliograph system, section 1. [production of magnetic field maps direct from solar spectra  

NASA Technical Reports Server (NTRS)

A system capable of producing maps of the magnetic field straight from spectra was created. The theory of the extraction of magnetic field information by Fourier transform techniques is discussed. Contour maps of a high gradient magnetic field region are presented.

Title, A. M.

1974-01-01

370

Infrared Spectra of Polycyclic Aromatic Hydrocarbons: Nitrogen Substitution  

NASA Technical Reports Server (NTRS)

The B3LYP/4-31G approach is used to compute the harmonic frequencies of substituted naphthalene, anthracene, and their cations. The substitutions include cyano (CN), aminio (NH2), imino (NH), and replacement of a CH group by a nitrogen atom. All unique sites are considered, namely 1 and 2 for naphthalene and 1, 2, and 9 for an'tracene, except for the imino, where only 2-iminonaphthalene is studied. The IR spectra of these substituted species are compared with those of the unsubstituted molecules. The addition of a CN group does not significantly affect the spectra except to add the CN stretching frequency. Replacing a CH group by N has only a small effect on the IR spectra. The addition of the NH2 group dramatically affects the neutral spectra, giving it much of the character of the cation spectra. However, the neutral 2-irrinonaphthalene spectra looks more like that of naphthalene than like the 2-aminonaphthalene spectra.

Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

1998-01-01

371

Mineral Spectra from Nili Fossae, Mars  

NASA Technical Reports Server (NTRS)

Spectra collected by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) indicate the presence of three distinct minerals. The graphed information comes from an observation of terrain in the Nili Fossae area of northern Mars. CRISM is one of six science instruments on NASA's Mars Reconnaissance Orbiter.

Iron-magnesium smectite clay is formed through alteration of rocks by liquid water and is characterized by distinctive absorptions at 1.4, 1.9, and 2.3 micrometers due to water (H2O) and OH in the atomic structure of the mineral. Olivine is an iron magnesium silicate and primary igneous mineral, and water is not in its structure. Its spectrum is characterized by a strong and broad absorption at 1.0 micrometer due to ferrous iron (Fe2+). Carbonate is an alteration mineral identified by the distinctive paired absorptions at 2.3 and 2.5 micrometers. The precise band positions at 2.31 and 2.51 micrometers identify the carbonate at this location as magnesium carbonate. The broad 1.0 micrometer band indicates some small amount of ferrous iron is also present and the feature at 1.9 micrometers indicates the presence of water. CRISM researchers believe the magnesium carbonate found in the Nili Fossae region formed from alteration of olivine by water.

The data come from a CRISM image catalogued as FRT00003E12. The spectra shown here are five-pixel-by-five-pixel averages of CRISM L-detector spectra taken from three different areas within the image that have then been ratioed to a five-pixel-by-five-pixel common denominator spectrum taken from a spectrally unremarkable area with no distinctive mineralogic signatures. This technique highlights the spectral contrasts between regions due to their unique mineralogy. The spectral wavelengths near 2.0 micrometers are affected by atmospheric absorptions and have been removed for clarity.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The Johns Hopkins University Applied Physics Laboratory led the effort to build the CRISM instrument and operates CRISM in coordination with an international team of researchers from universities, government and the private sector.

2008-01-01

372

Atomic line shapes in stellar spectra  

NASA Astrophysics Data System (ADS)

The spectrum emitted by a star is determined by the conditions where the photons last scatter in its atmosphere . It carries a signature of the presence of atomic species, and of the effects of atomic collisions and motions on the radiative process. To the astronomer interested in the star, these spectra offer clues to its composition, temperature, surface gravity, magnetic field, rotation and line-of-sight motion. To the atomic physicist, stellar spectra are a probe for collision processes under conditions that are difficult to reproduce in a laboratory. Indeed, an understanding of the underpinning line shape physics is key to exploring a wide range of interesting astronomical phenomena-answering questions about the color and composition of brown dwarfs, the temperature, size and age of white dwarfs, and the detection of extrasolar planets and their atmospheres. The theory of spectral line shapes, especially the unified approach we have developed, makes possible accurate models of stellar spectra that account both for the centers of spectral lines and their extreme wings in one consistent treatment. Under some circumstances it is possible to test the line shape theories in the laboratory, if not under conditions exactly the same as those in stars, at least under closely similar conditions. For application to cool brown dwarf stars, for example, with an atmosphere of molecular hydrogen and the alkali metals, conventional laboratory absorption spectroscopy can be used to examine the line wing, to measure the broadening of the line center, and to determine shifts of lines due to collisions. At the other extreme of temperature, a shock wave in a laser-produced plasma produces for a few nanoseconds a dense partially ionized atomic hydrogen source at the temperature of a white dwarf star. A comparison of laboratory experimental data with theoretical profiles establishes the accuracy of the interaction potentials, which remain difficult to compute a priori precisely in most cases. In this paper, we will show work now in progress that compares unified line shape calculations with new experiments to determine the wings of the sodium and potassium resonance lines broadened by molecular hydrogen and helium, and that looks at the role of the ion collisions in determining the widths and shift of Balmer ? when the electron/proton density is much higher than found in the usual laboratory plasma arc sources.

Kielkopf, John F.; Allard, Nicole F.

2008-10-01

373

Jets and Bombs: Characterizing IRIS Spectra  

NASA Astrophysics Data System (ADS)

For almost two decades, SUMER has provided an unique perspective on explosive events in the lower solar atmosphere. One of the hallmark observations during this tenure is the identification of quiet sun bi-directional jets in the lower transition region. We investigate these events through two distinct avenues of study: a MHD model for reconnection and the new datasets of the Interface Region Imaging Spectrograph (IRIS). Based on forward modeling optically thin spectral profiles, we find the spectral signatures of reconnection can vary dramatically based on viewing angle and altitude. We look to the IRIS data to provide a more complete context of the chromospheric and coronal environment during these dynamic events. During a joint IRIS-SUMER observing campaign, we observed spectra of multiple jets, a small C flare, and an Ellerman bomb event. We discuss the questions that arise from the inspection of these new data.

Schmit, Donald; Innes, Davina

2014-06-01

374

Spectra of Particulate Backscattering in Natural Waters  

NASA Technical Reports Server (NTRS)

Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (bb) of the water and its constituents. The absorption coefficient at the mesotrophic station clearly shows spectral absorption features attributable to several phytoplankton pigments (Chlorophyll a, b, c, and Carotenoids). The backscattering shows only weak spectral features and can be well represented by a power-law variation with wavelength (lambda): b(sub b) approx. Lambda(sup -n), where n is a constant between 0.4 and 1.0. However, the weak spectral features in b(sub b), suggest that it is depressed in spectral regions of strong particle absorption. The applicability of the present inverse radiative transfer algorithm, which omits the influence of Raman scattering, is limited to lambda < 490 nm in oligotrophic waters and lambda < 575 nm in mesotrophic waters.

Gordon, Howard, R.; Lewis, Marlon R.; McLean, Scott D.; Twardowski, Michael S.; Freeman, Scott A.; Voss, Kenneth J.; Boynton, Chris G.

2009-01-01

375

Vibrational spectra and DFT calculations of squalene  

NASA Astrophysics Data System (ADS)

The isoprenoid compound squalene is a building block molecule for the production of essential cellular molecules such as membrane sterols, has several therapeutic activities including anticancer properties, and has commercial applications for a variety of industries including the production of cosmetics. While the physical structure of squalene has been known for many years, a spectroscopic understanding of the squalene molecular structure and how these spectrometric properties relate to the physical squalene structure has yet to be reported. In the present work we present the Raman and infrared spectra of liquid squalene, complemented by DFT calculations. The molecule has 234 vibrational frequencies and these have been categorized according to the different types of vibrational modes present. The vibrational modes are highly mixed and these have been assigned for the more prominent infrared and Raman bands.

Chun, Hye Jin; Weiss, Taylor L.; Devarenne, Timothy P.; Laane, Jaan

2013-01-01

376

Measure fiber position errors from spectra data  

E-print Network

Precise fiber positioning is crucial to a wide field, multi-fiber spectroscopic survey like LAMOST. Nowadays, most position error measurements are based on CCD photographic and imaging processing techniques. Those methods only work for measuring errors orthogonal to the telescope optical axis, while there also lies errors parallel to the telescope optical axis, like defocusing, and error caused by the existing deviation angle between optical axes of a fiber and the telescope. Directly measuring two latter types of position errors is difficult for individual fiber, especially during observation. Possible sources of fiber position errors are discussed in brief for LAMOST. By constructing a model of magnitude loss due to the fiber position error for a point source, we propose an indirect method to calculate the total and systematic position errors for each individual fiber from spectra data. Restrictions and applications of this method are also discussed.

Chen, Jian-Jun; Luo, A-Li; Zhao, Yong-Heng

2014-01-01

377

Two-photon spectra of quantum emitters  

NASA Astrophysics Data System (ADS)

We apply our recently developed theory of frequency-filtered and time-resolved N-photon correlations (del Valle et al 2012 Phys. Rev. Lett. 109 183601) to study the two-photon spectra of a variety of systems of increasing complexity: single-mode emitters with two limiting statistics (one harmonic oscillator or a two-level system) and the various combinations that arise from their coupling. We consider both the linear and nonlinear regimes under incoherent excitation. We find that even the simplest systems display a rich dynamics of emission, not accessible by simple single-photon spectroscopy. In the strong coupling regime, two-photon emission processes involving virtual states are revealed. Furthermore, two general results are unravelled by two-photon correlations with narrow linewidth detectors: (i) filtering-induced bunching and (ii) breakdown of the semi-classical theory. We show how to overcome the latter in a fully quantized picture.

Gonzalez-Tudela, Alejandro; Laussy, Fabrice P.; Tejedor, Carlos; Hartmann, Michael J.; del Valle, Elena

2013-03-01

378

The complex X ray spectra of AGN  

NASA Technical Reports Server (NTRS)

X-ray spectral surveys of large samples of Seyfert galaxies are discussed. The spectral shape in the 0.1 to 20 keV energy range is considered. Two new spectral survey are undertaken, one involving 105 Imaging Proportional Counter (IPC) observations of 75 Seyfert galaxies, the other using IPC and Monitor Proportional Counter (MPC) data from 28 observations of 23 Seyfert galaxies. The X-ray spectra of active galactic nuclei (AGN) are complex, with in most cases considerable steepening at the lowest energies. At higher energies (2 to 20 keV), the existence of a universal, canonical power law is confirmed, independent of X-ray luminosity over four orders of magnitude.

Urry, C. M.; Arnaud, Keith; Edelson, R. A.; Kruper, J. S.; Mushotzky, R. F.

1989-01-01

379

The radio spectra of galactic nuclei  

E-print Network

We present a model for the inverted radio spectra of active active galactic nuclei as well as the central regions of normal galaxies. The model is based on the unified scenario for active galaxies, stating that the central engines of active galaxies consists of a supermassive black hole surrounded by an accretion disk and a radio jet. The nuclei of normal (i. e. less active) galaxies are supposed to be scaled-down versions of the same phenomenon. We show that the radio emission of a jet component, becoming optically thin to the radio emission of a monoenergetic pair plasma at decreasing frequencies as it moves outward and expands, is well suited to explain the observational results. We present a model calculation for the special case of the nucleus of M~81.

M. Boettcher; H. -P. Reuter; H. Lesch

1997-07-31

380

X ray spectra of cataclysmic variables  

NASA Technical Reports Server (NTRS)

X ray spectral parameters of cataclysmic variables observed with the 'Einstein' imaging proportional counter were determined by fitting an optically thin, thermal bremsstrahlung spectrum to the raw data. Most of the sources show temperatures of order a few keV, while a few sources exhibit harder spectra with temperatures in excess of 10 keV. Estimated 0.1 to 3.5 keV luminosities are generally in the range from 10(exp 30) to 10(exp 32) erg/sec. The results are consistent with the x rays originating in a disk/white dwarf boundary layer of non-magnetic systems, or in a hot, post-shock region in the accretion column of DQ Her stars, with a negligible contribution from the corona of the companion. In a few objects column densities were found that are unusually high for interstellar material. It was suggested that the absorption occurs in the system itself.

Patterson, Joseph; Halpern, Jules

1990-01-01

381

Chemical and isotopic determination from complex spectra  

SciTech Connect

Challenges for proliferation detection include remote, high- sensitivity detection of chemical effluents from suspect facilities and enhanced detection sensitivity for nuclear material. Both the identification of chemical effluents with lidar and enhanced nuclear material detection from radiation sensors involve determining constituents from complex spectra. In this paper, we extend techniques used to analyze time series to the analysis of spectral data. Pattern identification methods are applied to spectral data for domains where standard matrix inversion may not be suitable because of detection statistics. We use a feed-forward, back-propagation neural network in which the nodes of the input layer are fed with the observed spectral data. The nodes of the output layer contain the identification and concentration of the isotope or chemical effluent the sensor is to identify. We will discuss the neural network architecture, together with preliminary results obtained from the training process.

Zardecki, A.; Strittmatter, R.B.

1995-07-01

382

A Study of Pioneer Venus Nightglow Spectra  

NASA Technical Reports Server (NTRS)

The work performed during the 12-month period of this contract involved: (1) further analysis of latitudinal variations in the Venusian NO nightglow intensity from PVOUVS data; (2) corrections made to the input data for the VTGCM model, relating specifically to a factor of three increase in the three-body recombination rate coefficient of N + O; (3) consideration of limits on the rate of reaction of N-atoms with CO2; (4) consideration of the Venusian equivalent of the terrestrial hot N-atom reaction for NO production; and (5) successful location of video images of meteor trails from space, for the purpose of making a comparison with the meteor trail that we have hypothesized as an explanation of intense UV spectra observed on a particular Pioneer Venus (PV) orbit.

Slanger, Tom G.

1993-01-01

383

Spectra as windows into exoplanet atmospheres.  

PubMed

Understanding a planet's atmosphere is a necessary condition for understanding not only the planet itself, but also its formation, structure, evolution, and habitability. This requirement puts a premium on obtaining spectra and developing credible interpretative tools with which to retrieve vital planetary information. However, for exoplanets, these twin goals are far from being realized. In this paper, I provide a personal perspective on exoplanet theory and remote sensing via photometry and low-resolution spectroscopy. Although not a review in any sense, this paper highlights the limitations in our knowledge of compositions, thermal profiles, and the effects of stellar irradiation, focusing on, but not restricted to, transiting giant planets. I suggest that the true function of the recent past of exoplanet atmospheric research has been not to constrain planet properties for all time, but to train a new generation of scientists who, by rapid trial and error, are fast establishing a solid future foundation for a robust science of exoplanets. PMID:24613929

Burrows, Adam S

2014-09-01

384

Measuring Reddening with SDSS Stellar Spectra  

NASA Astrophysics Data System (ADS)

We present measurements of dust reddening using the colors of stars with spectra in the Sloan Digital Sky Survey. We measure reddening as the difference between the measured colors of a star and the predicted colors, as derived from stellar parameters from the SEGUE Stellar Parameter Pipeline. We achieve uncertainties of 54, 34, 25, and 28 mmag in the colors u-g, g-r, r-i, and i-z, per star, though the uncertainty varies depending on the stellar type and the magnitude of the star. The spectrum-based reddening measurements confirm our earlier "blue tip" reddening measurements, preferring an RV = 3.1 Fitzpatrick (1999) reddening law to O'Donnell (1994) or Cardelli et al. (1989) reddening laws. We obtain a reddening law normalization within 4% of the blue tip results, despite the somewhat different sky footprint used in the two analyses.

Schlafly, Eddie; Finkbeiner, D. P.

2011-01-01

385

On Magnetic Spectra of Earth and Mars  

NASA Technical Reports Server (NTRS)

The spectral method for distinguishing crustal from core-source magnetic fields is reexamined, modified, and applied to both a comprehensive geomagnetic field model and an altitude normalized magnetic map of Mars. The observational spectra are fairly fitted by theoretical forms expected from certain elementary classes of magnetic sources. For Earth we find fields from a core of radius 3512 +/- 64 km, in accord with the seismologic core radius of 3480 km, and a crust represented by a shell of random dipolar sources at radius 6367 +/- 14 km, near the planetary mean radius of 6371.2 km. For Mars we find no sign of a core-source field, only a field from a crust represented in same way, but at radius 3344 +/- 10 km, about 46 km below the planetary mean radius of 3389.5 km, and with sources about 9.6 +/- 3.2 times stronger.

Voorhies, C. V.; Sabaka, T. J.; Purucker, M.

2002-01-01

386

Workshop to establish databases of carbohydrate spectra  

SciTech Connect

The workshop was organized to formulate guidelines for establishing spectral databases of complex carbohydrates. The databases will enable the scientific community to avoid the great waste of research effort and funds that frequently occurs when carbohydrate chemists are forced to duplicate the structural characterization of previously characterized complex carbohydrates. Chemists waste their effort on repetitive characterizations because in the absence of spectral databases they are unaware they are analyzing a known molecule until they have completely determined its structure. Chemists will be able to avoid much of this wasted effort when the collections of mass and of nuclear magnetic resonance (NMR) spectra initiated at the workshop are subsequently developed into searchable databases. Then scientists only need query the databases with the spectrum or with information defining the spectrum of an unidentified carbohydrate to find out if it has been previously characterized.

NONE

1995-12-31

387

Prediction of electroencephalographic spectra from neurophysiology  

NASA Astrophysics Data System (ADS)

A recent neurophysical model of propagation of electrical waves in the cortex is extended to include a physiologically motivated subcortical feedback loop via the thalamus. The electroencephalographic spectrum when the system is driven by white noise is then calculated analytically in terms of physiological parameters, including the effects of filtering of signals by the cerebrospinal fluid, skull, and scalp. The spectral power at low frequencies is found to vary as f-1 when awake and f-3 when asleep, with a breakpoint to a steeper power-law tail at frequencies above about 20 Hz in both cases; the f-1 range concurs with recent magnetoencephalographic observations of such a regime. Parameter sensitivities are explored, enabling a model with fewer free parameters to be proposed, and showing that spectra predicted for physiologically reasonable parameter values strongly resemble those observed in the laboratory. Alpha and beta peaks seen near 10 Hz and twice that frequency, respectively, in the relaxed wakeful state are generated via subcortical feedback in this model, thereby leading to predictions of their frequencies in terms of physiological parameters, and of correlations in their occurrence. Subcortical feedback is also predicted to be responsible for production of anticorrelated peaks in deep sleep states that correspond to the occurrence of theta rhythm at around half the alpha frequency and sleep spindles at 3/2 times the alpha frequency. An additional positively correlated waking peak near three times the alpha frequency is also predicted and tentatively observed, as are two new types of sleep spindle near 5/2 and 7/2 times the alpha frequency, and anticorrelated with alpha. These results provide a theoretical basis for the conventional division of EEG spectra into frequency bands, but imply that the exact bounds of these bands depend on the individual. Three types of potential instability are found: one at zero frequency, another in the theta band at around half the alpha frequency, and a third at the alpha frequency itself.

Robinson, P. A.; Rennie, C. J.; Wright, J. J.; Bahramali, H.; Gordon, E.; Rowe, D. L.

2001-02-01

388

Cooling Flow Spectra in Ginga Galaxy Clusters  

NASA Technical Reports Server (NTRS)

The primary focus of this research project has been a joint analysis of Ginga LAC and Einstein SSS X-ray spectra of the hot gas in galaxy clusters with cooling flows is reported. We studied four clusters (A496, A1795, A2142 & A2199) and found their central temperatures to be cooler than in the exterior, which is expected from their having cooling flows. More interestingly, we found central metal abundance enhancements in two of the clusters, A496 and A2142. We have been assessing whether the abundance gradients (or lack thereof) in intracluster gas is correlated with galaxy morphological gradients in the host clusters. In rich, dense galaxy clusters, elliptical and SO galaxies are generally found in the cluster cores, while spiral galaxies are found in the outskirts. If the metals observed in clusters came from proto-ellipticals and proto-S0s blowing winds, then the metal distribution in intracluster gas may still reflect the distribution of their former host galaxies. In a research project which was inspired by the success of the Ginga LAC/Einstein SSS work, we analyzed X-ray spectra from the HEAO-A2 MED and the Einstein SSS to look for temperature gradients in cluster gas. The HEAO-A2 MED was also a non-imaging detector with a large field of view compared to the SSS, so we used the differing fields of view of the two instruments to extract spatial information. We found some evidence of cool gas in the outskirts of clusters, which may indicate that the nominally isothermal mass density distributions in these clusters are steepening in the outer parts of these clusters.

White, Raymond E., III

1997-01-01

389

THEORETICAL SPECTRA OF TERRESTRIAL EXOPLANET SURFACES  

SciTech Connect

We investigate spectra of airless rocky exoplanets with a theoretical framework that self-consistently treats reflection and thermal emission. We find that a silicate surface on an exoplanet is spectroscopically detectable via prominent Si-O features in the thermal emission bands of 7-13 {mu}m and 15-25 {mu}m. The variation of brightness temperature due to the silicate features can be up to 20 K for an airless Earth analog, and the silicate features are wide enough to be distinguished from atmospheric features with relatively high resolution spectra. The surface characterization thus provides a method to unambiguously identify a rocky exoplanet. Furthermore, identification of specific rocky surface types is possible with the planet's reflectance spectrum in near-infrared broad bands. A key parameter to observe is the difference between K-band and J-band geometric albedos (A{sub g}(K) - A{sub g}(J)): A{sub g}(K) - A{sub g}(J) > 0.2 indicates that more than half of the planet's surface has abundant mafic minerals, such as olivine and pyroxene, in other words primary crust from a magma ocean or high-temperature lavas; A{sub g}(K) - A{sub g}(J) < -0.09 indicates that more than half of the planet's surface is covered or partially covered by water ice or hydrated silicates, implying extant or past water on its surface. Also, surface water ice can be specifically distinguished by an H-band geometric albedo lower than the J-band geometric albedo. The surface features can be distinguished from possible atmospheric features with molecule identification of atmospheric species by transmission spectroscopy. We therefore propose that mid-infrared spectroscopy of exoplanets may detect rocky surfaces, and near-infrared spectrophotometry may identify ultramafic surfaces, hydrated surfaces, and water ice.

Hu Renyu; Seager, Sara [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Ehlmann, Bethany L., E-mail: hury@mit.edu [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)

2012-06-10

390

Polarization effects in cutaneous autofluorescent spectra  

NASA Astrophysics Data System (ADS)

Used polarized light for fluorescence excitation one could obtain response related to the anisotropy features of extracellular matrix. The fluorophore anisotropy is attenuated during lesions' growth and level of such decrease could be correlated with the stage of tumor development. Our preliminary investigations are based on in vivo point-by-point measurements of excitation-emission matrices (EEM) from healthy volunteers skin on different ages and from different anatomical places using linear polarizer and analyzer for excitation and emission light detected. Measurements were made using spectrofluorimeter FluoroLog 3 (HORIBA Jobin Yvon, France) with fiber-optic probe in steady-state regime using excitation in the region of 280-440 nm. Three different situations were evaluated and corresponding excitation-emission matrices were developed - with parallel and perpendicular positions for linear polarizer and analyzer, and without polarization of excitation and fluorescence light detected from a forearm skin surface. The fluorescence spectra obtained reveal differences in spectral intensity, related to general attenuation, due to filtering effects of used polarizer/analyzer couple. Significant spectral shape changes were observed for the complex autofluorescence signal detected, which correlated with collagen and protein cross-links fluorescence, that could be addressed to the tissue extracellular matrix and general condition of the skin investigated, due to morphological destruction during lesions' growth. A correlation between volunteers' age and the fluorescence spectra detected was observed during our measurements. Our next step is to increase developed initial database and to evaluate all sources of intrinsic fluorescent polarization effects and found if they are significantly altered from normal skin to cancerous state of the tissue, this way to develop a non-invasive diagnostic tool for dermatological practice.

Borisova, E.; Angelova, L.; Jeliazkova, Al.; Genova, Ts.; Pavlova, E.; Troyanova, P.; Avramov, L.

2014-05-01

391

Far infrared spectra of hydrous layer silicates  

NASA Astrophysics Data System (ADS)

Observation of major bands seen in infrared spectra of 26 phyllosilicates (23 of which were produced in the laboratory) are reported for wave numbers from 50 to 280 cm-1. Substitutions in the various structural sites (interlayer, tetrahedral and octahedral) permit one to identify the ions which contribute to the vibrations which give rise to bands in the infrared spectra. No attempt is made to assign vibrational modes or specific vibrational types. Using the following ion substitutions, OH-OD; Na-K-Sr-Mg-Ca; Si-Ge; Al-Ga; Mg-Co-Ni-Fe, it is apparent that in the 7 Å chlorite (amesite and chrysotile), kaolinite, pyrophyllite, aluminous dioctahedral mica, aluminous smectites and trioctahedral micas it is not possible to attribute any low frequency bands as being dominated by interlayer ion stretch vibrations (alkali ions). The cations which participate in the vibrators responsible for the dominant modes observed then seem to be Si and Al. This does not exclude the existence of interlayer ion stretch modes in these spectral regions, however they could not be identified. In the materials studied only a few bands can be attributed to hydroxyl-related vibrations and little influence is seen for octahedrally coordinated ions in dioctahedral minerals. It is important to note that the lowest frequency bands (80 140 cm-1) are apparently dominated by vibrations in the network and especially to the Si-O part of the structure. Low frequency bands are however most apparent in charged layer structures, i.e. micas and smectites.

Velde, B.; Couty, R.

1985-11-01

392

CO2 profile retrievals from TCCON spectra  

NASA Astrophysics Data System (ADS)

The Total Carbon Column Observing Network (TCCON) is a global network of ground-based Fourier Transform Spectrometers recording direct solar spectra in the near-infrared spectral region. With stringent requirements on the instrumentation, data processing and calibration, accurate and precise column-averaged abundances of CO2, CH4, N2O, HF, CO, H2O, and HDO are retrieved being an essential contribution for the validation of satellite data (e.g. GOSAT, OCO-2) and carbon cycle research (Olsen and Randerson, 2004). However, the determined column-averaged dry air mole fraction (DMF) contains no information about the vertical CO2 profile, due to the use of a simple scaling retrieval within the common TCCON analysis, where the fitting algorithm GFIT (e.g. Yang et al., 2005) is used. In this presentation we will apply a different procedure for calculating trace gas abundances from the measured spectra, the fitting algorithm PROFFIT (Hase et. al., 2004) which has been shown to be in very good accordance with GFIT. PROFFIT additionally offers the ability to perform profile retrievals in which the pressure broadening effect of absorption lines is used to retrieve vertical gas profiles, being of great interest especially for the CO2 modelling community. A new analyzing procedure will be shown and retrieved vertical CO2 profiles of the TCCON sites Izaña (Tenerife, Canary Islands, Spain) and Lamont (Oklahoma, USA) will be presented and compared with simultaneously performed surface in-situ measurements and CO2 profiles from different aircraft campaigns. References: - Hase, F. et al., J.Q.S.R.T. 87, 25-52, 2004. - Olsen, S.C. and Randerson, J.T., J.G.Res., 109, D023012, 2004. - Yang, Z. et al., J.Q.S.R.T., 90, 309-321, 2005.

Dohe, Susanne; Hase, Frank; Sepúlveda, Eliezer; García, Omaira; Wunch, Debra; Wennberg, Paul; Gómez-Peláez, Angel; Abshire, James B.; Wofsy, Steven C.; Schneider, Matthias; Blumenstock, Thomas

2014-05-01

393

Horizon-Unbiased Utility Functions Vicky Henderson  

E-print Network

DMI 0447990 is ac- knowledged. Department of Mathematical Sciences, University of Bath, Bath. BA2 7AY. UK. Email: dgh@maths.bath.ac.uk. This author is supported by an Epsrc Advanced Fellowship. 1 #12;the including both a riskless bank account and risky asset. In contrast to the indivisible real asset

394

Unbiased Blind Adaptive Channel Identification and Equalization  

Microsoft Academic Search

The blind and adaptive equalization or identification of communication channels is a problem ofimportant theoretical and practical concerns. Many recently proposed solutions typically exploit thediversity induced by sensor arrays or time oversampling, leading to the so-called second-order multichanneltechniques. However, some of these methods build on conditions or equations which are validin the noise free case only. This notably includes the

David Gesbert; Pierre Duhamel

1997-01-01

395

Unbiased Fitting of Dust Continuum Observations  

NASA Astrophysics Data System (ADS)

We present the results of an ubiased, automated approach to fitting infrared observations of interstellar dust clouds for the purposes of constraining their underlying physical properties. The dust radiative transfer is solved self-consistently in spherical geometry, producing simulated observations for comparison with actual observational data. The results are iterated until a best-fit chi-squared is achieved, producing constraints on the model parameters and hence source properties. As a test, we apply the approach to the well-studied source B335. We find that the source properties such as density distribution and grain properties can be reasonably constrained, providing an interesting physical picture of this region.

Doty, Steven D.; Tidman, R.; Shirley, Y.; Jackson, A.

2010-01-01

396

Database-Driven Analyses of Astronomical Spectra  

NASA Astrophysics Data System (ADS)

Spectroscopy is one of the most powerful tools to study the physical properties and chemical composition of very diverse astrophysical environments. In principle, each nuclide has a unique set of spectral features; thus, establishing the presence of a specific material at astronomical distances requires no more than finding a laboratory spectrum of the right material that perfectly matches the astronomical observations. Once the presence of a substance is established, a careful analysis of the observational characteristics (wavelengths or frequencies, intensities, and line profiles) allows one to determine many physical parameters of the environment in which the substance resides, such as temperature, density, velocity, and so on. Because of this great diagnostic potential, ground-based and space-borne astronomical observatories often include instruments to carry out spectroscopic analyses of various celestial objects and events. Of particular interest is molecular spectroscopy at infrared wavelengths. From the spectroscopic point of view, molecules differ from atoms in their ability to vibrate and rotate, and quantum physics inevitably causes those motions to be quantized. The energies required to excite vibrations or rotations are such that vibrational transitions generally occur at infrared wavelengths, whereas pure rotational transitions typically occur at sub-mm wavelengths. Molecular vibration and rotation are coupled though, and thus at infrared wavelengths, one commonly observes a multitude of ro-vibrational transitions (see Figure 13.1). At lower spectral resolution, all transitions blend into one broad ro-vibrational molecular band. The isotope. Molecular spectroscopy thus allows us to see a difference of one neutron in an atomic nucleus that is located at astronomical distances! Since the detection of the first interstellar molecules (the CH [21] and CN [14] radicals), more than 150 species have been detected in space, ranging in size from diatomic species to the fullerene species C60 and C70 [4]. Given the large number and variety of molecules detected in space, molecular infrared spectroscopy can be used to study pretty much any astrophysical environment that is not too energetic to dissociate the molecules. At the lowest energies, it is interesting to note that molecules such as CN have been used to measure the temperature of the Cosmic Microwave Background (see e.g., Ref. 15). The great diagnostic potential of infrared molecular spectroscopy comes at a price though. Extracting the physical parameters from the observations requires expertise in knowing how various physical processes and instrumental characteristics play together in producing the observed spectra. In addition to the astronomical aspects, this often includes interpreting and understanding the limitations of laboratory data and quantum-chemical calculations; the study of the interaction of matter with radiation at microscopic scales (called radiative transfer, akin to ray tracing) and the effects of observing (e.g., smoothing and resampling) on the resulting spectra and possible instrumental effects (e.g., fringes). All this is not trivial. To make matters worse, observational spectra often contain many components, and might include spectral contributions stemming from very different physical conditions. Fully analyzing such observations is thus a time-consuming task that requires mastery of several techniques. And with ever-increasing rates of observational data acquisition, it seems clear that in the near future, some form of automation is required to handle the data stream. It is thus appealing to consider what part of such analyses could be done without too much human intervention. Two different aspects can be separated: the first step involves simply identifying the molecular species present in the observations. Once the molecular inventory is known, we can try to extract the physical parameters from the observed spectral properties. For both steps, good databases of molecular spectroscopic information is vital; the second step furthermor

Cami, Jan

2012-03-01

397

Infrared reflectance spectra (4-12 micron) of lunar samples  

NASA Technical Reports Server (NTRS)

Presented here are infrared reflectance spectra of a typical set of Apollo samples to illustrate spectral character in the mid-infrared (4 to 12 microns) of lunar materials and how the spectra varies among three main forms: soil, breccia, and igneous rocks. Reflectance data, to a close approximation, are the inverse of emission spectra; thus, for a given material the spectral reflectance (R) at any given wavelength is related to emission (E) by 1 - R equals E. Therefore, one can use reflectance spectra of lunar samples to predict how emission spectra of material on the lunar surface will appear to spectrometers on orbiting spacecraft or earthbound telescopes. Spectra were measured in the lab in dry air using a Fourier Transform Infrared spectrometer. Shown here is only the key portion (4 to 12 microns) of each spectrum relating to the principal spectral emission region for sunlit lunar materials and to where the most diagnostic spectral features occur.

Nash, Douglas B.

1991-01-01

398

Monte Carlo simulation of Auger-electron spectra.  

PubMed

A procedure to calculate the complex spectra of electron-capture nuclides which simultaneously eject several electrons and X-rays with different energies is presented. The model is applied to compute spectra of the radionuclides (125)I, (123)I and (111)In. The spectra are then compared with experimental spectra obtained by means of liquid scintillation counting. To this end, the computed spectra were transformed to allow for the nonlinear response function for a liquid scintillator, chemical quenching, as well as the Wallac-type amplifier used for the measurements. The calculated spectra are important for applications of free parameter models in liquid scintillation counting and also for studying the impact of electron-capture nuclides on DNA. PMID:19013824

Grau Carles, A; Kossert, K

2009-01-01

399

Camera artifacts in IUE low-dispersion spectra  

NASA Technical Reports Server (NTRS)

Sky-background images obtained by the International Ultraviolet Explorer (IUE) were analyzed to study artificial spectral features (camera artifacts) in low-dispersion spectra. The artifacts mimic emission features and have been present in long-exposure spectra since the launch of the IUE satellite. The camera artifacts are strong in spectra characterized by long exposure times because they scale in time-integrated flux with the background level, which increases during the exposure due to camera phosphorescence. The artifacts cannot be detected in spectra obtained from short, direct exposures of flat-field lamps or standard stars. Plots of average sky-background spectra for the three operational IUE cameras (SWP, LWP, and LWR) are given to aid scientists in the identification of artifacts in their spectra.

Crenshaw, D. Michael; Norman, Dara J.; Bruegman, Otto W.

1990-01-01

400

Instabilotyping Reveals Unique Mutational Spectra in Microsatellite-Unstable Gastric Cancers1  

Microsoft Academic Search

Microsatellite instability (MSI) within coding regions causes frameshift mutations (FSMs). This type of mutation may inactivate tumor suppressor genes in cancers with frequent MSI (MSI-H cancers). To identify novel FSMs in gastric carcinogenesis in an unbiased and comprehensive man- ner, we screened for this type of mutation at 154 coding region repeat loci in 18 MSI-H gastric cancers. We also

Yuriko Mori; Fumiaki Sato; Florin M. Selaru; Andreea Olaru; Kellie Perry; Martha C. Kimos; Gen Tamura; Nagahide Matsubara; Suna Wang; Yan Xu; Jing Yin; Tong-Tong Zou; Barbara Leggett; Joanne Young; Toshihiro Nukiwa; O. Colin Stine; John M. Abraham; David Shibata; Stephen J. Meltzer

2002-01-01

401

Variable-temperature infrared spectra of VO/sub 2/  

SciTech Connect

The infrared spectra of VO/sub 2/ powder in KBr from 1300 to 400 cm/sup -1/ during heating and cooling through the metal-insulator transition are reported. In the high-temperature metallic region, the spectra are nearly featureless, while below the transition temperature well-developed vibrational bands are observed. The spectra at room temperature before and after heating are superimposable, a result consistent with the reversibility of the metal-insulator transition.

Hewston, T.A.; Nadler, M.P.

1987-11-01

402

The angular power spectra of polarized Galactic synchrotron  

Microsoft Academic Search

We derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36???103 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to ??103 are approximated very well by power laws with slope coefficients ?1.4, quite different from the CMB spectra. We

M. Tucci; E. Carretti; S. Cecchini; R. Fabbri; M. Orsini; E. Pierpaoli

2000-01-01

403

Resonant Compton scattering and gamma-ray burst continuum spectra  

NASA Technical Reports Server (NTRS)

The Thomson limit of resonant inverse Compton scattering in the strong magnetic fields of neutron stars is considered as a mechanism for producing gamma-ray burst continuum spectra. Photon production spectra and electron cooling rates are presented using the full magnetic Thomson cross-section. Model emission spectra are obtained as self-consistent solutions of a set of photon and electron kinetic equations, displaying spectral breaks and other structure at gamma-ray energies.

Baring, M. G.

1995-01-01

404

Extra EPR Spectra of Iron-Doped Rutile  

Microsoft Academic Search

We have discovered that besides the well-known EPR spectrum of Fe3+ substitutional ions in iron-doped rutile there are several other EPR spectra related to Fe3+ ions. The interpretation of these extra spectra was made considering the intensity variation with heat treatment and the orientation of the magnetic axes of the extra spectra. Isofrequency diagrams were recorded at 9.2 GHz and

Per-Olof Andersson; Erik L. Kollberg; Andrzej Jelenski

1973-01-01

405

Cascade hypernuclear production spectra at J-PARC  

Microsoft Academic Search

We predict cascade hypernuclear production spectra expected in the forthcoming J-PARC experiment. In the Green's function method of the distorted wave impulse wave approximation with the local optimal Fermi averaging t-matrix, we can describe the Xi production spectra in the continuum and bound state region reasonably well. Predictions to the high resonlution spectra at J-PARC suggest hat we should observe

Hideki Maekawa; Kohsuke Tsubakihara; Hiroshi Matsumiya; Akira Ohnishi

2007-01-01

406

Ultraviolet Stellar and Cluster Spectra Compared to Theoretical Templates  

Microsoft Academic Search

As part of NASA and Hubble Treasury programs, we are generating theoretical spectra for globular clusters and galaxies from\\u000a first principles. To check their validity, we are assessing how well they match high-resolution echelle spectra of the Sun\\u000a and nearby stars. Once agreement is reasonable, spectra at fixed metallicity and light-element enhancement are coadded with\\u000a weights representing the relative contribution

Ruth C. Peterson

407

Sequence Database Compression for Peptide Identification from Tandem Mass Spectra  

Microsoft Academic Search

The identification of peptides from tandem mass spectra is an important part of many high-throughput proteomics pipelines. In the high-throughput setting, the spectra are typically identified using software that matches tandem mass spectra with putative peptides from amino-acid sequence databases. The effectiveness of these search engines depends heavily on the completeness of the amino-acid sequence database used, but suitably complete

Nathan Edwardsand; Ross Lippert

2004-01-01

408

The vibrational spectra and structure of oxaloacetic acid  

NASA Astrophysics Data System (ADS)

The complete vibrational spectra of oxaloacetic acid have been recorded. Infrared spectra were collected at liquid N 2 as well as ambient temperature, while the Raman data were collected at ambient temperature only. A vibrational assignment is proposed based on an enol structure in the solid phase. The previously documented keto—enol tautomerization of oxaloacetic acid in solution was verified by recording infrared spectra of oxaloacetic acid in solvents of different polarities.

Schiering, David W.; Katon, J. E.

1986-04-01

409

An Enlarged Data Base of Electron-Ionization Mass Spectra  

Microsoft Academic Search

The computer-searchable data base of reference mass spectra described earlier has been increased in size by 76%, so that it\\u000a now contains 139,859 different spectra of 118,144 different compounds. The average number of peaks per spectrum is 53. All\\u000a spectra were examined for errors by the Probability Based Matching (PBM) and the Quality Index (QI) algorithms and by human\\u000a inspection.

Fred W. McLafferty; Douglas B. Stauffer; Andrea B. Twiss-Brooks; Stanton Y. Loh

1991-01-01

410

78 FR 35658 - Spectra Energy Corp., Application for a New or Amended Presidential Permit  

Federal Register 2010, 2011, 2012, 2013

...DEPARTMENT OF STATE [Public Notice 8353] Spectra Energy Corp., Application for a New...State. ACTION: Notice of Receipt of Spectra Energy Corp., Application for a New...Department of State (DOS) has received from Spectra Energy Corp (``Spectra...

2013-06-13

411

Comparison of UV synthetic spectra with broadband and spectral irradiances  

NASA Astrophysics Data System (ADS)

Converting discreet narrowband filter radiometer irradiance measurements into continuous allows the construction of weighted doses such as an erythemal and plant action spectra. Synthetic spectra were retrieved from 7 UV narrowband channels using a fast 5 parameter fit. The synthetic spectra are compared with measurements from a collocated spectroradiometer and the erythemally weighted doses from the synthetic spectra are compared with daily erythemal doses from a collocated broadband radiometer. The agreement in spectral data ranges generally from 0.75 to 1.25 depending upon wavelength and solar zenith angle. Agreement between daily erythemal doses are generally between 0.70 and 0.90.

Slusser, James R.; Bigelow, Dennis; Gao, Wei; Scott, Gwendolyn R.; Olson, Becky

2003-11-01

412

Infrared spectra of lunar soil analogs. [spectral reflectance of minerals  

NASA Technical Reports Server (NTRS)

The infrared spectra of analogs of lunar soils were investigated to further the development of methodology for interpretation of remotely measured infrared spectra of the lunar surface. The optical constants of dunite, bytownite, augite, ilmenite, and a mare glass analog were obtained. The infrared emittance spectra of powdered minerals were measured and compared with spectra calculated by the reflectance theory using a catalog of optical constants. The results indicate that the predictions of the theory closely simulate the experimental measurements if the optical constants are properly derived.

Aronson, J. R.

1977-01-01

413

On the spectra and photometry of M-giant stars  

NASA Astrophysics Data System (ADS)

From a sample of 97 very bright M-giant stars in the Solar neighbourhood, high-quality "intrinsic" spectra in the spectral range 380 <~ ?[nm] <~ 900 for all M-spectral subtypes of the Case and MK classification systems are obtained. The results are fitted to photospheric synthetic spectra in the range 99 <~ ? [nm] <=12500 in order to infer the corresponding continua. The synthetic spectra are also compared to the intrinsic spectra. The effective temperatures are derived and mathematical spectral classification criteria are found. The (UB)_j_(VRI)_c_(JHKLM)_ESO_ photometric data of the sample are also given. The data are available on the Strasbourg Astronomical Data Centre (CDS).

Fluks, M. A.; Plez, B.; The, P. S.; de Winter, D.; Westerlund, B. E.; Steenman, H. C.

1994-06-01

414

Ultrahigh-energy cosmic rays particle spectra from crypton decays  

NASA Astrophysics Data System (ADS)

We calculate the spectra of ultrahigh-energy cosmic rays (UHECRs) in an explicit top-down model based on the decays of metastable neutral “crypton” states in a flipped SU(5) string model. For each of the eight specific 10th-order superpotential operators that might dominate crypton decays, we calculate the spectra of both protons and photons, using a code incorporating supersymmetric evolution of the injected spectra. For all the decay operators, the total UHECR spectra are compatible with the available data. Also, the fractions of photons are compatible with all the published upper limits, but may be detectable in future experiments.

Ellis, John; Mayes, V. E.; Nanopoulos, D. V.

2006-12-01

415

Variations of gamma radiation spectra during precipitations  

NASA Astrophysics Data System (ADS)

In the present paper results of prolonging studies of variations of a natural gamma (X-ray) radiation during precipitations registered at cosmic ray station in Apatity are presented. To the present time in the complex installation realizing monitoring of the near ground radiation, the detector is added on the basis of a scintillation crystal by size Ø150×100 mm. The special procedure of working out of the differential energy spectra obtained on the basis of this detector is designed. Due to this it is found, that increases are produced by an additional flux of radiation with the non-regular descending energy spectrum superimposed on a background radiation, having a power law energy spectrum. The clear upper energy limit of the additional radiation, accompanying with precipitations, is observed. It is 1.8-2.0 MeV. Any spectral lines, which could be produced by radionuclides, are not revealed in all researched gamut. It is concluded that these fluxes are produced by energetic charged particles during their passage through the atmosphere, i.e. Bremsstrahlung generation process. Based on the energy balance, the minimum field strength, which can cause a secondary increase, was performed.

Balabin, Yu V.; Germanenko, A. V.; Gvozdevsky, B. B.; Vashenyuk, E. V.

2013-02-01

416

Cassini UVIS observations of Titan nightglow spectra  

NASA Astrophysics Data System (ADS)

In this paper we present the first nightside EUV and FUV airglow limb spectra of Titan showing molecular emissions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed photon emissions of Titan's day and night limb-airglow and disk-airglow on multiple occasions, including during an eclipse observation. The 71 airglow observations analyzed in this paper show EUV (600-1150 Å) and FUV (1150-1900 Å) atomic multiplet lines and band emissions arising from either photoelectron induced fluorescence and solar photo-fragmentation of molecular nitrogen (N2) or excitation by magnetosphere plasma. The altitude of the peak UV emissions on the limb during daylight occurred inside the thermosphere at the altitude of the topside ionosphere (near 1000 km altitude). However, at night on the limb, a subset of emission features, much weaker in intensity, arise in the atmosphere with two different geometries. First, there is a twilight photoelectron-excited glow that persists with solar depression angle up to 25-30 degrees past the terminator, until the solar XUV shadow height passes the altitude of the topside ionosphere (1000-1200 km). The UV twilight glow spectrum is similar to the dayglow but weaker in intensity. Second, beyond 120° solar zenith angle, when the upper atmosphere of Titan is in total XUV darkness, there is indication of weak and sporadic nightside UV airglow emissions excited by magnetosphere plasma collisions with ambient thermosphere gas, with similar N2 excited features as above in the daylight or twilight glow over an extended altitude range.

Ajello, Joseph M.; West, Robert A.; Gustin, Jacques; Larsen, Kristopher; Stewart, A. Ian F.; Esposito, Larry W.; McClintock, William E.; Holsclaw, Gregory M.; Bradley, E. Todd

2012-12-01

417

Understanding Vibrational Spectra of Silicon Nanocrystals  

NASA Astrophysics Data System (ADS)

After the discovery of light emission from porous Si, nanostructured Si became a promising material for opto-electronic applications. For two decades lots of both experimental and theoretical works done in order to understand mechanisms behind the interaction of light with low dimensional forms of Si. In this work we employed MD simulation technique. The simulation details are similar to our earlier work except we used Large Scale Atomistic Molecular Modeling Package Software (LAMMPS) with ReaxFF package as an integrator. We used constant pressure constant temperature (NPT) ensemble with a simulation box size around 4.2 nm. We inserted silicon nanocrystals into amorphous silicon dioxide matrix with diameter ranging from 2 nm to 3.2 nm using a scheme defined in our previous work7. We also simulated free standing hydrogen passivated nanocrystals with same diameters to compare effects of oxide matrix on the nanocrystals. The effect of strain on vibrational spectra of Silicon Nanocrystals is studied as a function of nanocrystal diameter using reactive molecular dynamics simulations technique for both embedded and hydrogen passivated nanocrystals. With use of refined parameters our calculations reproduce the redshift of the Raman active transverse optical peak of Si-Si vibrations with decreasing the nanocrystal size.

Yilmaz, Dundar; Sevik, Cem; Bulutay, Ceyhun; Cagin, Tahir

2011-03-01

418

Resonance spectra of caged black holes  

E-print Network

Recent numerical studies of the coupled Einstein-Klein-Gordon system in a cavity have provided compelling evidence that {\\it confined} scalar fields generically collapse to form black holes. Motivated by this intriguing discovery, we here use analytical tools in order to study the characteristic resonance spectra of the confined fields. These discrete resonant frequencies are expected to dominate the late-time dynamics of the coupled black-hole-field-cage system. We consider caged Reissner-Nordstr\\"om black holes whose confining mirrors are placed in the near-horizon region $x_{\\text{m}}\\equiv (r_{\\text{m}}-r_+)/r_+\\ll\\tau\\equiv (r_+-r_-)/r_+$ (here $r_{\\text{m}}$ is the radius of the confining mirror and $r_{\\pm}$ are the radii of the black-hole horizons). We obtain a simple analytical expression for the fundamental quasinormal resonances of the coupled black-hole-field-cage system: $\\omega_n=-i2\\pi T_{\\text{BH}}\\cdot n[1+O(x^n_{\\text{m}}/\\tau^n)]$, where $T_{\\text{BH}}$ is the temperature of the caged black...

Hod, Shahar

2014-01-01

419

Spectra of nonlocally bound quantum systems  

NASA Astrophysics Data System (ADS)

We discuss a class of nonlinear and nonlocal models for the dynamics of a composite quantum system. The models in question depend on the following constituents: on two subsystem Hamiltonians (denoted by H and ?), an analytic function ( f), and a real parameter ( s). As demonstrated elsewhere before, the stationary states can be described in these models fairly explicitly. In this article, we build upon that result, and discuss the topological as well as statistical characteristics of the spectra. Here, we concentrate on the special case f = log. It turns out that an energy spectrum of the nonlocally bound system substantially differs from that of its components. Indeed, we show rigorously that, if H is the harmonic oscillator and ? is completely degenerate with one energy level, then the energy spectrum of the composite system has the topology of the Cantor set (for s > 2). In addition, we show that, if H is replaced by the logarithm of the harmonic oscillator, then the spectrum consists of finitely many intervals separated by gaps (for s sufficiently large). In the last case, the key analytic object is the series ? n - s . In particular, as an interesting offshoot, this structure furnishes a nontautological immersion of fundamental number-theoretic functions into the quantum formalism.

Sowa, A.

2011-06-01

420

Optical spectra of high temperature superconductors  

SciTech Connect

The concept of free electrons which yields the Drude description of the conductivity works surprisingly well in conventional metals. By contrast, the infrared reflectivity of the cuprate superconductors deviates dramatically from Drude behavior and thus challenges theory to explain the origin of the anomalous electron damping and the related mass divergence which has implications for the existence of a Fermi surface. The controversial key issue of the carrier concentration in cuprates needs to be resolved by a conserving analysis of the puzzling conductivity. Raman spectra of cuprates also exhibit unconventional electronic contributions over a wide frequency range up to 1 eV, and recent data provide evidence for the symmetry of the superconducting energy gap. A microscopic theory for both the optical conductivity and the Raman anomalies in cuprates derives a linear frequency variation of the damping from electron-electron collisions on a nested Fermi surface that refers to nearly parallel segments of an electron trajectory. Thus the nesting theory links the cuprate anomalies to phenomena in chromium and rare earth metals. Nesting also yields a novel mechanism for d-wave superconductivity that requires a Coulomb repulsion of intermediate strength and key nesting features that distinguish high {Tc} cuprates from other materials. 41 refs., 7 figs.

Ruvalds, J. [Univ. of Virginia, Charlottesville, VA (United States). Physics Dept.

1996-12-31

421

Correlating features in the primordial spectra  

NASA Astrophysics Data System (ADS)

Heavy fields coupled to the inflaton reduce the speed of sound in the effective theory of the adiabatic mode each time the background inflationary trajectory deviates from a geodesic. This can result in features in the primordial spectra. We compute the corresponding bispectrum and show that if a varying speed of sound induces features in the power spectrum, the change in the bispectrum is given by a simple formula involving the change in the power spectrum and its derivatives. In this manner, we provide a uniquely discriminable signature of a varying sound speed for the adiabatic mode during inflation that indicates the influence of heavy fields. We find that features in the bispectrum peak in the equilateral limit and, in particular, in the squeezed limit we find considerable enhancement entirely consistent with the single field consistency relation. From the perspective of the underlying effective theory, our results generalize to a wide variety of inflationary models where features are sourced by the time variation of background quantities. A positive detection of such correlated features would be unambiguous proof of the inflaton’s nature as a single light scalar degree of freedom embedded in a theory that is UV completable.

Achúcarro, Ana; Gong, Jinn-Ouk; Palma, Gonzalo A.; Patil, Subodh P.

2013-06-01

422

The ultraviolet spectra of nearby radio galaxies  

NASA Technical Reports Server (NTRS)

New and archival IUE SWP spectra are reported for nine nearby radio galaxies (V is less than 15 mag), together with optical emissionlike data for these galaxies as well as a number of candidates with weaker line emission. Both their UV line and continuum properties, as well as their UV and UV-optical line ratios, are examined. Ly-alpha emission is found to be common among local radio galaxies, at modest luminosities (typically 10 exp 41-42 erg/s). No apparent relation is found between L(Ly-alpha) and radio power for the nearby radio galaxies alone. The Ly-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 times lower than the prediction for case B recombination. The destruction of Ly-alpha photons by grains during resonant scattering can explain the observed deficiency for reasonable metallicities. The nearby radio galaxies have in general a small C IV/Ly-alpha ratio (less than 0.1). Comparison of the C IV and Ly-alpha strengths with those in luminous AGN suggests that most of the UV continuum comes from the stellar population, and not from the AGN.

Keel, William C.; Windhorst, Rogier A.

1991-01-01

423

Extracting Quantitative Data from Lunar Soil Spectra  

NASA Technical Reports Server (NTRS)

Using the modified Gaussian model (MGM) developed by Sunshine et al. [1] we compared the spectral properties of the Lunar Soil Characterization Consortium (LSCC) suite of lunar soils [2,3] with their petrologic and chemical compositions to obtain quantitative data. Our initial work on Apollo 17 soils [4] suggested that useful compositional data could be elicited from high quality soil spectra. We are now able to expand upon those results with the full suite of LSCC soils that allows us to explore a much wider range of compositions and maturity states. The model is shown to be sensitive to pyroxene abundance and can evaluate the relative portion of high-Ca and low-Ca pyroxenes in the soils. In addition, the dataset has provided unexpected insights into the nature and causes of absorption bands in lunar soils. For example, it was found that two distinct absorption bands are required in the 1.2 m region of the spectrum. Neither of these bands can be attributed to plagioclase or agglutinates, but both appear to be largely due to pyroxene.

Noble, S. K.; Pieters, C. M.; Hiroi, T.

2005-01-01

424

Estimating Shock Spectra: Extensions beyond GEVS  

NASA Technical Reports Server (NTRS)

Shock response spectra (SRS) are the standard description of some vibration environments on spacecraft for equipment qualification. For shock events produced by pyrotechnic devices, SRS can have significant frequency content as high as 10 kHz. It is difficult to construct and analyze finite element models that can resolve dynamic behavior at such high frequencies. GEVS provides simple, empirically based methods for approximating the SRS for a wide variety of shock events. It begins with a base SRS according to the type of pyrotechnic device, and then provides attenuation relations to adjust this SRS according to distance from the shock source, the type of structural frame and the properties of any structural joints between the source and equipment. In our paper we extend GEVS to include more detailed information about the spacecraft structure. To retain the general framework of GEVS, we begin with a base SRS and adjust this SRS using attenuation relations. We use modal and traveling wave concepts to derive the attenuation relations for simple canonical structures. Then we show how these concepts can be used to analyze more complex structures using finite element mode shapes to explicitly calculate the attenuation factors. Since the low- to mid-frequency finite element modal information is extrapolated to obtain the low- to high-frequency attenuation relations, the resulting attenuated SRS is formulated as an upper bound rather than as mean predicted values. We illustrate the extended GEVS approach by analyzing the impact response of composite tubes and the shock response of the STEREO spacecraft.

Igusa, Takeru; Maahs, Gordon L.

2008-01-01

425

AIS spectra of desert shrub canopies  

NASA Technical Reports Server (NTRS)

Airborne Imaging Spectrometer (AIS) data were collected 30 August 1985 from a desert shrub community in central Oregon. Spectra from artificial targets placed on the test site and from bare soil, big sagebrush (Artemesia tridentata wyomingensis), silver sagebrush (Artemesia cana bolander), and exposed volcanic rocks were studied. Spectral data from grating position 3 (tree mode) were selected from 25 ground positions for analysis by Principal Factor Analysis (PFA). In this grating position, as many as six factors were identified as significant in contributing to spectral structure. Channels 74 through 84 (tree mode) best characterized between-class differences. Other channels were identified as nondiscriminating and as associated with such errors as excessive atmospheric absorption and grating positin changes. The test site was relatively simple with the two species (A. tridentata and A. cana) representing nearly 95% of biomass and with only two mineral backgrounds, a montmorillonitic soil and volcanic rocks. If, as in this study, six factors of spectral structure can be extracted from a single grating position from data acquired over a simple vegetation community, then AIS data must be considered rich in information-gathering potential.

Murray, R.; Isaacson, D. L.; Schrumpf, B. J.; Ripple, W. J.; Lewis, A. J.

1986-01-01

426

Synthetic infrared spectra for correlation spectroscopy  

SciTech Connect

As a first step toward the development of a new remote sensing technique that the authors call holographic correlation spectroscopy, they demonstrate that diffractive optics can be used to synthesize the infrared spectra of real compounds. In particular, they have designed, fabricated, and characterized a diffractive element that successfully reproduces the major features f the spectrum of gaseous HF in the region between 3,600 cm{sup {minus}1} and 4,300 cm{sup {minus}1}. The reflection-mode diffractive optic consists of 4,096 lines, each 4.5 {micro}m wide, at 16 discrete depths relative to the substrate (from 0 to 1.2 {micro}m), and was fabricated on a silicon wafer using anisotropic reactive ion-beam etching in a four-mask-level process. The authors envision the use of diffractive elements of this type to replace the cumbersome reference cells of conventional correlation spectroscopy and thereby enable a new class of compact and versatile correlation spectrometers.

Sinclair, M.B.; Butler, M.A.; Ricco, A.J.; Kravitz, S.H.; Zubrzycki, W.J.; Warren, M.E.

1997-12-01

427

Spectra as windows into exoplanet atmospheres  

PubMed Central

Understanding a planet’s atmosphere is a necessary condition for understanding not only the planet itself, but also its formation, structure, evolution, and habitability. This requirement puts a premium on obtaining spectra and developing credible interpretative tools with which to retrieve vital planetary information. However, for exoplanets, these twin goals are far from being realized. In this paper, I provide a personal perspective on exoplanet theory and remote sensing via photometry and low-resolution spectroscopy. Although not a review in any sense, this paper highlights the limitations in our knowledge of compositions, thermal profiles, and the effects of stellar irradiation, focusing on, but not restricted to, transiting giant planets. I suggest that the true function of the recent past of exoplanet atmospheric research has been not to constrain planet properties for all time, but to train a new generation of scientists who, by rapid trial and error, are fast establishing a solid future foundation for a robust science of exoplanets. PMID:24613929

Burrows, Adam S.

2014-01-01

428

Inflationary power spectra with quantum holonomy corrections  

NASA Astrophysics Data System (ADS)

In this paper we study slow-roll inflation with holonomy corrections from loop quantum cosmology. It was previously shown that, in the Planck epoch, these corrections lead to such effects as singularity avoidance, metric signature change and a state of silence. Here, we consider holonomy corrections affecting the phase of cosmic inflation, which takes place away from the Planck epoch. Both tensor and scalar power spectra of primordial inflationary perturbations are computed up to the first order in slow-roll parameters and V/?c, where V is a potential of the scalar field and ?c is a critical energy density (expected to be of the order of the Planck energy density). Possible normalizations of modes at short scales are discussed. In case the normalization is performed with use of the Wronskian condition applied to adiabatic vacuum, the tensor and scalar spectral indices are not quantum corrected in the leading order. However, by choosing an alternative method of normalization one can obtain quantum corrections in the leading order. Furthermore, we show that the holonomy-corrected equations of motion for tensor and scalar modes can be derived based on effective background metrics. This allows us to show that the classical Wronskian normalization condition is well defined for the cosmological perturbations with holonomy corrections.

Mielczarek, Jakub

2014-03-01

429

Delayed Neutron Energy Spectra Following Fast Fission of Uranium  

NASA Astrophysics Data System (ADS)

Delayed neutron energy spectra have been measured for six delay-time intervals following the fast fission of ^{238}U nuclei. The delay-time intervals span the range 0.17 to 10.2 seconds following initial fission while the measured spectra span neutron energies from 10 keV to 4 MeV. The experiment was performed utilizing the UMass/Lowell 5.5 MV Van de Graaff accelerator to produce fast neutrons for inducing fission in a ^{238} U lined fission chamber. The fission fragments were flushed via a helium jet stream to a well-shielded counting room where they were deposited onto a moving tape (magnetic audio tape) and transferred to a beta-neutron time-of-flight spectrometer. By adjusting the tape speed, composite delayed neutron time-of-flight spectra were measured for several different delay-time intervals. These measurements involved beta-neutron coincidences with ^6 Li-loaded glass scintillators for neutron energies from 10 keV to 450 keV and Bicron BC 501 liquid scintillators for the neutron energy range 200 keV-4 MeV. The measured composite delayed neutron energy spectra for ^{238}U are compared to the composite spectra for ^ {235}U and ^{239} Pu, and also to composite spectra derived for ^{238}U from the ENDF/B-VI database, which is based on summation calculations of individual precursor data supplemented by theoretical estimates. The composite spectra of ^{235}U and ^{239}Pu were obtained from previous measurements of delayed neutron spectra at this laboratory. The composite spectra are also decomposed into Keepin six-group spectra and compared with those for ^{239}Pu and ^{235}U. In addition, an equilibrium spectrum has been calculated from the measured composite spectra using several different analytical techniques and is also compared with the equilibrium spectrum of ^{238}U measured in an earlier study at this laboratory.

Villani, Marcel Franklin

430

Fluorescence emission spectra of calcofluor stained yeast cell suspensions: heuristic assessment of basis spectra for their linear unmixing.  

PubMed

Fluorescence emission spectra of yeast cell suspensions stained with calcofluor have recently been identified as promising markers of variations in the quality of yeast cell wall. It is shown in this paper how the raw fluorescence spectra of calcofluor can be transformed to reliable spectral signatures of cell wall quality, which are independent of actual dye-to-cell concentrations of examined cell suspensions. Moreover, the presented approach makes it possible to assess basis fluorescence spectra that allows for the spectral unmixing of raw fluorescence spectra in terms of respective fluorescence contributions of calcofluor solvated in the suspension medium and bound to yeast cell walls. PMID:22538834

Plášek, Jaromír; Dostál, Marek; Gášková, Dana

2012-07-01

431

Near infrared spectra of the Orion bar  

NASA Astrophysics Data System (ADS)

We have used the LONGSP spectrometer on the 1.5-m TIRGO telescope to obtain long slit spectra in the J, H, and K wavelength bands towards two positions along the Orion bar. These data have been supplemented with images made using the ARNICA camera mounted on TIRGO as well as with an ESO NTT observation carried out by Dr A. Moorwood. We detect a variety of transitions of hydrogen, helium, OI, FeII, FeIII, and H_2. From our molecular hydrogen data, we conclude that densities are moderate (3-6x 10(4) cm(-3) ) in the layer responsible for the molecular hydrogen emission and give no evidence for the presence of dense neutral clumps. We also find that the molecular hydrogen bar is likely to be tilted by ~ 10 degrees relative to the line of sight. We discuss the relative merits of several models of the structure of the bar and conclude that it may be split into two structures separated by 0.2-0.3 parsec along the line of sight. It also seems likely to us that in both structures, density increases along a line perpendicular to the ionization front which penetrates into the neutral gas. We have used the 1.317mum OI line to estimate the FUV radiation field incident at the ionization front and find values of 1-3x 10(4) greater than the average interstellar field. From [FeII] line measurements, we conclude that the electron density in the ionized layer associated with the ionization front is of order 10(4) \\percc. Finally, our analysis of the helium and hydrogen recombination lines implies essential coincidence of the helium and hydrogen Stromgren spheres.

Marconi, A.; Testi, L.; Natta, A.; Walmsley, C. M.

1998-02-01

432

Fast multidimensional NMR spectroscopy for sparse spectra.  

PubMed

Multidimensional NMR spectroscopy is widely used for studies of molecular and biomolecular structure. A major disadvantage of multidimensional NMR is the long acquisition time which, regardless of sensitivity considerations, may be needed to obtain the final multidimensional frequency domain coefficients. In this article, a method for under-sampling multidimensional NMR acquisition of sparse spectra is presented. The approach is presented in the case of two-dimensional NMR acquisitions. It relies on prior knowledge about the support in the two-dimensional frequency domain to recover an over-determined system from the under-determined system induced in the linear acquisition model when under-sampled acquisitions are performed. This over-determined system can then be solved with linear least squares. The prior knowledge is obtained efficiently at a low cost from the one-dimensional NMR acquisition, which is generally acquired as a first step in multidimensional NMR. If this one-dimensional acquisition is intrinsically sparse, it is possible to reconstruct the corresponding two-dimensional acquisition from far fewer observations than those imposed by the Nyquist criterion, and subsequently to reduce the acquisition time. Further improvements are obtained by optimizing the sampling procedure for the least-squares reconstruction using the sequential backward selection algorithm. Theoretical and experimental results are given in the case of a traditional acquisition scheme, which demonstrate reliable and fast reconstructions with acceleration factors in the range 3-6. The proposed method outperforms the CS methods (OMP, L1) in terms of the reconstruction performance, implementation and computation time. The approach can be easily extended to higher dimensions and spectroscopic imaging. PMID:24664959

Merhej, Dany; Ratiney, Hélène; Diab, Chaouki; Khalil, Mohamad; Sdika, Michaël; Prost, Rémy

2014-06-01

433

Infrared Extinction Spectra of Mineral Dust Aerosol  

NASA Astrophysics Data System (ADS)

Mineral dust aerosol affects the atmosphere by absorbing and scattering radiation and plays an important role in the Earth's radiative budget. The effect of atmospheric dust on climate is studied by various remote sensing techniques that use measurements from narrow band IR channels of satellites to determine key atmospheric properties. Therefore, it is essential to take radiative effects of mineral dust aerosol into account to correctly process remote sensing data. As aerosols are transported through the atmosphere they undergo aging and heterogeneous chemistry. This leads to changes in their optical properties and their effects on climate. In this study we carried out spectral simulations using both Mie theory and solutions derived in the Rayleigh regime for authentic dust samples and several processed components of mineral dust. Simulations of the extinction based on Mie theory shows that it does not accurately reproduce the peak position and band shape of the prominent IR resonance features. Errors in the simulated peak position and the line shape associated with Mie theory can adversely affect determination of mineral composition based on IR satellite data. Analytic solutions for various shapes derived from Rayleigh theory offer a better fit to the major band features of the spectra, therefore the accuracy of modeling atmospheric dust properties can be improved by using these analytic solutions. It is also important to take aging of mineral dust into account. We investigated the effect of chemical processing on the optical properties. It was shown that interactions of components of mineral dust (calcite, quartz and kaolinite) with humic and organic acids cause a shift of the IR resonance bands of these minerals. It may indicate changes in shape of the particles as well as changes in hygroscopicity and, as the result, the water content in these samples. Therefore, care should be taken when modeling optical properties of aged mineral dust.

Kleiber, P.; Laskina, O.; Alexander, J. M.; Young, M.; Grassian, V. H.

2012-12-01

434

Hardness ratios of different neutron spectra.  

PubMed

Extensive data have been gathered in the past on the response of different detectors, based on the registration of neutron-induced fissions in bismuth, gold, tantalum and thorium by the spark-replica counter and the thin film breakdown counter. These detectors make it possible to exploit the excellent characteristics of the fission reactions for the measurements of high-energy neutrons. Most of the investigations have been carried out at the quasi-monoenergetic neutron beam facility at The Svedberg Laboratory-TSL of the Uppsala University in cooperation with the Khlopin Radium Institute (KRI). The responses of different fission detectors in the neutron energy range 35-180 MeV have been evaluated: a region where the predictive power of available nuclear reaction models and codes is not reliable yet. For neutron energy >200 MeV, the fission-detector responses have been derived from the data of the proton fission cross sections. By using the ratio of the responses of these detectors, a simple and accurate way to evaluate the spectrum hardness can be obtained, thus providing a tool to obtain spectral information needed for neutron dosimetry without the need to know the entire spectrum. Extensive data have been already obtained for the high-energy neutron spectrum from the CERN concrete facility. In the present paper, the measured values of the response ratios for different fissile detectors exposed at the CERN facility are compared with those calculated for the spectra from the same facility and from different altitudes in the atmosphere, respectively. PMID:15353650

Tommasino, L; Tripathy, S P

2004-01-01

435

Comparison of IMP and orbital spectra  

NASA Astrophysics Data System (ADS)

Visible and near-infrared spectra from the Imager for Mars Pathfinder (IMP) camera have been used to characterize the color and infer the composition and physical nature of the Pathfinder landing site. The range of colors and albedos of materials at the Pathfinder landing site is similar to that observed in Viking Orbiter and HST images of Mars, but precise comparisons are hampered by the effects of atmospheric scattering in these data sets and differences in the effective wavelengths of the images. Such comparisons will allow the spectral units observed at the Pathfinder landing site to be placed into a global geologic context, and the composition, physical properties, and origins of Martian surface units to be inferred. We will report on our progress toward achieving these objectives by calibrating, modeling, and analyzing IMP multispectral observations of various surface materials and comparing them to the color and albedo units observed by the Viking Orbiter cameras, the WF/PC2 on HST, and the MOC wide-angle cameras on MGS. Improved spectral reflectance measurements of rock and soil units at the Pathfinder site are available for the Superpan and photometric equator datasets as a result of more precise IMP calibration algorithms and improved automated spatial registration and mosaicking tools developed in the USGS ISIS environment. A method for ingesting and processing WF/PC2 images into ISIS is being developed. Analyses of these data sets will help to determine the relative importance and timing of geologic processes that have affected the Pathfinder landing site, and therefore constrain the geologic history of the site. The relationships between various spectral units, as observed at the Pathfinder landing site, may be extrapolated to infer the stratigraphic relations between these units regionally and perhaps globally. This research is supported by the NASA Mars Data Analysis Program.

Herkenhoff, K. E.; Johnson, J. R.; Lemmon, M.; Reid, R.; Smith, P. H.

2000-10-01

436

Mutation spectra of complex environmental mixtures  

SciTech Connect

Bioassay-directed chemical analysis of complex environmental mixtures has indicated that much of the genotoxic activity of mixtures is due to the presence of one or a few classes or chemicals within the mixture. We have extended this observation to the molecular level by using colony probe hybridization and PCR/DNA sequence analysis to determine the mutation spectra of {approximately}8,000 revertants induced by a variety of complex mixtures and their chemical fractions in TA100 and TA98 of Salmonella. For urban air, >80% of mutagenic activity was due to a base/neutral fraction that contained primarily PAHs. The mutation spectrum induced by unfractionated urban air was not significantly different from that produced by a model PAH, B(a)P. The mutation spectrum induced by organic extracts of chlorinated drinking water were similar to those produced by the chlorinated furanone MX, which accounted for {approximately}20% of the mutagenic activity of the samples. The base/neutral fraction of municipal waste incinerator emissions accounted for the primary class of mutations induced by the emissions, and a polar neutral fraction accounted for the secondary class of mutations induced by the emissions. The primary class of mutations induced by cigarette smoke condensate in TA100 (GC {yields} TA) is also the primary class of mutations in the p53 gene of lung tumors of cigarette smokers. These results confirm at the molecular level that the mutations induced by a complex mixture reflect the dominance of one or a few classes of chemicals within the mixture.

DeMarini, D.M. [EPA, Research Triangle Park, NC (United States)

1997-10-01

437

HOT ELECTROMAGNETIC OUTFLOWS. I. ACCELERATION AND SPECTRA  

SciTech Connect

The theory of cold, relativistic, magnetohydrodynamic outflows is generalized by the inclusion of an intense radiation source. In some contexts, such as the breakout of a gamma-ray burst (GRB) jet from