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1

Light absorption cell combining variable path and length pump  

DOEpatents

A device for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid therebetween and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data.

Prather, William S. (2419 Dickey Rd., Augusta, GA 30906)

1993-01-01

2

Integrating sphere effective optical path length calibration by gas absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A method of integrating sphere effective optical path length (EOPL) evaluation using tunable diode laser absorption spectroscopy for gas detection was demonstrated. Oxygen was used as a sample gas for an 8.38 cm diameter integrating sphere calibration; 393.7 ± 1.3 cm EOPL was obtained from the wavelength modulation spectroscopy with second harmonic calibration by measuring oxygen P11 line at 764 nm, which is in agreement with that of 393 cm by using direct absorption spectroscopy calibration. The EOPL calibration accuracy of this method can reach 0.33 %. It has been justified that the EOPL of an integrating sphere is independent of the incident light intensity.

Gao, Qiang; Zhang, Yungang; Yu, Jia; Zhang, Zhiguo; Wu, Shaohua; Guo, Wei

2014-03-01

3

Photon path length retrieval from GOSAT observations  

NASA Astrophysics Data System (ADS)

The influence of clouds on the atmospheric radiation budget is investigated, focussing on the photon path length distributions of the scattered sunlight. Apart from the reflection of incoming solar radiation at the cloud top, clouds can also introduce a large number of additional scattering events causing an enhancement of the photon paths. In certain cloud formations, these scattering events also result in a ``ping-pong`` behaviour between different cloud patches and cloud layers. It has been shown from ground based measurements that it is possible to retrieve photon path lengths by analysis of high resolution oxygen A-band spectra (O. Funk et al.). This study uses similar space based measurements of the oxygen A-band for the path length retrieval. The oxygen A-band spectra are retrieved from the Japanese Greenhouse Gases Observing Satellite (GOSAT) which was successfully launched in 2009. The high spectral resolution of the GOSAT TANSO-FTS instrument allows to almost completely resolve the individual absorption lines. The considered spectral range is particularly suitable for this study because it shows clear absorption structures of different strength. From the analysis of the spectral signatures, cloud properties and the underlying path length distributions can be derived. The retrieval is done by analysis and comparison of the extracted TANSO-FTS spectra with simulations from the Monte Carlo radiative transfer Model McArtim. The model permits modelling of altitude dependent oxygen absorption cross sections and three-dimensional cloud patterns. Case studies of clear and cloudy sky scenarios will be presented. Future studies will focus on more complicated cloud structures, especially considering three-dimensional geometries and heterogeneities.

Kremmling, Beke; Penning de Vries, Marloes; Deutschmann, Tim; Wagner, Thomas

2013-04-01

4

Variable path length spectrophotometric probe  

DOEpatents

A compact, variable pathlength, fiber optic probe for spectrophotometric measurements of fluids in situ. The probe comprises a probe body with a shaft having a polished end penetrating one side of the probe, a pair of optic fibers, parallel and coterminous, entering the probe opposite the reflecting shaft, and a collimating lens to direct light from one of the fibers to the reflecting surface of the shaft and to direct the reflected light to the second optic fiber. The probe body has an inlet and an outlet port to allow the liquid to enter the probe body and pass between the lens and the reflecting surface of the shaft. A linear stepper motor is connected to the shaft to cause the shaft to advance toward or away from the lens in increments so that absorption measurements can be made at each of the incremental steps. The shaft is sealed to the probe body by a bellows seal to allow freedom of movement of the shaft and yet avoid leakage from the interior of the probe.

O'Rourke, Patrick E. (157 Greenwood Dr., Martiney, GA 30907); McCarty, Jerry E. (104 Recreation Dr., Aiken, SC 29803); Haggard, Ricky A. (1144 Thornwood Drive, North Augusta, SC 29891)

1992-01-01

5

Diagnosis of multilayer clouds using photon path length distributions  

NASA Astrophysics Data System (ADS)

Photon path length distribution is sensitive to 3-D cloud structures. A detection method for multilayer clouds has been developed, by utilizing the information of photon path length distribution. The photon path length method estimates photon path length information from the low level, single-layer cloud structure that can be accurately observed by a millimeter-wave cloud radar (MMCR) combined with a micropulse lidar (MPL). As multiple scattering within the cloud layers and between layers would substantially enhance the photon path length, the multilayer clouds can be diagnosed by evaluating the estimated photon path information against observed photon path length information from a co-located rotating shadowband spectrometer (RSS). The measurements of MMCR-MPL and RSS at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site have been processed for the year 2000. Cases studies illustrate the consistency between MMCR-MPL detection and the photon path length method under most conditions. However, the photon path length method detected some multilayer clouds that were classified by the MMCR-MPL as single-layer clouds. From 1 year statistics at the ARM SGP site, about 27.7% of single-layer clouds detected by the MMCR-MPL with solar zenith angle less than 70° and optical depth greater than 10 could be multilayer clouds. It suggests that a substantial portion of single-layer clouds detected by the MMCR-MPL could also be influenced by some "missed" clouds or by the 3-D effects of clouds.

Li, Siwei; Min, Qilong

2010-10-01

6

Absorption Lengths in the Holographic Plasma  

E-print Network

We consider the effect of a periodic perturbation with frequency $\\omega$ on the holographic N=4 plasma represented by the planar AdS black hole. The response of the system is given by exponentially decaying waves. The corresponding complex wave numbers can be found by solving wave equations in the AdS black hole background with infalling boundary conditions on the horizon in an analogous way as in the calculation of quasinormal modes. The complex momentum eigenvalues have an interpretation as poles of the retarded Green's functions, where the inverse of the imaginary part gives an absorption length $\\lambda$. At zero frequency we obtain the screening length for a static field. These are directly related to the glueball masses in the dimensionally reduced theory. We also point out that the longest screening length corresponds to an operator with non-vanishing R-charge and thus does not have an interpretation as a QCD3 glueball.

Amado, Irene; Landsteiner, Karl; Montero, Sergio

2007-01-01

7

Absorption Lengths in the Holographic Plasma  

E-print Network

We consider the effect of a periodic perturbation with frequency $\\omega$ on the holographic N=4 plasma represented by the planar AdS black hole. The response of the system is given by exponentially decaying waves. The corresponding complex wave numbers can be found by solving wave equations in the AdS black hole background with infalling boundary conditions on the horizon in an analogous way as in the calculation of quasinormal modes. The complex momentum eigenvalues have an interpretation as poles of the retarded Green's functions, where the inverse of the imaginary part gives an absorption length $\\lambda$. At zero frequency we obtain the screening length for a static field. These are directly related to the glueball masses in the dimensionally reduced theory. We also point out that the longest screening length corresponds to an operator with non-vanishing R-charge and thus does not have an interpretation as a QCD3 glueball.

Irene Amado; Carlos Hoyos; Karl Landsteiner; Sergio Montero

2007-07-11

8

Neutron Path Length Correction of a 3He Spin Filter  

NASA Astrophysics Data System (ADS)

3He neutron spin filters (NSF) have been widely used for polarized neutron instrumentation for worldwide neutron facilities. Here we report characterization of the two-dimensional neutron path variation of a 3He NSF when a large divergent, scattered neutron beam passes through the end windows of a cylindrical 3He cell. Path length variations of the transmission of the unpolarized neutrons through a 3He NSF and neutron polarization produced from a 3He NSF are characterized. We present a ray-tracing model to explain the path length variation and corresponding neutron transmission and neutron polarization variations, and compare the measured variations to those calculated from the model. Although the path length effect is not large, it should be corrected in the polarization efficiency correction software when a 3He NSF is used for SANS polarization analysis. The path length variation effect can be adopted to other types of neutron scattering spectrometers when using 3He NSFs.

Chen, W. C.; Erwin, R.; Watson, S. M.

9

On the Minimization of Average Path Lengths for Heterogeneous MDDs  

Microsoft Academic Search

In this paper, we propose an exact and a heuristic min- imization algorithms for the average path length (APL) of heterogeneous multi-valued decision diagrams (MDDs). In a heterogeneous MDD, each variable can take on the dif- ferent number of values. To represent a binary logic func- tion using a heterogeneous MDD, we partition the binary variables into groups, and treat

Shinobu Nagayama; Tsutomu Sasao

2004-01-01

10

Limited-path-length entanglement percolation in quantum complex networks  

SciTech Connect

We study entanglement distribution in quantum complex networks where nodes are connected by bipartite entangled states. These networks are characterized by a complex structure, which dramatically affects how information is transmitted through them. For pure quantum state links, quantum networks exhibit a remarkable feature absent in classical networks: it is possible to effectively rewire the network by performing local operations on the nodes. We propose a family of such quantum operations that decrease the entanglement percolation threshold of the network and increase the size of the giant connected component. We provide analytic results for complex networks with an arbitrary (uncorrelated) degree distribution. These results are in good agreement with numerical simulations, which also show enhancement in correlated and real-world networks. The proposed quantum preprocessing strategies are not robust in the presence of noise. However, even when the links consist of (noisy) mixed-state links, one can send quantum information through a connecting path with a fidelity that decreases with the path length. In this noisy scenario, complex networks offer a clear advantage over regular lattices, namely, the fact that two arbitrary nodes can be connected through a relatively small number of steps, known as the small-world effect. We calculate the probability that two arbitrary nodes in the network can successfully communicate with a fidelity above a given threshold. This amounts to working out the classical problem of percolation with a limited path length. We find that this probability can be significant even for paths limited to few connections and that the results for standard (unlimited) percolation are soon recovered if the path length exceeds by a finite amount the average path length, which in complex networks generally scales logarithmically with the size of the network.

Cuquet, Marti; Calsamiglia, John [Grup de Fisica Teorica: Informacio i Fenomens Quantics, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona (Spain)

2011-03-15

11

Path-length distributions of photons diffusely reflected from a semi-infinite atmosphere.  

NASA Technical Reports Server (NTRS)

Knowledge of the probability distribution of photon path lengths for diffuse reflection in the continuum from a planetary atmosphere greatly simplifies computation of the shape and strength of absorption lines formed under conditions of multiple scattering. Graphs of this probability distribution are presented for diffuse reflection from a semiinfinite conservative atmosphere for both isotropic and forward-directed scattering, and for several angles of incidence and reflection. Graphs showing distributions for the case of absorption in the continuum are also discussed. The distributions are obtained from an analytic expression for the path-length distribution for nth-order scattering and a tabulation of nth-order intensities. It is found that te shape of the probability distribution depends markedly on the degree of forward scattering due to the phase function. The results are compared with those obtained by a Monte Carlo computation of the sort which might be used if tabulated nth-order intensities were not available.

Appleby, J. F.; Irvine, W. M.

1973-01-01

12

Coherent perfect absorption of path entangled single photons.  

PubMed

We examine the question of coherent perfect absorption (CPA) of single photons, and more generally, of the quantum fields by a macroscopic medium. We show the CPA of path entangled single photons in a Fabry-Perot interferometer containing an absorptive medium. The frequency of perfect absorption can be controlled by changing the interferometer parameters like the reflectivity and the complex dielectric constant of the material. We exhibit similar results for path entangled photons in micro-ring resonators. For entangled fields like the ones produced by a down converter the CPA aspect is evident in phase sensitive detection schemes such as in measurements of the squeezing spectrum. PMID:25321294

Huang, Sumei; Agarwal, G S

2014-08-25

13

Quantification of optical Doppler broadening and optical path lengths of multiply scattered light by phase modulated low coherence interferometry  

NASA Astrophysics Data System (ADS)

We show experimental validation of a novel technique to measure optical path length distributions and path length resolved Doppler broadening in turbid media for different reduced scattering coefficients and anisotropies. The technique involves a phase modulated low coherence Mach-Zehnder interferometer, with separate fibers for illumination and detection. Water suspensions of Polystyrene microspheres with high scattering and low absorption levels are used as calibrated scattering phantoms. The path length dependent diffusion broadening or Doppler broadening of scattered light is shown to agree with Diffusive Wave Spectroscopy within 5%. The optical path lengths are determined experimentally from the zero order moment of the phase modulation peak around the modulation frequency in the power spectrum and the results are validated with Monte Carlo simulations.

Varghese, B.; Rajan, V.; van Leeuwen, T. G.; Steenbergen, W.

2007-07-01

14

Photon path length distributions for cloudy atmospheres from GOSAT satellite measurements  

NASA Astrophysics Data System (ADS)

The presence of clouds in the atmosphere has significant influence on the photon paths of the scattered sunlight. Besides reflections of radiation at the cloud top, additional scattering events inside the cloud may occur and thus lengthening or shortening of the photon path in the atmosphere. Clouds consisting of multiple layers or patches may lead to a "ping pong" behaviour of the photons due to reflections at the individual surfaces. The objective of our study is the retrieval of photon path length distributions for various atmospheric cloud situations which will lead to a better understanding of the influence of clouds on the atmospheric radiative transport. Following principles from ground based photon path length retrieval (Funk et al., 2003), our research uses the combination of space based measurements of the oxygen A-band and radiative transfer simulations. The experimental spectra originate from the Japanese Greenhouse gases Observing SATellite (GOSAT), more precisely the Fourier Transform Spectrometer TANSO-FTS. Its high spectral resolution allows to almost completely resolve the individual absorption lines which is a prerequisite to our study. The Monte Carlo radiative transfer model McArtim (Deutschmann et al., 2011) is used to model the measured spectra. This model allows user-defined input for the altitude dependent cross sections and furthermore the incorporation of three dimensional cloud shapes and properties. From the simulation output and the sun-satellite geometry, photon path length distributions can be obtained. Distributions of photon path lengths are presented for a selection of GOSAT observations of entirely cloud covered atmospheres with similar measurement geometries.

Kremmling, Beke; Penning de Vries, Marloes; Wagner, Thomas

2014-05-01

15

Path Length Fluctuations Derived from Site Testing Interferometer Data  

NASA Technical Reports Server (NTRS)

To evaluate possible sites for NASA's proposed Ka-band antenna array, the NASA Glenn Research Center has constructed atmospheric phase monitors (APM) which directly measure the tropospheric phase stability. These instruments observe an unmodulated 20.2 GHz beacon signal broadcast from a geostationary satellite (Anik F2) and measure the phase difference between the signals received by the two antennas. Two APM's have been deployed, one at the NASA Deep Space Network (DSN) Tracking Complex in Goldstone, California, and the other at the NASA White Sands Complex, in Las Cruces, New Mexico. Two station-years of atmospheric phase fluctuation data have been collected at Goldstone since operations commenced in May 2007 and 0.5 station-years of data have been collected at White Sands since operations began February 2009. With identical instruments operating simultaneously, we can directly compare the phase stability at the two sites. Phase stability is analyzed statistically in terms of the root-mean-square (rms) of the tropospheric path length fluctuations over 10 min blocks. Correlation between surface wind speed and relative humidity with interferometer phase are discussed. For 2 years, the path length fluctuations at the DSN site in Goldstone, California, have been better than 757 micrometer (with reference to a 300 m baseline and to Zenith) for 90 percent of the time. For the 6 months of data collected at White Sands, New Mexico, the path length fluctuations have been better than 830 micrometers (with reference to a 300 m baseline and to Zenith) for 90 percent of the time. This type of data analysis, as well as many other site quality characteristics (e.g., rain attenuation, infrastructure, etc.), will be used to determine the suitability of both sites for NASA s future communication services at Ka-band using an array of antennas.

Acosta, Roberto J.; Nessel, James A.; Morse, Jacquelynne R.

2010-01-01

16

Path Length Entropy Analysis of Diastolic Heart Sounds  

PubMed Central

Early detection of coronary artery disease (CAD) using the acoustic approach, a noninvasive and cost-effective method, would greatly improve the outcome of CAD patients. To detect CAD, we analyze diastolic sounds for possible CAD murmurs. We observed diastolic sounds to exhibit 1/f structure and developed a new method, path length entropy (PLE) and a scaled version (SPLE), to characterize this structure to improve CAD detection. We compare SPLE results to Hurst exponent, Sample entropy and Multi-scale entropy for distinguishing between normal and CAD patients. SPLE achieved a sensitivity-specificity of 80%–81%, the best of the tested methods. However, PLE and SPLE are not sufficient to prove nonlinearity, and evaluation using surrogate data suggests that our cardiovascular sound recordings do not contain significant nonlinear properties. PMID:23930808

Griffel, B.; Zia, M. K.; Fridman, V.; Saponieri, C.; Semmlow, J. L.

2013-01-01

17

Long-length contaminated equipment disposal process path document  

SciTech Connect

The first objective of the LLCE Process Path Document is to guide future users of this system on how to accomplish the cradle-to-grave process for the disposal of long-length equipment. Information will be provided describing the function and approach to each step in the process. Pertinent documentation, prerequisites, drawings, procedures, hardware, software, and key interfacing organizations will be identified. The second objective is related to the decision to lay up the program until funding is made available to complete it or until a need arises due to failure of an important component in a waste tank. To this end, the document will identify work remaining to be completed for each step of the process and open items or issues that remain to be resolved.

McCormick, W.A.

1998-09-30

18

Estimation of path length factor for measurement of haemoglobin concentration in the exposed cortical tissue  

NASA Astrophysics Data System (ADS)

The change in oxy- and deoxy haemoglobin in the cortical tissue caused by brain function can be measured from multi-spectral images of exposed cortex. We cannot ignore the wavelength dependence of mean optical path length of detected light to calculate the accurate changes in concentrations of oxy- and deoxy- haemoglobin in the cortical tissue. The optical path length factor, which reflects the wavelength dependence of mean optical path length, is experimentally estimated from the multi-spectral images of exposed cortex of guinea pigs. The optical path length factor improves the accuracy in changes in concentrations of oxy- and deoxy-haemoglobin obtained from the multi-spectral images.

Sakaguchi, K.; Tachibana, T.; Yokoyama, K.; Furukawa, S.; Katsura, T.; Maki, A.; Kawaguchi, H.; Okada, E.

2005-08-01

19

High reflected cubic cavity as long path absorption cell for infrared gas sensing  

NASA Astrophysics Data System (ADS)

One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

Yu, Jia; Gao, Qiang; Zhang, Zhiguo

2014-10-01

20

Laser Metrology for an Optical-Path-Length Modulator  

NASA Technical Reports Server (NTRS)

Laser gauges have been developed to satisfy requirements specific to monitoring the amplitude of the motion of an optical-path-length modulator that is part of an astronomical interferometer. The modulator includes a corner-cube retroreflector driven by an electromagnetic actuator. During operation of the astronomical interferometer, the electromagnet is excited to produce linear reciprocating motion of the corner-cube retroreflector at an amplitude of 2 to 4 mm at a frequency of 250, 750, or 1,250 Hz. Attached to the corner-cube retroreflector is a small pick-off mirror. To suppress vibrations, a counterweight having a mass equal to that of the corner-cube retroreflector and pick-off mirror is mounted on another electromagnetic actuator that is excited in opposite phase. Each gauge is required to measure the amplitude of the motion of the pick-off mirror, assuming that the motions of the pick-off mirror and the corner-cube retroreflector are identical, so as to measure the amplitude of motion of the corner- cube retroreflector to within an error of the order of picometers at each excitation frequency. Each gauge is a polarization-insensitive heterodyne interferometer that includes matched collimators, beam separators, and photodiodes (see figure). The light needed for operation of the gauge comprises two pairs of laser beams, the beams in each pair being separated by a beat frequency of 80 kHz. The laser beams are generated by an apparatus, denoted the heterodyne plate, that includes stabilized helium-neon lasers, acousto-optical modulators, and associated optical and electronic subsystems. The laser beams are coupled from the heterodyne plate to the collimators via optical fibers.

Gursel, Yekta

2005-01-01

21

A New Path Length Measure Based on GO for Gene Similarity with Evaluation using SGD Pathways  

Microsoft Academic Search

We propose a new method for measuring the semantic similarity of genes based on path length between their annotation terms in the Gene Ontology. Our method applies an exponential transfer function to the average path length between two genes to compute their similarity. The non-linear measure ensures that the semantic similarity decreases with distance and proves to be quite competitive

Anurag Nagar; Hisham Al-mubaid

2008-01-01

22

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2012 CFR

... false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication...78.108 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2012-10-01

23

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2013 CFR

... false Minimum path lengths for fixed links. 74.644 Section 74.644 Telecommunication...74.644 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2013-10-01

24

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2011 CFR

... false Minimum path lengths for fixed links. 74.644 Section 74.644 Telecommunication...74.644 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2011-10-01

25

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

... false Minimum path lengths for fixed links. 74.644 Section 74.644 Telecommunication...74.644 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2010-10-01

26

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2011 CFR

... false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication...78.108 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2011-10-01

27

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2012 CFR

... false Minimum path lengths for fixed links. 74.644 Section 74.644 Telecommunication...74.644 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2012-10-01

28

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

... false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication...78.108 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2010-10-01

29

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2014 CFR

... false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication...78.108 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2014-10-01

30

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2014 CFR

... false Minimum path lengths for fixed links. 74.644 Section 74.644 Telecommunication...74.644 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2014-10-01

31

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2013 CFR

... false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication...78.108 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the value set...

2013-10-01

32

Comparison between Path Lengths Traveled by Solar Electrons and Ions in Ground-Level Enhancement Events  

NASA Astrophysics Data System (ADS)

We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT ion data to investigate the path length difference between solar electrons and ions in the ground-level enhancement (GLE) events in solar cycle 23. Assuming that the onset time of metric type II or decameter-hectometric (DH) type III radio bursts is the solar release time of non-relativistic electrons, we have found that within an error range of ±10% the deduced path length of low-energy (~27 keV) electrons from their release site near the Sun to the 1 AU observer is consistent with the ion path length deduced by Reames from the onset time analysis. In addition, the solar longitude distribution and IMF topology of the GLE events examined are in favor of the coronal mass ejection-driven shock acceleration origin of observed non-relativistic electrons. We have also found an increase of electron path lengths with increasing electron energies. The increasing rate of path lengths is correlated with the pitch angle distribution (PAD) of peak electron intensities locally measured, with a higher rate corresponding to a broader PAD. The correlation indicates that the path length enhancement is due to the interplanetary scattering experienced by first arriving electrons. The observed path length consistency implies that the maximum stable time of magnetic flux tubes, along which particles transport, could reach 4.8 hr.

Tan, Lun C.; Malandraki, Olga E.; Reames, Donald V.; Ng, Chee K.; Wang, Linghua; Patsou, Ioanna; Papaioannou, Athanasios

2013-05-01

33

Comparison Between Path Lengths Traveled by Solar Electrons and Ions in Ground-Level Enhancement Events  

NASA Technical Reports Server (NTRS)

We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT ion data to investigate the path length difference between solar electrons and ions in the ground-level enhancement (GLE) events in solar cycle 23. Assuming that the onset time of metric type II or decameter-hectometric (DH) type III radio bursts is the solar release time of non-relativistic electrons, we have found that within an error range of plus or minus 10% the deduced path length of low-energy (approximately 27 keV) electrons from their release site near the Sun to the 1 AU observer is consistent with the ion path length deduced by Reames from the onset time analysis. In addition, the solar longitude distribution and IMF topology of the GLE events examined are in favor of the coronal mass ejection-driven shock acceleration origin of observed non-relativistic electrons.We have also found an increase of electron path lengths with increasing electron energies. The increasing rate of path lengths is correlated with the pitch angle distribution (PAD) of peak electron intensities locally measured, with a higher rate corresponding to a broader PAD. The correlation indicates that the path length enhancement is due to the interplanetary scattering experienced by first arriving electrons. The observed path length consistency implies that the maximum stable time of magnetic flux tubes, along which particles transport, could reach 4.8 hr.

Tan, Lun C.; Malandraki, Olga E.; Reames, Donald; NG, Chee K.; Wang, Linghua; Patsou, Ioanna; Papaioannou, Athanasios

2013-01-01

34

Geometrical path length probability density functions of the skylight transmitted by midlatitude cloudy skies: Some case studies  

NASA Astrophysics Data System (ADS)

Examples of inferred probability density functions of geometrical path lengths (PDF-GP) for zenith-scattered skylight transmitted by cloudy skies at midlatitude (50°N, 8.2°E) are reported. The method relies on high resolution spectroscopy of the O2 A-band (760nm-780nm) absorption in the transmitted skylight, and an·inverse Laplace transform to recover the PDF-GP from the absorption strengths of a set of A-band absorption lines. Some examples of a larger set of measurements are presented and discussed in detail. These examples include PDF-GPs for typical midlatitude summer (fair weather Cumulus) and winter (Stratus) cloudiness. Moreover, two cloud observations with largely enhanced O2 A-band absorptions (up to a factor of 7 implying a mean geometrical path length of about 116 km) are discussed, namely the PDF-GPs of thunderstorm clouds (Cumulonimbus, Cb) and of clouds formed in a cold front (Stratocumulus, Sc; Altostratus, As; Nimbostratus, Ns; Cirrus, Ci).

Veitel, H.; Funk, O.; Kurz, C.; Platt, U.; Pfeilsticker, K.

35

A Faster Algorithm for the Single Source Shortest Path Problem with Few Distinct Positive Lengths  

E-print Network

In this paper, we propose an efficient method for implementing Dijkstra's algorithm for the Single Source Shortest Path Problem (SSSPP) in a graph whose edges have positive length, and where there are few distinct edge ...

Orlin, James B.

36

High resolution sound velocity measurement in liquid3He using path length modulation technique  

Microsoft Academic Search

Employing path length modulation technique, we are able to make high resolution sound velocity measurements (≈ 10 ppm) with a relatively short path length. We present new values of F {2\\/3} calculated from zeroand first-sound velocity measurements at 12.6 MHz in liquid3He over the pressure range of 0.6 to 14 bar. We also report a newly observed behavior in high

Y. Lee; P. J. Hamot; D. T. Sprague; T. M. Haard; J. B. Kycia; M. R. Rand; W. P. Halperin

1996-01-01

37

High resolution sound velocity measurement in liquid 3 He using path length modulation technique  

Microsoft Academic Search

Employing path length modulation technique, we are able to make high resolution sound velocity measurements (? 10 ppm) with\\u000a a relatively short path length. We present new values ofF\\u000a 23 calculated from zeroand first-sound velocity measurements at 12.6 MHz in liquid3He over the pressure range of 0.6 to 14 bar. We also report a newly observed behavior in high frequency

Y. Lee; P. J. Hamot; D. T. Sprague; T. M. Haard; J. B. Kycia; M. R. Rand; W. P. Halperin

1996-01-01

38

An Exact Algebraic Evaluation of Path-Length Difference for Two-Source Interference  

NASA Astrophysics Data System (ADS)

When studying wave interference, one often wants to know the difference in path length for two waves arriving at a common point P but coming from adjacent sources. For example, in many contexts interference maxima occur where this path-length difference is an integer multiple of the wavelength. The standard approximation for the path-length difference is path-length difference?dsin ?, where d is the distance between the sources and ? is the angle between the perpendicular bisector of d and the line connecting P to the midpoint of d. A common derivation of Eq. (1) begins with the seemingly paradoxical approximation that two paths that meet at a common point can be treated as parallel. In this paper we present an alternative derivation that first finds a simple, exact expression for the path-length difference, valid even when the paths clearly are not parallel. We then show the circumstances under which Eq. (1) is a useful approximation to the exact expression and finally determine an upper limit to the error inherent in using Eq. (1) in place of the exact expression. No math is required beyond the Pythagorean theorem and simple algebra.

Hopper, Seth; Howell, John

2006-11-01

39

Optimization of transport protocols with path-length constraints in complex networks.  

PubMed

We propose a protocol optimization technique that is applicable to both weighted and unweighted graphs. Our aim is to explore by how much a small variation around the shortest-path or optimal-path protocols can enhance protocol performance. Such an optimization strategy can be necessary because even though some protocols can achieve very high traffic tolerance levels, this is commonly done by enlarging the path lengths, which may jeopardize scalability. We use ideas borrowed from extremal optimization to guide our algorithm, which proves to be an effective technique. Our method exploits the degeneracy of the paths or their close-weight alternatives, which significantly improves the scalability of the protocols in comparison to shortest-path or optimal-path protocols, keeping at the same time almost intact the length or weight of the paths. This characteristic ensures that the optimized routing protocols are composed of paths that are quick to traverse, avoiding negative effects in data communication due to path-length increases that can become specially relevant when information losses are present. PMID:21230151

Ramasco, José J; de La Lama, Marta S; López, Eduardo; Boettcher, Stefan

2010-09-01

40

Three-dimensional cortex model including vascular structure for estimation of path length for optical imaging  

NASA Astrophysics Data System (ADS)

Optical imaging of hemoglobin concentration changes in the exposed cortex has been used to investigate the functional brain activation. The concentration changes in oxygenated and deoxygenated hemoglobin can be independently obtained from the dual- or multi-wavelength measurements of the change in reflectance of the exposed cortex and wavelengthdependent optical path length in the cortical tissues. In the previous studies, the partial optical path length were generally estimated by homogeneous and layered models. In reality, the concentration changes in the hemoglobin only occurs in the blood vessels. In this study, the partial optical path lengths in the blood vessels were estimated by the heterogeneous model including the blood vessel structure based upon the image acquired by two-photon microscopy. Light propagation in the exposed-cortex model is simulated to estimate the wavelength dependence of the partial optical path length in the blood vessels. The wavelength dependence of the partial optical path length for the heterogeneous model was different from that for the homogeneous model. In the wavelength range from 500 to 580 nm, the partial optical path length in the blood vessels was mainly affected by the structure of the blood vessels in the region shallower than 50 ?m.

Kikuchi, Takahiro; Takuwa, Hiroyuki; Masamoto, Kazuto; Ito, Hiroshi; Okada, Eiji

2013-06-01

41

Generating minimax-curvature and shorter ?3-spline path using multi-objective variable-length genetic algorithm  

Microsoft Academic Search

As a continuing work on G3-continuous path planning for nonholonomic wheeled unicycle-type nonholo-nomic mobile robot in the predefined static environment, this paper accounts for a multi-objective path optimization problem that directly incorporates the objectives of simultaneously minimizes the total path length and the maximum curvature along the path. Using easily customized variable-length Island-based Parallel Genetic Algorithm (IPGA) as a path

Jiun-Hau Wei; Jing-Sin Liu

2010-01-01

42

Visual target distance, but not visual cursor path length produces shifts in motor behavior  

PubMed Central

When using tools effects in body space and distant space often do not correspond. Findings so far demonstrated that in this case visual feedback has more impact on action control than proprioceptive feedback. The present study varies the dimensional overlap between visual and proprioceptive action effects and investigates its impact on aftereffects in motor responses. In two experiments participants perform linear hand movements on a covered digitizer tablet to produce ?-shaped cursor trajectories on the display. The shape of hand motion and cursor motion (linear vs. curved) is dissimilar and therefore does not overlap. In one condition the length of hand amplitude and visual target distance is similar and constant while the length of the cursor path is dissimilar and varies. In another condition the length of the hand amplitude varies while the lengths of visual target distance (similar or dissimilar) and cursor path (dissimilar) are constant. First, we found that aftereffects depended on the relation between hand path length and visual target distance, and not on the relation between hand and cursor path length. Second, increasing contextual interference did not reveal larger aftereffects. Finally, data exploration demonstrated a considerable benefit from gain repetitions across trials when compared to gain switches. In conclusion, dimensional overlap between visual and proprioceptive action effects modulates human information processing in visually controlled actions. However, adjustment of the internal model seems to occur very fast for this kind of simple linear transformation, so that the impact of prior visual feedback is fleeting. PMID:24672507

Wendker, Nike; Sack, Oliver S.; Sutter, Christine

2014-01-01

43

a Shortest Path Algorithm for a Network with Various Fuzzy Arc Lengths  

NASA Astrophysics Data System (ADS)

We are concerned with the design of a model and an algorithm for computing a shortest path in a network having various types of fuzzy arc lengths. First, we develop a new technique for the addition of various fuzzy numbers in a path using ? -cuts. Then, we propose a regression model for obtaining membership function for the considered addition. Finally, we present a dynamic programming method for finding a shortest path in the network. An example is worked out to illustrate the applicability of the proposed approach.

Tajdin, Ali; Mahdavi, Iraj; Mahdavi-Amiri, Nezam; Sadeghpour-Gildeh, Bahram; hadighi, Rofideh

2010-06-01

44

Analysis of light propagation in highly scattering media by path-length-assigned Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Numerical analysis of optical propagation in highly scattering media is investigated when light is normally incident to the surface and re-emerges backward from the same point. This situation corresponds to practical light scattering setups, such as in optical coherence tomography. The simulation uses the path-length-assigned Monte Carlo method based on an ellipsoidal algorithm. The spatial distribution of the scattered light is determined and the dependence of its width and penetration depth on the path-length is found. The backscattered light is classified into three types, in which ballistic, snake, and diffuse photons are dominant.

Ishii, Katsuhiro; Nishidate, Izumi; Iwai, Toshiaki

2014-05-01

45

Atmospheric water vapor differential absorption measurements on vertical paths with a CO2 lidar.  

PubMed

Ground based vertical path differential absorption measurements were obtained up to a height of 1.5 km with a CO2 lidar transmitting alternatively on the R(20) (10.247-microm) and R(18) (10.260-microm) lines during daylight in conditions of both strong and weak temperature inversions. The differential absorption between these lines for typical middle latitude lower atmosphere water vapor concentrations appears to be well suited to this type of measurement as the power loss on the more absorbed backscattered line [R(20)] is not too great as to unduly restrict the operating range, while the power differential is still sufficiently large to be readily measureable. In one set of measurements a strong temperature inversion at a height of 1 km resulted in a rapid vertical lapse in aerosol concentration with a consequent loss of SNR on the returns and severe distortion to the differential absorption profiles at this level. Water vapor profiles were derived from all measurements except in the region of the strong temperature inversion where the atmospheric backscattering cross section decayed rapidly. Reasonable results were obtained through the weak inversion region. The measurement capability of the lidar was found to be restricted by the length of the laser pulse tail and an inadequate signal-to-noise performance in regions of strong temperature inversions due to the associated decreases in aerosol concentration. PMID:18196122

Baker, P W

1983-08-01

46

Achromatic recirculated chicane with fixed geometry and independently variable path length and momentum compaction  

DOEpatents

A particle beam recirculated chicane geometry that, through the inducement of a pair of 180 degree bends directed by the poles of a pair of controllable magnetic fields allows for variation of dipole position, return loop radii and steering/focussing, thereby allowing the implementation of independent variation of path length and momentum compaction.

Douglas, David R.; Neil, George R.

2005-04-26

47

A New Path Length Measure Based on GO for Gene Similarity with Evaluation Using SGD Pathways  

E-print Network

A New Path Length Measure Based on GO for Gene Similarity with Evaluation Using SGD Pathways Anurag the Saccharomyces Genome Database (SGD) taking part in various cellular pathways. We analyzed 152 pathways from SGD methods in certain cases. Keywords: Gene similarity, GO term similarity, Gene similarity in SGD. 1

Al-Mubaid, Hisham

48

Acoustic method for measuring the sound speed of gases over small path lengths  

E-print Network

Acoustic method for measuring the sound speed of gases over small path lengths J. S. Olfert,a M. D, Canada Received 9 February 2007; accepted 8 April 2007; published online 9 May 2007 Acoustic "phase shift this method the discrete acoustic wave and phase detection DAWPD method. Experimental results show

49

Path Length Control in a Nulling Coronagraph with a MEMS Deformable Mirror and a Calibration Interferometer  

NASA Technical Reports Server (NTRS)

We report progress on a nulling coronagraph intended for direct imaging of extrasolar planets. White light is suppressed in an interferometer, and phase errors are measured by a second interferometer. A 1020-pixel MEMS deformable mirror in the first interferometer adjusts the path length across the pupil. A feedback control system reduces deflections of the deformable mirror to order of 1 nm rms.

Rao, Shanti R.; Wallacea, J. Kent; Samuele, Rocco; Chakrabarti, Supriya; Cook, Timothy; Hicks, Brian; Jung, Paul; Lane, Benjamin; Levine, B. Martin; Mendillo, Chris; Schmidtlin, Edouard; Shao, Mike; Stewart, Jason B.

2008-01-01

50

Qualms Regarding the Optimality of Cumulative Path Length Control in CSA\\/CMA-Evolution Strategies  

Microsoft Academic Search

The cumulative step-size adaptation (CSA) based on path length control is regarded as a robust alternative to the standard mutative self-adaptation technique in evolution strategies (ES), guaranteeing an almost optimal control of the mutation operator. In this short paper it is shown that the underlying basic assumption in CSA - the per- pendicularity of expected consecutive steps - does not

Hans-georg Beyer; Dirk V. Arnold

2003-01-01

51

ABSORPTION TIME AND TREE LENGTH OF THE KINGMAN COALESCENT AND THE GUMBEL DIS-  

E-print Network

ABSORPTION TIME AND TREE LENGTH OF THE KINGMAN COALESCENT AND THE GUMBEL DIS- TRIBUTION M. M¨ohle1 to revisit the moments and central moments of the classical Gumbel distribution. Keywords: absorption time of coalescent processes (restricted to a sample of size n N) such as the number of jumps, the absorption time

Möhle, Martin

52

Tapered laser rods as a means of minimizing the path length of trapped barrel mode rays  

DOEpatents

By tapering the diameter of a flanged barrel laser rod over its length, the maximum trapped path length of a barrel mode can be dramatically reduced, thereby reducing the ability of the trapped spontaneous emission to negatively impact laser performance through amplified spontaneous emission (ASE). Laser rods with polished barrels and flanged end caps have found increasing application in diode array end-pumped laser systems. The polished barrel of the rod serves to confine diode array pump light within the rod. In systems utilizing an end-pumping geometry and such polished barrel laser rods, the pump light that is introduced into one or both ends of the laser rod, is ducted down the length of the rod via the total internal reflections (TIRs) that occur when the light strikes the rod's barrel. A disadvantage of using polished barrel laser rods is that such rods are very susceptible to barrel mode paths that can trap spontaneous emission over long path lengths. This trapped spontaneous emission can then be amplified through stimulated emission resulting in a situation where the stored energy available to the desired lasing mode is effectively depleted, which then negatively impacts the laser's performance, a result that is effectively reduced by introducing a taper onto the laser rod.

Beach, Raymond J.; Honea, Eric C.; Payne, Stephen A.; Mercer, Ian; Perry, Michael D.

2005-08-30

53

Path-length measurement performance evaluation of polarizing laser interferometer prototype  

NASA Astrophysics Data System (ADS)

The space laser interferometer has been considered the most promising means for detecting gravitational waves and improving the accuracy and spatial resolution of the Earth's gravity model. An on-ground polarizing laser interferometer prototype equipped with one reference interferometer and two measurement interferometers having equal-length arms is presented in the paper. The laser interferometer prototype is designed as the demonstration of a Chinese space laser interferometer antenna in the future, of which the path-length measurement performance evaluation and preliminary noise analysis are investigated here. The results show that the path-length measurement sensitivity is better than 200 pm/Hz½ in the frequency band of 10 mHz-1 Hz, and the sensitivity of measuring the motion of a sinusoidally driven testmass is better than 100 pm within the frequency regime of 1 mHz-1 Hz. In this way, laboratory activities have demonstrated the feasibility of this prototype to measure tiny path-length fluctuations of the simulated testmass. As a next step, adopting an integrated design of optics and optical substrate to enhance the stability of the laser interferometer is being planned, and other key techniques included in the space laser interferometer such as laser pointing modulation and laser phase-locking control are to be implanted into this prototype are under consideration.

Li, Yu-qiong; Luo, Zi-ren; Liu, He-shan; Dong, Yu-hui; Jin, Gang

2015-02-01

54

Modeling the average shortest-path length in growth of word-adjacency networks  

NASA Astrophysics Data System (ADS)

We investigate properties of evolving linguistic networks defined by the word-adjacency relation. Such networks belong to the category of networks with accelerated growth but their shortest-path length appears to reveal the network size dependence of different functional form than the ones known so far. We thus compare the networks created from literary texts with their artificial substitutes based on different variants of the Dorogovtsev-Mendes model and observe that none of them is able to properly simulate the novel asymptotics of the shortest-path length. Then, we identify the local chainlike linear growth induced by grammar and style as a missing element in this model and extend it by incorporating such effects. It is in this way that a satisfactory agreement with the empirical result is obtained.

Kulig, Andrzej; Dro?d?, Stanis?aw; Kwapie?, Jaros?aw; O?wiȩcimka, Pawe?

2015-03-01

55

An algorithm using length-r paths to approximate subgraph isomorphism  

Microsoft Academic Search

The 'LeRP' algorithm approximates subgraph isomorphism for attributed graphs based on counts of Length-R Paths. The algorithm provides a good approximation to the maximal isomorphic subgraph. The basic approach of the LeRP algorithm differs fundamentally from other methods. When comparing structural similarity LeRP uses a neighborhood of nodes that varies in size dynamically. This approach provides sufficient evidence of similarity

Fred W. Depiero; David K. Krout

2003-01-01

56

A Graduated Cylinder Colorimeter: An Investigation of Path Length and the Beer-Lambert Law  

NASA Astrophysics Data System (ADS)

A 10-mL graduated cylinder was used to construct a colorimeter to investigate the relationship between absorbance and path length found in the Beer-Lambert law. Light-emitting diodes (LEDs) were used as the light sources and filter monochromators. The experiments were conducted on intensely colored permanganate and tetraamminecopper(II) solutions. The device also was useful for demonstrating the relationship between absorbance and concentration.

Gordon, James; Harman, Stephanie

2002-05-01

57

Optimum frequencies of a passive microwave radiometer for tropospheric path-length correction  

Microsoft Academic Search

Radio-astronomical observations require accurate calibration of tropospheric path length. Such calibration can be achieved by microwave radiometers operating near the 22-GHz water vapor line. However, the performances of current passive microwave radiometers are meteorology-profile dependent. This is shown due mainly to incorrect frequency combinations and to saturation of brightness temperatures. By properly selecting an optimum frequency pair and removing the

Sien-Chong Wu

1979-01-01

58

Visibility oscillation in a multimode laser interferometer signal and its use in optimizing path lengths  

NASA Astrophysics Data System (ADS)

The interference signal visibility V (difference to sum ratio of intensities at maximum and minimum interference) of an interferometer that uses a multimode laser is here derived for a given laser gain profile and spectral mode separation as a function of the difference ZS between the probe and reference beam optical path lengths and the spectral separation kS between the center of the laser gain profile and the nearest laser mode of higher frequency. kS has a significant effect on V for a given ZS. This parameter, in lasers where it sweeps freely across the gain profile, and other effects, such as various misalignments and optical coupling inefficiencies, render V alone an unreliable parameter for quantifying ZS (for the purpose of reducing it, say). However, the difference to sum ratio of the maximum and minimum V due to variations in kS for a given ZS is an intrinsic property of the laser insensitive to configurational details. Parameter W so defined, therefore, proves very useful for balancing path lengths. This is of particular importance for systems where probe and/or reference beams are transmitted via long single mode optical fibers, so this application is detailed. Optical path lengths within such fibers often cannot be measured to sufficient accuracy by spatial path length measurements due to fiber nonuniformity resulting in variations in the mode's group velocity (needed to convert to optical path length). Two examples are provided using different makes and models of 0.633 ?m HeNe lasers with similar specifications. In the first case, the function W(ZS) is calculated directly from the laser's published gain profile and mode separation. In the second case, W is determined empirically for a range of ZS values for a laser with an unknown gain profile in a (heterodyned) interferometer whose interference signal oscillates between maximum and minimum intensity at 80 MHz due to the reference beam's optical frequency being acousto-optically upshifted by that amount, while kS spontaneously varies on an acoustic time scale. A single high-bandwidth waveform record for each ZS, therefore, provides all the information needed to determine W. Despite the second laser's gain profile apparently differing in detail, qualitative agreement is achieved between the two methods sufficient to validate the technique.

Ruden, E. L.; Camacho, J. F.; Lynn, A. G.

2013-10-01

59

Visibility oscillation in a multimode laser interferometer signal and its use in optimizing path lengths.  

PubMed

The interference signal visibility V (difference to sum ratio of intensities at maximum and minimum interference) of an interferometer that uses a multimode laser is here derived for a given laser gain profile and spectral mode separation as a function of the difference Z(S) between the probe and reference beam optical path lengths and the spectral separation k(S) between the center of the laser gain profile and the nearest laser mode of higher frequency. k(S) has a significant effect on V for a given Z(S). This parameter, in lasers where it sweeps freely across the gain profile, and other effects, such as various misalignments and optical coupling inefficiencies, render V alone an unreliable parameter for quantifying Z(S) (for the purpose of reducing it, say). However, the difference to sum ratio of the maximum and minimum V due to variations in k(S) for a given Z(S) is an intrinsic property of the laser insensitive to configurational details. Parameter W so defined, therefore, proves very useful for balancing path lengths. This is of particular importance for systems where probe and/or reference beams are transmitted via long single mode optical fibers, so this application is detailed. Optical path lengths within such fibers often cannot be measured to sufficient accuracy by spatial path length measurements due to fiber nonuniformity resulting in variations in the mode's group velocity (needed to convert to optical path length). Two examples are provided using different makes and models of 0.633 ?m HeNe lasers with similar specifications. In the first case, the function W(Z(S)) is calculated directly from the laser's published gain profile and mode separation. In the second case, W is determined empirically for a range of Z(S)values for a laser with an unknown gain profile in a (heterodyned) interferometer whose interference signal oscillates between maximum and minimum intensity at 80 MHz due to the reference beam's optical frequency being acousto-optically upshifted by that amount, while k(S) spontaneously varies on an acoustic time scale. A single high-bandwidth waveform record for each Z(S), therefore, provides all the information needed to determine W. Despite the second laser's gain profile apparently differing in detail, qualitative agreement is achieved between the two methods sufficient to validate the technique. PMID:24182097

Ruden, E L; Camacho, J F; Lynn, A G

2013-10-01

60

Cosmic-ray propagation in the Galaxy and in the heliosphere - The path-length distribution at low energy  

NASA Technical Reports Server (NTRS)

The energy dependence of the path-length distribution of cosmic rays at low energies, below relativistic velocities, is studied, and its implications for models of cosmic-ray confinement and propagation in the Galaxy and Galactic halo, including the effects of a possible Galactic wind, are studied. It is found that the mean free path in Galactic propagation must be fully energy-dependent, with the mean of an exponential path-length distribution increasing with increasing energy below 1 GeV per nucleon and decreasing with increasing energy above 1 GeV per nucleon. This indicates that, at low energies, diffusion is not the controlling process. The path-length distribution is not purely exponential but is depleted in short path lengths at low energies. This depletion is energy-dependent, being largest at low energies and decreasing with increasing energy.

Garcia-Munoz, M.; Simpson, J. A.; Guzik, T. G.; Wefel, J. P.; Margolis, S. H.

1987-01-01

61

Length dependent thermal conductivity measurements yield phonon mean free path spectra in nanostructures.  

PubMed

Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J

2015-01-01

62

Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures  

PubMed Central

Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J.

2015-01-01

63

Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures  

NASA Astrophysics Data System (ADS)

Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron.

Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J.

2015-03-01

64

LHC Predictions from an extended theory with Elastic, Inelastic, and Path Length Fluctuating Energy Loss  

E-print Network

We present the LHC predictions for the WHDG model of radiative, elastic, and path length fluctuating energy loss. We find the pT dependence of RAA is qualitatively very different from AWS-based energy loss extrapolations to the LHC; the large pT reach of the year one data at the LHC should suffice to distinguish between the two. We also discuss the importance of requiring a first elastic scatter before any medium-induced elastic or radiative loss occurs, a necessary physical effect not considered in any previous models.

William A. Horowitz

2007-02-27

65

New method for path-length equalization of long single-mode fibers for interferometry  

NASA Astrophysics Data System (ADS)

The ability to use single mode (SM) fibers for beam transport in optical interferometry offers practical advantages over conventional long vacuum pipes. One challenge facing fiber transport is maintaining constant differential path length in an environment where environmental thermal variations can lead to cm-level variations from day to night. We have fabricated three composite cables of length 470 m, each containing 4 copper wires and 3 SM fibers that operate at the astronomical H band (1500-1800 nm). Multiple fibers allow us to test performance of a circular core fiber (SMF28), a panda-style polarization-maintaining (PM) fiber, and a lastly a specialty dispersion-compensated PM fiber. We will present experimental results using precision electrical resistance measurements of the of a composite cable beam transport system. We find that the application of 1200 W over a 470 m cable causes the optical path difference in air to change by 75 mm (+/- 2 mm) and the resistance to change from 5.36 to 5.50?. Additionally, we show control of the dispersion of 470 m of fiber in a single polarization using white light interference fringes (?c=1575 nm, ??=75 nm) using our method.

Anderson, M.; Monnier, J. D.; Ozdowy, K.; Woillez, J.; Perrin, G.

2014-07-01

66

A volumetric approach to path-length measurements is essential when treating radiotherapy with modulated beams.  

PubMed

The established dosimetric benefits of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy have lead to their increased use in prostate radiotherapy. Complimenting these techniques, volumetric image guidance has supported increased positional accuracy. In addition, 3-dimensional image guidance has also allowed for assessment of potential dosimetric variation that can be attributed to a deformation of either internal or external structures, such as rectal distension or body contour. Compounding these issues is the variation of tissue density through which the new field position passes and also the variation of dose across a modulated beam. Despite the growing level of interest in this area, there are only a limited number of articles that examine the effect of a variation in beam path length, particularly across a modulated field. IMRT and volumetric-modulated radiation therapy (VMAT) fields are dynamic in nature, and the dose gradient within these fields is variable. Assessment of variation of path length away from the beam?s central axis and across the entire field is vital where there is considerable variation of dose within the field, such as IMRT and VMAT. In these cases, reliance on the traditional central axis to focus skin distances is no longer appropriate. This article discusses these more subtle challenges that may have a significant clinical effect if left unrecognized and undervalued. PMID:24630910

Forde, Elizabeth; Booth, Jeremy; Leech, Michelle

2014-01-01

67

Calculation of the mean path length of the Epstein frame under non-sinusoidal excitations using the double Epstein method  

NASA Astrophysics Data System (ADS)

This paper discusses the effect of non-sinusoidal excitation on the mean path length of the Epstein frame. Two different steels, a non-oriented (NO) steel and a high-permeability grain-oriented (HGO) electrical steel have been tested under pure sinusoidal and non-sinusoidal excitations and the mean path length of the Epstein frame has been re-calculated. Results indicate that the actual mean path of the Epstein frame depends not only on the material permeability and anisotropy but also on the peak flux density and magnetising frequency. The amount of distortion of the excitation frequency also has an effect on the value of the actual mean path length of the Epstein frame.

Marketos, Philip; Zurek, Stan; Moses, Anthony J.

68

Beam splitter and method for generating equal optical path length beams  

DOEpatents

The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

Qian, Shinan; Takacs, Peter

2003-08-26

69

Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements  

NASA Technical Reports Server (NTRS)

We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

2012-01-01

70

A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements  

NASA Technical Reports Server (NTRS)

A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

2012-01-01

71

Continuous correction of differential path length factor in near-infrared spectroscopy  

PubMed Central

Abstract. In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p<0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p<0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method. PMID:23640027

Talukdar, Tanveer; Moore, Jason H.; Diamond, Solomon G.

2013-01-01

72

Progress Toward Redetermining the Boltzmann Constant with a Fixed-Path-Length Cylindrical Resonator  

NASA Astrophysics Data System (ADS)

A single, fixed-path-length cylindrical-cavity resonator was used to measure c 0 = (307.825 2 ± 0.001 2) m · s-1, the zero-density limit of the speed of sound in pure argon at the temperature of the triple point of water. Three even and three odd longitudinal modes were used in this measurement. Based on the ratio M/ ? 0 = (23.968 644 ± 0.000 033) g · mol-1, determined from an impurity and isotopic analysis of the argon used in this measurement and the measured c 0, the value k B = 1.380 650 6 × 10-23J · K-1 was obtained for the Boltzmann constant. This value of k B has a relative uncertainty u r( k B) = 7.9 × 10-6 and is fractionally, (0.12 ± 8.1) × 10-6 larger than the value recommended by CODATA in 2006. (The uncertainty is one standard uncertainty.) Several, comparatively large imperfections of our prototype cavity affect the even longitudinal modes more than the odd modes. The models for these imperfections are approximate, but they suggest that an improved cavity will significantly reduce the uncertainty of c 0.

Zhang, J. T.; Lin, H.; Feng, X. J.; Sun, J. P.; Gillis, K. A.; Moldover, M. R.; Duan, Y. Y.

2011-08-01

73

Changes in diffusion path length with old age in diffuse optical tomography  

NASA Astrophysics Data System (ADS)

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures.

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

74

Changes in diffusion path length with old age in diffuse optical tomography.  

PubMed

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures. PMID:22612125

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

75

Path-length-resolved dynamic light scattering in highly scattering random media: The transition to diffusing wave spectroscopy  

E-print Network

Path-length-resolved dynamic light scattering in highly scattering random media: The transition to diffusing wave spectroscopy Kostadinka K. Bizheva, Andy M. Siegel, and David A. Boas Electro diffusive light. Our experimental analysis provides details on the transition from single scattering

76

Estimation of Path Length Reduction Factor by Using One Year Rain Attenuation Statistics over a Line of Sight Link Operating at 28.75 GHz in Amritsar (INDIA)  

NASA Astrophysics Data System (ADS)

The effect of environmental factors in general and rain droplets in particular, on microwave propagation is a very well known fact now. If the rain droplets are present in an inhomogeneous way across the path length of the microwave communication system then, a new concept of path length reduction factor is introduced which accounts for the inhomogeneous nature of the rain droplets along the path length of the microwave signal. The present paper presents results of path length reduction factor using data on attenuation levels obtained on a LOS link operating at 28.75 GHz in Amritsar region and its comparison with Crane's and ITU-R's model.

Sharma, Parshotam; Hudiara, Inderjit Singh; Singh, Maninder Lal

2011-02-01

77

An open path, fast response infrared absorption gas analyzer for H2O and CO2  

NASA Astrophysics Data System (ADS)

An open path infrared absorption based instrument for fast response measurements of H2O and CO2 fluctuations is described. This instrument performed reliably in several field experiments in both terrestrial and marine environments, on both fixed (tower) and mobile (boat, plane) flux platforms. Noise levels for H2O and CO2 concentrations were less than 10 mg/m3 and 300 ?g/m3, respectively for frequencies between 0.005 and 10 Hz. Drifts in instrument output, associated with changes in instrument temperature, are compensated for electronically.

Auble, David L.; Meyers, Tilden P.

1992-05-01

78

Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar  

E-print Network

We use an airborne pulsed integrated path differential absorption lidar to make spectroscopic measurements of the pressure-induced line broadening and line center shift of atmospheric CO2 at the 1572.335 nm absorption line. We measure the absorption lineshape in the vertical column between the aircraft and ground. A comparison of our measured absorption lineshape to calculations based on HITRAN shows excellent agreement with the peak optical depth accurate to within 0.3%. Additionally, we measure changes in the line center position to within 5.2 MHz of calculations, and the absorption linewidth to within 0.6% of calculations.

Ramanathan, Anand; Allan, Graham R; Riris, Haris; Weaver, Clark J; Hasselbrack, William E; Browell, Edward V; Abshire, James B

2013-01-01

79

Influence of neglecting the curved path of the Achilles tendon on Achilles tendon length change at various ranges of motion  

PubMed Central

Abstract Achilles tendon length has been measured using a straight?line model. However, this model is associated with a greater measurement error compared with a curved?line model. Therefore, we examined the influence of neglecting the curved path of the Achilles tendon on its length change at various ranges of motion. Ten male subjects participated in this study. First, the location of the Achilles tendon was confirmed by using ultrasonography, and markers were attached on the skin over the Achilles tendon path. Then, the three?dimensional coordinates of each marker at dorsiflexion (DF) 15°, plantarflexion (PF) 0°, PF15°, and PF30° were obtained. Achilles tendon length in the curved?line model was calculated as the sum of the distances among each marker. On the other hand, Achilles tendon length in the straight?line model was calculated as the straight distance between the two most proximal and distal markers projected onto the sagittal plane. The difference of the Achilles tendon length change between curved?line and straight?line models was calculated by subtracting the Achilles tendon length change obtained in curved?line model from that obtained in straight?line model with three different ranges of motion (i.e., PF0°, PF15°, and PF30° from DF15°, respectively). As a result, the difference in Achilles tendon length change between the two models increased significantly as the range of motion increased. In conclusion, neglecting the curved path of the Achilles tendon induces substantial overestimation of its length change when the extent of ankle joint angle change is large. PMID:25303951

Fukutani, Atsuki; Hashizume, Satoru; Kusumoto, Kazuki; Kurihara, Toshiyuki

2014-01-01

80

Water-equivalent path length calibration of a prototype proton CT scanner  

SciTech Connect

Purpose: The authors present a calibration method for a prototype proton computed tomography (pCT) scanner. The accuracy of these measurements depends upon careful calibration of the energy detector used to measure the residual energy of the protons that passed through the object. Methods: A prototype pCT scanner with a cesium iodide (CsI(Tl)) crystal calorimeter was calibrated by measuring the calorimeter response for protons of 200 and 100 MeV initial energies undergoing degradation in polystyrene plates of known thickness and relative stopping power (RSP) with respect to water. Calibration curves for the two proton energies were obtained by fitting a second-degree polynomial to the water-equivalent path length versus calorimeter response data. Using the 100 MeV calibration curve, the RSP values for a variety of tissue-equivalent materials were measured and compared to values obtained from a standard depth-dose range shift measurement using a water-tank. A cylindrical water phantom was scanned with 200 MeV protons and its RSP distribution was reconstructed using the 200 MeV calibration. Results: It is shown that this calibration method produces measured RSP values of various tissue-equivalent materials that agree to within 0.5% of values obtained using an established water-tank method. The mean RSP value of the water phantom reconstruction was found to be 0.995 {+-} 0.006. Conclusions: The method presented provides a simple and reliable procedure for calibration of a pCT scanner.

Hurley, R. F.; Schulte, R. W.; Bashkirov, V. A.; Wroe, A. J.; Ghebremedhin, A.; Sadrozinski, H. F.-W.; Rykalin, V.; Coutrakon, G.; Koss, P.; Patyal, B. [Loma Linda University, 11175 Campus Street, Loma Linda, California 92354 (United States); Loma Linda University Medical Center, 11234 Anderson Street, Loma Linda, California 92354 (United States); Loma Linda University, 11175 Campus Street, Loma Linda, California 92354 (United States); Loma Linda University Medical Center, 11234 Anderson Street, Loma Linda, California 92354 (United States); University of California, Santa Cruz, 1156 High Street, Santa Cruz, California 95064 (United States); Northern Illinois University, 1120 East Diehl Road, Naperville, Illinois 60563 (United States); Loma Linda University Medical Center, 11234 Anderson Street, Loma Linda, California 92354 (United States)

2012-05-15

81

Topological versus rheological entanglement length in primitive-path analysis protocols, tube models, and slip-link models  

NASA Astrophysics Data System (ADS)

We show that the front factor appearing in the shear modulus of a phantom network, Gph=(1-2/f)(?kBT)/Ns, also controls the ratio of the strand length, Ns, and the number of monomers per Kuhn length of the primitive paths, NphPPKuhn, characterizing the average network conformation. In particular, NphPPKuhn=Ns/(1-2/f) and Gph=(?kBT)/NphPPKuhn. Neglecting the difference between cross-links and slip-links, these results can be transferred to entangled systems and the interpretation of primitive path analysis data. In agreement with the tube model, the analogy to phantom networks suggest that the rheological entanglement length, Nerheo=(?kBT)/Ge, should equal NePPKuhn. Assuming binary entanglements with f=4 functional junctions, we expect that Nerheo should be twice as large as the topological entanglement length, Netopo. These results are in good agreement with reported primitive path analysis results for model systems and a wide range of polymeric materials. Implications for tube and slip-link models are discussed.

Everaers, Ralf

2012-08-01

82

[Open-path online monitoring of ambient atmospheric CO2 based on laser absorption spectrum].  

PubMed

With the conjunction of tunable diode laser absorption spectroscopy technology (TDLAS) and the open long optical path technology, the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail, and the instrument for large-range measurement was set up. By choosing the infrared absorption line of CO2 at 1.57 microm whose line strength is strong and suitable for measurement, the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007. The diurnal atmospheric variations of CO2 and continuous monitoring results were presented. The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination. The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night, so it matches the photosynthesis trend. The instrument can detect gas concentration online with high resolution, high sensitivity, high precision, short response time and many other advantages, the monitoring requires no gas sampling, the calibration is easy, and the detection limit is about 4.2 x 10(-7). It has been proved that the system and measurement project are feasible, so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology. PMID:19385195

He, Ying; Zhang, Yu-Jun; Kan, Rui-Feng; Xia, Hui; Geng, Hui; Ruan, Jun; Wang, Min; Cui, Xiao-Juan; Liu, Wen-Qing

2009-01-01

83

On the sampling of step length in Monte Carlo simulation of trajectories with very small mean free path  

NASA Astrophysics Data System (ADS)

In an event-by-event simulation of the trajectory of a particle moving in matter it is usually assumed that the probability for the particle to travel a distance s without interaction is exp(-s/?), where ?=(n·?)-1 is the total mean free path, n the number of scatterers per unit volume and ? the total cross section per scatterer. The step length s between scattering events is then generated by means of a sampling formula s=-? ln(1-R), where R a random number in the interval 0length D=dnn and a finite probability I=1-exp(-D/?) of a single elastic or inelastic scattering event at the end of each step. According to this method, conventional sampling may exaggerate the number of events per unit path length; the corrected mean free path between events is found to be ?c=D/(1-exp(-D/?)). The correction is substantial when ? is comparable to or smaller than D, in practice for very low energy particles in liquids and solids. Consequently, quantities like stopping power may then be overestimated, while transport mean free path may be underestimated. In the opposite limit ??D, conventional and M sampling produce the same result. Present results further indicate that conventional sampling using the corrected total mean free path ?c is a good approximation to M sampling.

Liljequist, D.

2012-11-01

84

Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements  

USGS Publications Warehouse

Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 1018 molec cm?2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO2 detection limit was determined to be 2 × 1016 molec cm?2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS2) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO2 ratio (X = ClO, CS2) could be derived, and yielded 2 × 10?3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

Vita, Fabio; Kern, Christoph; Inguaggiato, Salvatore

2014-01-01

85

Development of a pulsed 2-micron integrated path differential absorption lidar for CO2 measurement  

NASA Astrophysics Data System (ADS)

Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center.

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl

2013-09-01

86

Open-path tunable diode laser absorption for eddy correlation flux measurements of atmospheric trace gases  

NASA Astrophysics Data System (ADS)

Biogenic emissions from and dry deposition to terrestrial surfaces are important processes determining the trace gas composition of the atmosphere. We have developed an instrument for flux measurements of gases such as CH4, N2O, and O3 based on the eddy correlation technique which combines trace gas fluctuation measurements with simultaneous windfield measurements. The instrument combines a tunable diode laser infrared light source with an open-path multipass absorption cell in order to provide the fast time response (approximately equals 0.1 s) and short base pathlength (0.6 m) required for the eddy correlation method. Initial field tests using the instrument to measure methane emissions from a local wetland demonstrate the capability for high precision eddy correlation flux measurements.

Anderson, Stuart M.; Zahniser, Mark S.

1991-05-01

87

Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement  

NASA Technical Reports Server (NTRS)

Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

2013-01-01

88

Ground-based integrated path coherent differential absorption lidar measurement of CO2: hard target return  

NASA Astrophysics Data System (ADS)

The National Institute of Information and Communications Technology (NICT) have made a great deal of effort to develop a coherent 2-?m differential absorption and wind lidar (Co2DiaWiL) for measuring CO2 and wind speed. First, coherent Integrated Path Differential Absorption (IPDA) lidar experiments were conducted using the Co2DiaWiL and a hard target (surface return) located about 7.12 km south of NICT on 11, 27, and 28 December 2010. The detection sensitivity of a 2-?m IPDA lidar was examined in detail using the CO2 concentration measured by the hard target. The precisions of CO2 measurement for the hard target and 900, 4500 and 27 000 shot pairs were 6.5, 2.8, and 1.2%, respectively. The results indicated that a coherent IPDA lidar with a laser operating at a high pulse repetition frequency of a few tens of KHz is necessary for measuring the CO2 concentration of the hard target with a precision of 1-2 ppm. Statistical comparisons indicated that, although a small amount of in situ data and the fact that they were not co-located with the hard target made comparison difficult, the CO2 volume mixing ratio measured with the Co2DiaWiL was about 5 ppm lower than that measured with the in situ sensor. The statistical results indicated that there were no differences between the hard target and atmospheric return measurements. A precision of 1.5% was achieved from the atmospheric return, which is lower than that obtained from the hard-target returns. Although long-range DIfferential Absorption Lidar (DIAL) CO2 measurement with the atmospheric return can result in highly precise measurement, the precision of the atmospheric return measurement was widely distributed comparing to that of the hard target return. Our results indicated that it is important to use a Q-switched laser to measure the range-gated differential absorption optical depth with the atmospheric return and that it is better to simultaneously conduct both hard target and atmospheric return measurements to enable highly accurate CO2 measurement.

Ishii, S.; Koyama, M.; Baron, P.; Iwai, H.; Mizutani, K.; Itabe, T.; Sato, A.; Asai, K.

2012-11-01

89

Investigation of an implantable dosimeter for single-point water equivalent path length verification in proton therapy  

SciTech Connect

Purpose: In vivo range verification in proton therapy is highly desirable. A recent study suggested that it was feasible to use point dose measurement for in vivo beam range verification in proton therapy, provided that the spread-out Bragg peak dose distribution is delivered in a different and rather unconventional manner. In this work, the authors investigate the possibility of using a commercial implantable dosimeter with wireless reading for this particular application. Methods: The traditional proton treatment technique delivers all the Bragg peaks required for a SOBP field in a single sequence, producing a constant dose plateau across the target volume. As a result, a point dose measurement anywhere in the target volume will produce the same value, thus providing no information regarding the water equivalent path length to the point of measurement. However, the same constant dose distribution can be achieved by splitting the field into a complementary pair of subfields, producing two oppositely ''sloped'' depth-dose distributions, respectively. The ratio between the two distributions can be a sensitive function of depth and measuring this ratio at a point inside the target volume can provide the water equivalent path length to the dosimeter location. Two types of field splits were used in the experiment, one achieved by the technique of beam current modulation and the other by manipulating the location and width of the beam pulse relative to the range modulator track. Eight MOSFET-based implantable dosimeters at four different depths in a water tank were used to measure the dose ratios for these field pairs. A method was developed to correct the effect of the well-known LET dependence of the MOSFET detectors on the depth-dose distributions using the columnar recombination model. The LET-corrected dose ratios were used to derive the water equivalent path lengths to the dosimeter locations to be compared to physical measurements. Results: The implantable dosimeters measured the dose ratios with a reasonable relative uncertainty of 1%-3% at all depths, except when the ratio itself becomes very small. In total, 55% of the individual measurements reproduced the water equivalent path lengths to the dosimeters within 1 mm. For three dosimeters, the difference was consistently less than 1 mm. Half of the standard deviations over the repeated measurements were equal or less than 1 mm. Conclusions: With a single fitting parameter, the LET-correction method worked remarkably well for the MOSFET detectors. The overall results were very encouraging for a potential method of in vivo beam range verification with millimeter accuracy. This is sufficient accuracy to expand range of clinical applications in which the authors could use the distal fall off of the proton depth dose for tight margins.

Lu, Hsiao-Ming; Mann, Greg; Cascio, Ethan [Francis H. Burr Proton Therapy Center, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Sicel Technologies, Inc., Morrisville, North Carolina 27560 (United States); Francis H. Burr Proton Therapy Center, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States)

2010-11-15

90

Simulating the Effect of Modulated Tool-Path Chip Breaking On Surface Texture and Chip Length  

Microsoft Academic Search

One method for creating broken chips in turning processes involves oscillating the cutting tool in the feed direction utilizing the CNC machine axes. The University of North Carolina at Charlotte and the Y-12 National Security Complex have developed and are refining a method to reliably control surface finish and chip length based on a particular machine's dynamic performance. Using computer

K. S. Smith; J. T. McFarland; D. A. Tursky; T. S. Assaid; W. E. Barkman; Babelay Jr. E. F

2010-01-01

91

Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement  

NASA Technical Reports Server (NTRS)

Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

2014-01-01

92

Airborne 2-micron double-pulsed integrated path differential absorption lidar for column CO2 measurement  

NASA Astrophysics Data System (ADS)

Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 mJ and up to 10 Hz repetition rate. The two laser pulses are separated by 200 µs and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-µm direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-?m IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

2014-10-01

93

Simulating the Effect of Modulated Tool-Path Chip Breaking On Surface Texture and Chip Length  

SciTech Connect

One method for creating broken chips in turning processes involves oscillating the cutting tool in the feed direction utilizing the CNC machine axes. The University of North Carolina at Charlotte and the Y-12 National Security Complex have developed and are refining a method to reliably control surface finish and chip length based on a particular machine's dynamic performance. Using computer simulations it is possible to combine the motion of the machine axes with the geometry of the cutting tool to predict the surface characteristics and map the surface texture for a wide range of oscillation parameters. These data allow the selection of oscillation parameters to simultaneously ensure broken chips and acceptable surface characteristics. This paper describes the machine dynamic testing and characterization activities as well as the computational method used for evaluating and predicting chip length and surface texture.

Smith, K.S.; McFarland, J.T.; Tursky, D. A.; Assaid, T. S.; Barkman, W. E.; Babelay, Jr., E. F.

2010-04-30

94

The effect of wafer stress on absorption coefficient and minority carrier diffusion length in cast poly-Si  

Microsoft Academic Search

The surface photovoltage (SPV) technique is an attractive method for measuring the minority carrier diffusion length of solar cells. It has the advantage of not requiring permanent sample contacts. It does require, however, an accurate knowledge of the absorption coefficient-wavelength (?-?) relationship. This relationship is well known for single-crystal silicon and SPV plots are linear for such materials. However, for

I. G. Hwang; D. K. Schroder; J. H. Wohlgemuth

1993-01-01

95

The azimuthal path of myosin V and its dependence on lever-arm length  

PubMed Central

Myosin V (myoV) is a two-headed myosin capable of taking many successive steps along actin per diffusional encounter, enabling it to transport vesicular and ribonucleoprotein cargos in the dense and complex environment within cells. To better understand how myoV navigates along actin, we used polarized total internal reflection fluorescence microscopy to examine angular changes of bifunctional rhodamine probes on the lever arms of single myoV molecules in vitro. With a newly developed analysis technique, the rotational motions of the lever arm and the local orientation of each probe relative to the lever arm were estimated from the probe’s measured orientation. This type of analysis could be applied to similar studies on other motor proteins, as well as other proteins with domains that undergo significant rotational motions. The experiments were performed on recombinant constructs of myoV that had either the native-length (six IQ motifs and calmodulins [CaMs]) or truncated (four IQ motifs and CaMs) lever arms. Native-length myoV-6IQ mainly took straight steps along actin, with occasional small azimuthal tilts around the actin filament. Truncated myoV-4IQ showed an increased frequency of azimuthal steps, but the magnitudes of these steps were nearly identical to those of myoV-6IQ. The results show that the azimuthal deflections of myoV on actin are more common for the truncated lever arm, but the range of these deflections is relatively independent of its lever-arm length. PMID:22291144

Lewis, John H.; Beausang, John F.; Sweeney, H. Lee

2012-01-01

96

Ground-based integrated path coherent differential absorption lidar measurement of CO2: foothill target return  

NASA Astrophysics Data System (ADS)

The National Institute of Information and Communications Technology (NICT) has made a great deal of effort to develop a coherent 2 ?m differential absorption and wind lidar (Co2DiaWiL) for measuring CO2 and wind speed. First, coherent Integrated Path Differential Absorption (IPDA) lidar experiments were conducted using the Co2DiaWiL and a foothill target (tree and ground surface) located about 7.12 km south of NICT on 11, 27, and 28 December 2010. The detection sensitivity of a 2 ?m IPDA lidar was examined in detail using the CO2 concentration measured by the foothill reflection. The precisions of CO2 measurements for the foothill target and 900, 4500 and 27 000 shot pairs were 6.5, 2.8, and 1.2%, respectively. The results indicated that a coherent IPDA lidar with a laser operating at a high pulse repetition frequency of a few tens of KHz is necessary for XCO2 (column-averaged dry air mixing ratio of CO2) measurement with a precision of 1-2 ppm in order to observe temporal and spatial variations in the CO2. Statistical comparisons indicated that, although a small amount of in situ data and the fact that they were not co-located with the foothill target made comparison difficult, the CO2 volume mixing ratio obtained by the Co2DiaWiL measurements for the foothill target and atmospheric returns was about -5 ppm lower than the 5 min running averages of the in situ sensor. Not only actual difference of sensing volume or the natural variability of CO2 but also the fluctuations of temperature could cause this difference. The statistical results indicated that there were no biases between the foothill target and atmospheric return measurements. The 2 ?m coherent IPDA lidar can detect the CO2 volume mixing ratio change of 3% in the 5 min signal integration. In order to detect the position of the foothill target, to measure a range with a high SNR (signal-to-noise ratio), and to reduce uncertainty due to the presence of aerosols and clouds, it is important to make a precise range measurement with a Q-switched laser and a range-gated receiver.

Ishii, S.; Koyama, M.; Baron, P.; Iwai, H.; Mizutani, K.; Itabe, T.; Sato, A.; Asai, K.

2013-05-01

97

Ground-based Photon Path Measurements from Solar Absorption Spectra of the O2 A-band  

NASA Technical Reports Server (NTRS)

High-resolution solar absorption spectra obtained from Table Mountain Facility (TMF, 34.38degN, 117.68degW, 2286 m elevation) have been analyzed in the region of the O2 A-band. The photon paths of direct sunlight in clear sky cases are retrieved from the O2 absorption lines and compared with ray-tracing calculations based on the solar zenith angle and surface pressure. At a given zenith angle, the ratios of retrieved to geometrically derived photon paths are highly precise (approx.0.2%), but they vary as the zenith angle changes. This is because current models of the spectral lineshape in this band do not properly account for the significant absorption that exists far from the centers of saturated lines. For example, use of a Voigt function with Lorentzian far wings results in an error in the retrieved photon path of as much as 5%, highly correlated with solar zenith angle. Adopting a super-Lorentz function reduces, but does not completely eliminate this problem. New lab measurements of the lineshape are required to make further progress.

Yang, Z.; Wennberg, P. O.; Cageao, R. P.; Pongetti, T. J.; Toon, G. C.; Sander, S. P.

2005-01-01

98

Acyl chain length, saturation, and hydrophobicity modulate the efficiency of dietary fatty acid absorption in adult humans.  

PubMed

Intestinal fat absorption is known to be, overall, a highly efficient process, but much less is known about the efficiency with which individual dietary fatty acids (FA) are absorbed by the adult small intestine. We therefore measured the absorption efficiency of the major dietary FA using sucrose polybehenate (SPB) as a nonabsorbable marker and analyzed how it is modulated by acyl chain physicochemical properties and polymorphisms of proteins involved in chylomicron assembly. Dietary FA absorption efficiency was measured in 44 healthy subjects fed a standard diet containing 35% fat and 5% SPB. FA and behenic acid (BA) were measured in homogenized diets and stool samples by gas chromatography-mass spectroscopy, and coefficients of absorption for each FA were calculated as 1 - [(FA/BA)feces/(FA/BA)diet]. Absorption coefficients for saturated FA decreased with increasing chain length and hydrophobicity (mean ± SE) and ranged from 0.95 ± 0.02 for myristate (14:0), 0.80 ± 0.03 for stearate (18:0), to 0.26 ± 0.02 for arachidate (20:0). Absorption coefficients for unsaturated FA increased with increasing desaturation from 0.79 ± 0.03 for elaidic acid (18:1t), 0.96 ± 0.01 for linoleate (18:2), to near complete absorption for eicosapentaenoic (20:5) and docosahexaenoic (22:6) acids. Of several common genetic polymorphisms in key proteins involved in the chylomicron assembly pathway, only the intestinal fatty acid-binding protein-2 A54T allele (rs1799883) had any impact on FA absorption. We conclude that acyl chain length, saturation, and hydrophobicity are the major determinants of the efficiency with which dietary FA are absorbed by the adult small intestine. PMID:24008359

McKimmie, Ryan L; Easter, Linda; Weinberg, Richard B

2013-11-01

99

Acyl chain length, saturation, and hydrophobicity modulate the efficiency of dietary fatty acid absorption in adult humans  

PubMed Central

Intestinal fat absorption is known to be, overall, a highly efficient process, but much less is known about the efficiency with which individual dietary fatty acids (FA) are absorbed by the adult small intestine. We therefore measured the absorption efficiency of the major dietary FA using sucrose polybehenate (SPB) as a nonabsorbable marker and analyzed how it is modulated by acyl chain physicochemical properties and polymorphisms of proteins involved in chylomicron assembly. Dietary FA absorption efficiency was measured in 44 healthy subjects fed a standard diet containing 35% fat and 5% SPB. FA and behenic acid (BA) were measured in homogenized diets and stool samples by gas chromatography-mass spectroscopy, and coefficients of absorption for each FA were calculated as 1 ? [(FA/BA)feces/(FA/BA)diet]. Absorption coefficients for saturated FA decreased with increasing chain length and hydrophobicity (mean ± SE) and ranged from 0.95 ± 0.02 for myristate (14:0), 0.80 ± 0.03 for stearate (18:0), to 0.26 ± 0.02 for arachidate (20:0). Absorption coefficients for unsaturated FA increased with increasing desaturation from 0.79 ± 0.03 for elaidic acid (18:1t), 0.96 ± 0.01 for linoleate (18:2), to near complete absorption for eicosapentaenoic (20:5) and docosahexaenoic (22:6) acids. Of several common genetic polymorphisms in key proteins involved in the chylomicron assembly pathway, only the intestinal fatty acid-binding protein-2 A54T allele (rs1799883) had any impact on FA absorption. We conclude that acyl chain length, saturation, and hydrophobicity are the major determinants of the efficiency with which dietary FA are absorbed by the adult small intestine. PMID:24008359

McKimmie, Ryan L.; Easter, Linda

2013-01-01

100

Signal and Noise Analysis of the Recent Airborne CO2 and O2 Measurements with an Integrated Path Differential Absorption Lidar  

Microsoft Academic Search

We report the signal and noise analysis of our recent airborne experiments of CO2 and O2 column concentration measurements with an integrated path differential absorption (IPDA) lidar developed for NASA's Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) mission. The O2 column absorption measurement is used to derive the atmospheric pressure, which is needed to calculate the

X. Sun; J. B. Abshire; H. Riris; A. Amediek; G. Allan; M. R. Rodriguez; W. Hasselbrack

2010-01-01

101

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation  

NASA Astrophysics Data System (ADS)

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

Moix, Jeremy M.; Ma, Jian; Cao, Jianshu

2015-03-01

102

Forster resonance energy transfer, absorption and emission spectra in multichromophoric systems: III. Exact stochastic path integral evaluation  

E-print Network

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators one can also immediately compute energy transfer rates using the multi-chromophoric Forster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion is the only perturbative method capable of generating uniformly reliable e...

Moix, Jeremy; Cao, Jianshu

2015-01-01

103

Constraints on the Path-Length Dependence of Jet Quenching in Nuclear Collisions at RHIC and LHC  

E-print Network

Recent data on the high-pT pion nuclear modification factor, $R_{AA}(p_T)$, and its elliptic azimuthal asymmetry, $v_2(p_T)$, from RHIC/BNL and LHC/CERN are analyzed in terms of a wide class of jet-energy loss models coupled to different (2+1)d transverse plus Bjorken expanding hydrodynamic fields. We test the consistency of each model by demanding a simultaneous account of the azimuthal, the transverse momentum, and the centrality dependence of the data at both 0.2 and 2.76 ATeV energies. We find a rather broad class of jet-energy independent energy-loss models $dE/dx= \\kappa(T) x^z T^{2+z} \\zeta_q$ that, when coupled to bulk constrained temperature fields T(x,t), can account for the current data at the $\\chi^2test the sensitivity of predictions to different skewed energy-loss fluctuations via a convenient scaling factor distributed in a finite range $0statistical and systematic uncertainties of the measured data does not allow a constraint on the path-length exponent z to a range narrower than [0-2].

Barbara Betz; Miklos Gyulassy

2014-10-17

104

Phase locking in a fiber laser array with varying path lengths Liping Liu, Yi Zhou, Fanting Kong, and Y. C. Chena)  

E-print Network

Phase locking in a fiber laser array with varying path lengths Liping Liu, Yi Zhou, Fanting Kong demonstrated in fiber lasers coupled to a common resonator containing a spatial filter. The phase-locked mode of which can be met in fiber laser arrays. © 2004 American Institute of Physics. [DOI: 10

105

A stochastic simulation of the propagation of Galactic cosmic rays reflecting the discreteness of cosmic ray sources Age and path length distribution  

NASA Astrophysics Data System (ADS)

Aims: The path length distribution of Galactic cosmic rays (GCRs) is the fundamental ingredient for modeling the propagation process of GCRs based on the so-called weighted slab method. We try to derive this distribution numerically by taking into account the discreteness in both space and time of occurrences of supernova explosions where GCRs are suspected to be born. The resultant age distribution and ratio of B/C are to be compared with recent observations. Methods: We solve numerically the stochastic differential equations equivalent to the Parker diffusion-convection equation which describes the propagation process of GCR in the Galaxy. We assume the three-dimensional diffusion is an isotropic one without any free escape boundaries. We ignore any energy change of GCRs and the existence of the Galactic wind for simplicity. We also assume axisymmetric configurations for the density distributions of the interstellar matter and for the surface density of supernovae. We have calculated age and path length of GCR protons arriving at the solar system with this stochastic method. The obtained age is not the escape time of GCRs from the Galaxy as usually assumed, but the time spent by GCRs during their journey to the solar system from the supernova remnants where they were born. Results: The derived age and path length show a distribution spread in a wide range even for GCR protons arriving at the solar system with the same energy. The distributions show a cut-off at a lower range in age or path length depending on the energy of GCRs. These cut-offs clearly come from the discreteness of occurrence of supernovae. The mean age of GeV particles obtained from the distributions is consistent with the age obtained by direct observation of radioactive secondary nuclei. The energy dependence of the B/C ratio estimated with the path length distribution reproduces reliably the energy dependence of B/C obtained by recent observations in space.

Miyake, S.; Muraishi, H.; Yanagita, S.

2015-01-01

106

OPEN PATH TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY FOR ACQUISITION OF FUGITIVE EMISSION FLUX DATA  

EPA Science Inventory

Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. EPA has developed a gorund-based optical remote sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transfor...

107

The Influence of Research Designs in Understanding the Control of Morphological Patterns on Bedload Path Lengths in gravel-bed rivers  

NASA Astrophysics Data System (ADS)

There may be a strong association between particle path length and the morphologic scale of prevailing pool- bar channel patterns in gravel-bed rivers. It has been shown that tracers introduced in a pool during channel- forming discharges have downstream path length frequency distributions that are symmetrical, with modes coinciding with pool-bar spacing. Evidence to support this hypothesis comes mostly from flume studies and there is only a limited support based on field data. For the past seven years, we have conducted field experiments in streams with gradients ranging from constricted pool and pool-bar systems to step-pools and cascades in order to link displacement distances of tracing particles to the spacing between bed features. Results showed that clast movements could not be predicted from morphological length scales. The objective of this paper is to define why the control of morphological patterns on bedload path lengths could not be seen from our dataset. We have tested hypotheses for which the limited predictive capacity of the morphological length scale results from 1) the identification of some bed units that may have been ambiguous along the bed profiles or 2) the selection of sampling parameters. The experiment was carried out in seven reaches located in Quebec and in the French Alps. The slopes ranged between 0.011 and 0.43 and the representative particle size (d50) from 42 to 110 mm. Detailed topographic maps of the bed were produced in order to describe the morphological patterns. We used passive transponders inserted into clasts to measure displacement distances. Between 100 and 450 clasts of different sizes were tagged in each reach between 2003 and 2008. The tracking was carried out at low flow using a portable antenna. In identifying morphological entities that represent no ambiguity from both field observations and long profiles, we did not observe significant evidence of a morphological control on the path lengths. The results show that even when selecting well defined pool-bar or pool-step single entities, the morphological length scale is not associated with bedload path length in six of the seven reaches. However, in one of the reaches, a step-pool channel, the clasts did tend to move downstream from one pool to the next pool. The influence of sampling strategies was tested using the size and shape of the tagged clasts, the magnitude of the flood events, the channel characteristics, and the duration of the experiments. For some transport events, the size and the shape of the tagged clasts are both correlated with individual displacement distances. These events are not observed at specific discharge values. In general, however, the correlations are not significant. Moreover, the frequency distributions of path lengths are similar whatever the size of the tagged clasts. The percentage of mobile clasts during an initial event, as well as channel and average hydrodynamic characteristics of the streams do not affect the displacement distances or the mobility of the clasts. The duration of the experiment (from the initial seeding to the last recovery of the clasts) appears to be the only sampling factor to play a role on the significance of the relations between displacement distances and channel width, slope and bed material size. The channel morphology may affect the bedload path length but, to test this effect in the field and eventually generalize the results to different channel systems, the sampling protocol must include duration rules applied to all stream channels. This study outlines the importance standardizing research protocols for long term studies of particle path lengths.

Lamarre, H.; Roy, A.

2009-05-01

108

Integrated Path Differential Absorption Lidar Optimizations Based on Pre-Analyzed Atmospheric Data for ASCENDS Mission Applications  

NASA Technical Reports Server (NTRS)

In this paper a modeling method based on data reductions is investigated which includes pre analyzed MERRA atmospheric fields for quantitative estimates of uncertainties introduced in the integrated path differential absorption methods for the sensing of various molecules including CO2. This approach represents the extension of our existing lidar modeling framework previously developed and allows effective on- and offline wavelength optimizations and weighting function analysis to minimize the interference effects such as those due to temperature sensitivity and water vapor absorption. The new simulation methodology is different from the previous implementation in that it allows analysis of atmospheric effects over annual spans and the entire Earth coverage which was achieved due to the data reduction methods employed. The effectiveness of the proposed simulation approach is demonstrated with application to the mixing ratio retrievals for the future ASCENDS mission. Independent analysis of multiple accuracy limiting factors including the temperature, water vapor interferences, and selected system parameters is further used to identify favorable spectral regions as well as wavelength combinations facilitating the reduction in total errors in the retrieved XCO2 values.

Pliutau, Denis; Prasad, Narasimha S.

2012-01-01

109

Monitoring complex trace-gas mixtures by long-path laser absorption spectrometry. [in long duration manned mission closed environments  

NASA Technical Reports Server (NTRS)

Laser-based spectrophotometric methods, which have been proposed for the detection of trace concentrations of gaseous contaminants, include Raman and passive radiometry. The paper discusses a simple long-path laser absorption method which is capable of resolving complex mixtures of closely related trace contaminants at ppm levels. A number of species were selected which are most likely to accumulate in closed environments, such as submarines or long-duration manned space flights. Absorption coefficients at CO2 laser wavelengths were measured, accurate to + 3 per cent or better, for each of these species. This data base was then used to determine the presence and concentration of the contaminants in prepared mixtures of 12 to 15 gases. Computer programs have been developed which will permit a real-time analysis of the monitored atmosphere. Minimum detectable concentrations for individual species are generally in the ppm range, and are not seriously degraded by interferences even in complex mixtures. Estimates of the dynamic range of this monitoring technique for various system configurations and comparison with other methods of analysis are discussed

Green, B. D.; Steinfeld, J. I.

1976-01-01

110

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation.  

PubMed

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters. PMID:25747062

Moix, Jeremy M; Ma, Jian; Cao, Jianshu

2015-03-01

111

Absorption  

NSDL National Science Digital Library

The process of absorption is a cellular process (microscopic). Absorption cells line the stomach and intestine walls and allow small nutrients (broken down from the food we eat) to pass through and into our blood. The process of absorption is much like a leaking balloon filled with water. The balloon is the stomach or intestine, the tiny holes are the absorption cells, and the water is nutrients leaving.

Katie Hale (CSUF; )

2002-09-26

112

Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy  

PubMed Central

In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were set up offshore, several kilometers from the coast, directly on the sea ice, which was never done before. High bromine oxide concentrations were detected frequently during sunlight hours with a characteristic daily cycle showing morning and evening maxima and a minimum at noon. The, so far, highest observed average mixing ratio in the polar boundary layer of 41 pmol/mol (equal to pptv) was detected. Only short sea ice contact is required to release high amounts of bromine. An observed linear decrease of maximum bromine oxide levels with ambient temperature during sunlight, between -24 °C and -15 °C, provides indications on the conditions required for the emission of RHS. In addition, the data indicate the presence of reactive chlorine in the Arctic boundary layer. In contrast to Antarctica, iodine oxide was not detected above a detection limit of 0.3 pmol/mol. PMID:20160121

Pöhler, Denis; Vogel, Leif; Frieß, Udo; Platt, Ulrich

2010-01-01

113

Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy.  

PubMed

In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were set up offshore, several kilometers from the coast, directly on the sea ice, which was never done before. High bromine oxide concentrations were detected frequently during sunlight hours with a characteristic daily cycle showing morning and evening maxima and a minimum at noon. The, so far, highest observed average mixing ratio in the polar boundary layer of 41 pmol/mol (equal to pptv) was detected. Only short sea ice contact is required to release high amounts of bromine. An observed linear decrease of maximum bromine oxide levels with ambient temperature during sunlight, between -24 degrees C and -15 degrees C, provides indications on the conditions required for the emission of RHS. In addition, the data indicate the presence of reactive chlorine in the Arctic boundary layer. In contrast to Antarctica, iodine oxide was not detected above a detection limit of 0.3 pmol/mol. PMID:20160121

Pöhler, Denis; Vogel, Leif; Friess, Udo; Platt, Ulrich

2010-04-13

114

Mapping of methane spatial distribution around biogas plant with an open-path tunable diode absorption spectroscopy scanning system  

NASA Astrophysics Data System (ADS)

An open-path tunable diode laser absorption spectroscopy (OP-TDLAS) detector was applied to detect the methane emission from a biogas plant in a dairy farm. Two OP-TDLAS scanning systems were built according to maximum likelihood with expectation minimization (MLEM) and smooth basis function minimization (SBFM) algorithms to reconstruct the two-dimensional (2-D) distribution maps. Six reconstruction maps with the resolution of 30×80 were obtained by the MLEM algorithm with "grid translation method" and three reconstruction maps were obtained by the SBFM algorithm with 2-D Gaussian model. The maximum mixing ratio in the first result was between 0.85 and 1.30 ppm, while it was between 1.14 and 1.30 ppm in the second result. The average mixing ratio in the first result was between 0.54 and 0.49 ppm, and between 0.56 and 0.65 ppm in the second result. The reconstruction results validated that the two algorithms could effectively reflect the methane mixing ratio distribution within the target area. However, with the more simple optical rays and less equipment requirements, the OP-TDLAS scanning system based on SBFM algorithm provides a useful monitoring tool of methane emissions in agricultural production.

Zhang, Shirui; Wang, Jihua; Dong, Daming; Zheng, Wengang; Zhao, Xiande

2013-02-01

115

Development of a new Long Path Absorption Photometer (LOPAP) instrument for the sensitive detection of NO2 in the atmosphere  

NASA Astrophysics Data System (ADS)

A compact and simple instrument for the sensitive detection of NO2 in the atmosphere has been developed. NO2 is sampled in a stripping coil by a selective chemical reaction, converted into a highly absorbing dye, which is detected by long path absorption in a liquid core waveguide. Several interferences were quantified in the laboratory which so far can all be neglected. The significant interferences against HONO and O3 were suppressed by using an upstream HONO/O3-scrubber. The instrument has a detection limit of 2 pptv, an accuracy of 10 % and a precision of 0.5 % for 3 min time resolution. Thus, the new NO2-LOPAP technique is more sensitive than known commercial NO2 instruments. The new analyzer is much simpler to apply than other highly sensitive and selective NO2 methods, e.g. LIF or REMPI methods. The new instrument allows an absolute calibration that can be easily performed with liquid nitrite standards, which is a significant advantage compared with other NO2 measurement techniques for which NO2 calibration gas mixtures are typically necessary. The new instrument has been validated against the chemiluminescence technique during an urban field campaign and against the FTIR technique in a smog chamber under complex photosmog conditions. The data sets exhibit high correlation and excellent agreement.

Villena, G.; Bejan, I.; Kurtenbach, R.; Wiesen, P.; Kleffmann, J.

2011-08-01

116

Development of a new Long Path Absorption Photometer (LOPAP) instrument for the sensitive detection of NO2 in the atmosphere  

NASA Astrophysics Data System (ADS)

A compact and simple instrument for the sensitive detection of NO2 in the atmosphere has been developed. NO2 is sampled in a stripping coil by a selective chemical reaction, converted into a highly absorbing dye, which is detected by long path absorption in a liquid core waveguide. Several interferences were quantified in the laboratory which so far can all be neglected. The significant interferences against HONO and O3 were suppressed by using an upstream HONO/O3-scrubber. The instrument has a detection limit of 2 pptv, an accuracy of 10% and a precision of 0.5% for 3 min time resolution. Thus, the new NO2-LOPAP technique is more sensitive than known commercial NO2 instruments. The new analyzer is much simpler to apply than other highly sensitive and selective NO2 methods, e.g. LIF or REMPI methods. The new instrument allows an absolute calibration that can be easily performed with liquid nitrite standards, which is a significant advantage compared with other NO2 measurement techniques for which NO2 calibration gas mixtures are typically necessary. The new instrument has been validated against the chemiluminescence technique during an urban field campaign and against the FTIR technique in a smog chamber under complex photosmog conditions. The data sets exhibit high correlation and excellent agreement.

Villena, G.; Bejan, I.; Kurtenbach, R.; Wiesen, P.; Kleffmann, J.

2011-03-01

117

A method to measure the total scattering cross section and effective beam gas path length in a low-vacuum SEM.  

PubMed

A method is presented to determine the total scattering cross section of imaging gases used in low-vacuum scanning electron microscopy or environmental scanning electron microscopy. Experimental results are presented for water vapor, nitrogen gas and ambient air for primary beam electron energies between 5 and 30 keV. The measured results are compared and discussed with calculated values. This method allows the effective beam gas path length (BGPL) to be determined. The variations of the effective BGPL with varying chamber pressure are presented. PMID:19504539

Rattenberger, J; Wagner, J; Schröttner, H; Mitsche, S; Zankel, A

2009-01-01

118

Stopping powers of Ti for protons from 0.2 to 13.5 MeV: Correction for the actual path length due to multiple scattering  

NASA Astrophysics Data System (ADS)

Stopping powers of Ti were measured for protons from 0.2 to 13.5 MeV. The uncertainty of the present results was estimated to be ±0.40%. Although the present results agreed well with our previous result measured at 6.5 MeV, they were 1-2% smaller than those measured by Andersen et al. and 0.5-4% smaller than compilation values of ICRU Report 49. Analyzing the present results with the Bethe-Bloch formula with corrections, we could obtain the information on the lowest energy; beyond that we could not apply the formula to describe stopping powers. In order to obtain precise experimental values at low energies, we paid special attention to the effect of the enlargement of an actual path length over a target thickness. We measured angular distributions due to multiple scattering for 26 kinds of target thickness and incident energy combinations. In these cases energy losses of protons ranged from 1.3 to 62% of their initial energies. We found that angular distributions were excellently reproduced by both Molière's theory and the theory of Sigmund and Winterbon. Therefore, we could conclude that these theories gave a reliable evaluation of the correction for the actual path length.

Sakamoto, N.; Ogawa, H.; Tsuchida, H.

2000-04-01

119

Earth-satellite-Earth laser long-path absorption experiment using the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS)  

Microsoft Academic Search

This paper reports the results of the laser long-path absorption experiments carried out with the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS). The RIS is a 0.5 m diameter single-element hollow retroreflector with a unique optical design which uses a curved mirror surface to correct velocity aberrations caused by the satellite movement. In the RIS experiments

Nobuo Sugimoto; Nobuhiko Koga; Ichiro Matsui; Yasuhiro Sasano; Atsushi Minato; Kenichi Ozawa; Yasunori Saito; Akio Nomura; Tetsuo Aoki; Toshikazu Itabe; Hiroo Kunimori; Isao Murata; Hiroshi Fukunishi

1999-01-01

120

Laser transmitter/receiver system for earth-satellite-earth long-path absorption measurements of atmospheric trace species using the retroreflector in space  

NASA Astrophysics Data System (ADS)

A laser transmitter/receiver system using a retroreflector in space (RIS) to experiment with earth-satellite-earth laser long-path absorption measurements of atmospheric trace species is described. The system employs two single-longitudinal-mode pulsed carbon-dioxide lasers to measure the atmospheric spectrum and a second-harmonic Nd:YAG laser for active satellite tracking using the image of the RIS reflection. Details of the laser system and the initial experiment are reported.

Ozawa, Kenichi; Koga, Nobuhiko; Sugimoto, Nubuo; Saito, Yasunori; Nomura, Akio; Aoki, Tetsuo; Itabe, Toshikazu; Kunimori, Hiroo

1997-12-01

121

Spatiotemporal structure of a laser beam at a path length of 144??km: comparative analysis of spatial and temporal spectra.  

PubMed

We present an analysis of spatial and temporal spectra of the observations of scintillations in a laser beam (532 nm, ?200??mW power) traveling along a 144 km path at an altitude of 2-2.4 km above sea level, just above the atmospheric boundary layer, between the islands of La Palma and Tenerife. The observations were performed during nighttime on July 18 and 21, 2011, by means of a telescope with an aperture diameter of 1 m. Strong scintillations were observed. We compared the temporal and spatial spectra of the scintillations. For the temporal spectra, we performed the correction for the aliasing effect due to the low frame rate. The 2D spatial spectra of the scintillations in the observation plane were found to be close to isotropic. This allowed for transforming them into 1D spectra. We found a good agreement between the temporal and 1D spatial spectra. This corroborates the applicability of the Taylor hypothesis of frozen turbulence for finite-size laser beams and strong scintillations. PMID:24787588

Gurvich, Alexandre S; Gorbunov, Michael E; Fedorova, Olga V; Fortus, Marina I; Kirchengast, Gottfried; Proschek, Veronika; Tereszchuk, Keith A

2014-04-20

122

Determination of the lactose content of fluid milk by spectrophotometric enzymatic analysis using weight additions and path length adjustment: collaborative study.  

PubMed

The objective of this collaborative study was to determine the method performance characteristics of a spectrophotometric enzymatic assay for measuring the lactose content of fluid milk. The principle behind the method is similar to that of AOAC Method 984.15 but with significant modifications and added quality control. Additionally, lactose concentration is expressed on a weight/weight (wt/wt) rather than a weight/volume (wt/vol) basis. The principle of the method is the hydrolysis of lactose to D-glucose and D-galactose by beta-galactosidase, followed by the oxidation of beta-D-galactose by nicotinamide adenine dinucleotide (NAD+) in the presence of beta-galactose dehydrogenase. The reaction is catalyzed by the addition of aldose-l-epimerase, which accelerates the mutarotation of alphha-D-galactose to beta-D-galactose. The amount of reduced nicotinamide adenine dinucleotide (NADH) formed is measured at 340 nm and is proportional to the amount of lactose present. Important aspects of the assay include preparing the assay solution by weight (rather than volume), mixing the contents of the spectrophotometric cuvette without losing solution, inclusion of aldose-l-epimerase, specifying spectrophotometer characteristics, and accounting for the optical path length of the spectrophotometric cuvettes. In the collaborative study, 11 laboratories tested one lactose standard and 8 pairs of blind replicate raw, processed, and formulated milks with an anhydrous lactose content between 3.0-7.2%. Statistical performance, in units of g/100 g anhydrous lactose, for the milk materials within the applicability of the method was as follows: mean = 4.4040, Sr = 0.0130, SR = 0.0250, RSDr = 0.29%, RSDR = 0.57%, r = 0.0364, and R = 0.0700. Standard and marginal recoveries were 98.66 and 99.53%, respectively. Method performance represented a significant improvement over what would be achieved if path length was not accounted for or the assay was done volumetrically. The Study Directors recommend that the method for determination of the lactose content of fluid milk by the spectrophotometric enzymatic method using weight additions and path length adjustment be adopted Official First Action. PMID:17373452

Lynch, Joanna M; Barbano, David M; Fleming, J Richard

2007-01-01

123

Inhibition of Ileal Water Absorption by Intraluminal Fatty Acids INFLUENCE OF CHAIN LENGTH, HYDROXYLATION, AND CONJUGATION OF FATTY ACIDS  

PubMed Central

The influence of fatty acids on ileal absorption of water, electrolytes, glucose, and taurocholate was examined in Thirty-Vella fistulas in five mongrel dogs. Fatty acid absorption also was measured. Segments of terminal ileum were perfused at steady state with isotonic electrolyte solutions containing 11.2 mM glucose, 4.5 mM taurocholate, and 0.1-5.0 mM fatty acid. Three C18 fatty acids, oleic acid, 10(9)-hydroxystearic acid, and ricinoleic acid, completely inhibited water absorption at 5 mM. Sodium, chloride, and potassium absorptions were inhibited in parallel with absorption of water. Differences between the potencies of C18 fatty acids were apparent when lesser concentrations were perfused. Dodecanoic and decanoic acids were as effective as C18 fatty acids at 5 mM but octanoic and hexanoic acids were ineffective. The polar group of C18 fatty acids was modified by conjugating oleic and ricinoleic acids with taurine. When these compounds and a substituted C18 fatty acid, p-n-decylbenzenesulfonate, were perfused, water absorption was also inhibited. Short-chain fatty acids (C3 and C4) and their hydroxylated derivatives were ineffective at 5 mM. When water absorption was inhibited, absorption of glucose and taurocholate was decreased. We speculate that the phenomenon of inhibition of water and electrolyte absorption by fatty acids may be relevant to steatorrhea and diarrhea in man. Images PMID:4808636

Ammon, Helmut V.; Phillips, Sidney F.

1974-01-01

124

Absorption  

NSDL National Science Digital Library

This activity can be used to allow students to explore the concept of absorption using a variety of materials. Extensions include exploring how Native Americans used absorbtion in a number of ways. This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÂ?s 1998 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

Katherine M Knudson (Polson Middle School)

1998-04-01

125

Adjusting the tasseled cap brightness and greenness factors for atmospheric path radiance and absorption on a pixel by pixel basis  

NASA Technical Reports Server (NTRS)

A radiative transfer model was used to convert ground measured reflectances into the radiance at the top of the atmosphere, for several levels of atmospheric path radiance. The radiance in MSS7 (0.8 to 1.1 m) was multiplied by the transmission fraction for atmospheres having different levels of precipitable water. The radiance values were converted to simulated LANDSAT digital counts for four path radiance levels and four levels of precipitable water. These values were used to calculate the Kauth-Thomas brightness, greenness, yellowness, and nonsuch factors. Brightness was affected by surface conditions and path radiance. Greenness was affected by surface conditions, path radiance, and precipitable water. Yellowness was affected by path radiance and nonsuch by precipitable water, and both factors changed only slightly with surface conditions. Yellowness and nonsuch were used to adjust brightness and greenness to produce factors that were affected only by surface conditions such as soils and vegetation, and not by path radiance and precipitable water.

Jackson, R. D.; Slater, P. N.; Pinter, P. J. (principal investigators)

1982-01-01

126

Sensitivity of Pion versus Parton-Jet Nuclear Modification Factors to the Path-Length Dependence of Jet-Energy Loss at RHIC and LHC  

E-print Network

We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a parton-jet nuclear modification factor at RHIC and LHC. We contrast predictions based on a linear pQCD and a highly non-linear hybrid-AdS holographic model of jet-energy loss. We find that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. We conclude that while reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superimposition with NLO and medium effects. Hence, a detailed description of the underlying physics requ...

Betz, Barbara

2015-01-01

127

Improved extended-x-ray-absorption fine-structure (EXAFS) studies applied to the investigation of Cu-O, Cu-N, and Cu-Br bond lengths  

Microsoft Academic Search

Extended-x-ray-absorption fine-structure spectra in the region of the Cu K edge are presented for Cu, CuO, Cu2O, CuSO4, CuSO4.5H2O, Cu(OH)2, Cu(NO3).3H2O, [Cu(NH3)4]2+, and CuBr2. By the usual Fourier-analysis method, bond lengths for Cu-O, Cu-N, and Cu-Br are determined. Further, a back-transformation into real space is used which allows us to check the consistency of the evaluation for the whole energy

G. Martens; P. Rabe; N. Schwentner; A. Werner

1978-01-01

128

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries in ?-Fe  

NASA Astrophysics Data System (ADS)

The energetics and length scales associated with the interaction between point defects (vacancies and self-interstitial atoms) and grain boundaries in bcc Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained ?170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15 Å of the boundary. The present results provide detailed information about the interaction energies of vacancies and self-interstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low- and high-angle grain boundaries were effective sinks for point defects, with a few low-? grain boundaries (e.g., the ?3{112} twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and ? designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have ?80% more grain boundary sites per area and ?300% greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6-7 Å versus 10-11 Å for vacancies and interstitials, respectively).

Tschopp, M. A.; Solanki, K. N.; Gao, F.; Sun, X.; Khaleel, M. A.; Horstemeyer, M. F.

2012-02-01

129

Toward stand-off open-path measurements of NO and NO(2) in the sub-parts per million meter range using quantum cascade lasers (QCLs) in the intra-pulse absorption mode.  

PubMed

Two thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers operated in pulsed mode have been used for the quasi-simultaneous determination of NO and NO2 in the sub-parts per million meter (sub-ppm-m) range. Using a beam splitter, the beams of the two lasers were combined and sent to a retro-reflector. The returned light was recorded with a thermoelectrically cooled mercury cadmium telluride detector with a rise time of 4 ns. Alternate operation of the lasers with pulse lengths of 300 ns and a repetition rate of 66 kHz allowed quasi-simultaneous measurements. During each pulse the laser temperature increased, causing a thermal chirp of the laser line of up to 1.3 cm(-1). These laser chirps were sufficient to scan rotational bands of NO centered at 1902 cm(-1) and NO2 located at 1632 cm(-1). In that way an absorption spectrum could be recorded from a single laser pulse. Currently achieved limits of detection are 600 parts per billion meter (ppb-m) for NO and 260 ppb-m for NO2 using signal averaging over 1 min. This work presents the first steps toward a portable stand-off, open-path instrument that uses thermoelectrically cooled detector and lasers. PMID:24359649

Reidl-Leuthner, Christoph; Lendl, Bernhard

2013-12-01

130

JOURNAL DE PHYSIQUE Colloque C4, supplkment au no 10, Tome 32, Octobre 1971, page C4-154 ABSORPTION OF 0,, CO, AND CS, ; FLUORESCENCE PROM CS, ;  

E-print Network

, with photoelectric detection. The monochromator itself was used as an absorption cell whose path length was 618 cm que celles de la serie Lyman de l'hydrogkne atomique, ainsi que des sections efficaces d

Paris-Sud XI, Université de

131

Calculation of exit dose for conformal and dynamically-wedged fields, based on water-equivalent path length measured with an amorphous silicon electronic portal imaging device.  

PubMed

In this study, we use the quadratic calibration method (QCM), in which an EPID image is converted into a matrix of equivalent path lengths (EPLs) and, therefore, exit doses, so as to model doses in conformal and enhanced dynamic wedge (EDW) fields. The QCM involves acquiring series of EPID images at a reference field size for different thicknesses of homogeneous solid water blocks. From these, a set of coefficients is established that is used to compute the EPL of any other irradiated material. To determine the EPL, the irradiated area must be known in order to establish the appropriate scatter correction. A method was devised for the automatic calculation of areas from the EPID image that facilitated the calculation of EPL for any field and exit dose. For EDW fields, the fitting coefficients were modified by utilizing the linac manufacturer's golden segmented treatment tables (GSTT) methodology and MU fraction model. The nonlinear response of the EPL with lower monitor units (MUs) was investigated and slight modification of the algorithm performed to account for this. The method permits 2D dose distributions at the exit of phantom or patient to be generated by relating the EPL with an appropriate depth dose table. The results indicate that the inclusion of MU correction improved the EPL determination. The irradiated field areas can be accurately determined from EPID images to within ± 1% uncertainty. Cross-plane profiles and 2D dose distributions of EPID predicted doses were compared with those calculated with the Eclipse treatment planning system (TPS) and those measured directly with MapCHECK 2 device. Comparison of the 2D EPID dose maps to those from TPS and MapCHECK shows that more than 90% of all points passed the gamma index acceptance criteria of 3% dose difference and 3 mm distance to agreement (DTA), for both conformal and EDW study cases. We conclude that the EPID QCM is an accurate and convenient method for in vivo dosimetry and may, therefore, complement existing techniques. PMID:21844855

Kavuma, Awusi; Glegg, Martin; Metwaly, Mohamed; Currie, Garry; Elliott, Alex

2011-01-01

132

A comprehensive study on energy absorption and exposure buildup factors for some essential amino acids, fatty acids and carbohydrates in the energy range 0.015–15 MeV up to 40 mean free path  

Microsoft Academic Search

The gamma ray energy absorption (EABF) and exposure buildup factors (EBF) have been calculated for some essential amino acids, fatty acids and carbohydrates in the energy region 0.015–15MeV up to a penetration depth of 40mfp (mean free path). The five parameter geometric progression (G-P) fitting approximation has been used to calculate both EABF and EBF. Variations of EABF and EBF

Murat Kurudirek; Yüksel Özdemir

2011-01-01

133

EXPERIMENTAL STUDY OF THE ABSORPTION IN DISTILLED WATER, ARTIFICIAL SEA WATER, AND HEAVY WATER IN THE VISIBLE REGION OF THE SPECTRUM  

Microsoft Academic Search

The absorption of light in distilled water, artificial sea water, and ; heavy water was measured in the visible region. A Nielsen spectrometer with ; glass optics was used with a tungsten source and photomultiplier detector. Path ; lengths were 60.0 and 132.0 cm. The absorption in distilled and artificiai sea ; water differs little; maxima below 745 m mu

SERAPHIN A. SULLIVAN

1963-01-01

134

Characterizing a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of atmospheric ammonia  

Microsoft Academic Search

A compact, fast-response Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of ammonia (NH3) has been evaluated under both laboratory and field conditions. Absorption of radiation from a pulsed, thermoelectrically cooled QC laser occurs at reduced pressure in a 0.5 L multiple pass absorption cell with an effective path length of 76 m. Detection is achieved using

R. A. Ellis; J. G. Murphy; E. Pattey; R. van Haarlem; J. M. O'Brien; S. C. Herndon

2010-01-01

135

On-chip cavity-enhanced absorption spectroscopy using a white light-emitting diode and polymer mirrors.  

PubMed

We have developed a disposable microfluidic chip with integrated cavity mirrors comprised of two pieces of 3M Vikuiti™ enhanced specular reflector II (ESRII) film, for performing cavity-enhanced absorption spectroscopy with a white light-emitting diode (LED). Compared to measurements made with a chip without cavity mirrors, the absorption path length is enhanced by a maximum factor of 28 at 544 nm, and the sensitivity is enhanced by approximately 5 times, enabling micromolar range detection limits to be achieved in an optical path length of only 50 ?m. PMID:25494304

Rushworth, Cathy M; Jones, Gareth; Fischlechner, Martin; Walton, Emma; Morgan, Hywel

2015-02-01

136

Design parameters for enhanced photon absorption in vertically aligned silicon nanowire arrays  

NASA Astrophysics Data System (ADS)

Superior photon absorption in ordered nanowire arrays has been demonstrated recently. However, systematic studies are still missing to explore the limits of their implementation as functional photonic devices. With emphasis on silicon nanowires, we investigated the effects of nanowire diameter, length, morphology, and pitch on the photon absorption within the visible solar spectrum based on simulations. Our results reveal that these parameters are crucial but disclose a path to improve the absorbance drastically.

Jäger, Stefan T.; Strehle, Steffen

2014-09-01

137

Global sampling of the photochemical reaction paths of bromoform by ultrafast deep-UV through near-IR transient absorption and ab initio multiconfigurational calculations  

NASA Astrophysics Data System (ADS)

Ultrafast deep-ultraviolet through near infrared (210-950 nm) transient absorption spectroscopy complemented by ab initio multiconfigurational calculations offers a global description of the photochemical reaction pathways of bromoform following 255-nm excitation in methylcyclohexane and acetonitrile solutions. Photoexcitation of CHBr3 leads to the ground-state iso-CHBr3 product in a large quantum yield (˜35%), formed through two different mechanisms: concerted excited-state isomerization and cage-induced isomerization through the recombination of the nascent radical pair. These two processes take place on different time scales of tens of femtoseconds and several picoseconds, respectively. The novel ultrafast direct isomerization pathway proposed herein is consistent with the occurrence of a conical intersection between the first excited singlet state of CHBr3 and the ground electronic state of iso-CHBr3. Complete active space self-consistent field calculations characterize this singularity in the vicinity of a second order saddle point on the ground state which connects the two isomer forms. For cage-induced isomerization, both the formation of the nascent radical pair and its subsequent collapse into ground-state iso-CHBr3 are directly monitored through the deep-ultraviolet absorption signatures of the radical species. In both mechanisms, the optically active (i.e., those with largest Franck-Condon factors) C-Br-Br bending and Br-Br stretching modes of ground-state iso-CHBr3 have the largest projection on the reaction coordinate, enabling us to trace the structural changes accompanying vibrational relaxation of the non-equilibrated isomers through transient absorption dynamics. The iso-CHBr3 photoproduct is stable in methylcyclohexane, but undergoes either facile thermal isomerization to the parent CHBr3 structure through a cyclic transition state stabilized by the polar acetonitrile medium (˜300-ps lifetime), and hydrolysis in the presence of water.

Pal, S. K.; Mereshchenko, A. S.; Butaeva, E. V.; El-Khoury, P. Z.; Tarnovsky, A. N.

2013-03-01

138

Global sampling of the photochemical reaction paths of bromoform by ultrafast deep-UV through near-IR transient absorption and ab initio multiconfigurational calculations.  

PubMed

Ultrafast deep-ultraviolet through near infrared (210-950 nm) transient absorption spectroscopy complemented by ab initio multiconfigurational calculations offers a global description of the photochemical reaction pathways of bromoform following 255-nm excitation in methylcyclohexane and acetonitrile solutions. Photoexcitation of CHBr3 leads to the ground-state iso-CHBr3 product in a large quantum yield (?35%), formed through two different mechanisms: concerted excited-state isomerization and cage-induced isomerization through the recombination of the nascent radical pair. These two processes take place on different time scales of tens of femtoseconds and several picoseconds, respectively. The novel ultrafast direct isomerization pathway proposed herein is consistent with the occurrence of a conical intersection between the first excited singlet state of CHBr3 and the ground electronic state of iso-CHBr3. Complete active space self-consistent field calculations characterize this singularity in the vicinity of a second order saddle point on the ground state which connects the two isomer forms. For cage-induced isomerization, both the formation of the nascent radical pair and its subsequent collapse into ground-state iso-CHBr3 are directly monitored through the deep-ultraviolet absorption signatures of the radical species. In both mechanisms, the optically active (i.e., those with largest Franck-Condon factors) C-Br-Br bending and Br-Br stretching modes of ground-state iso-CHBr3 have the largest projection on the reaction coordinate, enabling us to trace the structural changes accompanying vibrational relaxation of the non-equilibrated isomers through transient absorption dynamics. The iso-CHBr3 photoproduct is stable in methylcyclohexane, but undergoes either facile thermal isomerization to the parent CHBr3 structure through a cyclic transition state stabilized by the polar acetonitrile medium (?300-ps lifetime), and hydrolysis in the presence of water. PMID:23556730

Pal, S K; Mereshchenko, A S; Butaeva, E V; El-Khoury, P Z; Tarnovsky, A N

2013-03-28

139

Parsimonious path openings and closings.  

PubMed

Path openings and closings are morphological tools used to preserve long, thin, and tortuous structures in gray level images. They explore all paths from a defined class, and filter them with a length criterion. However, most paths are redundant, making the process generally slow. Parsimonious path openings and closings are introduced in this paper to solve this problem. These operators only consider a subset of the paths considered by classical path openings, thus achieving a substantial speed-up, while obtaining similar results. In addition, a recently introduced 1D opening algorithm is applied along each selected path. Its complexity is linear with respect to the number of pixels, independent of the size of the opening. Furthermore, it is fast for any input data accuracy (integer or floating point) and works in stream. Parsimonious path openings are also extended to incomplete paths, i.e., paths containing gaps. Noise-corrupted paths can thus be processed with the same approach and complexity. These parsimonious operators achieve a several orders of magnitude speed-up. Examples are shown for incomplete path openings, where computing times are brought from minutes to tens of milliseconds, while obtaining similar results. PMID:24569442

Morard, Vincent; Dokladal, Petr; Decenciere, Etienne

2014-04-01

140

The absorption of ultrasonic waves in liquids  

E-print Network

~ PIOt Ot LOV~ A?/Ao Va, SOund Path Ianna;th ~ Aaetane. 29 III, Plot of Lo~ A?/Ao va, Sound Path Length All@1 IV~ Aloohol ~ o ~, i ~ ~ ~ ~ e ~ ~ ~ ~ ~ s s ~ ~ ~ ~ ~ ~ e e ~ ~ ~ ~ s + ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ 30 Plot ot Lo@+ A /A va, Sound Path... Length 'arbon 'Totgsohlol'Moo o we ~ o ~ ~ o ~ a ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ 131 Vo Plot of Log+A?/Ave, Sound Path Length' tekel &t &lox' ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ s ~ ~ ~ ~ o y 0 ~ ~ ~ e ~ ~ o ~ ~ ~ ~ e...

Hudson, Paul A

1951-01-01

141

Near-infrared optical-absorption behavior in high-beta nonlinear optical chromophore-polymer guest-host materials. II. Dye spacer length effects in an amorphous polycarbonate copolymer host.  

PubMed

In the second of a three-part series, spectral absorption behavior of nonlinear optical (NLO) dyes incorporated into amorphous polycarbonate, comprised of a homologous series of dialkyl spacer groups extending from the midsection of the dye molecule, is characterized by UV-Vis and photothermal deflection spectroscopy. The dyes are structural analogs of the NLO dye FTC [2-(3-cyano-4-{2-[5-(2-{4-[ethyl-(2-methoxyethyl)amino]phenyl}vinyl)-3,4-diethylthiophen-2-yl]vinyl}-5,5-dimethyl-5H-furan-2-ylidene)malononitrile]. Previous Monte Carlo calculations [B. H. Robinson and L. R. Dalton, J. Phys. Chem. A 104, 4785 (2000)] predict a strong dependence of the macroscopic nonlinear optical susceptibility on the chromophore waist: length aspect ratio in electric-field-poled films arising from interactions between chromophores. It is expected that these interactions will play a role in the absorption characteristics of unpoled films, as well. The spacer groups range in length from diethyl to dihexyl, and each dye is studied over a wide range of concentrations. Among the four dyes studied, a universal dependence of near-IR loss on inhomogeneous broadening of the dye main absorption peak is found. The inhomogeneous width and its concentration dependence are seen to vary with spacer length in a manner characteristic of the near-IR loss-concentration slope at transmission wavelengths of 1.06 and 1.3 mum, but not at 1.55 mum. The lower wavelength loss behavior is assigned to purely Gaussian broadening, and is described by classical mixing thermodynamic quantities based on the Marcus theory of inhomogeneous broadening [R. A. Marcus, J. Chem. Phys. 43, 1261 (1965)], modeled as a convolution of dye-dye dipole broadening and dye-polymer van der Waals broadening. The Gaussian dipole interactions follow a Loring dipole-broadening description [R. F. Loring, J. Phys. Chem. 94, 513 (1990)] dominated by the excited-state dipole moment, and have a correlated homogeneous broadening contribution. The long-wavelength loss behavior has a non-Gaussian dye-dye dipole contribution which follows Kador's broadening analysis [L. Kador, J. Chem. Phys. 95, 5574 (1991)], with a net broadening described by a convolution of this term with a Gaussian van der Waals interaction given by Obata et al. [M. Obata, S. Machida, and K. Horie, J. Polym. Sci. B 37, 2173 (1999)], with each term governed by the dye spacer length. A minimum in broadening and loss-concentration slope at a spacer length of four carbons per alkyl at all wavelengths has important consequences for practical waveguide devices, and is of higher aspect ratio than the spherical limit shown by Robinson and Dalton to minimize dipole interactions under a poling field. PMID:16008487

Barto, Richard R; Frank, Curtis W; Bedworth, Peter V; Ermer, Susan; Taylor, Rebecca E

2005-06-15

142

Noise estimation technique to reduce the effects of 1/f noise in Open Path Tunable Diode Laser Absorption Spectrometry (OP-TDLAS)  

NASA Astrophysics Data System (ADS)

Many techniques using high frequency modulation have been proposed to reduce the effects of 1/f noise in tunable diode-laser absorption spectroscopy (TDLAS). The instruments and devices used by these techniques are not suitable for space applications that require small, low mass and low power instrumentation. A new noise estimation technique has already been proposed and validated for two lasers to reduce the effect of 1/f noise at lower frequencies. This paper extends the noise estimation technique and applies it using one distribution feedback (DFB) laser diode. In this method a DFB laser diode is excited at two slightly different frequencies, giving two different harmonics that can be used to estimate the total noise in the measurement. Simulations and experimental results on ammonia gas validate that the 1/f noise is effectively reduced by the noise estimation technique using one laser. Outdoor experimental results indicate that the effect of 1/f noise is reduced to more than 1/4 its normal value.

Mohammad, Israa L.; Anderson, Gary T.; Chen, Youhua

2014-06-01

143

Standard Length versus Total Length  

Microsoft Academic Search

In an effort to determine the length measurement most representative of the bulk of the fish, the standard length and the total length were each compared with the weight of the fish. This comparison was made for four species of game fish, yellow perch (Perca flavescens), wall-eyed pike (Stizostedion v. vitreum), rock bass (Ambloplites rupestris), and lake trout (Cristivomer n.

William F. Royce

1942-01-01

144

Time optimal paths for high speed maneuvering  

SciTech Connect

Recent theoretical results have completely solved the problem of determining the minimum length path for a vehicle with a minimum turning radius moving from an initial configuration to a final configuration. Time optimal paths for a constant speed vehicle are a subset of the minimum length paths. This paper uses the Pontryagin maximum principle to find time optimal paths for a constant speed vehicle. The time optimal paths consist of sequences of axes of circles and straight lines. The maximum principle introduces concepts (dual variables, bang-bang solutions, singular solutions, and transversality conditions) that provide important insight into the nature of the time optimal paths. We explore the properties of the optimal paths and present some experimental results for a mobile robot following an optimal path.

Reister, D.B.; Lenhart, S.M.

1993-01-01

145

Counting paths in digraphs  

SciTech Connect

Say a digraph is k-free if it has no directed cycles of length at most k, for k {element_of} Z{sup +}. Thomasse conjectured that the number of induced 3-vertex directed paths in a simple 2-free digraph on n vertices is at most (n-1)n(n+1)/15. We present an unpublished result of Bondy proving there are at most 2n{sup 3}/25 such paths, and prove that for the class of circular interval digraphs, an upper bound of n{sup 3}/16 holds. We also study the problem of bounding the number of (non-induced) 4-vertex paths in 3-free digraphs. We show an upper bound of 4n{sup 4}/75 using Bondy's result for Thomasse's conjecture.

Sullivan, Blair D [ORNL; Seymour, Dr. Paul Douglas [Princeton University

2010-01-01

146

Fiber laser intracavity absorption spectroscopy for in situ multicomponent gas analysis in the atmosphere and combustion environments  

NASA Astrophysics Data System (ADS)

Intracavity absorption spectroscopy with a broadband Er3+-doped fiber laser is applied for the measurements of several molecular species revealing quantitative information about the gas concentration, temperature and chemical reactions in flames. The spectral range of measurements extends from 6200 cm-1 to 6550 cm-1 with the proper choice of the fiber length and by moving an intracavity lens. With a pulsed laser applied in this experiment, the sensitivity to absorption corresponds to an effective absorption path length of 3 km assuming the cavity is completely filled with the sample. For a cw laser, the effective absorption path length is estimated to be 50 km. Absorption spectra of various molecules such as CO2, CO, H2O, H2S, C2H2 and OH were recorded separately in the cell and/or in low-pressure methane and propane flames. The presented measurements demonstrate simultaneous in situ detection of three molecular products of chemical reactions at different flame locations. Variation of the relative strengths of OH absorption lines with the temperature enables the estimation of the local flame temperature. The sensitivity of this laser does not depend on the broadband cavity losses and it can be used for in situ measurements of absorption spectra in hostile environments such as contaminated samples, flames or combustion engines. The presented technique can be applied for various diagnostic purposes, such as in environmental, combustion and plasma research, in medicine and in the determination of stable isotope ratios.

Löhden, B.; Kuznetsova, S.; Sengstock, K.; Baev, V. M.; Goldman, A.; Cheskis, S.; Pálsdóttir, B.

2011-02-01

147

Ladybug Lengths  

NSDL National Science Digital Library

This lesson introduces students to the measurable attribute of length and provides practice in measuring length using non-standard units. The lesson is launched using the story Ladybug on the Move by Richard Fowler. Lesson objectives, teaching ideas, and handouts are included.

2012-01-01

148

Near-infrared absorption spectra of (O-16)3 and (O-18)3 - Adiabatic energy of the 1A2 state?  

Microsoft Academic Search

The band positions and isotope shifts for the weak vibronic bands of O3 near 1 micron are determined experimentally using a low-resolution dual-beam absorption spectrometer with a 0.2-m holographic-grating monochromator and identical absorption chambers of volume about 600 cu cm and optical path length 46 cm. The experimental setup and procedures and the signal-processing methods applied are described, and the

S. M. Anderson; J. Morton; K. Mauersberger

1990-01-01

149

A comprehensive study on energy absorption and exposure buildup factors for some essential amino acids, fatty acids and carbohydrates in the energy range 0.015-15 MeV up to 40 mean free path  

NASA Astrophysics Data System (ADS)

The gamma ray energy absorption ( EABF) and exposure buildup factors ( EBF) have been calculated for some essential amino acids, fatty acids and carbohydrates in the energy region 0.015-15 MeV up to a penetration depth of 40 mfp (mean free path). The five parameter geometric progression (G-P) fitting approximation has been used to calculate both EABF and EBF. Variations of EABF and EBF with incident photon energy, penetration depth and weight fraction of elements have been studied. While the significant variations in EABF and EBF for amino acids and fatty acids have been observed at the intermediate energy region where Compton scattering is the main photon interaction process, the values of EABF and EBF appear to be almost the same for all carbohydrates in the continuous energy region. It has been observed that the fatty acids have the largest EABF and EBF at 0.08 and 0.1 MeV, respectively, whereas the maximum values of EABF and EBF have been observed for aminoacids and carbohydrates at 0.1 MeV. At the fixed energy of 1.5 MeV, the variation of EABF with penetration depth appears to be independent of the variations in chemical composition of the amino acids, fatty acids and carbohydrates. Significant variations were also observed between EABF and EBF which may be due to the variations in chemical composition of the given materials.

Kurudirek, Murat; Özdemir, Yüksel

2011-01-01

150

Inbound traffic engineering for multihomed ASs using AS path prepending  

Microsoft Academic Search

This article considers the AS path prepending approach to engineer inbound traffic for multihomed ASs. The AS path prepending approach artificially inflates the length of the AS path attribute on one of the links in hopes of diverting some of the traffic to other links. Unlike the current practice that determines the prepending length in a trial-and-error way, we propose

Rocky K. C. Chang; M. Lo

2005-01-01

151

Snell's law and light traveling along the shortest path  

Microsoft Academic Search

the problem to be analyzed follows: Given a starting point s, an ending point t and a set of n Weighted Faces (or regions) in a 2-dimensional space, find the best path from s to t, where the length of the path is defined as the weighted sum of the Euclidean length of the sub paths inside each region. Let

Carlos Lara

2006-01-01

152

Absorption lengths in the holographic plasma  

Microsoft Academic Search

We consider the effect of a periodic perturbation with frequency omega on the holographic Script N = 4 plasma represented by the planar AdS black hole. The response of the system is given by exponentially decaying waves. The corresponding complex wave numbers can be found by solving wave equations in the AdS black hole background with infalling boundary conditions on

Irene Amado; Carlos Hoyos; Karl Landsteiner; Sergio Montero

2007-01-01

153

Measuring Length  

NSDL National Science Digital Library

Practice measuring length. Play this fun game to work on length. Measure the teddy Next, practice measuring to the nearest 1/2 inch. Measure to 1/2 inches If your ready for a challenge, practice this next game: Measure to 1/4 inches Play the Fish Tales game! *Once you have played all the games, have an adult sign your planner that you practiced these games! You'll ...

Miss Lerdahl

2010-01-26

154

Off-axis paths in spherical mirror interferometers  

Microsoft Academic Search

vO = 24r, and g being integers, the rays retrace their paths. These ray paths give rise to additional resonances which were observed. Pictures of the points of reflection are reproduced. The theory is in good agreement with the experi- mental observations. In laser amplifiers these ray paths enable one to obtain long effective path lengths in the active medium

D. Herriott; H. Kogelnik; R. Kompfner

1964-01-01

155

Variable path cryogenic acoustic interferometer  

NASA Astrophysics Data System (ADS)

We describe a variable path acoustic interferometer for use at cryogenic temperatures. Movement is enabled without mechanical coupling via two piezoelectric bimorphs wired and mounted in a manner that preserves the parallelism of two ultrasonic transducers that define the acoustic path. A certain degree of in situ alignment can also be accomplished. Path length sweeps from 0 to 180 ?m have been made at cryogenic temperatures and preliminary sound velocity measurements in liquid 4He and gaseous 3He near 4 K are presented which agree well with past measurements.

Kucera, D. M.; Ketterson, J. B.

1998-12-01

156

Exciton coherence length fluctuations in chromophore aggregates probed by multidimensional optical spectroscopy  

PubMed Central

The coherent third order optical response of molecular aggregates with fluctuating frequencies, couplings, and transition dipole moments is studied. We derived stochastic nonlinear exciton equations (SNEEs) by combining the quasiparticle picture of excitons with the path integral over stochastic bath paths described by the stochastic Liouville equations. Coherent two-dimensional (2D) spectra are calculated for a tetramer model system whose transition dipole orientations undergo two-state stochastic jumps on an arbitrary timescale. Correspondence between domains of ordered dipoles, which determine the exciton coherence length and the absorption peaks, is established. Signatures of domain coherence length fluctuations are observed in the cross peak dynamics of the 2D spectra in specific pulse polarization configurations. PMID:20614954

Šanda, František; Perlík, Václav; Mukamel, Shaul

2010-01-01

157

Double-beam laser indirect absorption detection in capillary electrophoresis  

SciTech Connect

The use of a laser for optical detection in capillary electrophoresis (CE) allows efficient light coupling. By increasing the absorption path length and by reducing noise through an all-electronic noise canceller, the performance of indirect absorption detection is substantially enhanced. In 75-[mu]m capillaries, as low as 1 [times] 10[sup [minus]7] M pyruvate (10[sup [minus]16] mol injected) can be detected. In 14-[mu]m capillaries, 3 [times] 10[sup [minus]6] M (1.5 [times] 10[sup [minus]16] mol injected) can be detected. When a cationic chromophore is used, K[sup +] at 1 [times] 10[sup [minus]6] M injected is detectable. These represent the best performance to date, by over 1 order of magnitude, for indirect absorption detection in CE without preconcentration. 26 refs., 5 figs.

Xue, Y.; Yeung, E.S. (Ames Lab., IA (United States) Iowa State Univ., Ames, IA (United States))

1993-10-15

158

Finger Length  

NSDL National Science Digital Library

Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. This Science Update describes a recent study that looks to finger length for signs of a man's pre-natal exposure to testosterone.

Science Update

2005-03-28

159

Finger Length  

NSDL National Science Digital Library

This Science Update explores male agression patterns and their correlation to pre-natal testosterone exposure. Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. One recent study looks to finger length for signs of a man's pre-natal exposure to testosterone.n women, the index and ring finger are roughly equal in length. But in most men, the ring finger is longer. That's a result of fetal exposure to testosterone. Psychologists Alison Bailey and Pete Hurd, of the University of Alberta in Canada, studied these finger ratios in male college students. And they found that men with more dramatic differences tended to be more aggressive. Additional links to resources are given for further inquiry.

American Association for the Advancement of Science (; )

2005-03-28

160

Term Paths  

NSDL National Science Digital Library

Students follow several pathways using anatomical directions on a simulated "body" produced from a copy of a school building's fire evacuation plan. The main hallways are designated as major blood vessels and the various areas of the school, the head, chest, abdomen, etc. Students complete several pathways using anatomical terms as directions. For example, one of my paths begins, "Ex- ot-, ad- superior, ecto- derm-, peri-frontal, circum- rhino-, " which loosely means, exit the ear, go to the superior region, outside the skin, around the frontal region, around the nose. At the end of each path I leave a clue that lets me know the students actually made it. The combined clues form a sentence.

Cynthia Ann Radle (McCullough High School REV)

1995-06-30

161

Lemke paths and P-matrices  

SciTech Connect

One can define for an LCP (A, b) with artificial vector d, n internally vertex disjoint Lemke paths to solve the LCP, where A is an n {times} n matrix. The lengths of the set of Lemke paths are investigated in the case that A is a P-matrix. We introduce a class of matrices, the complete hidden Minkowski matrices, that guarantee a set of short Lemke paths.

Morris, W.

1994-12-31

162

An introduction to critical paths.  

PubMed

A critical path defines the optimal sequencing and timing of interventions by physicians, nurses, and other staff for a particular diagnosis or procedure. Critical paths are developed through collaborative efforts of physicians, nurses, pharmacists, and others to improve the quality and value of patient care. They are designed to minimize delays and resource utilization and to maximize quality of care. Critical paths have been shown to reduce variation in the care provided, facilitate expected outcomes, reduce delays, reduce length of stay, and improve cost-effectiveness. The approach and goals of critical paths are consistent with those of total quality management (TQM) and can be an important part of an organization's TQM process. PMID:15739581

Coffey, Richard J; Richards, Janet S; Remmert, Carl S; LeRoy, Sarah S; Schoville, Rhonda R; Baldwin, Phyllis J

2005-01-01

163

Path planning control  

NASA Technical Reports Server (NTRS)

Viewgraphs on path planning control are presented. Topics covered include: model based path planning; sensor based path planning; hybrid path planning; proximity sensor array; and applications for fuzzy logic.

Mcroberts, Malcolm

1990-01-01

164

Length-dependent plasmon resonance in single-walled carbon nanotubes.  

PubMed

The optical response of single-walled carbon nanotubes (SWCNTs) to far-infrared (FIR) radiation was systematically studied using various SWCNTs with different tube-length distributions. The observed peak position in the FIR spectra linearly scaled with the inverse of tube length irrespective of diameter, which is consistent with the dispersion relation predicted by the one-dimensional plasmon resonance model. The effects of chemical doping on the FIR spectra of the separated metallic and semiconducting SWCNTs clearly indicate that the motion of plasmons in the electronic band structures is primarily responsible for the optical response in these spectral regions. The observed absorption peaks are naturally sensitive to the presence of defects on the tube wall and correlated with the electric resistance, suggesting that the plasmons resonate with the current path length of the SWCNTs. PMID:25283493

Morimoto, Takahiro; Joung, Soon-Kil; Saito, Takeshi; Futaba, Don N; Hata, Kenji; Okazaki, Toshiya

2014-10-28

165

Covering Points of a Digraph with Point-Disjoint Paths and Its Application to Code Optimization  

Microsoft Academic Search

A point-disjoint path cover of a directed graph is a collection of point-disjoint paths (some paths possibly having zero length) which covers all the points. A path cover which minimizes the number of paths corresponds to an optimal sequence of the steps of a computer program for efficient coding and documentation. The minimization problem for the general directed graph is

Francis T. Boesch; James F. Gimpel

1977-01-01

166

Ultraviolet absorption hygrometer  

DOEpatents

An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

Gersh, M.E.; Bien, F.; Bernstein, L.S.

1986-12-09

167

Automatic Control Of Length Of Welding Arc  

NASA Technical Reports Server (NTRS)

Nonlinear relationships among current, voltage, and length stored in electronic memory. Conceptual microprocessor-based control subsystem maintains constant length of welding arc in gas/tungsten arc-welding system, even when welding current varied. Uses feedback of current and voltage from welding arc. Directs motor to set position of torch according to previously measured relationships among current, voltage, and length of arc. Signal paths marked "calibration" or "welding" used during those processes only. Other signal paths used during both processes. Control subsystem added to existing manual or automatic welding system equipped with automatic voltage control.

Iceland, William F.

1991-01-01

168

Ray Paths  

NSDL National Science Digital Library

For the next two exercises, we will break up into groups of four. Each member of the group will represent one of four waves leaving the source: direct wave, ground roll, reflected wave, and head wave. All four "waves" will leave the source at the same time and travel at a particular speed and path as directed by the instructor. ALL students will record the arrival time of each "wave" at each geophone until all 12 geophones have been used. Plot arrival time versus distance for each "wave". Do any of the time versus distance curves fit a straight line? Do any of them not fit a straight line? Explain why they do or don't fit a straight line. Uses online and/or real-time data Has minimal/no quantitative component

169

Atmospheric absorption model from 0.01 to 10 wave numbers  

NASA Astrophysics Data System (ADS)

The Applied Physics Laboratory has developed a physical optics electromagnetic propagation computer code at radar frequencies that features long path length representation of atmospheric waveguides or ducts. Thus, an accurate tropospheric absorption model, emphasizing water vapor and oxygen effects, is required for a realistic code. The HITRAN database now provides a comprehensive characterization of spectral lines from 0 to 10 cm-1. A theoretical local line shape is used with this database, which improves the traditional models. Also, a new semiempirical water vapor continuum model has been developed based on the theoretical work of Birnbaum and the most recent experimental data. The result is an improved model for low-altitude, long path calculations of atmospheric absorption at radar and millimeter wavelengths.

Thomas, Michael E.

1990-09-01

170

[Measurement on gas temperature distribution by tunable diode laser absorption spectroscopy].  

PubMed

The technique of tunable diode laser absorption spectroscopy (TDLAS) can be used for gas temperature distribution measurement by scanning multiple gas absorption lines with a tunable diode laser. The fundamental of gas temperature distribution measurement by TDLAS is introduced in the present paper, and the discretization strategy of equation for gas absorption is also given here. Using constrained linear least-square fitting method, the gas temperature distribution can be calculated with the help of physical constraints under the condition of uniform gas concentration and pressure. Based on the spectral parameters of four CO absorption lines near 6330 cm(-1) from HITRAN database, the model of two-temperature distribution at 300 and 600 K with each path length of 55 cm was set up. The effects of relative measurement error and different path length constraints of temperature bins on the gas temperature distribution measurement results were simulated by constrained linear least-square fitting. The results show that the temperature distribution calculation error increases as the relative measurement error rises. A measurement error of 5% could lead to a maximum relative error of 11%, and an average relative error of 2.2% for calculation result. And the weak physical constraints of path length for temperature bins could increase the calculation result error during the process of constrained linear least-square fitting. By setting up the model of two-temperature distribution with gas cells at room temperature as the cold section and in tube furnace as the hot section, the experiment of gas temperature distribution measurement in lab was carried out. Using four absorption lines of CO near 6330 cm(-1) scanned by VCSEL diode laser, and fitting the background laser intensity without absorption by the cubic polynomial to get the baseline signal, the integrals of spectral absorbance for gas temperature distribution measurement can be calculated. The relative calculation errors of path length for temperature bins are about 7.3%, 6.5%, 4.7% and 2.7% in the four cases. PMID:18975785

Li, Ning; Yan, Jian-hua; Wang, Fei; Chi, Yong; Cen, Ke-fa

2008-08-01

171

Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar  

NASA Technical Reports Server (NTRS)

A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

172

Atmospheric absorption of high frequency noise and application to fractional-octave bands  

NASA Technical Reports Server (NTRS)

Pure tone sound absorption coefficients were measured at 1/12 octave intervals from 4 to 100 KHz at 5.5K temperature intervals between 255.4 and 310.9 K and at 10 percent relative humidity increments between 0 percent and saturation in a large cylindrical tube (i.d., 25.4 cm; length, 4.8 m). Special solid-dielectric capacitance transducers, one to generate bursts of sound waves and one to terminate the sound path and detect the tone bursts, were constructed to fit inside the tube. The absorption was measured by varying the transmitter receiver separation from 1 to 4 m and observing the decay of multiple reflections or change in amplitude of the first received burst. The resulting absorption was compared with that from a proposed procedure for computing sound absorption in still air. Absorption of bands of noise was numerically computed by using the pure tone results. The results depended on spectrum shape, on filter type, and nonlinearly on propagation distance. For some of the cases considered, comparison with the extrapolation of ARP-866A showed a difference as large as a factor of 2. However, for many cases, the absorption for a finite band was nearly equal to the pure tone absorption at the center frequency of the band. A recommended prediction procedure is described for 1/3 octave band absorption coefficients.

Shields, F. D.; Bass, H. E.

1977-01-01

173

Continuously variable focal length lens  

DOEpatents

A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

Adams, Bernhard W; Chollet, Matthieu C

2013-12-17

174

[Measurement of OH radicals in flame with high resolution differential optical absorption spectroscopy].  

PubMed

The present paper describes a new developed high resolution differential optical absorption spectroscopy instrument used for the measurement of OH radicals in flame. The instrument consists of a Xenon lamp for light source; a double pass high resolution echelle spectrometer with a resolution of 3.3 pm; a multiple-reflection cell of 20 meter base length, in which the light reflects in the cell for 176 times, so the whole path length of light can achieve 3 520 meters. The OH radicals'6 absorption lines around 308 nm were simultaneously observed in the experiment. By using high resolution DOAS technology, the OH radicals in candles, kerosene lamp, and alcohol burner flames were monitored, and their concentrations were also inverted. PMID:22250529

Liu, Yu; Liu, Wen-Qing; Kan, Rui-Feng; Si, Fu-Qi; Xu, Zhen-Yu; Hu, Ren-Zhi; Xie, Pin-Hua

2011-10-01

175

Influence of absorption induced thermal initiation pathway on irradiance threshold for laser induced breakdown  

PubMed Central

We investigated the influence of thermal initiation pathway on the irradiance threshold for laser induced breakdown in transparent, absorbing and scattering phantoms. We observed a transition from laser-induced optical breakdown to laser-induced thermal breakdown as the absorption coefficient of the medium is increased. We found that the irradiance threshold after correction for the path length dependent absorption and scattering losses in the medium is lower due to the thermal pathway for the generation of seed electrons compared to the laser-induced optical breakdown. Furthermore, irradiance threshold gradually decreases with the increase in the absorption properties of the medium. Creating breakdown with lower irradiance threshold that is specific at the target chromophore can provide intrinsic target selectivity and improve safety and efficacy of skin treatment methods that use laser induced breakdown.

Varghese, Babu; Bonito, Valentina; Jurna, Martin; Palero, Jonathan; Verhagen, Margaret Hortonand Rieko

2015-01-01

176

Competition for Shortest Paths on Sparse Graphs  

NASA Astrophysics Data System (ADS)

Optimal paths connecting randomly selected network nodes and fixed routers are studied analytically in the presence of a nonlinear overlap cost that penalizes congestion. Routing becomes more difficult as the number of selected nodes increases and exhibits ergodicity breaking in the case of multiple routers. The ground state of such systems reveals nonmonotonic complex behaviors in average path length and algorithmic convergence, depending on the network topology, and densities of communicating nodes and routers. A distributed linearly scalable routing algorithm is also devised.

Yeung, Chi Ho; Saad, David

2012-05-01

177

Evaluation of ammonia absorption coefficients by photoacoustic spectroscopy for detection of ammonia levels in human breath  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy represents a powerful technique for measuring extremely low absorptions independent of the path length and offers a degree of parameter control that cannot be attained by other methods. We report precise measurements of the ammonia absorption coefficients at the CO2 laser wavelengths by using a photoacoustic (PA) cell in an extracavity configuration and we compare our results with other values reported in the literature. Ammonia presents a clear fingerprint spectrum and high absorption strengths in the CO2 wavelengths region. Because more than 250 molecular gases of environmental concern for atmospheric, industrial, medical, military, and scientific spheres exhibit strong absorption bands in the region 9.2-10.8 ?m, we have chosen a frequency tunable CO2 laser. In the present work, ammonia absorption coefficients were measured at both branches of the CO2 laser lines by using a calibrated mixture of 10 ppm NH3 in N2. We found the maximum absorption in the 9 ?m region, at 9R(30) line of the CO2 laser. One of the applications based on the ammonia absorption coefficients is used to measure the ammonia levels in exhaled human breath. This can be used to determine the exact time necessary at every session for an optimal degree of dialysis at patients with end-stage renal disease.

Dumitras, D. C.; Dutu, D. C.; Matei, C.; Cernat, R.; Banita, S.; Patachia, M.; Bratu, A. M.; Petrus, M.; Popa, C.

2011-04-01

178

Opportunity's Path  

NASA Technical Reports Server (NTRS)

This Long Term Planning graphic was created from a mosaic of navigation camera images overlain by a polar coordinate grid with the center point as Opportunity's original landing site. The blue dots represent the rover position at various locations.

The red dots represent the center points of the target areas for the instruments on the rover mast (the panoramic camera and miniature thermal emission spectrometer). Opportunity visited Stone Mountain on Feb. 5. Stone Mountain was named after the southernmost point of the Appalachian Mountains outside of Atlanta, Ga. On Earth, Stone Mountain is the last big mountain before the Piedmont flatlands, and on Mars, Stone Mountain is at one end of Opportunity Ledge. El Capitan is a target of interest on Mars named after the second highest peak in Texas in Guadaloupe National Park, which is one of the most visited outcrops in the United States by geologists. It has been a training ground for students and professional geologists to understand what the layering means in relation to the formation of Earth, and scientists will study this prominent point of Opportunity Ledge to understand what the layering means on Mars.

The yellow lines show the midpoint where the panoramic camera has swept and will sweep a 120-degree area from the three waypoints on the tour of the outcrop. Imagine a fan-shaped wedge from left to right of the yellow line.

The white contour lines are one meter apart, and each drive has been roughly about 2-3 meters in length over the last few sols. The large white blocks are dropouts in the navigation camera data.

Opportunity is driving along and taking a photographic panorama of the entire outcrop. Scientists will stitch together these images and use the new mosaic as a 'base map' to decide on geology targets of interest for a more detailed study of the outcrop using the instruments on the robotic arm. Once scientists choose their targets of interest, they plan to study the outcrop for roughly five to fifteen sols. This will include El Capitan and probably one to two other areas.

Blue Dot Dates Sol 7 / Jan 31 = Egress & first soil data collected by instruments on the arm Sol 9 / Feb 2 = Second Soil Target Sol 12 / Feb 5 = First Rock Target Sol 16 / Feb 9 = Alpha Waypoint Sol 17 / Feb 10 = Bravo Waypoint Sol 19 or 20 / Feb 12 or 13 = Charlie Waypoint

2004-01-01

179

Precise cavity enhanced absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A short review of recent achievements in high-precision cavity enhanced absorption spectroscopy is presented. Actual challenges and development paths in modern line shape study are indicated and discussed. The importance of identification and quantification of systematic instrumental errors affecting the measured line shape is highlighted. New, alternative measurement methods based on cavity enhanced spectroscopy are proposed.

Cygan, A.; Wcis?o, P.; Wójtewicz, S.; Mas?owski, P.; Domys?awska, J.; Trawi?ski, R. S.; Ciury?o, R.; Lisak, D.

2014-11-01

180

On the Generation of Nearly Optimal, Planar Paths of Bounded Curvature and Bounded Curvature Gradient  

E-print Network

is a generalization of the Dubins problem to account for more realistic vehicle dynamics. The problem is solved. First, the generated path should be compatible to the vehicle dynamics, and second, the path should is the total length of the path, whereas the vehicle's dynamics may be incorporated into the path generation

Tsiotras, Panagiotis

181

ALGEBRAIC ASPECTS OF EMISSION TOMOGRAPHY WITH ABSORPTION  

E-print Network

ALGEBRAIC ASPECTS OF EMISSION TOMOGRAPHY WITH ABSORPTION L. Hajdu and R. Tijdeman Abstract of emission tomography with absorption, con- sider a ray (such as light or X-ray) transmitting through #1; e #22;x ; where #22; #21; 0 denotes the absorption coeÃ?cient of the material, and x is the length

Tijdeman, Robert

182

A multiple path photonic lab on a chip for parallel protein concentration measurements.  

PubMed

We propose a PDMS-based photonic system for the accurate measurement of protein concentration with minute amounts of the sample. As opposed to the state of the art approach, in the multiple path photonic lab on a chip (MPHIL), analyte concentration or molar absorptivity is obtained with a single injection step, by performing simultaneous parallel optical measurements varying the optical path length. Also, as opposed to the standard calibration protocol, the MPHIL approach does not require a series of measurements at different concentrations. MPHIL has three main advantages: firstly the possibility of dynamically selecting the path length, always working in the absorbance vs. concentration linear range for each target analyte. Secondly, a dramatic reduction of the total volume of the sample required to obtain statistically reliable results. Thirdly, since only one injection is required, the measurement time is minimized, reducing both contamination and signal drifts. These characteristics are clearly advantageous when compared to commercial micro-spectrophotometers. The MPHIL concept was validated by testing three commercial proteins, lysozyme (HEWL), glucose isomerase (d-xylose-ketol-isomerase, GI) and Aspergillus sp. lipase L (BLL), as well as two proteins expressed and purified for this study, B. cereus formamidase (FASE) and dihydropyrimidinase from S. meliloti CECT41 (DHP). The use of MPHIL is also proposed for any spectrophotometric measurement in the UV-VIS range, as well as for its integration as a concentration measurement platform in more advanced photonic lab on a chip systems. PMID:25537135

Rodríguez-Ruiz, Isaac; Conejero-Muriel, Mayte; Ackermann, Tobias N; Gavira, José A; Llobera, Andreu

2015-02-01

183

Spectroscopic method for determination of the absorption coefficient in brain tissue  

NASA Astrophysics Data System (ADS)

I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, ?a. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(?a)+d ln(Is)ln(?a), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes.

Johansson, Johannes D.

2010-09-01

184

Finding a Hamiltonian Path in a Cube with Specified Turns is Hard  

E-print Network

We prove the NP-completeness of finding a Hamiltonian path in an N × N × N cube graph with turns exactly at specified lengths along the path. This result establishes NP-completeness of Snake Cube puzzles: folding a chain ...

Abel, Zachary Ryan

185

Lower Semicontinuity of Weighted Path Length in BV  

E-print Network

for a class of weigthed metrics in BV. These Riemann­type metrics, uniformly equivalent to the L 1 distance­type metric, uniformly equivalent to the standard L 1 distance. The construction of this weighted distance(b) = v \\Psi : (1:3) We remark that this weighted distance does not fit within the standard framework

186

Nonlinear optical propagation in a tandem structure comprising nonlinear absorption and scattering materials  

SciTech Connect

Laser propagation in a tandem structure comprising carbon nanotubes and phthalocyanines is studied by Z-scan method. Due to the different mechanisms of the two materials, the laser beam can be attenuated with different absorptivities, by changing the sequence of light passing through each material. Numerical simulations considering the effect of path length and the change of nonlinear coefficient within each material are conducted for understanding the distribution of laser intensity in the tandem system and hence, fitting of the asymmetric Z-scan curves. The results are helpful for the design of nonlinear optical devices comprising multiple nonlinear materials and mechanisms.

Wang, Kangpeng; Ju, Yongfeng; He, Jin; Zhang, Long, E-mail: jwang@siom.ac.cn, E-mail: lzhang@siom.ac.cn; Wang, Jun, E-mail: jwang@siom.ac.cn, E-mail: lzhang@siom.ac.cn [Key Laboratory of Materials for High-Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Chen, Yu [Key Laboratory for Advanced Materials, Department of Chemistry, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Blau, Werner J. [Key Laboratory of Materials for High-Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); School of Physics and the Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland)

2014-01-13

187

Essential paths space on ADE SU(3) graphs: A geometric approach  

E-print Network

For simply laced $SU(3)$ graphs we offer a geometric understanding of the path creation and annihilation operators for $SU(3)$ in terms of creation and annihilation of sequences of three vertices forming triangular cells or collapsed triangular cells. We prove that the space of paths of a given length can be decomposed as a direct sum of orthogonal sub-spaces constructed by recurrent applications of the path creation operator on subspaces of essential paths of shorter length.

Jesus A. Pineda; E. Isasi; M. I. Caicedo

2015-04-10

188

Absorption of planar waves in a draining bathtub  

SciTech Connect

We present an analysis of the absorption of acoustic waves by a black hole analogue in (2+1) dimensions generated by a fluid flow in a draining bathtub. We show that the low-frequency absorption length is equal to the acoustic hole circumference and that the high-frequency absorption length is 4 times the ergoregion radius. For intermediate values of the wave frequency, we compute the absorption length numerically and show that our results are in excellent agreement with the low- and high-frequency limits. We analyze the occurrence of superradiance, manifested as negative partial absorption lengths for corotating modes at low frequencies.

Oliveira, Ednilton S.; Dolan, Sam R.; Crispino, Luis C. B. [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970, Sao Paulo, SP (Brazil) and Faculdade de Fisica, Universidade Federal do Para, 66075-110, Belem, Para (Brazil); School of Mathematics, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Faculdade de Fisica, Universidade Federal do Para, 66075-110, Belem, Para (Brazil)

2010-06-15

189

DISCUSS: Critical Path Analysis  

NSDL National Science Digital Library

This module, by Barrie Baker and Neville Hunt of Coventry University, introduces critical path analysis and addresses the following topics: Networks, Critical paths, Floats, Activity-on-node (AON) networks. Excel spreadsheets are used to provide examples and exercises.

Baker, Barrie

190

Traveling salesman path problems  

E-print Network

In the Traveling Salesman Path Problem, we are given a set of cities, traveling costs between city pairs and fixed source and destination cities. The objective is to find a minimum cost path from the source to destination ...

Lam, Fumei

2005-01-01

191

Flow paths of submarine groundwater discharge (SGD) and its relation to Fe diagenesis: A case study from Indian River Lagoon, Florida  

Microsoft Academic Search

In the subterranean estuary, flow paths for submarine groundwater discharge (SGD) depend on two sources of water - freshwater and recirculated seawater. The lengths of freshwater flow paths increase as discharge points move offshore across the outflow face. Recirculated seawater flow paths can have different lengths depending on mechanisms driving the flow, with the longest flow paths resulting from diffusive

M. Roy; J. B. Martin; J. E. Cable; J. Cherrier; C. G. Smith; A. Dorsett

2008-01-01

192

Geodesy by radio interferometry: Effects of atmospheric modeling errors on estimates of baseline length  

Microsoft Academic Search

Analysis of very long baseline interferometry data indicates that systematic errors in prior estimates of baseline length, of order 5 cm for  8000-km baselines, were due primarily to mismodeling of the electrical path length of the troposphere and mesosphere (\\

J. L. Davis; T. A. Herrinch; I. I. Shapiro; A. E. E. Rollers; G. Elgered

1985-01-01

193

Approximate Shortest Path Queries Using Voronoi Duals  

NASA Astrophysics Data System (ADS)

We propose an approximation method to answer point-to-point shortest path queries in undirected edge-weighted graphs, based on random sampling and Voronoi duals. We compute a simplification of the graph by selecting nodes independently at random with probability p. Edges are generated as the Voronoi dual of the original graph, using the selected nodes as Voronoi sites. This overlay graph allows for fast computation of approximate shortest paths for general, undirected graphs. The time-quality tradeoff decision can be made at query time. We provide bounds on the approximation ratio of the path lengths as well as experimental results. The theoretical worst-case approximation ratio is bounded by a logarithmic factor. Experiments show that our approximation method based on Voronoi duals has extremely fast preprocessing time and efficiently computes reasonably short paths.

Honiden, Shinichi; Houle, Michael E.; Sommer, Christian; Wolff, Martin

194

Fourier-transform absorption spectrum of H2O in the region of 15500-16000 cm-1  

NASA Astrophysics Data System (ADS)

In this paper we present the results of H2 16O absorption spectrum investigation recorded by a high resolution Fouriertransform spectrometer IFS-125M in the region 15500 - 16000 cm-1. Absorption path of 34.8 m and resolution of 0.03 cm-1 were chosen to record the spectrum. White type multipass absorption cell with a basic length of 60 cm were used. Light-emitting diode (LED) was applied as a source of radiation. Signal-to-noise ratio is about 104, making it possible to measure parameters of lines with intensity up to 2*10-27 cm/molecule. Least-square-fitting algorithm was used to retrieve of the spectroscopic parameters from measured spectral data set. Spectral line positions and line intensities derived from the fitting were compared to data obtained in previous works.

Sinitsa, L. N.; Serduykov, V. I.; Vasilchenko, S. S.; Bykov, A. D.; Shcherbakov, A. P.; Polovtseva, E. R.; Kalinin, K. V.

2014-11-01

195

Walden's Paths - Ensemble Edition  

NSDL National Science Digital Library

Walden?s Paths enables users of digital document collections (e.g. the Web) to exploit these documents by reusing them for previously unintended audiences in an academic setting. Authors of paths (usually educators) overlay a linear, directed meta-structure over the Web documents and recontextualize these by adding explanatory text to achieve their curricular goals. Paths do not modifythe structure or content of the Web resources that they include. The creation of a path over pre-organized content (e.g. books, Web pages) to reorganize and associate related information serves to facilitate easy retrieval and communication. Walden?s Paths displays the information that the path points to in conjunction with the textual annotations added by the author of the path.

2011-01-04

196

Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect  

DOEpatents

An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect have been developed. Two sample cells are placed in each arm of an interferometer and are traversed by colinear probe and heating laser beams. The interrogation probe beams are recombined forming a fringe pattern, the intensity of which can be related to changes in optical path length of these laser beams through the cells. This in turn can be related to small differences in optical absorptivity which results in different amounts of sample heating when the heating laser beams are turned on, by the fact that the index of refraction of a liquid is temperature dependent. A critical feature of this invention is the stabilization of the optical path of the probe beams against drift. Background (solvent) absorption can then be suppressed by a factor of approximately 400. Solute absorptivities of about 10[sup [minus]5] cm[sup [minus]1] can then be determined in the presence of background absorptions in excess of 10[sup [minus]3] cm[sup [minus]1]. In addition, the smallest absorption measured with the instant apparatus and method is about 5 [times] 10[sup [minus]6] cm[sup [minus]1]. 6 figs.

Cremers, D.A.; Keller, R.A.

1984-05-08

197

[Retrieval of monocyclic aromatic hydrocarbons with differential optical absorption spectroscopy].  

PubMed

Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, e. g. SO2, NO2, O3 etc. However, unlike the absorption spectra of SO2 and NO2, the analysis of aromatic compounds is difficult and strongly suffers from the cross interference of other absorbers (Herzberg bands of oxygen, ozone and sulfur dioxide), especially with relatively low concentrations of aromatic compounds in the atmosphere. In the present paper, the DOAS evaluation of aromatic compounds was performed by nonlinear least square fit with two interpolated oxygen optical density spectra at different path lengths and reference spectra of ozone at different temperature and SO2 cross section to correct the interference from absorbers of O2, O3 and SO2. The measurement of toluene, benzene, (m, p, o) xylene and phenol with a DOAS system showed that DOAS method is suitable for monocyclic aromatic compounds monitoring in the atmosphere. PMID:17112022

Xie, Pin-Hua; Fu, Qiang; Liu, Jian-Guo; Liu, Wen-Qing; Qin, Min; Li, Ang; Liu, Shi-Sheng; Wei, Qing-Nong

2006-09-01

198

Path optimization for oil probe  

NASA Astrophysics Data System (ADS)

We discuss a robust method for optimal oil probe path planning inspired by medical imaging. Horizontal wells require three-dimensional steering made possible by the rotary steerable capabilities of the system, which allows the hole to intersect multiple target shale gas zones. Horizontal "legs" can be over a mile long; the longer the exposure length, the more oil and natural gas is drained and the faster it can flow. More oil and natural gas can be produced with fewer wells and less surface disturbance. Horizontal drilling can help producers tap oil and natural gas deposits under surface areas where a vertical well cannot be drilled, such as under developed or environmentally sensitive areas. Drilling creates well paths which have multiple twists and turns to try to hit multiple accumulations from a single well location. Our algorithm can be used to augment current state of the art methods. Our goal is to obtain a 3D path with nodes describing the optimal route to the destination. This algorithm works with BIG data and saves cost in planning for probe insertion. Our solution may be able to help increase the energy extracted vs. input energy.

Smith, O'Neil; Rahmes, Mark; Blue, Mark; Peter, Adrian

2014-05-01

199

Neutron scattering lengths and cross sections  

Microsoft Academic Search

The application of thermal neutron scattering to the study of the structure and dynamics of condensed matter requires a knowledge of the scattering lengths and the corresponding scattering and absorption cross sections of the elements. Ln some cases, values for the individual isotopes are needed as well. This information is required to obtain an absolute normalization ofthe scatteredneutron distributions, tocalculate

Varley F. Sears

1992-01-01

200

Intrinsic UV absorption spectrometry observed with a liquid core waveguide as a sensor technique for monitoring ozone in water.  

PubMed

The industrial use of ozone as a sanitizing agent in water treatment and food processing in recent years calls for sensor technologies for monitoring ozone in water for process control. Ozone molecules absorb UV light with a peak absorption wavelength at 254 nm. This property has been used in this work to develop a simple sensor technology for online, real-time continuous monitoring of trace ozone in water. A Teflon AF2400 tube filled with pure water forms a liquid core waveguide (LCW), which is used as a long-path-length optical absorption cell. This pure water filled tube was deployed into a water sample. Ozone molecules dissolved in the water sample permeate through the Teflon AF2400 tube wall and dissolve in water filled in the tube. This prevents interference species from entering the LCW, and eliminates interferences. The optical absorption signal of the long-path-length cell at 254 nm measured by guiding light through the LCW is used as a sensing signal. This simple structured sensor does not involve any chemical reagent, is reversible, and has a response time <4.5 minutes. It can be used to detect ozone in water samples down to 3.6 × 10(-9) mol L(-1). PMID:21743914

Le, Trang; Tao, Shiquan

2011-08-21

201

On-column double-beam laser absorption detection for capillary electrophoresis  

SciTech Connect

Double-beam laser absorption detection in capillary electrophoresis (CE) has been developed. This is based on the direct subtraction of reference and signal photocurrents by an electronic circuit, under feedback control, to reduce background noise. A simple equation for calculating concentrations has been proposed and was confirmed by experimental results. A practical noise-to-signal ratio of 1 [times] 10[sup [minus]5] in intensity is achieved. This is 5 times lower than that of commercial CE systems. For absorbance detection, as low as 2 [times] 10[sup [minus]8] M malachite green can be detected. This corresponds to a 25-fold improvement of detection limit over commercial systems. This gain in detectability results from both a reduction in intensity fluctuations (noise) and an increase in the effective absorption path length (signal). 22 refs., 6 figs.

Xue, Y.; Yeung, E.S. (Iowa State Univ., Ames (United States))

1993-08-01

202

Laser absorption spectroscopy of oxygen confined in highly porous hollow sphere xerogel.  

PubMed

An Al2O3 xerogel with a distinctive microstructure is studied for the application of laser absorption spectroscopy of oxygen. The xerogel has an exceptionally high porosity (up to 88%) and a large pore size (up to 3.6 µm). Using the method of gas-in-scattering media absorption spectroscopy (GASMAS), a long optical path length (about 3.5m) and high enhancement factor (over 300 times) are achieved as the result of extremely strong multiple-scattering when the light is transmitted through the air-filled, hollow-sphere alumina xerogel. We investigate how the micro-physical feature influences the optical property. As part of the optical sensing system, the material's gas exchange dynamics are also experimentally studied. PMID:24663551

Yang, Lin; Somesfalean, Gabriel; He, Sailing

2014-02-10

203

Interstellar Metastable Helium Absorption as a Probe of the Cosmic-Ray Ionization Rate  

E-print Network

The ionization rate of interstellar material by cosmic rays has been a major source of controversy, with different estimates varying by three orders of magnitude. Observational constraints of this rate have all depended on analyzing the chemistry of various molecules that are produced following cosmic-ray ionization, and in many cases these analyses contain significant uncertainties. Even in the simplest case (H3+) the derived ionization rate depends on an (uncertain) estimate of the absorption path length. In this paper we examine the feasibility of inferring the cosmic-ray ionization rate using the 10830 A absorption line of metastable helium. Observations through the diffuse clouds toward HD 183143 are presented, but yield only an upper limit on the metastable helium column density. A thorough investigation of He+ chemistry reveals that only a small fraction of He+ will recombine into the triplet state and populate the metastable level. In addition, excitation to the triplet manifold of helium by secondary...

Indriolo, Nick; Hinkle, K H; McCall, Benjamin J

2009-01-01

204

TCP Capture Avoidance in Wireless Networks Based on Path Length and Path Density  

E-print Network

802.11 products and the popularity of the existing TCP/IP protocol stack. In our approach we attempted investigation aims at understanding the global behavior of multiple multi-hop TCP connec- tions under worst case placement of nodes. Therefore, in the first stage of our research, we intro- duce a network model which

Vetter, Thomas

205

Near-IR diode laser absorption for measurement of tropospheric HO2  

NASA Technical Reports Server (NTRS)

The possibility of using tunable lead salt diode lasers in the infrared for measurement of tropospheric HO2 has been frequently considered. Although the sensitivity of diode laser absorption has been improved through the use of high frequency detection techniques, nature has been unkind in that the HO2 absorption cross sections are weak. Even using the most optimistic assumptions about attainable path length and detectable absorbance, measurement of tropospheric HO2 by diode laser absorption in the mid-IR appears marginal. A possible alternative method for measuring HO2 is by absorption at near-infrared wavelengths. Several absorption bands of HO2 occur in the wavelength region between 1.2 and 1.6 micron due to electronic transitions and overtones of the fundamental vibrational modes. InGaAsP diode lasers operate in this wavelength region and can be used for high resolution spectroscopy in a manner analogous to the lead salt lasers. A diode laser system in the near-IR offers some advantages.

Stanton, Alan C.

1994-01-01

206

Wide absorption spectrum measuring methods by DFB-LDs in water vapor detection system  

NASA Astrophysics Data System (ADS)

Two measuring methods of the wide absorption spectrum by distributed feedback laser diodes (DFB-LDs) are presented in detecting the water vapor absorption line. One is the subsection scanning method, and it takes advantage of the wide spectrum tuning range by the temperature modulation and fast spectrum tuning speed by current modulation. Specifically, this method is realized by dividing a target spectral region into several sections which correspond to the specific temperature of DFB-LD, scanning every section by current modulation for hundreds times, and averaging the data to raise the signal to noise ratio (SNR), then combining all sections to get the whole spectrum. An accuracy of 10 ppmv had been obtained in the measurement of water vapor with a 10-cm path length by this method. Another is data fitting method, based on the absorption line-shape function; the absorption line can be described by fitting with partial measured data. The fitting absorption line was fitted well with the measured data, and the square of correlation coefficient (R-square) was no less than 0.99.

Liu, Y. N.; Chang, J.; Lian, J.; Wang, Q.; Lv, G. P.; Wang, W. J.; Liu, Z.; Liu, X. Z.; Zhang, S. S.; Wang, Z. L.; Jiang, S.; Zhu, C. G.; Wei, W.; Sun, B. N.

2014-09-01

207

Arc Length Gone Global  

ERIC Educational Resources Information Center

Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

Boudreaux, Gregory M.; Wells, M. Scott

2007-01-01

208

Measuring Thermodynamic Length  

SciTech Connect

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E

2007-09-07

209

Advanced Physics: Path Integral  

NSDL National Science Digital Library

A cursor is shown in an x-y graph. The cursor can be dragged around the graph and its path is marked as it is moved. The data are sent to a DataTable which shows x, y, and the value of the path integral, F.dl.

Wolfgang Christian

210

The SunPath  

NSDL National Science Digital Library

This site features an interactive applet that models the Sun's path from a geocentric view. It calculates and visualizes the position of the Sun based on latitude and time, and allows students to simulate the Sun's position and path for an hour, a day, a month or a year.

Australian National University

211

Demonstration of scan path optimization in proton therapy  

SciTech Connect

A three-dimensional (3D) intensity modulated proton therapy treatment plan to be delivered by magnetic scanning may comprise thousands of discrete beam positions. This research presents the minimization of the total scan path length by application of a fast simulated annealing (FSA) optimization algorithm. Treatment plans for clinical prostate and head and neck cases were sequenced for continuous raster scanning in two ways, and the resulting scan path lengths were compared: (1) A simple back-and-forth, top-to-bottom (zigzag) succession, and (2) an optimized path produced as a solution of the FSA algorithm. Using a first approximation of the scanning dynamics, the delivery times for the scan sequences before and after path optimization were calculated for comparison. In these clinical examples, the FSA optimization shortened the total scan path length for the 3D target volumes by approximately 13%-56%. The number of extraneous spilled particles was correspondingly reduced by about 13%-54% due to the more efficient scanning maps that eliminated multiple crossings through regions of zero fluence. The relative decrease in delivery time due to path length minimization was estimated to be less than 1%, due to both a high scanning speed and time requirements that could not be altered by optimization (e.g., time required to change the beam energy). In a preliminary consideration of application to rescanning techniques, the decrease in delivery time was estimated to be 4%-20%.

Kang, Joanne H.; Wilkens, Jan J.; Oelfke, Uwe [Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

2007-09-15

212

Michael Grunwald Transition path sampling  

E-print Network

Michael Gr¨unwald Transition path sampling simulations of structural phase transformations compromises the comparability of simulation and experiment considerably. Here, we use transition path sam of parallel crystal planes. We subject the pathways obtained with transition path sam- pling

Gruenwald, Michael

213

Study Tracks Path of Indian Ocean Tsunami  

NSDL National Science Digital Library

Since the Indian Ocean tsunami of December 26, 2004, scientists have tried to retrace the path of the giant waves to learn how and why the water moved in unexpected directions, even turning corners and producing simultaneous wavefronts coming from different directions. This radio broadcast describes efforts to measure the strength, distance traveled inland, and height of the tsunami, as well as mapping its route. The clip is 4 minutes in length.

214

Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers  

NASA Astrophysics Data System (ADS)

Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe-Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8-12 GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30 wt% hollow Ni/Fe-Co (7:3) fibers in length of 180 ?m exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2 GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite.

Yi, Jin Woo; Lee, Sang Bok; Kim, Jin Bong; Lee, Sang Kwan; Park, O. Ok

2014-06-01

215

Tortuous path chemical preconcentrator  

DOEpatents

A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

Manginell, Ronald P. (Albuquerque, NM); Lewis, Patrick R. (Albuquerque, NM); Adkins, Douglas R. (Albuquerque, NM); Wheeler, David R. (Albuquerque, NM); Simonson, Robert J. (Cedar Crest, NM)

2010-09-21

216

A Path to Discovery  

ERIC Educational Resources Information Center

The path taken and the turns made as a turtle traces a polygon are examined to discover an important theorem in geometry. A unique tool, the Angle Adder, is implemented in the investigation. (Contains 9 figures.)

Stegemoller, William; Stegemoller, Rebecca

2004-01-01

217

Neandertal clavicle length  

PubMed Central

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W.; Auerbach, Benjamin M.

2014-01-01

218

Neandertal clavicle length.  

PubMed

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W; Auerbach, Benjamin M

2014-03-25

219

PathFinder Science  

NSDL National Science Digital Library

PathFinder Science contains research projects about water conservation, tardigrades, a winter bird survey, ozone, ultraviolet light and DNA, global warming, spot removal, lichens, stream monitoring, amphibian biomonitoring, and particulate monitoring. Free registration to the PathFinder Science Network offers the opportunity to be a part of the listserv, upload collaborative project data or publish research work. There are tools and tips to help students publish their research on the web.

220

Follow the Paths  

NSDL National Science Digital Library

In this lesson, younger students will be introduced to the various orbital paths that are used for satellites. Using a globe and a satellite model or a large picture of Earth, the teacher will introduce three types of orbital paths (polar, elliptical, and geosynchronous). The students should be able to define 'satellite', define the three types of orbits, describe how satellites orbit the Earth, and understand how they are slowed down by drag from the atmosphere.

221

AIR QUALITY MONITORING IN ATLANTA WITH THE DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER  

EPA Science Inventory

During July and August of 1990, a differential optical absorption spectrometer (DOAS) made by OPSIS Inc. was used to measure gaseous air pollutants over three separate open paths in Atlanta, GA. ver path 1 (1099 m) and path 2 (1824 m), ozone (O3), sulfur dioxide (SO2), nitrogen d...

222

Correlations between bond lengths, Tc, and O vibration frequencies: Raman-scattering and infrared-absorption study of the 1:2:1:2 structure (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 as a function of doping  

NASA Astrophysics Data System (ADS)

Raman-scattering and infrared-absorption measurements on optical phonons are used to investigate the doping-induced changes in the electronic structure of (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 (Tl/Pb-1:2:1:2). In contrast to YBa2Cu3O7-? (YBCO), the doping of the CuO2 planes is achieved by direct substitution of Ca2+ for Y3+ in between the CuO2 planes, enabling the effects of the dynamic out-of-plane charge transfer and doping to be separated. In spite of large changes in Cu to apical-O bond lengths as measured by neutron scattering, we observe no corresponding apical O(2) vibration frequency shifts with doping of the type found in YBCO. Instead, the frequencies of the A1g Raman-active apical O(2) phonon and an A2u IR-active out-of-plane phonon are correlated with the Tc curve.

Mertelj, T.; Mihailovi?, D.; Matacotta, F. C.; Liu, R. S.; Cooper, J. R.; Gameson, I.; Edwards, P. P.

1993-05-01

223

Recent Results From the JPL Carbon Dioxide Laser Absorption Spectrometer  

Microsoft Academic Search

Active optical sensing of atmospheric molecular species relies on measuring the differential absorption between a number of different wavelengths to determine changes in concentration of the species of interest. At JPL we have been developing an aircraft instrument that uses an Integrated Path Differential Absorption (IPDA) approach in the 2-micron spectral region for high-precision measurements of atmospheric carbon dioxide mixing

G. D. Spiers; S. Geier; M. W. Phillips; R. T. Menzies

2007-01-01

224

Resonant absorption and not-so-resonant absorption in short, intense laser irradiated plasma  

SciTech Connect

An analytical model for laser-plasma interaction during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. Both the resonant absorption and not-so-resonant absorption are self-consistently included. Different from the previous theoretical works, the physics of resonant absorption is found to be valid in more general conditions as the steepening of the electron density profile is considered. Even for a relativistic intensity laser, resonant absorption can still exist under certain plasma scale length. For shorter plasma scale length or higher laser intensity, the not-so-resonant absorption tends to be dominant, since the electron density is steepened to a critical level by the ponderomotive force. The laser energy absorption rates for both mechanisms are discussed in detail, and the difference and transition between these two mechanisms are presented.

Ge, Z. Y.; Zhuo, H. B.; Ma, Y. Y.; Yang, X. H.; Yu, T. P.; Zou, D. B.; Yin, Y.; Shao, F. Q. [College of Science, National University of Defense Technology, Changsha 410073 (China)] [College of Science, National University of Defense Technology, Changsha 410073 (China); Yu, W.; Luan, S. X. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)] [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhou, C. T. [College of Science, National University of Defense Technology, Changsha 410073 (China) [College of Science, National University of Defense Technology, Changsha 410073 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Peng, X. J. [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)] [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2013-07-15

225

Peano-like paths for subaperture polishing of optical aspherical surfaces.  

PubMed

Polishing can be more uniform if the polishing path provides uniform coverage of the surface. It is known that Peano paths can provide uniform coverage of planar surfaces. Peano paths also contain short path segments and turns: (1) all path segments have the same length, (2) path segments are mutually orthogonal at the turns, and (3) path segments and turns are uniformity distributed over the domain surface. These make Peano paths an attractive candidate among polishing tool paths because they enhance multidirectional approaches of the tool to each surface location. A method for constructing Peano paths for uniform coverage of aspherical surfaces is proposed in this paper. When mapped to the aspherical surface, the path also contains short path segments and turns, and the above attributes are approximately preserved. Attention is paid so that the path segments are still well distributed near the vertex of the surface. The proposed tool path was used in the polishing of a number of parabolic BK7 specimens using magnetorheological finishing (MRF) and pitch with cerium oxide. The results were rather good for optical lenses and confirm that a Peano-like path was useful for polishing, for MRF, and for pitch polishing. In the latter case, the surface roughness achieved was 0.91 nm according to WYKO measurement. PMID:23736249

Tam, Hon-Yuen; Cheng, Haobo; Dong, Zhichao

2013-05-20

226

Transient absorption microscopy of monolayer and bulk WSe2.  

PubMed

We present an experimental investigation on the exciton dynamics of monolayer and bulk WSe2 samples, both of which are studied by femtosecond transient absorption microscopy. Under the excitation of a 405 nm pump pulse, the differential reflection signal of a probe pulse (tuned to the A-exciton resonance) reaches a peak rapidly that indicates an ultrafast formation process of excitons. By resolving the differential reflection signal in both time and space, we directly determine the exciton lifetimes of 18±1 and 160±10 ps and the exciton diffusion coefficients of 15±5 and 9±3 cm2/s in the monolayer and bulk samples, respectively. From these values, we deduce other parameters characterizing the exciton dynamics such as the diffusion length, the mobility, the mean free path, and the mean free length. These fundamental parameters are useful for understanding the excitons in monolayer and bulk WSe2 and are important for applications in optoelectronics, photonics, and electronics. PMID:24547746

Cui, Qiannan; Ceballos, Frank; Kumar, Nardeep; Zhao, Hui

2014-03-25

227

The effects of random path fluctuations on the accuracy of laser ranging systems. [statistical analysis of atmospheric turbulence effects on optical paths  

NASA Technical Reports Server (NTRS)

The precision of satellite ranging systems, limited in part by atmospheric refraction and scattering, is examined. The effects of atmospheric turbulence on the accuracy of single color and multicolor ranging systems is discussed. The statistical characteristics of the random path length fluctuations induced by turbulence are examined. Correlation and structure functions are derived using several proposed models for the variations of the optical path length. For single color systems it is shown that the random path length fluctuations can limit the accuracy of a range measurement to a few centimeters. Two color systems can partially correct for the random path fluctuations so that in most cases their accuracy is limited to a few millimeters. However, at low elevation angles and over long horizontal paths two color systems can also have errors approaching a few centimeters.

Gardner, C. S.; Rao, N. N.

1975-01-01

228

Myofilament length dependent activation  

SciTech Connect

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

2010-05-25

229

Length Paradox in Relativity  

ERIC Educational Resources Information Center

Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

Martins, Roberto de A.

1978-01-01

230

Sampling diffusive transition paths  

SciTech Connect

We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.

F. Miller III, Thomas; Predescu, Cristian

2006-10-12

231

A Characteristic Particle Length  

E-print Network

It is argued that there are characteristic intervals associated with any particle that can be derived without reference to the speed of light $c$. Such intervals are inferred from zeros of wavefunctions which are solutions to the Schr\\"odinger equation. The characteristic length is $\\ell=\\beta^2\\hbar^2/(8Gm^3)$, where $\\beta=3.8\\dots$; this length might lead to observational effects on objects the size of a virus.

Mark D. Roberts

2014-06-14

232

Editorial: Redefining Length  

SciTech Connect

Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

Sprouse, Gene D. [American Physical Society (United States)

2011-07-15

233

Object location using path separators  

Microsoft Academic Search

We study a novel separator property called k-path separa- ble. Roughly speaking, a k-path separable graph can be re- cursively separated into smaller components by sequentially removing k shortest paths. Our main result is that every minor free weighted graph is k-path separable. We then show that k-path separable graphs can be used to solve sev- eral object location problems:

Ittai Abraham; Cyril Gavoille

2006-01-01

234

Strength of mineral absorption features in the transmitted component of near-infrared reflected light - First results from RELAB. [spectrogoniometer for planetary and lunar surface composition experiments  

NASA Technical Reports Server (NTRS)

Bidirectional reflectance measurements are the only type of reflectance data available to the remote observer. For compositional interpretations, data are desired not only for identification of possible mineral components but also for modal abundance. The latter requires detailed information about the strength of absorption features. Using a new laboratory facility, the RELAB, laboratory data in the near infrared are presented that document effects of particle size, mineral mixtures, and viewing geometry for selected materials with well-developed absorption bands. The commonly observed increase in reflectance with decrease in particle size is also observed for absorption bands as well as a related decrease in absorption strength. For small particles in parts of the spectrum of maximum reflectance, however, a minor decrease in reflectance with a decrese in particle size is sometimes observed. Small particles dominate the observed characteristics of particulate surfaces, which contain a range of particle sizes. The mean optical path length (transmission through particles) of reflected radiation measured for a variety of particle sizes has an apparent upper limit of about 2 mm for particles of less than 250 microns. The typical number of particles involved in the optical path is less than 50.

Pieters, C. M.

1983-01-01

235

Mobile transporter path planning  

NASA Technical Reports Server (NTRS)

The use of a genetic algorithm (GA) for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the space station which must be able to reach any point of the structure autonomously. Elements of the genetic algorithm are explored in both a theoretical and experimental sense. Specifically, double crossover, greedy crossover, and tournament selection techniques are examined. Additionally, the use of local optimization techniques working in concert with the GA are also explored. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research.

Baffes, Paul; Wang, Lui

1990-01-01

236

APPLYING OPEN-PATH OPTICAL SPECTROSCOPY TO HEAVY-DUTY DIESEL EMISSIONS  

EPA Science Inventory

Non-dispersive infrared absorption has been used to measure gaseous emissions for both stationary and mobile sources. Fourier transform infrared spectroscopy has been used for stationary sources as both extractive and open-path methods. We have applied the open-path method for bo...

237

Collision-free curvature-bounded smooth path planning using composite Bezier curve based on Voronoi diagram  

Microsoft Academic Search

In this paper, we present an obstacle avoiding smooth path planning method based on Voronoi diagram and composite Bezier curve algorithm which obtains the curvature bounded path with small length. In our algorithm, a Voronoi diagram is constructed according to the global environment. The piecewise linear rough path in the Voronoi diagram which keeps away from the obstacles is obtained

Yi-Ju Ho; Jing-Sin Liu

2009-01-01

238

Method for Veterbi decoding of large constraint length convolutional codes  

NASA Technical Reports Server (NTRS)

A new method of Viterbi decoding of convolutional codes lends itself to a pipline VLSI architecture using a single sequential processor to compute the path metrics in the Viterbi trellis. An array method is used to store the path information for NK intervals where N is a number, and K is constraint length. The selected path at the end of each NK interval is then selected from the last entry in the array. A trace-back method is used for returning to the beginning of the selected path back, i.e., to the first time unit of the interval NK to read out the stored branch metrics of the selected path which correspond to the message bits. The decoding decision made in this way is no longer maximum likelihood, but can be almost as good, provided that constraint length K in not too small. The advantage is that for a long message, it is not necessary to provide a large memory to store the trellis derived information until the end of the message to select the path that is to be decoded; the selection is made at the end of every NK time unit, thus decoding a long message in successive blocks.

Hsu, In-Shek (inventor); Truong, Trieu-Kie (inventor); Reed, Irving S. (inventor); Jing, Sun (inventor)

1988-01-01

239

Tunable fiber ring laser absorption spectroscopic sensors for gas detection  

NASA Astrophysics Data System (ADS)

Fiber-optic gas sensing techniques are commonly based on the recognition of a wide range of chemical species from characteristic absorption, fluorescence or Raman-scattering spectra signatures. By tuning over the vibrational lines of species in the path of laser beam, tunable diode laser gas sensors measure signal spectroscopic intensity, gas concentration, and other properties. However, they have limitations of bulk architecture, small change of signal on top of large background, and low sensitivity of direct absorption. Here we report the fabrication and optical measurements of tunable Er-doped fiber ring laser absorption spectroscopic sensor featuring a gas cell that is a segment of photonic crystal fiber (PCF) with a long-period grating (LPG) inscribed. The tunable laser beam is coupled into the cladding of the PCF by the LPG where the gas in air holes absorbs light. The light travels along the PCF cladding and reflects at the end of the fiber where a silver film is coated as a mirror at one end facet. The light propagates back within cladding and passes through the gas one more time thus increasing the interaction length. This light is finally recoupled into the fiber core for intensity measurement. The proposed fiber gas sensors have been experimentally used for ammonia (NH3) concentration detection. They show excellent sensitivity and selectivity, and are minimally affected by temperature and/or humidity changes. The sensors using PCF-LPG gas cell are simple to fabricate, cost-effective, and are deployed for a variety of applications not possible using conventional optical fibers.

Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

2013-04-01

240

Gas path seal  

NASA Technical Reports Server (NTRS)

A gas path seal suitable for use with a turbine engine or compressor is described. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor bades. A compliant backing surrounds the shroud. The backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.

Bill, R. C.; Johnson, R. D. (inventors)

1979-01-01

241

DNA Computing Hamiltonian path  

E-print Network

2014 DNA DNA #12;DNA Computing · Feynman · Adleman · DNASIMD · ... · · · · · DNADNA #12;DNA · DNA · · · · DNA · · #12;2000 2005 2010 1995 Hamiltonian path DNA tweezers DNA tile DNA origami DNA box Sierpinski DNA tile self assembly DNA logic gates Whiplash PCR DNA automaton DNA spider MAYA

Hagiya, Masami

242

Off the Beaten Path.  

ERIC Educational Resources Information Center

Describes "Off the Beaten Path", a program that takes at-risk students out of the traditional classroom and puts them into a camping atmosphere in order to increase academic achievement, improve self-esteem, and promote better social skills. (WRM)

Grimm, Karen

1999-01-01

243

Frugality in path auctions  

Microsoft Academic Search

We consider the problem of picking (buying) an inexpensive s -- t path in a graph where edges are owned by independent (selfish) agents, and the cost of an edge is known to its owner only. We study the problem of finding frugal mechanisms for this task, i.e. we investigate the payments the buyer must make in order to buy

Edith Elkind; Amit Sahai; Kenneth Steiglitz

2004-01-01

244

Paths to Teaching.  

ERIC Educational Resources Information Center

This report uses the national Baccalaureate and Beyond longitudinal database to look at the early career paths of 1993 college graduates. The results provide information on which college graduates became teachers, where they taught, and whether they left teaching within 3 years. Overall, it is not easy to predict who may be potential teachers when…

Lee, John B.; Clery, Suzanne B.; Presley, Jennifer B.

245

Path to the Profession  

ERIC Educational Resources Information Center

A growing number of institutions are being more deliberate about bringing in fundraisers who fit the culture of the development department and about assessing skills and providing training that fill specific needs. Development shops are paying more attention to cultivating their staffs, staying attuned to employees' needs and creating career paths

Coleman, Toni

2012-01-01

246

Paths to Remarriage  

Microsoft Academic Search

High divorce rates and the traditionally discrepant ages at death for husbands and wives indicate a need for a more complete understanding of the paths to remarriage in contemporary America. This study uses data from the U.S. Bureau of the Census' Current Population Survey to examine the extent and timing of remarriage, social factors associated with remarriage, and the impact

Graham B. Spanier; Paul C. Glick

1980-01-01

247

Relativistic Length Agony Continued  

NASA Astrophysics Data System (ADS)

We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

Redzic, D. V.

2014-06-01

248

Probing local structure of pyrochlore lead zinc niobate with synchrotron x-ray absorption spectroscopy technique  

NASA Astrophysics Data System (ADS)

Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn2+ substituted on Nb5+ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn2+ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn2+ and Pb2+ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn2+'s neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb2+ lone pair, as the perovskite phase has shorter Zn2+ to Pb2+ bonding. This therefore suggests the steric hindrance of Pb2+ lone pair and the mutual interactions between Pb2+ lone pair and Zn2+ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials.

Kanchiang, Kanokwan; Pramchu, Sittichain; Yimnirun, Rattikorn; Pakawanit, Phakkhananan; Ananta, Supon; Laosiritaworn, Yongyut

2013-08-01

249

An Optimal Level of Adding Edges for a Simple Path to a Complete K-ary Tree  

NASA Astrophysics Data System (ADS)

This study proposes a model of adding edges of forming a simple path to a level of depth N in a complete K-ary (K?3) tree of height H under giving priority to edges between two nodes of which the deepest common ancestor is deeper. An optimal depth N* is obtained by maximizing the total shortening path length which is the sum of shortening lengths of shortest paths between every pair of all nodes in the complete K-ary tree.

Sawada, Kiyoshi

2010-10-01

250

Lengths of Ladybugs  

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "Ladybug on the Move" by Richard Fowler and measure the distance the ladybug travels on each page using yarn. Next, learners make their own "Go Ladybug Go!" books and use lima beans and a ladybug ruler to make and record measurements.

2012-09-18

251

Length, Perimeter, and Area  

NSDL National Science Digital Library

This lesson is designed to introduce students to the concepts of length, perimeter, and area. This lesson provides links to discussions and activities related to perimeter and area as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with learning about perimeter and area.

2011-01-20

252

Mappability and read length  

PubMed Central

Power-law distributions are the main functional form for the distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size of fragments and reads may prevent an unique alignment of repeat sequences to the reference sequence. Repeats in the human genome can be as long as 104 bases, or 105 ? 106 bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of 103 bases. With a read length of 1000 bases, slightly more than 1% of the assembled genome, and slightly less than 1% of the 1 kb reads, are unmappable, excluding the unassembled portion of the human genome (8% in GRCh37/hg19). The slow decay (long tail) of the power-law function implies a diminishing return in converting unmappable regions/reads to become mappable with the increase of the read length, with the understanding that increasing read length will always move toward the direction of 100% mappability. PMID:25426137

Li, Wentian; Freudenberg, Jan

2014-01-01

253

A predictive model of backscattering at subdiffusion length scales  

PubMed Central

We provide a methodology for accurately predicting elastic backscattering radial distributions from random media with two simple empirical models. We apply these models to predict the backscattering based on two classes of scattering phase functions: the Henyey-Greenstein phase function and a generalized two parameter phase function that is derived from the Whittle-Matérn correlation function. We demonstrate that the model has excellent agreement over all length scales and has less than 1% error for backscattering at subdiffusion length scales for tissue-relevant optical properties. The presented model is the first available approach for accurately predicting backscattering at length scales significantly smaller than the transport mean free path. PMID:21258528

Turzhitsky, Vladimir; Radosevich, Andrew; Rogers, Jeremy D.; Taflove, Allen; Backman, Vadim

2010-01-01

254

Path allocation for wavelength path sharing University College London  

E-print Network

: Wavelength path sharing (WPS) was introduced previously as a means of bridging the gap between the bit answers can be found depending upon the method used for the comparison. 2. Wavelength path sharing (WPS A logical path segment between WPS nodes S & T being transparently routed through X. Key #12;2 shows

Haddadi, Hamed

255

Gas cell for in situ soft X-ray transmission-absorption spectroscopy of materials  

NASA Astrophysics Data System (ADS)

A simple gas cell design, constructed primarily from commercially available components, enables in situ soft X-ray transmission-absorption spectroscopy of materials in contact with gas at ambient temperature. The cell has a minimum X-ray path length of 1 mm and can hold gas pressures up to ˜300 Torr, and could support higher pressures with simple modifications. The design enables cycling between vacuum and gas environments without interrupting the X-ray beam, and can be fully sealed to allow for measurements of air-sensitive samples. The cell can attach to the downstream port of any appropriate synchrotron beamline, and offers a robust and versatile method for in situ measurements of certain materials. The construction and operation of the cell are discussed, as well as sample preparation and proper spectral analysis, illustrated by examples of spectral measurements. Potential areas for improvement and modification for specialized applications are also mentioned.

Drisdell, W. S.; Kortright, J. B.

2014-07-01

256

Sensitive absorption measurements of hydrogen sulfide at 1.578 ?m using wavelength modulation spectroscopy  

NASA Astrophysics Data System (ADS)

Sensitive detection of hydrogen sulfide (H2S) has been performed by means of wavelength modulation spectroscopy (WMS) near 1.578 ?m. With the scan amplitude and the stability of the background baseline taken into account, the response time is 4 s for a 0.8 L multi-pass cell with a 56.7 m effective optical path length. Moreover, the linearity has been tested in the 0–50 ppmv range. The detection limit achievable by the Allan variance is 224 ppb within 24 s under room temperature and ambient pressure conditions. This tunable diode laser absorption spectroscopy (TDLAS) system for H2S detection has the feasibility of real-time online monitoring in many applications. Project supported by the Special Fund for Basic Research on Scientific Instruments of the Chinese Academy of Sciences (Grant No. YZ201315) and the National Natural Science Foundation of China (Grant Nos. 11204320, 41405034, and 11204319).

Xia, Hua; Dong, Feng-Zhong; Wu, Bian; Zhang, Zhi-Rong; Pang, Tao; Sun, Peng-Shuai; Cui, Xiao-Juan; Han, Luo; Wang, Yu

2015-03-01

257

Effective utilization of quantum-cascade distributed-feedback lasers in absorption spectroscopy  

NASA Technical Reports Server (NTRS)

A variable duty cycle quasi-cw frequency scanning technique was applied to reduce thermal effects resulting from the high heat dissipation of type I quantum-cascade lasers. This technique was combined with a 100-m path-length multipass cell and a zero-air background-subtraction technique to enhance detection sensitivity to a parts-in-10(9) (ppb) concentration level for spectroscopic trace-gas detection of CH4, N2O, H2O, and C2H5OH in ambient air at 7.9 micrometers. A new technique for analysis of dense high resolution absorption spectra was applied to detection of ethanol in ambient air, yielding a 125-ppb detection limit.

Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.

2000-01-01

258

Improving accuracy and precision in estimating fractal dimension of animal movement paths.  

PubMed

It is difficult to watch wild animals while they move, so often biologists analyse characteristics of animal movement paths. One common path characteristic used is tortuousity, measured using the fractal dimension (D). The typical method for estimating fractal D, the divider method, is biased and imprecise. The bias occurs because the path length is truncated. I present a method for minimising the truncation error. The imprecision occurs because sometimes the divider steps land inside the bends of curves, and sometimes they miss the curves. I present three methods for minimising this variation and test the methods with simulated correlated random walks. The traditional divider method significantly overestimates fractal D when paths are short and the range of spatial scales is narrow. The best method to overcome these problems consists of walking the dividers forwards and backwards along the path, and then estimating the path length remaining at the end of the last divider step. PMID:16823606

Nams, Vilis O

2006-01-01

259

Material Effects and Detector Response Corrections for Bunch Length Measurements  

SciTech Connect

A typical diagnostic used to determine the bunch length of ultra-short electron bunches is the auto-correlation of coherent transition radiation. This technique can produce artificially short bunch length results due to the attenuation of low frequency radiation if corrections for the material properties of the Michelson interferometer and detector response are not made. Measurements were taken using FTIR spectroscopy to determine the absorption spectrum of various materials and the response of a Molectron P1-45 pyroelectric detector. The material absorption data will be presented and limitations on the detector calibration discussed.

Zacherl, W.; Blumenfeld, I.; Berry, M.; Decker, F.-J.; Hogan, M.J.; Ischebeck, R.; Iverson, R.; Kirby, N.; Siemann, R.; Walz, D.; /SLAC; Clayton, C.E.; Huang, C.; Joshi, C.; Lu, W.; Marsh, K.A.; Mori, W.B.; Zhou, M.; /UCLA; Katsouleas, T.C.; Muggli, P.; Oz, E.; /Southern California U.

2007-06-28

260

PATHS groundwater hydrologic model  

SciTech Connect

A preliminary evaluation capability for two-dimensional groundwater pollution problems was developed as part of the Transport Modeling Task for the Waste Isolation Safety Assessment Program (WISAP). Our approach was to use the data limitations as a guide in setting the level of modeling detail. PATHS Groundwater Hydrologic Model is the first level (simplest) idealized hybrid analytical/numerical model for two-dimensional, saturated groundwater flow and single component transport; homogeneous geology. This document consists of the description of the PATHS groundwater hydrologic model. The preliminary evaluation capability prepared for WISAP, including the enhancements that were made because of the authors' experience using the earlier capability is described. Appendixes A through D supplement the report as follows: complete derivations of the background equations are provided in Appendix A. Appendix B is a comprehensive set of instructions for users of PATHS. It is written for users who have little or no experience with computers. Appendix C is for the programmer. It contains information on how input parameters are passed between programs in the system. It also contains program listings and test case listing. Appendix D is a definition of terms.

Nelson, R.W.; Schur, J.A.

1980-04-01

261

Muscle paths in biomechanical multibody simulations Ramona Maas1  

E-print Network

Muscle paths in biomechanical multibody simulations Ramona Maas1 , Sigrid Leyendecker1 1 Chair, the actuation of those systems can be implemented via Hill-type muscle models. The essential task of these models is to represent the typical force-length and force-velocity relation of real muscles, hence

Leyendecker, Sigrid

262

Dynamic path planning in sensor-based terrain acquisition  

Microsoft Academic Search

The terrain acquisition problem is formulated as that of continuous motion planning, and no constraints are imposed on obstacle geometry. Two algorithms are described for acquiring planar terrains with obstacles of arbitrary shape. Estimates of the algorithm performance are derived as upper bounds on the lengths of generated paths

V. J. Lumelsky; S. Mukhopadhyay; K. Sun

1990-01-01

263

Quantum cascade laser-based multipass absorption system for hydrogen peroxide detection  

NASA Astrophysics Data System (ADS)

Hydrogen peroxide (H2O2) is a relevant molecular trace gas species, that is related to the oxidative capacity of the atmosphere, the production of radical species such as OH, the generation of sulfate aerosol via oxidation of S(IV) to S(VI), and the formation of acid rain. The detection of atmospheric H2O2 involves specific challenges due to its high reactivity and low concentration (ppbv to sub-ppbv level). Traditional methods for measuring atmospheric H2O2 concentration are often based on wet-chemistry methods that require a transfer from the gas- to liquid-phase for a subsequent determination by techniques such as fluorescence spectroscopy, which can lead to problems such as sampling artifacts and interference by other atmospheric constituents. A quartz-enhanced photoacoustic spectroscopy-based system for the measurement of atmospheric H2O2 with a detection limit of 75 ppb for 1-s integration time was previously reported. In this paper, an updated H2O2 detection system based on long-optical-path-length absorption spectroscopy by using a distributed feedback quantum cascade laser (DFB-QCL) will be described. A 7.73-?m CW-DFB-QCL and a thermoelectrically cooled infrared detector, optimized for a wavelength of 8 ?m, are employed for theH2O2 sensor system. A commercial astigmatic Herriott multi-pass cell with an effective optical path-length of 76 m is utilized for the reported QCL multipass absorption system. Wavelength modulation spectroscopy (WMS) with second harmonic detection is used for enhancing the signal-to-noise-ratio. A minimum detection limit of 13.4 ppb is achieved with a 2 s sampling time. Based on an Allan-Werle deviation analysis the minimum detection limit can be improved to 1.5 ppb when using an averaging time of 300 s.

Cao, Yingchun; Sanchez, Nancy P.; Jiang, Wenzhe; Ren, Wei; Lewicki, Rafal; Jiang, Dongfang; Griffin, Robert J.; Tittel, Frank K.

2015-01-01

264

Cooperative Coevolutionary Adaptive Genetic Algorithm in Path Planning of Cooperative Multi-Mobile Robot Systems  

Microsoft Academic Search

In this paper, path planning of cooperative multi-mobile robot systems, an example of multi-agent systems, is discussed with the proposal of a novel Cooperative Coevolutionary Adaptive Genetic Algorithm (CCAGA). At the same time, for such genetic algorithms based path planning, a novel fixed-length decimal encoding mechanism for paths of each mobile robot is also proposed. Such cooperative coevolutionary adaptive genetic

Zixing Cai; Zhihong Peng

2002-01-01

265

Vowel length in Farsi  

NASA Astrophysics Data System (ADS)

This study tests whether Farsi vowels are contrastive with respective to length. Farsi has a six-vowel system with three lax vowels and three tense vowels. Both traditional grammarians and modern linguists believe that Farsi tense vowels are longer than lax vowels, and that there are no vowel pairs that contrast only in length. However, it has been suggested that Farsi exhibits compensatory lengthening, which is triggered by the deletion of glottal consonants in coda position in informal speech (Darzi, 1991). As a result, minimal pairs such as [tar] and [tarh] should contrast only with respect to vowel length. A corpus of 90 words of the form CVC, CVCG, CVGC, and CVCC (where V=a vowel and G=a glottal consonant) was recorded, and durations of vowels in different contexts were measured and compared. Preliminary results show that lax vowel durations fall into three groups with CVCC longer than CVCG/CVGC, and the latter longer than CVC. It remains to be seen whether CVCG/CVGC words show compensatory lengthening when the glottal consonant is deleted.

Shademan, Shabnam

2001-05-01

266

Lengthy Relationships: Foot Length, Stride, Leg Length, Height  

NSDL National Science Digital Library

Paleontologists occasionally find ancient tracks and footprints preserved in the rocks. This lesson opens the door to analysing those footprints, and gleaning information about body size and activities of the extinct animals that made the tracks. Students will learn that patterns can reveal much about the past, in light of the present; and that bipedalism has appeared several times. Relationships will be found between foot length and leg length; foot length and height; leg length and height; stride length and leg length; and stride length and speed.

Jennifer Johnson

267

Shortest paths in the Tower of Hanoi graph and finite automata  

Microsoft Academic Search

We present efficient algorithms for constructing a shortest path be- tween two states in the Tower of Hanoi graph, and for computing the length of the shortest path. The key element is a finite-state machine which decides, after examining on the average only 63 38 ? 1.66 of the largest discs, whether the largest disc will be moved once or

Dan Romik

2003-01-01

268

Transitional Information in Spatial Serial Memory: Path Characteristics Affect Recall Performance  

ERIC Educational Resources Information Center

This study examined the role of stimulus characteristics in a visuospatial order reconstruction task in which participants were required to recall the order of sequences of spatial locations. The complexity of the to-be-remembered sequences, as measured by path crossing, path length, and angles, was found to affect serial memory, in terms of both…

Parmentier, Fabrice B. R.; Elford, Greg; Mayberry, Murray

2005-01-01

269

Limited path entanglement percolation in quantum complex networks  

E-print Network

We study entanglement distribution in quantum complex networks where nodes are connected by bipartite entangled states. These networks are characterized by a complex structure, which dramatically affects how information is transmitted through them. For pure quantum state links, quantum networks exhibit a remarkable feature absent in classical networks: it is possible to effectively rewire the network by performing local operations on the nodes. We propose a family of such quantum operations that decrease the entanglement percolation threshold of the network and increase the size of the giant connected component. We provide analytic results for complex networks with arbitrary (uncorrelated) degree distribution. These results are in good agreement with numerical simulations, which also show enhancement in correlated and real world networks. The proposed quantum preprocessing strategies are not robust in the presence of noise. However, even when the links consist of (noisy) mixed state links, one can send quantum information through a connecting path with a fidelity that decreases with the path length. In this noisy scenario, complex networks offer a clear advantage over regular lattices, namely the fact that two arbitrary nodes can be connected through a relatively small number of steps, known as the small world effect. We calculate the probability that two arbitrary nodes in the network can successfully communicate with a fidelity above a given threshold. This amounts to working out the classical problem of percolation with limited path length. We find that this probability can be significant even for paths limited to few connections, and that the results for standard (unlimited) percolation are soon recovered if the path length exceeds by a finite amount the average path length, which in complex networks generally scales logarithmically with the size of the network.

Martí Cuquet; John Calsamiglia

2010-11-25

270

Signatures of Absorption Mechanisms for J{psi} and {psi}` Production in High Energy Heavy-Ion Collisions  

SciTech Connect

J/psi and psi` produced in high-energy heavy-ion collisions are absorbed by their collisions with nucleons and produced soft particles, leading to two distinct absorption mechanisms. The signature of absorption by produced soft particles, as revealed by psi` production data, consists of a gap and a change of the slope in going from the pA line to the nucleus-nucleus line when we make a semi-log plot of the survival probability as a function of the path length. Using this signature, we find from the J/psi production data in pA, O-Cu, O-U, and S-U collisions that the degree of J/psi absorption by produced soft particles is small and cannot account for the J/psi data in Pb-Pb collisions. The anomalous suppression of J/psi production in Pb-Pb collisions can be explained as due to the occurrence of a new phase of strong J/psi absorption, which sets in when the local energy density exceeds about 3.4 GeV/fm3. To probe the chemical content of the new phase, we propose to study the abundance of open-charm mesons and charm hyperons which depends sensitively on the quark chemical potential.

Wong, Cheuk-Yin

1997-06-01

271

Sensor for headspace pressure and H2O concentration measurements in closed vials by tunable diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The concentration of H2O and the pressure in the headspace of vials are simultaneously measured by a tunable diode laser sensor based on absorption spectroscopy techniques. The 7168.437 cm-1 spectral line of H2O is chosen as the sensing transition for its strong absorption strength and being reasonably far away from its neighboring molecular transitions. In order to prevent interference absorption by ambient water vapor in the room air, a difference between the measured signal and the referenced signal is used to calculate the pressure and H2O concentration in the headspace of vials, eliminating the need for inert gas purges and calibration with known gas. The validation of the sensor is conducted in a static vial, yielding an accuracy of 1.23% for pressure and 3.81% for H2O concentration. The sensitivity of the sensor is estimated to be about 2.5 Torr for pressure and 400 ppm for H2O concentration over a 3 cm absorption path length respectively. Accurate measurements for commercial freeze-dried products demonstrate the in-line applications of the sensor for the pharmaceutical industry.

Cai, Tingdong; Wang, Guishi; Cao, Zhensong; Zhang, Weijun; Gao, Xiaoming

2014-07-01

272

Laser differential confocal ultra-long focal length measurement.  

PubMed

A new laser differential confocal focal-length measurement method is proposed for the measurement of an ultra-long focal-length. The approach proposed uses the property of an axial intensity curve that the absolute zero precisely corresponds to the focus of the objective in a differential confocal focusing system (DCFS) to measure the variation in position of DCFS focus with and without a measured ultra-long focal-length lens (UFL), uses the distance between the two focuses to obtain the UFL focal-length, and thereby achieving the precise measurement of ultra-long focal-length. The method has a high focusing precision, a strong anti-interference capability and a short measurement light-path. The theoretical analyses and preliminary experimental results indicate that the relative measurement error is about 0.01% when the method is used for the measurement of back-focus-distance (BFD). PMID:19997229

Zhao, Weiqian; Sun, Ruoduan; Qiu, Lirong; Sha, Dingguo

2009-10-26

273

Automated continuous monitoring of inorganic and total mercury in wastewater and other waters by flow-injection analysis and cold-vapour atomic absorption spectrometry  

PubMed Central

An automated continuous monitoring system for the determination of inorganic and total mercury by flow-injection analysis followed by cold-vapour atomic absorption spectrometry is described. The method uses a typical flow-injection manifold where digestion and reduction of the injected sample takes place. Mercury is removed by aeration from the flowing stream in a specially designed air-liquid separator and swept into a silica cell for absorption measurement at a wavelength of 253.7 nm. A calibration curve up to 10 ?g Hg ml-1 using three different path length cells is obtained with a detection limit of 0.02 ?g Hg ml-1. The sampling rate of an injection every 3 min produces 20 results per hour from a flowing stream. PMID:18925201

Birnie, S. E.

1988-01-01

274

Essential paths space on ADE SU(3) graphs: A geometric approach  

E-print Network

Using triangular sequences of vertices as an analogue for a backtracking step on a path in SU(3), we offer a geometric understanding of the path creation and annihilation operators in terms of creation and annihilation of triangular sequences of vertices. We find that our implementation of these operators yields the expected mathematical properties as applied to essential and non essential paths. We prove that the space of paths of a given length can be decomposed in a way similar to that shown previously for SU(2), which is to say that one can write a path of a given length as a direct sum of sub-spaces which are ortogonal subspaces constructed by recurrent applications of the path creation operator on subspaces of essential paths of shorter length. We propose an algorithm that shows explicitly how a given path can be obtained as an interated and ordered application of the creation operator on a path belonging to the kernel of the annihilation operator.

Jesus A. Pineda; E. Isasi; M. I. Caicedo

2014-07-10

275

Tracking hurricane paths  

NASA Technical Reports Server (NTRS)

The South East coastal region experiences hurricane threat for almost six months in every year. To improve the accuracy of hurricane forecasts, meteorologists would need the storm paths of both the present and the past. A hurricane path can be established if we could identify the correct position of the storm at different times right from its birth to the end. We propose a method based on both spatial and temporal image correlations to locate the position of a storm from satellite images. During the hurricane season, the satellite images of the Atlantic ocean near the equator are examined for the hurricane presence. This is accomplished in two steps. In the first step, only segments with more than a particular value of cloud cover are selected for analysis. Next, we apply image processing algorithms to test the presence of a hurricane eye in the segment. If the eye is found, the coordinate of the eye is recorded along with the time stamp of the segment. If the eye is not found, we examine adjacent segments for the existence of hurricane eye. It is probable that more than one hurricane eye could be found from different segments of the same period. Hence, the above process is repeated till the entire potential area for hurricane birth is exhausted. The subsequent/previous position of each hurricane eye will be searched in the appropriate adjacent segments of the next/previous period to mark the hurricane path. The temporal coherence and spatial coherence of the images are taken into account by our scheme in determining the segments and the associated periods required for analysis.

Prabhakaran, Nagarajan; Rishe, Naphtali; Athauda, Rukshan

1997-01-01

276

Length of the Day  

NSDL National Science Digital Library

In this activity, students measure the length of the day using the rotation of the Earth, and discover that the Sun is not exactly in the same place at the same clock time every day, understand that the changes are due to motions of the Earth, and lead to differences in solar, star, and sidereal time. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

277

Oral Drug Absorption  

E-print Network

properties ? membrane permeability ? metabolic stability ? enzyme inhibition or induction ? protein binding ? transporter affinity ?. Chemical Optimization DDS technology 4 Strategy of Drug Delivery Absorption Distribution Metabolism Excretion Improve of drug... absorption absorption enhancement controlled releasecontrolled release new administration route Drug targeting to the tissue to the cell to the organelle Dr. Shinji Yamashita (Setsunan University) Issue: Oral Drug Absorption Dr. Valentino J. Stella...

Yamashita, Shinji

2006-10-26

278

The California PATH Database  

NSDL National Science Digital Library

The well known Berkeley Digital Library SunSite, discussed in the February 9, 1996 Scout Report, has recently added a new resource to its collection. The PATH database, maintained by the Harmer E. Davis Transportation Library at the University of California, is "the world's largest bibliographical database pertaining to Intelligent Transportation Systems (ITS)." It is searchable and browsable (Browse by ITS Thesaurus Term), and contains over 9,000 records and abstracts "including monographs, journal articles, conference papers, technical reports, theses and selected media coverage," dating back to the 1940s.

279

JAVA PathFinder  

NASA Technical Reports Server (NTRS)

JPF is an explicit state software model checker for Java bytecode. Today, JPF is a swiss army knife for all sort of runtime based verification purposes. This basically means JPF is a Java virtual machine that executes your program not just once (like a normal VM), but theoretically in all possible ways, checking for property violations like deadlocks or unhandled exceptions along all potential execution paths. If it finds an error, JPF reports the whole execution that leads to it. Unlike a normal debugger, JPF keeps track of every step how it got to the defect.

Mehhtz, Peter

2005-01-01

280

Pick-a-Path  

NSDL National Science Digital Library

This mobile app (available for both iOS and Android devices) was developed by the National Council of Teachers of Mathematics with funding from Verizon Foundation. The app is based on the Decimal Maze from the popular lesson "Too Big or Too Small". The goal is to help Okta reach the target (maximum, minimum, or a specific value) by choosing a path from the top of the maze to the bottom — adding, subtracting, multiplying and dividing as the player goes. Seven levels with seven puzzles in each level test the player's skills with operation with powers of ten, negative numbers, fractions, decimals, and exponents.

2012-01-01

281

Portage and Path Dependence*  

PubMed Central

We examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphological feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, we document the continuing importance of these portage sites over time. We interpret these results as path dependence and contrast explanations based on sunk costs interacting with decreasing versus increasing returns to scale. PMID:23935217

Bleakley, Hoyt; Lin, Jeffrey

2012-01-01

282

Byrds Flight Path  

NSDL National Science Digital Library

The Ohio State Universitys Library web site notes As a navigational aviator, Byrd pioneered in the technology that would be the foundation for modern polar exploration and investigation. As a decorated and much celebrated hero, Byrd drew popular attention to areas of the world that became focal points of scientific investigation in numerous disciplines. More information about Admiral Richard E. Byrd can be found at (http:--www.lib.ohio-state.edu-arvweb-polar-byrd-byrd.htm). The next animation, #1001, shows Byrds plane as it follows the flight path presented in this animation.

Tom Biddlecome

1999-11-08

283

Infrared absorption of carbon dioxide at high densitites with application to the atmosphere of Venus. Ph.D. Thesis - Columbia Univ.  

NASA Technical Reports Server (NTRS)

Several new infrared absorptions were found in carbon dioxide. All are normally forbidden, and were collision-induced in an absorbing cell whose combination of pressure and path length has a unique sensitivity for induced absorptions. The new absorptions in the 2.3 micron region are attributed to transitions from ground to the 3(1)1 Fermi pair at 4248 and 4391/cm. Other absorptions are attributed to simultaneous CO2-N2 transitions and to the 00(0)0-00(0)2 transition in CO2 polarizability derivatives and regular progressions in strength versus increasing quantum number. The spectra were used to predict the radiative transfer in a dry CO2 model of the lower Venus atmosphere. The results indicate that the radiation balance in the lower atmosphere is adequately explained by a dry massive atmosphere of CO2 with a layer of infrared-opaque clouds. The absorptions in the 2.3 micron region are significant in accounting for the opacity to sustain Venus' 768 K surface temperature.

Moore, J. F.

1971-01-01

284

Kinetic paths, time scale, and underlying landscapes: A path integral framework to study global natures of nonequilibrium systems and networks  

NASA Astrophysics Data System (ADS)

We developed a general framework to quantify three key ingredients for dynamics of nonequilibrium systems through path integrals in length space. First, we identify dominant kinetic paths as the ones with optimal weights, leading to effective reduction of dimensionality or degrees of freedom from exponential to polynomial so large systems can be treated. Second, we uncover the underlying nonequilibrium potential landscapes from the explorations of the state space through kinetic paths. We apply our framework to a specific example of nonequilibrium network system: lambda phage genetic switch. Two distinct basins of attractions emerge. The dominant kinetic paths from one basin to another are irreversible and do not follow the usual steepest descent or gradient path along the landscape. It reflects the fact that the dynamics of nonequilibrium systems is not just determined by potential gradient but also the residual curl flux force, suggesting experiments to test theoretical predictions. Third, we have calculated dynamic transition time scales from one basin to another critical for stability of the system through instantons. Theoretical predictions are in good agreements with wild type and mutant experiments. We further uncover the correlations between the kinetic transition time scales and the underlying landscape topography: the barrier heights along the dominant paths. We found that both the dominant paths and the landscape are relatively robust against the influences of external environmental perturbations and the system tends to dissipate less with less fluctuations. Our general framework can be applied to other nonequilibrium systems.

Wang, Jin; Zhang, Kun; Wang, Erkwang

2010-09-01

285

Length of stain dosimeter  

NASA Technical Reports Server (NTRS)

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

Lueck, Dale E. (inventor)

1994-01-01

286

Path Integral Bosonization  

E-print Network

We establish the direct $d=2$ on-shell bosonization $\\psi_{L}(x_{+}) = e^{i\\xi(x_{+})}$ and~$\\psi_{R}^{\\dagger}(x_{-}) = e^{i\\xi(x_{-})}$ in path integral formulation by deriving the off-shell relations $\\psi_{L}(x)\\psi_{R}^{\\dagger}(x) = \\exp[i\\xi(x)]$ and $\\psi_{R}(x)\\psi_{L}^{\\dagger}(x) = \\exp[-i\\xi(x)]$. Similarly, the on-shell bosonization of the bosonic commuting spinor, $\\phi_{L}(x_{+}) = ie^{-i\\xi(x_{+})}\\partial^{+}e^{-i\\chi(x_{+})}$, $\\phi^{\\dagger}_{R}(x_{-}) = e^{-i\\xi(x_{-})-i\\chi(x_{-})}$ and $\\phi_{R}(x_{-}) = ie^{i\\xi(x_{-})}\\partial^{-}e^{+i\\chi(x_{-})}$, $\\phi^{\\dagger}_{L}(x_{+}) = e^{i\\xi(x_{+})+i\\chi(x_{+})}$, is established in path integral formulation by deriving the off-shell relations $\\phi_{L}(x)\\phi^{\\dagger}_{R}(x) = ie^{-i\\xi(x)}\\partial^{+}e^{-i\\chi(x)}$ and $\\phi_{R}(x)\\phi^{\\dagger}_{L}(x) = ie^{i\\xi(x)}\\partial^{-}e^{i\\chi(x)}$.

Fujikawa, Kazuo

2015-01-01

287

More precise determination of thermal lens focal length for end-pumped solid-state lasers  

Microsoft Academic Search

A method of more precise determination of the focal length of equivalent thermal lens (TL) is presented in this paper. The method is based on the diffraction theory of aberrations. By numerically calculating the optical path difference (OPD) distribution and the Strehl ratio, the focal lengths for “top-hat” pumping and Gaussian pumping are obtained and the equations for the focal

Shuzhen Fan; Xingyu Zhang; Qingpu Wang; Shutao Li; Shuanghong Ding; Fufang Su

2006-01-01

288

Cavity ring-down spectroscopy (CRDS) system for measuring atmospheric mercury using differential absorption  

NASA Astrophysics Data System (ADS)

Atmospheric elemental mercury (Hg0) is a globally pervasive element that can be transported and deposited to remote ecosystems where it poses — particularly in its methylated form — harm to many organisms including humans. Current techniques for measurement of atmospheric Hg0 require several liters of sample air and several minutes for each analysis. Fast-response (i.e., 1 second or faster) measurements would improve our ability to understand and track chemical cycling of mercury in the atmosphere, including high frequency Hg0 fluctuations, sources and sinks, and chemical transformation processes. We present theory, design, challenges, and current results of our new prototype sensor based on cavity ring-down spectroscopy (CRDS) for fast-response measurement of Hg0 mass concentrations. CRDS is a direct absorption technique that implements path-lengths of multiple kilometers in a compact absorption cell using high-reflectivity mirrors, thereby improving sensitivity and reducing sample volume compared to conventional absorption spectroscopy. Our sensor includes a frequency-doubled, dye-laser emitting laser pulses tunable from 215 to 280 nm, pumped by a Q-switched, frequency tripled Nd:YAG laser with a pulse repetition rate of 50 Hz. We present how we successfully perform automated wavelength locking and stabilization of the laser to the peak Hg0 absorption line at 253.65 nm using an external isotopically-enriched mercury (202Hg0) cell. An emphasis of this presentation will be on the implementation of differential absorption measurement whereby measurements are alternated between the peak Hg0 absorption wavelength and a nearby wavelength "off" the absorption line. This can be achieved using a piezo electric tuning element that allows for pulse-by-pulse tuning and detuning of the laser "online" and "offline" of the Hg absorption line, and thereby allows for continuous correction of baseline extinction losses. Unexpected challenges with this approach included different efficiencies of laser performance (e.g., frequency doubling) at the two wavelengths and temperature dependence. We will discuss improvements on the control of our system to eliminate drift due to conversion efficiency and temperature dependence. We will detail complications with operating this instrument from a mobile platform for in situ measurements in the field. Finally, we will present data acquisition and processing approaches along with results of calibration curves, and comparisons to conventional mercury analyzers (i.e., a Tekran 2537 mercury vapor analyzer) during ambient air measurements.

Pierce, A.; Obrist, D.; Moosmuller, H.; Moore, C.

2012-04-01

289

Slip length crossover on a graphene surface.  

PubMed

Using equilibrium and non-equilibrium molecular dynamics simulations, we study the flow of argon fluid above the critical temperature in a planar nanochannel delimited by graphene walls. We observe that, as a function of pressure, the slip length first decreases due to the decreasing mean free path of gas molecules, reaches the minimum value when the pressure is close to the critical pressure, and then increases with further increase in pressure. We demonstrate that the slip length increase at high pressures is due to the fact that the viscosity of fluid increases much faster with pressure than the friction coefficient between the fluid and the graphene. This behavior is clearly exhibited in the case of graphene due to a very smooth potential landscape originating from a very high atomic density of graphene planes. By contrast, on surfaces with lower atomic density, such as an (100) Au surface, the slip length for high fluid pressures is essentially zero, regardless of the nature of interaction between fluid and the solid wall. PMID:25854252

Liang, Zhi; Keblinski, Pawel

2015-04-01

290

High pressure in situ x-ray absorption spectroscopy cell for studying simultaneously the liquid phase and the solid-liquid interface  

SciTech Connect

A high pressure in situ x-ray absorption spectroscopy cell with two different path lengths and path positions is presented for studying element-specifically both the liquid phase and the solid-liquid interface at pressures up to 250 bar and temperatures up to 220 deg. C. For this purpose, one x-ray path probes the bottom, while the other x-ray path penetrates through the middle of the in situ cell. The basic design of the cell resembles a 10 ml volume batch reactor, which is equipped with in- and outlet lines to dose compressed gases and liquids as well as a stirrer for good mixing. Due to the use of a polyetheretherketone inset it is also suitable for measurements under corrosive conditions. The characteristic features of the cell are illustrated using case studies from catalysis and solid state chemistry: (a) the ruthenium-catalyzed formylation of an amine in 'supercritical' carbon dioxide in the presence of hydrogen; (b) the cycloaddition of carbon dioxide to propylene oxide in the presence of a solid Zn-based catalyst, and (c) the solvothermal synthesis of MoO{sub 3} nanorods from MoO{sub 3}-2H{sub 2}O.

Grunwaldt, Jan-Dierk; Ramin, Michael; Rohr, Markus; Michailovski, Alexej; Patzke, Greta R.; Baiker, Alfons [Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Hoenggerberg HCI, CH-8093 Zurich (Switzerland)

2005-05-15

291

Quantitative infrared absorption cross sections of isoprene for atmospheric measurements  

NASA Astrophysics Data System (ADS)

Isoprene (C5H8, 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O3-initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600-6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298, and 323 K in a 19.94 cm path-length cell at 0.112 cm-1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.

Brauer, C. S.; Blake, T. A.; Guenther, A. B.; Sharpe, S. W.; Sams, R. L.; Johnson, T. J.

2014-11-01

292

Air quality monitoring with the differential optical absorption spectrometer  

NASA Astrophysics Data System (ADS)

Measurements of gaseous air pollutants over three separate open paths in Atlanta, Georgia, conducted with a differential optical absorption spectrometer (DOAS) during July and August 1990 are reported. Over path 1 (1099 m) and path 2 (1824 m), O3, SO2, NO2, HNO2, HCHO, benzene, toluene, and o-xylene were measured. NO and NH3 were monitored over path 3 (143 m). Federal reference method (FRM) instruments were located near the DOAS light receivers, and measurements of O3, NO2, and NO were made concurrently with the DOAS. Correlation coefficients between the two measurement paths ranged from 0.87 for toluene to 0.99 for ozone. Comparisons between FRM and DOAS for O3, NO2, and NO showed good correlations but some differences in average concentrations, most notably for NO, whose FRM concentrations averaged less than 40 percent of the DOAS concentrations. The advantages of the DOAS system over traditional FRM systems are discussed.

Stevens, Robert K.; Conner, Teri L.

1991-09-01

293

ABSORPTION SPECTRA OF URANYL NITRATE IN ORGANIC SOLVENTS  

Microsoft Academic Search

Optical densities of UOâ(NOâ)â in aqueous HCl(pH 1 to ; 2) saturated with NHâNOâ, 4% orthophosphoric acid and 10% HâSO\\/; sub 4\\/ were measured at various wave lengths in order to compare uranyl nitrate ; absorption spectra in organic solvents with its absorption spectra in aqueous ; solutions. (R.V.J.);

S. I. Sinyakova; N. S. Klassova

1959-01-01

294

Estimation of microwave absorption in the Jupiter atmosphere  

NASA Technical Reports Server (NTRS)

A procedure for estimating the microwave absorption loss of the Jupiter atmosphere is presented. Estimation of microwave absorption by planetary atmospheres involves two different investigative disciplines (1) the determination of an acceptable model of the atmosphere itself and (2) the determination of the microwave attenuation rate applicable to each different volume sample of the atmosphere, and the integration of this loss over the varying radio propagation path for any given entry trajectory to obtain the total loss.

Coombs, W. C.

1971-01-01

295

Flight Paths of Orbiting Satellites  

NSDL National Science Digital Library

This is an activity to help students visualize the relationship of motion, time and space as it relates to objects orbiting the earth. They will be able to track the path of an orbiting object on a globe, plot the path of an orbiting object on a flat world map, and explain that an object orbiting earth on a plane will produce a flight path which appears as wavy lines on the earths surface.

296

Interactive cutting path analysis programs  

NASA Technical Reports Server (NTRS)

The operation of numerically controlled machine tools is interactively simulated. Four programs were developed to graphically display the cutting paths for a Monarch lathe, Cintimatic mill, Strippit sheet metal punch, and the wiring path for a Standard wire wrap machine. These programs are run on a IMLAC PDS-ID graphic display system under the DOS-3 disk operating system. The cutting path analysis programs accept input via both paper tape and disk file.

Weiner, J. M.; Williams, D. S.; Colley, S. R.

1975-01-01

297

Packing paths in digraphs  

E-print Network

f ~P1g, or f ~P1; ~P2g, the G-packing problem is NP-complete. When G = f ~P1g, the G-packing problem is simply the matching problem. We treat in detail the one remaining case, G = f ~P1; ~P2g. We give in this case a polynomial algorithm for the packing problem. We also give the following positive results: a Berge type augmenting configuration theorem, a min-max characterization, and a reduction to bipartite matching. These results apply also to packings by the family G consisting of all directed paths and cycles. We also explore weighted variants of the problem and include a polyhedral analysis.

Richard C. Brewster; Pavol Hell; Sarah H. Pantel; Romeo Rizzi; Anders Yeo

298

Thermoalgebras and path integral  

SciTech Connect

Using a representation for Lie groups closely associated with thermal problems, we derive the algebraic rules of the real-time formalism for thermal quantum field theories, the so-called thermo-field dynamics (TFD), including the tilde conjugation rules for interacting fields. These thermo-group representations provide a unified view of different approaches for finite-temperature quantum fields in terms of a symmetry group. On these grounds, a path integral formalism is constructed, using Bogoliubov transformations, for bosons, fermions and non-abelian gauge fields. The generalization of the results for quantum fields in (S{sup 1}){sup d}xR{sup D-d} topology is addressed.

Khanna, F.C. [Theoretical Physics Institute, University of Alberta, Edmonton, AB T6G 2J1 (Canada); TRIUMF, Vancouver, BC, V6T 2A3 (Canada)], E-mail: khanna@phys.ualberta.ca; Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas/MCT, 22290-180 Rio de Janeiro, RJ (Brazil)], E-mail: adolfo@cbpf.br; Malbouisson, J.M.C. [Instituto de Fisicas, Universidade Federal da Bahia, 40210-340 Salvador, BA (Brazil)], E-mail: jmalboui@ufba.br; Santana, A.E. [Instituto de Fisicas, Universidade de Brasilia, 70910-900 Brasilia, DF (Brazil)], E-mail: asantana@fis.unb.br

2009-09-15

299

Writhe and mutual entanglement combine to give the entanglement length  

NASA Astrophysics Data System (ADS)

We propose a method to estimate Ne, the entanglement length, that incorporates both local and global topological characteristics of chains in a melt under equilibrium conditions. This estimate uses the writhe of the chains, the writhe of the primitive paths, and the number of kinks in the chains in a melt. An advantage of this method is that it works for both linear and ring chains, works under all periodic boundary conditions, does not require knowing the contour length of the primitive paths, and does not rely on a smooth set of data. We apply this method to linear finitely extendable nonlinear elastic chains and we observe that our estimates are consistent with those from other studies.

Panagiotou, E.; Kröger, M.; Millett, K. C.

2013-12-01

300

Sequence length requirements Tandy Warnow  

E-print Network

Sequence length requirements Tandy Warnow Department of Computer Science The University of Texas at Austin #12;Part 1: Absolute Fast Convergence #12;DNA Sequence Evolution AAGACTT TGGACTTAAGGCCT -3 mil yrs convergence (afc) #12;"Convergence rate" or sequence length requirement The sequence length (number of sites

Warnow,Tandy

301

D-xylose absorption  

MedlinePLUS

D-xylose absorption is a laboratory test to determine how well the intestines absorb a simple sugar (D-xylose). The test ... test is primarily used to determine if nutrient absorption problems are due to a disease of the ...

302

Modeling of gas absorption cross sections by use of principal-component-analysis model parameters.  

PubMed

Monitoring the amount of gaseous species in the atmosphere and exhaust gases by remote infrared spectroscopic methods calls for the use of a compilation of spectral data, which can be used to match spectra measured in a practical application. Model spectra are based on time-consuming line-by-line calculations of absorption cross sections in databases by use of temperature as input combined with path length and partial and total pressure. It is demonstrated that principal component analysis (PCA) can be used to compress the spectrum of absorption cross sections, which depend strongly on temperature, into a reduced representation of score values and loading vectors. The temperature range from 300 to 1000 K is studied. This range is divided into two subranges (300-650 K and 650-1000K), and separate PCA models are constructed for each. The relationship between the scores and the temperature values is highly nonlinear. It is shown, however, that because the score-temperature relationships are smooth and continuous, they can be modeled by polynomials of varying degrees. The accuracy of the data compression method is validated with line-by-line-calculated absorption data of carbon monoxide and water vapor. Relative deviations between the absorption cross sections reconstructed from the PCA model parameters and the line-by-line-calculated values are found to be smaller than 0.15% for cross sections exceeding 1.27 x 10(-21) cm(-1) atm(-1) (CO) and 0.20% for cross sections exceeding 4.03 x 10(-21) cm(-1) atm(-1) (H2O). The computing time is reduced by a factor of 10(4). PMID:12027171

Bak, Jimmy

2002-05-20

303

Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution  

SciTech Connect

This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm Multiplication-Sign 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45 Degree-Sign beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

Laroche, G. [Laboratoire d'Ingenierie de Surface, Centre de Recherche sur les Materiaux Avances, Departement de genie des mines, de la metallurgie et des materiaux, Universite Laval, 1065, avenue de la Medecine, Quebec G1V 0A6 (Canada); Centre de recherche du CHUQ, Hopital St Francois d'Assise, 10, rue de l'Espinay, local E0-165, Quebec G1L 3L5 (Canada); Vallade, J. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES, CNRS, Technosud, Rambla de la Thermodynamique, F-66100 Perpignan (France); Agence de l'environnement et de la Ma Latin-Small-Letter-Dotless-I -carettrise de l'Energie, 20, avenue du Gresille, BP 90406, F-49004 Angers Cedex 01 (France); Bazinette, R.; Hernandez, E.; Hernandez, G.; Massines, F. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES, CNRS, Technosud, Rambla de la Thermodynamique, F-66100 Perpignan (France); Nijnatten, P. van [OMT Solutions bv, High Tech Campus 9, 5656AE Eindhoven (Netherlands)

2012-10-15

304

Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution.  

PubMed

This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm × 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45° beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma. PMID:23126767

Laroche, G; Vallade, J; Bazinette, R; van Nijnatten, P; Hernandez, E; Hernandez, G; Massines, F

2012-10-01

305

On the Shortest Path Game  

E-print Network

Sep 19, 2014 ... Institute of Public Economics, University of Graz, ... s, t ? V . The aim of Shortest Path Game is to find a directed path from s to t in the following .... Assigning arbitrary but fixed numbers to each vertex in the beginning,. e.g. 1,...

2014-09-19

306

Obstacle avoidance and path planning  

Microsoft Academic Search

Outlines the state-of-the-art in obstacle avoidance and path planning for industrial robots that is practical on the current generation of computer hardware. Describes practical vehicle planners and planning for manipulators. Summarizes that obstacle avoidance and path planning are techniques with differing goals. Sonar is the standard method of obstacle avoidance systems which is largely limited by the reliability of the

Stephen Cameron

1994-01-01

307

Centrifugal Length Separation of Carbon Nanotubes  

SciTech Connect

Separation of single-wall carbon nanotubes (SWCNTs) by length via centrifugation in a high density medium, and the characterization of both the separated fractions and the centrifugation process are presented. Significant quantities of the separated SWCNTs ranging in average length from < 50 nm to ?2 ?m were produced, with the distribution width being coupled to the rate of the separation. Less rapid separation is shown to produce narrower distributions; these length fractions, produced using sodium deoxycholate dispersed SWCNTs, were characterized by UV-visible-nearinfrared absorption and fluorescence spectroscopy, dynamic light scattering, Raman scattering, and atomic force microscopy. Several parameters of the separation were additionally explored: SWCNT concentration, added salt concentration, liquid density, rotor speed, surfactant concentration, and the processing temperature. The centrifugation technique is shown to support 10 mg per day scale processing and is applicable to all of the major SWCNT production methods. The cost per unit of the centrifugation-based separation is also demonstrated to be significantly less than size exclusion chromatography-based separations.

Fagan, Jeffrey A.; Becker, Matthew L.; Chun, Jaehun; Nie, Pingting; Bauer, Barry J.; Simpson, Jeffrey R.; Hight-Walker, Angela; Hobbie, Erik K.

2008-12-16

308

HII Absorption Bill Erickson  

E-print Network

HII Absorption Bill Erickson November 10, 2006 It would make all of the drift curve simulations.8 dB above the data. One reason for this might be HII absorption which is not modeled in simulations. There are a number of ways that one might try to estimate the absorption. One might use optical maps of HII

Ellingson, Steven W.

309

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

NASA Astrophysics Data System (ADS)

In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences associated with development status and, to a lesser extent, water scarcity. People in the two less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in the more developed sites. Thematically, people in the two less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community-based solutions, while people in the more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in the two water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in the water-rich sites. Thematically, people in the two water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in the water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.

Wutich, A.; White, A. C.; White, D. D.; Larson, K. L.; Brewis, A.; Roberts, C.

2014-01-01

310

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

NASA Astrophysics Data System (ADS)

In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences based on development status and, to a lesser extent, water scarcity. People in less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in more developed sites. Thematically, people in less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community based solutions, while people in more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in water-rich sites. Thematically, people in water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.

Wutich, A.; White, A. C.; Roberts, C. M.; White, D. D.; Larson, K. L.; Brewis, A.

2013-06-01

311

A Two Micron Coherent Differential Absorption Lidar Development  

NASA Technical Reports Server (NTRS)

A pulsed, 2-micron coherent Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO2 profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop. Keywords: Differential Absorption Lidar, Near Infrared Laser,

Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo C.; Koch, Grady J.; Beyon, Jeffrey Y.; VanValkenburg, Randal L.; Kavaya, Michael J.; Singh, Upendra N.

2010-01-01

312

The pressure exerted by adsorbing directed lattice paths and staircase polygons  

E-print Network

A directed path in the vicinity of a hard wall exerts pressure on the wall because of loss of entropy. The pressure at a particular point may be estimated by estimating the loss of entropy if the point is excluded from the path. In this paper we determine asymptotic expressions for the pressure on the X-axis in models of adsorbing directed paths in the first quadrant. Our models show that the pressure vanishes in the limit of long paths in the desorbed phase, but there is a non-zero pressure in the adsorbed phase. We determine asymptotic approximations of the pressure for finite length Dyck paths and directed paths, as well as for a model of adsorbing staircase polygons with both ends grafted to the X-axis.

E. J. Janse van Rensburg; T. Prellberg

2013-02-07

313

An investigation of a mathematical model for atmospheric absorption spectra  

NASA Technical Reports Server (NTRS)

A computer program that calculates absorption spectra for slant paths through the atmosphere is described. The program uses an efficient convolution technique (Romberg integration) to simulate instrument resolution effects. A brief information analysis is performed on a set of calculated spectra to illustrate how such techniques may be used to explore the quality of the information in a spectrum.

Niple, E. R.

1979-01-01

314

Reconfigurable data path processor  

NASA Technical Reports Server (NTRS)

A reconfigurable data path processor comprises a plurality of independent processing elements. Each of the processing elements advantageously comprising an identical architecture. Each processing element comprises a plurality of data processing means for generating a potential output. Each processor is also capable of through-putting an input as a potential output with little or no processing. Each processing element comprises a conditional multiplexer having a first conditional multiplexer input, a second conditional multiplexer input and a conditional multiplexer output. A first potential output value is transmitted to the first conditional multiplexer input, and a second potential output value is transmitted to the second conditional multiplexer output. The conditional multiplexer couples either the first conditional multiplexer input or the second conditional multiplexer input to the conditional multiplexer output, according to an output control command. The output control command is generated by processing a set of arithmetic status-bits through a logical mask. The conditional multiplexer output is coupled to a first processing element output. A first set of arithmetic bits are generated according to the processing of the first processable value. A second set of arithmetic bits may be generated from a second processing operation. The selection of the arithmetic status-bits is performed by an arithmetic-status bit multiplexer selects the desired set of arithmetic status bits from among the first and second set of arithmetic status bits. The conditional multiplexer evaluates the select arithmetic status bits according to logical mask defining an algorithm for evaluating the arithmetic status bits.

Donohoe, Gregory (Inventor)

2005-01-01

315

British Pathe Newsreels Online  

NSDL National Science Digital Library

British Pathe, one of the oldest media companies in the world, recently made available its entire 3500-hour film archive, covering "news, sport, social history and entertainment from 1896 to 1970." At the Web site, users can search by keyword or try out advanced search, if details such as reel numbers or exact titles are known. Casual users may prefer the "Lucky Dip" search, which provides a random selection of films to see. After a search returns a hit list of films, choices include "Preview Film: a page of stills, with a textual description of the clip;" "Download Now: a free, low resolution clip;" or "Add to basket, to purchase higher resolutions of the film." (A rate card giving prices for low and high resolution clips is provided.) One hint for first-time users, though: if files do not seem to download properly, check your email, because you will be sent the URL to retrieve your film. After just a bit of finagling on our first visit, we watched the Beatles at a water-skiing show, Charlie Chaplin, and Sir Ernest Shackleton and his sled dogs photographed in 1916 on returning from their Antarctic expedition.

2002-01-01

316

Measurements on CO Concentration and gas temperature at 1.58 um with Tunable Diode Laser Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

The technique based on tunable diode laser absorption Spectroscopy (TDLAS) has been developed to realize the real-time and dynamic measurement of the combustion-generated pollutants. In this paper the fundamental of concentration and temperature measurement with TDLAS is presented. To validate the method, an experimental system of TDLAS is set up. A simple VCSEL diode without temperature controller is used for direct absorption and WMS setup. Restricted by modulation voltage and noise from diode laser and detector, concentration of 0.2% for 1 m path length can be detected. Temperature measurement in tube furnace is also carried out by CO2 absorption lines near 1.58um, and below 800K the difference between calculation by TDLAS and temperature signal by K-thermocouple is less than 60K. The method to eliminate the effects of the particles is also discussed here. By using three-order polynomial program, the measurement can be not affected by particles and power fluctuation.

Wang, Fei; Li, Ning; Huang, Qunxing; Yan, Jianhua; Cen, Kefa

2007-06-01

317

Nitrate Absorption by Barley  

PubMed Central

The influence of protein synthesis and nitrate reductase activity on nitrate absorption by barley (Hordeum vulgare L.) was investigated. Cycloheximide decreased nitrate absorption. Pretreatment studies showed that cycloheximide affects either energy transfer or nitrate reductase activity or both. Illumination increased plant capacity for nitrate absorption, possibly through increased energy supply and/or increased nitrate reductase activity. There was a positive correlation between nitrate reductase activity and light. Inhibiting the development of nitrate reductase activity by tungstate decreased nitrate absorption. At least two nitrate transport systems are thus proposed in barley: one operating in the dark, with little nitrate reductase activity detectable; and one closely correlated with nitrate reductase activity. Total absorption is the sum of dark absorption and absorption facilitated by nitrate reductase. PMID:16659426

Rao, K. Prasad; Rains, D. William

1976-01-01

318

Recent Results From, and Future Plans for the JPL Carbon Dioxide Laser Absorption Spectrometer  

Microsoft Academic Search

The Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) is an aircraft based Integrated Path Differential Absorption (IPDA) Spectrometer operating in the 2 micron wavelength range that we have been developing at JPL to evaluate the measurement of the column integrated carbon dioxide concentration beneath the aircraft. The IPDA measurement technique is based on an approach first used for the measurement of

G. D. Spiers; R. Menzies; S. Geier; M. Phillips

2009-01-01

319

Open-path atmospheric transmission for a diode-pumped cesium laser.  

PubMed

A tunable diode laser absorption spectroscopy device was developed to study atmospheric propagation for emerging high-energy laser weapons. The cesium diode-pumped alkali laser operates near 895 nm in the vicinity of several water-vapor absorption lines. Temperature, pressure, and water vapor concentration were determined for 150 m and 1 km open paths with statistical errors of ?0.2%. Comparison with meteorological instruments yields agreement for the 1 km path to within 0.6% for temperature, 3.7% for pressure, and 2.4% for concentration. PMID:23207380

Rice, Christopher A; Lott, Gordon E; Perram, Glen P

2012-12-01

320

Computing Path Tables for Quickest Multipaths In Computer Networks  

SciTech Connect

We consider the transmission of a message from a source node to a terminal node in a network with n nodes and m links where the message is divided into parts and each part is transmitted over a different path in a set of paths from the source node to the terminal node. Here each link is characterized by a bandwidth and delay. The set of paths together with their transmission rates used for the message is referred to as a multipath. We present two algorithms that produce a minimum-end-to-end message delay multipath path table that, for every message length, specifies a multipath that will achieve the minimum end-to-end delay. The algorithms also generate a function that maps the minimum end-to-end message delay to the message length. The time complexities of the algorithms are O(n{sup 2}((n{sup 2}/logn) + m)min(D{sub max}, C{sub max})) and O(nm(C{sub max} + nmin(D{sub max}, C{sub max}))) when the link delays and bandwidths are non-negative integers. Here D{sub max} and C{sub max} are respectively the maximum link delay and maximum link bandwidth and C{sub max} and D{sub max} are greater than zero.

Grimmell, W.C.

2004-12-21

321

Longest fault-free paths in hypercubes with vertex faults  

Microsoft Academic Search

The hypercube is one of the most versatile and efficient interconnection networks (networks for short) so far discovered for parallel computation. Let f denote the number of faulty vertices in an n-cube. This study demonstrates that when f?n?2, the n-cube contains a fault-free path with length at least 2n?2f?1 (or 2n?2f?2) between two arbitrary vertices of odd (or even) distance.

Jung-sheng Fu

2006-01-01

322

A Hierarchical Path View Model for Path Finding in Intelligent Transportation Systems  

Microsoft Academic Search

Effective path finding has been identified as an important requirement for dynamic route guidance in Intelligent Transportation Systems (ITS). Path finding is most efficient if the all-pair (shortest) paths are precomputed because path search requires only simple lookups of the precomputed path views. Such an approach however incurs path view maintenance (computation and update) and storage costs which can be

Yun-Wu Huang; Ning Jing; ELKE A. RUNDENSTEINER

1997-01-01

323

IMPEDANCE OF FINITE LENGTH RESISTOR  

SciTech Connect

We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

2005-05-15

324

Scattering theory with path integrals  

NASA Astrophysics Data System (ADS)

Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

Rosenfelder, R.

2014-03-01

325

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS  

E-print Network

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS AND RESEARCH CHALLENGES School of Computing Undergraduate Student) #12;Computer Science Misconceptions Intro to Computer Science - Florida International University 2 Some preconceived ideas & stereotypes about Computer Science (CS) are quite common

Hristidis, Vagelis

326

What is a MISR path?  

Atmospheric Science Data Center

... orbits that observe the same areas under the same nominal angular conditions. Areas that are close to each other in longitude will be ... 1 crosses the equator at 64.60° west longitude. Orbital Paths/Blocks   ...

2014-12-08

327

Collaborative Authoring of Walden's Paths  

E-print Network

The World Wide Web contains rich collections of digital materials that can be used in education and learning settings. The collaborative authoring prototype of Walden's Paths targets two groups of users: educators and learners. From the perspective...

Li, Yuanling

2012-10-19

328

Morse theory in path space  

E-print Network

We consider the path space of a curved manifold on which a point particle is introduced in a conservative physical system with constant total energy to formulate its action functional and geodesic equation together with breaks on the path. The second variation of the action functional is exploited to yield the geodesic deviation equation and to discuss the Jacobi fields on the curved manifold. We investigate the topology of the path space using the action functional on it and its physical meaning by defining the gradient of the action functional, the space of bounded flow energy solutions and the moduli space associated with the critical points of the action functional. We also consider the particle motion on the $n$-sphere $S^{n}$ in the conservative physical system to discuss explicitly the moduli space of the path space and the corresponding homology groups.

Yong Seung Cho; Soon-Tae Hong

2007-06-01

329

Scattering theory with path integrals  

SciTech Connect

Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

Rosenfelder, R. [Particle Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)] [Particle Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

2014-03-15

330

Survivable paths in multilayer networks  

E-print Network

We consider the problem of protection in multilayer networks. In single-layer net- works, a pair of disjoint paths can be used to provide protection for a source-destination pair. However, this approach cannot be directly ...

Parandehgheibi, Marzieh

2012-01-01

331

Formal language constrained path problems  

SciTech Connect

In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

Barrett, C.; Jacob, R.; Marathe, M.

1997-07-08

332

The Length of My Feet  

NSDL National Science Digital Library

This is Lesson 1 of a five lesson unit. "This lesson focuses students' attention on the attributes of length and develops their knowledge of and skill in using nonstandard units of measurement, their feet. It provides practice with and remediation of the measurable attributes of length." (from NCTM Illuminations)

Illuminations National Council of Teachers of Math

2009-01-28

333

Calcium absorption and achlorhydria  

Microsoft Academic Search

Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium

Robert R. Recker

1985-01-01

334

DOAS (differential optical absorption spectroscopy) urban pollution measurements  

NASA Astrophysics Data System (ADS)

During July and August of 1990, a differential optical absorption spectrometer (DOAS) made by OPSIS Inc. was used to measure gaseous air pollutants over three separate open paths in Atlanta, GA. Over path 1 (1099 m) and path 2 (1824 m), ozone (03), sulfur dioxide (SO2) nitrogen dioxide (NO2), nitrous acid (HNO2) formaldehyde (HCHO), benzene, toluene, and o-xylene were measured. Nitric oxide (NO) and ammonia (NH3) were monitored over path 3 (143 m). The data quality and data capture depended on the compound being measured and the path over which it was measured. Data quality criteria for each compound were chosen such that the average relative standard deviation would be less than 25%. Data capture ranged from 43% for o-xylene for path 1 to 95% for ozone for path 2. Benzene, toluene, and o-xylene concentrations measured over path 2, which crossed over an interstate highway, were higher than concentrations measured over path 1, implicating emissions from vehicles on the highway as a significant source of these compounds. Federal Reference Method (FRN) instruments were located near the DOAS light receivers and measurements of 03, NO2, and NO were made concurrently with the DOAS. Correlation coefficients greater than 0.85 were obtained between the DOAS and FRM's; however, there was a difference between the mean values obtained by the two methods for 03 and NO. A gas chromatograph for measuring volatile organic compounds was operated next to the FRN's. Correlation coefficients of about 0.66 were obtained between the DOAS and GC measurements of benzene and o- xylene. However, the correlation coefficient between the DOAS and GC measurements of toluene averaged only 0.15 for the two DOAS measurement paths. The lack of correlation and other factors indicate the possibility of a localized source of toluene near the GC. In general, disagreements between the two measurement methods could be caused by atmospheric inhomogeneities or interferences in the DOAS and other methods.

Stevens, Robert K.; Vossler, T. L.

1991-05-01

335

The Absorption Spectrum of Chlorine Dioxide  

Microsoft Academic Search

The wave-lengths of 134 absorption bands of ClO2 have been measured with the Hilger E-1 and E-185 quartz instruments. The bands have been arranged in progressions and the energy levels deduced. Five vibrational levels of the normal electronic state have been found; the vibrational levels of the excited electronic state can be described with the use of two vibrational quantum

Harold C. Urey; Helen Johnston

1931-01-01

336

Calculating Least Risk Paths in 3d Indoor Space  

NASA Astrophysics Data System (ADS)

Over the last couple of years, research on indoor environments has gained a fresh impetus; more specifically applications that support navigation and wayfinding have become one of the booming industries. Indoor navigation research currently covers the technological aspect of indoor positioning and the modelling of indoor space. The algorithmic development to support navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. However, alternative algorithms for outdoor navigation have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behaviour (e.g. simplest paths, least risk paths). These algorithms are currently restricted to outdoor applications. The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas…). As such, the clarity and easiness of route instructions is of paramount importance when distributing indoor routes. A shortest or fastest path indoors not necessarily aligns with the cognitive mapping of the building. Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-storey building. The results of several least risk path calculations are compared to the shortest paths in indoor environments in terms of total length, improvement in route description complexity and number of turns. Several scenarios are tested in this comparison: paths covering a single floor, paths crossing several building wings and/or floors. Adjustments to the algorithm are proposed to be more aligned to the specific structure of indoor environments (e.g. no turn restrictions, restricted usage of rooms, vertical movement) and common wayfinding strategies indoors. In a later stage, other cognitive algorithms will be implemented and tested in both an indoor and combined indoor-outdoor setting, in an effort to improve the overall user experience during navigation in indoor environments.

Vanclooster, A.; De Maeyer, Ph.; Fack, V.; Van de Weghe, N.

2013-08-01

337

Advanced Sine Wave Modulation of Continuous Wave Laser System for Atmospheric CO2 Differential Absorption Measurements  

NASA Technical Reports Server (NTRS)

NASA Langley Research Center in collaboration with ITT Exelis have been experimenting with Continuous Wave (CW) laser absorption spectrometer (LAS) as a means of performing atmospheric CO2 column measurements from space to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission.Because range resolving Intensity Modulated (IM) CW lidar techniques presented here rely on matched filter correlations, autocorrelation properties without side lobes or other artifacts are highly desirable since the autocorrelation function is critical for the measurements of lidar return powers, laser path lengths, and CO2 column amounts. In this paper modulation techniques are investigated that improve autocorrelation properties. The modulation techniques investigated in this paper include sine waves modulated by maximum length (ML) sequences in various hardware configurations. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit perfect autocorrelation properties down to one cycle per code bit. In addition, a method is presented to bandwidth limit the ML sequence based on a Gaussian filter implemented in terms of Jacobi theta functions that does not seriously degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.

2014-01-01

338

Absorption Cross-Sections in the Vacuum Ultra-Violet. III. Methane  

Microsoft Academic Search

Cross-sections for the continuous absorption of radiation by methane in the wave-length range 1600 to 350 angstrom have been measured. The absorption is analyzed so as to distinguish between absorption leading to photo-dissociation processes and absorption due to photo-ionization. The main photo-ionization process is CH4+hv--> CH4++e-, and the photo-ionization cross-section is measured for free electron energies from 0 to about

R. W. Ditchburn

1955-01-01

339

Walking on inclines: how do desert ants monitor slope and step length  

PubMed Central

Background During long-distance foraging in almost featureless habitats desert ants of the genus Cataglyphis employ path-integrating mechanisms (vector navigation). This navigational strategy requires an egocentric monitoring of the foraging path by incrementally integrating direction, distance, and inclination of the path. Monitoring the latter two parameters involves idiothetic cues and hence is tightly coupled to the ant's locomotor behavior. Results In a kinematic study of desert ant locomotion performed on differently inclined surfaces we aimed at pinpointing the relevant mechanisms of estimating step length and inclination. In a behavioral experiment with ants foraging on slippery surfaces we broke the otherwise tightly coupled relationship between stepping frequency and step length and examined the animals' ability to monitor distances covered even under those adverse conditions. We show that the ants' locomotor system is not influenced by inclined paths. After removing the effect of speed, slope had only marginal influence on kinematic parameters. Conclusion From the obtained data we infer that the previously proposed monitoring of angles of the thorax-coxa joint is not involved in inclinometry. Due to the tiny variations in cycle period, we also argue that an efference copy of the central pattern generator coding the step length in its output frequency will most likely not suffice for estimating step length and complementing the pedometer. Finally we propose that sensing forces acting on the ant's legs could provide the desired neuronal correlate employed in monitoring inclination and step length. PMID:18518946

Seidl, Tobias; Wehner, Rüdiger

2008-01-01

340

Correlations between bond lengths, Tc, and O vibration frequencies: Raman-scattering and infrared-absorption study of the 1:2:1:2 structure (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 as a function of doping  

Microsoft Academic Search

Raman-scattering and infrared-absorption measurements on optical phonons are used to investigate the doping-induced changes in the electronic structure of (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 (Tl\\/Pb-1:2:1:2). In contrast to YBa2Cu3O7-delta (YBCO), the doping of the CuO2 planes is achieved by direct substitution of Ca2+ for Y3+ in between the CuO2 planes, enabling the effects of the dynamic out-of-plane charge transfer and doping to be separated.

T. Mertelj; D. Mihailovic; F. C. Matacotta; R. S. Liu; J. R. Cooper; I. Gameson; P. P. Edwards

1993-01-01

341

On hallucinated garden paths UC San Diego  

E-print Network

On hallucinated garden paths Roger Levy UC San Diego Department of Linguistics 2010 LSA Annual., 1995) #12;Garden-pathing in incremental parsing · Garden-path sentence a consequence of incrementality recent examples don't match this definition · Tabor et al. (2004): garden-paths on continuous substrings

342

Solar absorption surface panel  

DOEpatents

A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

Santala, Teuvo J. (Attleboro, MA)

1978-01-01

343

Length-dependent optical properties of single-walled carbon nanotube samples  

NASA Astrophysics Data System (ADS)

Contradictory findings have been reported on the length dependence of optical absorption cross sections and fluorescence quantum yields in single-walled carbon nanotubes (SWCNTs). To clarify these points, studies have been made on bulk SWCNT dispersions subjected to length fractionation by electrophoretic separation or by ultrasonication-induced scission. Fractions ranged from ca. 120 to 760 nm in mean length. Samples prepared by shear-assisted dispersion were subsequently shortened by ultrasonic processing. After accounting for processing-induced changes in the surfactant absorption background, SWCNT absorption was found constant within ±11% as average nanotube length changed by a factor of 3.8. This indicates that the absorption cross-section per carbon atom is not length dependent. By contrast, in length fractions prepared by both methods, the bulk fluorescence efficiency or average quantum yield increased with SWCNT average length and approached an apparent asymptotic limit near 1 ?m. This result is interpreted as reflecting the combined contributions of exciton quenching by sidewall defects and by the ends of shorter nanotubes.

Naumov, Anton V.; Tsyboulski, Dmitri A.; Bachilo, Sergei M.; Weisman, R. Bruce

2013-08-01

344

An in situ cell for characterization of solids by soft x-ray absorption  

NASA Astrophysics Data System (ADS)

A cell has been designed and fabricated for in situ characterization of catalysts and environmental materials using soft x-ray absorption spectroscopy and spectromicroscopy at photon energies above 250 eV. "Lab-on-a-chip" technologies were used to fabricate the cell on a glass wafer. The sample compartment is 1.0 mm in diameter and has a gas path length of 0.8 mm to minimize x-ray absorption in the gas phase. The sample compartment can be heated to 533 K by an Al resistive heater and gas flows up to 5.0 cm3 min-1 can be supplied to the sample compartment through microchannels. The performance of the cell was tested by acquiring Cu L3-edge x-ray appearance near-edge structure (XANES) data during the reduction and oxidation of a silica-supported Cu catalyst using the beam line 11.0.2 scanning transmission x-ray microscope (STXM) at the Advanced Light Source of Lawrence Berkeley National Laboratory (Berkeley, CA). Two-dimensional images of individual catalyst particles were recorded at photon energies between 926 and 937 eV, the energy range in which the Cu(II) and Cu(I) L3 absorption edges are observed. Oxidation state specific images of the catalyst clearly show the disappearance of Cu(II) species during the exposure of the oxidized sample to 4% CO in He while increasing the temperature from 308 to 473 K. Reoxidation restores the intensity of the image associated with Cu(II). Cu L3-edge XANES spectra obtained from stacks of STXM images show that with increasing temperature the Cu(II) peak intensity decreases as the Cu(I) peak intensity increases.

Drake, Ian J.; Liu, Teris C. N.; Gilles, Mary; Tyliszczak, Tolek; Kilcoyne, A. L. David; Shuh, David K.; Mathies, Richard A.; Bell, Alexis T.

2004-10-01

345

Cosmic absorption of ultra high energy particles  

E-print Network

This paper summarizes the limits on propagation of ultra high energy particles in the Universe, set up by their interactions with cosmic background of photons and neutrinos. By taking into account cosmic evolution of these backgrounds and considering appropriate interactions we derive the mean free path for ultra high energy photons, protons and neutrinos. For photons the relevant processes are the Breit-Wheeler process as well as the double pair production process. For protons the relevant reactions are the photopion production and the Bethe-Heitler process. We discuss the interplay between the energy loss length and mean free path for the Bethe-Heitler process. Neutrino opacity is determined by its scattering off the cosmic background neutrino. We compute for the first time the high energy neutrino horizon as a function of its energy.

Ruffini, R; Xue, S -S

2015-01-01

346

Petawatt laser absorption bounded  

PubMed Central

The interaction of petawatt (1015?W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

2014-01-01

347

Effect of deformation path sequence on the behavior of nanoscale copper bicrystal interfaces.  

SciTech Connect

Molecular dynamics calculations are performed to study the effect of deformation sequence and history on the inelastic behavior of copper interfaces on the nanoscale. An asymmetric 45 deg tilt bicrystal interface is examined, representing an idealized high-angle grain boundary interface. The interface model is subjected to three different deformation paths: tension then shear, shear then tension, and combined proportional tension and shear. Analysis shows that path-history dependent material behavior is confined within a finite layer of deformation around the bicrystal interface. The relationships between length scale and interface properties, such as the thickness of the path-history dependent layer and the interface strength, are discussed in detail.

Spearot, Douglas E. (Georgia Institute of Technology, Atlanta, GA); Jacob, Karl I. (Georgia Institute of Technology, Atlanta, GA); Plimpton, Steven James; McDowell, David Lynn (Georgia Institute of Technology, Atlanta, GA)

2005-06-01

348

Optimal Patent Length and Breadth  

Microsoft Academic Search

In providing rewards to innovators, there is a tradeoff between patent length and breadth. This article provides conditions under which the optimal patent policy involves infinitely-lived patents, with patent breadth adjusting to provide the required reward for innovation.

Richard Gilbert; Carl Shapiro

1990-01-01

349

Bimanual and unimanual length perception.  

PubMed

From previous studies, it is unclear how bimanual length discrimination differs from unimanual length discrimination. To investigate the difference, we designed an experiment with four conditions. In the first two conditions, unimanual and bimanual discrimination thresholds are determined. In the third and fourth conditions, length is explored with the two index fingers like in the bimanual condition, but the reference is either internal, by clasping the hands together, or external, by grasping handles connected to the table. We find that thresholds for the unimanual condition (7.0%) and the clasping condition (9.2%) are both lower than for the bimanual condition (16%) and the grasping handles condition (15%). We conclude that when discriminating length unimanually and bimanually while clasping the hands together, the internal reference within the hand can be used and that explains the lower discrimination thresholds. PMID:24792507

Panday, Virjanand; Bergmann Tiest, Wouter M; Kappers, Astrid M L

2014-09-01

350

LASER-BASED, LONG PATH MONITORING OF AMBIENT GASES, ANALYSIS OF TWO SYSTEMS  

EPA Science Inventory

New long path absorption techniques for measurement of ambient O3 and CO have recently been demonstrated using a CO2 laser and a semiconductor diode laser, respectively. For the CO2 laser system the use of closely spaced wavelengths minimizes system drift and simplifies the deter...

351

Spectral properties of microwave graphs with local absorption  

E-print Network

The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50 Ohm load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.

M. Allgaier; S. Gehler; S. Barkhofen; H. -J. Stöckmann; U. Kuhl

2014-03-30

352

Gas-path seal technology  

NASA Technical Reports Server (NTRS)

Improved gas-path seals are needed for better fuel economy, longer performance retention, and lower maintenance, particularly in advanced, high-performance gas turbine engines. Problems encountered in gas-path sealing are described, as well as new blade-tip sealing approaches for high-pressure compressors and turbines. These include a lubricant coating for conventional, porous-metal, rub-strip materials used in compressors. An improved hot-press metal alloy shows promise to increase the operating surface temperatures of high-pressure-turbine, blade-tip seals to 1450 K (2150 F). Three ceramic seal materials are also described that have the potential to allow much higher gas-path surface operating temperatures than are possible with metal systems.

Zuk, J.

1976-01-01

353

Multiple paths in complex tasks  

NASA Technical Reports Server (NTRS)

The relationship between utility judgments of subtask paths and the utility of the task as a whole was examined. The convergent validation procedure is based on the assumption that measurements of the same quantity done with different methods should covary. The utility measures of the subtasks were obtained during the performance of an aircraft flight controller navigation task. Analyses helped decide among various models of subtask utility combination, whether the utility ratings of subtask paths predict the whole tasks utility rating, and indirectly, whether judgmental models need to include the equivalent of cognitive noise.

Galanter, Eugene; Wiegand, Thomas; Mark, Gloria

1987-01-01

354

Gamma-Normal Probability Distribution Arc Length  

E-print Network

used to attack randomness, and many researchers have done lots of work on stochastic ..... showed the performance of the proposed methodology for the shortest path. ... Dreyfus, S. (1969) An appraisal of some shortest path algorithms.

Hesam

2014-11-04

355

DYCK PATHS WITH PARITY RESTRICTIONS FOR THE FINAL RUNS TO THE ORIGIN: A STUDY OF THE HEIGHT  

E-print Network

PRODINGER Abstract. Stanley and Callan considered Dyck paths where the lengths of the run to the origin-length n) is the Catalan number 1 n+1 2n n . Two standard texts that describe this are [9, 5]. Callan [1 number of down steps. The second one is due to Callan himself: For the last sojourn, the (maximal) run

Prodinger, Helmut

356

Fluid absorption solar energy receiver  

NASA Technical Reports Server (NTRS)

A conventional solar dynamic system transmits solar energy to the flowing fluid of a thermodynamic cycle through structures which contain the gas and thermal energy storage material. Such a heat transfer mechanism dictates that the structure operate at a higher temperature than the fluid. This investigation reports on a fluid absorption receiver where only a part of the solar energy is transmitted to the structure. The other part is absorbed directly by the fluid. By proportioning these two heat transfer paths the energy to the structure can preheat the fluid, while the energy absorbed directly by the fluid raises the fluid to its final working temperature. The surface temperatures need not exceed the output temperature of the fluid. This makes the output temperature of the gas the maximum temperature in the system. The gas can have local maximum temperatures higher than the output working temperature. However local high temperatures are quickly equilibrated, and since the gas does not emit radiation, local high temperatures do not result in a radiative heat loss. Thermal radiation, thermal conductivity, and heat exchange with the gas all help equilibrate the surface temperature.

Bair, Edward J.

1993-01-01

357

Long gain length solar pumped box laser  

NASA Technical Reports Server (NTRS)

A solar pumped laser has its lasing path lengthened by forming a square loop in the lasing path by means of bending mirrors. Solar radiation is collected and concentrated into a donut shaped intensity pattern. This intensity pattern is directed onto the lasing path such that there is a maximum fit of the solar intensity pattern to the square loop laser cavity.

Deyoung, R. J.

1986-01-01

358

Improved integrating cavity absorption meter  

E-print Network

Improvements have been made in the Integrating Cavity Absorption Meter (ICAM). The ICAM is used to measure very small optical absorption coefficients (0.001m?¹), virtually independent of scattering effects. Optical absorption is measured...

Cui, Liqiu

2000-01-01

359

Folded-Light-Path Colloidal Quantum Dot Solar Cells  

PubMed Central

Colloidal quantum dot photovoltaics combine low-cost solution processing with quantum size-effect tuning to match absorption to the solar spectrum. Rapid advances have led to certified solar power conversion efficiencies of over 7%. Nevertheless, these devices remain held back by a compromise in the choice of quantum dot film thickness, balancing on the one hand the need to maximize photon absorption, mandating a thicker film, and, on the other, the need for efficient carrier extraction, a consideration that limits film thickness. Here we report an architecture that breaks this compromise by folding the path of light propagating in the colloidal quantum dot solid. Using this method, we achieve a substantial increase in short-circuit current, ultimately leading to improved power conversion efficiency. PMID:23835564

Koleilat, Ghada I.; Kramer, Illan J.; Wong, Chris T. O.; Thon, Susanna M.; Labelle, André J.; Hoogland, Sjoerd; Sargent, Edward H.

2013-01-01

360

Superconducting optical conductivity for arbitrary temperature and mean free path  

NASA Astrophysics Data System (ADS)

Calculations of the optical conductivity of a superconductor valid for any temperature T and any mean free path l are presented. They are based on the method of Marsiglio, Schossmann, and Carbotte of computing the real-frequency-axis gap and renormalization function. The work is applied to a study of the signature of the opening of the gap edge ?(T) as the superconducting state develops. At finite temperature, the presence of a normal-fluid component leads to absorption down to zero frequency (?). For sufficiently impure systems there remains, nevertheless, a sharp threshold for additional absorption from the condensate which starts at ?=2?(T), so that it is possible to deduce from it an accurate value of ?(T). For the pure limit, the situation is more ambiguous.

Akis, R.; Carbotte, J. P.; Timusk, T.

1991-06-01

361

PATH DECOMPOSITION METHOD FOR POTENTIALS  

Microsoft Academic Search

We know all that thanks the development of the various formulations, moreover all equiva- lent, the physical phenomena explained by quantum mechanics are understood better. Among these formulations, we can quote most known because of its success: the formulation of Feyn- man (1) which uses the tool of the path integral. Not a long time ago, obtaining solutions for certain

A. Laissaoui; L. Chetouani

362

The Path of Human Evolution  

Microsoft Academic Search

A complex series of evolutionary steps, contingent upon a dynamic environmental context and a long biological heritage, have led to the ascent of Homo sapiens as a dominant component of the modern biosphere. In a field where missing links still abound and new discoveries regularly overturn theoretical paradigms, our understanding of the path of human evolution has made tremendous advances

C. S. Feibel

2004-01-01

363

SSME propellant path leak detection  

NASA Technical Reports Server (NTRS)

The complicated high-pressure cycle of the space shuttle main engine (SSME) propellant path provides many opportunities for external propellant path leaks while the engine is running. This mode of engine failure may be detected and analyzed with sufficient speed to save critical engine test hardware from destruction. The leaks indicate hardware failures which will damage or destroy an engine if undetected; therefore, detection of both cryogenic and hot gas leaks is the objective of this investigation. The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-the-art technology infrared (IR) thermal imaging systems combined with computer, digital image processing, and expert systems for the engine protection. The feasibility of IR leak plume detection is evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application.

Crawford, Roger; Shohadaee, Ahmad Ali

1989-01-01

364

Career Paths in Environmental Sciences  

EPA Science Inventory

Career paths, current and future, in the environmental sciences will be discussed, based on experiences and observations during the author's 40 + years in the field. An emphasis will be placed on the need for integrated, transdisciplinary systems thinking approaches toward achie...

365

Equivariant Localization of Path Integrals  

E-print Network

We review equivariant localization techniques for the evaluation of Feynman path integrals. We develop systematic geometric methods for studying the semi-classical properties of phase space path integrals for dynamical systems, emphasizing the relations with integrable and topological quantum field theories. Beginning with a detailed review of the relevant mathematical background -- equivariant cohomology and the Duistermaat-Heckman theorem, we demonstrate how the localization ideas are related to classical integrability and how they can be formally extended to derive explicit localization formulas for path integrals in special instances using BRST quantization techniques. Various loop space localizations are presented and related to notions in quantum integrability and topological field theory. We emphasize the common symmetries that such localizable models always possess and use these symmetries to discuss the range of applicability of the localization formulas. A number of physical and mathematical applications are presented in connection with elementary quantum mechanics, Morse theory, index theorems, character formulas for semi-simple Lie groups, quantization of spin systems, unitary integrations in matrix models, modular invariants of Riemann surfaces, supersymmetric quantum field theories, two-dimensional Yang-Mills theory, conformal field theory, cohomological field theories and the loop expansion in quantum field theory. Some modern techniques of path integral quantization, such as coherent state methods, are also discussed. The relations between equivariant localization and other ideas in topological field theory, such as the Batalin-Fradkin-Vilkovisky and Mathai-Quillen formalisms, are presented.

Richard J. Szabo

1996-08-12

366

Employer Resource Manual. Project Path.  

ERIC Educational Resources Information Center

Project Path at Illinois' College of DuPage was established to provide pre-employment training and career counseling for disabled students. To encourage the integration of qualified individuals with disabilities into the workplace, the project compiled this resource manual for area businesses, providing tips for interacting with disabled people…

Kane, Karen R.; Del George, Eve

367

Perceived Shrinkage of Motion Paths  

ERIC Educational Resources Information Center

We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require…

Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

2009-01-01

368

Low bias integrated path estimators  

Microsoft Academic Search

We consider the problem of estimating the time-average variance constant for a stationary process. A previous paper described an approach based on multiple integrations of the simulation output path, and described the efficiency improvement that can result compared with the method of batch means (which is a special case of the method). In this paper we describe versions of the

James M. Calvin

2007-01-01

369

Folded path LWIR system for SWAP constrained platforms  

NASA Astrophysics Data System (ADS)

Folded path reflection and catadioptric optics are of growing interest, especially in the long wave infrared (LWIR), due to continuing demands for reductions in imaging system size, weight and power (SWAP). We present the optical design and laboratory data for a 50 mm focal length low f/# folded-path compact LWIR imaging system. The optical design uses 4 concentric aspheric mirrors, each of which is described by annular aspheric functions well suited to the folded path design space. The 4 mirrors are diamond turned onto two thin air-spaced aluminum plates which can be manually focused onto the uncooled LWIR microbolometer array detector. Stray light analysis will be presented to show how specialized internal baffling can be used to reduce stray light propagation through the folded path optical train. The system achieves near diffraction limited performance across the FOV with a 15 mm long optical train and a 5 mm back focal distance. The completed system is small enough to reside within a 3 inch diameter ball gimbal.

Fleet, Erin F.; Wilson, Michael L.; Linne von Berg, Dale; Giallorenzi, Thomas; Mathieu, Barry

2014-06-01

370

Pairing versus quarteting coherence length  

E-print Network

We systematically analyse the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We evidence the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the $\\alpha$-particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free $\\alpha$-particle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

Doru S. Delion; Virgil V. Baran

2015-01-20

371

Improving misalignment for feedback path estimation in hearing aid by multiple short-time noise injections.  

PubMed

Adaptive Feedback Cancellation (AFC) methods are used to find an FIR filter to cancel the negative effect of acoustic feedback between the loudspeaker and microphone of the hearing aid. Finding the AFC filter of appropriate order/length directly affects the performance and complexity of the system. In this paper, we use noise injection method to find the AFC filter estimating the feedback path model. We show that the optimum length which guarantees a good compromise between the quality and the complexity of the system may be smaller than the length of the actual feedback path model. However, in order to improve the performance of the system in terms of Misalignment criterion, we propose using multiple short-time noise injections and averaging method to find the best filter estimate of appropriate length. PMID:23367108

Khoubrouy, Soudeh A; Panahi, Issa M S

2012-01-01

372

Handbook for the estimation of microwave propagation effects: Link calculations for earth-space paths (path loss and noise estimation)  

NASA Technical Reports Server (NTRS)

A single model for a standard of comparison for other models when dealing with rain attenuation problems in system design and experimentation is proposed. Refinements to the Global Rain Production Model are incorporated. Path loss and noise estimation procedures as the basic input to systems design for earth-to-space microwave links operating at frequencies from 1 to 300 GHz are provided. Topics covered include gaseous absorption, attenuation by rain, ionospheric and tropospheric scintillation, low elevation angle effects, radome attenuation, diversity schemes, link calculation, and receiver noise emission by atmospheric gases, rain, and antenna contributions.

Crane, R. K.; Blood, D. W.

1979-01-01

373

Compounds affecting cholesterol absorption  

NASA Technical Reports Server (NTRS)

A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)

2004-01-01

374

Absorption heat pump system  

DOEpatents

The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

Grossman, Gershon (Oak Ridge, TN)

1984-01-01

375

Solar selective absorption coatings  

DOEpatents

A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

Mahoney, Alan R. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Martinez, F. Edward (Horseheads, NY)

2004-08-31

376

Solar selective absorption coatings  

DOEpatents

A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

Mahoney, Alan R. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Martinez, F. Edward (Horseheads, NY)

2003-10-14

377

IMF Length Scales and Predictability: The Two Length Scale Medium  

NASA Technical Reports Server (NTRS)

We present preliminary results from a systematic study using simultaneous data from three spacecraft, Wind, IMP 8 (Interplanetary Monitoring Platform) and Geotail to examine interplanetary length scales and their implications on predictability for magnetic field parcels in the typical solar wind. Time periods were selected when the plane formed by the three spacecraft included the GSE (Ground Support Equipment) x-direction so that if the parcel fronts were strictly planar, the two adjacent spacecraft pairs would determine the same phase front angles. After correcting for the motion of the Earth relative to the interplanetary medium and deviations in the solar wind flow from radial, we used differences in the measured front angle between the two spacecraft pairs to determine structure radius of curvature. Results indicate that the typical radius of curvature for these IMF parcels is of the order of 100 R (Sub E). This implies that there are two important IMF (Interplanetary Magnetic Field) scale lengths relevant to predictability: (1) the well-established scale length over which correlations observed by two spacecraft decay along a given IMF parcel, of the order of a few tens of Earth radii and (2) the scale length over which two spacecraft are unlikely to even observe the same parcel because of its curvature, of the order of a hundred Earth radii.

Collier, Michael R.; Szabo, Adam; Slavin, James A.; Lepping, R. P.; Kokubun, S.

1999-01-01

378

Seven-effect absorption refrigeration  

DOEpatents

A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

DeVault, Robert C. (Knoxville, TN); Biermann, Wendell J. (Fayetteville, NY)

1989-01-01

379

Seven-effect absorption refrigeration  

DOEpatents

A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.

DeVault, R.C.; Biermann, W.J.

1989-05-09

380

Effect of idler absorption in pulsed optical parametric oscillators.  

PubMed

Absorption at the idler wavelength in an optical parametric oscillator (OPO) is often considered detrimental. We show through simulations that pulsed OPOs with significant idler absorption can perform better than OPOs with low idler absorption both in terms of conversion efficiency and beam quality. The main reason for this is reduced back conversion. We also show how the beam quality depends on the beam width and pump pulse length, and present scaling relations to use the example simulations for other pulsed nanosecond OPOs. PMID:21369103

Rustad, Gunnar; Arisholm, Gunnar; Farsund, Øystein

2011-01-31

381

Effective Cavity Length of Gyrotrons  

NASA Astrophysics Data System (ADS)

Megawatt-class gyrotron oscillators for electron cyclotron heating and non-inductive current drive (ECH&CD) in magnetically confined thermonuclear fusion plasmas have relatively low cavity quality factors in the range of 1000 to 2000. The effective length of their cavities cannot be simply deduced from the cavity electric field profile, since this has by far not a Gaussian shape. The present paper presents a novel method to estimate the effective length of a gyrotron cavity just from the eigenvalue of the operating TEm,n mode, the cavity radius and the exact oscillation frequency which may be numerically computed or precisely measured. This effective cavity length then can be taken to calculate the Fresnel parameter in order to confirm that the cavity is not too short so that the transverse structure of any mode in the cavity is the same as that of the corresponding mode in a long circular waveguide with the same diameter.

Thumm, Manfred

2014-12-01

382

Screening length in plasma winds  

E-print Network

We study the screening length L_s of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v. Using the AdS/CFT correspondence we investigate, analytically, the screening length in the ultra-relativistic limit. We develop a procedure that allows us to find the scaling exponent for a large class of backgrounds. We find that for conformal theories the screening length is (boosted energy density)^{-1/d}. As examples of conformal backgrounds we study R-charged black holes and Schwarzschild-anti-deSitter black holes in (d+1)-dimensions. For non-conformal theories, we find that the exponent deviates from -1/d and as examples we study the non-extremal Klebanov-Tseytlin and Dp-brane geometries. We find an interesting relation between the deviation of the scaling exponent from the conformal value and the speed of sound.

Elena Caceres; Makoto Natsuume; Takashi Okamura

2007-06-04

383

Phase and Amplitude Control Ability using Spatial Light Modulators and Zero Path Length Difference Michelson Interferometer  

E-print Network

for the telescope with a circular aperture versus the shaped Spergel pupil aperture. The circular aperture displays, first proposed by David Spergel (ref. 1), reduces the effects of diffraction from the parent star Gaussian. This Gaussian nature optimally reduces the light-spreading effects due to diffraction along

Littman, Michael G.

384

Radial bunch compression: Path-length compensation in an rf photoinjector with a curved cathode  

E-print Network

or free-electron lasers (FELs) and for direct use in applications such as pulsed radiolysis [1] and time such as the free-electron laser by making them more compact and with shorter pulse duration, and could provide photoinjector is an ideal electron source for driving coherent spontaneous or superradiant free-electron lasers

Boyer, Edmond

385

Path-length-resolved forced-diffusive particle dynamics in Fourier-domain optical coherence tomography  

Microsoft Academic Search

—We present simulations of the decorrelation rate for a high and a low coherence light source in heterodyne light scattering geometry. Light scatters on an ensemble of particles of which the particle trajectories are calculated using a forced-diffusion model. The low coherence signal is constructed in the Fourier domain (as in Fourier-domain optical coherence tomography). I. INTRODUCTION The dynamics of

J. Kalkman; T. G. van Leeuwen; R. Sprik

2011-01-01

386

Experimental simulation of beam propagation over long path lengths using radio-frequency and magnetic traps  

NASA Astrophysics Data System (ADS)

An overview is given of the novel beam-dynamics experiments based on compact non-neutral plasma traps at Hiroshima University. We have designed and constructed two different classes of trap systems, one of which uses a radio-frequency electric field (Paul trap) and the other uses an axial magnetic field (Penning trap) for transverse plasma confinement. These systems are called "S-POD" (Simulator for Particle Orbit Dynamics). The S-POD systems can approximately reproduce the collective motion of a charged-particle beam propagating through long alternating-gradient (AG) quadrupole focusing channels using the Paul trap and long continuous focusing channels using the Penning trap. This allows us to study various beam-dynamics issues in compact and inexpensive experiments without relying on large-scale accelerators. So far, the linear Paul traps have been applied for the study of resonance-related issues including coherent-resonance-induced stop bands and their dependence on AG lattice structures, resonance crossing in fixed-field AG accelerators, ultralow-emittance beam stability, etc. The Penning trap with multi-ring electrodes has been employed primarily for the study of beam halo formation driven by initial distribution perturbations. In this paper, we briefly overview the S-POD systems, and then summarize recent experimental results on resonance effects and halo formation.

Okamoto, H.; Endo, M.; Fukushima, K.; Higaki, H.; Ito, K.; Moriya, K.; Yamaguchi, S.; Lund, S. M.

2014-01-01

387

High-Speed Path-Length Scanning with a Multiple-Pass Cavity Delay Line  

NASA Astrophysics Data System (ADS)

Techniques for high-speed delay scanning are important for low-coherence interferometry, optical coherence tomography, pump probe measurements, and other applications. We demonstrate a novel scanning delay line using a multiple-pass cavity. Differential delays are accumulated with each pass so that millimeter delays can be generated with tens of micrometer mirror displacements. With special design criteria, misalignment sensitivity can be dramatically reduced. The system is demonstrated to scan 6 m /s at 2-kHz repetition rates. Real-time optical coherence tomography imaging with 500 pixel images at four frames /s is performed. Using a Cr:forsterite laser source, we obtained axial image resolutions of 6 ?m with 92-dB sensitivity.

Hsiung, Pei-Lin; Li, Xingde; Chudoba, Christian; Hartl, Ingmar; Ko, Tony H.; Fujimoto, James G.

2003-02-01

388

A Multi-Baseline 12 GHz Atmospheric Phase Interferometer with One Micron Path Length Sensitivity  

E-print Network

We have constructed a five station 12 GHz atmospheric phase interferometer (API) for the Submillimeter Array (SMA) located near the summit of Mauna Kea, Hawaii. Operating at the base of unoccupied SMA antenna pads, each station employs a commercial low noise mixing block coupled to a 0.7 m off-axis satellite dish which receives a broadband, white noise-like signal from a geostationary satellite. The signals are processed by an analog correlator to produce the phase delays between all pairs of stations with projected baselines ranging from 33 to 261 m. Each baseline's amplitude and phase is measured continuously at a rate of 8 kHz, processed, averaged and output at 10 Hz. Further signal processing and data reduction is accomplished with a Linux computer, including the removal of the diurnal motion of the target satellite. The placement of the stations below ground level with an environmental shield combined with the use of low temperature coefficient, buried fiber optic cables provides excellent system stabili...

Kimberk, Robert S; Leiker, Patrick S; Blundell, Raymond; Nystrom, George U; Petitpas, Glen R; Test, John; Wilson, Robert W; Yamaguchi, Paul; Young, Kenneth H

2012-01-01

389

Ground-based measurements of atmospheric backscatter and absorption using coherent CO2 lidar  

NASA Technical Reports Server (NTRS)

In the present derivation of vertical profiles of atmospheric absorption and backscatter coefficients from coherent pulsed Doppler lidar by means of a slant path method, a strong seasonal variation of absorption and backscatter is evident throughout the lower troposphere. Measurements beyond the lower troposphere are hampered by modest pulse energy and lidar beam absorption, although small backscatter values are occasionally observed at midtropospheric levels during the winter months, when absorption is minimal. While a monomodal lognormal backscatter distribution is found within the lower boundary layer, evidence of a bimodal lognormal distribution is found at higher levels.

Rothermel, J.; Jones, W. D.

1985-01-01

390

FTIR-spectrometer-determined absorption coefficients of seven hydrazine fuel gases - Implications for laser remote sensing  

NASA Technical Reports Server (NTRS)

The absorption spectra of three hydrazines and four of their air-oxidation products were measured in the 9-12-micron spectral region with a Fourier transform infrared (FTIR) spectrometer with a 0.05-kayser resolution to determine absorption coefficients at CO2 and tunable diode laser wavelengths. The measurements agreed well with published CO2 laser determinations for many of the absorption coefficients, except where the published values are thought to be in error. The coefficients were then used to estimate the sensitivity for remote detection of these gases using CO2 and tunable diode lasers in long-path differential absorption measurements.

Molina, L. T.; Grant, W. B.

1984-01-01

391

Minimum physical length and the generalized uncertainty principle in string theory  

Microsoft Academic Search

A possible definition of path integrals for string theory is studied, based on a discretized version of Polyakov's generating functional. The finite resolution of string theory, as opposed to the infinite resolution in particle theory, clearly emerges from a renormalization group type analysis. We derive the existence of a minimum physical length (~10-33cm) and generalized form of the uncertainty principle,

Kenichi Konishi; Giampiero Paffuti; Paolo Provero

1990-01-01

392

Quantum Entanglement Molecular Absorption Spectrum Simulator  

NASA Technical Reports Server (NTRS)

Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

Nguyen, Quang-Viet; Kojima, Jun

2006-01-01

393

Continuous lengths of oxide superconductors  

DOEpatents

A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

Kroeger, Donald M. (Knoxville, TN); List, III, Frederick A. (Andersonville, TN)

2000-01-01

394

Magnon thermal mean free path in yttrium iron garnet  

NASA Astrophysics Data System (ADS)

The magnetothermal properties of monocrystalline yttrium iron garnet (YIG) are reported. The magnon contribution to both the thermal conductivity and specific heat at low temperatures has been determined by measuring these properties under an applied magnetic field, which allows us to freeze the magnon modes and isolate the phonon contribution relative to the zero-field behavior. These results are interpreted within the framework of a simple kinetic gas model for magnon heat conduction that allows us to estimate the magnon thermal mean free path, i.e., the inelastic scattering length scale for thermally driven bulk magnons. We observe this parameter to reach as high as approximately 100 ?m at 2 K. It tracks the acoustic phonon thermal mean free path closely and decreases rapidly as the temperature is increased. This relatively short length scale suggests that magnon modes at thermal energies in YIG are not solely or directly responsible for coherent macroscale thermal spin transport (e.g., in the spin Seebeck effect) at high temperatures. Instead, these results support a growing consensus that subthermal magnons, i.e., those at energies below about 30 ± 10 K, are important for spin transport in YIG at all temperatures. These results also emphasize that magnon effects should be considered wavelength dependent, and that magnon-magnon interactions may be just as important for thermal spin transport as magnon-phonon scattering. This, in turn, has implications for understanding the characteristic temperature and length scales involved in spin caloritronic phenomena.

Boona, Stephen R.; Heremans, Joseph P.

2014-08-01

395

Enzymatic reaction paths as determined by transition path sampling  

NASA Astrophysics Data System (ADS)

Enzymes are biological catalysts capable of enhancing the rates of chemical reactions by many orders of magnitude as compared to solution chemistry. Since the catalytic power of enzymes routinely exceeds that of the best artificial catalysts available, there is much interest in understanding the complete nature of chemical barrier crossing in enzymatic reactions. Two specific questions pertaining to the source of enzymatic rate enhancements are investigated in this work. The first is the issue of how fast protein motions of an enzyme contribute to chemical barrier crossing. Our group has previously identified sub-picosecond protein motions, termed promoting vibrations (PVs), that dynamically modulate chemical transformation in several enzymes. In the case of human heart lactate dehydrogenase (hhLDH), prior studies have shown that a specific axis of residues undergoes a compressional fluctuation towards the active site, decreasing a hydride and a proton donor--acceptor distance on a sub-picosecond timescale to promote particle transfer. To more thoroughly understand the contribution of this dynamic motion to the enzymatic reaction coordinate of hhLDH, we conducted transition path sampling (TPS) using four versions of the enzymatic system: a wild type enzyme with natural isotopic abundance; a heavy enzyme where all the carbons, nitrogens, and non-exchangeable hydrogens were replaced with heavy isotopes; and two versions of the enzyme with mutations in the axis of PV residues. We generated four separate ensembles of reaction paths and analyzed each in terms of the reaction mechanism, time of barrier crossing, dynamics of the PV, and residues involved in the enzymatic reaction coordinate. We found that heavy isotopic substitution of hhLDH altered the sub-picosecond dynamics of the PV, changed the favored reaction mechanism, dramatically increased the time of barrier crossing, but did not have an effect on the specific residues involved in the PV. In the mutant systems, we observed changes in the reaction mechanism and altered contributions of the mutated residues to the enzymatic reaction coordinate, but we did not detect a substantial change in the time of barrier crossing. These results confirm the importance of maintaining the dynamics and structural scaffolding of the hhLDH PV in order to facilitate facile barrier passage. We also utilized TPS to investigate the possible role of fast protein dynamics in the enzymatic reaction coordinate of human dihydrofolate reductase (hsDHFR). We found that sub-picosecond dynamics of hsDHFR do contribute to the reaction coordinate, whereas this is not the case in the E. coli version of the enzyme. This result indicates a shift in the DHFR family to a more dynamic version of catalysis. The second inquiry we addressed in this thesis regarding enzymatic barrier passage concerns the variability of paths through reactive phase space for a given enzymatic reaction. We further investigated the hhLDH-catalyzed reaction using a high-perturbation TPS algorithm. Though we saw that alternate reaction paths were possible, the dominant reaction path we observed corresponded to that previously elucidated in prior hhLDH TPS studies. Since the additional reaction paths we observed were likely high-energy, these results indicate that only the dominant reaction path contributes significantly to the overall reaction rate. In conclusion, we show that the enzymes hhLDH and hsDHFR exhibit paths through reactive phase space where fast protein motions are involved in the enzymatic reaction coordinate and exhibit a non-negligible contribution to chemical barrier crossing.

Masterson, Jean Emily

396

Assessing perceptions about hazardous substances (PATHS): the PATHS questionnaire.  

PubMed

How people perceive the nature of a hazardous substance may determine how they respond when potentially exposed to it. We tested a new Perceptions AbouT Hazardous Substances (PATHS) questionnaire. In Study 1 (N = 21), we assessed the face validity of items concerning perceptions about eight properties of a hazardous substance. In Study 2 (N = 2030), we tested the factor structure, reliability and validity of the PATHS questionnaire across four qualitatively different substances. In Study 3 (N = 760), we tested the impact of information provision on Perceptions AbouT Hazardous Substances scores. Our results showed that our eight measures demonstrated good reliability and validity when used for non-contagious hazards. PMID:23104995

Rubin, G James; Amlôt, Richard; Page, Lisa; Pearce, Julia; Wessely, Simon

2013-08-01

397

Cryogenic Absorption Cells Operating Inside a Bruker IFS-125HR: First Results for 13CH4 at 7 Micrometers  

NASA Technical Reports Server (NTRS)

New absorption cells designed specifically to achieve stable temperatures down to 66 K inside the sample compartment of an evacuated Bruker IFS-125HR Fourier transform spectrometer (FTS) were developed at Connecticut College and tested at the Jet Propulsion Laboratory (JPL). The temperature stabilized cryogenic cells with path lengths of 24.29 and 20.38 cm were constructed of oxygen free high conductivity (OFHC) copper and fitted with wedged ZnSe windows using vacuum tight indium seals. In operation, the temperature-controlled cooling by a closed-cycle helium refrigerator achieved stability of 0.01 K. The unwanted absorption features arising from cryodeposits on the cell windows at low temperatures were eliminated by building an internal vacuum shroud box around the cell which significantly minimized the growth of cryodeposits. The effects of vibrations from the closed-cycle helium refrigerator on the FTS spectra were characterized. Using this set up, several high-resolution spectra of methane isotopologues broadened with nitrogen were recorded in the 1200-1800 per centimeter spectral region at various sample temperatures between 79.5 and 296 K. Such data are needed to characterize the temperature dependence of spectral line shapes at low temperatures for remote sensing of outer planets and their moons. Initial analysis of a limited number of spectra in the region of the R(2) manifold of the v4 fundamental band of 13CH4 indicated that an empirical power law used for the temperature dependence of the N2-broadened line widths would fail to fit the observed data in the entire temperature range from 80 to 296 K; instead, it follows a temperature-dependence similar to that reported by Mondelain et al. [17,18]. The initial test was very successful proving that a high precision Fourier transform spectrometer with a completely evacuated optical path can be configured for spectroscopic studies at low temperatures relevant to the planetary atmospheres.

Sung, K.; Mantz, A. W.; Smith, M. A. H.; Brown, L. R.; Crawford, T. J.; Devi, V. M.; Benner, D. C.

2010-01-01

398

Cryogenic absorption cells operating inside a Bruker IFS-125HR: First results for 13CH4 at 7 ?m  

NASA Astrophysics Data System (ADS)

New absorption cells designed specifically to achieve stable temperatures down to 66 K inside the sample compartment of an evacuated Bruker IFS-125HR Fourier transform spectrometer (FTS) were developed at Connecticut College and tested at the Jet Propulsion Laboratory (JPL). The temperature stabilized cryogenic cells with path lengths of 24.29 and 20.38 cm were constructed of oxygen free high conductivity (OFHC) copper and fitted with wedged ZnSe windows using vacuum tight indium seals. In operation, the temperature-controlled cooling by a closed-cycle helium refrigerator achieved stability of ±0.01 K. The unwanted absorption features arising from cryodeposits on the cell windows at low temperatures were eliminated by building an internal vacuum shroud box around the cell which significantly minimized the growth of cryodeposits. The effects of vibrations from the closed-cycle helium refrigerator on the FTS spectra were characterized. Using this set up, several high-resolution spectra of methane isotopologues broadened with nitrogen were recorded in the 1200-1800 cm-1 spectral region at various sample temperatures between 79.5 and 296 K. Such data are needed to characterize the temperature dependence of spectral line shapes at low temperatures for remote sensing of outer planets and their moons. Initial analysis of a limited number of spectra in the region of the R(2) manifold of the ?4 fundamental band of 13CH4 indicated that an empirical power law used for the temperature dependence of the N2-broadened line widths would fail to fit the observed data in the entire temperature range from 80 to 296 K; instead, it follows a temperature-dependence similar to that reported by Mondelain et al. [17,18]. The initial test was very successful proving that a high precision Fourier transform spectrometer with a completely evacuated optical path can be configured for spectroscopic studies at low temperatures relevant to the planetary atmospheres.

Sung, K.; Mantz, A. W.; Smith, M. A. H.; Brown, L. R.; Crawford, T. J.; Devi, V. M.; Benner, D. C.

2010-08-01

399

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

E-print Network

status play in shaping how people conceptualize water solutions? 3) What role does water scarcity play selected based on their diversity in development status and water scarcity (Figure 1) · Participants no path (2 = 5.19, p = 0.02, = 0.22). Water Scarcity · Respondents from water-scarce sites were found

Hall, Sharon J.

400

The Evolution of Energy Absorption Systems for Crashworthy Helicopter Seats  

Microsoft Academic Search

The objective of this paper is to trace the development history of the energy absorbing systems used on crashworthy helicopter seats from their beginnings in the early 1960's to the current time. Its purpose is to assess the state-of-the-art of these systems and to prescribe the path of future needs and efforts. This paper emphasizes the evolution of energy absorption

Stanley P. Desjardins

2006-01-01

401

Path correlation considered prioritized burst segmentation for quality of service support in optical burst switching networks  

NASA Astrophysics Data System (ADS)

Burst segmentation (BS) is a high-efficiency contention resolution scheme in bufferless optical burst switching (OBS) networks. A prioritized BS scheme for quality of service (QoS) support is developed. Unlike the existing work on the BS scheme, the proposed BS model considers path-correlated factors, such as path length, the adjoining paths carrying traffic on a given path, and the multipriority traffic coming from all paths. Byte loss probability for high-priority and low-priority bursts under the time-based assembly approach and the length-based assembly approach to estimate the performance of the proposed BS scheme by comparing the cumulative distribution function of a burst length in an OBS ingress node (source) with that in an egress node (destination) is introduced. A preemptive BS policy for different priority bursts is proposed to support the QoS of the OBS network. Finally, a simulation is given to validate the proposed analytical model in an existing OBS network with two priority bursts. It is shown that the proposed BS scheme can realize the service differentiation for multipriority traffic under the consideration of network topology-dependent parameters.

Hou, Rui; Changyue, Jiana; He, Tingting; Yu, Jianwei; Lei, Bo; Mao, Tengyue

2013-04-01

402

Electron Inelastic-Mean-Free-Path Database  

National Institute of Standards and Technology Data Gateway

SRD 71 NIST Electron Inelastic-Mean-Free-Path Database (PC database, no charge)   This database provides values of electron inelastic mean free paths (IMFPs) for use in quantitative surface analyses by AES and XPS.

403

Model for Delay Faults Based upon Paths  

Microsoft Academic Search

Delay testing of combinational logic in a clocked environment is analyzed. A model based upon paths is introduced for delay faults. Any path with a total delay exceeding the clock interval is called a \\

Gordon L. Smith

1985-01-01

404

[Correlation and path analyses of phenotypic traits and body mass of transgenic carp with growth hormone gene of salmon].  

PubMed

Thirty 2-year old transgenic carp individuals with growth hormone gene of salmon were randomly selected to study the affecting degree of their phenotypic traits on their body mass by the methods of correlation and path analyses, with 30 individuals of non-transgenic carp as the control, aimed to ascertain the main phenotypic parameters affecting the body mass of the transgenic and non-transgenic carps. The test phenotypic traits were total length, body length, body height, least height of caudal peduncle, length of caudal peduncle, length of head, snout length, eyes horizontal diameter, inter-orbital distance, and body depth. Correlation analysis showed that for both of the transgenic and non-transgenic carps, most of the test phenotypic parameters were significantly correlated to body mass (P<0.01). Path analysis indicated that for transgenic carp, its body length and body height were the main predictable factors affecting body mass, with the path coefficient being 0.572 and 0.415, respectively, while for non-transgenic carp, its body depth and tail length were the main predictable factors affecting body mass, with the path coefficient being 0.610 and 0.377, respectively. PMID:22007470

Liu, Chun-lei; Chang, Yu-mei; Liang, Li-qun; Xu, Li-hua; Liu, Jin-liang; Chi, Bing-jie; Wu, Xue-gong

2011-07-01

405

Characteristic length of glass transition  

NASA Astrophysics Data System (ADS)

The characteristic length of the glass transition (? _? ) is based on the concept of cooperatively rearranging regions (CRR's) by Adam & Gibbs (1965): ? _? is the diameter of one CRR. In the theoretical part of the talk a formula is derived how this length can be calculated from calorimetric data of the transformation interval. The approach is based on fluctuations in natural functional subsystems. The corresponding thermodynamics is represented e.g. in a book of the author (E. Donth, Relaxation and Thermodynamics in Polymers. Glass Transition, Akademie-Verlag, Berlin 1992). A typical value for this length is 3 nanometers. In the experimental part several examples are reported to enlarge the experimental evidence for such a length: Squeezing the glass transition in the amorphous layers of partially crystallized PET (C. Schick, Rostock), glass transition of small-molecule glass formers in a series of nanoscaled pores of porous glasses (F. Kremer, Leipzig), comparison with a concentration fluctuation model in homogeneous polymer mixtures (E.W. Fischer, Mainz), and, from our laboratory, backscaling to ? _? across the main transition from the entanglement spacing in several amorphous polymers such as PVAC, PS, NR, and some polymer networks. Rouse backscaling was possible in the ? ? splitting region of several poly(n alkyl methacrylates) resulting in small characteristic lengths of order 1 nanometer near the onset of ? cooperativity. In a speculative outlook a dynamic density pattern is presented, having a cellular structure with higher density and lower mobility of the cell walls. It will be explained, with the aid of different thermal expansion of wall and clusters, how the clusters within the cells maintain a certain mobility far below the glass temperature.

Donth, E.

1996-03-01

406

Pairing versus quarteting coherence length  

NASA Astrophysics Data System (ADS)

We systematically analyze the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density-dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have, in all considered cases, a long-range character inside the nucleus and a decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in the continuum is investigated. Strong shell effects are put in evidence, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We provide evidence of the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the ? -particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free ? -particle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

Delion, D. S.; Baran, V. V.

2015-02-01

407

Multiple Paths to Encephalization and Technical Civilizations  

NASA Astrophysics Data System (ADS)

We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels.

Schwartzman, David; Middendorf, George

2011-12-01

408

Understanding Delay Variations on Internet Paths  

Microsoft Academic Search

In this paper we investigate the network factors that may affect the user perceived end-to-end delay jitter. In parti cular, we iden- tify the following three major factors: per hop queueing delay varia- tions along an Internet path; intra-domain multi-path routing; and inter- domain route (i.e., AS path) alterations. By studying traceroutedata collected on Internet paths, we find that 1)

Zhenhai Duan; Kuai Xu; Zhi-Li Zhang

409

Physarum can compute shortest paths.  

PubMed

Physarum polycephalum is a slime mold that is apparently able to solve shortest path problems. A mathematical model has been proposed by Tero et al. (Journal of Theoretical Biology, 244, 2007, pp. 553-564) to describe the feedback mechanism used by the slime mold to adapt its tubular channels while foraging two food sources s(0) and s(1). We prove that, under this model, the mass of the mold will eventually converge to the shortest s(0)-s(1) path of the network that the mold lies on, independently of the structure of the network or of the initial mass distribution. This matches the experimental observations by Tero et al. and can be seen as an example of a "natural algorithm", that is, an algorithm developed by evolution over millions of years. PMID:22732274

Bonifaci, Vincenzo; Mehlhorn, Kurt; Varma, Girish

2012-09-21

410

Interior point path following algorithms  

SciTech Connect

In the last few years the research on interior point methods for linear programming has been dominated by the study of primal-dual algorithms. Most of these methods are easily extended to monotone linear complementarity problems, preserving the convergence properties. In this talk we concentrate mostly on the basic techniques used for following the primal-dual central path associated with a monotone horizontal LCP. The emphasis is on feasible interior point methods, but we also describe the main techniques for dealing with infeasible starting points. We define the central path and construct homotopy methods for following it, with iterations based on the application of Newton`s method. We show how these Newton steps are combinations of two special directions, the affine-scaling and the centering direction, and describe how this fact can be used to generate large step methods with low polynomial bounds and superlinear rates of convergence.

Gonzaga, C.C.

1994-12-31

411

Path entanglement of surface plasmons  

NASA Astrophysics Data System (ADS)

Metals can sustain traveling electromagnetic waves at their surfaces supported by the collective oscillations of their free electrons in unison. Remarkably, classical electromagnetism captures the essential physics of these ‘surface plasma’ waves using simple models with only macroscopic features, accounting for microscopic electron–electron and electron–phonon interactions with a single, semi-empirical damping parameter. Nevertheless, in quantum theory these microscopic interactions could be important, as any substantial environmental interactions could decohere quantum superpositions of surface plasmons, the quanta of these waves. Here we report a measurement of path entanglement between surface plasmons with 95% contrast, confirming that a path-entangled state can indeed survive without measurable decoherence. Our measurement suggests that elastic scattering mechanisms of the type that might cause pure dephasing in plasmonic systems must be weak enough not to significantly perturb the state of the metal under the experimental conditions we investigated.

Fakonas, James S.; Mitskovets, Anna; Atwater, Harry A.

2015-02-01

412

Squeezed states and path integrals  

NASA Technical Reports Server (NTRS)

The continuous-time regularization scheme for defining phase-space path integrals is briefly reviewed as a method to define a quantization procedure that is completely covariant under all smooth canonical coordinate transformations. As an illustration of this method, a limited set of transformations is discussed that have an image in the set of the usual squeezed states. It is noteworthy that even this limited set of transformations offers new possibilities for stationary phase approximations to quantum mechanical propagators.

Daubechies, Ingrid; Klauder, John R.

1992-01-01

413

Path Integrals and Coherent States  

E-print Network

propagator, on the other hand, is ^ / ( ) iHT U T e- = ^( ) 1 /U iH = - Motivations for a path integral evolutions as a composition of infinitesimal evolutions. ^( ) 1 /U iH = - #12;DIRAC: is there a Lagrangian ''| | ' | | | | | | N iHT iH iH N N N N iH N N i q e q q e q q e q q e q dq dq dq

de Aguiar, Marcus A. M.

414

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES  

E-print Network

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES UNIVERFITY OF CALIFORNIA, BERKELEY Agogino, Kai Goebel SatnamAlag University of California,Berkeley CaliforniaPATH Research Report UCB-ITS-PRR-97-31 This work was performed as part of the CaliforniaPATH Program of the University of California

Agogino, Alice M.

415

Quantifying the Causes of Path Inflation  

Microsoft Academic Search

Researchers have shown that the Internet exhibits path inflation - end-to-end paths can be significantly longer than necessary. We present a trace-driven study of 65 ISPs that characterizes the root causes of path inflation, namely topology and routing policy choices within an ISP, between pairs of ISPs, and across the global Inter- net. To do so, we develop and validate

Neil Spring; Ratul Mahajan; Thomas Anderson

2003-01-01

416

Chip layout optimization using critical path weighting  

Microsoft Academic Search

A chip layout procedure for optimizing the performance of critical timing paths in a synchronous digital circuit is presented. The procedure uses the path analysis data produced by a static timing analysis program to generate weights for critical nets on clock and data paths. These weights are then used to bias automatic placement and routing in the layout program. This

A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kozak; M. Wiesel

1984-01-01

417

Accelerating cleanup: Paths to closure  

SciTech Connect

This document was previously referred to as the Draft 2006 Plan. As part of the DOE`s national strategy, the Richland Operations Office`s Paths to Closure summarizes an integrated path forward for environmental cleanup at the Hanford Site. The Hanford Site underwent a concerted effort between 1994 and 1996 to accelerate the cleanup of the Site. These efforts are reflected in the current Site Baseline. This document describes the current Site Baseline and suggests strategies for further improvements in scope, schedule and cost. The Environmental Management program decided to change the name of the draft strategy and the document describing it in response to a series of stakeholder concerns, including the practicality of achieving widespread cleanup by 2006. Also, EM was concerned that calling the document a plan could be misconstrued to be a proposal by DOE or a decision-making document. The change in name, however, does not diminish the 2006 vision. To that end, Paths to Closure retains a focus on 2006, which serves as a point in time around which objectives and goals are established.

Edwards, C.

1998-06-30

418

Ranking nodes according to their path-complexity  

NASA Astrophysics Data System (ADS)

Thermalization is one of the most important phenomena in statistical physics. Often, the transition probabilities between different states in the phase space is or can be approximated by constants. In this case, the system can be described by Markovian transition kernels, and when the phase space is discrete, by Markov chains. In this paper, we introduce a macroscopic entropy on the states of paths of length $k$ and, studying the recursion relation, obtain a fixed point entropy. This analysis leads to a centrality approach to Markov chains entropy.

Caravelli, Francesco

2015-04-01

419

Most likely paths to error when estimating the mean of a reflected random walk  

E-print Network

Most likely paths to error when estimating the mean of a reflected random walk Ken R. Duffya, Sean. Duffy), meyn@illinois.edu (Sean P. Meyn) Preprint submitted to Elsevier June 2, 2010 #12;2 1's recursion also governs the evolution of the queue-length at certain single server queues, such as the M/M/1

Duffy, Ken

420

Longest paths in strong spanning oriented subgraphs of strong semicomplete multipartite digraphs  

Microsoft Academic Search

A digraph obtained by replacing each edge of a complete multipartite graph by an arc or a pair of mutually opposite arcs with the same end vertices is called a semicomplete multipartite digraph. L. Volkmann (1998) raised the following question: Let D be a strong semicomplete multipartite digraph with a longest path of length l. Does there exist a strong

Gregory Gutin; Meike Tewes; Anders Yeo

2000-01-01

421

A rapid method to derive horizontal distributions of trace gases and aerosols near the surface using multi-axis differential optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

We apply a novel experimental procedure for the rapid measurement of the average volume mixing ratios (VMRs) and horizontal distributions of trace gases such as NO2, SO2, and HCHO in the boundary layer, which was recently suggested by Sinreich et al. (2013). The method is based on two-dimensional scanning multi-axis differential optical absorption spectroscopy (MAX-DOAS). It makes use of two facts (Sinreich et al., 2013): first, the light path for observations at 1° elevation angle traverses mainly air masses located close to the ground (typically < 200 m); second, the light path length can be calculated using the simultaneous measured absorption of the oxygen dimer O4. Thus, the average value of the trace gas VMR in the atmospheric layer between the surface and the particular altitude, for which this observation was sensitive, can be calculated. Compared to the originally proposed method, we introduce several important modifications and improvements: We apply the method only to measurements at 1° elevation angle (besides zenith view), for which the uncertainties of the retrieved values of the VMRs and surface extinctions are especially small. Using only 1° elevation angle for off-axis observation also allows an increased temporal resolution. We determine (and apply) correction factors (and their uncertainties) directly as function of the measured O4 absorption. Finally, the method is extended to trace gases analysed at other wavelengths and also to the retrieval of aerosol extinction. Depending on atmospheric visibility, the typical uncertainty of the results ranges from about 20% to 30%. We apply the rapid method to observations of a newly-developed ground-based multifunctional passive differential optical absorption spectroscopy (GM-DOAS) instrument in the north-west outskirts near Hefei in China. We report NO2, SO2, and HCHO VMRs and aerosol extinction for four azimuth angles and compare these results with those from simultaneous long-path DOAS observations. Good agreement is found (squares of the correlation coefficients for NO2, SO2, and HCHO were 0.92, 0.85, and 0.60, respectively), verifying the reliability of this novel method. Similar agreement is found for the comparison of the aerosol extinction with results from visibility meters. Future studies may conduct measurements using a larger number of azimuth angles to increase the spatial resolution.

Wang, Y.; Li, A.; Xie, P. H.; Wagner, T.; Chen, H.; Liu, W. Q.; Liu, J. G.

2014-06-01

422

Preserving Topology Confidentiality in Inter-Domain Path Computation Using a Path-Key-Based Mechanism  

Microsoft Academic Search

Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (TE) Label Switched Paths (LSPs) may be computed by Path Computation Elements (PCEs). Where the TE LSP crosses multiple domains, such as Autonomous Systems (ASes), the path may be computed by multiple PCEs that cooperate, with each responsible for computing a segment of the path. However, in some cases (e.g.,

A. Farrel

423

Absorption spectroscopy of individual single-walled carbon nanotubes  

E-print Network

Absorption spectroscopy of individual single-walled carbon nanotubes Stéphane Berciaud,a Laurent-walled carbon nanotubes (SWNTs) lead to heterogeneous samples containing mixtures of metallic and semiconducting species with a variety of lengths and defects. Optical detection at the single nanotube level should thus

Boyer, Edmond

424

Measurement of the expansion of picosecond laser-produced plasmas using resonance absorption profile spectroscopy  

Microsoft Academic Search

Time-resolved, submicron density scale lengths in picosecond laser-produced plasmas are measured using resonance absorption profile spectroscopy. The density scale length at critical density is inferred from the angle and polarization dependence of the absorption of a picosecond laser pulse in a performed plasma. The early expansion of picosecond laser-produced plasmas produced from an Au target is studied, with measured scale

O. L. Landen; D. G. Stearns; E. M. Campbell

1989-01-01

425

Farewell to the Voyagers: Measuring the Local ISM in the Immediate Path of the Two Voyager Spacecraft  

NASA Astrophysics Data System (ADS)

Astronomical observations of the interstellar medium often struggle to measure fundamental physical properties of the gas on small scales because most observations are averaged along the line of sight, leading to difficulties in evaluating pressure equilibrium, turbulence, magnetic field structure, and volume density. The local ISM has helped in this regard by providing relatively simple ISM absorption profiles over short path lengths, with low column densities only detectable with strong transitions in the UV . On August 25, 2012, the first human-made object, the Voyager 1 spacecraft, crossed the heliosphere, effectively leaving the solar system and entering the galactic interstellar environment. Voyager 2 is expected to do the same in the coming years, and over the next decade both spacecraft will continue to make daily measurements of fundamental physical properties. We propose to make the first observations of nearby stars along the same line of sight as the current locations of the Voyager spacecraft in order to measure the same interstellar material. The proposed observations are of the very closest stars in these directions and will provide measurements of the kinematic structure, electron density, temperature and turbulence, elemental abundances and small scale structure by comparing two closely spaced sight lines. With both HST and the Voyager spacecraft approaching the end of long and fruitful missions, we have the opportunity to acquire a unique dataset which synthesizes the independent and complimentary in situ observations with the shortest possible line-of-sight observations, to provide an unprecedented study of the galactic ISM surrounding the Sun.

Redfield, Seth

2014-10-01

426

Collisional absorption in aluminum.  

PubMed

The interaction of ultrashort laser pulses with matter is a topic of growing interest. In particular, recent developments on free-electron lasers have opened an unexplored field in which many interesting physical phenomena are to be expected. Since hydrodynamic descriptions of the interaction process need a microscopic "input," a quantum statistical theory of energy absorption by matter is required. We present a kinetic theory of collisional absorption in dense plasmas and analyze the electron-ion collision frequency in warm dense aluminum in dependence on laser frequency and temperature. PMID:16906987

Semkat, D; Redmer, R; Bornath, Th

2006-06-01

427

Absorption heat pump system  

DOEpatents

An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

Grossman, Gershon (Oak Ridge, TN); Perez-Blanco, Horacio (Knoxville, TN)

1984-01-01

428

Welding arc length control system  

NASA Technical Reports Server (NTRS)

The present invention is a welding arc length control system. The system includes, in its broadest aspects, a power source for providing welding current, a power amplification system, a motorized welding torch assembly connected to the power amplification system, a computer, and current pick up means. The computer is connected to the power amplification system for storing and processing arc weld current parameters and non-linear voltage-ampere characteristics. The current pick up means is connected to the power source and to the welding torch assembly for providing weld current data to the computer. Thus, the desired arc length is maintained as the welding current is varied during operation, maintaining consistent weld penetration.

Iceland, William F. (Inventor)

1993-01-01

429

Variable focal length deformable mirror  

DOEpatents

A variable focal length deformable mirror has an inner ring and an outer ring that simply support and push axially on opposite sides of a mirror plate. The resulting variable clamping force deforms the mirror plate to provide a parabolic mirror shape. The rings are parallel planar sections of a single paraboloid and can provide an on-axis focus, if the rings are circular, or an off-axis focus, if the rings are elliptical. The focal length of the deformable mirror can be varied by changing the variable clamping force. The deformable mirror can generally be used in any application requiring the focusing or defocusing of light, including with both coherent and incoherent light sources.

Headley, Daniel (Albuquerque, NM); Ramsey, Marc (Albuquerque, NM); Schwarz, Jens (Albuquerque, NM)

2007-06-12

430

Measurement of the Domain Growth Kinetics in Multidomain Nematic Liquid Crystal Polymers by Means of the Worm Like Path Model for Multiple Scattering  

Microsoft Academic Search

The rate of domain growth in nematic side chain polymer samples is measured using the worm like path model for multiple scattering of light. The worm like path model which describes multiple scattaering in terms of the optical persistence length is found to apply both to multiple scattering in liquid crystal polymer films as well as to model polystyrene despersions.

S. J. Picken; R. J. Van Wijk; J. W. Th. Lichtenbelt; J. B. Westerink; P. J. Van Klink

1995-01-01

431

Modulated Tool-Path (MTP) Chip Breaking System  

SciTech Connect

The Modulated Tool-Path (MTP) Chip Breaking System produces user-selectable chip lengths and workpiece finishes and is compatible with any material, workpiece shape, and depth of cut. The MTP chip breaking system consistently creates the desired size of chips regardless of workpiece size, shape, or material, and the machine operator does not need to make any adjustments during the machining operation. The system's programmer configures the part program that commands the machine tool to move in a specific fashion to deliver the desired part size, shape, chip length, and workpiece surface finish. The MTP chip breaking system helps manufacturers avoid the detrimental effects of continuous chips, including expensive repair costs, delivery delays, and hazards to personnel.

Graham, K. B.

2010-04-01

432

Broadband solar absorption enhancement via periodic nanostructuring of electrodes  

PubMed Central

Solution processed colloidal quantum dot (CQD) solar cells have great potential for large area low-cost photovoltaics. However, light utilization remains low mainly due to the tradeoff between small carrier transport lengths and longer infrared photon absorption lengths. Here, we demonstrate a bottom-illuminated periodic nanostructured CQD solar cell that enhances broadband absorption without compromising charge extraction efficiency of the device. We use finite difference time domain (FDTD) simulations to study the nanostructure for implementation in a realistic device and then build proof-of-concept nanostructured solar cells, which exhibit a broadband absorption enhancement over the wavelength range of ? = 600 to 1100?nm, leading to a 31% improvement in overall short-circuit current density compared to a planar device containing an approximately equal volume of active material. Remarkably, the improved current density is achieved using a light-absorber volume less than half that typically used in the best planar devices. PMID:24121519

Adachi, Michael M.; Labelle, André J.; Thon, Susanna M.; Lan, Xinzheng; Hoogland, Sjoerd; Sargent, Edward H.

2013-01-01

433

Flowing liquid-sheet jet for cavity ring-down absorption measurements.  

PubMed

The use of a flowing liquid-sheet jet in cavity ring-down absorption measurements is described. A mechanical gear pump was used to pump solvent at low pressure through a circular orifice. The resulting cylindrical jet of solvent was fired at a flat surface. A flat sheet of liquid was formed in a small portion of the resulting spray, which was sufficiently stable to be positioned at the Brewster angle in a linear ring-down cavity setup operated with a pulsed laser. The path length through a sheet-jet of ethylene glycol was measured to be 23.2 +/- 0.6 mum. Malachite Green dye was used as an analyte to demonstrate a linear dynamic range of 12.6 dB (73.9 nM to 1.34 microM). The limit of detection for the system was determined to be alpha LOD = 0.0162 cm(-1), or 71 nM (at epsilon = 9.975 x 10(4) M(-1) cm(-1), 628 nm, 3 sigma). The technique is shown to have promise for analytical and spectroscopic measurements, for example, in studies of gas-liquid interfaces. PMID:16878901

Alexander, A J

2006-08-01

434

Measurement of Glucose Level Exploiting a Relative Optical Absorption at Discrete Probe Wavelengths  

NASA Astrophysics Data System (ADS)

A practical and viable scheme for measuring the concentration of a glucose solution was proposed and verified based on the relative optical absorbance at discrete probe wavelengths instead of the continuous broad band absorption spectra. The relative absorbance at each of the probe wavelengths was obtained with respect to the absorbance at a reference wavelength. The single reference wavelength (1310 nm) and a group of four different probe wavelengths (1064, 1550, 1685, 1798 nm) were selected to exhibit the glucose absorbance with opposite signs, thereby enhancing the accuracy of the prediction. The glucose level was decently estimated by taking the average of all of the individual prediction values available from each of the probe wavelengths, with the standard error of prediction of ˜28 mg/dL. And the influence of the ambient temperature upon the prediction of the glucose concentration was examined to compensate for the error induced by the variation in it. The effect of both the amplification of the sensor signal and the optical path length upon the performance of the proposed scheme was briefly addressed as well.

Kim, Ki-Do; Son, Geun-Sik; Lim, Seong-Soo; Lee, Sang-Shin

2009-07-01

435

Leading dimensions in absorptive root trait variation across 96 subtropical forest species.  

PubMed

Absorptive root traits show remarkable cross-species variation, but major root trait dimensions across species have not been defined. We sampled first-order roots and measured 14 root traits for 96 angiosperm woody species from subtropical China, including root diameter, specific root length, stele diameter, cortex thickness, root vessel size and density, mycorrhizal colonization rate, root branching intensity, tissue density, and concentrations of carbon and nitrogen ([N]). Root traits differed in the degree of variation and phylogenetic conservatism, but showed predictable patterns of cross-trait coordination. Root diameter, cortex thickness and stele diameter displayed high variation across species (coefficient of variation (CV)=0.51-0.69), whereas the stele:root diameter ratio and [N] showed low variation (CV<0.32). Root diameter, cortex thickness and stele diameter showed a strong phylogenetic signal across species, whereas root branching traits did not, and these two sets of traits were segregated onto two nearly orthogonal (independent) principal component analysis (PCA) axes. Two major dimensions of root trait variation were found: a diameter-related dimension potentially integrating root construction, maintenance, and persistence with mycorrhizal colonization, and a branching architecture dimension expressing root plastic responses to the environment. These two dimensions may offer a promising path for better understanding root trait economics and root ecological strategies world-wide. PMID:24824672

Kong, Deliang; Ma, Chengen; Zhang, Qian; Li, Le; Chen, Xiaoyong; Zeng, Hui; Guo, Dali

2014-08-01

436

Diode-laser-based sensor for ultraviolet absorption measurements of atomic mercury  

NASA Astrophysics Data System (ADS)

A new sensor has been developed for measuring atomic mercury using absorption spectroscopy with 254-nm radiation generated from two sum-frequency-mixed diode lasers. Beams from a 375-nm external-cavity diode laser and a 784-nm distributed feedback diode laser are mixed in a beta-barium-borate crystal to generate approximately 4 nW of ultraviolet radiation. The development of the sensor is described along with extensive characterization experiments in a mercury vapor cell in the laboratory. An accuracy of ±6% in the absolute concentration of atomic mercury has been demonstrated by comparison with equilibrium vapor pressure calculations. The detection limit is approximately 0.1 parts per billion of atomic mercury in a meter path length for 300-K gas and a 10-s integration time. The insensitivity of the sensor to broadband attenuation is demonstrated. Measurements of collision-broadening coefficients for air, N2, Ar, and CO2 are reported, and implementation of wavelength-modulation spectroscopy with the sensor is demonstrated. Finally, results are presented from measurements with the sensor in situ in the exhaust stream of an actual coal-fired combustor.

Anderson, T. N.; Magnuson, J. K.; Lucht, R. P.

2007-04-01

437

Millimeter-Wave Propagation in Moist Air: Model Versus Path Data  

Microsoft Academic Search

ABSTRACT 1.,INTRODUCTION 2.,MILLIMETER-WAVE CHARACTERISTICS OF MOIST AIR 2.1 The Propagation,Model,MPM 2.1.1 Local Line Absorption and Dispersion 2.1.2 Continuum Spectra for Air 2.1.3 Hydrosol Continuum (Haze and Fog) 2.2 Atmospheric Turbulence 2.3 Multipath Fading 3.,BOULDER LOS EXPERIMENT 3.1 Link Description (27-km Path) 3.2 Data Acquisition 3.3 Calibration Procedure (O.l-km Path) 4. OBSERVATIONS, PREDICTIONS, AND RESULTS 4.1 Received Amplitude Levels 4.2 Predicted

H. J. Liebe; K. C. Allen; R. H. Espeland; E. J. Violette

1985-01-01

438

Mechanics of the crack path formation  

NASA Technical Reports Server (NTRS)

A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented here.

Rubinstein, Asher A.

1989-01-01

439

Effect of defoliation upon root growth, phosphate absorption and respiration in nutrient-limited tundra graminoids  

Microsoft Academic Search

Moderate experimental defoliation stimulated root respiration and phosphate absorption in two tundra graminoids, Eriophorum vaginatum and Carex aquatilis, growing under nutrient-limited field conditions in northern Alaska. The increase in phosphate absorption rate following defoliation of Eriophorum was associated with a decrease in root phosphate and available carbohydrate contents per unit root length but a constant root nitrogen content. Only after

F. Stuart Chapin; Mari Slack

1979-01-01

440

New techniques for optical absorption measurement of implanted nanoparticles in float glass  

Microsoft Academic Search

New techniques are reported for optical absorption and waveguide loss measurement of copper, gold and silver implanted float glass. Implantations were carried out on the tin face of the float glass since this face is an optical waveguide. Specially made triangle shape masks were used during implantation to study the optical loss–implant length relation. Absorption coefficients were extracted as 2.4

I Okur; P. D Townsend; P. J Chandler

1999-01-01

441

Path Complexity in Virtual Water Maze Navigation: Differential Associations with Age, Sex, and Regional Brain Volume.  

PubMed

Studies of human navigation in virtual maze environments have consistently linked advanced age with greater distance traveled between the start and the goal and longer duration of the search. Observations of search path geometry suggest that routes taken by older adults may be unnecessarily complex and that excessive path complexity may be an indicator of cognitive difficulties experienced by older navigators. In a sample of healthy adults, we quantify search path complexity in a virtual Morris water maze with a novel method based on fractal dimensionality. In a two-level hierarchical linear model, we estimated improvement in navigation performance across trials by a decline in route length, shortening of search time, and reduction in fractal dimensionality of the path. While replicating commonly reported age and sex differences in time and distance indices, a reduction in fractal dimension of the path accounted for improvement across trials, independent of age or sex. The volumes of brain regions associated with the establishment of cognitive maps (parahippocampal gyrus and hippocampus) were related to path dimensionality, but not to the total distance and time. Thus, fractal dimensionality of a navigational path may present a useful complementary method of quantifying performance in navigation. PMID:24860019

Daugherty, Ana M; Yuan, Peng; Dahle, Cheryl L; Bender, Andrew R; Yang, Yiqin; Raz, Naftali

2014-05-23

442

Landscape and Flux Framework for Non-Equilibrium Networks: Kinetic Paths and Rate Dynamics  

NASA Astrophysics Data System (ADS)

We developed a general framework to quantify three key ingredients for dynamics of nonequilibrium systems through path integrals in length space. First, we identify dominant kinetic paths as the ones with optimal weights, leading to effective reduction of dimensionality or degrees of freedom from exponential to polynomial so large systems can be treated. Second, we uncover the underlying nonequilibrium potential landscapes from the explorations of the state space through kinetic paths. We apply our framework to a specific example of nonequilibrium network system: lambda phage genetic switch. Two distinct basins of attractions emerge. The dominant kinetic paths from one basin to another are irreversible and do not follow the usual steepest descent or gradient path along the landscape. It reflects the fact that the dynamics of nonequilibrium systems is not just determined by potential gradient but also the residual curl flux force, suggesting experiments to test theoretical predictions. Third, we have calculated dynamic transition time scales from one basin to another critical for stability of the system through instantons. Theoretical predictions are in good agreements with wild type and mutant experiments.We further uncover the correlations between the kinetic transition time scales and the underlying landscape topography: the barrier heights along the dominant paths. We found that both the dominant paths and the landscape are relatively robust against the influences of external environmental perturbations and the system tends to dissipate less with less fluctuations. Our theoretical framework is general and can be applied to other nonequilibrium systems.

Wang, Jin

2012-02-01

443

ZINC ABSORPTION BY INFANTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Zinc is a vital mineral in human nutrition, and rare cases of overt zinc deficiency are well described in term and preterm infants. A variety of methods have been developed to assess zinc absorption, retention, and balance in humans, either using mass (metabolic) balance or stable isotope-based METH...

444

ZINC ABSORPTION BY INFANTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Zinc is a vital mineral in human nutrition and rare cases of overt zinc deficiency are well described in term and preterm infants. A variety of methods have been developed to assess zinc absorption, retention and balance in humans, either using mass (metabolic) balance or stable isotope-based METHOD...

445

Two-Phonon Absorption  

ERIC Educational Resources Information Center

A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

Hamilton, M. W.

2007-01-01

446

Energy absorption buildup factors for thermoluminescent dosimetric materials and their tissue equivalence  

Microsoft Academic Search

Gamma ray energy-absorption buildup factors were computed using the five-parameter geometric progression (G-P) fitting formula for seven thermoluminescent dosimetric (TLD) materials in the energy range 0.015-15 MeV, and for penetration depths up to 40 mfp (mean free path). The generated energy-absorption buildup factor data have been studied as a function of penetration depth and incident photon energy. Buildup factors determined

S. R. Manohara; S. M. Hanagodimath; L. Gerward

2010-01-01

447

Energy absorption buildup factors for thermoluminescent dosimetric materials and their tissue equivalence  

Microsoft Academic Search

Gamma ray energy-absorption buildup factors were computed using the five-parameter geometric progression (G-P) fitting formula for seven thermoluminescent dosimetric (TLD) materials in the energy range 0.015–15MeV, and for penetration depths up to 40mfp (mean free path). The generated energy-absorption buildup factor data have been studied as a function of penetration depth and incident photon energy. Buildup factors determined in the

S. R. Manohara; S. M. Hanagodimath; L. Gerward

2010-01-01

448

Pharmacologically induced erect penile length and stretched penile length are both good predictors of post-inflatable prosthesis penile length.  

PubMed

Inflatable penile prosthesis (IPP) remains the gold standard for the surgical treatment of refractory erectile dysfunction; however, current literature to aid surgeons on how best to counsel patients on their postoperative inflated penile length is lacking. The aim of this study was to identify preoperative parameters that could better predict postoperative penile length following insertion of an IPP. Twenty men were enrolled in a prospective study examining penile lengths before and after IPP surgery. Patients with Peyronie's disease were excluded from this analysis. Baseline preoperative characteristics, including body mass index, history of hypertension, diabetes, Sexual Health Inventory for Men scores and/or prior radical prostatectomy were recorded. All patients underwent implantation with a three-piece inflatable Coloplast penile prosthesis. We compared stretched penile length to pharmacologically induced erect lengths. Postoperatively, we measured inflated penile lengths at 6 weeks and assessed patients' perception of penile size at 12 weeks. The median (±interquartile range) stretched penile length and pharmacologically induced erect penile length was 15 (±3) and 14.25 (±2)?cm, respectively (P=0.5). Median post-prosthesis penile length (13.5±2.13?cm) was smaller than preoperative pharmacologically induced length (P=0.02) and preoperative stretched penile length (P=0.01). The majority of patients (70%) had a decrease in penile length (median loss 0.5±1.5?cm); however, this loss was perceptible by 43% of men. Stretched penile length and pharmacologically induced erect penile length were equally good predictors of postoperative inflated length (Spearman's correlation 0.8 and 0.9, respectively). Pharmacologically induced erect penile length and stretched penile lengths are equal predictors of post-prosthesis penile length. The majority of men will experience some decrease in penile length following prosthesis implantation; however <50% report a subjective loss of penile length. PMID:24430278

Osterberg, E C; Maganty, A; Ramasamy, R; Eid, J F

2014-01-01

449

INTERSTELLAR METASTABLE HELIUM ABSORPTION AS A PROBE OF THE COSMIC-RAY IONIZATION RATE  

SciTech Connect

The ionization rate of interstellar material by cosmic rays has been a major source of controversy, with different estimates varying by three orders of magnitude. Observational constraints of this rate have all depended on analyzing the chemistry of various molecules that are produced following cosmic-ray ionization, and in many cases these analyses contain significant uncertainties. Even in the simplest case (H{sup +} {sub 3}), the derived ionization rate depends on an (uncertain) estimate of the absorption path length. In this paper, we examine the feasibility of inferring the cosmic-ray ionization rate using the 10830 A absorption line of metastable helium. Observations through the diffuse clouds toward HD 183143 are presented, but yield only an upper limit on the metastable helium column density. A thorough investigation of He{sup +} chemistry reveals that only a small fraction of He{sup +} will recombine into the triplet state and populate the metastable level. In addition, excitation to the triplet manifold of helium by secondary electrons must be accounted for as it is the dominant mechanism which produces He* in some environments. Incorporating these various formation and destruction pathways, we derive new equations for the steady state abundance of metastable helium. Using these equations in concert with our observations, we find zeta{sub He} < 1.2 x 10{sup -15} s{sup -1}, an upper limit about 5 times larger than the ionization rate previously inferred for this sight line using H{sup +} {sub 3}. While observations of interstellar He* are extremely difficult at present, and the background chemistry is not nearly as simple as previously thought, potential future observations of metastable helium would provide an independent check on the cosmic-ray ionization rate derived from H{sup +} {sub 3} in diffuse molecular clouds, and, perhaps more importantly, allow the first direct measurements of the ionization rate in diffuse atomic clouds.

Indriolo, Nick; McCall, Benjamin J. [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Hobbs, L. M. [University of Chicago, Yerkes Observatory, Williams Bay, WI 53191 (United States); Hinkle, K. H. [National Optical Astronomy Observatories, Tucson, AZ 85726 (United States)

2009-10-01

450

A model of anomalous absorption, backscatter, and flux limitation in laser-produced plasmas  

Microsoft Academic Search

Fluid simulations of laser light absorption and backscatter for planar targets are presented for various laser irradiances, wavelengths, target materials, laser pulse lengths, and simulated prepulse conditions. Physical processes included in the model are inverse bremsstrahlung, resonant absorption, absorption by ion-acoustic fluctuations, and Brillouin backscatter. For the anomalous processes, self-consistent transport coefficients are derived and used throughout the time-dependent, one-dimensional

D. G. Colombant; Wallace M. Manheimer

1980-01-01

451

A theory of anomalous absorption, backscatter and flux limitation in laser produced plasmas  

Microsoft Academic Search

Fluid simulations of laser light absorption and backscatter are presented for various laser irradiances, wavelengths, target materials, laser pulse lengths and simulated prepulse conditions. Physical processes included in the model are inverse bremsstrahlung, resonant absorption, absorption by ion-acoustic fluctuations, and Brillouin backscatter. For the anomalous processes, self-consistent transport coefficients are derived and used throughout the time-dependent, one-dimensional code. Flux limitation

D. G. Colombant; W. M. Manheimer

1979-01-01

452

Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers.  

PubMed

Resonant plasmonic and metamaterial structures allow for control of fundamental optical processes such as absorption, emission and refraction at the nanoscale. Considerable recent research has focused on energy absorption processes, and plasmonic nanostructures have been shown to enhance the performance of photovoltaic and thermophotovoltaic cells. Although reducing metallic losses is a widely sought goal in nanophotonics, the design of nanostructured 'black' super absorbers from materials comprising only lossless dielectric materials and highly reflective noble metals represents a new research direction. Here we demonstrate an ultrathin (260 nm) plasmonic super absorber consisting of a metal-insulator-metal stack with a nanostructured top silver film composed of crossed trapezoidal arrays. Our super absorber yields broadband and polarization-independent resonant light absorption over the entire visible spectrum (400-700 nm) with an average measured absorption of 0.71 and simulated absorption of 0.85. Proposed nanostructured absorbers open a path to realize ultrathin black metamaterials based on resonant absorption. PMID:22044996

Aydin, Koray; Ferry, Vivian E; Briggs, Ryan M; Atwater, Harry A

2011-01-01

453

Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers  

NASA Astrophysics Data System (ADS)

Resonant plasmonic and metamaterial structures allow for control of fundamental optical processes such as absorption, emission and refraction at the nanoscale. Considerable recent research has focused on energy absorption processes, and plasmonic nanostructures have been shown to enhance the performance of photovoltaic and thermophotovoltaic cells. Although reducing metallic losses is a widely sought goal in nanophotonics, the design of nanostructured 'black' super absorbers from materials comprising only lossless dielectric materials and highly reflective noble metals represents a new research direction. Here we demonstrate an ultrathin (260 nm) plasmonic super absorber consisting of a metal-insulator-metal stack with a nanostructured top silver film composed of crossed trapezoidal arrays. Our super absorber yields broadband and polarization-independent resonant light absorption over the entire visible spectrum (400-700 nm) with an average measured absorption of 0.71 and simulated absorption of 0.85. Proposed nanostructured absorbers open a path to realize ultrathin black metamaterials based on resonant absorption.

Aydin, Koray; Ferry, Vivian E.; Briggs, Ryan M.; Atwater, Harry A.

2011-11-01

454

Characterizing the evolutionary path(s) to early Homo.  

PubMed

Numerous studies suggest that the transition from Australopithecus to Homo was characterized by evolutionary innovation, resulting in the emergence and coexistence of a diversity of forms. However, the evolutionary processes necessary to drive such a transition have not been examined. Here, we apply statistical tests developed from quantitative evolutionary theory to assess whether morphological differences among late australopith and early Homo species in Africa have been shaped by natural selection. Where selection is demonstrated, we identify aspects of morphology that were most likely under selective pressure, and determine the nature (type, rate) of that selection. Results demonstrate that selection must be invoked to explain an Au. africanus-Au. sediba-Homo transition, while transitions from late australopiths to various early Homo species that exclude Au. sediba can be achieved through drift alone. Rate tests indicate that selection is largely directional, acting to rapidly differentiate these taxa. Reconstructions of patterns of directional selection needed to drive the Au. africanus-Au. sediba-Homo transition suggest that selection would have affected all regions of the skull. These results may indicate that an evolutionary path to Homo without Au. sediba is the simpler path and/or provide evidence that this pathway involved more reliance on cultural adaptations to cope with environmental change. PMID:25470780

Schroeder, Lauren; Roseman, Charles C; Cheverud, James M; Ackermann, Rebecca R

2014-01-01

455

Dynamic optical properties in graphene: Length versus velocity gauge  

SciTech Connect

The dynamic optical properties of graphene are theoretically investigated in both length gauge and velocity gauge in the presence of ultrafast optical radiation field. The two gauges present different results of dynamic photo-induced carriers and optical conductance due to distinct dependencies on electric field and non-resonant optical absorption, while the two gauges give identical results in the steady state time. It shows that the choice of gauge affects evidently the dynamic optical properties of graphene. The velocity gauge represents an outcome of a real physical experiment.

Dong, H. M.; Han, K., E-mail: han6409@263.net [Department of Physics, China University of Mining and Technology, Xuzhou 221116 (China); Xu, W. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Department of Physics, Yunnan University, Kunming 650091 (China)

2014-02-14

456

Multiple order common path spectrometer  

NASA Technical Reports Server (NTRS)

The present invention relates to a dispersive spectrometer. The spectrometer allows detection of multiple orders of light on a single focal plane array by splitting the orders spatially using a dichroic assembly. A conventional dispersion mechanism such as a defraction grating disperses the light spectrally. As a result, multiple wavelength orders can be imaged on a single focal plane array of limited spectral extent, doubling (or more) the number of spectral channels as compared to a conventional spectrometer. In addition, this is achieved in a common path device.

Newbury, Amy B. (Inventor)

2010-01-01

457

Intellimotion: California PATH's Quarterly Newsletter  

NSDL National Science Digital Library

The California Partners for Advanced Transit and Highways (PATH) researches methods for increasing highway safety, reducing congestion, and minimizing pollution and energy consumption. Intellimotion is one of its publications that highlights some of the current projects. Although it is labeled as a quarterly newsletter, Intellimotion is released on a very irregular basis. The 2002 issue covers several stories, including a project that makes vehicle navigation with the Global Positioning System extremely accurate. Another article looks at intelligent transportation systems and the issues regarding Bus Rapid Transit. Many past issues of Intellimotion are available on this Web site. This site is also reviewed in the October 25, 2002 Scout Report.

458

Communication path for extreme environments  

NASA Technical Reports Server (NTRS)

Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.

Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)

2010-01-01

459

Staff detection with stable paths.  

PubMed

The preservation of musical works produced in the past requires their digitalization and transformation into a machine-readable format. The processing of handwritten musical scores by computers remains far from ideal. One of the fundamental stages to carry out this task is the staff line detection. We investigate a general-purpose, knowledge-free method for the automatic detection of music staff lines based on a stable path approach. Lines affected by curvature, discontinuities, and inclination are robustly detected. Experimental results show that the proposed technique consistently outperforms well-established algorithms. PMID:19372615

Dos Santos Cardoso, Jaime; Capela, Artur; Rebelo, Ana; Guedes, Carlos; Pinto da Costa, Joaquim

2009-06-01

460

Test Compression for Robust Testable Path Delay Fault Testing Using Interleaving and Statistical Coding  

NASA Astrophysics Data System (ADS)

This paper proposes a method providing efficient test compression. The proposed method is for robust testable path delay fault testing with scan design facilitating two-pattern testing. In the proposed method, test data are interleaved before test compression using statistical coding. This paper also presents test architecture for two-pattern testing using the proposed method. The proposed method is experimentally evaluated from several viewpoints such as compression rates, test application time and area overhead. For robust testable path delay fault testing on 11 out of 20 ISCAS89 benchmark circuits, the proposed method provides better compression rates than the existing methods such as Huffman coding, run-length coding, Golomb coding, frequency-directed run-length (FDR) coding and variable-length input Huffman coding (VIHC).

Namba, Kazuteru; Ito, Hideo

461

Effects of silicon nanowires length on solar cells photovoltaic properties  

NASA Astrophysics Data System (ADS)

Silicon nanowires (SiNWs) were produced by an electroless method on FZ-Si (100) wafer, in HF/AgNO3 solution. The influence of etching time and temperature on SiNWs morphology were studied using FESEM images. Optical properties were also investigated by optical absorption spectroscopy and low-temperature photoluminescence at 4.2 K. Considering their role as active regions, photovoltaic properties of SiNWs solar cells were studied for their different lengths. Photovoltaic measurements were taken in 1 sun condition under AM 1.5 illumination supplied by a solar simulator. Measurements indicated a reduction in efficiency as SiNWs length increased, which might be attributed to increased dangling states on nanowires surfaces.

Farangi, M.; Zahedifar, M.; Mozdianfard, M. R.; Pakzamir, M. H.

2012-11-01

462

Differential absorption and scattering sensitivity predictions  

NASA Technical Reports Server (NTRS)

A set of general equations for evaluating the sensitivity of the Differential Absorption and Scattering (DAS) technique based upon a conventional analysis of statistical errors is derived. The equations are put in a proper form for evaluating total column density and range resolved concentration measurements of a variety of atmospheric species. The derived equation are subsequently used to analyze the sensitivity of DAS in three specific applications assuming realistic parameters for the optical and electronic components of proposed DAS systems. The three DAS applications evaluated are: (1) measurement of nitrogen at ground levels over a horizontal path; (2) measurement of atmospheric ozone depletion in the wake of a jet engine at 20 km altitude; and (3) measurements of the ozone distribution in the atmosphere from an orbiting space