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1

STABLE AND TRANSPORTABLE REGIONAL MAGNITUDES BASED ON CODA-DERIVED MOMENT-RATE SPECTRA  

Microsoft Academic Search

We describe an empirical method of calibrating stable seismic source moment-rate spectra derived from regional coda envelopes using broadband stations. The main goal is to develop a regional magnitude methodology that has the following properties: 1) it is tied to an absolute scale and is thus unbiased and transportable; 2) it can be tied seamlessly to the well-established teleseismic and

Kevin Mayeda; Abraham Hofstetter; Jennifer L. O'Boyle; Niyazi Turkelli; William R. Walter

2002-01-01

2

Separating the Wheat from the Chaff: Unbiased Filtering of Background Tandem Mass Spectra Improves Protein Identification  

PubMed Central

Only a small fraction of spectra acquired in LC-MS/MS runs matches peptides from target proteins upon database searches. The remaining, operationally termed background, spectra originate from a variety of poorly controlled sources and affect the throughput and confidence of database searches. Here, we report an algorithm and its software implementation that rapidly removes background spectra, regardless of their precise origin. The method estimates the dissimilarity distance between screened MS/MS spectra and unannotated spectra from a partially redundant background library compiled from several control and blank runs. Filtering MS/MS queries enhanced the protein identification capacity when searches lacked spectrum to sequence matching specificity. In sequence-similarity searches it reduced by, on average, 30-fold the number of orphan hits, which were not explicitly related to background protein contaminants and required manual validation. Removing high quality background MS/MS spectra, while preserving in the data set the genuine spectra from target proteins, decreased the false positive rate of stringent database searches and improved the identification of low-abundance proteins.

Junqueira, Magno; Spirin, Victor; Balbuena, Tiago Santana; Waridel, Patrice; Surendranath, Vineeth; Kryukov, Grigoriy; Adzhubei, Ivan; Thomas, Henrik; Sunyaev, Shamil; Shevchenko, Andrej

2009-01-01

3

Constructions of Mutually Unbiased Bases  

Microsoft Academic Search

Two orthonormal bases B and Bof a d-dimensional complex inner-product space are called mutually unbiased if and only if |h b|bi| 2 = 1\\/d holds for all b ? B and b' ? B'. The size of any set containing pairwise mutually unbiased bases of Cd cannot exceed d + 1. If d is a power of a prime, then

Andreas Klappenecker; Martin Roetteler

2003-01-01

4

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

5

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

6

Unbiased stratification of left ventricles.  

PubMed

Image based quantitative stratification of the Left Ventricles (LV) across a population helps in unraveling the structure-function symbiosis of the heart. An unbiased, reference less grouping scheme that automatically determines the number of clusters and a physioanatomically relevant strategy that aligns the intra cluster LV shapes would enable the robust construction of pathology stratified cardiac atlas. This paper achieves this hitherto elusive stratification and alignment by adapting the conventional strategies routinely followed by clinicians. The individual LV shape models (N=127) are independently oriented to an "attitudinally consistent orientation" that captures the physioanatomic variations of the LV morphology. Affinity propagation technique based on the automatically identified inter-LV_landmark distances is used to group the LV shapes. The proposed algorithm is computationally efficient and, if the inter cluster variations are linked to pathology, could provide a clinically relevant cardiac atlas. PMID:18979790

Srinivasan, Rajagopalan; Shriram, K S; Suryanarayanan, Srikanth

2008-01-01

7

Seismic moment rate and earthquake mean recurrence interval in the major tectonic boundaries around Oman  

NASA Astrophysics Data System (ADS)

Owing to the short earthquake history, mathematical relationships were developed for calculating the earthquake recurrence from the rate of slip along the active faults. Based on the slip rate and the well-known Gutenberg-Richter law, various relationships between the earthquake occurrence parameters and the crustal deformation rates were developed. Among those is the widely used Molnar (1979 Bull. Seismol. Soc. Am. 69 115-33) mathematical expression, which is modified in the current study to produce a mathematical model based upon the truncated Gutenberg-Richter model instead of the normal Gutenberg-Richter one. The modified model is then tested and applied for the major tectonic boundaries around the Sultanate of Oman. The seismic moment rate is determined and the seismic hazard in terms of recurrence interval is expressed for the investigated regions. The calculated recurrence interval with moment magnitude 8.1 in the Makran zone is found to be 760 years, while for earthquakes with magnitude equal or greater than 5.8 in the Owen fracture zone is 4.904 years in consistency with the observed data. Recurrence intervals resulting from the original Molnar (1979) model and the current modified model were compared and discussed for the Zagros region.

Deif, A.; El-Hussain, I.

2012-12-01

8

A note on optimal vector unbiased predictor  

Microsoft Academic Search

A characterization of optimal vector unbiased predictor is obtained. Some properties of optimal unbiased predictors are established.\\u000a It is shown that simultaneous prediction of future random variables is equivalent to marginal prediction of these random variables.\\u000a Following Kale and Chandrasekar (1983) and Chandrasekar (1984), it is shown that the criteria proposed by ishii (1969) based\\u000a on matrices and the one

B. Chandrasekar; T. Edwin Prabakaran

1994-01-01

9

Mutually unbiased measurements in finite dimensions  

NASA Astrophysics Data System (ADS)

We generalize the concept of mutually unbiased bases (MUB) to measurements which are not necessarily described by rank one projectors. As such, these measurements can be a useful tool to study the long-standing problem of the existence of MUB. We derive their general form, and show that in a finite, d-dimensional Hilbert space, one can construct a complete set of d+1 mutually unbiased measurements. Besides their intrinsic link to MUB, we show that these measurements’ statistics provide complete information about the state of the system. Moreover, they capture the physical essence of unbiasedness, and in particular, they satisfy a non-trivial entropic uncertainty relation similar to d+1 MUB.

Kalev, Amir; Gour, Gilad

2014-05-01

10

On unbiased games on random graphs  

Microsoft Academic Search

We study unbiased Maker-Breaker positional games played on the edges of the random graph G(n;p). As the main result of the paper, we prove a conjecture from (18), that the property that Maker is able to win the Hamiltonicity game played on a random graph G(n;p) has a sharp threshold at log n n . Our theorem can be considered

Dan Hefetz; Michael Krivelevich; Milos Stojakovic; Tibor Szabo

2007-01-01

11

Minimax Unbiased Estimator of Mixing Distribution for Finite Mixtures.  

National Technical Information Service (NTIS)

Let H be the family of finite mixtures of any fixed set of k+1 (distinct) distribution functions. The minimax unbiased estimator of the parameter theta for identifiable families H is derived. An estimator is called minimax unbiased if it is unbiased and i...

D. C. Boes

1967-01-01

12

Nearly unbiased variable selection under minimax concave penalty  

Microsoft Academic Search

We propose MC+, a fast, continuous, nearly unbiased and accurate method of penalized variable selection in high-dimensional linear regression. The LASSO is fast and continuous, but biased. The bias of the LASSO may prevent consistent variable selection. Subset selection is unbiased but computationally costly. The MC+ has two elements: a minimax concave penalty (MCP) and a penalized linear unbiased selection

Cun-Hui Zhang

2010-01-01

13

Mutually unbiased probability-operator measurements  

NASA Astrophysics Data System (ADS)

We generalize the concept of unbiasedness from bases to measurements. We show that mutually unbiased (MU) measurements, which are not necessarily von Neumann measurements, exist in all finite-dimensional Hilbert spaces. We study the geometrical relation between these measurements and symmetric informationally complete measurements. In particular we find that these two kinds of measurements are related to each other as points and lines in finite affine plane geometries. This relation provides a natural way to define discrete phase-space functions based on MU measurements and symmetric informationally complete measurements.

Kalev, Amir

2014-07-01

14

Unbiased sampling of lattice Hamilton path ensembles  

NASA Astrophysics Data System (ADS)

Hamilton paths, or Hamiltonian paths, are walks on a lattice which visit each site exactly once. They have been proposed as models of globular proteins and of compact polymers. A previously published algorithm [Mansfield, Macromolecules 27, 5924 (1994)] for sampling Hamilton paths on simple square and simple cubic lattices is tested for bias and for efficiency. Because the algorithm is a Metropolis Monte Carlo technique obviously satisfying detailed balance, we need only demonstrate ergodicity to ensure unbiased sampling. Two different tests for ergodicity (exact enumeration on small lattices, nonexhaustive enumeration on larger lattices) demonstrate ergodicity unequivocally for small lattices and provide strong support for ergodicity on larger lattices. Two other sampling algorithms [Ramakrishnan et al., J. Chem. Phys. 103, 7592 (1995); Lua et al., Polymer 45, 717 (2004)] are both known to produce biases on both 2×2×2 and 3×3×3 lattices, but it is shown here that the current algorithm gives unbiased sampling on these same lattices. Successive Hamilton paths are strongly correlated, so that many iterations are required between statistically independent samples. Rules for estimating the number of iterations needed to dissipate these correlations are given. However, the iteration time is so fast that the efficiency is still very good except on extremely large lattices. For example, even on lattices of total size 10×10×10 we are able to generate tens of thousands of uncorrelated Hamilton paths per hour of CPU time.

Mansfield, Marc L.

2006-10-01

15

Decision rules for unbiased inventory estimates  

NASA Technical Reports Server (NTRS)

An efficient and accurate procedure for estimating inventories from remote sensing scenes is presented. In place of the conventional and expensive full dimensional Bayes decision rule, a one-dimensional feature extraction and classification technique was employed. It is shown that this efficient decision rule can be used to develop unbiased inventory estimates and that for large sample sizes typical of satellite derived remote sensing scenes, resulting accuracies are comparable or superior to more expensive alternative procedures. Mathematical details of the procedure are provided in the body of the report and in the appendix. Results of a numerical simulation of the technique using statistics obtained from an observed LANDSAT scene are included. The simulation demonstrates the effectiveness of the technique in computing accurate inventory estimates.

Argentiero, P. D.; Koch, D.

1979-01-01

16

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

17

Designing an Advanced Simulator for Unbiased Branches' Prediction  

Microsoft Academic Search

In this paper we continue our work on detecting and predicting unbiased branches. We centered on two directions: first, based on a simple example from Perm - Stanford benchmark, we show that extending context information some of branches in certain contexts became fully biased, thus diminishing the frequency of unbiased branches at benchmark level. Second, we use some state-of-the art

Adrian Florea; Ciprian Radu; Horia Calborean; Adrian Crapciu; Arpad Gellert; Lucian Vintan

18

Information-disturbance theorem for mutually unbiased observables  

SciTech Connect

We derive a 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.

Miyadera, Takayuki [Research Center for Information Security (RCIS), National Institute of Advanced Industrial Science and Technology (AIST), Daibiru building 1102, Sotokanda, Chiyoda-ku, Tokyo, 101-0021 (Japan); Imai, Hideki [Research Center for Information Security (RCIS), National Institute of Advanced Industrial Science and Technology (AIST), Daibiru building 1102, Sotokanda, Chiyoda-ku, Tokyo, 101-0021 (Japan); Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

2006-04-15

19

Mutually unbiased bases and complementary spin 1 observables  

NASA Astrophysics Data System (ADS)

The two observables are incompatible if they cannot be measured simultaneously; however, they become maximally incompatible (complementary) if their eigenstates are mutually unbiased. Only then does the measurement of one observable give no information about the other observable. The spin projection operators onto three mutually orthogonal directions are complementary only for spin 1/2. For higher spin numbers the corresponding eigenstates are no longer unbiased. In this work we examine the properties of spin 1 mutually unbiased bases (MUB) and look for the physical meaning of the corresponding operators. We show that if the computational basis is chosen to be the eigenbasis of the spin projection operator along some direction z, then all the states, which are unbiased to this basis, have to be squeezed. Next, we study the generation and the measurement of MUB states by introducing the Fourier-like transform through spin squeezing. Finally, we try to ascribe some classical interpretation to the operators corresponding to MUB and study what information the observer gains while measuring them. Higher spin numbers are also considered.

Kurzy?ski, Pawe?; Kaszub, Wawrzyniec; Czechlewski, Miko?aj

2010-07-01

20

Best Linear Unbiased Prediction in the Generalized Linear Regression Model  

Microsoft Academic Search

When interdependence of disturbances is present in a regression model, the pattern of sample residuals contains information which is useful in prediction of post-sample drawings. This information, which is often overlooked, is exploited in the best linear unbiased predictor derived here. The gain in efficiency associated with using this predictor instead of the usual expected value estimator may be substantial.

Arthur S. Goldberger

1962-01-01

21

Improved Correspondence for DTI Population Studies Via Unbiased Atlas Building  

Microsoft Academic Search

We present a method for automatically finding correspon- dence in Diusion Tensor Imaging (DTI) from deformable registration to a common atlas. The registration jointly produces an unbiased av- erage DTI atlas along with dieomorphic correspondence between each image. The registration image match metric uses a feature detector for thin fiber structures of white matter, and interpolation and averaging of diusion

Casey Goodlett; Brad Davis; Remi Jean; John H. Gilmore; Guido Gerig

2006-01-01

22

Unbiased Estimates of Variance Components with Bootstrap Procedures  

ERIC Educational Resources Information Center

This article provides general procedures for obtaining unbiased estimates of variance components for any random-model balanced design under any bootstrap sampling plan, with the focus on designs of the type typically used in generalizability theory. The results reported here are particularly helpful when the bootstrap is used to estimate standard…

Brennan, Robert L.

2007-01-01

23

Tree Algorithms for Unbiased Coin Tossing with a Biased Coin  

Microsoft Academic Search

We give new algorithms for simulating a flip of an unbiased coin by flipping a coin of unknown bias. We are interested in efficient algorithms, where the expected number of flips is our measure of efficiency. Other authors have represented algorithms as lattices, but by representing them instead as trees we are able to produce an algorithm more efficient than

Quentin F. Stout; Bette Warren

1984-01-01

24

Unbiased Parameter Estimation by Means of Autocorrelation Functions.  

National Technical Information Service (NTIS)

A method for obtaining on line unbiased parameter estimates of linear systems in the presence of additive uncorrelated noise is described. The method is based on the equation error and is presented in the form of continuous variables. Instead of the conve...

S. J. Merhav E. Gabay

1973-01-01

25

Linear unbiased state estimation for random models with sensor delay  

Microsoft Academic Search

The motivation for the work reported in this paper accrues from the necessity of finding stabilizing control laws for systems with randomly varying distributed delays. It reports the development of full and reduced order linear unbiased estimators for discrete-time stochastic parameter systems and shows how to parametrize the estimator gains to achieve a certain estimation error covariance. Both finite-time and

E. Yaz; A. Ray

1996-01-01

26

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.

Spruyt, Karen; Verleye, Gino; Gozal, David

2010-01-01

27

Nearly Best Linear Unbiased Estimation of the Mean and Standard Deviation of the Logistic Distribution.  

National Technical Information Service (NTIS)

The method of nearly best linear unbiased estimation, which was developed through order statistics, for obtaining unbiased estimators for use in estimating the location and scale parameters of continuous distribution is applied to the logistic distributio...

J. W. Rodgers

1968-01-01

28

Improving Quantum State Estimation with Mutually Unbiased Bases  

NASA Astrophysics Data System (ADS)

When used in quantum state estimation, projections onto mutually unbiased bases have the ability to maximize information extraction per measurement and to minimize redundancy. We present the first experimental demonstration of quantum state tomography of two-qubit polarization states to take advantage of mutually unbiased bases. We demonstrate improved state estimation as compared to standard measurement strategies and discuss how this can be understood from the structure of the measurements we use. We experimentally compared our method to the standard state estimation method for three different states and observe that the infidelity was up to 1.84±0.06 times lower by using our technique than it was by using standard state estimation methods.

Adamson, R. B. A.; Steinberg, A. M.

2010-07-01

29

Unbiased estimators for spatial distribution functions of classical fluids.  

PubMed

We use a statistical-mechanical identity closely related to the familiar virial theorem, to derive unbiased estimators for spatial distribution functions of classical fluids. In particular, we obtain estimators for both the fluid density rho(r) in the vicinity of a fixed solute and the pair correlation g(r) of a homogeneous classical fluid. We illustrate the utility of our estimators with numerical examples, which reveal advantages over traditional histogram-based methods of computing such distributions. PMID:15638649

Adib, Artur B; Jarzynski, Christopher

2005-01-01

30

Morphologically Unbiased Classifier Combination through Graphical PDF Correlation  

Microsoft Academic Search

We reinterpret the morphologically unbiased’ tomographic’ method of multiple classifier combination developed previously by\\u000a the authors as a methodology for graphical PDF correlation. That is, the original procedure for eliminating what are effectively the back-projection artifacts implicit in any linear\\u000a feature-space combination regime is shown to be replicable by a piecewise morphology matching process. Implementing this alternative\\u000a methodology computationally permits

David Windridge; Josef Kittler

2002-01-01

31

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.

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

2011-01-01

32

Conditionally unbiased and near unbiased estimation of the selected treatment mean for multistage drop-the-losers trials  

PubMed Central

The two-stage drop-the-loser design provides a framework for selecting the most promising of K experimental treatments in stage one, in order to test it against a control in a confirmatory analysis at stage two. The multistage drop-the-losers design is both a natural extension of the original two-stage design, and a special case of the more general framework of Stallard & Friede (2008) (Stat. Med. 27, 6209–6227). It may be a useful strategy if deselecting all but the best performing treatment after one interim analysis is thought to pose an unacceptable risk of dropping the truly best treatment. However, estimation has yet to be considered for this design. Building on the work of Cohen & Sackrowitz (1989) (Stat. Prob. Lett. 8, 273–278), we derive unbiased and near-unbiased estimates in the multistage setting. Complications caused by the multistage selection process are shown to hinder a simple identification of the multistage uniform minimum variance conditionally unbiased estimate (UMVCUE); two separate but related estimators are therefore proposed, each containing some of the UMVCUEs theoretical characteristics. For a specific example of a three-stage drop-the-losers trial, we compare their performance against several alternative estimators in terms of bias, mean squared error, confidence interval width and coverage.

Bowden, Jack; Glimm, Ekkehard

2014-01-01

33

Marginal Structural Models: unbiased estimation for longitudinal studies  

Microsoft Academic Search

Introduction  In this article, we introduce Marginal Structural Models, which yield unbiased estimates of causal effects of exposures in\\u000a the presence of time-varying confounding variables that also act as mediators.\\u000a \\u000a \\u000a \\u000a \\u000a Objectives  We describe estimation via inverse probability weighting; estimation may also be accomplished by g-computation (Robins in\\u000a Latent Variable Modeling and Applications to Causality, Springer, New York, pp 69–117, 1997; van der

Erica E. M. MoodieD; D. A. Stephens

2011-01-01

34

Unbiased Estimation of Mutation Rates under Fluctuating Final Counts  

PubMed Central

Estimation methods for mutation rates (or probabilities) in Luria-Delbrück fluctuation analysis usually assume that the final number of cells remains constant from one culture to another. We show that this leads to systematically underestimate the mutation rate. Two levels of information on final numbers are considered: either the coefficient of variation has been independently estimated, or the final number of cells in each culture is known. In both cases, unbiased estimation methods are proposed. Their statistical properties are assessed both theoretically and through Monte-Carlo simulation. As an application, the data from two well known fluctuation analysis studies on Mycobacterium tuberculosis are reexamined.

Ycart, Bernard; Veziris, Nicolas

2014-01-01

35

Unbiased invariant minimum norm estimation in generalized growth curve model  

Microsoft Academic Search

This paper considers the generalized growth curve model Y=?i=1mXiBiZi?+UE subject to R(Xm)?R(Xm-1)???R(X1), where Bi are the matrices of unknown regression coefficients, Xi,Zi and U are known covariate matrices, i=1,2,…,m, and E splits into a number of independently and identically distributed subvectors with mean zero and unknown covariance matrix ?. An unbiased invariant minimum norm quadratic estimator (MINQE(U,I)) of tr(C?) is

Xiaoyong Wu; Guohua Zou; Jianwei Chen

2006-01-01

36

Maximum likelihood: Extracting unbiased information from complex networks  

NASA Astrophysics Data System (ADS)

The choice of free parameters in network models is subjective, since it depends on what topological properties are being monitored. However, we show that the maximum likelihood (ML) principle indicates a unique, statistically rigorous parameter choice, associated with a well-defined topological feature. We then find that, if the ML condition is incompatible with the built-in parameter choice, network models turn out to be intrinsically ill defined or biased. To overcome this problem, we construct a class of safely unbiased models. We also propose an extension of these results that leads to the fascinating possibility to extract, only from topological data, the “hidden variables” underlying network organization, making them “no longer hidden.” We test our method on World Trade Web data, where we recover the empirical gross domestic product using only topological information.

Garlaschelli, Diego; Loffredo, Maria I.

2008-07-01

37

Drug targets: single-cell transcriptomics hastens unbiased discovery  

PubMed Central

Drug discovery in neuro- and psychopharmacology is lagging, and the most commonly mentioned cause is the scarcity of drug targets. Using NextGen ‘Sequencing Based Single-Cell Transcriptomics’ (SBSCT), several hundred different receptors and channels can be identified in individual neurons, and the functional gene product can subsequently be validated. The use of single-cell transcriptome data to reveal the entire receptor repertoire is crucial, as the copy numbers of mRNAs encoding receptors are low and when cells are pooled, dilution of rare mRNAs leads to loss of signal. These overlooked receptors on key neurons often mediate robust effects that may be therapeutically useful. SBSCT also enables the identification of orphan receptors and can provide strong evidence for receptor heterodimers. Here, we compare SBSCT to other single-cell profiling methods. We argue that the unbiased nature of SBSCT makes it a powerful tool for the identification of new drug targets.

Bartfai, Tamas; Buckley, Peter T.; Eberwine, James

2011-01-01

38

Finite-size scaling in unbiased translocation dynamics  

NASA Astrophysics Data System (ADS)

Finite-size scaling arguments naturally lead to the introduction of a coordinate-dependent diffusion coefficient in a Fokker–Planck description of the late-stage dynamics of unbiased polymer translocation through a membrane pore. The solution for the probability density function of the chemical coordinate matches the initial-stage subdiffusive regime and takes into account the equilibrium entropic drive. We find precise scaling relations connecting the subdiffusion exponent to the divergence with the polymer length of the translocation time, and also to the singularity of the probability density function at the absorbing boundaries. Quantitative comparisons with numerical simulation data in d = 2 strongly support the validity of the model and of the predicted scalings.

Brandani, Giovanni; Baldovin, Fulvio; Orlandini, Enzo; Stella, Attilio L.

2014-05-01

39

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

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.

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

Within-subject template estimation for unbiased longitudinal image analysis  

PubMed Central

Longitudinal image analysis has become increasingly important in clinical studies of normal aging and neurodegenerative disorders. Furthermore, there is a growing appreciation of the potential utility of longitudinally acquired structural images and reliable image processing to evaluate disease modifying therapies. Challenges have been related to the variability that is inherent in the available cross-sectional processing tools, to the introduction of bias in longitudinal processing and to potential over-regularization. In this paper we introduce a novel longitudinal image processing framework, based on unbiased, robust, within-subject template creation, for automatic surface reconstruction and segmentation of brain MRI of arbitrarily many time points. We demonstrate that it is essential to treat all input images exactly the same as removing only interpolation asymmetries is not sufficient to remove processing bias. We successfully reduce variability and avoid over-regularization by initializing the processing in each time point with common information from the subject template. The presented results show a significant increase in precision and discrimination power while preserving the ability to detect large anatomical deviations; as such they hold great potential in clinical applications, e.g. allowing for smaller sample sizes or shorter trials to establish disease specific biomarkers or to quantify drug effects.

Reuter, Martin; Schmansky, Nicholas J.; Rosas, H. Diana; Fischl, Bruce

2012-01-01

42

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

43

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

44

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

45

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

46

Quantitative and unbiased analysis of directional persistence in cell migration.  

PubMed

The mechanism by which cells control directional persistence during migration is a major question. However, the common index measuring directional persistence, namely the ratio of displacement to trajectory length, is biased, particularly by cell speed. An unbiased method is to calculate direction autocorrelation as a function of time. This function depends only on the angles of the vectors tangent to the trajectory. This method has not been widely used, because it is more difficult to compute. Here we discuss biases of the classical index and introduce a custom-made open-source computer program, DiPer, which calculates direction autocorrelation. In addition, DiPer also plots and calculates other essential parameters to analyze cell migration in two dimensions: it displays cell trajectories individually and collectively, and it calculates average speed and mean square displacements (MSDs) to assess the area explored by cells over time. This user-friendly program is executable through Microsoft Excel, and it generates plots of publication-level quality. The protocol takes ?15 min to complete. We have recently used DiPer to analyze cell migration of three different mammalian cell types in 2D cultures: the mammary carcinoma cell line MDA-MB-231, the motile amoeba Dictyostelium discoideum and fish-scale keratocytes. DiPer can potentially be used not only for random migration in 2D but also for directed migration and for migration in 3D (direction autocorrelation only). Moreover, it can be used for any types of tracked particles: cellular organelles, bacteria and whole organisms. PMID:25033209

Gorelik, Roman; Gautreau, Alexis

2014-08-01

47

UNBIASED INCLINATION DISTRIBUTIONS FOR OBJECTS IN THE KUIPER BELT  

SciTech Connect

Using data from the Deep Ecliptic Survey (DES), we investigate the inclination distributions of objects in the Kuiper Belt. We present a derivation for observational bias removal and use this procedure to generate unbiased inclination distributions for Kuiper Belt objects (KBOs) of different DES dynamical classes, with respect to the Kuiper Belt plane. Consistent with previous results, we find that the inclination distribution for all DES KBOs is well fit by the sum of two Gaussians, or a Gaussian plus a generalized Lorentzian, multiplied by sin i. Approximately 80% of KBOs are in the high-inclination grouping. We find that Classical object inclinations are well fit by sin i multiplied by the sum of two Gaussians, with roughly even distribution between Gaussians of widths 2.0{sup +0.6}{sub -0.5}{sup 0} and 8.1{sup +2.6}{sub -2.1}{sup 0}. Objects in different resonances exhibit different inclination distributions. The inclinations of Scattered objects are best matched by sin i multiplied by a single Gaussian that is centered at 19.1{sup +3.9}{sub -3.6}{sup 0} with a width of 6.9{sup +4.1}{sub -2.7}{sup 0}. Centaur inclinations peak just below 20{sup 0}, with one exceptionally high-inclination object near 80{sup 0}. The currently observed inclination distribution of the Centaurs is not dissimilar to that of the Scattered Extended KBOs and Jupiter-family comets, but is significantly different from the Classical and Resonant KBOs. While the sample sizes of some dynamical classes are still small, these results should begin to serve as a critical diagnostic for models of solar system evolution.

Gulbis, A. A. S. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 Cape Town (South Africa); Elliot, J. L.; Adams, E. R. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 (United States); Benecchi, S. D. [Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719 (United States); Buie, M. W. [Department of Space Studies, Southwest Research Institute, 1050 Walnut Street 400, Boulder, CO 80302 (United States); Trilling, D. E. [Department of Physics and Astronomy, Northern Arizona University, P.O. Box 6010, Flagstaff, AZ 86011 (United States); Wasserman, L. H., E-mail: amanda@saao.ac.z, E-mail: jle@mit.ed, E-mail: era@mit.ed, E-mail: lhw@lowell.ed, E-mail: susank@psi.ed, E-mail: buie@boulder.swri.ed, E-mail: David.Trilling@nau.ed [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States)

2010-08-15

48

Mutually unbiased bases, Heisenberg-Weyl orbits and the distance between them  

NASA Astrophysics Data System (ADS)

There is a famous construction of mutually unbiased bases in prime dimensions that uses the eigenbases of cyclic subgroups of the Heisenberg-Weyl group. Less well-known, perhaps, is that orbits under the same group also form sets of mutually unbiased bases. Regarded as points in a Grassmannian space, we find that the individual bases from different sets of mutually unbiased bases lie at regular, repeating distances from one another and we conjecture an analytical expression for these distances based on their status as 2-designs.

Blanchfield, Kate

2012-12-01

49

The Meta-Analysis Effect Size Calculator: A Basic Program for Reconstructing Unbiased Effect Sizes  

Microsoft Academic Search

The Meta-Analysis Effect Size Calculator provides the user with many different ways to calculate an effect size depending on the information available in the original research report. In addition, the program computes an unbiased estimate of effect size.

William L. Curlette

1987-01-01

50

The Appropriateness of Unbiased Optical Fractionators to Assess Cell Proliferation in the Adult Hippocampus  

PubMed Central

Optical fractionators have dominated the field of neural cell counting for two decades. These unbiased stereological techniques are often used for the quantification of hippocampal cell proliferation in neurogenesis experiments. However, the heterogeneous distribution of labeled cells, especially in the form of clusters, confounds the application of these techniques. A critical evaluation of the applicability of the optical fractionator suggests that absolute counting achieves higher efficiency in the quantification of cell proliferation than unbiased estimations.

Noori, Hamid R.; Fornal, Casimir A.

2011-01-01

51

Probing Heterogeneous Electron Transfer at an Unbiased Conductor by Scanning Electrochemical Microscopy in the Feedback Mode  

PubMed Central

The theory of the feedback mode of scanning electrochemical microscopy is extended for probing heterogeneous electron transfer at an unbiased conductor. A steady-state SECM diffusion problem with a pair of disk ultramicroelectrodes as a tip and a substrate is solved numerically. The potential of the unbiased substrate is such that the net current flow across the substrate/solution interface is zero. For a reversible substrate reaction, the potential and the corresponding tip current depend on SECM geometries with respective to the tip radius including not only the tip–substrate distance and the substrate radius but also the thickness of the insulating sheath surrounding the tip. A larger feedback current is obtained using a probe with a thinner insulating sheath, enabling identification of a smaller unbiased substrate with a radius that is approximately as small as the tip radius. An intrinsically slow reaction at an unbiased substrate as driven by a SECM probe can be quasi-reversible. The standard rate constant of the substrate reaction can be determined from the feedback tip current when the SECM geometries are known. The numerical simulations are extended to an SECM line scan above an unbiased substrate to demonstrate a “dip” in the steady-state tip current above the substrate center. The theoretical predictions are confirmed experimentally for reversible and quasi-reversible reactions at an unbiased disk substrate using disk probes with different tip radii and outer radii.

Xiong, Hui; Guo, Jidong; Amemiya, Shigeru

2008-01-01

52

Moment, energy, stress drop, and source spectra of western United States earthquakes from regional coda envelopes  

Microsoft Academic Search

We present a new method to estimate stable seismic source parameters, such as energy, moment, and Orowan stress drop, using regional coda envelopes from as few as one broadband station. We use the method to compute path- and site-corrected seismic moment-rate spectra for 117 recent western United States earthquakes. Empirical Green's function corrections were applied to our surface- and body-wave

Kevin Mayeda; William R. Walter

1996-01-01

53

The correspondence between mutually unbiased bases and mutually orthogonal extraordinary supersquares  

NASA Astrophysics Data System (ADS)

We study the connection between mutually unbiased bases and mutually orthogonal extraordinary supersquares, a wider class of squares which does not contain only the Latin squares. We show that there are four types of complete sets of mutually orthogonal extraordinary supersquares for the dimension d = 8. We introduce the concept of physical striation and show that this is equivalent to the extraordinary supersquare. The general algorithm for obtaining the mutually unbiased bases and the physical striations is constructed and it is shown that the complete set of mutually unbiased physical striations is equivalent to the complete set of mutually orthogonal extraordinary supersquares. We apply the algorithm to two examples: one for two-qubit systems (d = 4) and one for three-qubit systems (d = 8), by using the Type II complete sets of mutually orthogonal extraordinary supersquares of order 8.

Ghiu, Iulia; Ghiu, Cristian

2014-02-01

54

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

55

ORDER STATISTICS-BASED UNBIASED HOMOMORPHIC SYSTEM TO REDUCE MULTIPLICATIVE NOISE  

Microsoft Academic Search

In this paper, we propose an order statistics-based unbiased homomorphic system to reduce multiplicative noise. The de- sign of such a system is based on the probability density function (PDF) of the noise. First, we generalize the order statistics-based nonlinear filter called the sampled function weighted order (SFWO) filter proposed in (1) to reduce addi- tive noise, to the case

Debashis Sen; M. N. S. Swamy; M. O. Ahmad

56

An unbiased hard X-ray survey of the nearest Seyfert 2 galaxies  

Microsoft Academic Search

The BATSE Earth Occultation data is being successfully used to study the temporal and spectral properties of an unbiased sample of Seyfert 2 galaxies in the 20-100 keV energy range over a period of 8 years. The sample used is the enlarged Maiolino and Reike sample restricted in distance to those (46) located within 42 Mpc from Earth. Of the

M. J. Westmore; R. Gurriaran; A. J. Dean; F. Lei; A. Malizia; L. Bassani; J. B. Stephen; B. A. Harmon; M. L. McCollough

2000-01-01

57

Dynamic and Stochastic Instability and the Unbiased Forward Rate Hypothesis: A Variable Mean Response Approach  

Microsoft Academic Search

Since the mid-1970's, the unbiased forward rate hypothesis (UFRH) of forward and spot exchange rates has been intensively studied and tested with inconclusive and contradictory results. On the basis of the hypothesis, this paper provides variable mean response (VMR) random coefficients models to capture the time-varying and stochastic behavior of the slope coefficient to be referred to as the currency

Winston T. Lin

58

An unbiased parametric imaging algorithm for nonuniformly sampled biomedical system parameter estimation  

Microsoft Academic Search

An unbiased algorithm of generalized linear least squares (GLLS) for parameter estimation of nonuniformly sampled biomedical systems is proposed. The basic theory and detailed derivation of the algorithm are given. This algorithm removes the initial values required and computational burden of nonlinear least regression and achieves a comparable estimation quality in terms of the estimates' bias and standard deviation. Therefore,

Dagan Feng; Sung-Cheng Huang; ZhiZhong Wang; D. Ho

1996-01-01

59

Studies of an Optimally Unbiased MA Filter Intended for GPS-Based Timekeeping.  

National Technical Information Service (NTIS)

In this paper, we examine one of the possible approaches to design an optimally unbiased moving average (MA) filter intended for the time error online estimating and synchronization in timekeeping. The approach is based on the slowly changing nature of a ...

O. Ibarra-Manzano R. Rojas-Laguana R. Vazguez- Bautista Y. Shmaliy

2001-01-01

60

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

61

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

62

FDIC Center for Financial Research Working Paper No. 2005-04. Unbiased Capital Allocation in an Asymptotic Single Risk Factor (ASRF) Model of Credit Risk.  

National Technical Information Service (NTIS)

This paper derives unbiased capital allocation rules for portfolios in which credit risk is driven by a single common factor and idiosyncratic risk is fully diversified. The methodology for setting unbiased capital allocations is developed in the context ...

P. Kupiec

2005-01-01

63

Rapid purification of quantum systems by measuring in a feedback-controlled unbiased basis  

NASA Astrophysics Data System (ADS)

Rapid purification by feedback—specifically, reducing the mean impurity faster than by measurement alone—can be achieved by choosing the eigenbasis of the density matrix to be unbiased relative to the measurement basis. Here we further examine the protocol introduced by Combes and Jacobs [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.96.010504 96, 010504 (2006)] involving continuous measurement of the observable Jz for a D-dimensional system. We rigorously rederive the lower bound (2/3)(D+1) on the achievable speedup factor and also an upper bound, namely D2/2, for all feedback protocols that use measurements in unbiased bases. Finally, we extend our results to n independent measurements on a register of n qubits and derive an upper bound on the achievable speedup factor that scales linearly with n.

Combes, Joshua; Wiseman, Howard M.; Jacobs, Kurt; O'Connor, Anthony J.

2010-08-01

64

Monofunctional stealth nanoparticle for unbiased single molecule tracking inside living cells.  

PubMed

On the basis of a protein cage scaffold, we have systematically explored intracellular application of nanoparticles for single molecule studies and discovered that recognition by the autophagy machinery plays a key role for rapid metabolism in the cytosol. Intracellular stealth nanoparticles were achieved by heavy surface PEGylation. By combination with a generic approach for nanoparticle monofunctionalization, efficient labeling of intracellular proteins with high fidelity was accomplished, allowing unbiased long-term tracking of proteins in the outer mitochondrial membrane. PMID:24655019

Lisse, Domenik; Richter, Christian P; Drees, Christoph; Birkholz, Oliver; You, Changjiang; Rampazzo, Enrico; Piehler, Jacob

2014-04-01

65

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

66

Comment on "Unbiased Statistical Analysis for Multi-Stage Proteomic Search Strategies"  

PubMed Central

Everett et al. recently reported on a statistical bias that arises in the target-decoy approach to false discovery rate estimation in two-pass proteomics search strategies as exemplified by X!Tandem. This bias can cause serious underestimation of the false discovery rate. We argue here that the “unbiased” solution proposed by Everett et al., however, is also biased, and under certain circumstances can also result in a serious underestimate of the FDR, especially at the protein level.

Bern, Marshall; Kil, Yong J.

2013-01-01

67

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

NASA Astrophysics Data System (ADS)

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.

2005-05-01

68

Experimental studies of unbiased gluon jets from e+e- annihilations using the jet boost algorithm  

Microsoft Academic Search

We present the first experimental results based on the jet boost algorithm, a technique to select unbiased samples of gluon jets in e+e- annihilations, i.e. gluon jets free of biases introduced by event selection or jet finding criteria. Our results are derived from hadronic Z0 decays observed with the OPAL detector at the LEP e+e- collider at CERN. First, we

G. Abbiendi; C. Ainsley; P. F. Åkesson; G. Alexander; J. Allison; P. Amaral; G. Anagnostou; K. J. Anderson; S. Arcelli; S. Asai; D A Axen; Georges Azuelos; I. Bailey; E. Barberio; T. Barillari; R. J. Barlow; R. J. Batley; P. Bechtle; T. Behnke; K. W. Bell; P. J. Bell; G. Bella; A. Bellerive; G. Benelli; Siegfried Bethke; O. Biebel; O. Boeriu; P. Bock; M. Boutemeur; S. Braibant; L. Brigliadori; R. M. Brown; K. Buesser; H. J. Burckhart; S. Campana; R. K. Carnegie; B. Caron; A. A. Carter; J. R. Carter; C. Y. Chang; D. G. Charlton; C. Ciocca; Akos Csilling; M. Cuffiani; S. Dado; A. de Roeck; E. A. de Wolf; Klaus Desch; B. Dienes; M. Donkers; J. Dubbert; E. Duchovni; G. Duckeck; I. P. Duerdoth; E. Etzion; Franco Luigi Fabbri; L. Feld; P. Ferrari; F. Fiedler; I. Fleck; M. Ford; A. Frey; A. Fürtjes; P. Gagnon; J. W. Gary; G. Giacomelli; C. Geich-Gimbel; P. Giacomelli; M. Giunta; J. Goldberg; E. Gross; Jacob Grunhaus; M. Gruwé; P. O. Günther; A. Gupta; C. Hajdu; M. Hamann; G. G. Hanson; A. Harel; M. Hauschild; C. M. Hawkes; R. Hawkings; Richard J Hemingway; C. Hensel; G. Herten; R. D. Heuer; J. C. Hill; K. Hoffman; D. Horváth; P. Igo-Kemenes; K. Ishii; H. Jeremie; P. Jovanovic; T. R. Junk; N. Kanaya; J. Kanzaki; Dean A Karlen; K. Kawagoe; T. Kawamoto; Richard K Keeler; R. G. Kellogg; B. W. Kennedy; K. Klein; A. Klier; S. Kluth; T. Kobayashi; M. Kobel; S. Komamiya; L L Kormos; T. Krämer; P. Krieger; J. von Krogh; K. Kruger; T. Kuhl; M. Kupper; G. D. Lafferty; Hagar Yaël Landsman; D. Lanske; J. G. Layter; D. Lellouch; J. Letts; L. Levinson; J. Lillich; S. L. Lloyd; F. K. Loebinger; J. Lu; A. Ludwig; J. Ludwig; A. MacPherson; W. Mader; S. Marcellini; A. J. Martin; G. Masetti; T. J. McMahon; P. Mättig; W. J. McDonald; J A McKenna; R. A. McPherson; F. Meijers; W. Menges; F. S. Merritt; H. Mes; Aldo Michelini; S. Mihara; G. Mikenberg; D. J. Miller; S. Moed; W. Mohr; T. Mori; A. Mutter; K. Nagai; I. Nakamura; H. Nanjo; H. A. Neal; R. Nisius; S. W. O'Neale; A. Oh; A N Okpara; M. J. Oreglia; S. Orito; C. Pahl; G. Pásztor; J. R. Pater; J. E. Pilcher; J L Pinfold; D. E. Plane; B. Poli; J. Polok; O. Pooth; M B Przybycien; A. Quadt; K. Rabbertz; C. Rembser; P. Renkel; J. M. Roney; S. Rosati; Y. Rozen; K. Runge; K. Sachs; T. Saeki; E Sarkisyan-Grinbaum; A. D. Schaile; O. Schaile; P. Scharff-Hansen; J. Schieck; T. Schörner-Sadenius; M. Schröder; M. Schumacher; C. Schwick; W. G. Scott; R. Seuster; T. G. Shears; B. C. Shen; P. Sherwood; A. Skuja; A. M. Smith; R J Sobie; S. Söldner-Rembold; F. Spano; A. Stahl; K. Stephens; D. Strom; R. Ströhmer; S. Tarem; M. Tasevsky; R. Teuscher; M. A. Thomson; E. Torrence; D. Toya; P. Tran; I. Trigger; Z L Trócsányi; E. Tsur; M. F. Turner-Watson; I. Ueda; B. Ujvári; C. F. Vollmer; P. Vannerem; R. Vértesi; M. Verzocchi; H. Voss; Joost Herman Vossebeld; D. Waller; C. P. Ward; D. R. Ward; P. M. Watkins; A. T. Watson; N. K. Watson; P. S. Wells; T. Wengler; N. Wermes; D. Wetterling; G. W. Wilson; J. A. Wilson; G. Wolf; T. R. Wyatt; S. Yamashita; D. Zer-Zion; L. Zivkovic

2004-01-01

69

Extending unbiased stereology of brain ultrastructure to three-dimensional volumes  

NASA Technical Reports Server (NTRS)

OBJECTIVE: Analysis of brain ultrastructure is needed to reveal how neurons communicate with one another via synapses and how disease processes alter this communication. In the past, such analyses have usually been based on single or paired sections obtained by electron microscopy. Reconstruction from multiple serial sections provides a much needed, richer representation of the three-dimensional organization of the brain. This paper introduces a new reconstruction system and new methods for analyzing in three dimensions the location and ultrastructure of neuronal components, such as synapses, which are distributed non-randomly throughout the brain. DESIGN AND MEASUREMENTS: Volumes are reconstructed by defining transformations that align the entire area of adjacent sections. Whole-field alignment requires rotation, translation, skew, scaling, and second-order nonlinear deformations. Such transformations are implemented by a linear combination of bivariate polynomials. Computer software for generating transformations based on user input is described. Stereological techniques for assessing structural distributions in reconstructed volumes are the unbiased bricking, disector, unbiased ratio, and per-length counting techniques. A new general method, the fractional counter, is also described. This unbiased technique relies on the counting of fractions of objects contained in a test volume. A volume of brain tissue from stratum radiatum of hippocampal area CA1 is reconstructed and analyzed for synaptic density to demonstrate and compare the techniques. RESULTS AND CONCLUSIONS: Reconstruction makes practicable volume-oriented analysis of ultrastructure using such techniques as the unbiased bricking and fractional counter methods. These analysis methods are less sensitive to the section-to-section variations in counts and section thickness, factors that contribute to the inaccuracy of other stereological methods. In addition, volume reconstruction facilitates visualization and modeling of structures and analysis of three-dimensional relationships such as synaptic connectivity.

Fiala, J. C.; Harris, K. M.; Koslow, S. H. (Principal Investigator)

2001-01-01

70

An Unbiased, Double-Blind Study of Terrestrial Debris in Evolved Planetary Systems  

NASA Astrophysics Data System (ADS)

We propose to observe, in an unbiased manner, a large sample of white dwarfs with post-main sequence ages between 20 and 120 Myr to search for evidence of rocky circumstellar debris. Our targets are identical to those selected for an approved HST Cycle 18 Snapshot program for ultraviolet spectroscopy with COS. These stars were chosen only for their brightness and to be within a narrow range of effective temperatures amenable to our science goals. The COS observations will measure the metal content of the stars while the Spitzer observations will search for the presence of warm, circumstellar dust. In this manner, for the first time, we will obtain an unbiased picture of planetary debris in the post-main sequence -- in frequency of occurence per star, in its chemical composition via the atmospheric metal pollution, and in its accretion-production rate -- all as a function of cooling age and main-sequence progenitor mass. It will be the first and only unbiased search for both atmospheric metals and circumstellar dust at a complete sample of white dwarfs with well defined post-main sequence ages and reliable mass determinations. As such, we will be able to overcome existing limitations in the field, determine clean statistics for the first time, and distinguish the influences of cooling age and atmospheric metal content on the observed disk frequency.

Farihi, Jay; Gaensicke, Boris; Girven, Jonathan

2011-05-01

71

An Investigation of Nonuniform Deposition of Field Emission Displays Phosphors on Unbiased Indium-Tin-Oxide Coated Glass During Electrophoresis  

NASA Astrophysics Data System (ADS)

Upon the deposition of field emission displays (FED) phosphors in electrophoresis, a weak and nonuniform deposition of phosphor on the unbiased neighbor indium-tin-oxide (ITO) patterns is always observed in addition to the expected thick and uniform deposition of phosphor on the biased patterns. An explanation of the origin of the nonuniform deposition is attempted by solving Laplace’s equation with proper boundary conditions simulating the deposition bath used for the sample preparation. According to the solution of Laplace’s equation, in the beginning, the potential distribution is such that the electric field has a parallel component from the unbiased ITOs to the biased ones in addition to the major vertical components of the electrical field. However, during the deposition, the field has the parallel component from the biased ITOs to the unbiased ones as the thickness of the deposited phosphor increases. This appears to generate the observed nonuniform deposition on the unbiased ITO patterns.

Shin, Sang Hoon; Jeon, Duk Young; Jin, Yong Wan; Kim, Jong Min

2000-12-01

72

Improving Agricultural Drought Monitoring in East Africa with Unbiased Rainfall Fields and Detailed Land Surface Physics  

NASA Astrophysics Data System (ADS)

Monitoring drought is particularly challenging within rainfed agricultural and pastoral systems, where it can serve the greatest need. Such locations often have sparse or non-existent ground based measurements of precipitation, evapotranspiration (ET), and soil moisture. For more effective drought monitoring with limited hydroclimate observations, we simulate land surface states using the Community Noah Land Surface Model forced with different merged rainfall products inside a Land Information System (LIS). Using model outputs we will answer the questions: How sensitive are soil moisture and ET fields to differences in rainfall forcing and model physics? What are acceptable drought-specific tradeoffs between near-real time availability and skill of rainfall data? Preliminary results with the African Rainfall Estimation Algorithm Version 2 (RFE2.0) outperformed global products, suggesting that sub-global rainfall estimates are the way forward for regional drought monitoring. Specifically, the Noah model forced with RFE2.0 better resolved the heterogeneous patterns in crop stress than the Famine Early Warning System Network (FEWS NET) operational Water Requirement Satisfaction Index (WRSI) model. To further investigate the improvement in drought monitoring while maintaining timeliness, we unbias (using Africa specific climatology) the precipitation products from CPC Merged Analysis of Precipitation (CMAP), Tropical Rainfall Measurement Mission (TRMM), and RFE2.0. The skill (relative accuracy) and reliability (average agreement) of the unbiased rainfall are calculated against an unbiased precipitation product augmented with station data from Ethiopia and Kenya. Soil moisture and ET fields from Noah are compared to the operational FEWS NET WRSI, soil water anomaly index, and the World Food Program’s Crop and Food Security Assessment Mission reports. We anticipate that the unbiased rainfall fields will improve the accuracy, spatio-temporal resolution, and heterogeneity of the ET and soil moisture estimates compared to current operational drought indicators. Ultimately, these improved information products will better inform decision makers about seasonal food production and help them assess the need for relief, potentially saving millions of lives.

McNally, A.; Yatheendradas, S.; Peters-Lidard, C. D.; Michaelsen, J.

2010-12-01

73

Genomic best linear unbiased prediction (gBLUP) for the estimation of genomic breeding values.  

PubMed

Genomic best linear unbiased prediction (gBLUP) is a method that utilizes genomic relationships to estimate the genetic merit of an individual. For this purpose, a genomic relationship matrix is used, estimated from DNA marker information. The matrix defines the covariance between individuals based on observed similarity at the genomic level, rather than on expected similarity based on pedigree, so that more accurate predictions of merit can be made. gBLUP has been used for the prediction of merit in livestock breeding, may also have some applications to the prediction of disease risk, and is also useful in the estimation of variance components and genomic heritabilities. PMID:23756897

Clark, Samuel A; van der Werf, Julius

2013-01-01

74

Discrete phase-space structure of n-qubit mutually unbiased bases  

SciTech Connect

We work out the phase-space structure for a system of n qubits. We replace the field of real numbers that label the axes of the continuous phase space by the finite field GF(2{sup n}) and investigate the geometrical structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves intersecting only at the origin and satisfying certain additional properties. We provide a simple classification of such curves and study in detail the four- and eight-dimensional cases, analyzing also the effect of local transformations. In this way, we provide a comprehensive phase-space approach to the construction of mutually unbiased bases for n qubits.

Klimov, A.B.; Romero, J.L. [Departamento de Fisica, Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico); Bjoerk, G. [School of Information and Communication Technology, Royal Institute of Technology (KTH), Electrum 229, SE-164 40 Kista (Sweden); Sanchez-Soto, L.L. [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain)], E-mail: lsanchez@fis.ucm.es

2009-01-15

75

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

76

Unbiased acceleration measurements with an electrostatic accelerometer on a rotating platform  

NASA Astrophysics Data System (ADS)

The Gravity Advanced Package is an instrument composed of an electrostatic accelerometer called MicroSTAR and a rotating platform called Bias Rejection System. It aims at measuring with no bias the non-gravitational acceleration of a spacecraft. It is envisioned to be embarked on an interplanetary spacecraft as a tool to test the laws of gravitation.MicroSTAR is based on Onera's experience and inherits in orbit technology. The addition of the rotating platform is a technological upgrade which allows using an electrostatic accelerometer to make measurements at low frequencies with no bias. To do so, the Bias Rejection System rotates MicroSTAR such that the signal of interest is separated from the bias of the instrument in the frequency domain. Making these unbiased low-frequency measurements requires post-processing the data. The signal processing technique developed for this purpose is the focus of this article. It allows giving the conditions under which the bias is completely removed from the signal of interest. And the precision of the unbiased measurements can be fully characterized: given the characteristics of the subsystems, it is possible to reach a precision of 1 pm s-2 on the non-gravitational acceleration for an integration time of 3 h.

Lenoir, Benjamin; Christophe, Bruno; Reynaud, Serge

2013-01-01

77

Knowing What Counts: Unbiased Stereology in the Non-human Primate Brain  

PubMed Central

The non-human primate is an important translational species for understanding the normal function and disease processes of the human brain. Unbiased stereology, the method accepted as state-of-the-art for quantification of biological objects in tissue sections2, generates reliable structural data for biological features in the mammalian brain3. The key components of the approach are unbiased (systematic-random) sampling of anatomically defined structures (reference spaces), combined with quantification of cell numbers and size, fiber and capillary lengths, surface areas, regional volumes and spatial distributions of biological objects within the reference space4. Among the advantages of these stereological approaches over previous methods is the avoidance of all known sources of systematic (non-random) error arising from faulty assumptions and non-verifiable models. This study documents a biological application of computerized stereology to estimate the total neuronal population in the frontal cortex of the vervet monkey brain (Chlorocebus aethiops sabeus), with assistance from two commercially available stereology programs, BioQuant Life Sciences and Stereologer (Figure 1). In addition to contrast and comparison of results from both the BioQuant and Stereologer systems, this study provides a detailed protocol for the Stereologer system.

Burke, Mark; Zangenehpour, Shahin; Mouton, Peter R.; Ptito, Maurice

2009-01-01

78

Unbiased query-by-bagging active learning for VHR image classification  

NASA Astrophysics Data System (ADS)

A key factor for the success of supervised remote sensing image classification is the definition of an efficient training set. Suboptimality in the selection of the training samples can bring to low classification performance. Active learning algorithms aim at building the training set in a smart and efficient way, by finding the most relevant samples for model improvement and thus iteratively improving the classification performance. In uncertaintybased approaches, a user-defined heuristic ranks the unlabeled samples according to the classifier's uncertainty about their class membership. Finally, the user is asked to define the labels of the pixels scoring maximum uncertainty. In the present work, an unbiased uncertainty scoring function encouraging sampling diversity is investigated. A modified version of the Entropy Query by Bagging (EQB) approach is presented and tested on very high resolution imagery using both SVM and LDA classifiers. Advantages of favoring diversity in the heuristics are discussed. By the diverse sampling it enhances, the unbiased approach proposed leads to higher convergence rates in the first iterations for both the models considered.

Copa, Loris; Tuia, Devis; Volpi, Michele; Kanevski, Mikhail

2010-10-01

79

Quantitative assessment of in-solution digestion efficiency identifies optimal protocols for unbiased protein analysis.  

PubMed

The majority of mass spectrometry-based protein quantification studies uses peptide-centric analytical methods and thus strongly relies on efficient and unbiased protein digestion protocols for sample preparation. We present a novel objective approach to assess protein digestion efficiency using a combination of qualitative and quantitative liquid chromatography-tandem MS methods and statistical data analysis. In contrast to previous studies we employed both standard qualitative as well as data-independent quantitative workflows to systematically assess trypsin digestion efficiency and bias using mitochondrial protein fractions. We evaluated nine trypsin-based digestion protocols, based on standard in-solution or on spin filter-aided digestion, including new optimized protocols. We investigated various reagents for protein solubilization and denaturation (dodecyl sulfate, deoxycholate, urea), several trypsin digestion conditions (buffer, RapiGest, deoxycholate, urea), and two methods for removal of detergents before analysis of peptides (acid precipitation or phase separation with ethyl acetate). Our data-independent quantitative liquid chromatography-tandem MS workflow quantified over 3700 distinct peptides with 96% completeness between all protocols and replicates, with an average 40% protein sequence coverage and an average of 11 peptides identified per protein. Systematic quantitative and statistical analysis of physicochemical parameters demonstrated that deoxycholate-assisted in-solution digestion combined with phase transfer allows for efficient, unbiased generation and recovery of peptides from all protein classes, including membrane proteins. This deoxycholate-assisted protocol was also optimal for spin filter-aided digestions as compared with existing methods. PMID:23792921

León, Ileana R; Schwämmle, Veit; Jensen, Ole N; Sprenger, Richard R

2013-10-01

80

Fluorescence Spectra  

NSDL National Science Digital Library

This experiment uses the Tracker video analysis and modeling tool to explore the phenomenon of fluorescence and its application in fluorescent lamps. For each of five different visible spectra, students (a) observe the spectrum directly, (b) measure its brightness versus wavelength in Tracker, and (c) answer both qualitative and quantitative questions about it. The spectra include a fluorescent dye with laser and UV illumination, a mercury lamp and two fluorescent lamps, all with red and green laser spots added for easy calibration. For more information, see the AAPT presentation. The zip file includes the lab instructions, spectrum images and Tracker data files. This requires Tracker version 4.62 or higher. Tracker installers are available for Windows, Mac and Linux from ComPADRE or the Tracker web site (http://www.cabrillo.edu/~dbrown/tracker/).

Brown, Douglas

2012-01-17

81

An unbiased survey for dense cores in the Lynds 1630 molecular cloud  

NASA Technical Reports Server (NTRS)

An unbiased, systematic survey for dense cores within the L1630 (Orion B) molecular cloud has been completed. This survey provides the first complete census of dense (n greater tha 10,000/cu cm) cores within a molecular cloud. To identify the dense gas, 3.6 square degrees of the L1630 cloud were surveyed in the J = 2-1 transition of CS. CS emission was detected over 10 percent of the area surveyed, and this emission is not uniformly distributed throughout the cloud but is confined to 42 dense cores. The size, shape, velocity dispersion, and mass of these cores are examined. Comparison of the mass contained within dense cores with the total gas mass within the surveyed region, estimated from CO emission, reveals that the dense cores constitute only a small fraction (not greater than 19 percent) of the total cloud mass.

Lada, Elizabeth A.; Bally, John; Stark, Antony A.

1991-01-01

82

Directed Transport of the Davydov Solitons by Unbiased a.c. Forces  

NASA Astrophysics Data System (ADS)

We show that in asymmetric molecular chains a periodic unbiased field causes a drift of the Davydov solitons. This directed current, known as ratchet phenomenon, has a threshold with respect to the intensity and the frequency of the field. In spatially symmetric chains a harmonic periodic electric field generates oscillations of solitons but does not result in their directed drift. Such a drift current can be induced in symmetric chains by a time periodic asymmetric external field. This complex dynamics of solitons is generated by the interplay between the Peierls-Nabarro barrier, external field and dissipative effects in the chain. The dependence of the amplitude of soliton oscillations and the velocity of the drift are shown to depend on the intensity of the field, its frequency and the coefficient of the energy dissipation.

Brizhik, L. S.; Eremko, A. A.; Piette, B. M. A. G.; Zakrzewski, W. J.

83

Solution to the mean king's problem with mutually unbiased bases for arbitrary levels  

NASA Astrophysics Data System (ADS)

The mean king’s problem with mutually unbiased bases is reconsidered for arbitrary d -level systems. Hayashi [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.

Kimura, Gen; Tanaka, Hajime; Ozawa, Masanao

2006-05-01

84

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

85

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

PubMed Central

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, Cedric; Kirshner, Hagai; Carlini, Lina; Olivier, Nicolas; Holden, Seamus; Manley, Suliana; Ye, Jong Chul; Unser, Michael

2014-01-01

86

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

87

Balanced-PCR amplification allows unbiased identification of genomic copy changes in minute cell and tissue samples  

Microsoft Academic Search

Analysis of genomic DNA derived from cells and fresh or fixed tissues often requires whole genome amplification prior to microarray screening. Technical hurdles to this process are the introduc- tion of amplification bias and\\/or the inhibitory effects of formalin fixation on DNA amplification. Here we demonstrate a balanced-PCR procedure that allows unbiased amplification of genomic DNA from fresh or modestly

Gang Wang; Cameron Brennan; Martha Rook; Jia Liu Wolfe; Christopher Leo; Lynda Chin; Hongjie Pan; Wei-Hua Liu; G. Mike Makrigiorgos

2004-01-01

88

An Investigation of Nonuniform Deposition of Field Emission Displays Phosphors on Unbiased Indium-Tin-Oxide Coated Glass During Electrophoresis  

Microsoft Academic Search

Upon the deposition of field emission displays (FED) phosphors in electrophoresis, a weak and nonuniform deposition of phosphor on the unbiased neighbor indium-tin-oxide (ITO) patterns is always observed in addition to the expected thick and uniform deposition of phosphor on the biased patterns. An explanation of the origin of the nonuniform deposition is attempted by solving Laplace's equation with proper

Sang Hoon Shin; Duk Young Jeon; Yong Wan Jin; Jong Min Kim

2000-01-01

89

An Unbiased Estimate of the Global Hubble Constant in the Region of Pisces-Perseus  

NASA Astrophysics Data System (ADS)

We obtain an unbiased estimate of the global Hubble constant H0 in a volume of cz <= 12,000 km s-1 in the region of Pisces-Perseus. The Tully-Fisher (TF) relation is applied to a magnitude-limited sample of 441 spiral galaxies selected from the Arecibo 21 cm catalog. We improve the photometry data of the previous TF study by Ichikawa & Fukugita by using our original surface photometry data and local calibrators that have newly been made available in other works. The photometry data were calibrated with CCD observations, and we achieve 0.13 mag for a photometric internal error. We use a maximum likelihood method for the TF analysis. Monte Carlo simulations demonstrate that our method reproduces a given H0 at the 95% confidence level. By applying the method to our sample galaxies, we obtain the unbiased global Hubble constant H0=65+/-2+20-14 km s-1 Mpc-1 the first and the second terms represent the internal random error and the external uppermost and lowermost systematic errors, respectively. We also find a good agreement for our H0 with those recently obtained via Cepheid observation in the local universe and the TF relation and supernovae applied to a spatial volume comparable to or larger than ours. Hubble velocities of the spirals inferred from our H0 show no significant systematic differences from those given in the Mark III catalog. The same analysis for H0 is carried out using the r-band photometry data of the Pisces-Perseus region given by Willick et al. We obtain a global H0 that is consistent with that obtained from the B-band analysis. A bulk motion in the Pisces-Perseus region is briefly discussed, based on our calibration of H0. The B-band intrinsic TF scatter is too large to allow any determination of bulk motion. However, our r-band TF analysis supports the notion of a coherent streaming motion of the Pisces-Perseus ridge with a velocity of ~-200 km s-1 with respect to the CMB, in agreement with most modern studies.

Watanabe, Masaru; Ichikawa, Takashi; Okamura, Sadanori

1998-08-01

90

Isolation of a mycoplasma-specific binding peptide from an unbiased phage-displayed peptide library.  

PubMed

An important goal in medicine is the development of methods for cell-specific targeting of therapeutic molecules to pathogens or pathogen-infected cells. However, little progress has been made in cell-specific targeting of bacterially infected cells. Using a phage display approach, we have isolated a 20-mer peptide that binds to Mycoplasma arginini infected pancreatic beta-cells in tissue culture. This peptide binds to M. arginini infected beta-cells 200 times better than a control phage and is specific for the infected cells. Furthermore, transferring the M. arginini contamination to another cell line renders the newly infected cell line susceptible to peptide binding. Immunolocalization experiments suggest that the peptide is binding to M. arginini adhered to the cell surface. The free synthetic peptide retains its binding in the absence of the phage vehicle and tetramerization of the peptide increases its affinity for the infected cells. Efforts have been made to use this peptide to eliminate Mycoplasma from infected cell lines using ferromagnetic beads coated with the selected peptide. A ten-fold reduction of infection was accomplished with one fractionation via this approach. Our results suggest that this peptide, isolated from an unbiased selection, may be of utility for the detection and reduction of Mycoplasma infection in cultured cells. Furthermore, a general implication of our findings is that phage display methods may be useful for identifying peptides that target a broad array of other biological pathogens in a specific fashion. PMID:16880978

De, Jitakshi; Chang, Ya-Ching; Samli, Kausar N; Schisler, Jonathan C; Newgard, Christopher B; Johnston, Stephen A; Brown, Kathlynn C

2005-07-01

91

Unbiased Discovery of Glypican as a Novel Receptor for LRRTM4 in Regulating Excitatory Synapse Development  

PubMed Central

SUMMARY Leucine-rich repeat (LRR) proteins have recently been identified as important regulators of synapse development and function, but for many LRR proteins the ligand-receptor interactions are not known. Here we identify the heparan sulfate (HS) proteoglycan glypican as a novel receptor for LRRTM4 using an unbiased proteomics-based approach. Glypican binds LRRTM4, but not LRRTM2, in a HS-dependent manner. Glypican 4 (GPC4) and LRRTM4 localize to the pre- and postsynaptic membranes of excitatory synapses, respectively. Consistent with a trans-synaptic interaction, LRRTM4 triggers GPC4 clustering in contacting axons and GPC4 induces clustering of LRRTM4 in contacting dendrites in a HS-dependent manner. LRRTM4 positively regulates excitatory synapse development in cultured neurons and in vivo, and the synaptogenic activity of LRRTM4 requires the presence of HS on the neuronal surface. Our results identify glypican as a novel LRRTM4 receptor and indicate that a trans-synaptic glypican-LRRTM4 interaction regulates excitatory synapse development.

de Wit, Joris; O'Sullivan, Matthew L.; Savas, Jeffrey N.; Condomitti, Giuseppe; Caccese, Max C.; Vennekens, Kristel M.; Yates, John R.; Ghosh, Anirvan

2014-01-01

92

Unbiased discovery of glypican as a receptor for LRRTM4 in regulating excitatory synapse development.  

PubMed

Leucine-rich repeat (LRR) proteins have recently been identified as important regulators of synapse development and function, but for many LRR proteins the ligand-receptor interactions are not known. Here we identify the heparan sulfate (HS) proteoglycan glypican as a receptor for LRRTM4 using an unbiased proteomics-based approach. Glypican binds LRRTM4, but not LRRTM2, in an HS-dependent manner. Glypican 4 (GPC4) and LRRTM4 localize to the pre- and postsynaptic membranes of excitatory synapses, respectively. Consistent with a trans-synaptic interaction, LRRTM4 triggers GPC4 clustering in contacting axons and GPC4 induces clustering of LRRTM4 in contacting dendrites in an HS-dependent manner. LRRTM4 positively regulates excitatory synapse development in cultured neurons and in vivo, and the synaptogenic activity of LRRTM4 requires the presence of HS on the neuronal surface. Our results identify glypican as an LRRTM4 receptor and indicate that a trans-synaptic glypican-LRRTM4 interaction regulates excitatory synapse development. PMID:23911103

de Wit, Joris; O'Sullivan, Matthew L; Savas, Jeffrey N; Condomitti, Giuseppe; Caccese, Max C; Vennekens, Kristel M; Yates, John R; Ghosh, Anirvan

2013-08-21

93

Molecular karyotype (amplotype) of metastatic colorectal cancer by unbiased arbitrarily primed PCR DNA fingerprinting  

PubMed Central

Genomic instability characterizes the aneuploid cancer cell. Losses of genetic material are critical in cancer by exposing recessive mutations in tumor suppressor genes. Gains of genetic material also may lead to overexpression of genes contributing to tumor progression either in the presence or absence of mutation. However, the detection of moderate gains (such as tri-tetraploidy) has been a challenge in cancer research. Unbiased DNA fingerprinting by the arbitrarily primed PCR allows the detection of moderate gains (in addition to losses) of DNA sequences of known chromosomal localization. We have generated in this manner a molecular karyotype of metastatic colon cancer. This amplotype shows that sequences from several chromosomes undergo both losses (1, 4, 9, 14, and 18) and gains (6, 7, 12, and 20) in over half of the tumors. Moreover, gains of sequences from chromosomes 8 and 13 occurred in most tumors, indicating the existence in these chromosomes of positive regulators of cell growth or survival that are under strong positive selection during tumor progression. We conclude that overrepresentation of these chromosomal regions is a critical step for metastatic colorectal cancer. Comparative amplotype analysis from primary and metastatic tumors suggest the existence in chromosome 4 of gene(s) whose loss is specifically selected in cells that reach the metastatic stage.

Malkhosyan, Sergei; Yasuda, Jun; Soto, Jose Luis; Sekiya, Takao; Yokota, Jun; Perucho, Manuel

1998-01-01

94

Multiple events on single molecules: unbiased estimation in single-molecule biophysics.  

PubMed

Most analyses of single-molecule experiments consist of binning experimental outcomes into a histogram and finding the parameters that optimize the fit of this histogram to a given data model. Here we show that such an approach can introduce biases in the estimation of the parameters, thus great care must be taken in the estimation of model parameters from the experimental data. The bias can be particularly large when the observations themselves are not statistically independent and are subjected to global constraints, as, for example, when the iterated steps of a motor protein acting on a single molecule must not exceed the total molecule length. We have developed a maximum-likelihood analysis, respecting the experimental constraints, which allows for a robust and unbiased estimation of the parameters, even when the bias well exceeds 100%. We demonstrate the potential of the method for a number of single-molecule experiments, focusing on the removal of DNA supercoils by topoisomerase IB, and validate the method by numerical simulation of the experiment. PMID:16439482

Koster, Daniel A; Wiggins, Chris H; Dekker, Nynke H

2006-02-01

95

An unbiased risk estimator for image denoising in the presence of mixed poisson-gaussian noise.  

PubMed

The behavior and performance of denoising algorithms are governed by one or several parameters, whose optimal settings depend on the content of the processed image and the characteristics of the noise, and are generally designed to minimize the mean squared error (MSE) between the denoised image returned by the algorithm and a virtual ground truth. In this paper, we introduce a new Poisson-Gaussian unbiased risk estimator (PG-URE) of the MSE applicable to a mixed Poisson-Gaussian noise model that unifies the widely used Gaussian and Poisson noise models in fluorescence bioimaging applications. We propose a stochastic methodology to evaluate this estimator in the case when little is known about the internal machinery of the considered denoising algorithm, and we analyze both theoretically and empirically the characteristics of the PG-URE estimator. Finally, we evaluate the PG-URE-driven parametrization for three standard denoising algorithms, with and without variance stabilizing transforms, and different characteristics of the Poisson-Gaussian noise mixture. PMID:24723526

Le Montagner, Yoann; Angelini, Elsa D; Olivo-Marin, Jean-Christophe

2014-03-01

96

Intramolecular Hydroamination of Unbiased and Functionalized Primary Aminoalkenes Catalyzed by a Rhodium Aminophosphine Complex  

PubMed Central

We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups that would not be tolerated in hydroaminations catalyzed by more electrophilic systems. This catalyst contains an unusual diaminophosphine ligand that binds to rhodium in a ?3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C), occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, occur with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and occur with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late transition metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product vs reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes for the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center.

Julian, Lisa D.; Hartwig, John F.

2010-01-01

97

Unbiased compound screening identifies unexpected drug sensitivities and novel treatment options for gastrointestinal stromal tumors.  

PubMed

Most gastrointestinal stromal tumors (GIST) are caused by oncogenic KIT or platelet-derived growth factor receptor activation, and the small molecule kinase inhibitor imatinib mesylate is an effective first-line therapy for metastatic or unresectable GIST. However, complete remissions are rare and most patients ultimately develop resistance, mostly because of secondary mutations in the driver oncogenic kinase. Hence, there is a need for novel treatment options to delay failure of primary treatment and restore tumor control in patients who progress under therapy with targeted agents. Historic data suggest that GISTs do not respond to classical chemotherapy, but systematic unbiased screening has not been performed. In screening a compound library enriched for U.S. Food and Drug Administration (FDA)-approved chemotherapeutic agents (NCI Approved Oncology Drugs Set II), we discovered that GIST cells display high sensitivity to transcriptional inhibitors and topoisomerase II inhibitors. Mechanistically, these compounds exploited the cells' dependency on continuous KIT expression and/or intrinsic DNA damage response defects, explaining their activity in GIST. Mithramycin A, an indirect inhibitor of the SP1 transcription factor, and mitoxantrone, a topoisomerase II inhibitor, exerted significant antitumor effects in mouse xenograft models of human GIST. Moreover, these compounds were active in patient-derived imatinib-resistant primary GIST cells, achieving efficacy at clinically relevant concentrations. Taken together, our findings reveal that GIST cells have an unexpectedly high and specific sensitivity to certain types of FDA-approved chemotherapeutic agents, with immediate implications for encouraging their clinical exploration. PMID:24385214

Boichuk, Sergei; Lee, Derek J; Mehalek, Keith R; Makielski, Kathleen R; Wozniak, Agnieszka; Seneviratne, Danushka S; Korzeniewski, Nina; Cuevas, Rolando; Parry, Joshua A; Brown, Matthew F; Zewe, James; Taguchi, Takahiro; Kuan, Shin-Fan; Schöffski, Patrick; Debiec-Rychter, Maria; Duensing, Anette

2014-02-15

98

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

99

Unbiased discovery of in vivo imaging probes through in vitro profiling of nanoparticle libraries  

PubMed Central

Summary In vivo imaging reveals how proteins and cells function as part of complex regulatory networks in intact organisms, and thereby contributes to a systems-level understanding of biological processes. However, the development of novel in vivo imaging probes remains challenging. Most probes are directed against a limited number of pre-specified protein targets; cell-based screens for imaging probes have shown promise, but raise concerns over whether in vitro surrogate cell models recapitulate in vivo phenotypes. Here, we rapidly profile the in vitro binding of nanoparticle imaging probes in multiple samples of defined target vs. background cell types, using primary cell isolates. This approach selects for nanoparticles that show desired targeting effects across all tested members of a class of cells, and decreases the likelihood that an idiosyncratic cell line will unduly skew screening results. To adjust for multiple hypothesis testing, we use permutation methods to identify nanoparticles that best differentiate between the target and background cell classes. (This approach is conceptually analogous to one used for high-dimensionality datasets of genome-wide gene expression, e.g. to identify gene expression signatures that discriminate subclasses of cancer.) We apply this approach to the identification of nanoparticle imaging probes that bind endothelial cells, and validate our in vitro findings in human arterial samples, and by in vivo intravital microscopy in mice. Overall, this work presents a generalizable approach to the unbiased discovery of in vivo imaging probes, and may guide the further development of novel endothelial imaging probes.

Kelly, Kimberly A.; Shaw, Stanley Y.; Nahrendorf, Matthias; Kristoff, Kelly; Aikawa, Elena; Schreiber, Stuart L.; Clemons, Paul A.; Weissleder, Ralph

2009-01-01

100

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

101

Absorption and folding of melittin onto lipid bilayer membranes via unbiased atomic detail microsecond molecular dynamics simulation.  

PubMed

Unbiased molecular simulation is a powerful tool to study the atomic details driving functional structural changes or folding pathways of highly fluid systems, which present great challenges experimentally. Here we apply unbiased long-timescale molecular dynamics simulation to study the ab initio folding and partitioning of melittin, a template amphiphilic membrane active peptide. The simulations reveal that the peptide binds strongly to the lipid bilayer in an unstructured configuration. Interfacial folding results in a localized bilayer deformation. Akin to purely hydrophobic transmembrane segments the surface bound native helical conformer is highly resistant against thermal denaturation. Circular dichroism spectroscopy experiments confirm the strong binding and thermostability of the peptide. The study highlights the utility of molecular dynamics simulations for studying transient mechanisms in fluid lipid bilayer systems. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova. PMID:24769159

Chen, Charles H; Wiedman, Gregory; Khan, Ayesha; Ulmschneider, Martin B

2014-09-01

102

Unbiased tensor-based morphometry: improved robustness and sample size estimates for Alzheimer's disease clinical trials.  

PubMed

Various neuroimaging measures are being evaluated for tracking Alzheimer's disease (AD) progression in therapeutic trials, including measures of structural brain change based on repeated scanning of patients with magnetic resonance imaging (MRI). Methods to compute brain change must be robust to scan quality. Biases may arise if any scans are thrown out, as this can lead to the true changes being overestimated or underestimated. Here we analyzed the full MRI dataset from the first phase of Alzheimer's Disease Neuroimaging Initiative (ADNI-1) from the first phase of Alzheimer's Disease Neuroimaging Initiative (ADNI-1) and assessed several sources of bias that can arise when tracking brain changes with structural brain imaging methods, as part of a pipeline for tensor-based morphometry (TBM). In all healthy subjects who completed MRI scanning at screening, 6, 12, and 24months, brain atrophy was essentially linear with no detectable bias in longitudinal measures. In power analyses for clinical trials based on these change measures, only 39AD patients and 95 mild cognitive impairment (MCI) subjects were needed for a 24-month trial to detect a 25% reduction in the average rate of change using a two-sided test (?=0.05, power=80%). Further sample size reductions were achieved by stratifying the data into Apolipoprotein E (ApoE) ?4 carriers versus non-carriers. We show how selective data exclusion affects sample size estimates, motivating an objective comparison of different analysis techniques based on statistical power and robustness. TBM is an unbiased, robust, high-throughput imaging surrogate marker for large, multi-site neuroimaging studies and clinical trials of AD and MCI. PMID:23153970

Hua, Xue; Hibar, Derrek P; Ching, Christopher R K; Boyle, Christina P; Rajagopalan, Priya; Gutman, Boris A; Leow, Alex D; Toga, Arthur W; Jack, Clifford R; Harvey, Danielle; Weiner, Michael W; Thompson, Paul M

2013-02-15

103

Unbiased and Mobile Gait Analysis Detects Motor Impairment in Parkinson's Disease  

PubMed Central

Motor impairments are the prerequisite for the diagnosis in Parkinson's disease (PD). The cardinal symptoms (bradykinesia, rigor, tremor, and postural instability) are used for disease staging and assessment of progression. They serve as primary outcome measures for clinical studies aiming at symptomatic and disease modifying interventions. One major caveat of clinical scores such as the Unified Parkinson Disease Rating Scale (UPDRS) or Hoehn&Yahr (H&Y) staging is its rater and time-of-assessment dependency. Thus, we aimed to objectively and automatically classify specific stages and motor signs in PD using a mobile, biosensor based Embedded Gait Analysis using Intelligent Technology (eGaIT). eGaIT consist of accelerometers and gyroscopes attached to shoes that record motion signals during standardized gait and leg function. From sensor signals 694 features were calculated and pattern recognition algorithms were applied to classify PD, H&Y stages, and motor signs correlating to the UPDRS-III motor score in a training cohort of 50 PD patients and 42 age matched controls. Classification results were confirmed in a second independent validation cohort (42 patients, 39 controls). eGaIT was able to successfully distinguish PD patients from controls with an overall classification rate of 81%. Classification accuracy increased with higher levels of motor impairment (91% for more severely affected patients) or more advanced stages of PD (91% for H&Y III patients compared to controls), supporting the PD-specific type of analysis by eGaIT. In addition, eGaIT was able to classify different H&Y stages, or different levels of motor impairment (UPDRS-III). In conclusion, eGaIT as an unbiased, mobile, and automated assessment tool is able to identify PD patients and characterize their motor impairment. It may serve as a complementary mean for the daily clinical workup and support therapeutic decisions throughout the course of the disease.

Klucken, Jochen; Barth, Jens; Kugler, Patrick; Schlachetzki, Johannes; Henze, Thore; Marxreiter, Franz; Kohl, Zacharias; Steidl, Ralph; Hornegger, Joachim; Eskofier, Bjoern; Winkler, Juergen

2013-01-01

104

Unbiased tensor-based morphometry: Improved robustness and sample size estimates for Alzheimer's disease clinical trials  

PubMed Central

Various neuroimaging measures are being evaluated for tracking Alzheimer’s disease (AD) progression in therapeutic trials, including measures of structural brain change based on repeated scanning of patients with magnetic resonance imaging (MRI). Methods to compute brain change must be robust to scan quality. Biases may arise if any scans are thrown out, as this can lead to the true changes being overestimated or underestimated. Here we analyzed the full MRI dataset from the first phase of Alzheimer’s Disease Neuroimaging Initiative (ADNI-1) from the first phase of Alzheimer’s Disease Neuroimaging Initiative (ADNI-1) and assessed several sources of bias that can arise when tracking brain changes with structural brain imaging methods, as part of a pipeline for tensor-based morphometry (TBM). In all healthy subjects who completed MRI scanning at screening, 6, 12, and 24 months, brain atrophy was essentially linear with no detectable bias in longitudinal measures. In power analyses for clinical trials based on these change measures, only 39 AD patients and 95 mild cognitive impairment (MCI) subjects were needed for a 24-month trial to detect a 25% reduction in the average rate of change using a two-sided test (?=0.05, power=80%). Further sample size reductions were achieved by stratifying the data into Apolipoprotein E (ApoE) ?4 carriers versus non-carriers. We show how selective data exclusion affects sample size estimates, motivating an objective comparison of different analysis techniques based on statistical power and robustness. TBM is an unbiased, robust, high-throughput imaging surrogate marker for large, multi-site neuroimaging studies and clinical trials of AD and MCI.

Hua, Xue; Hibar, Derrek P.; Ching, Christopher R.K.; Boyle, Christina P.; Rajagopalan, Priya; Gutman, Boris A.; Leow, Alex D.; Toga, Arthur W.; Jack, Clifford R.; Harvey, Danielle; Weiner, Michael W.; Thompson, Paul M.

2013-01-01

105

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.

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

2011-01-01

106

Prediction of Complex Human Traits Using the Genomic Best Linear Unbiased Predictor  

PubMed Central

Despite important advances from Genome Wide Association Studies (GWAS), for most complex human traits and diseases, a sizable proportion of genetic variance remains unexplained and prediction accuracy (PA) is usually low. Evidence suggests that PA can be improved using Whole-Genome Regression (WGR) models where phenotypes are regressed on hundreds of thousands of variants simultaneously. The Genomic Best Linear Unbiased Prediction (G-BLUP, a ridge-regression type method) is a commonly used WGR method and has shown good predictive performance when applied to plant and animal breeding populations. However, breeding and human populations differ greatly in a number of factors that can affect the predictive performance of G-BLUP. Using theory, simulations, and real data analysis, we study the performance of G-BLUP when applied to data from related and unrelated human subjects. Under perfect linkage disequilibrium (LD) between markers and QTL, the prediction R-squared (R2) of G-BLUP reaches trait-heritability, asymptotically. However, under imperfect LD between markers and QTL, prediction R2 based on G-BLUP has a much lower upper bound. We show that the minimum decrease in prediction accuracy caused by imperfect LD between markers and QTL is given by (1?b)2, where b is the regression of marker-derived genomic relationships on those realized at causal loci. For pairs of related individuals, due to within-family disequilibrium, the patterns of realized genomic similarity are similar across the genome; therefore b is close to one inducing small decrease in R2. However, with distantly related individuals b reaches very low values imposing a very low upper bound on prediction R2. Our simulations suggest that for the analysis of data from unrelated individuals, the asymptotic upper bound on R2 may be of the order of 20% of the trait heritability. We show how PA can be enhanced with use of variable selection or differential shrinkage of estimates of marker effects.

de los Campos, Gustavo; Vazquez, Ana I.; Fernando, Rohan; Klimentidis, Yann C.; Sorensen, Daniel

2013-01-01

107

Predicting genetic values: a kernel-based best linear unbiased prediction with genomic data.  

PubMed

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

2011-07-01

108

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.

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

2010-01-01

109

An Unbiased Assessment of the Role of Imprinted Genes in an Intergenerational Model of Developmental Programming  

PubMed Central

Environmental factors during early life are critical for the later metabolic health of the individual and of future progeny. In our obesogenic environment, it is of great socioeconomic importance to investigate the mechanisms that contribute to the risk of metabolic ill health. Imprinted genes, a class of functionally mono-allelic genes critical for early growth and metabolic axis development, have been proposed to be uniquely susceptible to environmental change. Furthermore, it has also been suggested that perturbation of the epigenetic reprogramming of imprinting control regions (ICRs) may play a role in phenotypic heritability following early life insults. Alternatively, the presence of multiple layers of epigenetic regulation may in fact protect imprinted genes from such perturbation. Unbiased investigation of these alternative hypotheses requires assessment of imprinted gene expression in the context of the response of the whole transcriptome to environmental assault. We therefore analyse the role of imprinted genes in multiple tissues in two affected generations of an established murine model of the developmental origins of health and disease using microarrays and quantitative RT–PCR. We demonstrate that, despite the functional mono-allelicism of imprinted genes and their unique mechanisms of epigenetic dosage control, imprinted genes as a class are neither more susceptible nor protected from expression perturbation induced by maternal undernutrition in either the F1 or the F2 generation compared to other genes. Nor do we find any evidence that the epigenetic reprogramming of ICRs in the germline is susceptible to nutritional restriction. However, we propose that those imprinted genes that are affected may play important roles in the foetal response to undernutrition and potentially its long-term sequelae. We suggest that recently described instances of dosage regulation by relaxation of imprinting are rare and likely to be highly regulated.

Radford, Elizabeth J.; Isganaitis, Elvira; Jimenez-Chillaron, Josep; Schroeder, Joshua; Molla, Michael; Andrews, Simon; Didier, Nathalie; Charalambous, Marika; McEwen, Kirsten; Marazzi, Giovanna; Sassoon, David; Patti, Mary-Elizabeth; Ferguson-Smith, Anne C.

2012-01-01

110

Unbiased Review of Digital Diagnostic Images in Practice: Informatics Prototype and Pilot Study  

PubMed Central

Rationale and Objectives Clinical and contextual information associated with images may influence how radiologists draw diagnostic inferences, highlighting the need to control multiple sources of bias in the methodological design of investigations involving radiological interpretation. In the past, manual control methods to mask review films presented in practice have been used to reduce potential interpretive bias associated with differences between viewing images for patient care versus reviewing images for purposes of research, education, and quality improvement. These manual precedents from the film era raise the question whether similar methods to reduce bias can be implemented in the modern digital environment. Materials and Methods We built prototype “CreateAPatient” information technology for masking review case presentations within our institution’s production Radiology Information and Picture Archiving and Reporting Systems (RIS and PACS). To test whether CreateAPatient could be used to mask review images presented in practice, six board-certified radiologists participated in a pilot study. During pilot testing, seven digital chest radiographs, known to contain lung nodules and associated with fictitious patient identifiers, were mixed into the routine workload of the participating radiologists while they covered general evening call shifts. We tested whether it was possible to mask the presentation of these review cases, both by probing the interpreting radiologists to report detection and by conducting a forced-choice experiment on a separate cohort of 20 radiologists and information technology professionals. Results None of the participating radiologists reported awareness of review activity, and forced-choice detection was less than predicted at chance, suggesting radiologists were effectively blinded. In addition, we identified no evidence of review reports unsafely propagating beyond their intended scope or otherwise interfering with patient care, despite integration of these records within production electronic workflow systems. Conclusion Information technology can facilitate the design of unbiased methods involving professional review of digital diagnostic images.

Fotenos, Anthony F.; Safdar, Nabile M.; Nagy, Paul G.; Mezrich, Reuben; Lewin, Jonathan S.

2013-01-01

111

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

112

Age-related changes in rat cerebellar basket cells: a quantitative study using unbiased stereological methods  

PubMed Central

Cortical cerebellar basket cells are stable postmitotic cells; hence, they are liable to endure age-related changes. Since the cerebellum is a vital organ for the postural control, equilibrium and motor coordination, we aimed to determine the quantitative morphological changes in those interneurons with the ageing process, using unbiased techniques. Material from the cerebellar cortex (Crus I and Crus II) was collected from female rats aged 2, 6, 9, 12, 15, 18, 21 and 24 mo (5 animals per each age group), fixed by intracardiac perfusion, and processed for transmission electron microscopy, using conventional techniques. Serial semithin sections were obtained (5 blocks from each rat), enabling the determination of the number-weighted mean nuclear volume (by the nucleator method). On ultrathin sections, 25 cell profiles from each animal were photographed. The volume density of the nucleus, ground substance, mitochondria, Golgi apparatus (Golgi) and dense bodies (DB), and the mean surface density of the rough endoplasmic reticulum (RER) were determined, by point counting, using a morphometric grid. The mean total volumes of the soma and organelles and the mean total surface area of the RER [s?N (RER)] were then calculated. The results were analysed with 1-way ANOVA; posthoc pairwise comparisons of group means were performed using the Newman-Keuls test. The relation between age and each of the parameters was studied by regression analysis. Significant age-related changes were observed for the mean volumes of the soma, ground substance, Golgi, DB, and s?N (RER). Positive linear trends were found for the mean volumes of the ground substance, Golgi, and DB; a negative linear trend was found for the s?N (RER). These results indicate that rat cerebellar basket cells endure important age-related changes. The significant decrease in the s?N (RER) may be responsible for a reduction in the rate of protein synthesis. Additionally, it may be implicated in a cascade of events leading to cell damage due to the excitotoxic activity of glutamate, which could interfere in the functioning of the complex cerebellar neuronal network.

HENRIQUE, RUI M. F.; ROCHA, EDUARDO; REIS, ALCINDA; MARCOS, RICARDO; OLIVEIRA, MARIA H.; SILVA, MARIA W.; MONTEIRO, ROGERIO A. F.

2001-01-01

113

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.

2014-01-01

114

The Optically Unbiased Gamma-Ray Burst Host (TOUGH) Survey. I. Survey Design and Catalogs  

NASA Astrophysics Data System (ADS)

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 Ks magnitudes and redshifts. We detect the host galaxies for 80% of the GRBs in the sample, although only 42% have Ks -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? emission line and we can exclude an early indication that Ly? emission is ubiquitous among GRB hosts, but confirm that Ly? is stronger in GRB-selected galaxies than in flux-limited samples of Lyman break galaxies. .

Hjorth, Jens; Malesani, Daniele; Jakobsson, Páll; Jaunsen, Andreas O.; Fynbo, Johan P. U.; Gorosabel, Javier; Krühler, Thomas; Levan, Andrew J.; Micha?owski, Micha? J.; Milvang-Jensen, Bo; Møller, Palle; Schulze, Steve; Tanvir, Nial R.; Watson, Darach

2012-09-01

115

Assessing diet-health relationships using a short-term unbiased dietary instrument: focus on risk models with multiple dietary components  

Cancer.gov

Identify challenges in estimating relationships between a dietary exposure measured by repeated application of a short-term unbiased instrument and a health outcome in a risk model with multiple dietary components. Describe potential approaches to correct for within-person random measurement error in estimating relationships between a dietary exposure measured by a short-term unbiased instrument and a health outcome in a risk model with multiple dietary components.

116

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

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

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

119

REMiner: a tool for unbiased mining and analysis of repetitive elements and their arrangement structures of large chromosomes.  

PubMed

Repetitive elements (REs) constitute a substantial portion of the genomes of human and other species; however, the RE profiles (type, density, and arrangement) within the individual genomes have not been fully characterized. In this study, we developed an RE analysis tool, called REMiner, for a chromosome-wide investigation into the occurrence of individual REs and arrangement of clusters of REs, and REMiner's functional features were examined using the human chromosome Y. The algorithm implemented by REMiner focused on unbiased mining of REs in large chromosomes and data interface within a viewer. The data from the chromosome demonstrated that REMiner is an efficient tool in regard to its capacity for a large query size and the availability of a high-resolution viewer, featuring instant retrieval of alignment data and control of magnification and identity ratio. The chromosome-wide survey identified a diverse population of ordered RE arrangements, which may participate in the genome biology. PMID:21803149

Chung, Byung-Ik; Lee, Kang-Hoon; Shin, Kyung-Seop; Kim, Woo-Chan; Kwon, Deug-Nam; You, Ri-Na; Lee, Young-Kwan; Cho, Kiho; Cho, Dong-Ho

2011-11-01

120

Unbiased Discovery of Interactions at a Control Locus Driving Expression of the Cancer-Specific Therapeutic and Diagnostic Target, Mesothelin  

PubMed Central

Although significant effort is expended on identifying transcripts/proteins that are up-regulated in cancer, there are few reports on systematic elucidation of transcriptional mechanisms underlying such druggable cancer-specific targets. The mesothelin (MSLN) gene offers a promising subject, being expressed in a restricted pattern normally, yet highly overexpressed in almost one-third of human malignancies and a target of cancer immunotherapeutic trials. CanScript, a cis promoter element, appears to control MSLN cancer-specific expression; its related genomic sequences may up-regulate other cancer markers. CanScript is a 20-nt bipartite element consisting of an SP1-like motif and a consensus MCAT sequence. The latter recruits TEAD (TEA domain) family members, which are universally expressed. Exploration of the active CanScript element, especially the proteins binding to the SP1-like motif, thus could reveal cancer-specific features having diagnostic or therapeutic interest. The effcient identification of sequence-specific DNA-binding proteins at a given locus, however, has lagged in biomarker explorations. We used two orthogonal proteomics approaches— unbiased SILAC (stable isotope labeling by amino acids in cell culture)/DNA affnity-capture/mass spectrometry survey (SD-MS) and a large transcription factor protein microarray (TFM)—and functional validation to explore systematically the CanScript interactome. SD-MS produced nine candidates, and TFM, 18. The screens agreed in confirming binding by TEAD proteins and by newly identified NAB1 and NFATc. Among other identified candidates, we found functional roles for ZNF24, NAB1 and RFX1 in MSLN expression by cancer cells. Combined interactome screens yield an effcient, reproducible, sensitive, and unbiased approach to identify sequence-specific DNA-binding proteins and other participants in disease-specific DNA elements.

Ren, Yunzhao R.; Chaerkady, Raghothama; Hu, Shaohui; Wan, Jun; Qian, Jiang; Zhu, Heng; Pandey, Akhilesh; Kern, Scott E.

2013-01-01

121

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.

2014-01-01

122

Crack spectra analysis  

SciTech Connect

Crack spectra derived from velocity data have been shown to exhibit systematics which reflect microstructural and textural differences between samples (Warren and Tiernan, 1980). Further research into both properties and information content of crack spectra have yielded the following: Spectral features are reproducible even at low pressures; certain observed spectral features may correspond to non-in-situ crack populations created during sample retrieval; the functional form of a crack spectra may be diagnostic of the sample's grain texture; hysteresis is observed in crack spectra between up and down pressure runs - it may be due to friction between the faces of closed crack populations.

Tiernan, M.

1980-09-01

123

Universality of velocity spectra  

Microsoft Academic Search

The purpose of this paper is to present unified spectral models for the three-component velocity fluctuations observed in wind-tunnel generated shear flows and in the atmospheric boundary layer. Presently, only empirical models exist whose coefficients are based on the matching of these models with observed spectra. A general spectral model is presented which can be closely matched to velocity spectra

H. W. Tieleman

1995-01-01

124

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

125

Spectra of porphyrins  

Microsoft Academic Search

The review opens by presenting the absorption spectra for three series of porphyrins derived from the basic skeleton: (a) compounds obtained by simple substitution; (b) compounds obtained by reduction of one or more pyrrole rings; and (c) compounds obtained from fusion of aromatic rings onto the basic skeleton. The spectra are discussed in terms of a four orbital model-that is

Martin Gouterman

1961-01-01

126

Optical Spectra of Supernovae  

Microsoft Academic Search

The temporal evolution of the optical spectra of various types of supernovae (SNe) is illustrated, in part to aid observers classifying supernova candidates. Type II SNe are defined by the presence of hydrogen, and they exhibit a very wide variety of photometric and spectroscopic properties. Among hydrogen-deficient SNe (Type I), three subclasses are now known: those whose early-time spectra show

Alexei V. Filippenko

1997-01-01

127

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

2006-07-20

128

Lily Pad Spectra  

NASA Technical Reports Server (NTRS)

The color image on the lower left from the panoramic camera on the Mars Exploration Rover Opportunity shows the 'Lily Pad' bounce-mark area at Meridiani Planum, Mars. This image was acquired on the 3rd sol, or martian day, of Opportunity's mission (Jan.26, 2004). The upper left image is a monochrome (single filter) image from the rover's panoramic camera, showing regions from which spectra were extracted from the 'Lily Pad' area. As noted by the line graph on the right, the green spectra is from the undisturbed surface and the red spectra is from the airbag bounce mark.

2004-01-01

129

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

130

Thermodynamic analysis of spectra  

SciTech Connect

Although random matrix theory had its initial application to neutron resonances, there is a relative scarcity of suitable nuclear data. The primary reason for this is the sensitivity of the standard measures used to evaluate spectra--the spectra must be essential pure (no state with a different symmetry) and complete (no states missing). Additional measures that are less sensitive to these experimental limitations are of significant value. The standard measure for long range order is the {delta}{sub 3} statistic. In the original paper that introduced this statistic, Dyson and Mehta also attempted to evaluate spectra with thermodynamic variables obtained from the circular orthogonal ensemble. We consider the thermodynamic 'internal energy' and evaluate its sensitivity to experimental limitations such as missing and spurious levels. Monte Carlo simulations suggest that the internal energy is less sensitive to mistakes than is {delta}{sub 3}, and thus the internal energy can serve as a addition to the tool kit for evaluating experimental spectra.

Mitchell, G. E. [North Carolina State University, Raleigh, NC 27695 and Triangle Universities Nuclear Laboratory, Durham, NC 27708 (United States); Shriner, J. F. Jr. [Tennessee Technological University, Cookeville, TN 38505 (United States)

2008-04-04

131

Mass spectra of benzylpyridines  

Microsoft Academic Search

The mass spectra of dimethylbenzyl- and dimethyldibenzylpyridines at different ionizing electron energies were investigated. The anomalously low intensities of the molecular ion peaks of 3,4-dibenzylpyridines, as compared with the 2,5-isomers, and the greater probability of the formation of primary (M-2)+ ions in the mass spectra are explained by the synchronous loss of a neutral H2 particle and the formation of

P. B. Terent'ev; R. A. Khmel'nitskii; N. A. Klyuev; A. B. Belikov; V. V. Dorogov

1973-01-01

132

Two Distinct States of the HAMP Domain from Sensory Rhodopsin Transducer Observed in Unbiased Molecular Dynamics Simulations  

PubMed Central

HAMP domain is a ubiquitous module of bacterial and archaeal two-component signaling systems. Considerable progress has been made recently in studies of its structure and conformational changes. However, the mechanism of signal transduction through the HAMP domain is not clear. It remains a question whether all the HAMPs have the same mechanism of action and what are the differences between the domains from different protein families. Here, we present the results of unbiased molecular dynamics simulations of the HAMP domain from the archaeal phototaxis signal transducer NpHtrII. Two distinct conformational states of the HAMP domain are observed, that differ in relative position of the helices AS1 and AS2. The longitudinal shift is roughly equal to a half of an ?-helix turn, although sometimes it reaches one full turn. The states are closely related to the position of bulky hydrophobic aminoacids at the HAMP domain core. The observed features are in good agreement with recent experimental results and allow us to propose that the states detected in the simulations are the resting state and the signaling state of the NpHtrII HAMP domain. To the best of our knowledge, this is the first observation of the same HAMP domain in different conformations. The simulations also underline the difference between AMBER ff99-SB-ILDN and CHARMM22-CMAP forcefields, as the former favors the resting state and the latter favors the signaling state.

Gushchin, Ivan; Gordeliy, Valentin; Grudinin, Sergei

2013-01-01

133

Conformational Sampling and Nucleotide-Dependent Transitions of the GroEL Subunit Probed by Unbiased Molecular Dynamics Simulations  

PubMed Central

GroEL is an ATP dependent molecular chaperone that promotes the folding of a large number of substrate proteins in E. coli. Large-scale conformational transitions occurring during the reaction cycle have been characterized from extensive crystallographic studies. However, the link between the observed conformations and the mechanisms involved in the allosteric response to ATP and the nucleotide-driven reaction cycle are not completely established. Here we describe extensive (in total long) unbiased molecular dynamics (MD) simulations that probe the response of GroEL subunits to ATP binding. We observe nucleotide dependent conformational transitions, and show with multiple 100 ns long simulations that the ligand-induced shift in the conformational populations are intrinsically coded in the structure-dynamics relationship of the protein subunit. Thus, these simulations reveal a stabilization of the equatorial domain upon nucleotide binding and a concomitant “opening” of the subunit, which reaches a conformation close to that observed in the crystal structure of the subunits within the ADP-bound oligomer. Moreover, we identify changes in a set of unique intrasubunit interactions potentially important for the conformational transition.

Skjaerven, Lars; Grant, Barry; Muga, Arturo; Teigen, Knut; McCammon, J. Andrew; Reuter, Nathalie; Martinez, Aurora

2011-01-01

134

Suppression of nonsense-mediated mRNA decay permits unbiased gene trapping in mouse embryonic stem cells  

PubMed Central

An international collaborative project has been proposed to inactivate all mouse genes in embryonic stem (ES) cells using a combination of random and targeted insertional mutagenesis techniques. Random gene trapping will be the first choice in the initial phase, and gene-targeting experiments will then be carried out to individually knockout the remaining ‘difficult-to-trap’ genes. One of the most favored techniques of random insertional mutagenesis is promoter trapping, which only disrupts actively transcribed genes. Polyadenylation (poly-A) trapping, on the other hand, can capture a broader spectrum of genes including those not expressed in the target cells, but we noticed that it inevitably selects for the vector integration into the last introns of the trapped genes. Here, we present evidence that this remarkable skewing is caused by the degradation of a selectable-marker mRNA used for poly-A trapping via an mRNA-surveillance mechanism, nonsense-mediated mRNA decay (NMD). We also report the development of a novel poly-A-trap strategy, UPATrap, which suppresses NMD of the selectable-marker mRNA and permits the trapping of transcriptionally silent genes without a bias in the vector-integration site. We believe the UPATrap technology enables a simple and straightforward approach to the unbiased inactivation of all mouse genes in ES cells.

Shigeoka, Toshiaki; Kawaichi, Masashi; Ishida, Yasumasa

2005-01-01

135

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.

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

2009-01-01

136

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

PubMed

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

2010-01-01

137

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

138

PAH Spectra for Everyone  

NASA Astrophysics Data System (ADS)

The Ames Astrochemistry Laboratory now has PAH IR spectra of more than 220 laboratory measured and over 600 theoretically calculated IR spectra of polycyclic aromatic hydrocarbons (PAHs) in a multitude of forms. The vast majority of these spectra are not readily accessible to the public. We propose to make the full collection of the Ames experimental and computational collection of PAH IR spectra available to the entire Spitzer community and accessible via the World Wide Web (WWW). The laboratory measured mid-IR spectral collection includes over 220 neutral, cationic, and anionic PAHs, PAHs with deuterium in place of hydrogen, PAHs containing oxygen, and PAHs containing nitrogen (PANHs). The formulae of the PAHs in the experimental data collection range from C10H8 to C50H22. Unfortunately, it is not possible to obtain physical samples of all of the types of PAHs that are of astrophysical interest for experimental study. We also have an extensive collection of accurate computational spectra to fill in gaps in the experimentally available spectra. Our theoretical PAH spectral collection includes very large PAHs, PAHs containing 40 to 132 carbon atoms which are comparable to the size of the PAHs thought to dominate the interstellar emission spectrum. Large PAHs might be multiply charged and these are also represented in the theoretical database. There is also observational evidence for PAH cations with nitrogen in the inner rings (PANHs) and interest in the spectroscopy of aromatic species containing oxygen and deuterium as well as PAH metal clusters. All of these types of PAHs are represented in the Ames computational PAH IR spectroscopic collection. If funded, we plan to make our entire inventory of the lab spectra available to the Spitzer community within the next two years.

Allamandola, Louis; Bauschlicher, Charlie, Jr.; Mattioda, Andrew

2007-05-01

139

Best Linear Unbiased Prediction of Genomic Breeding Values Using a Trait-Specific Marker-Derived Relationship Matrix  

PubMed Central

Background With the availability of high density whole-genome single nucleotide polymorphism chips, genomic selection has become a promising method to estimate genetic merit with potentially high accuracy for animal, plant and aquaculture species of economic importance. With markers covering the entire genome, genetic merit of genotyped individuals can be predicted directly within the framework of mixed model equations, by using a matrix of relationships among individuals that is derived from the markers. Here we extend that approach by deriving a marker-based relationship matrix specifically for the trait of interest. Methodology/Principal Findings In the framework of mixed model equations, a new best linear unbiased prediction (BLUP) method including a trait-specific relationship matrix (TA) was presented and termed TABLUP. The TA matrix was constructed on the basis of marker genotypes and their weights in relation to the trait of interest. A simulation study with 1,000 individuals as the training population and five successive generations as candidate population was carried out to validate the proposed method. The proposed TABLUP method outperformed the ridge regression BLUP (RRBLUP) and BLUP with realized relationship matrix (GBLUP). It performed slightly worse than BayesB with an accuracy of 0.79 in the standard scenario. Conclusions/Significance The proposed TABLUP method is an improvement of the RRBLUP and GBLUP method. It might be equivalent to the BayesB method but it has additional benefits like the calculation of accuracies for individual breeding values. The results also showed that the TA-matrix performs better in predicting ability than the classical numerator relationship matrix and the realized relationship matrix which are derived solely from pedigree or markers without regard to the trait. This is because the TA-matrix not only accounts for the Mendelian sampling term, but also puts the greater emphasis on those markers that explain more of the genetic variance in the trait.

Zhang, Zhe; Liu, Jianfeng; Ding, Xiangdong; Bijma, Piter; de Koning, Dirk-Jan; Zhang, Qin

2010-01-01

140

Turn-Directed ?-? Conformational Transition of ?-syn12 Peptide at Different pH Revealed by Unbiased Molecular Dynamics Simulations  

PubMed Central

The transition from ?-helical to ?-hairpin conformations of ?-syn12 peptide is characterized here using long timescale, unbiased molecular dynamics (MD) simulations in explicit solvent models at physiological and acidic pH values. Four independent normal MD trajectories, each 2500 ns, are performed at 300 K using the GROMOS 43A1 force field and SPC water model. The most clustered structures at both pH values are ?-hairpin but with different turns and hydrogen bonds. Turn9-6 and four hydrogen bonds (HB9-6, HB6-9, HB11-4 and HB4-11) are formed at physiological pH; turn8-5 and five hydrogen bonds (HB8-5, HB5-8, HB10-3, HB3-10 and HB12-1) are formed at acidic pH. A common folding mechanism is observed: the formation of the turn is always before the formation of the hydrogen bonds, which means the turn is always found to be the major determinant in initiating the transition process. Furthermore, two transition paths are observed at physiological pH. One of the transition paths tends to form the most-clustered turn and improper hydrogen bonds at the beginning, and then form the most-clustered hydrogen bonds. Another transition path tends to form the most-clustered turn, and turn5-2 firstly, followed by the formation of part hydrogen bonds, then turn5-2 is extended and more hydrogen bonds are formed. The transition path at acidic pH is as the same as the first path described at physiological pH.

Liu, Lei; Cao, Zanxia

2013-01-01

141

Atomic Spectra Database (ASD)  

National Institute of Standards and Technology Data Gateway

SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

142

Quantization noise spectra  

Microsoft Academic Search

Several results describing the behavior of quantization noise in a unified and simplified manner are discussed. Exact formulas for quantizer noise spectra are developed. They are applied to a variety of systems and inputs, including scalar quantization (PCM), dithered PCM, sigma-delta modulation, dithered sigma-delta modulation, two-stage sigma-delta modulation, and second-order sigma-delta modulation

Robert M. Gray

1990-01-01

143

Metagenomic Analysis of Taxa Associated with Lutzomyia longipalpis, Vector of Visceral Leishmaniasis, Using an Unbiased High-Throughput Approach  

PubMed Central

Background Leishmaniasis is one of the most diverse and complex of all vector-borne diseases worldwide. It is caused by parasites of the genus Leishmania, obligate intramacrophage protists characterised by diversity and complexity. Its most severe form is visceral leishmaniasis (VL), a systemic disease that is fatal if left untreated. In Latin America VL is caused by Leishmania infantum chagasi and transmitted by Lutzomyia longipalpis. This phlebotomine sandfly is only found in the New World, from Mexico to Argentina. In South America, migration and urbanisation have largely contributed to the increase of VL as a public health problem. Moreover, the first VL outbreak was recently reported in Argentina, which has already caused 7 deaths and 83 reported cases. Methodology/Principal Findings An inventory of the microbiota associated with insect vectors, especially of wild specimens, would aid in the development of novel strategies for controlling insect vectors. Given the recent VL outbreak in Argentina and the compelling need to develop appropriate control strategies, this study focused on wild male and female Lu. longipalpis from an Argentine endemic (Posadas, Misiones) and a Brazilian non-endemic (Lapinha Cave, Minas Gerais) VL location. Previous studies on wild and laboratory reared female Lu. longipalpis have described gut bacteria using standard bacteriological methods. In this study, total RNA was extracted from the insects and submitted to high-throughput pyrosequencing. The analysis revealed the presence of sequences from bacteria, fungi, protist parasites, plants and metazoans. Conclusions/Significance This is the first time an unbiased and comprehensive metagenomic approach has been used to survey taxa associated with an infectious disease vector. The identification of gregarines suggested they are a possible efficient control method under natural conditions. Ongoing studies are determining the significance of the associated taxa found in this study in a greater number of adult male and female Lu. longipalpis samples from endemic and non-endemic locations. A particular emphasis is being given to those species involved in the biological control of this vector and to the etiologic agents of animal and plant diseases.

McCarthy, Christina B.; Diambra, Luis A.; Rivera Pomar, Rolando V.

2011-01-01

144

Activity: Graphing Spectra  

NSDL National Science Digital Library

This activity introduces two different representations of spectra: the photographic representation, such as the rainbow, and the graphical representation used more often by astronomers. A rainbow is often given as an everyday example of a spectrum. Most students have seen a rainbow, so this example is used to help make the unfamiliar more familiar. However, the spectra that scientists use, which students will see in this lesson plan, appear very different than a rainbow. In this activity, students will explore for themselves two different representations of the same spectrum, noting advantages and disadvantages of each. They will explore the differences and similarities of both these representations, and will develop a more intuitive feel for a graphical representation, which may not yet be familiar to them.

145

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

146

Auroral Colors and Spectra  

NSDL National Science Digital Library

This site, co-produced by the NCAR High Altitude Observatory and the COMET Program, provides an explanation of how auroral colors are produced. The emission of specific colors of light is discussed in relation to oxygen and nitrogen emission spectra. Numerous images, graphs, and a video of an aurora are included. The site is part of "Physics of the Aurora: Earth Systems," an interactive learning module about the aurora.

2007-01-26

147

Martian neutron leakage spectra  

NASA Astrophysics Data System (ADS)

A high-energy nucleon-meson transport code is used to calculate energy spectra of Martian leakage neutrons. Four calculations are used to simulate a uniform surface layer containing various amounts of water, different burial depths of a 50 percent water layer underneath a 1 percent water layer, changing atmospheric pressure, and a thick carbon dioxide ice sheet overlying a "dirty" water ice sheet. Calculated spectra at energies less than about 1000 eV were fitted by a superposition of thermal and epithermal functions having four free parameters, two of which (thermal and epithermal amplitudes) were found to vary systematically and to specify uniquely the configuration in each of the series. Parameter variations depend on the composition of the assumed surface layers through the average atomic mass and the macroscopic scattering and absorption cross sections. It is concluded that measurements of leakage neutron spectra should allow determination of the hydrogen content of surface layers buried to depths up to about 100 g/sq. cm and determination of the thickness of a polar dry ice cap up to a thickness of about 250 g/sq. cm.

Drake, D. M.; Feldman, W. C.; Jakosky, B. M.

1988-06-01

148

Classification of single-voxel 1H spectra of brain tumours using LCModel.  

PubMed

This study presents a novel method for the direct classification of (1)H single-voxel MR brain tumour spectra using the widespread analysis tool LCModel. LCModel is designed to estimate individual metabolite proportions by fitting a linear combination of in?vitro metabolite spectra to an in?vivo MR spectrum. In this study, it is used to fit representations of complete tumour spectra and to perform a classification according to the highest estimated tissue proportion. Each tumour type is represented by two spectra, a mean component and a variability term, as calculated using a principal component analysis of a training dataset. In the same manner, a mean component and a variability term for normal white matter are also added into the analysis to allow a mixed tissue approach. An unbiased evaluation of the method is carried out through the automatic selection of training and test sets using the Kennard and Stone algorithm, and a comparison of LCModel classification results with those of the INTERPRET Decision Support System (IDSS) which incorporates an advanced pattern recognition method. In a test set of 46 spectra comprising glioblastoma multiforme, low-grade gliomas and meningiomas, LCModel gives a classification accuracy of 90% compared with an accuracy of 95% by IDSS. PMID:21796709

Raschke, F; Fuster-Garcia, E; Opstad, K S; Howe, F A

2012-02-01

149

[Raman spectra of pyroxene].  

PubMed

By testing the Raman spectra of megacryst pyroxene, enstatite and diopside in terms of location, shape and intensity, the symmetries of the main spectral band of pyroxene and the vibration modes of Raman shift were identified. The spectral bands of corresponding ionic groups such as non-bridge oxygen Si-O- and bridge oxygen Si-O0, O-Si-O and M-O were assigned for vibrational mode. Through the change in the intensity of the spectral band in different section direction and the deficiency of some spectral bands, the orientation problem in mineral crystallography was preliminarily studied. PMID:20384128

Wang, Rong; Zhang, Bao-Min

2010-02-01

150

Theoretical Studies of Molecular Spectra  

NASA Technical Reports Server (NTRS)

This summary describes the research activities of the principal investigator during the reporting period. The research includes spectroscopy, management of molecular databases, and generation of spectral line profiles and opacity data. The spectroscopy research includes oxygen broadening of nitric oxide (NO), analysis of CO2 spectra, analysis of HNO3 spectra, and analysis of CO spectra.

McKay, Christopher (Technical Monitor); Freedman, Richard S.

2002-01-01

151

DISPLACEMENT SPECTRA FOR SEISMIC DESIGN  

Microsoft Academic Search

Displacement-based seismic design and assessment of structures require the reliable definition of displacement spectra for a wide range of periods and damping levels. The displacement spectra derived from acceleration spectra in existing seismic codes do not provide a suitable answer and there are no existing frequency-dependent attenuation relationships derived specifically for this purpose. Using a carefully processed dataset of European

JULIAN J. BOMMER; AMR S. ELNASHAI

1999-01-01

152

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

153

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

154

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

155

Modeling Supernova Spectra  

NASA Astrophysics Data System (ADS)

We highlight results from a series of investigations into modeling spectra of core-collapse supernovae (SNe). We have explored the accuracy of the expanding-photosphere method, and found that it can be used to obtain distances to Type IIP SNe with an accuracy of <~10%. We confirm the result of Utrobin and Chugai (2005) that time-dependent terms must be included in the statistical equilibrium equations in order to model Hi line evolution in Type II SNe, and show that time-dependent terms influence other spectral features (e.g., He i lines). We have initiated a study of polarization signatures from aspherical but axially-symmetric Type II SN ejecta. Hillier and Li acknowledge support from STScI theory grant HST-AR-11756.01.A and NASA theory grant NNX10AC80G. Dessart acknowledges financial support from grant PIRG04-GA-2008-239184.

Hillier, D. John; Dessart, Luc; Li, Chendong

2012-04-01

156

Unbiased photoelectrochemical water splitting in Z-scheme device using W/Mo-doped BiVO4 and Zn(x)Cd(1-x)Se.  

PubMed

Photoelectrochemical water splitting to generate H2 and O2 using only photon energy (with no added electrical energy) has been demonstrated with dual n-type-semiconductor (or Z-scheme) systems. Here we investigated two different Z-scheme systems; one is comprised of two cells with the same metal-oxide semiconductor (W- and Mo-doped bismuth vanadate), that is, Pt-W/Mo-BiVO4, and the other is comprised of the metal oxide and a chalcogenide semiconductor, that is, Pt-W/Mo-BiVO4 and Zn(0.2)Cd(0.8)Se. The redox couples utilized in these Z-scheme configurations were I(-)/IO3(-) or S(2-)/S(n)(2-), respectively. An electrochemical analysis of the system in terms of cell components is shown to illustrate the behavior of the complete photoelectrochemical Z-scheme water-splitting system. H2 gas from the unbiased photolysis of water was detected using gas chromatography-mass spectroscopy and using a membrane-electrode assembly. The electrode configuration to achieve the maximum conversion efficiency from solar energy to chemical energy with the given materials and the Z-scheme is discussed. Here, the possibilities and challenges of Z-scheme unbiased photoelectrochemical water-splitting devices and the materials to achieve practical solar-fuel generation are discussed. PMID:23494937

Park, Hyun S; Lee, Heung Chan; Leonard, Kevin C; Liu, Guanjie; Bard, Allen J

2013-07-22

157

Hybrid estimation of cosmic microwave background polarization power spectra  

NASA Astrophysics Data System (ADS)

This paper generalizes the hybrid power spectrum estimation method developed in a previous paper to the estimation of polarization power spectra of the cosmic microwave background radiation. The hybrid power spectrum estimator is unbiased and we show that it is close to optimal at all multipoles, provided the pixel noise satisfies certain constraints. Furthermore, the hybrid estimator is computationally fast and can easily be incorporated in a Monte Carlo chain for Planck-sized data sets, which may be essential to account for realistic noise covariance and systematic errors. Simple formulae are given for the covariance matrices, including uncorrelated inhomogeneous instrumental noise, and these are tested extensively against numerical simulations. We compare the behaviour of simple pseudo-Cl (PCL) estimates with maximum-likelihood estimates at low multipoles. For realistic sky cuts, maximum-likelihood estimates reduce very significantly the mixing of E and B modes. To achieve limits on the scalar-tensor ratio of r << 0.1 from sky maps with realistic sky cuts, maximum-likelihood methods, or PCL estimators based on unambiguous E and B modes, will be essential.

Efstathiou, G.

2006-07-01

158

Development of fatigue loading spectra  

SciTech Connect

The present work on fatigue-loading spectra encompasses the current status of standardized stress-time histories, European approaches to standard loading spectrum development, transport aircraft airframe fatigue test spectra, the TURBISTAN fatigue-loading standard for fighter-aircraft engine disks, an automated procedure for the creation of flight-by-flight spectra, and the development of a wave-action standard history for fatigue testing relevant to tubular structures in the North Sea. Also treated is the use of the TURBISTAN mission spectra to evaluate fatigue crack growth in a rotating disk, fatigue-spectra development for airborne stores, a simplified analysis of fatigue-loading spectra, variable-amplitude load models for fatigue-damage crack growth, the tracking time service histories for multiaxis fatigue problems, and the compilation of procedures for fatigue crack propagation testing under complex load sequences.

Potter, J.M.; Watanabe, R.T.

1989-01-01

159

EPR spectra of trigonal clusters  

NASA Astrophysics Data System (ADS)

A theory of EPR spectra of trinuclear antiferromagnetic clusters having near trigonal symmetry ( D3 n) is described. It is shown that low-temperature EPR spectra of polycrystalline clusters involving paramagnetic ions with half-integer spins and quenched orbital motion may be applied to estimate molecular g factors, degrees of symmetry lowering, and antisymmetric exchange parameters. The theory is applied to interpret the EPR spectra of trinuclear iron acetate.

Rakitin, Yu. V.; Yablokov, Yu. V.; Zelentsov, V. V.

160

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

161

IRAS LRS Spectra of Asteroids  

NASA Astrophysics Data System (ADS)

Optical and 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. To remedy this paucity of mid-infrared spectra we have searched the original Dutch (Groningen) archive of 171,000 7.7-22.7 micron spectra from the IRAS Low Resolution Spectrometer (LRS), for point sources brighter than 1.5 Jy at 12 or 25 microns. Our pilot study based on 4000 numbered asteroids has already found several hundred valid spectra of about 100 different asteroids. We anticipate finding a few thousand relevant spectra from a complete study applied to all currently numbered asteroids. We present the results of analysis of our pilot study. The process was to extract and recalibrate the LRS spectra; divide the spectra by the best-fitting thermal continua calculated from Standard Thermal Models and/or Thermophysical Models to enhance any spectral features (emission or absorption), group the asteroid spectra initially by optical taxonomic class, co-add the spectra by class, and search for any patterns of mid-infrared spectral features. We discuss recognizable spectral features that appear to be diagnostic of at least families of minerals, and investigate the prospects for an infrared thermal taxonomic classification of asteroids.

Walker, R. G.; Cohen, M.

1999-12-01

162

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

163

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

164

Finite-field method with unbiased polarizable continuum model for evaluation of the second hyperpolarizability of an open-shell singlet molecule in solvents.  

PubMed

The static second hyperpolarizability ? of the complexes composed of open-shell singlet 1,3-dipole molecule involving a boron atom and a water molecule in aqueous phase are investigated by the finite-field (FF) method combined with a standard polarized continuum model (PCM) and with a newly proposed unbiased PCM (UBPCM). On the basis of the comparison with the results calculated by the FF method using the full quantum and the quantum-mechanical/molecular-mechanical and molecular-dynamics (QM/MM-MD) treatments, the present FF-UBPCM method is demonstrated to remedy the artificial overestimation of the ? caused by standard FF-PCM calculations and to well reproduce the FF-QM/MM-MD and FF-full-QM results with much lower costs. PMID:23913641

Inui, Tomoya; Shigeta, Yasuteru; Okuno, Katsuki; Baba, Takeshi; Kishi, Ryohei; Nakano, Masayoshi

2013-10-15

165

Using Regression Calibration Equations That Combine Self-Reported Intake and Biomarker Measures to Obtain Unbiased Estimates and More Powerful Tests of Dietary Associations  

PubMed Central

The authors describe a statistical method of combining self-reports and biomarkers that, with adequate control for confounding, will provide nearly unbiased estimates of diet-disease associations and a valid test of the null hypothesis of no association. The method is based on regression calibration. In cases in which the diet-disease association is mediated by the biomarker, the association needs to be estimated as the total dietary effect in a mediation model. However, the hypothesis of no association is best tested through a marginal model that includes as the exposure the regression calibration-estimated intake but not the biomarker. The authors illustrate the method with data from the Carotenoids and Age-Related Eye Disease Study (2001--2004) and show that inclusion of the biomarker in the regression calibration-estimated intake increases the statistical power. This development sheds light on previous analyses of diet-disease associations reported in the literature.

Freedman, Laurence S.; Midthune, Douglas; Carroll, Raymond J.; Tasevska, Natasa; Schatzkin, Arthur; Mares, Julie; Tinker, Lesley; Potischman, Nancy; Kipnis, Victor

2011-01-01

166

Unveiling the Intrinsic X-Ray Properties of Broad Absorption Line Quasars with a Relatively Unbiased Sample  

NASA Astrophysics Data System (ADS)

There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs at z ~ 2, selected from a near-infrared (Two Micron All Sky Survey) sample, where the BALQSO fraction is likely to be close to the intrinsic fraction. We measure photon indices using the stacked spectra of the optically faint (i – Ks >= 2.3 mag) and optically bright (i – Ks < 2.3 mag) samples to be ? ~= 1.5-2.1. We constrain their intrinsic column density by modeling the X-ray fractional hardness ratio, finding a mean column density of 3.5 × 1022 cm–2 assuming neutral absorption. We incorporate Sloan Digital Sky Survey optical measurements (rest frame UV) to study the broadband spectral index between the X-ray and UV bands, and compare this to a large sample of normal quasars. We estimate that the optically faint BALQSOs are X-ray weaker than the optically bright ones, and the entire sample of BALQSOs are intrinsically X-ray weak when compared to normal active galactic nuclei (AGNs). Correcting for magnification of X-ray emission via gravitational lensing by the central black hole viewed at large inclination angles makes these BALQSOs even more intrinsically X-ray weak. Finally, we estimate AGN kinetic feedback efficiencies of a few percent for an X-ray wind of 0.3c in high-ionization BALQSOs. Combined with energy carried by low-ionization BALQSOs and UV winds, the total kinetic energy in BALQSOs can be sufficient to provide AGN kinetic feedback required to explain the co-evolution between black holes and host galaxies.

Morabito, Leah K.; Dai, Xinyu; Leighly, Karen M.; Sivakoff, Gregory R.; Shankar, Francesco

2014-05-01

167

? Bootis stars with composite spectra  

NASA Astrophysics Data System (ADS)

We examine the large sample of ? Boo candidates collected in Table 1 of Gerbaldi et al. (\\cite{Gerbaldi2003}) to see how many of them show composite spectra. Of the 132 ? Boo candidates we identify 22 which definitely show composite spectra and 15 more for which there are good reasons to suspect a composite spectrum. The percentage of ? Boo candidates with composite spectra is therefore >17% and possibly considerably higher. For such stars the ? Boo classification should be reconsidered taking into account the fact that their spectra are composite. We argue that some of the underabundances reported in the literature may simply be the result of the failure to consider the composite nature of the spectra. This leads to the legitimate suspicion that some, if not all, the ? Boo candidates are not chemically peculiar at all. A thorough analysis of even a single one of the ? Boo candidates with composite spectra, in which the composite nature of the spectrum is duly considered, which would demonstrate that the chemical peculiarities persist, would clear the doubt we presently have that the stars with composite spectra may not be ? Boo stars at all. Based on observations collected at ESO (Echelec spectrograph) and at TBL (Telescope Bernard Lyot) of the Pic du Midi Observatory (France).

Faraggiana, R.; Bonifacio, P.; Caffau, E.; Gerbaldi, M.; Nonino, M.

2004-10-01

168

Spectra of Irradiated Giant Planets  

Microsoft Academic Search

As many as 101 extrasolar giant planets (EGPs) have been detected by radial-velocity techniques, but none has been detected directly by its own emission or by reflection of the light from its parent star. We review the current state-of-the-art in the theoretical modeling of the spectra of giant planets outside the solar system and the basic theory of EGP spectra

Adam Burrows; David Sudarsky

2002-01-01

169

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

170

FISA: Fast Integrated Spectra Analyzer  

NASA Astrophysics Data System (ADS)

FISA (Fast Integrated Spectra Analyzer) permits fast and reasonably accurate age and reddening determinations for small angular diameter open clusters by using their integrated spectra in the (3600-7400) AA range and currently available template spectrum libraries. This algorithm and its implementation help to achieve astrophysical results in shorter times than from other methods. FISA has successfully been applied to integrated spectroscopy of open clusters, both in the Galaxy and in the Magellanic Clouds, to determine ages and reddenings.

Benítez-Llambay, Alejandro

2012-02-01

171

Broadband millimeter-wave spectroscopy with Z-Spec: an unbiased molecular-line survey of the starburst galaxy M82  

NASA Astrophysics Data System (ADS)

Z-Spec is a broadband, millimeter-wave, direct-detection spectrometer based on a novel waveguide grating architecture. It is designed to fully cover the wide one-millimeter atmospheric window with a frequency range of 186 to 307 GHz at a resolution of ~ 250. The design goal is the detection of rotational and fine structure lines from the distant population of galaxies that make up the far-infrared background. Its large instantaneous bandwidth enables detection of multiple transitions of carbon monoxide and a relatively rapid determination of redshift. The grating design is based on the Rowland architecture but is much more compact because of the use of a parallel-plate waveguide propagation medium. Z-Spec uses 160 silicon nitride micromesh bolometers and is cooled to less than 100 mK to achieve background-limited performance. Moreover, Z-Spec serves as a technology demonstration of a technique that is uniquely suited to far-infrared extragalactic spectroscopy from space. Z-Spec's capabilities enable wide-coverage, unbiased line surveys of nearby galaxies. Searches for molecular lines outside our own galaxy have typically been targeted at specific transitions of particular molecules. The brightest sources of extra-galactic molecular lines come from galaxies with physical conditions very different from those found in the Milky Way. Unbiased searches for spectral lines can discover transitions and molecules that are unexpected. A three-pointing study of the prototypical starburst galaxy M82 was performed with Z-Spec at the Caltech Submillimeter Observatory. The survey detected eleven bright lines in the center of the Z-Spec band, of which four had not been previously detected. Two of the new detections are for molecules that had been detected at lower frequencies (HNC 3 - 2 and C2H 3 - 2) and the other two are potentially transitions of SO2, for which only upper limits on lower frequency transitions were previously available. Several detected molecules are analyzed using a large-velocity-gradient (LVG) radiative-transfer model and indicate significant regions of high-density molecular gas along the major axis of M82.

Naylor, Bret J.

2008-06-01

172

Thermal Emission Spectra of Mercury  

NASA Technical Reports Server (NTRS)

The emission spectrum of Mercury may hold clues as to the mineral composition of the surface from reststrahlen bands. Unfortunately, these bands are very weak in finely powdered materials, such as are expected on the mercurian surface, and they lie in a region of the spectrum where there are substantial atmospheric absorptions. We have been measuring the 8-14-micron spectra of Mercury and the Sun at a resolution of about 0.03 wavenumbers, using the Fourier Transform Spectrometer (FTS) located at the National Solar Observatory, Kitt Peak, Arizona. The objective of using such a high resolution for the measurement is to be able to look between atmospheric absorption lines as much as possible. The atmospheric effects are largely cancelled by ratioing Mercury spectra to Sun spectra taken at nearly the same airmass, although small differences in airmass produce some residual atmospheric absorptions in the ratio spectra. We expect that spectral features of Mercury, if any, should appear in the ratio spectra, since the 8-14 micron spectrum of the Sun approximates a black body.

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

1999-01-01

173

Analysis of photometric spectra of 17 meteors  

NASA Technical Reports Server (NTRS)

The initial phase of the photometry which involved 17 meteor spectra consisting of eight Geminid spectra, six Orionid spectra and three Eta Aquarid spectra is discussed. Among these 17 spectra it is found that the Geminid spectra are of the best quality and are used for the identification of the atomic lines and molecular bands that normally appear on video tape spectra. The data from the Geminid records are used for developing calibration techniques in photometry. The Orionid and Eta Aquarid spectra are chosen for early analysis because of the current interest in all physical and chemical data relating to Comet Halley.

Millman, P. M.

1982-01-01

174

Using an incremental mean first passage approach to explore the viscosity dependent dynamics of the unbiased translocation of a polymer through a nanopore  

NASA Astrophysics Data System (ADS)

Noting the limitations of the standard characterization of translocation dynamics, an incremental mean first passage process methodology is used to more completely map the unbiased translocation of a polymer through a nanopore. In this approach, the average time t0 required to reach successively increasing displacements for the first time is recorded - a measure shown to be more commensurate with the mean first passage nature of translocation. Applying this methodology to the results of Langevin dynamics simulations performed in three dimensions across a range of viscosities, a rich set of dynamics spanning regular diffusion at low viscosities to sub-diffusion at higher viscosities is revealed. Further, while the scaling of the net translocation time ? with polymer length N is shown to be viscosity-dependent, common regimes are found across all viscosities: super-diffusive behaviour at short times, an N-independent backbone consistent with ? ~ N2.0 at low viscosities and ? ~ N2.2 at higher viscosities for intermediate times, and N-dependent deviations from the backbone near the completion of translocation.

de Haan, Hendrick W.; Slater, Gary W.

2012-05-01

175

Genomic predictions across Nordic Holstein and Nordic Red using the genomic best linear unbiased prediction model with different genomic relationship matrices.  

PubMed

This study investigated genomic predictions across Nordic Holstein and Nordic Red using various genomic relationship matrices. Different sources of information, such as consistencies of linkage disequilibrium (LD) phase and marker effects, were used to construct the genomic relationship matrices (G-matrices) across these two breeds. Single-trait genomic best linear unbiased prediction (GBLUP) model and two-trait GBLUP model were used for single-breed and two-breed genomic predictions. The data included 5215 Nordic Holstein bulls and 4361 Nordic Red bulls, which was composed of three populations: Danish Red, Swedish Red and Finnish Ayrshire. The bulls were genotyped with 50 000 SNP chip. Using the two-breed predictions with a joint Nordic Holstein and Nordic Red reference population, accuracies increased slightly for all traits in Nordic Red, but only for some traits in Nordic Holstein. Among the three subpopulations of Nordic Red, accuracies increased more for Danish Red than for Swedish Red and Finnish Ayrshire. This is because closer genetic relationships exist between Danish Red and Nordic Holstein. Among Danish Red, individuals with higher genomic relationship coefficients with Nordic Holstein showed more increased accuracies in the two-breed predictions. Weighting the two-breed G-matrices by LD phase consistencies, marker effects or both did not further improve accuracies of the two-breed predictions. PMID:24750283

Zhou, L; Lund, M S; Wang, Y; Su, G

2014-08-01

176

Reduction of multielement mass spectra  

SciTech Connect

Even though the spectra obtained by inductively coupled plasma source spectrometry (ICP-MS) are relatively simple, their interpretation can be complicated by the presence of molecular and isobaric interferants. To the extent that isotopic abundances are known and constant, one can treat observed spectra as sums of known components. A linear decomposition approach for determining the concentrations of the components in a spectrum and correctly propagating uncertainties is presented. This technique differs from linear regression in that an exact fit is made to a subset of isotopes and goodness-of-fit is evaluated from the deviations between the predicted and measured intensities of the other, unfit isotopes. This technique can be applied to a wide range of spectral fitting problems. In this paper, its applicability to ICP-MS spectra is used to demonstrate the use and utility of the technique. 2 refs., 9 figs.

Russ, G.P. III; Caffee, M.W.; Hudson, G.B.; Storch, N.A.

1990-06-29

177

State equations for nonrational spectra  

NASA Astrophysics Data System (ADS)

This paper develops an infinite dimensional theory for filtering and control in the presence of non-rational spectra. It begins with a review of the original work of A.V. Balakrishnan for the continues time case. This work formulates an auxiliary state space signal model for the case of non-rational spectra. The result is the recovery of Kalman like signal generation models with the resulting separation principle for control. New results, based on unpublished notes of Balakrishnan, on discretization of the model are developed. Although the results can and will be generalized, this paper only covers the 1D theory.

Washburn, Donald C.

1999-08-01

178

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

179

Inference of Site Frequency Spectra From High-Throughput Sequence Data: Quantification of Selection on Nonsynonymous and Synonymous Sites in Humans  

PubMed Central

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.

Keightley, Peter D.; Halligan, Daniel L.

2011-01-01

180

Computer Simulation of NMR Spectra.  

ERIC Educational Resources Information Center

Describes a PASCAL computer program which provides interactive analysis and display of high-resolution nuclear magnetic resonance (NMR) spectra from spin one-half nuclei using a hard-copy or monitor. Includes general and theoretical program descriptions, program capability, and examples of its use. (Source for program/documentation is included.)…

Ellison, A.

1983-01-01

181

The LickX spectra  

NASA Astrophysics Data System (ADS)

Context. Collections of stellar spectra, often called stellar libraries, are useful in a variety of applications in the field of stellar populations. Aims: This is an attempt to improve the much-used Lick library of stellar spectra by removing jitter from the wavelength scale via cross-correlation, and calling the result the LickX library. Methods: Each spectrum was cross-correlated with a template spectrum and a new wavelength solution sought. Low-order polynomials were fit to adjust the old scale to a new fit. Indices were measured, new standard star averages found, and adjusted averages derived for the program stars. Results: The greatest gains in accuracy are expected for the fainter stars and stars of extreme surface temperatures; the bright K giant standard stars in LickX have the same uncertainties as Lick. The spectra and a table of index measurements in which repeated measurements are averaged are made available electronically. Individual stellar spectra, in FITS files, and the ascii catalog of absorption feature index strengths are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A36

Worthey, G.; Danilet, A. B.; Faber, S. M.

2014-01-01

182

cloud supersaturations and CCN spectra  

NASA Astrophysics Data System (ADS)

Multiple regression analysis predictions of low altitude cloud droplet concentrations based on measured CCN spectra compared much better with measured low altitude droplet concentrations than various CCN concentrations at single supersaturations (S) in two aircraft cumulus cloud projects, RICO and ICE-T. The addition of vertical velocity (W) to the single and multiple regressions showed small improvements. For RICO the multiple regression correlations were also superior to previous adiabatic model predictions of droplet concentrations also based on CCN spectra and mean W. More adiabatic cloud parcels showed only slightly better correlations than flight-averaged droplet concentrations. Results show the value of more extensive CCN spectra and the relative unimportance of W variations for determining droplet concentrations in these Caribbean cumuli. The fact that flight-averaged droplet concentrations of all low cloud data was almost as well correlated with CCN spectra as were droplet concentrations of more adiabatic cloud parcels indicates that entrainment did not significantly perturb CCN-droplet concentration relationships. As should be expected higher cloud S were determined for the cumulus clouds than for stratus clouds. Suppression of cloud S by higher CCN concentrations that had previously been observed in stratus was observed in ICE-T but not in RICO where the CCN range may have been too low for cloud S suppression. But ICE-T and a stratus project, POST, even showed this S suppression over the same limited maritime CCN range as RICO.

Hudson, James; Noble, Stephen

2014-05-01

183

On Spectra of Starlike Graphs  

Microsoft Academic Search

In the present paper we show that the spectrum of an arbitrary starlike graph\\u000acan be completely determined via separating functions $\\\\rho_t$ (see\\u000a\\\\cite{NazRoi,RedRoi,Red3}). This fact helps to get in an easy way several\\u000aresults for the spectra of starlike graphs.

I. K. Redchuk

2006-01-01

184

On Spectra of Starlike Graphs  

Microsoft Academic Search

In the present paper we show that the spectrum of an arbitrary starlike graph can be completely determined via separating functions $\\\\rho_t$ (see \\\\cite{NazRoi,RedRoi,Red3}). This fact helps to get in an easy way several results for the spectra of starlike graphs.

I. K. Redchuk

2006-01-01

185

Electrospray mass spectra of lanthanides  

SciTech Connect

The electrospray mass spectra of several elements in the lanthanide series are presented with the focus being on understanding the basic processes that occur to yield such spectra. The solution chemistry and the physical properties of the elements have a profound effect on the type of species observed in a mass spectrum. To perform elemental analysis by electrospray mass spectrometry, harsh declustering conditions are typically used. This results in a spectrum consisting of the bare metal ion (Ln[sup +] or Ln[sup 2+]) and molecular ions (LnO[sup +]) such as oxides as well as contributions due to matrix ions. The sampling conditions required to obtain such spectra require a large potential difference between the sampling plate and the skimmer at the atmosphere to vacuum interface, resulting in efficient collision-induced dissociation conditions. To monitor the process, a frame by frame illustration is used where the potential difference between the sampling plate and skimmer is increased in increments and the resultant spectra are captured. With this procedure, the dominant processes may be highlighted and explained step by step and a clearer understanding of the processes involved is obtained. 43 refs., 7 refs., 1 tab.

Stewart, I.I.; Horlick, G. (Univ. of Alberta, Edmonton, Alberta (Canada))

1994-11-15

186

Interpretation of Wave Energy Spectra.  

National Technical Information Service (NTIS)

Guidelines for interpreting nondirectional wave energy spectra are presented. A simple method is given for using the spectrum to estimate a significant height and period for each major wave train in most sea states. The method allows a more detailed and a...

E. F. Thompson

1980-01-01

187

Impact Broadening of Microwave Spectra  

Microsoft Academic Search

Pressure broadening in resonant and in nonresonant microwave spectra of gases, as well as the transition from resonant to nonresonant shape with increasing pressure, are treated in the impact approximation in a unified manner, based on the theories of Baranger, Kolb and Griem, and Fano. The relaxation rate in nonresonant absorption (Debye relaxation) is expressed in terms of collision cross

A. Ben-Reuven

1966-01-01

188

Vibrational Spectra of ?-Aminobutyric Acid  

NASA Astrophysics Data System (ADS)

The NIR-FT Raman, FT-IR spectral analysis of ?-Aminobutyric acid (GABA) a simple amino acid is carried out by density functional computations. The vibrational spectra confirm the existence of NH3+ in GABA. Hydroxyl groups H-bonded to the different extents are analysed, supported by computed results.

Suresh, D. M.; Sajan, D.; Laladas, K. P.; Joe, I. Hubert; Jayakumar, V. S.

2008-11-01

189

Raman spectra of carotenoids in natural products  

Microsoft Academic Search

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.

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

2003-01-01

190

Raman Spectra of Alkali Fluoride Crystals.  

National Technical Information Service (NTIS)

Polarized Raman spectra of LiF, NaF, and CsF and preliminary unpolarized spectra of KF and RbF have been measured at 300K. These spectra are compared with spectra predicted recently by Hardy and Karo, or with the two-phonon density of states. The calculat...

A. R. Evans D. B. Fitchen

1970-01-01

191

Infrared Spectra for 32 Stars (Johnson+ 1970)  

NASA Astrophysics Data System (ADS)

Relative fluxes are presented for 46 spectra (30 stars plus the Sun), ranging in spectral type from A0 to M7. Spectra of seven carbon stars are included. Although some spectra cover the wavenumbers from 2500 to 8200, many spectra do not include wavenumbers less than 4000 and there are many gaps as a result of atmospheric absorption. (47 data files).

Johnson, H. J.; Mendez, M. E.

1996-08-01

192

Vacuum ultraviolet absorption spectra of fluoromethanes  

Microsoft Academic Search

The electronic absorption spectra of tetrafluoromethane, fluoroform, methylene fluoride, and methylfluoride were measured between 120 and 60 nm. Except for intenstities the spectra are found to be essentially the same as the electron impact spectra published previously by Harshbarger, Robin, and Lassettre. An experimental setup is described whereby absorption spectra can be measured in this part of the spectrum with

P. Sauvageau; R. Gilbert; P. P. Berlow; C. Sandorfy

1973-01-01

193

Higher-order septin assembly is driven by GTP-promoted conformational changes: evidence from unbiased mutational analysis in Saccharomyces cerevisiae.  

PubMed

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

2014-03-01

194

Age and sex do not affect the volume, cell numbers, or cell size of the suprachiasmatic nucleus of the rat: an unbiased stereological study.  

PubMed

The circadian rhythms displayed by numerous biological functions are known to be sex specific and affected by aging. It has not been settled yet whether the sex- and age-related characteristics of circadian rhythms derive from changes in the anatomy of the suprachiasmatic nucleus. To shed light on these issues, we applied unbiased stereological techniques to estimate the volume of the suprachiasmatic nucleus as well as the total number of its cells and the mean volume of their somata and nuclei in progressively older groups of male and female Wistar rats (aged 1, 6, 12, 18, 24, and 30 months). The volume of the nucleus was estimated with the Cavalieri principle on serial sections. The total numbers of neurons and astrocytes were estimated by applying the optical fractionator, and the mean somatic and nuclear volumes of cells were estimated by using isotropic, uniform random sections and the nucleator method. On average, the volume of the suprachiasmatic nucleus was 0.044 mm3, and the total number of neurons and astrocytes was 17,400. Cells of the dorsomedial and ventrolateral components of the nucleus, which are morphologically different, have identical mean perikaryal and nuclear volumes, which we estimated to be 750 microns3 and 400 microns3, respectively. We further demonstrated that, at all ages analysed, the volume of the suprachiasmatic nucleus, the total cell number, and the mean somatic and nuclear volumes of its cells are affected neither by the age nor by the sex of the animal, regardless of the presence of sex- and age-related variations in circadian rhythms. However, the possibility that females may display changes in the volume of the suprachiasmatic nucleus at older ages cannot be ruled out. No effect of aging was observed in the total number of neurons or in the total number of astrocytes. PMID:8576416

Madeira, M D; Sousa, N; Santer, R M; Paula-Barbosa, M M; Gundersen, H J

1995-10-30

195

THE OPTICALLY UNBIASED GRB HOST (TOUGH) SURVEY. V. VLT/X-SHOOTER EMISSION-LINE REDSHIFTS FOR SWIFT GRBs AT z {approx} 2  

SciTech Connect

We present simultaneous optical and near-infrared (NIR) spectroscopy of 19 Swift {gamma}-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 R-tilde =24.6 mag). The median redshift is z-tilde =2.1 for all hosts and z-tilde =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{sub H,X}), for example, is closely related to the darkness of the afterglow and skewed toward low N{sub H,X} values in samples that are dominated by bursts with bright optical afterglows.

Kruehler, Thomas; Malesani, Daniele; Milvang-Jensen, Bo; Fynbo, Johan P. U.; Hjorth, Jens; Sparre, Martin; Watson, Darach J. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Jakobsson, Pall [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavik (Iceland); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Tanvir, Nial R. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)

2012-10-10

196

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

197

Modeling of phytochrome absorption spectra.  

PubMed

Phytochromes constitute one of the six well-characterized families of photosensory proteins in Nature. From the viewpoint of computational modeling, however, phytochromes have been the subject of much fewer studies than most other families of photosensory proteins, which is likely a consequence of relevant high-resolution structural data becoming available only in recent years. In this work, hybrid quantum mechanics/molecular mechanics (QM/MM) methods are used to calculate UV-vis absorption spectra of Deinococcus radiodurans bacteriophytochrome. We investigate how the choice of QM/MM methodology affects the resulting spectra and demonstrate that QM/MM methods can reproduce the experimental absorption maxima of both the Q and Soret bands with an accuracy of about 0.15 eV. Furthermore, we assess how the protein environment influences the intrinsic absorption of the bilin chromophore, with particular focus on the Q band underlying the primary photochemistry of phytochromes. PMID:23456980

Falklöf, Olle; Durbeej, Bo

2013-06-15

198

Variable spectra of active galaxies  

NASA Technical Reports Server (NTRS)

The analysis of EXOSAT spectra of active galaxies are presented. The objects examined for X-ray spectral variability were MR 2251-178 and 3C 120. The results of these investigations are described, as well as additional results on X-ray spectral variability related to EXOSAT observations of active galaxies. Additionally, the dipping X-ray source 4U1624-49 was also investigated.

Halpern, Jules P.

1988-01-01

199

Spectra of sodium aluminate solutions  

Microsoft Academic Search

The UV spectra of sodium aluminate solutions were obtained in the sodium oxide concentration range from 59 to 409 g\\/L and the caustic ratio range from 1.5 to 4.0 to reveal the structure characteristics of them, It is found that a new peak appears at about 370 nm besides peaks at about 220 and 266 nm in all solutions. The

Shu-hua MA; Shi-li ZHENG; Hong-bin XU; Yi ZHANG

2007-01-01

200

Stokes doubling in Auger spectra  

Microsoft Academic Search

It is shown that Stokes doubling of an Auger line takes place when the frequency of the incoming X-ray photons is scanned near an X-ray absorption resonance. The conditions for observing Stokes doubling effects in Auger spectra are found to depend strongly on the form of the spectral function of the incoming X-ray photons. These conditions are quantified in the

Faris Gel'Mukhanov; Hans Ågren

1994-01-01

201

Multiwavelength Systematics of OB Spectra  

NASA Astrophysics Data System (ADS)

The systematics of OB spectra are reviewed in the optical domain, dominated by photospheric lines, and in the far ultraviolet (both IUE and FUSE ranges), in which the stellar-wind profiles dominate. First, the two-dimensional (temperature, luminosity) trends in normal spectra are surveyed. Then, the normal reference frame having been established, various categories of peculiar objects can be distinguished relative to it, which reveal several phenomena of structural and/or evolutionary significance. Included are CNO anomalies at both early and late O types, three varieties of rapid rotators, hot and cool Of/WN transition objects, and the recently discovered second known magnetic O star. The importance of both optical and UV observations to understand these phenomena is emphasized; for instance, progress in understanding the structure of the new O-type magnetic oblique rotator is hampered by the current lack of a UV spectrograph. While progress in the physical interpretation of these trends and anomalies has been and is being made, increased attention to modeling the systematics would accelerate future progress in this autho?s opinion. Finally, preliminary results from a Chandra high-resolution survey of OB X-ray spectra (PI W. Waldron) are presented. They provide evidence that, just as emerged earlier in the UV, systematic morphological trends exist in the X-ray domain that are correlated with the optical spectral types, and hence the fundamental stellar parameters, contrary to prevailing opinion.

Walborn, Nolan R.

2007-07-01

202

Multiwavelength Systematics of OB Spectra  

NASA Astrophysics Data System (ADS)

The systematics of OB spectra are reviewed in the optical domain, dominated by photospheric lines, and in the far ultraviolet (both IUE and FUSE ranges), in which the stellar-wind profiles dominate. First, the two-dimensional (temperature, luminosity) trends in normal spectra are surveyed. Then, the normal reference frame having been established, various categories of peculiar objects can be distinguished relative to it, which reveal several phenomena of structural and/or evolutionary significance. Included are CNO anomalies at both early and late O types, three varieties of rapid rotators, hot and cool Of/WN transition objects, and the recently discovered second known magnetic O star. The importance of both optical and UV observations to understand these phenomena is emphasized; for instance, progress in understanding the structure of the new O-type magnetic oblique rotator is hampered by the current lack of a UV spectrograph. While progress in the physical interpretation of these trends and anomalies has been and is being made, increased attention to modeling the systematics would accelerate future progress in this author's opinion. Finally, preliminary results from a Chandra high-resolution survey of OB X-ray spectra (PI W. Waldron) are presented. They provide evidence that, just as emerged earlier in the UV, systematic morphological trends exist in the X-ray domain that are correlated with the optical spectral types, and hence the fundamental stellar parameters, contrary to prevailing opinion.

Walborn, N. R.

2006-08-01

203

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

204

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

205

The analysis of astronomical spectra  

NASA Astrophysics Data System (ADS)

Efforts to develop and improve computer analysis techniques for astronomical spectra in SERC Collaborative Computational Project 7 (CCP7) during the period 1985-1988 are reviewed. Consideration is given to the organizational structure and personnel of CCP7, advanced computers for LTE and non-LTE stellar-atmosphere models, the network systems STARLINK and JANET, the CCP7 software library, and CCP7-sponsored meetings and newsletters. The studies underway at 11 observatories and university centers in the UK and the FRG are listed and briefly characterized.

Jeffery, C. S.

1989-06-01

206

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

207

Uranium spectra in the ICP  

NASA Astrophysics Data System (ADS)

Uranium spectra have been studied by inductively coupled plasma atomic emission spectroscopy (ICP-AES). In total, 8361 uranium lines were observed in the wavelength range of 235-500 nm. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by a disk with data files and text files for an IBM-compatible computer. The main article discusses the scientific aspects of the subject and explains the purpose of the data files.

Ghazi, A. A.; Qamar, Sajid; Atta, M. A.

1994-05-01

208

Reflection spectra of solids of planetary interest  

NASA Technical Reports Server (NTRS)

This paper reproduces the spectra of solids which might be found on the surfaces of planetary bodies or as solid condensates in the upper planetary atmosphere. Among these are spectra of various iron compounds of interest in the study of the clouds of Venus. Other spectra (some at low temperature) are included for various sulfides relevant to the planet Jupiter. Meteorite and coal spectra are also included to illustrate dark carbon compounds.

Sill, G. T.; Carm, O.

1973-01-01

209

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

210

Energy spectra and LET spectra of protons behind shielding  

NASA Astrophysics Data System (ADS)

With the advent of devices sensitive to SEU due to direct ionization by protons, it became important to know the flux and energies of protons behind aluminum shielding or within satellites. We present new analytically derived expressions for the energy distribution of incident protons, after passing the shielding, and of secondary protons emitted within the shielding. The results are compared with those of the MULASSIS code. In some cases, like a satellite in a GCR orbit, the contribution of the secondary protons to SEU might be the dominant one. Proton energy-distributions behind shielding are proportional, at low energy values, to inverse proton-LET in aluminum. Their calculated LET-spectra in silicon can be used for evaluating SEU-rate in space. The analytic expressions presented here can be useful in calculating the influence of shielding on other incident ions and secondary ions.

Katz, Sari; Barak, Joseph

2014-08-01

211

Action Spectra of Zebrafish Cone Photoreceptors  

PubMed Central

Zebrafish is becoming an increasingly popular model in the field of visual neuroscience. Although the absorption spectra of its cone photopigments have been described, the cone action spectra were still unknown. In this study we report the action spectra of the four types of zebrafish cone photoreceptors, determined by measuring voltage responses upon light stimulation using whole cell patch clamp recordings. A generic template of photopigment absorption spectra was fit to the resulting action spectra in order to establish the maximum absorption wavelength, the A2-based photopigment contribution and the size of the ?-wave of each cone-type. Although in general there is close correspondence between zebrafish cone action- and absorbance spectra, our data suggest that in the case of MWS- and LWS-cones there is appreciable contribution of A2-based photopigments and that the ?-wave for these cones is smaller than expected based on the absorption spectra.

Endeman, Duco; Klaassen, Lauw J.; Kamermans, Maarten

2013-01-01

212

Spectra from pair-equilibrium plasmas  

NASA Technical Reports Server (NTRS)

A numerical model of relativistic nonmagnetized plasma with uniform temperature and electron density distributions is considered, and spectra from plasma in pair equilibrium are studied. A range of dimensionless temperature (T) greater than about 0.2 is considered. The spectra from low pair density plasmas in pair equilibrium vary from un-Comptonized bremsstrahlung spectra at Thomson cross section tau(N) much less than one to Comptonized bremsstrahlung spectra with tau(N) over one. For high pair density plasmas the spectra are flat for T greater than about one, and have broad intensity peaks at energy roughly equal to 3T for T less than one. In the latter region the total luminosity is approximately twice the annihilation luminosity. All spectra are flat in the X-ray region, in contradiction to observed AGN spectra. For dimensionless luminosity greater than about 100, the cooling time becomes shorter than the Thomson time.

Zdziarski, A. A.

1984-01-01

213

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

214

[Vibrational spectra of Corallium elatius].  

PubMed

Corallium elatius, which has unique color distribution characteristic, is the most important species of Taiwan precious corals. EPMA, XRD, FTIR and Laser Raman detective methods were used to study the chemical, mineral composition and spectra characteristics of Corallium elatius. The result of EPMA, XRD and FTIR shows the high-Mg calcite mineral componentand the stable minor chemical constituents of the samples. Meanwhile, the cell parameter indicates the lattice distortion and the preferred orientation of calcite grain caused by organic matter. The red part of the samples shows a different Raman spectrum from that of the white part, located at 1517/1128 cm(-1) and 1296/1016 cm(-1). Raman scattering measurement reveals the relationship between the organic matter and color. PMID:24369625

Fan, Lu-wei; Zhang, Yan; Hu, Yang

2013-09-01

215

Graviton Spectra in String Cosmology  

SciTech Connect

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}{sup 3} increase and initiates an {omega}{sup {minus}7} decrease, is induced during the so far overlooked bounce of the scale factor between the collapsing deflationary era (or pre{endash}big bang) and the expanding inflationary era (or post{endash}big bang). The frequency and the intensity of the peak may likely fall in the realm of the new generation of interferometric detectors. The existence of a peak, at variance with ordinarily monotonic graviton spectra, would therefore offer strong support to string cosmology. {copyright} {ital 1997} {ital The American Physical Society}

Galluccio, M.; Occhionero, F. [Osservatorio Astronomico di Roma, Via del Parco Mellini 84, 00136 Roma (Italy)] [Osservatorio Astronomico di Roma, Via del Parco Mellini 84, 00136 Roma (Italy); Litterio, M. [Istituto Astronomico dell`Universita La Sapienza, Via G. M. Lancisi 29, 00186 Roma (Italy)] [Istituto Astronomico dell`Universita La Sapienza, Via G. M. Lancisi 29, 00186 Roma (Italy)

1997-08-01

216

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

217

Infrared spectra of natural and synthetic malachites  

NASA Astrophysics Data System (ADS)

IR absorption and reflection spectra of dark and light samples of natural and synthetic malachite over 400-4000 cm-1 are studied for the purpose of improving the synthesis technique and in order to distinguish between natural malachite and malachite grown from ammonia solutions. Nitrogen was not detected in the IR spectra or in microprobe analyses of the synthetic material. The differences found in the IR spectra were insignificant and cannot be regarded as distinctive indicators of these materials.

Schuiskii, A. V.; Zorina, M. L.

2013-09-01

218

Reflection spectra of solids of planetary interest  

NASA Technical Reports Server (NTRS)

The spectra of solids are reproduced which might be found on the surfaces of planetary bodies or as solid condensates in the upper planetary atmosphere. Among these are spectra of various iron compounds of interest in the study of the clouds of Venus. Other spectra are included of various sulfides, some at low temperature, relevant to the planet Jupiter. Meteorite and coal abstracts are also included, to illustrate dark carbon compounds.

Sill, G. T.

1973-01-01

219

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

220

Automatic analysis of Rutherford backscattering spectrometry spectra  

Microsoft Academic Search

It has been shown that Bayesian statistics is a powerful tool in the analysis of ion beam analysis (IBA) data. Past work has shown its applicability to the deconvolution of the detector response function from micro-Rutherford backscattering spectrometry (RBS) and micro-proton-induced X-ray emission (PIXE) spectra, subtraction of the background from PIXE spectra, the extraction of depth profiles from PIXE spectra

J. Padayachee; K. A. Meyer; V. M. Prozesky

2001-01-01

221

Bayesian analysis of mutational spectra.  

PubMed Central

Studies that examine both the frequency of gene mutation and the pattern or spectrum of mutational changes can be used to identify chemical mutagens and to explore the molecular mechanisms of mutagenesis. In this article, we propose a Bayesian hierarchical modeling approach for the analysis of mutational spectra. We assume that the total number of independent mutations and the numbers of mutations falling into different response categories, defined by location within a gene and/or type of alteration, follow binomial and multinomial sampling distributions, respectively. We use prior distributions to summarize past information about the overall mutation frequency and the probabilities corresponding to the different mutational categories. These priors can be chosen on the basis of data from previous studies using an approach that accounts for heterogeneity among studies. Inferences about the overall mutation frequency, the proportions of mutations in each response category, and the category-specific mutation frequencies can be based on posterior distributions, which incorporate past and current data on the mutant frequency and on DNA sequence alterations. Methods are described for comparing groups and for assessing dose-related trends. We illustrate our approach using data from the literature.

Dunson, D B; Tindall, K R

2000-01-01

222

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

223

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

224

Photosynthetic Action Spectra of Trees  

PubMed Central

Comparative isoenergetic action spectra of net photosynthesis for intact, current year foliage of five tree species were determined from 400 to 710 nm by CO2 exchange analysis. The blue (400 to 500 nm) peak of net photosynthetic activity for the green broadleaves of red alder (Alnus rubra Bong.) was reduced to a plateau for the green needle-leaves of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and Sitka spruce (Picea sitchensis [Bong.] Carr.), a shoulder for the blue-green needles of Colorado spruce (Picea pungens Engelm.), and a reduced shoulder for the blue-white needles of Blue spruce (Picea pungens var. hoospii). These differences were attributable neither to a differential blue light stimulation of photorespiration nor to a differential presence of a nonplastid screening pigment. The conifers all had similar carotenoid-chlorophyll ratios, with approximately 50% more carotenoid relative to chlorophyll as compared to red alder. Blue light absorption and low efficiency of energy transfer by the carotenoids probably accounts for the low net photosynthetic activity of the green conifers in blue light as compared to red alder. Leaf form per se (broad versus needle) had no distinguishable influence on these results.

Clark, John B.; Lister, Geoffrey R.

1975-01-01

225

Near-Infrared Spectra of Uranian Satellites  

NASA Astrophysics Data System (ADS)

We present 0.8 to 2.5 micron spectra taken on June 21 & 22, 1998 UT of the Uranian satellites Miranda, Titania, Ariel, Oberon, and Umbriel. The spectra were taken using The Aerospace Corporation's Near-Infrared Imaging Spectragraph (NIRIS) on the University of California's Lick Observatory 3 meter Shane telescope. These spectra will be compared with previous work including Brown, R.H. and Cruikshank, D.P. (1983) as well as more recent spectra and analysis by Grundy, W. et al. (1999). Support for this research was provided by The Aerospace Corporation's Independent Research and Development Program.

Venturini, C. C.; Lynch, D. K.; Rudy, R. J.; Mazuk, S.; Puetter, R. C.

2001-05-01

226

High Resolution Spectra of Solar Flares  

NASA Astrophysics Data System (ADS)

I discuss high-resolution solar flare spectra from the soft X-ray region through the extreme ultraviolet (EUV) wavelength regions. Spectra of solar flares at these wavelengths have been recorded since the late 1960s, beginning primarily with the NASA Orbiting Solar Observatory (OSO) series of spacecraft. Knowledge of EUV flare spectra took a quantum leap with the NASA Skylab Apollo Telescope Mount spectrographs in the early 1970s. Knowledge of the X-ray spectrum took a similar leap in the 1980s with the US Department of Defense P78-1 spacecraft, the NASA Solar Maximum Mission spacecraft (SMM), and the Japanese Hinotori spacecraft. Investigations of flare X-ray spectra continued with the BCS X-ray spectrometer experiment on the Japanese Yohkoh mission. Recently, EUV solar flare spectroscopy has been extended with the SUMER spectrometer on the ESA SOHO spacecraft. In addition to the above missions, significant contributions were made with instrumentation on a number of other spacecraft, e.g., the Soviet Intercosmos X-ray spectrometers. Our knowledge of the physical conditions in solar flares has been greatly expanded from analyses of X-ray and EUV flare spectra. I will discuss the general characteristics of the flare emission line and continuum spectra, and the physical processes that produce them. I will discuss what we have learned about solar flares from the spectra, and discuss solar flare spectra in terms of spectra expected from other astrophysical sources.

Doschek, G. A.

227

Designing density fluctuation spectra in inflation  

SciTech Connect

Scale-invariant (flat) fluctuation spectra are the most natural outcomes of inflation. Nonetheless current large-scale-structure observations seem to indicate more fluctuation power on large scales than flat spectra give. We consider a wide variety of models based on the chaotic inflation paradigm and sketch the effects that varying the expansion rate, structure of the potential surface, and the curvature coupling constants have on the quantum fluctuation spectra. We calculate in detail the quantum generation of fluctuation spectra by numerically solving the linearized perturbation equations for multiple scalar fields, the metric, and the radiation into which the scalars dissipate, following the evolution from inside the horizon through reheating.

Salopek, D.S. (Department of Physics, University of Toronto, Toronto, Canada M5S 1A7 (CA)); Bond, J.R. (Canadian Institute for Advanced Research Program, Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Canada M5S 1A1); Bardeen, J.M. (Department of Physics, University of Washington, Seattle, Washington 98195)

1989-09-15

228

Near infrared Raman spectra of Rhizoma dioscoreae  

NASA Astrophysics Data System (ADS)

A novel and compact near-infrared (NIR) Raman system is developed using 785-nm diode laser, volume-phase technology holographic system, and NIR intensified charge-coupled device (CCD). Raman spectra and first derivative spectra of Rhizoma Dioscoreae are obtained. Raman spectra of Rhizoma Dioscoreae showed three strong characteristic peaks at 477.4cm-1, 863.9cm-1, and 936.0cm-1. The major ingredients are protein, amino acid, starch, polysaccharides and so on, matched with the known basic biochemical composition of Rhizoma Dioscoreae. In the first derivative spectra of Rhizoma Dioscoreae, distinguishing characteristic peaks appeared at 467.674cm-1, 484.603cm-1, 870.37cm-1, 943.368cm-1. Contrasted with Rhizoma Dioscoreae Raman spectra, in 600cm-1 to 800cm-1, 1000cm-1 to 1400cm-1 regions, changes in Rhizoma Dioscoreae Raman first derivative spectra are represented more clearly than Rhizoma Dioscoreae Raman spectra. So Rhizoma Dioscoreae raman first derivative spectra can be an accurate supplementary analysis method to Rhizoma Dioscoreae Raman spectra.

Lin, Wenshuo; Chen, Rong; Chen, Guannan; Feng, Sangyuan; Li, Yongzeng; Huang, Zufang; Li, Yongsen

2008-03-01

229

Incorporating Spectra Into Periodic Timing  

NASA Astrophysics Data System (ADS)

The Chandra surveys have resulted in a wealth of data on low-luminosity X-ray sources (Lx 1030-34 erg/s) of Galactic scales beyond the local solar neighborhood. Many of these are compact binaries, in particular, cataclysmic variables, often identified by their periodic X-ray variability and spectra. Hong et al. (2009, 2011) have used energy quantiles (Hong, Schlegel & Grindlay, 2004) as a fast, robust indicator of spectral hardness and absorption of the X-ray sources. Energy quantiles also enable a simple but effective illustration of spectral changes with phase in these periodic systems: e.g. absorption by the accreting material is understood to drive the periodic light-curves. An interesting question is how to best make use of the information encapsulated in the periodic change in energy spectrum, along with the periodic change in intensity, especially for cases of ambiguous period determination? And, how to do it computationally efficiently? A first approach is to do the period search in intensity, as is standard; and then use a criterion of spectral variation to verify possible periods. Huijse, Zegers & Protopapas (2011) recently demonstrated a powerful period estimation technique using information potential and correntropy embedded in the light curve. Similar quantities based on energies (or energy quantiles) of X-ray photons can serve as criteria of spectral variation. A different approach treats the spectrum variations and intensity variations completely independently, searching through period-space in each, and then combining the results. A more general method would include both at the same time, looking for statistically significant variations above what is expected for a constant (in intensity and spectrum).

Connors, Alanna; Hong, J.; Protopapas, P.; Kashyap, V.

2011-09-01

230

lambda Bootis stars with composite spectra  

Microsoft Academic Search

We examine the large sample of lambda Boo candidates collected in Table 1 of Gerbaldi et al. (\\\\cite{Gerbaldi2003}) to see how many of them show composite spectra. Of the 132 lambda Boo candidates we identify 22 which definitely show composite spectra and 15 more for which there are good reasons to suspect a composite spectrum. The percentage of lambda Boo

R. Faraggiana; P. Bonifacio; E. Caffau; M. Gerbaldi; M. Nonino

2004-01-01

231

Spectra of Meteors from Halley's Comet.  

National Technical Information Service (NTIS)

The spectra of 17 bright Orionid meteors from comet Halley, photographed between 1958 and 1968, are compared with the spectra of other fast meteors. The spectral region from 3100 to 8700 A is covered, with a wide range of instrumental dispersion. The brig...

I. Halliday

1986-01-01

232

Extreme-Ultraviolet Spectra of Ionic Crystals  

Microsoft Academic Search

The absorption spectra of several ionic crystals were obtained by the use of synchrotron radiation with photon energies in the range 50-250 eV. This range includes thresholds for excitation of both p and d core states. Arguments are given that peaks in the observed spectra are generally due to maxima in the final density of states, rather than exciton phenomena.

Frederick C. Brown; Christian Gähwiller; Hiizu Fujita; A. Barry Kunz; William Scheifley; Nicholas Carrera

1970-01-01

233

Reference Raman spectra of eleven miscellaneous pesticides.  

PubMed

The Raman spectra of ICP (propham), CIPC (chlorpropham), carbaryl, EPTC (ethyl N,N-dipropyl (3-chlorophenyl) carbamate), pebulate, CDEC (2-chloroallyl diethyldithiocarbamate), thiram, maneb, zineb, ferbam, and nicotine have been recorded. These spectra are presented, along with tables giving values for the frequencies. PMID:993181

Nicholas, M L; Powell, D L; Williams, T R; Thompson, R Q; Oliver, N H

1976-11-01

234

Current-fluctuation spectra of liquid rubidium  

Microsoft Academic Search

The mode-coupling theory has been worked out to calculate the longitudinal and transverse current-fluctuation spectra, the dynamical structure factor, and the dynamical as well as the static transport coefficients of liquid rubidium. The results are compared with experimental data. A detailed comparison of the excitation spectra of liquid rubidium with those of liquid argon is presented.

J. Bosse; W. Götze; M. Lücke

1978-01-01

235

Diffuse Reflectance Spectra of Energetic Material.  

National Technical Information Service (NTIS)

The diffuse reflectance spectra of pure, solid HNS, TNT, HMX, RDX and PETN have been recorded. These spectra reveal that all of the high explosives (HE) have strong absorption profiles in the UV region of the spectrum and much weaker absorption in the vis...

R. A. Borg

1994-01-01

236

Homogeneous NMR Spectra in Inhomogeneous Fields  

Microsoft Academic Search

Researchers interested in high-resolution nuclear magnetic resonance (NMR) spectroscopy have long sought higher magnetic fields to enhance resolution and simplify spectra. Magnets with substantially larger fields than those available in the best commercial spectrometers are available, but the inhomogeneity is unacceptable for high-resolution spectra. A detection method (termed HOMOGENIZED) is presented that removes inhomogeneity while retaining chemical shift differences and

Sujatha Vathyam; Sanghyuk Lee; Warren S. Warren

1996-01-01

237

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

238

PCA: Principal Component Analysis for spectra modeling  

NASA Astrophysics Data System (ADS)

The mid-infrared spectra of ultraluminous infrared galaxies (ULIRGs) contain a variety of spectral features that can be used as diagnostics to characterize the spectra. However, such diagnostics are biased by our prior prejudices on the origin of the features. Moreover, by using only part of the spectrum they do not utilize the full information content of the spectra. Blind statistical techniques such as principal component analysis (PCA) consider the whole spectrum, find correlated features and separate them out into distinct components. This code, written in IDL, classifies principal components of IRS spectra to define a new classification scheme using 5D Gaussian mixtures modelling. The five PCs and average spectra for the four classifications to classify objects are made available with the code.

Hurley, Peter D.; Oliver, Seb; Farrah, Duncan; Wang, Lingyu; Efstathiou, Andreas

2012-07-01

239

Principal Component Analysis of SDSS Stellar Spectra  

NASA Astrophysics Data System (ADS)

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. We make publicly available the resulting high signal-to-noise mean spectra and the other three eigenspectra. 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 SDSS. We analyze correlations between eigencoefficients, and metallicity and gravity estimated by SEGUE Stellar Parameters Pipeline, and find similar performance. The SDSS stellar spectroscopic database and the PCA offer a convenient method to classify new spectra, as well as to search for unusual spectra.

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

2009-01-01

240

Optical Spectra of L-DWARFS  

NASA Astrophysics Data System (ADS)

Theoretical spectra, of L-dwarfs (Teff <2200 K) were computed for a. grid of the "dusty" C-model atmospheres of Tsuji (1998). To fit the observed spectra of L-dwarfs we used two additional (evristic) suggestions: - molecular densities of TiO and VO governed the visible spectra, of M-dwarfs are reduced due to the extra depletion of V and Ti atoms into grains in atmospheres of Teff <2200 K; - There are (a few) additional opacity k sources in L-dwarf atmospheres; A few lands of k = f(A) dependences were used to get "the better fit" of observed spectra of L-dwarfs, We show: -We may fit the observed sequence of L-dwarf spectra using in the frame of our simple model; - Observed sequence of the L-dwarf spectra is the temperature sequence; - At first time, the region of 860 nm contained CrH bands is well fitted; -There are a few possibilities to get the reliable fits to the observed spectra; -In the frame of our approach we have found the solution even for the case of G1229B.

Pavlenko, Ya.

241

Frequency spectra of beam-plates revisited.  

PubMed

Based on Mindlin's plate theory, the frequency spectra for flexural and thickness-shear vibrations of a finite beam-plate with different combinations of boundary conditions are presented and studied. Comparing them with the dispersion curves of the infinite beam-plate reveals an intrinsic relation between resonant vibration and guided wave propagation. The fundamental frequency spectra, which are for beam-plates with hinged and/or guided edges, are found to play an important role in understanding the spectra of beam-plates with other boundary conditions. PMID:18606431

Guo, Y Q; Chen, W Q; Pao, Y H

2009-01-01

242

Spectra of KIC10661783 (Lehmann+, 2013)  

NASA Astrophysics Data System (ADS)

In 2010, we obtained 26 high-resolution spectra of KIC 10661783 in seven almost consecutive nights using the Coude-echelle spectrograph at the 2-m telescope of the Thueringer Landessternwarte Tautenburg. The spectra have a resolving power of 64000 and cover the wavelength range 470-740nm. The exposure time was 30 min and the spectra have a signal-to-noise ratio of 90 on average. They were reduced using standard ESO-MIDAS packages and a routine for the calibration of the instrumental radial velocity zero-point using O2 telluric lines. (2 data files).

Lehmann, H.; Southworth, J.; Tkachenko, A.; Pavlovski, K.

2013-08-01

243

Seismic source spectra and estimated stress drop derived from cohesive-zone models of circular subshear rupture  

NASA Astrophysics Data System (ADS)

Earthquake stress drops are often estimated from far-field body wave spectra using measurements of seismic moment, corner frequency and a specific theoretical model of rupture behaviour. The most widely used model is from Madariaga in 1976, who performed finite-difference calculations for a singular crack radially expanding at a constant speed and showed that bar{f}_c = k ? /a, where bar{f}_c is spherically averaged corner frequency, ? is the shear wave speed, a is the radius of the circular source and k = 0.32 and 0.21 for P and S waves, respectively, assuming the rupture speed Vr = 0.9?. Since stress in the Madariaga model is singular at the rupture front, the finite mesh size and smoothing procedures may have affected the resulting corner frequencies. Here, we investigate the behaviour of source spectra derived from dynamic models of a radially expanding rupture on a circular fault with a cohesive zone that prevents a stress singularity at the rupture front. We find that in the small-scale yielding limit where the cohesive-zone size becomes much smaller than the source dimension, P- and S-wave corner frequencies of far-field body wave spectra are systematically larger than those predicted by the Madariaga model. In particular, the model with rupture speed Vr = 0.9? shows that k = 0.38 for P waves and k = 0.26 for S waves, which are 19 and 24 per cent larger, respectively, than those of Madariaga. Thus for these ruptures, the application of the Madariaga model overestimates stress drops by a factor of 1.7. In addition, the large dependence of corner frequency on take-off angle relative to the source suggests that measurements from a small number of seismic stations are unlikely to produce unbiased estimates of spherically averaged corner frequency.

Kaneko, Y.; Shearer, P. M.

2014-05-01

244

Establishment of the Spectra of Kinetic Turbulence.  

National Technical Information Service (NTIS)

An analysis of kinetic equations describing the establishment of Langmuir turbulence spectra is presented. Secondary turbulence occurs where stationary distribution consists of many peaks. The position of peaks is established and their amplitudes complete...

A. K. Pergament A. M. Dykhne L. A. Bolshov V. P. Kiselev

1979-01-01

245

On Inelastic Response Spectra for Aseismic Design.  

National Technical Information Service (NTIS)

The sources of variability in inelastic response spectra, namely, strong ground motion duration, ductility level, and viscous damping ratio, are investigated. From time history analysis, it is concluded that the Newmark inelastic response spectrum for ela...

E. H. Vanmarcke J. M. Biggs S. S. P. Lai

1978-01-01

246

Assignment of Optical Spectra for Vanadyl Complexes.  

National Technical Information Service (NTIS)

An empirical correlation between e.s.r. hyperfine splittings and values of the ratio of axial to equatorial charge obtained from optical spectra is presented which makes possible a consistent set of optical assignments.

H. A. Kuska M. T. Rogers

1965-01-01

247

Synthesis and Spectra of Vanadium Complexes.  

ERIC Educational Resources Information Center

Describes an experiment which illustrates simple synthetic techniques, redox principles in synthesis reactions, interpretation of visible spectra using Orgel diagrams, and the spectrochemical series. The experiment is suitable for the advanced undergraduate inorganic chemistry laboratory. (JN)

Ophardt, Charles E.; Stupgia, Sean

1984-01-01

248

Impact Ionisation Mass Spectra of Mineral Microparticles  

NASA Astrophysics Data System (ADS)

We present mass spectra derived from the impact ionisation plasmas generated by the hypervelocity impacts of mineral microparticles over a range of speeds. The mineral microparticles were made from silicates (olivine, pyroxene, anorthite) and pyrrhotite and accelerated to velocities of 1->30 km s-1 using the Van de Graaff electrostatic accelerator at the Max Planck Institut für Kernphysik, Heidelberg [15]. The mass spectra were produced using high resolution reflectrontype instruments (e.g. LAMA etc. [20, 19, 18]) intended for use as space-based dust telescopes. We show that, if spectra are obtained over a range of impact velocities, it is possible to identify species from the bulk mineral material even if there are significant contributions to the spectra from organic or anthropogenic contaminants. In some cases it is also possible to infer the composition of the mineral, based on unique fragment and cluster ions.

Hillier, J. K.; Mocker, A.; Green, S. F.; Kempf, S.; Postberg, F.; Sestak, S.; Srama, R.; Sternovsky, Z.; Trieloff, M.

2011-10-01

249

Vibrational and vibronic spectra of tryptamine conformers  

NASA Astrophysics Data System (ADS)

Conformation-specific ionization-detected stimulated Raman spectra, including both Raman loss and Raman gain lines, along with visible-visible-ultraviolet hole-burning spectra of tryptamine (TRA) conformers have been measured simultaneously, with the aim of obtaining new data for identifying them. The slightly different orientations of the ethylamine side chain relative to the indole lead to unique spectral signatures, pointing to the presence of seven TRA conformers in the molecular beam. Comparison of ionization-loss stimulated Raman spectra to computationally scaled harmonic Raman spectra, especially in the alkyl C-H and amine N-H stretch regions together with the retrieved information on the stabilities of the TRA conformers assisted their characterization and structural identification. The prospects and limitations of using these spectroscopic methods as potential conformational probes of flexible molecules are discussed.

Mayorkas, Nitzan; Bernat, Amir; Izbitski, Shay; Bar, Ilana

2013-03-01

250

Comparing Ultraviolet Spectra Against Calculations: First Results  

NASA Technical Reports Server (NTRS)

The five-year goal of this effort is to calculate high fidelity mid-UV spectra for individual stars and stellar systems for a wide range of ages, abundances, and abundance ratios. In this first year, the emphasis was placed on revising the list of atomic line parameters used to calculate mid-UV spectra. First, new identifications of atomic lines and measurements of their transition probabilities were obtained for lines of the first and second ionization stages of iron-peak elements. Second, observed mid-UV and optical spectra for standard stars were re-analyzed and compared to new calculations, to refine the determination of transition probabilities and to estimate the identity of lines still missing from the laboratory lists. As evidenced by the figures, a dramatic improvement has resulted in the reproduction of the spectra of standard stars by the calculations.

Peterson, Ruth C.

2003-01-01

251

The Analysis of Cold Neutron Spectra.  

National Technical Information Service (NTIS)

The report reviews briefly several methods for interpreting neutron scattering data in terms of center frequency of infrared and Raman Spectra. In addition, a determination of elastic constants and thermodynamic properties from dispersion data for crystal...

R. A. Kromhout D. F. Burch

1969-01-01

252

Analysis of Cold Neutron Spectra of Metals.  

National Technical Information Service (NTIS)

A recently developed method for obtaining the absorbed energy spectrum, and calculating its absorption frequencies from elastic constants data, has been applied to metals, using cold neutron spectra in absence of infrared data. The emitted spectrum from i...

H. S. Plendl R. A. Kromhout

1971-01-01

253

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

254

Multivariate analysis of endometrial tissue fluorescence spectra  

NASA Astrophysics Data System (ADS)

Background and Objective: The detailed multivariate analysis of endometrial tissue fluorescence spectra was done. Spectra underlying features and classification algorithm were analyzed. An effort has been made to determine the importance of neopterin component in endometrial premalignization. Study Design/Materials and Methods: Biomedical tissue fluorescence was measured by excitation with the Nd YAG laser third harmonic. Multivariate analysis techniques were used to analyze fluorescence spectra. Biomedical optics group at Vilnius University analyzed the neopterin substance supplied by the Institute of Medical Chemistry and Biochemistry of Innsbruck University. Results: Seven statistically significant spectral compounds were found. The classification algorithm classifying samples to histopathological categories was developed and resulted in sensitivity of 80% and specificity 93% for malignant vs. hyperplastic and normal. Conclusions: Fluorescence spectra could be classified with high accuracy. Spectral variation underlying features can be extracted. Neopterin component might play an important role in endometrial hyperplasia development.

Vaitkuviene, Aurelija; Auksorius, E.; Fuchs, D.; Gavriushin, V.

2002-10-01

255

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

256

Establishment of the spectra of kinetic turbulence  

NASA Technical Reports Server (NTRS)

An analysis of kinetic equations describing the establishment of Langmuir turbulence spectra is presented. Secondary turbulence occurs where stationary distribution consists of many peaks. The position of peaks is established and their amplitudes complete undamped oscillations. It is pointed out that establishing spectra can occur only during adiabatic inclusion of pumping. It is significant here that the adiabiatic condition is more rigid than the ordinary by several hundred times.

Bolshov, L. A.; Dykhne, A. M.; Kiselev, V. P.; Pergament, A. K.

1979-01-01

257

THE SPITZER ATLAS OF STELLAR SPECTRA (SASS)  

SciTech Connect

We present the Spitzer Atlas of Stellar Spectra, which includes 159 stellar spectra (5-32 {mu}m; R {approx} 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, such as blue stragglers and certain pulsating variables. All of the spectra have been uniformly reduced, and all are available online. For dwarfs and giants, the spectra of early-type objects are relatively featureless, characterized by the presence of hydrogen lines in 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 circumstellar gas and/or dust. The sample includes five M supergiant spectra, which show strong dust excesses and in some cases polycyclic aromatic hydrocarbon features. Sequences of WR stars present the well-known pattern of lines of He I and He II, as well as forbidden lines of ionized metals. The characteristic flat-top shape of the [Ne III] line is evident even at these low spectral resolutions. Several Luminous Blue Variables and other transition stars are present in the Atlas and show very diverse spectra, dominated by circumstellar gas and dust features. We show that the [8]-[24] Spitzer colors (IRAC and MIPS) are poor predictors of spectral type for most luminosity classes.

Ardila, David R. [NASA Herschel Science Center, California Institute of Technology, Mail Code 100-22, Pasadena, CA 91125 (United States); Van Dyk, Schuyler D.; Makowiecki, Wojciech; Stauffer, John; Rho, Jeonghee; Fajardo-Acosta, Sergio; Hoard, D. W.; Wachter, Stefanie [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Song, Inseok, E-mail: ardila@ipac.caltech.ed [Department of Physics and Astronomy, University of Georgia at Athens, GA 30602-2451 (United States)

2010-12-15

258

Microwave Spectra of Benzotriazole and Pyrimidinotriazole  

NASA Astrophysics Data System (ADS)

The microwave spectra of 1 H-benzotriazole and its N-D isotopomer and of 1,2,4-triazolo[1,5- a]pyrimidine have been investigated in a heated cell. Both molecules are planar. Their dipole moments have been measured. The rotational spectra of some vibrational satellites belonging to the butterfly and 1,3-twisting vibrations have also been assigned.

Velino, B.; Cane, E.; Gagliardi, L.; Trombetti, A.; Caminati, W.

1993-09-01

259

Global comparisons of earthquake source spectra  

NASA Astrophysics Data System (ADS)

A key question in earthquake seismology is whether earthquake sources in different tectonic regions are functionally equivalent in terms of radiated ground motion. This thesis compares the apparent earthquake source radiation for six different tectonic regions covering Japan, Mexico, Turkey, California, British Columbia (B.C., western Canada), and eastern North America (ENA). The source, path and site effects were systematically separated from the observed spectra to the extent possible, to allow interregional comparisons of apparent source radiation. Large Fourier spectra databases were developed for both horizontal and vertical components over all distances for earthquakes of magnitude 2.5 to 7.5. Regional parameters characterizing source, path, and site properties, including crustal and near-surface site amplifications, were thoroughly investigated to separate the corresponding spectral responses, and thereby isolate apparent source processes. Effects on observed spectra of geometrical spreading, regional anelastic scattering, crustal and site amplification and deamplifications were removed to obtain the source spectra. Empirical source models were described at discrete frequencies as functions of m1 for each study region. Vertical spectra are more closely related to, and diagnostic of, the apparent source radiation than are horizontal spectra. Further study on source spectral scaling should take the source mechanism into account. After all the corrections made in this study, any discrepancies in source spectra between regions may be related to faulting mechanism. Source mechanism appears to be an important remaining influential factor that has not been sufficiently investigated at the present time. This is supported by the recent experimental findings that faulting types and shearing modes could have at least affected the spectral levels, if not the shape. The maximum slip velocity, num ? 0.5 m/s, estimated from the regional high frequency levels of the spectra, provides a region-independent source parameter that is more meaningful than the Brune stress parameter. (Abstract shortened by UMI.)

Chen, Shengzao

260

Signatures of rotation in oscillation spectra  

NASA Astrophysics Data System (ADS)

Rotation makes oscillation spectra of rapidly rotating stars much more complicated. Hence, new strategies need to be developed in order to interpret such spectra. In what follows, we describe how multi-colour photometric mode visibilities can be generalised to rapidly rotating stars, while fully taking into account centrifugal deformation and gravity darkening. We then go on to describe some first results as well as a strategy for constraining mode identification.

Reese, D. R.; Prat, V.; Barban, C.; van't Veer-Menneret, C.; MacGregor, K. B.

2012-12-01

261

Genetic influences on bipolar EEG power spectra  

Microsoft Academic Search

The EEG bipolar power spectra provide more localization than spectral measures obtained from monopolar referencing strategies, and have been shown to be useful endophenotypes of psychiatric disorders such as alcoholism. We estimated the additive genetic heritability of resting bipolar EEG power spectra in a large sample of non-twin sibling pairs. The corresponding heritabilities ranged between 0.220 and 0.647 and were

Yongqiang Tang; David B. Chorlian; Madhavi Rangaswamy; Bernice Porjesz; Lance Bauer; Samuel Kuperman; Sean O'Connor; John Rohrbaugh; Marc Schuckit; Arthur Stimus; Henri Begleiter

2007-01-01

262

Electron spectra of radical cations of heteroanalogs  

Microsoft Academic Search

Radical cation spectra of indazole and benzothiophene in the visible region were obtained by laser photolysis during the reaction of photoexcited quinones with these compounds in acetonitrile. The charge transfer bands of the complexes of the test compounds with p-chloranil and 7,7,8,8-tetracyanoquinodimethane in dioxane were recorded on a Specord M-40. Photoelectron spectra were obtained on a ES-3201 electron spectrometer. The

K. B. Petrushenko; V. K. Turchaninov; A. I. Vokin; A. F. Ermikov; Yu. L. Frolov

1985-01-01

263

Silicon Kedge XANES spectra of silicate minerals  

Microsoft Academic Search

Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO44-cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of

Dien Li; G. M. Bancroft; M. E. Fleet; X. H. Feng

1995-01-01

264

Investigation of nonequilibrium hydroxyl emission spectra  

Microsoft Academic Search

Ultraviolet nonequilibrium OH emission spectra in flames are measured and analyzed. Spectra of nonequilibrium coefficients are recorded for an optically\\u000a thin jet, and spectral absorption coefficients and electronic absorption band intensities are determined. Based on the developed\\u000a mathematical radiative transfer model in a nonequilibrium radiating media, the OH contribution to radiative jet cooling is estimated, and practical applications of the

N. I. Moskalenko; A. V. Zaripov; Yu. A. Il’in

2010-01-01

265

Investigation of nonequilibrium hydroxyl emission spectra  

NASA Astrophysics Data System (ADS)

Ultraviolet nonequilibrium OH emission spectra in flames are measured and analyzed. Spectra of nonequilibrium coefficients are recorded for an optically thin jet, and spectral absorption coefficients and electronic absorption band intensities are determined. Based on the developed mathematical radiative transfer model in a nonequilibrium radiating media, the OH contribution to radiative jet cooling is estimated, and practical applications of the nonequilibrium emission process to the development of optoelectronic systems of observation over aero carriers are considered.

Moskalenko, N. I.; Zaripov, A. V.; Il'in, Yu. A.

2010-07-01

266

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

267

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

268

Modeling lateral geniculate nucleus cell response spectra and Munsell reflectance spectra with cone sensitivity curves  

PubMed Central

We find that the cell response spectra of lateral geniculate nucleus cells, as well as the reflectance spectra of Munsell color chips, may be modeled by using the cone sensitivity functions of the long and medium cones. We propose a simple model for how the neural signals from the photoreceptors might be combined in the retina to closely approximate the reflectance spectra of Munsell color chips without input from the short cone.

Romney, A. Kimball; D'Andrade, Roy G.

2005-01-01

269

Spectra of 8 supergiants in nearby galaxies (Britavskiy+, 2014)  

NASA Astrophysics Data System (ADS)

The spectra of all program stars are presented. The log of observations and other information about these spectra are available into the article. The names of the files with spectra are the same as in the article. (3 data files).

Britavskiy, N. E.; Bonanos, A. Z.; Mehner, A.; Garcia-Alvarez, D.; Prieto, J. L.; Morrell, N. I.

2013-11-01

270

Infrared spectra of urine from cancerous bladders  

NASA Astrophysics Data System (ADS)

The infrared spectra of organic constituents of urine from cancerous bladders of some patients were recorded. The spectra of the organic part of the samples were classified into five types according to the bulk constituents. Samples with type A spectra consisted mainly of proteins with only trace amounts of lipids. Their spectra were characterized mainly by the absorption bands of proteins at the frequencies 3330, 3075, 2960, 2850, 1650, 1530, 1450, 1400 and 1320 cm-1, in addition to a weak band at 1720 cm-1 due to the absorption of lipids. Samples with type B spectra were characterized by high amounts of proteins and low amounts of lipids and phosphate compounds. The presence of phosphate compounds was indicated by the absorption bands at the frequencies 1100 and 1030 cm-1. Samples giving spectral type C were characterized by high urea contents as indicated by the presence of two strong bands at 1670 and 1630 cm-1. Samples with the spectral type D consisted of urea and phosphate compounds whereas the last spectral type E consisted mainly of calcium oxalates, uric acids and phosphate compounds. The presence of calcium oxalates was indicated by the presence of its diagnostic bands at the frequencies 1630 and 1330 cm-1, while the presence of uric acid was indicated by the bands at the frequencies 1360, 1130, 1020 and 880 cm-1. On the other hand, the spectra of the organic part of urine from some normal bladders exhibited the characteristic bands of urea only. Careful examination of the spectra of the inorganic part of urine revealed that some samples consisted mainly of hydroxyapatite. The absorption bands of hydroxyapatite appeared at the frequencies 568, 603, 985, 1037 and 1128 cm-1. The spectra of other samples showed that the bands of basic phosphates at the frequencies 568, 620, 727, 890, 1035 and 1140 cm-1. The spectra of the inorganic part of urine from a number of normal bladders displayed the bands of basic phosphates. The relationship between urine constituents and pathological types of bladder tumor tissue was discussed.

Moharram, M. A.; Higazi, A.; Moharram, A. A.

1996-06-01

271

Group independent component analysis of MR spectra  

PubMed Central

This study investigates the potential of independent component analysis (ICA) to provide a data-driven approach for group level analysis of magnetic resonance (MR) spectra. ICA collectively analyzes data to identify maximally independent components, each of which captures covarying resonances, including those from different metabolic sources. A comparative evaluation of the ICA approach with the more established LCModel method in analyzing two different noise-free, artifact-free, simulated data sets of known compositions is presented. The results from such ideal simulations demonstrate the ability of data-driven ICA to decompose data and accurately extract components resembling modeled basis spectra from both data sets, whereas the LCModel results suffer when the underlying model deviates from assumptions, thus highlighting the sensitivity of model-based approaches to modeling inaccuracies. Analyses with simulated data show that independent component weights are good estimates of concentrations, even of metabolites with low intensity singlet peaks, such as scyllo-inositol. ICA is also applied to single voxel spectra from 193 subjects, without correcting for baseline variations, line-width broadening or noise. The results provide evidence that, despite the presence of confounding artifacts, ICA can be used to analyze in vivo spectra and extract resonances of interest. ICA is a promising technique for decomposing MR spectral data into components resembling metabolite resonances, and therefore has the potential to provide a data-driven alternative to the use of metabolite concentrations derived from curve-fitting individual spectra in making group comparisons.

Kalyanam, Ravi; Boutte, David; Gasparovic, Chuck; Hutchison, Kent E; Calhoun, Vince D

2013-01-01

272

Spectra from nuclear-excited plasmas  

NASA Technical Reports Server (NTRS)

The paper discusses the spectra taken from He-3(n,p)H-3 nuclear-induced plasmas under high thermal neutron flux, lasing conditions. Also, initial spectra are presented for U-235F6 generated plasmas. From an evaluation of these spectra, important atomic and molecular processes that occur in the plasma can be inferred. The spectra presented are the first to be generated by He-3 and U-235F6 nuclear reactions under high neutron flux, lasing conditions. The U-235(n,ff)FF reaction, which liberates 165 MeV of fission-fragment kinetic energy, creates plasmas that are of great interest, since at sufficiently high densities of U-235F6 the gas becomes self-critical; thus, there is no need for an external driving reactor (source of neutrons). The spectra from mixtures of He-3 and Ar, Xe, Kr, Ne, Cl2, F2 and N2 indicate little difference between high-pressure nuclear-induced plasmas and high-pressure electrically pulsed afterglow plasmas for noble-gas systems

De Young, R. J.; Weaver, W. R.

1980-01-01

273

Optimum x-ray spectra for mammography.  

PubMed

A number of authors have calculated x-ray energies for mammography using, as a criterion, the maximum signal-to-noise ratio (SNR) obtainable per unit dose to the breast or conversely the minimum exposure for constant SNR. The predicted optimum energy increases with increasing breast thickness. Tungsten anode x-ray spectra have been measured with and without various added filter materials to determine how close the resultant spectra can be brought to the predicted optimum energies without reducing the x-ray output to unacceptable levels. The proportion of the total number of x-rays in a measured spectrum lying within a narrow energy band centred on the predicted optimum has been used as an optimum energy index. The effect of various filter materials on the measured x-ray spectra has been investigated both experimentally and theoretically. The resulting spectra have been compared with molybdenum anode, molybdenum filtered x-ray spectra normally used for mammography. It is shown that filters with K-absorption edges close to the predicted optimum energies are the most effective at producing the desired spectral shape. The choices of filter thickness and Vp are also explored in relationship to their effect on the resultant x-ray spectral shape and intensity. PMID:7146094

Beaman, S A; Lillicrap, S C

1982-10-01

274

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

275

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

276

EXPLORING THE MORPHOLOGY OF RAVE STELLAR SPECTRA  

SciTech Connect

The RAdial Velocity Experiment (RAVE) is a medium-resolution (R {approx} 7500) spectroscopic survey of the Milky Way that has already obtained over half a million stellar spectra. They present a randomly selected magnitude-limited sample, so it is important to use a reliable and automated classification scheme that identifies normal single stars and discovers different types of peculiar stars. To this end, we present a morphological classification of {approx}350, 000 RAVE survey stellar spectra using locally linear embedding, a dimensionality reduction method that enables representing the complex spectral morphology in a low-dimensional projected space while still preserving the properties of the local neighborhoods of spectra. We find that the majority of all spectra in the database ({approx} 90%-95%) belong to normal single stars, but there is also a significant population of several types of peculiars. Among them, the most populated groups are those of various types of spectroscopic binary and chromospherically active stars. Both of them include several thousands of spectra. Particularly the latter group offers significant further investigation opportunities since activity of stars is a known proxy of stellar ages. Applying the same classification procedure to the sample of normal single stars alone shows that the shape of the projected manifold in two-dimensional space correlates with stellar temperature, surface gravity, and metallicity.

Matijevic, G.; Zwitter, T. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Bienayme, O.; Siebert, A. [Observatoire de Strasbourg, Universite de Strasbourg, CNRS, 11 rue de l'universite, 67000 Strasbourg (France); Bland-Hawthorn, J. [Sydney Institute for Astronomy, University of Sydney, NSW 2006 (Australia); Boeche, C.; Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, 69120 Heidelberg (Germany); Freeman, K. C. [Research School of Astronomy and Astrophysics, Australia National University, Weston Creek, Canberra, ACT 2611 (Australia); Gibson, B. K. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 3TE (United Kingdom); Gilmore, G. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Helmi, A. [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Munari, U. [INAF Osservatorio Astronomico di Padova, 36012 Asiago (Italy); Navarro, J. [Department of Physics and Astronomy, University of Victoria, Victora, BC V8P 5C2 (Canada); Parker, Q. A.; Reid, W. [Department of Physics and Astronomy, Macquarie University, NSW 2109 (Australia); Seabroke, G. [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking RH5 6NT (United Kingdom); Siviero, A. [Department of Astronomy, Padova University, Vicolo dell'Osservatorio 2, 35122 Padova (Italy); Steinmetz, M.; Williams, M. [Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam (Germany); Watson, F. G., E-mail: gal.matijevic@fmf.uni-lj.si [Australian Astronomical Observatory, P.O. Box 296, Epping, NSW 2121 (Australia); and others

2012-06-01

277

Combined vibrational spectra of natural wardite  

NASA Astrophysics Data System (ADS)

Vibrational spectra (IR, Raman, inelastic neutron scattering) were measured of natural wardite (ideal formula NaAl 3(OH) 4(PO 4) 2·2 H 2O) from Trauira, Brazil, with the main impurities Fe and Ca. The spectra are discussed on the basis of a symmetry analysis restricted to one layer in the four-layer structure. The band pattern in the ?(OH) region is due to two different Al 2OH groups and their correlation coupling; their deformations ? and ? are assigned based on IR and INS spectra. Contributions of the hydrogen-bonded H 2O molecules are discussed, as are the vibrations of the AlO 6 octahedra dominating the Raman spectrum. From the fundamentals ?(OH) of the OH groups and their overtones anharmonicity constants have been estimated.

Breitinger, D. K.; Belz, H.-H.; Hajba, L.; Komlósi, V.; Mink, J.; Brehm, G.; Colognesi, D.; Parker, S. F.; Schwab, R. G.

2004-11-01

278

Carbon Signatures in Type Ia Supernovae Spectra  

NASA Astrophysics Data System (ADS)

A major difference between various explosion scenarios of Type Ia supernovae (SNe Ia) is the remaining amount of unburned (C + O) material and its velocity distribution within the expanding ejecta. We have investigated the presence of C II 6580 A in SNe Ia using the parameterized spectrum synthesis code, SYNOW, and optical spectra obtained from the publicly available database, SuSpect. While oxygen absorption features are not uncommon in SN Ia spectra, the presence of strong carbon absorption has only been confirmed in a handful of objects. The infrequent identification of carbon lines may be due to a weak absorption signature, line blending with Si II 6355 A absorption, or a combination of these and other possible effects. We will present SYNOW spectra fits for several SNe Ia.

Parrent, Jerod T.; Fesen, R. A.; Marion, H.

2010-01-01

279

Crystal field spectra of lunar pyroxenes.  

NASA Technical Reports Server (NTRS)

Absorption spectra in the visible and near infrared regions have been obtained for pyroxene single crystals in rocks from the Apollo 11, 12, 14, and 15 missions. The polarized spectra are compared with those obtained from terrestrial calcic clinopyroxenes, subcalcic augites, pigeonites, and orthopyroxenes. The lunar pyroxenes contain several broad, intense absorption bands in the near infrared, the positions of which are related to bulk composition, Fe(2+) site occupancy and structure type of the pyroxene. The visible spectra contain several sharp, weak peaks mainly due to spin-forbidden transitions in Fe(2+). Additional weak bands in this region in Apollo 11 pyroxenes are attributed to Ti(3+) ions. Spectral features from Fe(3+), Mn(2+), Cr(3+), and Cr(2+) were not observed.

Burns, R. G.; Abu-Eid, R. M.; Huggins, F. E.

1972-01-01

280

Tunneling spectra of individual magnetic endofullerene molecules  

NASA Astrophysics Data System (ADS)

We report measurements of electron tunneling spectra for individual N@C60 molecules, a spin-3/2 endohedral fullerene. The molecules were measured at low temperature in electromigrated break-junctions in the single-electron transistor configuration. We observe that the N@C60 devices exhibit a spin-state transition as a function of applied magnetic field which was not observed in C60 control devices. The nature of this transition enables us to identify the charge and spin states of the molecule. The spectra of N@C60 devices also exhibit low-energy excited states and signatures of non-equilibrium spin excitations predicted for this molecule. The experimental spectra can be reproduced theoretically by accounting for the exchange interaction between the nitrogen spin and electron(s) on the C60 cage.

Tam, E. S.; Grose, J. E.; Parks, J. J.; Ulgut, B.; Abruña, H. D.; Ralph, D. C.; Timm, C.; Scheloske, M.; Harneit, W.

2009-03-01

281

Infrared spectra of cesium chloride aqueous solutions  

NASA Astrophysics Data System (ADS)

The aqueous solutions of CsCl were studied at room temperature by infrared (IR) spectroscopy in the entire solubility range, 0-1200 g/L, using attenuated total reflection (ATR) sampling. The influence of anomalous dispersion on the IR-ATR spectra was evaluated by calculating the imaginary refractive index, k(?), of each sample. Factor analysis (FA) was used to determine the number and abundance of species in the solutions. FA applied to both k(?) spectra and IR-ATR spectra produced two principal spectra with a similar abundance of species. This result indicates that, even at high salt concentration, the optical effects do not influence the chemical analysis of IR-ATR spectra. The spectral modifications related to the salt concentrations are mainly first order. Second order effects were observed, but being weak, were not investigated. The two principal spectra are related to the two species present in the solution: pure water and CsCl-solvated water. From the latter, 2.8+/-0.4 water molecules were calculated to be associated with each close-bound Cs+/Cl- ion pair. In the case of KCl and NaCl aqueous solutions, both of which showed the same number of species, the number of water molecules associated to an ion pair was 5.0+/-0.4. That the latter number is different from that of CsCl indicates that the interaction between water molecules and ion pairs is different when cation Na or K in the chloride salt is replaced by Cs.

Max, Jean-Joseph; Chapados, Camille

2000-10-01

282

A Catalog of Chandra Grating Spectra  

NASA Astrophysics Data System (ADS)

We are developing a Chandra Grating-Data Archive and Catalog to make all grating spectra more visible and accessible to users. We intend to to provide a simple browser interface to analysis-quality standard spectral products (binned spectra and corresponding response files), with the addition of summary graphical products and model-independent flux properties tables. Such products and a browser interface will make it easy for a user to find observations of a particular object, type of object, or type of observation, to quickly assess the quality and potential usefulness of the spectra, and to download the data and responses as a package if desired. We will include LETG data as well as ACIS CC-mode observations. In addition to the data, portable reprocessing scripts, using CXC and other publicly available software which were used to create the archive will also be available to users, facilitating standard or customized reprocessing from download of Level 1 archive data to production of spectra and responses with minimal interaction (analogous to the "psextract" script commonly used for automated imaging spectral extraction). We will add some customized products which may take time, effort, or special expertise to produce. Candidates for such include extended source extractions, crowded field extractions, and aggregate products such as summed Capella or summed Orion-field-objects spectra. Additional content will grow according to user feedback. This catalog builds upon experience with other relevant work, such as the X-Atlas of HETGS spectra (http://cxc.harvard.edu/XATLAS) or the XMM-RGS spectral browser (http://xmm.esac.esa.int/BiRD). It is intended to be a long-term legacy product for Chandra gratings observations. This work was supported by NASA through the Smithsonian Astrophysical Observatory (SAO) contract SV3-73016 for the Chandra X-Ray Center and Science Instruments.

Huenemoerder, David; Nichols, J.; Mitschang, A.; Dewey, D.; Marshall, H.; Nowak, M.; Schulz, N.; Davis, J. E.; Houck, J. C.; Canizares, C.

2008-03-01

283

POLLUX: a database of stellar spectra - First step : SED and High Resolution Synthetic Spectra  

NASA Astrophysics Data System (ADS)

POLLUX is a stellar spectra database under development at the GRAAL laboratory (Montpellier, France). It will be made available on-line to the community through a VO compliant interface (http://pollux.graal.univ-montp2.fr). In its first version, POLLUX will propose theoretical data: high resolution synthetic spectra and spectral energy distribution.

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

2008-10-01

284

Elemental Spectra from the First ATIC Flight  

NASA Technical Reports Server (NTRS)

The Advanced Thin Ionization Calorimeter (ATIC) instrument is a balloon-borne experiment designed to measure the composition and energy spectra of Z = l to 26 cosmic rays over the energy range from approx. 10(exp 11) to approx. 10(exp 14) eV. The instrument consists of a silicon matrix charge detector, plastic scintillator strip hodoscopes interleaved with graphite interaction targets, and a fully active Bismuth Germanate (BGO) calorimeter. ATIC had two successful Long Duration Balloon flights launched from McMurdo Station, Antarctica in 2000 and 2002. In this paper, spectra of various elements measured during the first 16 day flight are presented.

Ahn, H. S.; Adams, J. H.; Bashindzhagyan, G.; Batkov, K. E.; Changv, J.; Christl, M.; Fazely, A. R.; Ganel, O.; Gunasingha, R. M.; Guzik, T. G.

2005-01-01

285

Mid-infrared spectra of Martian komantiite  

NASA Technical Reports Server (NTRS)

Synthetic mid-infrared emissive spectra of basalts of possible Martian komatiitic compositions were generated to show what might be seen in data returned from the Thermal Emission Spectrometer (TES). TES is flying on the Mars Observer arriving at Mars in late 1993. The synthetic Martian komatiite spectra were generated using mineralogy based on Shergottite, Nakhlite, and Chassigny (SNC) meteorites and Viking X-Ray Fluorescence (XRF) data. These data sets provide strong evidence for the existence of ultramafic lavas on Mars, particularly lavas of komatiitic composition.

Reyes, David P.

1992-01-01

286

Micro-Raman spectra of ugrandite garnet.  

PubMed

The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X(3)Y(2)(SiO(4))(3), X = Ca(2+), Y = Al(3+), Fe(3+), Cr(3+), according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported. PMID:19084471

Moroz, T; Ragozin, A; Salikhov, D; Belikova, G; Puchkov, V; Kagi, H

2009-08-01

287

Vibrational spectra study on quinolones antibiotics  

NASA Astrophysics Data System (ADS)

In order to be able to fully understand and easily identify the quilonoles, we collected IR and Raman spectra of six quinolones, and attempted to assign the attribution of the observed frequencies and their association with specific modes of vibration. According to the structure, the compounds were divided into the groups, and the similarities and differences were further studied by comparing. The result of the study shows that the frequency and intensity are comparable to the corresponding structure. The spectra not only have the commonness but also the individualities.

Wang, Yu; Yu, Ke; Wang, Sihuan

2006-09-01

288

Infrared Absorption Spectra of Deuterated Amorphous Carbon  

NASA Astrophysics Data System (ADS)

We report infrared absorption spectra of hydrogenated amorphous carbon (HAC) deposits prepared in the presence of deuterium. Spectra of D:HAC and DAC are characterized by the appearance of additional features near 2175 cm-1 (4.6 ?m) corresponding to stretching vibrations of CDn groups. These are accompanied by a weakening of absorption in the CHn absorption bands throughout the infrared. Laboratory data suggest that it may be possible to detect deuterium fractionations XD/H>=7.4×10-3 in carbonaceous dust along the line of sight to Galactic center sources via absorption within the CDn stretching band near 4.6 ?m.

Grishko, V. I.; Duley, W. W.

2003-01-01

289

AIS-2 spectra of California wetland vegetation  

NASA Technical Reports Server (NTRS)

Spectral data gathered by Airborne Imaging Spectrometers-2 from wetlands were analyzed. Spectra representing stands of green Salicornia virginica, green Sesuvium verrucosum, senescing Distichlis spicata, a mixture of senescing Scirpus acutus and Scirpus californicus, senescing Scirpus paludosus, senescent S. paludosus, mowed senescent S. paludosus, and soil were isolated. No difference among narrowband spectral reflectance of the cover types was apparent between 0.8 to 1.6 micron. There were, however, broadband differences in brightness. These differences were sufficient to permit a fairly accurate decomposition of the image into its major cover type components using a procedure that assumes an additive linear mixture of surface spectra.

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

1987-01-01

290

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

291

Four years of meteor spectra patrol  

NASA Technical Reports Server (NTRS)

The development of the NASA-Langley Research Center meteor spectra patrol is described in general terms. The recording of very faint meteors was made possible by three great strides in optical and photographic technology in the 1960's: (1) the availability of optical-grade fused silica at modest cost, (2) the development of large transmission gratings with high blaze efficiency, and (3) the development of a method for avoiding plate fogging due to background skylight, which consisted of using a photoelectric meteor detector which actuates the spectrograph shutter when a meteor occurs in the field. The classification scheme for meteor spectra developed by Peter M. Millman is described.

Harvey, G. A.

1974-01-01

292

Photon spectra from quark generation by WIMPs  

SciTech Connect

If the present dark matter (DM) in the Universe annihilates into Standard Model (SM) particles, it must contribute to the gamma ray fluxes that are detected on the Earth. The magnitude of such contribution depends on the particular DM candidate, but certain features of these spectra may be analyzed in a model-independent fashion. In this work we provide the fitting formula valid for the simulated photon spectra from WIMP annihilation into light quark-anti quark (qq-bar) channels in a wide range of WIMP masses. We illustrate our results for the cc-bar channel.

Cembranos, J. A. R.; Cruz-Dombriz, A.; Maroto, A. L. [Departamento de Fisica Teorica I, Universidad Complutense de Madrid, E-28040 Madrid (Spain) and Department of Mathematics and Applied Mathematics, University of Cape Town, 7700 (South Africa); Dobado, A.; Lineros, R. [IFIC, CSIC-Universitat de Valencia, Ed. Instituts, Apt. 22085, 46071 Valencia (Spain)

2011-05-23

293

Photoluminescence spectra of xenon implanted natural diamonds  

Microsoft Academic Search

The natural diamonds were implanted with 500keV Xe ions within the dose range 1×1013–5×1014cm?2. The post-implantation thermal annealing was carried out gradually at temperatures between 300°C and 1400°C. Photoluminescence spectra were measured after each annealing step in the temperature range 1.5–200K. The spectra featured the Xe-related zero phonon line (ZPL) at 811.6nm (1.527eV) and a vibronic sideband with several quasilocal

V. A. Martinovich; A. V. Turukhin; A. M. Zaitsev; A. A. Gorokhovsky

2003-01-01

294

Simultaneous Selective Detection of Multiple Quantum Spectra  

NASA Astrophysics Data System (ADS)

A three-dimensional multiple-quantum NMR experiment that produces individual spectra of all quantum orders is described. The separation of different quantum orders is accomplished via Fourier transformation with respect to the phase of the first two pulses of a generic three-pulse multiple-quantum sequence. This dramatically reduces the time required to obtain several selectively detected spectra and enhances the sensitivity and digital resolution from that obtained using the original two-dimensional technique. The experiment is demonstrated on the protons of para-chlorotoluene dissolved in the nematic liquid crystal Merck ZLI-1132.

Syvitski, R. T.; Burlinson, N.; Burnell, E. E.; Jeener, J.

2002-04-01

295

The POLLUX database of synthetic stellar spectra  

NASA Astrophysics Data System (ADS)

The POLLUX database of theoretical stellar spectra includes high-resolution synthetic spectra in the optical range, and spectral distribution energies from the UV to the infrared domains. Data are produced using state-of-the-art codes for each spectral type. The aim of the POLLUX database is to offer easy and direct comparison to observational data, as well as to create easily accessed stellar libraries from M dwarfs or red supergiants to hot and massive stars including Wolf-Rayet stars. Here, we review the major steps of the elaboration of such a database : current status, ongoing and further developments. http://pollux.graal.univ-montp2.fr

Palacios, A.; Lèbre, A.; Sanguillon, M.; Maeght, P.

296

Electronic absorption spectra of lunar minerals  

NASA Technical Reports Server (NTRS)

Techniques for obtaining information on the crystal chemistry of transition-metal ions from measurement of the electronic absorption spectra of lunar minerals are reviewed along with the theory of spectral interpretation. Typical polarized absorption spectra are examined for lunar pyroxenes, pyroxferroite, olivine, and plagioclase feldspars. Oxidation states of Fe, Ti, and Cr in lunar minerals are discussed, and conditions under which they crystallized are considered. It is shown how information on the gross mineralogy and petrology of different regions of the moon's surface may be extracted from remote reflectivity measurements of that surface.

Vaughan, D. J.; Burns, R. G.

1977-01-01

297

Micro-Raman spectra of ugrandite garnet  

NASA Astrophysics Data System (ADS)

The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X 3Y 2(SiO 4) 3, X = Ca 2+, Y = Al 3+, Fe 3+, Cr 3+, according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.

Moroz, T.; Ragozin, A.; Salikhov, D.; Belikova, G.; Puchkov, V.; Kagi, H.

2009-08-01

298

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

299

Electro-orientation spectra of hematic cells  

Microsoft Academic Search

We calculate the turnover frequency spectra for erythrocyte hematic cells. For this purpose we present a simple approach to calculate the electric field induced torque on essentially dielectric objects. We define an effective dipole moment as a function of the cell internal electric field distribution which is determined by using an adaptive finite-element numerical method. The realistic shape of the

José L. Sebastián; Sagrario Muñoz; Miguel Sancho; G. Marti?nez

2010-01-01

300

Interpretations and observations of ocean wave spectra  

Microsoft Academic Search

The paper starts with a discussion of the linear stochastic theory of ocean waves and its various nonlinear extensions. The\\u000a directional spectrum, with its unique dispersion relation connecting frequency (?) and wavenumber (k), is no longer valid for nonlinear waves, and examples of -spectra based on analytical expressions and computer simulations of nonlinear waves are presented. Simulations of the dynamic

Harald Elias Krogstad; Karsten Trulsen

2010-01-01

301

Energy Loss Spectra in Planar Channeling.  

National Technical Information Service (NTIS)

Using simple models for the motion of particles in planar channels and for the energy loss and its dependence on the path, energy loss spectra of particles transmitted through thin foils in planar channels are calculated. A comparison with measurements is...

S. Steenstrup A. P. Pathak

1980-01-01

302

FT-IR spectra of inorganic borohydrides  

NASA Astrophysics Data System (ADS)

Inorganic compounds with BH4- ions are the subject of many recent investigations in the context of potential hydrogen storage materials. In this work, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra of a series of reference and research compounds (including deuterated samples) are collected and made available to the research community.

D'Anna, Vincenza; Spyratou, Alexandra; Sharma, Manish; Hagemann, Hans

2014-07-01

303

Time of flight spectra in chemisorption  

NASA Astrophysics Data System (ADS)

Phenomenological models based on the master equation are analyzed to calculate the temperature and angular dependence of time of flight spectra in chemisorption. Strong deviations from Knudsen's cosine law and Maxwell's velocity distribution are produced. The Gaussian model seems of little relevance for the analysis of experimental data for which, in most cases, models incorporating activation barriers are needed.

Gortel, Z. W.; Kreuzer, H. J.; Wedler, G.; Schäff, M.

1984-07-01

304

Interpretation of Infrared Spectra, A Practical Approach  

NSDL National Science Digital Library

This 25-page PDF from John Coates discusses the basic rules of infrared spectral interpretation. The vibrational spectrum of a molecule is considered to be a unique physical property that can be used for identification purposes when compared to existing reference spectra. This is the basis for computer based spectral searching featured in this document.

Coates, John; Spectroscopynow.com

305

FT-IR spectra of inorganic borohydrides.  

PubMed

Inorganic compounds with BH4(-) ions are the subject of many recent investigations in the context of potential hydrogen storage materials. In this work, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra of a series of reference and research compounds (including deuterated samples) are collected and made available to the research community. PMID:24717677

D'Anna, Vincenza; Spyratou, Alexandra; Sharma, Manish; Hagemann, Hans

2014-07-15

306

EPR Spectra of Some Irradiated Polycrystalline Perrhenates.  

National Technical Information Service (NTIS)

An EPR study of the paramagnetic centers formed by gamma , electron and neutron irradiation of the NaReO sub 4 and KReO sub 4 was made. In the EPR spectra of the powder samples irradiated gamma , with electrons and neutrons, the presence of three types of...

N. G. Zaitseva M. Constantinescu R. Georgescu O. Constantinescu

1978-01-01

307

Microdosimetric spectra measurements of JANUS neutrons  

SciTech Connect

Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 ..mu..m) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs.

Marshall, I.R.; Williamson, F.S.

1985-01-01

308

Mid-Infrared Spectra of Martian Komantiite.  

National Technical Information Service (NTIS)

Synthetic mid-infrared emissive spectra of basalts of possible Martian komatiitic compositions were generated to show what might be seen in data returned from the Thermal Emission Spectrometer (TES). TES is flying on the Mars Observer arriving at Mars in ...

D. P. Reyes

1992-01-01

309

Atomic Spectra in a Helium Bubble  

Microsoft Academic Search

Density functional theory (DFT) is applied to atomic spectra under perturbations of superfluid liquid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and

Takashi Nakatsukasa; Kazuhiro Yabana; George F. Bertsch

2002-01-01

310

Liquid phase effects on benzene UV spectra  

NASA Astrophysics Data System (ADS)

Some results for the benzene molecular properties in liquid phase are shown, stressing the interest on the electronic spectra properties. The way we follow to perform calculations is a Semi-classical one. taking into account the structural information of the benzene pure liquid and the electronic structure of the benzene molecule at the CNDO level.

Se?e, L. M.; Botella, V.; Gómez, P. C.; Fernández, M.

1986-03-01

311

Theoretical Prediction of Raman and ROA Spectra  

NASA Astrophysics Data System (ADS)

Recent developments in the prediction of vibrational Raman and Raman optical activity (ROA) will be presented, with an emphasis on methods which are applicable to larger molecules and on the inclusion of solvent effects. The accuracy of the models for both gas-phase and solution spectra will be evaluated.

Frisch, Michael

2010-08-01

312

Fitting PAC spectra with a hybrid algorithm  

NASA Astrophysics Data System (ADS)

A hybrid algorithm (HA) that blends features of genetic algorithms (GA) and simulated annealing (SA) was implemented for simultaneous fits of perturbed angular correlation (PAC) spectra. The main characteristic of the HA is the incorporation of a selection criterion based on SA into the basic structure of GA. The results obtained with the HA compare favorably with fits performed with conventional methods.

Alves, M. A.; Carbonari, A. W.

2008-01-01

313

Fitting PAC spectra with a hybrid algorithm  

NASA Astrophysics Data System (ADS)

A hybrid algorithm (HA) that blends features of genetic algorithms (GA) and simulated annealing (SA) was implemented for simultaneous fits of perturbed angular correlation (PAC) spectra. The main characteristic of the HA is the incorporation of a selection criterion based on SA into the basic structure of GA. The results obtained with the HA compare favorably with fits performed with conventional methods.

Alves, M. A.; Carbonari, A. W.

314

Porphyrins XIII: Fluorescence spectra and quantum yields  

Microsoft Academic Search

Fluorescence spectra, quantum yields, natural radiative lifetimes, and absorption oscillator strengths are reported for a number of porphyrins in benzene solution. Emission yields for free base, Mg-, and Zn-phthalocyanine in 1-chloronaphthalene solution are also reported. The phthalocyanines are considerably more fluorescent than the porphyrins, and this is attributed mainly to their shorter radiative lifetimes. The heavy atom effect on fluorescence

Paul G. Seybold; Martin Gouterman

1969-01-01

315

Emission Spectra as a Combustion Diagnostic Tool  

Microsoft Academic Search

In the present work, spontaneous emission spectra of Liquefied Petroleum Gas (LPG) flames were used for combustion diagnostics. CH* and C2 * radicals were chosen as flame probe because these species shown a large optical emission in the visible spectrum region. Additionally, the occurrence of these radicals is strongly dependent of the flame composition. In rich flames, for which the

Dermeval Carinhana Junior; Juliana C. de Oliveira; Marcelo G. Destro; Alberto M. dos Santos

316

Determination of Particle Temperature from Emission Spectra  

Microsoft Academic Search

This paper discusses the fundamental possibility of determining the temperature of nanooxides in flames using thermal emission spectra. It is found that experimentally determined temperatures can be close to the real temperatures of particles only in the case of a high concentration of structural defects in the particles. It is shown that the energy accumulated in these defects should be

I. S. Altman

2004-01-01

317

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

318

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

319

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

320

Theory of recursive nuclear band spectra  

SciTech Connect

We first give a brief review of our earlier empirical work on parameter-free difference equations for nuclear spectra and discuss some of the implications. Then we show that a simple quantum mechanical model is capable of explaining and improving our previously suggested recursion relations.

Buck, B.; Merchant, A. C. [Department of Physics, University of Oxford, Theoretical Physics, 1 Keble Road, Oxford OX1 3NP (United Kingdom); Perez, S. M. [Department of Physics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa); iThemba LABS, P.O. Box 722, Somerset West 7129 (South Africa)

2010-03-15

321

Analytical Spectra of CMB Anisotropies and Polarization  

NASA Astrophysics Data System (ADS)

We briefly present the results of our analytical studies on CMB anisotropies and polarizations generated by scalar metric perturbations in synchronous gauge, parallel to the previous work with RGW as a generating source. The analytical the spectra ClXX are explicitly given and the influences of various cosmological processes are examined.

Zhang, Yang; Cai, Zheng

322

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

323

Physical parametrization of stellar spectra - The neural network approach  

Microsoft Academic Search

We present a technique that employs artificial neural networks to produce physical parameters for stellar spectra. A neural network is trained on a set of synthetic optical stellar spectra to give physical parameters. The network is then used to produce physical parameters for real, observed spectra. Our neural networks are trained on a set of 155 synthetic spectra, generated using

Coryn A. L. Bailer-Jones; Mike Irwin; Gerard Gilmore; Ted von Hippel

1997-01-01

324

Direct Analysis of Spectra of Type Ib Supernovae  

Microsoft Academic Search

Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to photospheric-phase spectra of Type Ib supernovae (SNe Ib). Although the synthetic spectra are based on simplifying approximations, including spherical symmetry, they account well for the observed spectra. Our sample of SNe Ib obeys a tight relation between the velocity at the photosphere, as determined from the Fe

David Branch; S. Benetti; Daniel Kasen; E. Baron; David J. Jeffery; Kazuhito Hatano; R. A. Stathakis; Alexei V. Filippenko; Thomas Matheson; A. Pastorello; G. Altavilla; E. Cappellaro; L. Rizzi; M. Turatto; Weidong Li; Douglas C. Leonard; Joseph C. Shields

2002-01-01

325

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

326

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

327

Mössbauer spectra of tin in float glass  

NASA Astrophysics Data System (ADS)

Tin is not a major constituent of window glass, but is found at high concentrations in the lower surface of float glass which has been in contact with the molten tin bath. It does not extend far into the surface, but causes the physical and chemical behaviour to differ from that of the upper surface. It is important, therefore, to understand the structural role of tin in silicate glasses and thus its effect on various properties. Mössbauer spectra were taken of three series of glassy materials, namely binary glasses (SnO and SiO2) in varying proportions, re-melted float glass containing tin, and float glass from a production plant. The binary glasses contained between 20 and 70% tin which was found to be mainly Sn2+, with very small amounts of Sn4+ in some of them. The spectra showed a small decrease in isomer shift with increase in tin content, which is ascribed to the change in molar volume. The re-melted samples were float glass which was mixed with stannous oxalate in appropriate conditions to try and maintain tin in the 2+ state, and contained up to 15% tin by weight. The spectra show both Sn4+ and Sn2+ with rather more in the 4+ oxidation state. The change in the spectra as a function of temperature revealed a large difference in the f-factor (and hence the chemical binding) of the two states. A series of spectra was taken between 17.5 and 900 K for the sample containing 15% tin. From the absorption as a function of temperature the f-factor was determined for both oxidation states, and hence enabled the relative amounts of Sn4+ and Sn2+ present in each sample to be estimated. Measurements of the shift as a function of temperature were also made. The float samples were surface material produced by grinding away all but 0.1 mm of the lower surface of industrially produced float glass. The Mössbauer spectra showed them to be predominantly Sn2+, as expected from the reducing atmosphere in the float plant. The concentration and oxidation state of the tin may be estimated from the value of the f-factors and isomer shifts.

Johnson, J. A.; Johnson, C. E.; Williams, K. F. E.; Holland, D.; Karim, M. M.

1995-12-01

328

Photoacoustic reflectivity spectra of layered semiconductors  

NASA Astrophysics Data System (ADS)

The Photoacoustic (PA) spectra in several layered compounds such as HfSe2, ZrS2, HfS2, WSe2, MoSe2 and MoS2 have been measured at energies above the fundamental absorption edge. In this optical region the PA signal is regarded to be independent of the optical absorption coefficient and the dips in the PA spectra may be ascribed to optical reflection effects inherent the band structure. Generally, our experimental data prove that the information on the band structure of the layered semiconductors is in good agreement with that obtainable by means of conventional spectroscopic techniques, and moreover it is comparable with the data which are usually obtained by means of modulatory spectroscopy.

Baldassarre, L.; Cingolani, A.

1988-03-01

329

QSOS with IPC X-Ray Spectra  

NASA Astrophysics Data System (ADS)

Observations with the Einstein IPC have produced a unique sample of 33 quasars with well determined soft x-ray spectra. 24 of these are bright enough to be observed with IUE. Our previous programs in years 8 and 9 have obtained spectra of many of the opticall-selected PG quasars In the IPC sample. With this proposal we aim to complete IUE coverage for the bright objects in the sample. This primarily requires observations of radio-laud quasars. The x-ray results show a clear difference In the properties of radio-loud and radio-quiet quasars. With the new data collected from this proposed program we can see if these differences extend into the neighboring ultraviolet region.

Elvis, Martin S.

330

Benchmarking statistical averaging of spectra with HULLAC  

NASA Astrophysics Data System (ADS)

Knowledge of radiative properties of hot plasmas is important for ICF, astrophysics, etc When mid-Z or high-Z elements are present, the spectra are so complex that one commonly uses statistically averaged description of atomic systems [1]. In a recent experiment on Fe[2], performed under controlled conditions, high resolution transmission spectra were obtained. The new version of HULLAC [3] allows the use of the same model with different levels of details/averaging. We will take advantage of this feature to check the effect of averaging with comparison with experiment. [1] A Bar-Shalom, J Oreg, and M Klapisch, J. Quant. Spectros. Rad. Transf. 65, 43 (2000). [2] J. E. Bailey, G. A. Rochau, C. A. Iglesias et al., Phys. Rev. Lett. 99, 265002-4 (2007). [3]. M. Klapisch, M. Busquet, and A. Bar-Shalom, AIP Conference Proceedings 926, 206-15 (2007).

Klapisch, Marcel; Busquet, Michel

2008-11-01

331

A comparative study of THz spectra  

NASA Astrophysics Data System (ADS)

We have constructed two types of THz spectrometers using the frequency-tunable THz wave generators based on difference-frequency generation (DFG) in GaP crystal. The OPO-source system is for high accuracy measurement to detect fine structures in THz absorption spectra. The Cr:F-source system has merit in simple structure, easy maintenance and low-cost, but still has sufficient resolution for room temperature observation of solids or liquids. Comparing the absorption spectra of saccharides measured with these spectrometers and those measured with FT-IR or TDS, our spectrometers have superiority in frequency range and resolution, enough to record sub peaks, which can be analyzed as structural defects in organic compounds.

Nishizawa, J.; Suto, K.; Sasaki, T.; Tanno, T.

332

Optical absorption spectra of ? in ? (YGG)  

NASA Astrophysics Data System (ADS)

Optical absorption spectra of trivalent europium in the rare-earth garnet 0953-8984/9/7/025/img3 (YGG) have been recorded between 4600 and 0953-8984/9/7/025/img4 at 77 and at 293 K. A total of 117 crystal-field transitions has been detected in the spectra. The symmetry of the 0953-8984/9/7/025/img5 site is 0953-8984/9/7/025/img6, so a total removal of the crystal-field degeneracy of the 0953-8984/9/7/025/img7 configuration can be expected. The energy level scheme of 0953-8984/9/7/025/img5 in YGG is parametrized in terms of 20 free-ion parameters and nine crystal-field parameters. The crystal field is strong in the garnet host, so J-mixing has to be taken into account for the crystal-field calculation.

Binnemans, K.; Görller-Walrand, C.

1997-02-01

333

Stellar Spectra in the H Band  

NASA Astrophysics Data System (ADS)

The H band is a region of the infrared centered at wavelength 1.65 microns in a clear window between atmospheric absorption bands. Cool stars such as Mira variables are brightest in this band, and the amplitudes of the light curves of Miras are typically 5 times smaller in H than in V. Since the AAVSO is currently exploring the possibility of distributing H-band photometers to interested members, it is of interest to examine the stellar spectra that these photometers would measure. In most red giant stars, the strongest spectral features in the H band are a set of absorption bands due to the CO molecule. Theoretical spectra calculated from model atmospheres are used to illustrate the pronounced flux peak in H which persists over a wide range of temperature. The models also show that the light in the H band emerges from deeper layers of the star's atmosphere than the light in any other band.

Wing, R. F.; Jorgensen, U. G.

2003-12-01

334

Analysis of spectra using correlation functions  

NASA Technical Reports Server (NTRS)

A novel method is presented for the quantitative analysis of spectra based on the properties of the cross correlation between a real spectrum and either a numerical synthesis or laboratory simulation. A new goodness-of-fit criterion called the heteromorphic coefficient H is proposed that has the property of being zero when a fit is achieved and varying smoothly through zero as the iteration proceeds, providing a powerful tool for automatic or near-automatic analysis. It is also shown that H can be rendered substantially noise-immune, permitting the analysis of very weak spectra well below the apparent noise level and, as a byproduct, providing Doppler shift and radial velocity information with excellent precision. The technique is in regular use in the Atmospheric Trace Molecule Spectroscopy (ATMOS) project and operates in an interactive, realtime computing environment with turn-around times of a few seconds or less.

Beer, Reinhard; Norton, Robert H.

1988-01-01

335

Noise spectra of an interacting quantum dot  

NASA Astrophysics Data System (ADS)

We study the noise spectra of a many-level quantum dot coupled to two electron reservoirs, when interactions are taken into account only on the dot within the Hartree-Fock approximation. The dependence of the noise spectra on the interaction strength, the coupling to the leads, and the chemical potential are derived. For zero bias and zero temperature, we find that as a function of the (external) frequency, the noise exhibits steps and dips at frequencies reflecting the internal structure of the energy levels on the dot. Modifications due to a finite bias and finite temperatures are investigated for a noninteracting two-level dot. Possible relations to experiments are pointed out.

Gabdank, N.; Rothstein, E. A.; Entin-Wohlman, O.; Aharony, A.

2011-12-01

336

Ab initio infrared and Raman spectra  

NASA Technical Reports Server (NTRS)

It is pointed out that with increased computer power and improved computational techniques, such as the gradients developed in recent years, it is becoming practical to compute spectra ab initio, from the fundamental constants of nature, for systems of increasing complexity. The present investigation has the objective to explore several possible ab initio approaches to spectra, giving particular attention to infrared and nonresonance Raman. Two approaches are discussed. The sequential approach, in which first the electronic part and then later the nuclear part of the Born-Oppenheimer approximation is solved, is appropriate for small systems. The simultaneous approach, in which the electronic and nuclear parts are solved at the same time, is more appropriate for many-atom systems. A review of the newer quantum gradient techniques is provided, and the infrared and Raman spectral band contours for the water molecule are computed.

Fredkin, D. R.; White, S. R.; Wilson, K. R.; Komornicki, A.

1983-01-01

337

Sulphur compounds in cometary IUE spectra  

NASA Technical Reports Server (NTRS)

From a study of cometary IUE spectra, a tentative identification of bands of the B-X systems of the SO molecule in the comet IRAS-Araki-Alcock in the 2200-2400 A region is reported, and it is suggested that sulphur compounds are more prevalent in comets than has been previously realized. S(+) and possibly SH are evident in comet Halley spectra, and new bands in the (A-X) system of CS and the (B-X) system of S2 are identified. The present results throw doubts on previous assessments of dust abundances from scattered continua in the 2900-3000 A region. The relatively strong abundance of S2 compared to OH in the Cernis and Bowell comets suggests that S2 is not well mixed and is not bound in H2O-ice.

Krishna Swamy, K. S.; Wallis, M. K.

1987-01-01

338

Neutron Spectra in a 15 MV LINAC  

NASA Astrophysics Data System (ADS)

Neutron spectra were calculated inside the treatment hall of a 15 MV LINAC, calculations were carried out using Monte Carlo methods. With a Bonner sphere spectrometer with pairs of thermoluminiscent dosimeters the neutron spectrum at 100 cm from the isocenter was measured and compared with the calculated spectrum. All the spectra in the treatment hall show the presence of evaporation and knock-on neutrons; also the room-return due to the hall features is shown. In the maze the large contribution are due to epithermal and thermal neutrons. A good agreement between the calculated and measured spectrum at 100 cm was noticed, from this comparison the differences are attributed to the water content in the concrete of the hall.

Vega-Carrillo, H. R.; Chu, Wei-Han; Tung, Chuan-Jong; Lan, Jen-Hong

2010-12-01

339

Slit spectra of second Byurakan survey galaxies  

NASA Astrophysics Data System (ADS)

Slit spectra have been obtained at Lick Observatory of 18 Seyfert galaxy candidates from the Second Byurakan Spectral Sky Survey (SBS). The great majority of them turned out to be Seyfert galaxies. The classifications and redshifts of all the galaxies are reported. Measurements ofthe intensity ratios of the emission lines used in classifying the galaxies are tabulated and plotted on diagnostic diagrams. The spectra of seven of the galaxies are described in detail. In general, our classification and redshift measurements are in very good accord with those of Lipovestsky, Stepanian, and their collaborators at the Special Astrophysical Observatory, showing that their results can be used in conjunction with the Lick results with little if any systematic differences between the two data sets. The importance of the SBS as a source of new Seyferts bridging the gap between low-redshift Seyfert galaxies and higher luminosity Quasi-Stellar Objects (QSOs) is also emphasized.

Martel, Andre; Osterbrock, Donald E.

1994-04-01

340

Slit Spectra of Second Byurakan Survey Galaxies  

NASA Astrophysics Data System (ADS)

Slit spectra have been obtained at Lick Observatory of 18 Seyfert galaxy candidates from the Second Byurakan Spectral Sky Survey (SBS). The great majority of them turned out to be Seyfert galaxies. The classifications and redshifts of all the galaxies are reported. Measurements of the intensity ratios of the emission lines used in classifying the galaxies are tabulated and plotted on diagnostic diagrams. The spectra of seven of the galaxies are described in detail. In general, our classification and redshift measurements are in very good accord with those of Lipovetsky, Stepanian, and their collaborators at the Special Astrophysical Observatory, showing that their results can be used in conjunction with the Lick results with little if any systematic difference between the two data sets. The importance of the SBS as a source of new Seyferts bridging the gap between low-redshift Seyfert galaxies and higher-luminosity QSOs is also emphasized.

Osterbrock, D. E.; Martel, A.

1993-12-01

341

Cathodoluminescence spectra of gallium nitride nanorods  

PubMed Central

Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

2011-01-01

342

Electron spectra of radical cations of heteroanalogs  

SciTech Connect

Radical cation spectra of indazole and benzothiophene in the visible region were obtained by laser photolysis during the reaction of photoexcited quinones with these compounds in acetonitrile. The charge transfer bands of the complexes of the test compounds with p-chloranil and 7,7,8,8-tetracyanoquinodimethane in dioxane were recorded on a Specord M-40. Photoelectron spectra were obtained on a ES-3201 electron spectrometer. The He(I) resonance band (21.21 eV) was used for excitation. Measurements were carried out in the 60-120/sup 0/C range. The energy scale was calibrated form the first ionization potentials of Ar (15.76 eV) and chlorobenzene (9.06 eV). The error in the determination of the ionization potentials for the first four photoelectron bands was 0.05 eV.

Petrushenko, K.B.; Turchaninov, V.K.; Vokin, A.I.; Ermikov, A.F.; Frolov, Yu.L.

1985-12-01

343

Primordial power spectra from anisotropic inflation  

SciTech Connect

We examine cosmological perturbations in a dynamical theory of inflation in which an Abelian gauge field couples directly to the inflaton, breaking conformal invariance. When the coupling between the gauge field and the inflaton takes a specific form, inflation becomes anisotropic and anisotropy can persist throughout inflation, avoiding Wald's no-hair theorem. After discussing scenarios in which anisotropy can persist during inflation, we calculate the dominant effects of a small persistent anisotropy on the primordial gravitational wave and curvature perturbation power spectra using the ''in-in'' formalism of perturbation theory. We find that the primordial power spectra of cosmological perturbations gain significant direction dependence and that the fractional direction dependence of the tensor power spectrum is suppressed in comparison to that of the scalar power spectrum.

Dulaney, Timothy R.; Gresham, Moira I. [California Institute of Technology, Pasadena, California 91125 (United States)

2010-05-15

344

Raman spectra of deuteriated taurine single crystals  

NASA Astrophysics Data System (ADS)

The polarized Raman spectra of partially deuteriated taurine [(ND 3+) 0.65(NH 3+) 0.35(CH 2) 2SO 3-] crystals from x( zz) x and x( zy) x scattering geometries of the A g and B g irreducible representations of the factor group C 2h are reported. The temperature-dependent Raman spectra of partially deuteriated taurine do not reveal any evidence of the structural phase transition undergone by normal taurine at about 250 K, but an anomaly observed in the 180 cm -1 band at ˜120 K implies a different dynamic for this band (which is involved in a pressure-induced phase transition) in the deuteriated crystal.

Souza, J. M. de; Lima, R. J. C.; Freire, P. T. C.; Sasaki, J. M.; Melo, F. E. A.; Filho, J. Mendes; Jones, Derry W.

2005-05-01

345

Electric field representation of pulsar intensity spectra  

NASA Astrophysics Data System (ADS)

Pulsar dynamic spectra exhibit high-visibility fringes arising from interference between scattered radiowaves. These fringes may be random or of highly ordered patterns, depending on the nature of the scattering or refraction. Here we consider the possibility of decomposing pulsar dynamic spectra - which are intensity measurements - into their constituent scattered waves, i.e. electric field components. We describe an iterative method of achieving this decomposition and show how the algorithm performs on data from the pulsar B0834+06. The match between model and observations is good, although not formally acceptable as a representation of the data. Scattered wave components derived in this way are immediately useful for qualitative insights into the scattering geometry. With some further development, this approach can be put to a variety of uses, including: imaging the scattering and refracting structures in the interstellar medium; interstellar interferometric imaging of pulsars at a very high angular resolution and mitigating pulse arrival time fluctuations due to interstellar scattering.

Walker, M. A.; Stinebring, D. R.

2005-10-01

346

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

347

Vibrational spectra and force field of dimethylphosphines  

NASA Astrophysics Data System (ADS)

Vibrational spectra in the range 200-3000 cm -1 are reported and assigned for the species (CH 3) 2PH, (CH 3) 2PD, (CD 3) 2PH, (CD 3) 2PD, CH 3CD 3PH and CH 3CD 3PD. The spectra in the range 1020-500 cm -1 are complicated due to the coupling between ?PH, ?Me and the skeletal modes of the molecule. Interpretation is only possible through a force field which is markedly different from an earlier one of dimethyl sulphide. This force field predicts uncoupled ?PH frequencies of 835 ( a) and 909 cm -1 ( a), couples PH bending largely to out-of-skeletal plane methyl rocking (? i) and includes a low p¦¦( a) bending constant, a high skeletal bending constant and unusual signs for two interaction constants. In the crystalline phase at 78 K, the two methyl groups are non-equivalent.

McKean, D. C.; McQuillan, G. P.

1980-04-01

348

Raman spectra of seven interplanetary dust particles  

NASA Technical Reports Server (NTRS)

The Raman shift spectra of seven interplanetary dust particles, U2034(F10), U2034(F8), U2022(B1), W7074 18, W7074 C15, W7074 C3 and W7074 A7, were measured with a Spex-1403 Raman spectrograph. The exciting radiations were the 488 nm and 514 nm line of a 5W argon ion laser. All seven spectra exhibit the 1350 and 1600 Delta/cm arbon bands, implying that the Interplanetary dust particles were coated with hydrocarbon and incompletely crystallized carbon, the part of which may be the residue of hydrocarbon contents in the particles after water loss by the heating during their entry into the earth's atmosphere. A weak band structure in the 520-610/cm range could be caused by cyclosilicates, and a weak band at 2900/cm is tentatively identified as due to hydrocarbon molecules.

Xu, Yin-Lin; Yu, Min; Fan, Chang-Yun

1992-01-01

349

Optical Absorption Spectra of Nanocrystal Gold Molecules  

Microsoft Academic Search

The optical absorption spectra of a series of nanocrystal gold moleculesslarger, crystalline Au clusters that are passivated by a compact monolayer of n-alkylthiol(ate)sshave been measured across the electronic range (1.1-4.0 eV) in dilute solution at ordinary temperature. Each of the20 samples, ranging in effective core diameter from 1.4 to 3.2 nm (70 to800 Au atoms), has been purified by fractional

Marcos M. Alvarez; Joseph T. Khoury; T. Gregory Schaaff; Marat N. Shafigullin; Igor Vezmar; Robert L. Whetten

1997-01-01

350

GAMANAL. Interpretation of Gamma-Ray Spectra  

Microsoft Academic Search

GAMANAL provides a complete qualitative and quantitative analysis of mixtures of radioactive species such as fission products by computer interpretation of high-resolution gamma-ray spectra. The program first determines and removes the background or Compton continuum under the peaks in a spectrum to locate the peak regions. This is done by examining the pulse-height spectrum data for background and peak regions

Gunnink

1986-01-01

351

Ultraviolet photoelectron spectra of cesium halides  

Microsoft Academic Search

Energy distributions of photoelectrons from evaporated films of cesium halides were measured at photon energies of 11-23 eV. The photoelectron spectra show structures that can be identified as relatively high densities of states in the Cs+ 5p core as well as in the valence and conduction bands. Doublet core states due to spin-orbit splitting are observed for all the cesium

Jerel A. Smith; W. Pong

1975-01-01

352

Reanalysis of Tyrannosaurus rex Mass Spectra  

PubMed Central

Asara et al. reported the detection of collagen peptides in a 68-million-year-old T. rex bone by shotgun proteomics. This finding has been called into question as a possible statistical artifact. We reanalyze Asara et al.'s tandem mass spectra using a different search engine and different statistical tools. Our reanalysis shows a sample containing common laboratory contaminants, soil bacteria, and bird-like hemoglobin and collagen.

Bern, Marshall; Phinney, Brett S.; Goldberg, David

2009-01-01

353

Aladin, VO standards, Spectra and data cubes  

NASA Astrophysics Data System (ADS)

Aladin can be used as a VO portal for 3D spectroscopy DAL services. The new release is able to ingest data cubes and display them in movie mode. Lambda maps and spectra at one position can be excerpted. SIA services retrieving data cubes allow to describe in the metadata tree several access modes to the same dataset via DAL query response extensions. Interaction with tools like VOSPEC and SPLAT via PLASTIC protocol is emphasized.

Boch, T.; Fernique, P.; Bonnarel, F.

2008-10-01

354

M dwarf flare spectra (Kowalski+, 2013)  

NASA Astrophysics Data System (ADS)

The spectral data are contained in FITS files (to be read into IDL with mrdfits.pro), and the photometry data are contained in two column .dat files. Spectra were obtained with the Dual-Imaging Spectrograph (DIS) on the ARC 3.5m telescope at the Apache Point Observatory (APO) in low-resolution. The observing log for each target star is given in Table 2. (5 data files).

Kowalski, A. F.; Hawley, S. L.; Wisniewski, J. P.; Osten, R. A.; Hilton, E. J.; Holtzman, J. A.; Schmidt, S. J.; Davenport, J. R. A.

2013-06-01

355

Transient absorption spectra of 2-hydroxybenzophenone photostabilizers  

NASA Astrophysics Data System (ADS)

Transient absorption spectra (400-600 nm) of 2-hydroxybenzophenone and the methyl methacrylate copolymer of 2-hydroxy, 3-allyl, 4,4'-dimethoxybenzophenone following 355 nm excitation (7-480 ps delay) are reported. A short-lived, 435 nm transient (? ? 10 ps in CH 2Cl 2) for both molecules is assigned to the lowest excited singlet before internal proton transfer. Weaker, broad T-T absorption is observed after 480 ps.

Merritt, Charles; Scott, Gary W.; Gupta, Amitava; Yavrouian, Andre

1980-01-01

356

Increased Elemental Specificity of Positron Annihilation Spectra  

Microsoft Academic Search

Positron annihilation spectroscopy (PAS) is a sensitive probe for studying the electronic structure of defects in solids. We show that the high-momentum part of the Doppler-broadened annihilation spectra can be used to distinguish different elements. This is achieved by using a new two-detector coincidence system to examine the line shape variations originating from high-momentum core electrons. Because the core electrons

P. Asoka-Kumar; M. Alatalo; V. J. Ghosh; A. C. Kruseman; B. Nielsen; K. G. Lynn

1996-01-01

357

Optimal databased complex demodulation for evolutionary spectra  

Microsoft Academic Search

Complex demodulation of evolutionary spectra is formulated as a two-dimensional kernel smoother in the time-frequency domain. A tapered Fourier transform is calculated, and the log-spectral estimate is smoothed. As the characteristic widths of the kernel smoother increase, the bias from temporal and frequency averaging increases while the variance decreases. The demodulation parameters are chosen by minimizing the expected error using

K. S. Riedel

1992-01-01

358

On the information content of stellar spectra  

NASA Astrophysics Data System (ADS)

With the increasing quality of asteroseismic observations it is important to minimize the random and systematic errors in mode parameter estimates. To this end it is important to understand how the oscillations relate to the directly observed quantities, such as intensities and spectra, and to derived quantities, such as Doppler velocity. Here I list some of the effects we need to take into account and show an example of the impact of some of them.

Schou, Jesper

2014-02-01

359

A comparative study of THz spectra  

Microsoft Academic Search

We have constructed two types of THz spectrometers using the frequency-tunable THz wave generators based on difference-frequency generation (DFG) in GaP crystal. The OPO-source system is for high accuracy measurement to detect fine structures in THz absorption spectra. The Cr:F-source system has merit in simple structure, easy maintenance and low-cost, but still has sufficient resolution for room temperature observation of

Jun-ichi NISHIZAWA; Ken SUTO; Tetsuo SASAKI; Takenori TANNO

2005-01-01

360

Optical spectra of FLASH generated plasmas  

NASA Astrophysics Data System (ADS)

Time integrated measurements of optical spectra of the plasma generated by pulses of the free electron laser facility FLASH on a solid target at DESY Hamburg are interpreted in terms of plasma hydrodynamics. It is shown that the main contribution to the optical range comes from the expanding stage of the plasma evolution on a ns scale, whereas the UV part is partially obscured by the optically dense outstreaming plasma near the ablated hole.

Stránský, M.; Rohlena, Karel

2014-05-01

361

Bayesian Source Separation for PAH Spectra  

NASA Astrophysics Data System (ADS)

The Aromatic Infrared Bands (AIBs) are prominent features of many galactic spectra in the infrared and are strongly associated with star-forming regions. Polycyclic Aromatic Hydrocarbons (PAHs) are a leading contender as the source for this emission. Unequivocally establishing this identification has been difficult since the AIBs do not appear to be the result of emission from a small, tractable number of PAHs. Rather the observed emission bands appear to be composed of the contributions from possibly hundreds of different PAHs, neutral and ionized, each with its own distinctive spectrum. A major step toward verifying the PAH hypothesis would be to quantitatively establish how well the observed AIBs can be explained, or not explained, as the combination of known PAH spectra. To date this problem has been attacked by either manually superimposing individual PAH spectra or by using non-negative least squares. We explain how both of these approaches have serious deficiencies. We then describe our progress in applying Bayesian source separation techniques to this difficult problem. In this phase of our investigation, we have worked with theoretically generated PAH spectra at a single temperature composed of combinations of arbitrarily selected PAHs with added Gaussian noise. First, we show how the non-negative least squares approach fares as a function of PAH composition, noise level, and spectral resolution. Next, we outline our Bayesian approach, which relies on Skilling's nested sampling algorithm. This approach allows us to find highly probable solutions and evaluate the uncertainties in our estimates by sampling the posterior. Moreover, this algorithm also enables us to compute the evidence provided by the data as well as visualize the posterior probability in the high-dimensional hypothesis space generated by the numerous combinations of possible PAH contributions. This research is supported by NASA Applied Information Systems Research Grant 05-AISR05-0143.

Carbon, Duane F.; Tse, M. K.; Knuth, K. H.

2006-12-01

362

Deconvolution of diode-laser spectra  

NASA Technical Reports Server (NTRS)

A new technique has been developed for deconvolving diode-laser spectra. This technique treats Doppler broadening, collisional broadening, and instrumental effects simultaneously. This technique is superior to previous deconvolution methods in the recovery of line-strength and transition-frequency information. A section of the ethane spectrum near 12 microns is used as an example. This new approach applies to any spectroscopy in which the instrumental resolution is narrower than actual linewidths.

Halsey, G. W.; Jennings, D. E.; Blass, W. E.

1985-01-01

363

Spectra classification based on kernel methods  

NASA Astrophysics Data System (ADS)

The star/galaxy/quasar (qso) classification according to spectra in astronomy is basic and important step in LAMOST project. It is proposed that two algorithms based on the KPCA and the GDA to classify star, galaxy and quasar in this paper. For the performance of classification, the experiments show that the KPCA is slightly better than the PCA; the GDA is also slightly better than the LDA, and it is significantly better than the KPCA.

Xu, Xin; Duan, Fuqing; Luo, Ali

2005-11-01

364

EPR Spectra of Modified Iron Oxides  

Microsoft Academic Search

EPR spectra of iron oxides, obtained by calcination of iron oxide-hydroxides a-, ß-, ?- and d-FeOOH, and ruthenium catalysts based on them (Ru\\/Fe2O3 and Ru\\/Na-Fe2O3), used for the water-gas shift reaction (WGSR), were analyzed. The iron oxide (B) (obtained from ß-FeOOH) is inactive in WGSR. Deposition of ruthenium on iron oxide supports, in particular on those modified with sodium, enhanced

Anna Basi?ska; Wanda Wójtowicz; Andrzej B. Wi?ckowski; Florian Domka

2000-01-01

365

Photoelectron spectra from K and Na clusters  

NASA Astrophysics Data System (ADS)

We discuss photoelectron spectra (PES) of Na and K clusters for various charge states and various sizes. The PES were obtained in dynamical calculations with time-dependent local-density approximation (TDLDA) augmented with a self-interaction correction to arrange the correct ionization properties. Comparison with experimental data shows that TDLDA provides generally a pertinent description. A few deviations for very small systems hint at final state correlations which go beyond a mean-field description.

Pohl, A.; Reinhard, P.-G.; Suraud, E.

2003-11-01

366

Turbulent velocity spectra in superfluid flows  

Microsoft Academic Search

We present velocity spectra measured in three cryogenic liquid 4He steady flows: grid and wake flows in a pressurized wind tunnel capable of achieving mean velocities up to 5 m\\/s at temperatures above and below the superfluid transition, down to 1.7 K, and a ``chunk'' turbulence flow at 1.55 K, capable of sustaining mean superfluid velocities up to 1.3 m\\/s.

J. Salort; C. Baudet; B. Castaing; B. Chabaud; F. Daviaud; T. Didelot; P. Diribarne; B. Dubrulle; Y. Gagne; F. Gauthier; A. Girard; B. Hébral; B. Rousset; P. Thibault; P.-E. Roche

2010-01-01

367

Ultraviolet spectra of R Coronae Borealis stars  

NASA Technical Reports Server (NTRS)

An analysis of the International Ultraviolet Explorer spectra of the R CrB-type variables R CrB, RY Sgr, XX Cam, and MV Sgr suggests that: (1) it should be possible to construct useful models for the atmospheres of these hydrogen deficient, carbon rich stars if present standards of metallic line blanketing are used; and (2) the observed wavelength dependence of the circumstellar extinction is primarily due to circumstellar grains.

Holm, A. V.; Wu, C. C.

1982-01-01

368

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

369

Optical spectra analysis for breast cancer diagnostics  

NASA Astrophysics Data System (ADS)

Minimally invasive probe and optical biopsy system based on optical spectra recording and analysis seem to be a promising tool for early diagnostics of breast cancer. Light scattering and absorption spectra are generated continuously as far as the needle-like probe with one emitting and several collecting optical fibers penetrates through the tissues toward to the suspicious area. That allows analyzing not only the state of local site, but also the structure of tissues along the needle trace. The suggested method has the advantages of automated on-line diagnosing and minimal tissue destruction and in parallel with the conventional diagnostic procedures provides the ground for decision-making. 165 medical trials were completed in Nizhny Novgorod Regional Oncology Centre, Russia. Independent diagnoses were the results of fine biopsy and histology. Application of wavelet expansion and clasterization techniques for spectra analysis revealed several main spectral types for malignant and benign tumors. Automatic classification algorithm demonstrated specificity ˜90% and sensitivity ˜91%. Large amount of information, fuzziness in criteria and data noisiness make neural networks to be an attractive analytic tool. The model based on three-layer perceptron was tested over the sample of 29 `cancer' and 29 `non-cancer' cases and demonstrated total separation.

Belkov, S. A.; Kochemasov, G. G.; Lyubynskaya, T. E.; Maslov, N. V.; Nuzhny, A. S.; da Silva, L. B.; Rubenchik, A.

2011-11-01

370

Pure cyclotron spectra of V405 Aur  

NASA Astrophysics Data System (ADS)

In this study we investigate the pure cyclotron spectra of an Intermediate Polar (IP), V405 Aur, which has the highest magnetic field strength in its class. Recent studies have shown that cyclotron harmonics are seen in the spectra of V405 Aur. We assume that cyclotron harmonics are produced by electrons having a streaming bi-Maxwellian velocity profile found in the lower portions of the accretion column connecting to the magnetic poles of the white dwarf in V405 Aur system. Then we applied the Green function for a dispersive medium such as the one found in V405 Aur. Further we assume that the cyclotron radiation is produced at Ordinary and Extraordinary wave modes. We find the general solution of the Green function for the Extraordinary wave mode and a dispersive medium and we derived the pure cyclotron spectra from the Green function. This function enabled us to calculate energy radiated per unit wavelength per unit solid angle as a function of wavelength which revealed the sixth, seventh and the eighth harmonics which correspond to the observed values. Our model produces the observed cyclotron spectrum of V405 Aur.

Tutar, Demet; Rennan Pekünlü, E.

2013-02-01

371

Haloes Seen In UVIS Reflectance Spectra  

NASA Astrophysics Data System (ADS)

UVIS SOI reflectance spectra show bright ‘haloes’ around the locations of some of the strongest resonances in Saturn’s A ring (Esposito etal 2005). UV spectra constrain the size and composition of the icy ring particles (Bradley etal 2010, 2012). We investigate the Janus 4:3, 5:3, 6:5 and Mimas 5:3 inner Lindblad resonances as well as at the Mimas 5:3 vertical resonance (bending wave location). Models of ring particle regolith evolution (Elliott and Esposito 2010) indicate the deeper regolith is made of older and purer ice. The strong resonances cause streamline crowding (Lewis and Stewart 2005) which damps the interparticle velocity, allowing temporary clumps to grow, which in turn increase the velocity, eroding the clumps and releasing smaller particles and regolith (see the predator-prey model of Esposito etal 2012). This cyclic behavior, driven by the resonant perturbation from the moon, can yield collision velocities greater than 1m/sec, sufficient to erode the aggregates (Blum 2006), exposing older, purer materials. Thus, the radial location of the strongest resonances can be where we find both large aggregates and disrupted fragments, in a balance maintained by the periodic moon forcing. If this stirring exposes older, and purer ice, the velocity threshold for eroding the aggregates can explain why only the strongest Lindblad resonances show haloes. UVIS spectra can determine the relative contributions of particle size and purity at these locations, for comparison to estimates from the regolith evolution models.

Esposito, Larry W.; Bradley, E.; Colwell, J.; Sremcevic, M.

2012-10-01

372

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

373

Resonance Raman Spectra of Photodissociated Hemoglobins  

PubMed Central

Resonance Raman spectra at cryogenic temperatures of photodissociated hemoglobins and the corresponding deoxygenated preparations are compared and significant differences are found in modes with contributions from peripheral substituents of the heme as well as in the iron-histidine stretching mode. These differences in heme vibrational spectra reflect differences in the tertiary structure of the heme pocket between deoxyhemoglobin and the CO-bound form. An analysis of the effects of cooperative energy storage on the tertiary structure around the heme is made and used to interpret this resonance Raman data. The differences between the spectra of the deoxygenated preparations and the photoproducts provide evidence that a fraction of the free energy of cooperativity, ?G, is located away from the heme. These data support models for cooperativity in which the cooperative energy is distributed over many bonds or is localized in protein bonds only, such as those at the subunit interface. In addition, the local changes in amino acid positions, which must occur following the change in the state of ligand binding, may drive the changes in the structural relationships of the subunits and hence form one of the initial steps for triggering the quaternary structure transition.

Rousseau, D. L.; Ondrias, M. R.

1985-01-01

374

Soil emissivity and reflectance spectra measurements  

SciTech Connect

We present an analysis of the laboratory reflectance and emissivity spectra of 11 soil samples collected on different field campaigns carried out over a diverse suite of test sites in Europe, North Africa, and South America from 2002 to 2008. Hemispherical reflectance spectra were measured from 2.0 to 14 {mu}m with a Fourier transform infrared spectrometer, and x-ray diffraction analysis (XRD) was used to determine the mineralogical phases of the soil samples. Emissivity spectra were obtained from the hemispherical reflectance measurements using Kirchhoff's law and compared with in situ radiance measurements obtained with a CIMEL Electronique CE312-2 thermal radiometer and converted to emissivity using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) temperature and emissivity separation algorithm. The CIMEL has five narrow bands at approximately the same positions as the ASTER. Results show a root mean square error typically below 0.015 between laboratory emissivity measurements and emissivity measurements derived from the field radiometer.

Sobrino, Jose A.; Mattar, Cristian; Pardo, Pablo; Jimenez-Munoz, Juan C.; Hook, Simon J.; Baldridge, Alice; Ibanez, Rafael

2009-07-01

375

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

376

IRAS Low Resolution Spectra of Asteroids  

NASA Astrophysics Data System (ADS)

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.

2002-04-01

377

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

378

IUE-newsips spectra of sigma Geminorum  

NASA Astrophysics Data System (ADS)

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 low dispersion. The emission lines, identified as activity indicators and originating in the chromosphere and transition region, are seen in the spectra. The emission line fluxes and equivalent widths are computed based on Gaussian profile fitting procedures to examine the existence of any line flux variation that depends on time or orbital phase. It was found that there is a flux variation with time and orbital phase that is in good agreement with the photometric light curve variation. By comparing the flux variation with simultaneous light curve variation, it can be shown that there is a relation between the ultraviolet flux variation and the spot activity of the system, as shown by Ayres et al. (1984) and Engvold et al. (1988) based on their IUE (with IUESIPS reduction) spectral analysis. Moreover, it was inferred that there is no ultraviolet excess in sigma Gem by comparing the spectra of beta Gem taken as a comparison star. The Mg II h and k radial velocity curves of sigma Gem were in a good agreement with data obtained by Eker (1986) and Duemmler et al. (1997). The sinusoidal Mg II radial velocity curve solutions of the system give e = 0, P_orb. = 19.607+/-0.008 days, K = 34.86+/- 2.33 km s-1, gamma = 49.42+/- 1.87 km s-1 and T_o = 2445972.53+/- 0.28. Since the ultraviolet flux data are not conveniently distributed and are insufficient to determine the activity cycle, the evaluation of the ultraviolet flux activity cycle was not successful. Tables 3 to 11 are 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/391/641. Figures 1 to 10 are only available in electronic form at http://www.edpsciences.org

Ekmekçi, F.; Karaku?, O.

2002-08-01

379

Fault depth and seismic moment rate estimates of the San Andreas Fault System: Observations from seismology and geodesy  

Microsoft Academic Search

The depth of the seismogenic zone is a critical parameter for earthquake hazard models of the San Andreas Fault System. Independent observations from both seismology and geodesy can provide insight into the depths of faulting, however these depths do not always agree. Here we inspect variations in fault depths of 12 segments of the southern San Andreas Fault System derived

B. R. Smith-Konter; D. T. Sandwell; P. M. Shearer

2010-01-01

380

Near-infrared spectra of Jupiter, Saturn, and Uranus  

NASA Technical Reports Server (NTRS)

Near infrared spectra of Jupiter, Saturn, and Uranus were measured at resolutions higher than previously available in the range from 6,000 to 10,750/cm. The resolution was 0.5/cm for Jupiter and Saturn, and 32/cm for Uranus. The spectra are presented both individually and as ratio spectra, in which the planetary spectra are divided by the solar spectrum. The Uranus spectrum is shown with Saturn, Jupiter, and Sun spectra reduced to the same resolution so that Uranus can be compared with the other outer planets. The high resolution Saturn, Jupiter, and Sun spectra are presented in parallel plots to simplify comparisons between them.

Potter, A. E.

1974-01-01

381

Unbiased Recursive Partitioning: A Conditional Inference Framework  

Microsoft Academic Search

Recursive binary partitioning is a popular tool for regression analysis. Two fundamental problems of exhaustive search procedures usually applied to fit such models have been known for a long time: overfitting and a selection bias towards covariates with many possible splits or missing values. While pruning procedures are able to solve the overfitting problem, the variable selection bias still seriously

Torsten Hothorn; Kurt Hornik; Wirtschaftsuniversitat Wien; Achim Zeileis

2006-01-01

382

Unbiased Coin Tossing with a Biased Coin  

Microsoft Academic Search

Procedures are exhibited and analyzed for converting a sequence of i.i.d. Bernoulli variables with unknown mean $p$ into a Bernoulli variable with mean $\\\\frac{1}{2}$. The efficiency of several procedures is studied.

Wassily Hoeffding; Gordon Simons

1970-01-01

383

Unbiased COIN Tossing with a Biased Coin.  

National Technical Information Service (NTIS)

Procedures are exhibited and analyzed for converting a sequence of independent, identically distributed random variables with unknown mean p into a Bernoulli variable with mean 1/2. Repeated application of any of these procedures produces a Bernoulli sequ...

W. Hoeffding G. Simons

1969-01-01

384

Efficient Techniques for Unbiasing a Bernoulli Generator.  

National Technical Information Service (NTIS)

Consider the problem of operating on a sequence of i.i.d. Bernoulli variables with unknown mean p to produce a sequence of symmetric Bernoulli variables. Define the efficiency of any proposed method to be the average number of output digits per input digi...

J. A. Lechner

1971-01-01

385

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[W][OA  

PubMed Central

Treating wounds in Nicotiana attenuata leaves with Manduca sexta oral secretions (W+OS) 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 and by the alkalinity of OS were assessed by applying a buffer known to mimic the pH-mediated changes of OS elicitation (pectin methyl esterase activation and methanol release). The activities of fatty acid amino acid conjugates, well-known elicitors of antiherbivore defenses, and of 2-hydroxyoctadecatrienoic acid, a newly discovered signal in OS, were determined. Approximately 400 analytes were detected after deconvolution and alignment of GCxGC data; 35 volatiles were significantly regulated upon W+OS. Two-thirds of these were specifically regulated by OS, being either amplified (most terpenoids and certain hexenylesters) or strongly repressed (many short-chain alcohols and some aromatic and hexenylester derivatives). Fatty acid amino acid conjugates played a central role in this pattern of regulation, since they induced the emission of half of OS-elicited volatiles and inhibited the production of almost all OS-repressed volatiles; 2-hydroxyoctadecatrienoic acid influenced emission of trans-?-bergamotene, while other unknown OS constituents amplified hexenylester production. We conclude that the complex bouquet of herbivory-elicited volatiles results from the complex modulations of the wound response by diverse cues found in OS. This work also underscores the value of ultra-high-resolution GCxGC-ToF analysis combined with the nontargeted mining of the resulting data.

Gaquerel, Emmanuel; Weinhold, Alexander; Baldwin, Ian T.

2009-01-01

386

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

387

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

388

Solar Doppler shifts - Sources of continuous spectra  

NASA Technical Reports Server (NTRS)

Oscillation observations can be used to study nonoscillatory solar phenomena that exhibit Doppler shifts. The paper discusses several effects of these phenomena and their associated temporal and spatial power spectra: (1) they limit the signal-to-noise ratio and sometimes detectability of oscillation modes; (2) there is the potential for better understanding and/or detection of solar phenomena; (3) large-scale convection may spatially modulate oscillation modes, leading to a continuous background spectrum; and (4) in regions of the spectrum where the resolution to separate modes is lacking one can determine upper limits for the integrated effects of modes.

Duvall, T. L., Jr.; Harvey, J. W.

1986-01-01

389

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

390

Covariance analysis of gamma ray spectra.  

PubMed

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. PMID:23387645

Trainham, R; Tinsley, J

2013-01-01

391

Covariance analysis of gamma ray spectra  

NASA Astrophysics Data System (ADS)

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

392

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

393

On The Spectra of Operator Completion Problems  

Microsoft Academic Search

\\u000a For an 2 × 2 operator matrix\\u000a $\\u000aM_X \\\\left( {{*{20}c}\\u000aA & C \\\\\\\\\\u000aX & B \\\\\\\\\\u000a } \\\\right)\\u000a$\\u000aM_X \\\\left( {\\\\begin{array}{*{20}c}\\u000aA & C \\\\\\\\\\u000aX & B \\\\\\\\\\u000a\\\\end{array} } \\\\right)\\u000a\\u000a on the Hilbert space H ? K, if A, B and C are given, we study the intersection and the union of the spectra

Hong-Ke Du; Caixing Gu

394

Engineering upconversion emission spectra using plasmonic nanocavities.  

PubMed

We show that the upconversion emission spectra of Tm3+ and Yb3+ codoped ?-NaYF4-NaYF4 core-shell nanoparticles can be judiciously modified by means of plasmonic nanocavities. Our analysis indicates that more than a 30-fold increase in conversion efficiency to the UV spectral band can be expected by engineering the NIR absorption and the local density of states. The effect of the nanocavity on the resulting radiation patterns is discussed. Our results are exemplified in cylindrical cavity geometries. PMID:24978717

Lantigua, Christopher; He, Sha; Bouzan, Milad Akhlaghi; Hayenga, William; Johnson, Noah J J; Almutairi, Adah; Khajavikhan, Mercedeh

2014-07-01

395

Uncertainty Quantification on Prompt Fission Neutrons Spectra  

SciTech Connect

Uncertainties in the evaluated prompt fission neutrons spectra present in ENDF/B-VII.0 are assessed in the framework of the Los Alamos model. The methodology used to quantify the uncertainties on an evaluated spectrum is introduced. We also briefly review the Los Alamos model and single out the parameters that have the largest influence on the calculated results. Using a Kalman filter, experimental data and uncertainties are introduced to constrain model parameters, and construct an evaluated covariance matrix for the prompt neutrons spectrum. Preliminary results are shown in the case of neutron-induced fission of {sup 235}U from thermal up to 15 MeV incident energies.

Talou, P. [T-16, Nuclear Physics Group, Los Alamos National Laboratory, NM 87545 (United States)], E-mail: talou@lanl.gov; Madland, D.G.; Kawano, T. [T-16, Nuclear Physics Group, Los Alamos National Laboratory, NM 87545 (United States)

2008-12-15

396

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

397

Atomic Spectra in a Helium Bubble  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) is applied to atomic spectra under perturbations of superfluid liquid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and D2 absorption lines are quite well reproduced by theory, suggesting that the DFT may be useful for describing spectral perturbations in more complex environments.

Nakatsukasa, Takashi; Yabana, Kazuhiro; Bertsch, George F.

2002-09-01

398

Magnetic Resonance Spectra and Statistical Geometry  

PubMed Central

Methods of statistical geometry are introduced which allow one to estimate, on the basis of computable criteria, the conditions under which maximally informative data may be collected. We note the important role of constraints which introduce curvature into parameter space and discuss the appropriate mathematical tools for treating curvature effects. Channel capacity, a term from communication theory, is suggested as a useful figure of merit for estimating the information content of spectra in the presence of noise. The tools introduced here are applied to the case of a model nitroxide system as a concrete example, but we stress that the methods described here are of general utility.

Mainali, Laxman; Sahu, Indra Dev; Schneider, David J.

2010-01-01

399

Influence of intermediate states on photoelectron spectra  

NASA Astrophysics Data System (ADS)

We investigate the information contained in the photoelectron spectra (PES) of electrons emitted from an atom, molecule, or cluster under the influence of a laser pulse. Basic patterns are evaluated in a simple potential well model. The results are corroborated by realistic applications to the cluster Na9+ calculated within a time-dependent density functional formalism. The final PES are composed from an interplay between features of the laser pulse and spectral properties of the emitting system. We discuss the mutual influences and the possibilities for disentangling the various effects.

Pohl, A.; Reinhard, P.-G.; Suraud, E.

2001-12-01

400

High-energy spectra of atmospheric neutrinos  

NASA Astrophysics Data System (ADS)

A calculation of the atmospheric high-energy muon neutrino spectra and zenith-angle distributions is performed for two primary spectrum parameterizations (by Gaisser and Honda and by Zatsepin and Sokolskaya) with the use of QGSJET-II-03 and SIBYLL 2.1 hadronic models. A comparison of the zenith angle-averaged muon neutrino spectrum with the data of Frejus, AMANDA-II, and IceCube40 experiments makes it clear that, even at energies above 100 TeV, the prompt neutrino contribution is not apparent because of the considerable uncertainties of the experimental data in the high-energy region.

Petrova, O. N.; Sinegovskaya, T. S.; Sinegovsky, S. I.

2012-12-01

401

Fluorescence spectra shape based dynamic thermometry  

NASA Astrophysics Data System (ADS)

An entirely optical, dynamic thermometry technique based on the temperature dependence of a fluorescence spectrum is presented. Different from conventional intensity-based fluorescence thermometry, in this work, neural network recognition is employed to extract the sample temperature from the magnitude and shape of recorded fluorescence spectra. As a demonstration to determine the depth profile of dynamical temperature variations and of the thermal and optical properties of semitransparent samples, in-depth photothermally induced periodical temperature oscillations of a rhodamine B and copper chloride dyed glycerol sample were measured with an accuracy of 4.2 mK·Hz-1/2 and fitted well by a 1D thermal diffusion model.

Liu, Liwang; Creten, Sebastiaan; Firdaus, Yuliar; Agustin Flores Cuautle, Jose Jesus; Kouyaté, Mansour; Van der Auweraer, Mark; Glorieux, Christ

2014-01-01

402

Vibrational spectra of cesium tellurate phosphate  

NASA Astrophysics Data System (ADS)

The infrared and Raman spectra of cesium tellurate phosphate (Te(OH) 6·Cs 2HPO 4), a compound containing two anions, are recorded and analysed. It has been found that the two anions Te(OH) 6 and HPO 4 coexist in the crystal almost independently without affecting each other. The hydrogen atom is loosely bonded to the oxygen atom of the phosphate ion and hence the phosphate ion exists as distorted PO 3-4 tetrahedron rather than HPO 2-4 ion.

Viswanathan, K.; Nayar, V. U.; Aruldhas, G.

1986-11-01

403

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

404

Ultraviolet Spectra of Normal Spiral Galaxies  

NASA Technical Reports Server (NTRS)

The data related to this grant on the Ultraviolet Spectra of Normal Spiral Galaxies have been entirely reduced and analyzed. It is incorporated into templates of Spiral galaxies used in the calculation of K corrections towards the understanding of high redshift galaxies. The main paper was published in the Astrophysical Journal, August 1996, Volume 467, page 38. The data was also used in another publication, The Spectral Energy Distribution of Normal Starburst and Active Galaxies, June 1997, preprint series No. 1158. Copies of both have been attached.

Kinney, Anne

1997-01-01

405

Applying Zeeman Doppler imaging to solar spectra  

NASA Astrophysics Data System (ADS)

A new generation of spectro-polarimeters with high throughput (e.g. CFHT/ESPADONS and LBT/PEPSI) is becoming available. This opportunity can be exploited using Zeeman Doppler imaging (ZDI), a technique that inverts time-series of Stokes V spectra to map stellar surface magnetic fields (Semel 1989). ZDI is assisted by ``Least squares deconvolution'' (LSD), which sums up the signal from 1000's of photospheric lines to produce a mean deconvolved profile with higher S:N (Donati & Collier Cameron 1997).

Hussain, G. A. J.; Saar, S. H.; Collier Cameron, A.

2004-03-01

406

Second-Order Raman Spectra of Thorium Dioxide  

Microsoft Academic Search

The second-order Raman spectra of the thorium dioxide crystal have been investigated. The results are interpreted in terms of the phonon energies near the Brillouin zone boundaries and the zone center, which have been calculated by using Born-von Karman force model. A nearly complete interpretation of the spectra is given. The observed polarization of Raman spectra is in good agreement

Mareo Ishigame; Masahisa Kojima

1976-01-01

407

Microcomputer program for analysis of positron annihilation lifetime spectra  

Microsoft Academic Search

A user friendly program (LT) for analysis of the lifetime spectra has been designed for personal computers. The program is compared with other existing programs such as POSITRONFIT, CONTIN and MELT. LT enables one to analyse both discrete and continuous spectra as well as mixed- partially linear and partially continuous spectra. The searched parameters are found by using a fully

J. Kansy

1996-01-01

408

Multivariate statistical analysis of particle x-ray spectra  

Microsoft Academic Search

Multivariate statistical analysis (MSA) is a powerful tool for the analysis of series of spectra. This paper explores an application of MSA to a series of energy dispersive X-ray (EDX) spectra acquired in the scanning electron microscope (SEM) from a series of particles. The raw data were series of spectra previously acquired to test analytical procedures for trace element detection.

I. M. Anderson; J. A. Small

1998-01-01

409

Electron Impact Spectra of Ethane and Other Saturated Hydrocarbons.  

National Technical Information Service (NTIS)

Electron impact spectra for ethane are reported at accelerating voltages from 50 to 180 V and scattering angles to 9 deg. Spectra of methane at 0 deg and 6 deg and for propane and butane at 0 deg are reported at an accelerating voltage of 50. Spectra of p...

E. N. Lassettre A. Skerbele M. A. Dillon

1968-01-01

410

Basics of multiphoton effects in coherent radiation spectra  

NASA Astrophysics Data System (ADS)

Differences between classically calculated radiation spectra of coherent radiation sources and their calorimetrically measured counterparts are discussed in a nutshell. Properties of photon multiplicity spectra are highlighted. The high-intensity limit is analyzed. A simple model for quick estimates of multiphoton effects in coherent radiation spectra is given.

Bondarenco, M. V.

2014-05-01

411

Normalization of the Speech Modulation Spectra for Robust Speech Recognition  

Microsoft Academic Search

Abstract—In this paper, we study a novel technique that normalizes the modulation spectra of speech signals for robust speech recognition. The modulation spectra of a speech signal are the power spectral density (PSD) functions of the feature trajectories generated from the signal, hence they describe the temporal structure of the features. The modulation spectra are distorted when,the speech signal is

Xiong Xiao; Chng Eng Siong; Haizhou Li

2008-01-01

412

INFRARED SPECTRA OF AMMONIA-WATER ICES  

SciTech Connect

We conducted a systematic study of the near-IR and mid-IR spectra of ammonia-water ices at various NH{sub 3}/H{sub 2}O ratios. The differences between the spectra of amorphous and crystalline ammonia-water ices were also investigated. The 2.0 {mu}m ammonia band central wavelength is a function of the ammonia/water ratio. It shifts from 2.006 {+-} 0.003 {mu}m (4985 {+-} 5 cm{sup -1}) to 1.993 {+-} 0.003 {mu}m (5018 {+-} 5 cm{sup -1}) as the percentage of ammonia decreases from 100% to 1%. The 2.2 {mu}m ammonia band center shifts from 2.229 {+-} 0.003 {mu}m (4486 {+-} 5 cm{sup -1}) to 2.208 {+-} 0.003 {mu}m (4528 {+-} 5 cm{sup -1}) over the same range. Temperature-dependent shifts of those bands are below the uncertainty of the measurement, and therefore are not detectable. These results are important for comparison with astronomical observations as well as for estimating the concentration of ammonia in outer solar system ices.

Zheng Weijun; Jewitt, David [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Kaiser, Ralf I. [Department of Chemistry, University of Hawaii, Honolulu, HI 96822 (United States)], E-mail: jewitt@ifa.hawaii.edu, E-mail: ralfk@hawaii.edu, E-mail: zhengwj@iccas.ac.cn

2009-03-15

413

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

414

Glueball spectra of SQCD-like theories  

NASA Astrophysics Data System (ADS)

We study the spectrum of scalar glueballs in SQCD-like theories whose gravity description is in terms of N c D5 color branes wrapped on an S 2 inside a CY3-fold, and N f backreacting D5 flavor branes wrapped on a non-compact two-cycle inside the same CY3-fold. We show that there exists a consistent truncation of the ten-dimensional Type IIB supergravity system to a five-dimensional non-linear sigma model consisting of four scalars coupled to gravity. Studying fluctuations of the scalars as well as the metric around particular backgrounds allows us to compute their spectra. A few different backgrounds share the same qualitative features, namely that the mass of the lightest scalar glueball increases as the number of flavors is increased, until one reaches the point N f = 2 N c after which the opposite behaviour is obtained. We show that the five-dimensional non-linear sigma model obeys Seiberg duality, and demonstrate this explicitly for the spectra of a class of backgrounds that are Seiberg dual to themselves.

Elander, Daniel

2010-03-01

415

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

416

Fully automated microcomputer calculation of vibrational spectra  

NASA Astrophysics Data System (ADS)

A fully automated method for computing frequencies and atomic displacements of normal modes, giving synthetic infrared and Raman spectra, has been developed for use on small computers. No expertise in group theory or the mathematics of normal-mode calculation are required to use the computer program. The method takes full account of symmetry and is applicable to any crystal or molecule. Force constants can be specified in terms of any two-atom “bonds” or three-atom angles. The essential steps in the computer program are: (1) Locate all atoms in the unit cell or molecule and compute displacement vectors for each internal coordinate; (2) Convert the basis of the force constants from bonds and angles to cartesian displacements; (3) Construct the full-matrix irreducible representations of the point or factor group in question, using appropriate symmetry matrices and polynomial basis functions; (4) Derive the symmetry coordinates in terms of cartesian displacements using the projection/transfer-operator technique; (5) construct secular equations for each species with Wilson's f g method; (6) solve for frequencies and atomic motions; and (7) use simple models of infrared and Raman intensities to calculate spectra.

Dowty, Eric

1987-01-01

417

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

418

Infrared Spectra of Ammonia-Water Ices  

NASA Astrophysics Data System (ADS)

We conducted a systematic study of the near-IR and mid-IR spectra of ammonia-water ices at various NH3/H2O ratios. The differences between the spectra of amorphous and crystalline ammonia-water ices were also investigated. The 2.0 ?m ammonia band central wavelength is a function of the ammonia/water ratio. It shifts from 2.006 ± 0.003 ?m (4985 ± 5 cm-1) to 1.993 ± 0.003 ?m (5018 ± 5 cm-1) as the percentage of ammonia decreases from 100% to 1%. The 2.2 ?m ammonia band center shifts from 2.229 ± 0.003 ?m (4486 ± 5 cm-1) to 2.208 ± 0.003 ?m (4528 ± 5 cm-1) over the same range. Temperature-dependent shifts of those bands are below the uncertainty of the measurement, and therefore are not detectable. These results are important for comparison with astronomical observations as well as for estimating the concentration of ammonia in outer solar system ices.

Zheng, Weijun; Jewitt, David; Kaiser, Ralf I.

2009-03-01

419

Protein Identification Using Top-Down Spectra*  

PubMed Central

In the last two years, because of advances in protein separation and mass spectrometry, top-down mass spectrometry moved from analyzing single proteins to analyzing complex samples and identifying hundreds and even thousands of proteins. However, computational tools for database search of top-down spectra against protein databases are still in their infancy. We describe MS-Align+, a fast algorithm for top-down protein identification based on spectral alignment that enables searches for unexpected post-translational modifications. We also propose a method for evaluating statistical significance of top-down protein identifications and further benchmark various software tools on two top-down data sets from Saccharomyces cerevisiae and Salmonella typhimurium. We demonstrate that MS-Align+ significantly increases the number of identified spectra as compared with MASCOT and OMSSA on both data sets. Although MS-Align+ and ProSightPC have similar performance on the Salmonella typhimurium data set, MS-Align+ outperforms ProSightPC on the (more complex) Saccharomyces cerevisiae data set.

Liu, Xiaowen; Sirotkin, Yakov; Shen, Yufeng; Anderson, Gordon; Tsai, Yihsuan S.; Ting, Ying S.; Goodlett, David R.; Smith, Richard D.; Bafna, Vineet; Pevzner, Pavel A.

2012-01-01

420

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

421

QSO'S with IPC X-Ray Spectra  

NASA Astrophysics Data System (ADS)

We propose to obtain both short and long wavelength ultraviolet spectrophotometry of 5 bright quasars that have well-determined x-ray spectra. Together with the quasars in our current IUE program and seven from the IUE data archive these objects will form the basis of a reasonably sized sample. For this sample we have in hand (or are in the process of obtaining) ground-based optical and infrared spectra and photometry and IRAS co-add data. Together these data define the quasars' continuum from ~100 microns to ~7 keV, (5 decades of frequency). The IUE data have particular importance for defining the optical-UV 'big bump' (accretion disk?) and the "300OA" 'small bump' due to Balmer continuum and FeII emission. The definition of these features is essential to the testing of the accretion disk hypothesis and particular disk models; the determination of the EUV ionizing spectrum, and the testing of the optically thick photoionization models.

Elvis, Martin S.

422

Biological NMR FIDs and spectra normalization  

NASA Astrophysics Data System (ADS)

There is increasing use of spectroscopic techniques, such as high-resolution NMR spectroscopy, to examine variations in cell metabolism and / or structure in response to numerous physical, chemical, and biological agents. In these types of studies, in order to obtain relative quantitative information, a comparison between signal intensities of control samples and treated or exposed ones is often conducted. The methods thus far developed for this purpose are not directly related to the overall intrinsic properties of the samples, but rather to the addition of external substances of known concentrations or to indirect measurement of internal substances. Another possibility is to estimate, by an opportune algorithm, a normalization constant which takes into consideration all cell metabolites present in the sample. Recently, a new normalization algorithm, based on Principal Component Analysis (PCA), was presented. PCA is a well-known statistical technique for analysis of large, multivariate datasets, which extracts the basic features of the data. The PRICONA (PRincipal COmponent Normalization Algorithm) algorithm use PCA in a new totally different manner: PCA is, in fact, used to normalize spectra in order to obtain quantitative information about the treatment effects. In this paper, a comparison of results obtained in the time domain, that is on NMR FIDs (Free Induction Decay) and in the frequency domain, on NMR spectra, is conducted. The comparison is useful because in NMR spectroscopy analysis in the different domain can have different advantages. The algorithm was tested by Monte Carlo simulations of NMR FIDs.

Romano, R.; Canonico, R.; Acernese, F.; Giordano, G.; Barone, F.

2014-03-01

423

Simulation of x-ray absorption near-edge spectra and x-ray fluorescence spectra of optically excited molecules  

SciTech Connect

The x-ray absorption near-edge spectra (XANES) and fluorescence spectra of molecules in the ground state and optically excited states are computed using time-dependent density functional theory and time-dependent Hartree-Fock theory. The calculated XANES spectra of optically excited methanol, benzonitrile, hydrogen sulphide, and titanium tetrachloride and the fluorescence spectra of optically excited methanol can be used to simulate ultrafast optical pump/x-ray probe experiments.

Pandey, R.K.; Mukamel, Shaul [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States)

2006-03-07

424

Comparison between MAFAGS-OS spectra and Kurucz-ODF spectra  

Microsoft Academic Search

Grids of theoretical stellar spectra are fundamental for estimating basic stellar parameters from photometric and spectroscopic data observed in large sky surveys such as SDSS, LAMOST, Gaia, etc. Do the different atmosphere models influence the parameters estimation? We compute the Lick indexes and uvby color indexes using the MAFAGS-OS grid of model atmospheres and fluxes provided by F. Grupp (personal

Jiannan Zhang; Ali Luo; Yihan Song; Fang Zuo

2011-01-01

425

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

426

Quantitative in vivo absorption spectra of phytoplankton: Detrital absorption and comparison with fluorescence excitation spectra  

Microsoft Academic Search

Spectra1 absorption of phytoplankton from cultures and natural samples was measured on filters with various optical setups including collimated and diffuse irradiation and measurements ofwetted filters within an integrating sphere. In suspensions within an integrating sphere, specific absorption coefficients for laboratory cultures varied by a factor of only two. Measurements on filters yielded values dependent on filter load. Specific absorption

HELMUT MASKE; HAUKE HAARDT

1987-01-01

427

Optical Spectra of Yb(3+) in Crystals with Scheelite Structure. I. Explanation of the Spectra.  

National Technical Information Service (NTIS)

The optical and Zeeman spectra are reported for Yb(3+) in nine single crystals of the Scheelite family at temperatures varying between 1.9 and 300 K and impurity ion concentration varying between 0.05 and 4 percent. The scheelite crystals examined were Ca...

E. A. Brown

1980-01-01

428

Lattice vibrations and ion transport spectra in beta-alumina. II. Microwave spectra  

Microsoft Academic Search

The ionic conductor beta-alumina has been studied in the microwave frequency range 0.2 to 85 GHz. The conductivity and dielectric constant have been measured in this range for Na, Ag, and K ions substituted in the diffusing planes. The spectra show a region below 1 GHz where the conductivity is thermally activated with values the same as the dc values.

A. S. Barker Jr.; J. A. Ditzenberger; J. P. Remeika

1976-01-01

429

WebSpectra: Problems in NMR and IR Spectroscopy  

NSDL National Science Digital Library

From the University of California at Los Angeles's Chemistry Department, WebSpectra provides chemistry students with a searchable library of Nuclear Magnetic Resonance (NMR) and Infrared (IR) spectroscopy problems. According to the makers of this innovative site, "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." A set of instructional documents are entitled Solving Spectral Problems, Overview of NMR Spectroscopy, Notes on NMR Solvents, Types of NMR Spectra, Introduction to IR Spectra, and a Table of IR Absorptions. A wide variety of compounds and their spectra are available for interpretation and have been organized in categories from Beginning to Advanced. Spectrum for each compound may be magnified 16X by clicking on peaks. This is an outstanding learning tool for students coming to grips with interpreting NMR and IR spectra.

430

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

431

MAS NMR and FTIR spectra of framework aluminosilicates  

NASA Astrophysics Data System (ADS)

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb 2+, Cd 2+, Ni 2+ and Cr 3+) into the zeolite structure. After decomposition of the spectra into component peaks differences caused by ion exchange were observed. Additionally, NMR spectra of kalsilite (framework aluminosilicate, not belonging to zeolite group) and other zeolites (chabazite, heulandite and analcime) were measured. 27Al MAS NMR spectra of all the samples studied were compared with the FTIR spectra measured in the middle infrared region. Based on the results obtained it has been proved that the interpretation of spectra obtained using these two different techniques can give some information concerning changes occurring in various framework aluminosilicate structures.

Mozgawa, W.; Fojud, Z.; Handke, M.; Jurga, S.

2002-09-01

432

Correcting Infrared Spectra for Atmospheric Transmission  

NASA Astrophysics Data System (ADS)

Astronomical spectra taken with ground-based telescopes in the near-IR spectral region are affected by strong absorptions due to molecules in the Earth's atmosphere, particularly CO2 and H2O. These features need to be removed in order to reveal the true spectrum of the object being observed. The traditional technique for doing this is to observe a standard star with a relatively featureless spectrum (a smooth spectrum standard) and divide the observed spectrum of the object by that of the standard. This technique has a number of practical difficulties but is also fundamentally flawed. Even with a perfectly smooth spectrum standard observed at an identical air mass to the object, this technique does not, in general, reproduce the spectrum of the object that would have been observed in the absence of the Earth's atmosphere. The problem arises because of the presence of high-resolution structure in the molecular absorption features, generally on a finer scale than the resolution of the observed spectrum. The transmission of the Earth's atmosphere for any spectral bin then depends on the unresolved spectral structure of the light being transmitted and cannot be represented by a unique value derived from the standard star, as the traditional technique assumes. We use high-resolution line-by-line radiative transfer models to quantify these effects for two cases: observations of a solar-type star, and observations of the planet Mars. For a solar-type star, application of the traditional technique causes errors of a few percent in the vicinity of strong atmospheric absorption features. The case of the planet Mars is an extreme case, since Mars has the same CO2 absorption features as the Earth's atmosphere. Our simulations show that applying the traditional astronomical technique to ground-based spectra of the planet Mars leads to systematic errors of up to ~50% in the vicinity of the strong CO2 absorption features. High-quality IR spectroscopy with ground-based telescopes requires an improved technique to handle the absorption in the Earth's atmosphere. We outline a possible approach based on the use of radiative transfer models for the Earth's atmosphere. We note that in general it is not possible to correct observed spectra for atmospheric absorption. However, a forward-modeling approach can be used in which a model spectrum for the object is generated, atmospheric transmission effects added, and the result compared with the observed spectrum. We present a demonstration of the ability of a model to accurately represent the Earth atmosphere transmission in the J band.

Bailey, Jeremy; Simpson, Andrew; Crisp, David

2007-02-01

433

Comparison between MAFAGS-OS spectra and Kurucz-ODF spectra  

NASA Astrophysics Data System (ADS)

Grids of theoretical stellar spectra are fundamental for estimating basic stellar parameters from photometric and spectroscopic data observed in large sky surveys such as SDSS, LAMOST, Gaia, etc. Do the different atmosphere models influence the parameters estimation? We compute the Lick indexes and uvby color indexes using the MAFAGS-OS grid of model atmospheres and fluxes provided by F. Grupp (personal comm.) and the Kurucz grids [1]. A spectrum comparison reveals the behavior of spectra from the MAFAGS and Kurucz grids. We find that using the (b-y) index, consistent effective temperatures can be determined from both the Kurucz and MAFAGS grids of theoretical spectra. The m1 index, together with color index, can be used to determine the metallicity of F- and G-type stars, but the measurements of the Kurucz and MAFAGS grids show systematic discrepancies for cool stars. The c1 indexes computed with both grids show small discrepancies for Teff < 6000 K, while for Teff > 6000 K, the c1 indexes agree well. The Lick indexes of the Kurucz grid and the MAFAGS grid tend to be in agreement for warm stars with temperatures above 5000 K, while for cool stars with temperatures ranging from 4000 K to 5000 K, the difference of Lick indexes for both models is apparently large. We also compare the MAFAGS spectrum and Kurucz spectrum of the same temperature, surface gravity, and metallicity using a correlation coefficient for the complete spectrum. For warm stars, the MAFAGS and Kurucz spectra are almost the same, while for cool stars below 5000 K, there are some discrepancies between the MAFAGS and Kurucz spectra that induce internal discrepancies in the parameters determination.

Zhang, Jiannan; Luo, Ali; Song, Yihan; Zuo, Fang

2011-12-01

434

Ablation spectra of the human cornea  

NASA Astrophysics Data System (ADS)

Ablation of human corneal tissue with 193 nm excimer laser energy generates fluorescence in the near ultraviolet and visible regions of the spectrum. The fluorescence spectra from five human corneas were collected during ablation in vitro. We find that the fluorescence spectrum changes continuously at the cornea is ablated from the epithelial surface towards the endothelium. We reduced the dimensionality of the large data set resulting from each cornea by a principal components analysis. The three most significant principal component eigenvectors suffice to describe the observed spectral evolution, and independent analysis of each tissue sample produces a similar set of eigenvectors. The evolution of the calculated eigenvector weighting factors during ablation then corresponds to the observed spectral evolution. In fact, this evolution is qualitatively consistent between corneas. We suggest that this spectral evolution offers promise as a real-time surgical feedback tool.

Cohen, David; Chuck, Roy S.; Bearman, Gregory H.; McDonnell, Peter J.; Grundfest, Warren S.

2001-07-01

435

3- to 13-micron spectra of Io  

NASA Technical Reports Server (NTRS)

The Broadband Array Spectrograph System with the NASA Infrared Telescope Facility was used to obtain 3- to 13-micron spectra of Io on June 14-16, 1991. The extinction correction and its error for each standard star (Alpha Boo, Alpha Lyr, and Mu UMa) were found individually by performing an unweighted linear fit of instrumental magnitude as a function of airmass. The model results indicate two significant trends: (1) modest differences between the two hemispheres at lower background temperatures and (2) a tendency to higher temperatures, smaller areas, and less power from the warm component at higher background temperatures with an increased contrast between the two hemispheres. The increased flux from 8 to 13 microns is due primarily to a greater area on the Loki (trailing) hemisphere for the warm component, although temperature also plays a role.

Noll, Keith S.; Hammel, H. B.; Young, Leslie; Joiner, Joanna; Hackwell, J.; Lynch, D. K.; Russell, R.

1993-01-01

436

Satellite spectra for helium-like titanium  

SciTech Connect

Wavelengths and atomic parameters for both dielectronic and inner-shell satellite lines of the type ls/sup 2/ nl - 1s2l' nl, with n = 2, 3, and 4, have been calculated for Ti XX. The atomic data were calculated in a multiconfiguration intermediate coupling scheme and are compared with previous results for n = 2. The intensities of the higher n satellites are derived from these data, and thus an estimate of the contribution of the unresolved dielectronic satellites to the resonance line is obtained. Direct excitation rates are also given for the resonance, intercombination and forbidden lines for He-like titanium. Cascades and the effect of resonances for these lines are not considered in this paper. These results are used to fit an experimental soft x-ray spectrum from the PDX (Poloidal Divertor Experiment) tokamak discharge. Good agreement is obtained between computed and observed spectra.

Bely-Dubac, F.; Faucher, P.; Steeman-Clark, L.; Dubau, J.; Cammy-Val, C.; Bitter, M.; Hill, K.W.; von Goeler, S.

1982-06-01

437

Electron spectra from decay of fission products  

SciTech Connect

Electron spectra following decay of individual fission products (72 less than or equal to A less than or equal to 162) are obtained from the nuclear data given in the compilation using a listed and documented computer subroutine. Data are given for more than 500 radionuclides created during or after fission. The data include transition energies, absolute intensities, and shape parameters when known. An average beta-ray energy is given for fission products lacking experimental information on transition energies and intensities. For fission products having partial or incomplete decay information, the available data are utilized to provide best estimates of otherwise unknown decay schemes. This compilation is completely referenced and includes data available in the reviewed literature up to January 1982.

Dickens, J K

1982-09-01

438

Raman spectra of solid isotopic hydrogen mixtures  

NASA Astrophysics Data System (ADS)

Rotational and vibrational Raman spectra are investigated for mixtures of hydrogen isotopes in the solid phase. The S0(0) rotational Raman transitions are asymmetrically broadened in energy for each isotope in the mixture compared to their respective pure component transitions. The isotopic energy shift of S0(0) breaks the lattice symmetry and limits the roton hopping responsible for the well defined S0(0) triplet found in the pure component. The S0(0) line shapes of tritiated and nontritiated mixtures are nearly identical, and shows there is little effect from radiation damage. The vibrational Q1(J) lines are shifted to higher energy, and the Q1(1)/Q1(0) intensity ratio is decreased in the mixtures relative to the pure component. Both effects are due to a localization of the vibrons in mixtures.

Kozioziemski, B. J.; Collins, G. W.

2003-05-01

439

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

440

Theoretical infrared spectra of large carbon clusters  

NASA Astrophysics Data System (ADS)

Harmonic force constant calculations at the MNDO SCF level are reported for 22 polyhedral carbon clusters C n (20 ? n ? 240) and for the reference molecules benzene, coronene, and corannulene. New or revised assignments are suggested for coronene and corannulene. Based on the results for the reference molecules and for C 60, MNDO is expected to overestimate the vibrational frequencies of the unknown clusters by 10% and to yield reasonable intensity patterns. Calculated infrared spectra are shown and discussed for 12 carbon clusters, with particular emphasis on those which might be observable spectroscopically. The zero-point vibrational energies and the entropy contributions to the free enthalpy are only of minor importance for the thermodynamic stabilities of different clusters.

Bakowies, Dirk; Thiel, Walter

1991-04-01

441

A review of type Ia supernova spectra  

NASA Astrophysics Data System (ADS)

SN 2011fe was the nearest and best-observed type Ia supernova in a generation, and brought previous incomplete datasets into sharp contrast with the detailed new data. In retrospect, documenting spectroscopic behaviors of type Ia supernovae has been more often limited by sparse and incomplete temporal sampling than by consequences of signal-to-noise ratios, telluric features, or small sample sizes. As a result, type Ia supernovae have been primarily studied insofar as parameters discretized by relative epochs and incomplete temporal snapshots near maximum light. Here we discuss a necessary next step toward consistently modeling and directly measuring spectroscopic observables of type Ia supernova spectra. In addition, we analyze current spectroscopic data in the parameter space defined by empirical metrics, which will be relevant even after progenitors are observed and detailed models are refined.

Parrent, J.; Friesen, B.; Parthasarathy, M.

2014-05-01

442

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

443

Electroabsorption and electrophotoluminescence spectra of some subphthalocyanines  

NASA Astrophysics Data System (ADS)

Electric field effects on the electronically excited states have been investigated for two subphthalocyanines, F-SubPc and T-SubPc, which have the electron-withdrawing and electron-donating substituents, respectively. In contrast with T-SubPc, the directions of the electric dipole moment in the excited states S1 and S2 of F-SubPc are found to be very different from that in the ground state S0. The S1 and S2 states of T-SubPc show a prominent charge-transfer character, suggesting that T-SubPc is a suitable candidate as the dye in photovoltaic cells. Electrophotoluminescence spectra suggest that the intersystem crossing from S1 to T1 is enhanced by electric fields.

Awasthi, Kamlesh; Nakamura, Kosuke; Kono, Hirohiko; Kobayashi, Nagao; Ohta, Nobuhiro

444

Longslit Spectra of the Galaxy NGC 1569  

NASA Technical Reports Server (NTRS)

Longslit spectra of the starburst galaxy NGC 1569 are displayed. This ground-based data was acquired at the 90-inch telescope of the Steward Observatory (Kitt Peak, Arizona) in September 1998. Results for the red region of the spectrum are presented. The variation of ionization and gas density as a function of position in the galaxy are shown. The background stellar component of the galaxy is separated from the nebular emission spectrum. These ground-based results will be used with space-based data to be acquired by astronomers at South Carolina State University, the University of Maryland and Rice University as part of an approved Cycle 8 Hubble Space Telescope program.

Duenas, Ely

2000-01-01

445

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

446

First dynamic spectra of stellar microwave flares  

NASA Technical Reports Server (NTRS)

The VLA has been used in the spectral-line mode at 1.4 GHz to obtain the first dynamic spectra of stellar sources other than the sun. Two very intense, highly circularly polarized, microwave outbursts were observed on the dMe flare star UV Cet, in addition to a slowly varying, unpolarized component. One outburst was purely left circularly polarized and showed no variations as a function of frequency across the 41 MHz band, whereas the other was as much as 70 percent right-circularly polarized and showed distinct variations with frequency. Although the slowly varying emission is probably due to incoherent gyrosynchrotron emission, the two flaring events are the result of coherent mechanisms. The coherent emission is interpreted in terms of plasma radiation and the cyclotron maser instability.

Bastian, T. S.; Bookbinder, J. A.

1987-01-01

447

SN2011by: Rozhen photometry and spectra  

NASA Astrophysics Data System (ADS)

We present BVRI photometric data and several low-resolution spectra covering 4-month period after the explosion of SN2011by. The maximum light in I band occurs 2.25 d earlier than that in B band. The photometric data clearly exhibit presence of secondary peak in R and I filter. The measured declined rates in BVRI bands during the initial fading and late-time weakening and the absolute magnitude at maximum light of SN2011by are typical for SN Ia stars. Our data were well reproduced by the 92al model. The measured time gradient of the expansion velocity of the SiII 6355 feature and its EW are appropriate for ``Normal'' subtype of SNe Ia. We found two trends in August: gradually decreasing of the SiII 6355 feature and fast strengthening of 5720 Å.

Dimitrov, D.; Kjurkchieva, D.

448

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

449

Galactic cosmic ray composition and energy spectra  

NASA Technical Reports Server (NTRS)

Galactic cosmic ray nuclei represent a significant risk to long-duration spaceflight outside the magnetosphere. We review briefly existing measurements of the composition and energy spectra of heavy cosmic ray nuclei, pointing out which species and energy ranges are most critical to assessing cosmic ray risks for spaceflight. Key data sets are identified and a table of cosmic ray abundances is presented for elements from H to Ni (Z = 1 to 28). Because of the 22-year nature of the solar modulation cycle, data from the approaching 1998 solar minimum is especially important to reducing uncertainties in the cosmic ray radiation hazard. It is recommended that efforts to model this hazard take advantage of approaches that have been developed to model the astrophysical aspects of cosmic rays.

Mewaldt, R. A.

1994-01-01

450

Optical absorption spectra of dications of carotenoids  

SciTech Connect

Quantitative optical absorption spectra of the cation radicals and the dications of canthaxanthin (I), {beta}carotene (II), 7`-cyano-7`-ethoxycarbonyl-7`-apo-{beta}-carotene (III), and 7`,7`-dimethyl-7`-apo-{beta}-carotene (IV) in dichloromethane solution are reported. Exclusive formation of dications occurs when the carotenoids are oxidized with ferric chloride. Addition of neutral carotenoid to the dications results in equilibrium formation of cation radicals. Oxidation with iodine in dichloromethane affords only cation radicals; electrochemical oxidation under suitable conditions yields both dications and cation radicals. Values of the optical parameters depend on the nature of the oxidative medium. The oscillator strengths calculated for gas phase cation radicals and dications of I-IV using the INDO/S method show the same trend as the experimental values. 31 refs., 4 figs., 2 tabs.

Jeevarajan, J.A.; Wei, C.C.; Jeevarajan, A.S.; Kispert, L.D. [Univ. of Alabama, Tuscaloosa, AL (United States)] [Univ. of Alabama, Tuscaloosa, AL (United States)

1996-04-04