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1

Light absorption cell combining variable path and length pump  

DOEpatents

A device is described 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 there between 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. 2 figures.

Prather, W.S.

1993-12-07

2

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

3

Effective optical path length for tandem diffuse cubic cavities as gas absorption cell  

NASA Astrophysics Data System (ADS)

Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap < 0.01, which coincided well with theoretical analysis. The simulating EOPL was smaller than experimental results at fap > 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.

Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.

2014-12-01

4

Measuring absorption coefficients in small volumes of highly scattering media: source-detector separations for which path lengths do not depend on scattering properties  

SciTech Connect

The noninvasive measurement of variations in absorption that are due to changes in concentrations of biochemically relevant compounds in tissue is important in many clinical settings. One problem with such measurements is that the path length traveled by the collected light through the tissue depends on the scattering properties of the tissue. We demonstrate, using both Monte Carlo simulations and experimental measurements, that for an appropriate separation between light-delivery and light-collection fibers the path length of the collected photons does not depend on scattering parameters for the range of parameters typically found in tissue. This is important for developing rapid, noninvasive, and inexpensive methods for measuring absorption changes in tissue. {copyright} 1997 Optical Society of America

Mourant, J.R.; Bigio, I.J.; Jack, D.A.; Johnson, T.M.; Miller, H.D. [Bioscience and Biotechnology Group CST-4, MS E535, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1997-08-01

5

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

6

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

7

Three mirror optical path length corrector  

NASA Astrophysics Data System (ADS)

A system of three high-speed tilt mirrors with a coupled control system used for correcting absolute optical path length (OPL) variations in a beam train has been analyzed. The system uses the principle that three one-degree-of-freedom tilt mirrors can be used to simultaneously control three fundamental beam parameters: tilt (beam jitter), translation (beam walk), and OPL (piston error). Closed-form solutions to the three coupled equations have been found and will be presented. Two special cases have been studied in detail. The first case used the three mirror system to maintain the current state of tilt and translation while independently controlling the absolute OPL for phasing. The second case uses the three mirror system to correct or negate any tilt or translation while imparting an absolute OPL on the beam as well. The limitations of the small angle approximation have been examined as well as a practical concept for the control system. Applications to laser beam trains, phased arrays, or astronomical systems employing interferometric imaging techniques are discussed.

Tyson, Robert K.

8

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

9

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

10

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

2007-06-19

11

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2013 CFR

... FIXED MICROWAVE SERVICES Technical Standards § 101.143 ...path length in kilometers. Note to paragraph (b ...(c) Upon an appropriate technical showing, applicants and...exception to these requirements. Note to paragraph (c ):...

2013-10-01

12

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2012 CFR

... FIXED MICROWAVE SERVICES Technical Standards § 101.143 ...path length in kilometers. Note to paragraph (b ...(c) Upon an appropriate technical showing, applicants and...exception to these requirements. Note to paragraph (c ):...

2012-10-01

13

On the Optimal Path Length for Tor Kevin Bauer1  

E-print Network

On the Optimal Path Length for Tor Kevin Bauer1 , Joshua Juen2 , Nikita Borisov2 , Dirk Grunwald1 that optimally balances security and performance is an open problem. Tor's design decision to build paths frequently involve achieving a correct balance between security and performance. For example, Tor does

Borisov, Nikita

14

Analytical solution of average path length for Apollonian networks  

NASA Astrophysics Data System (ADS)

With the help of recursion relations derived from the self-similar structure, we obtain the solution of average path length, dmacr t , for Apollonian networks. In contrast to the well-known numerical result dmacr t?(lnNt)3/4 [J. S. Andrade, Jr. , Phys. Rev. Lett. 94, 018702 (2005)], our rigorous solution shows that the average path length grows logarithmically as dmacr t?lnNt in the infinite limit of network size Nt . The extensive numerical calculations completely agree with our closed-form solution.

Zhang, Zhongzhi; Chen, Lichao; Zhou, Shuigeng; Fang, Lujun; Guan, Jihong; Zou, Tao

2008-01-01

15

Average Photon Path-Length in Isotropically Scattering Finite Atmospheres  

NASA Astrophysics Data System (ADS)

The determination of the average path-length of photons in a finite isotropically scattering plane-parallel homogeneous atmosphere is discussed. To solve this problem we have used the kernel approximation method which easily allows us to find the derivatives of the intensity with respect to optical depth, optical thickness and albedo of single scattering. In order to check the results we have used another approach by exploiting the set of integrodifferential equations of Chandrasekhar for theX- andY-functions. This approach allows us to find the average path length only at the boundaries of the atmosphere but on the other hand it gives also the dispersion of the path-length distribution function, thus generating the input parameters for determining the approximate path-length distribution function. It occurred that the set so obtained is stable and the results are highly accurate. As a by-product we obtain the first two derivatives of theX- andY-functions with respect to the albedo of single scattering and optical thickness, and the mixed derivative.

Viik, Tõnu

1995-03-01

16

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

17

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

18

Photon path length distributions for cloudy skies  oxygen A-Band measurements and model calculations  

NASA Astrophysics Data System (ADS)

This paper addresses the statistics underlying cloudy sky radiative transfer (RT) by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999). Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD). This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate) RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements.

Funk, O.; Pfeilsticker, K.

2003-03-01

19

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

20

Path-length control in an interferometric QKD link  

NASA Astrophysics Data System (ADS)

We describe a phase-encoded quantum key distribution system the uses continuous control of receiver-interferometer path length to maintain alignment with the transmitter. In this fiber-based system, a small number of training frames are sent over the quantum channel that allow the receiver to compensate for drift in the transmitter and receiver interferometers due to slow changes in temperature. The system is self-starting after disruption and can maintain a quantum bit error rate of less than 7% for phase drift rates of 0.5 deg/sec. The control system design is described and measured system data is compared with simulations.

Elliott, Brig B.; Pikalo, Oleksiy; Schlafer, John; Troxel, Greg

2003-08-01

21

Infrared Pulse-laser Long-path Absorption Measurement of Carbon Dioxide Using a Raman-shifted Dye Laser  

NASA Technical Reports Server (NTRS)

A pulsed laser source is effective in infrared laser long-path absorption measurements when the optical path length is very long or the reflection from a hard target is utilized, because higher signal-to-noise ratio is obtained in the detection of weak return signals. We have investigated the performance of a pulse-laser long-path absorption system using a hydrogen Raman shifter and a tunable dye laser pumped by a Nd:YAG laser, which generates second Stokes radiation in the 2-micron region.

Minato, Atsushi; Sugimoto, Nobuo; Sasano, Yasuhiro

1992-01-01

22

On the Relationship of Tornado Path Length and Width to Intensity  

Microsoft Academic Search

Reported path lengths and widths of tornadoes have been modeled using Weibull distributions for different Fujita (F) scale values. The fits are good over a wide range of lengths and widths. Path length and width tend to increase with increasing F scale, although the temporal nonstationarity of the data for some parts of the data (such as width of F3

Harold E. Brooks

2004-01-01

23

Two approaches for assessing photon path length distribution in pulp  

NASA Astrophysics Data System (ADS)

Pulp consists of distinguishable particles, the refractive indices of which differ from the index of the employed medium, water. We are thus dealing with an optically scattering material. Particle distribution in pulp is nowadays a focus of interest. This parameter is related to the photon path length distribution (PPLD) determined by the inhomogeneity of the scatterer. In order to assess PPLD, we use two methods. In the first, the particle properties in pulp are estimated by means of a microscope. A model for Monte Carlo simulation is then built to obtain PPLD. In the second, the signal generated by a laser pulse passing the cuvette filled with water or pulp is detected with a streak camera and the assessment of PPLD accomplished by a deconvolution procedure. To obtain the particle distribution, the two methods may be used together, so that the streak-camera measurements give PPLD, and in the following simulation process the particle distribution is found, which corresponds to the determined PPLD. The number and diversity of the sample sets currently used do not fdfill the statistical requirements of the industry. Nevertheless, the results achieved encourage us to develop the methods further.

Saarela, Juha; Tormanen, Matti; Karttunen, Kyösti; Myllylä, Risto

2005-08-01

24

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

25

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

26

Two dynamic reconfiguration approaches for optimizing the restoration path length in p-cycle protection network  

NASA Astrophysics Data System (ADS)

p-cycle is one of the most promising technique of span protection in optical transport networks with mesh-like efficiency and ring-like speed. Longer p-cycle provides better efficiency in term of spare capacity, but longer restored path increases end-to-end propagation delay, which reduces the reliability of the restored network. Hence, minimization of restoration path is a critical issue in p-cycle based protection network. In this paper, two new dynamic reconfiguration approaches namely inter-cycles switching (ICS) and local restoration paths (LRP) are discussed to reduce the length of restored paths in existing optimal spare capacity design of p-cycle. Both proposed approaches are meant to utilize the idle p-cycles thus significantly reducing the path length. This reduction in restored path length also releases the redundant spare capacity.

Yadav, Raghav; Yadav, Rama Shankar

2010-07-01

27

COMPARISON BETWEEN PATH LENGTHS TRAVELED BY SOLAR ELECTRONS AND IONS IN GROUND-LEVEL ENHANCEMENT EVENTS  

SciTech Connect

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 ({approx}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. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Malandraki, Olga E.; Patsou, Ioanna; Papaioannou, Athanasios [Institute of Astronomy and Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Athens (Greece); Reames, Donald V. [Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742 (United States); Ng, Chee K. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Wang, Linghua, E-mail: ltan@umd.edu [Department of Geophysics, Peking University, Beijing 100871 (China)

2013-05-01

28

Genetics of Path Lengths in Brain Connectivity Networks: HARDI-Based Maps in 457 Adults  

PubMed Central

Brain connectivity analyses are increasingly popular for investigating organization. Many connectivity measures including path lengths are generally defined as the number of nodes traversed to connect a node in a graph to the others. Despite its name, path length is purely topological, and does not take into account the physical length of the connections. The distance of the trajectory may also be highly relevant, but is typically overlooked in connectivity analyses. Here we combined genotyping, anatomical MRI and HARDI to understand how our genes influence the cortical connections, using whole-brain tractography. We defined a new measure, based on Dijkstra’s algorithm, to compute path lengths for tracts connecting pairs of cortical regions. We compiled these measures into matrices where elements represent the physical distance traveled along tracts. We then analyzed a large cohort of healthy twins and show that our path length measure is reliable, heritable, and influenced even in young adults by the Alzheimer’s risk gene, CLU.

Jahanshad, Neda; Prasad, Gautam; Toga, Arthur W.; McMahon, Katie L.; de Zubicaray, Greig I.; Martin, Nicholas G.; Wright, Margaret J.; Thompson, Paul M.

2014-01-01

29

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 Minimum path lengths for fixed links. (a) The distance between end points of a fixed link must equal or exceed the...

2010-10-01

30

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2012 CFR

...CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 ...path length in kilometers. Note to paragraph (b ...(c) Upon an appropriate technical showing, applicants and...exception to these requirements. Note: Links authorized...

2012-10-01

31

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2011 CFR

...CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 ...path length in kilometers. Note to paragraph (b ...(c) Upon an appropriate technical showing, applicants and...exception to these requirements. Note: Links authorized...

2011-10-01

32

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2013 CFR

...CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 ...path length in kilometers. Note to paragraph (b ...(c) Upon an appropriate technical showing, applicants and...exception to these requirements. Note: Links authorized...

2013-10-01

33

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2014 CFR

...CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 ...path length in kilometers. Note to paragraph (b ...(c) Upon an appropriate technical showing, applicants and...exception to these requirements. Note: Links authorized...

2014-10-01

34

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

35

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

PubMed

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

36

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

37

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

38

On the determination of atmospheric path length by passive microwave radiometer  

NASA Technical Reports Server (NTRS)

Microwave radiometer techniques were evaluated for use in atmospheric path length correction of Pacific Plate Motion Experiment interferometer measurements. It is shown that passive microwave radiometry allows precise measurement of the brightness temperature of the sky. It is also noted that the technological requirements of radiometers are very different from the requirements of radio astronomy. The technology was used in the construction of radiometers which are sufficient for use in the path length correction problem. A simulation study shows that, when combined with surface meteorology data, passive microwave radiometer data would allow a determination of the path length correction to better than 2 cm at the zenith. By a careful choice of frequencies, a dual frequency system would allow a measurement of the path length correction to better than 4 cm at zenith angles as great as 60 deg. Because of the wide range of weather conditions to be expected for the PPME sites (which include Alaska, Hawaii and Massachusetts), it will probably be necessary to use a separate correction algorithm for each site.

Webster, W. J., Jr.

1975-01-01

39

Measurement of Optical Path Length for Cerebral Near-Infrared Spectroscopy in Newborn Infants  

Microsoft Academic Search

The time taken for an extremely short pulse of near-infrared laser light to traverse the heads of 6 preterm infants was measured after death. The values obtained were used to calculate a differential path length factor (DPF), defined as the mean distance travelled by the photons divided by the distance between the points where light entered and left the head.

J. S. Wyatt; M. Cope; D. T. Delpy; P. van der Zee; S. R. Arridge; A. D. Edwards; E. O. R. Reynolds

1990-01-01

40

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

41

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

E-print Network

such as the free-electron laser by making them more compact and with shorter pulse duration, and could provide, France (Received 9 June 2006; published 25 August 2006) Electron bunch lengthening due to space of the electron bunch, a larger initial radius causes path-length differences in both the rf cavity

Boyer, Edmond

42

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

43

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

44

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

45

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

2014-12-01

46

Journal of Power Sources xxx (2006) xxxxxx The impact of channel path length on PEMFC flow-field design  

E-print Network

cm2 serpentine laboratory- scale flow-field patterns with different flow path lengths and inlet is one method of minimizing these stresses. This paper investigates how 200 cm2 serpentine flow become more uniform for serpentine flow-field designs with shorter path lengths or larger number

Van Zee, John W.

47

Terahertz path-length lens composed of oblique metal slit array  

NASA Astrophysics Data System (ADS)

Need for high-performance and sophisticated optical devices in the terahertz wave band is growing rapidly with terahertz technological progress. This paper presents a lens in the terahertz wave band based on phase control using an oblique metal slit array. A convex oblique slit array can produce a focusing effect. This focusing effect is confirmed by full-wave analysis for the designed terahertz path-length lens. The effective refractive index computed from the full-wave analysis is consistent with analytical expressions and changes from 1.00 to 1.56 with the angle of the metal slit array. Full-wave analysis also confirms that the lamination errors of the path-length lens have limited influence on the focusing effects. The robustness of the lens design is essential for its industrial applications to terahertz optical devices.

Togashi, Takahisa; Kitahara, Hideaki; Takano, Keisuke; Hangyo, Masanori; Mita, Mamoru; Young, John C.; Suzuki, Takehito

2015-02-01

48

Volcanic Segmentation, Nb Depletion, Reactive Flow Path Length and Volcano Size are Linked in Central America  

NASA Astrophysics Data System (ADS)

Central America is unusual among the global set of arcs because the volcanic front is segmented by abrupt right steps of up to 40 km. Nb depletion (Zr/Nb) jumps at these steps (Bolge, 2005). Nb depletion is greater (Zr/Nb higher) at the volcano closer to the trench. Between steps, Nb depletion decreases to the SE, creating a saw- tooth pattern. Given the smooth Benioff zone revealed by seismicity and the slight anticlockwise rotation of the linear volcanic segments relative to the isobaths to the seismic zone, the variation in Nb depletion correlates with depth to the seismic zone. Thus, short paths have maximum Nb depletion and long paths have minimum depletion. This suggests a melt/fluid generation with a Nb retaining phase in the residue to create the initial depletion. A reactive flow through the mantle wedge then progressively reduces the initial depletion. The full set of incompatible elements is consistent with simple AFC models of this process. Furthermore, the uneven distribution of volcanic output along the volcanic front appears related to the variation in path length. A short path generates maximum Nb depletion and a small volcano. An intermediate length path generates a large volcano and moderate Nb depletion. A long path generates minimum Nb depletion and, again, a small volcano. This suggests that the magma generating region has an optimal depth or distance from the trench for magma productivity. Finally, although the origin of the volcanic lines is not explained, it must be a facet of upper plate tectonics, rather than a segmented slab.

Carr, M. J.; Bolge, L. L.

2007-12-01

49

Fiber-optic liquid level sensor based on coupling optical path length variation  

NASA Astrophysics Data System (ADS)

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm.

Nath, Pabitra; Kumarjit Singh, Hidam; Tiwari, Dhananjay; Basumatry, Tenisen

2012-05-01

50

Fiber-optic liquid level sensor based on coupling optical path length variation.  

PubMed

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm. PMID:22667647

Nath, Pabitra; Singh, Hidam Kumarjit; Tiwari, Dhananjay; Basumatry, Tenisen

2012-05-01

51

Path-length dependence of energy loss within in-medium showers  

SciTech Connect

The study of the path-length dependence of high-transverse-momentum (P{sub T}) hadron suppression in heavy-ion collisions by measuring the dependence of hard-hadron production on the angle {phi} with the reaction plane in noncentral collisions has so far been one of the most successful tools in constraining the microscopic picture of leading-parton energy loss. With the imminent start of the Large Hadron Collider heavy-ion program and the possibility of full jet reconstruction, the focus has shifted to models that are capable of simulating full in-medium parton showers rather than tracing the leading parton only. Yet, on the level of single-inclusive hadron observables, such shower models need to reproduce the findings of leading-parton energy-loss models; in particular, they need to reproduce the correct reaction-plane-angle dependence of hadron suppression. The aim of this work is to illustrate, using the example of the Monte Carlo in-medium shower code, yajem (Yet another Jet Energy-loss Model), how path-length dependence arises in a Monte Carlo shower formulation, how it relates to path-length dependence of leading-parton energy loss, and how model results compare with data on the reaction-plane dependence of the nuclear suppression factor R{sub AA}({phi}).

Renk, Thorsten [Department of Physics, P.O. Box 35, FI-40014 University of Jyvaeskylae, Finland and (Finland); Helsinki Institute of Physics, P.O. Box 64, FI-00014 University of Helsinki (Finland)

2011-02-15

52

Path-length-multiplexed scattering-angle-diverse optical coherence tomography for retinal imaging  

PubMed Central

A low-resolution path-length-multiplexed scattering angle diverse optical coherence tomography (PM-SAD-OCT) is constructed to investigate the scattering properties of the retinal nerve fiber layer (RNFL). Low-resolution PM-SADOCT retinal images acquired from a healthy human subject show the variation of RNFL scattering properties at retinal locations around the optic nerve head. The results are consistent with known retinal ganglion cell neural anatomy and principles of light scattering. Application of PM-SAD-OCT may provide potentially valuable diagnostic information for clinical retinal imaging. PMID:24177097

Wang, Bingqing; Yin, Biwei; Dwelle, Jordan; Rylander, H. Grady; Markey, Mia K.; Milner, Thomas E.

2014-01-01

53

Long-path supercontinuum absorption spectroscopy for measurement of atmospheric constituents.  

PubMed

A supercontinuum source has been proposed as a new tool for measurement of minor species concentrations on long paths through the atmosphere. The present work describes results from recent experiments that demonstrate the potential for Differential Absorption Spectroscopy (DAS) and Spectral Pattern Recognition Differential Absorption Lidar (SPR-DIAL) measurements utilizing a supercontinuum source. As an initial example of this measurement approach, the results include the quantification of water vapor concentration through indoor and outdoor path absorption measurements using a collimated supercontinuum source. Experimental spectra are compared with equivalent simulations from MODTRAN??? versions 4 and 5 to examine the water vapor band between 1300 and 1500 nm to demonstrate the feasibility of the approach. PMID:18545560

Brown, David M; Shi, Kebin; Liu, Zhiwen; Philbrick, C R

2008-06-01

54

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

55

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

56

Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb  

NASA Astrophysics Data System (ADS)

Dynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known. The DP is the mean path length in tissues of backscattered photons and varies with wavelength. It is usually estimated using Monte Carlo simulations in simplified semi-infinite homogeneous geometries. Here we consider the use of multilayered models of the somatosensory cortex (SsC) and olfactory bulb (OB), which are common physiological models of brain activation. Simulations demonstrate that specific DP estimation is required for SsC and OB, specifically for wavelengths above 600 nm. They validate the hypothesis of a constant path length during activation and show the need for specific DP if imaging is performed in a thinned-skull preparation. The first multispectral reflectance imaging data recorded in vivo during OB activation are presented, and the influence of DP on the hemodynamic parameters and the pattern of oxymetric changes in the activated OB are discussed.

Renaud, Rémi; Martin, Claire; Gurden, Hirac; Pain, Frédéric

2012-01-01

57

Optimizing the multiphoton absorption properties of maximally path-entangled number states  

SciTech Connect

In this paper we examine the N-photon absorption properties of maximally path-entangled number states (N00N states). We consider two cases. The first involves the N-photon absorption properties of the ideal N00N state, one that does not include spectral information. We study how the N-photon absorption probability of this state scales with N, confirming results presented by others in a previous paper by a different method. We compare this to the absorption probability of various other states. The second case is that of two-photon absorption for an N=2 N00N state generated from a type-II spontaneous down-conversion event. In this situation we find that the absorption probability is both better than analogous coherent light (due to frequency entanglement) and highly dependent on the optical setup. We show that the poor production rates of quantum states of light may be partially mitigated by adjusting the spectral parameters to improve their two-photon absorption rates. This work has application to quantum imaging, particularly quantum lithography, where the N-photon absorbing process in the lithographic resist must be optimized for practical applications.

Plick, William N.; Wildfeuer, Christoph F.; Anisimov, Petr M.; Dowling, Jonathan P. [Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2009-12-15

58

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

59

Variable-length cell for studies of gas spectra with extremely short optical paths.  

PubMed

We present a cell for studies of light transmission through very strongly absorbing gases. It uses a fixed window and a mirror, parallel to the latter and attached to a micrometric linear motion feedthrough monitoring mirror-window distances from 0 to a couple of centimeters. This device is tested by recording CO2 gas spectra near 4.3 ?m using a Fourier transform spectrometer. Their analysis shows that optical-path lengths between 20 and 2000 ?m have been obtained. This now enables spectroscopic measurements of self-broadening coefficients of O16C12O16 lines in the ?3 band, for instance, and opens perspectives for optical soundings of thin films of porous materials. PMID:25089968

Morales, Sébastien B; Pangui, Edouard; Landsheere, Xavier; Tran, Ha; Hartmann, Jean-Michel

2014-07-01

60

arXiv:physics/0511072v2[physics.optics]14Apr2006 Optical fibers with interferometric path length stability by controlled heating for  

E-print Network

(at a velocity of 1 cm per year) will have to be controlled. Moreover, fiber length fluctuations havearXiv:physics/0511072v2[physics.optics]14Apr2006 Optical fibers with interferometric path length path length of an optical fiber to an accuracy of about 1/100 of the laser wavelength. We study

Peters, Achim

61

Investigating brain community structure abnormalities in bipolar disorder using PLACE (Path Length Associated Community Estimation)  

PubMed Central

In this paper, we present PLACE, a comprehensive framework for studying node-level community structure. Instead of the well-known Q modularity metric, PLACE utilizes a novel metric, ?PL, which measures the difference between inter-community versus intra-community path lengths. We compared community structures in human healthy brain networks generated using these two metrics, and argued that ?PL may have theoretical advantages. PLACE consists of the following: 1) extracting community structure using top-down hierarchical binary trees, where a branch at each bifurcation denotes a collection of nodes that form a community at that level, 2) constructing and assessing mean group community structure, and 3) detecting node-level changes in community between groups. We applied PLACE and investigated the structural brain networks obtained from a sample of 25 euthymic bipolar I subjects versus 25 gender and age matched healthy controls. Results showed community structural differences in posterior default mode network (DMN) regions, with the bipolar group exhibiting left-right decoupling. PMID:23798337

GadElkarim, Johnson J.; Ajilore, Olusola; Schonfeld, Dan; Zhan, Liang; Thomspon, Paul M.; Feusner, Jamie D.; Kumar, Anand; Altshuler, Lori L.; Leow, Alex D.

2014-01-01

62

Water equivalent path length measurement in proton radiotherapy using time resolved diode dosimetry  

SciTech Connect

Purpose: To verify water equivalent path length (WEPL) before treatment in proton radiotherapy using time resolved in vivo diode dosimetry. Methods: Using a passively scattered range modulated proton beam, the output of a diode driving a fast current-to-voltage amplifier is recorded at a number of depths in a water tank. At each depth, a burst of overlapping single proton pulses is observed. The rms duration of the burst is computed and the resulting data set is fitted with a cubic polynomial. Results: When the diode is subsequently set to an arbitrary depth and the polynomial is used as a calibration curve, the ''unknown'' depth is determined within 0.3 mm rms. Conclusions: A diode or a diode array, placed (for instance) in the rectum in conjunction with a rectal balloon, can potentially determine the WEPL at that point, just prior to treatment, with submillimeter accuracy, allowing the beam energy to be adjusted. The associated unwanted dose is about 0.2% of a typical single fraction treatment dose.

Gottschalk, B.; Tang, S.; Bentefour, E. H.; Cascio, E. W.; Prieels, D.; Lu, H.-M. [Laboratory for Particle Physics and Cosmology, Harvard University, 18 Hammond Street, Cambridge, Massachusetts 02138 (United States); Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114 (United States); Ion Beam Applications S.A., Louvain-la-Neuve 1348 (Belgium); Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114 (United States); Ion Beam Applications S.A., Louvain-la-Neuve 1348 (Belgium); Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114 (United States)

2011-04-15

63

Error reduction methods for integrated-path differential-absorption lidar measurements.  

PubMed

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". PMID:22772254

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

2012-07-01

64

Quadrupole Nitrogen Molecule Lines at 4.1 Micron Studies with a Diode Laser and AN Absorption Path of 5.016 KM  

NASA Astrophysics Data System (ADS)

Three quadrupole vibration-rotation absorption lines of molecular nitrogen were detected using second derivative spectroscopy in the 4.1 micron region, using a high resolution diode laser spectrometer and a White -type multiple reflection absorption cell, adjusted to a path length of 5.016 km. Accurate line positions, pressure broadening parameters, integrated absorption coefficients, and quadrupole moment derivatives were determined for two of these transitions. The S(10) quadrupole line was scanned at three pressures in the range 730 to 837 Torr, while the S(12) line was studied at five pressures, ranging from 729 to 950 Torr, to determine pressure-broadened line widths. All the measurements were carried out at a temperature of 297 ^circK. The line shapes and the full-width-at-half-maximum values provided some evidence of collisional narrowing.

Balog, Paul P.

1990-01-01

65

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

66

Addressing the Path-Length-Dependency Confound in White Matter Tract Segmentation  

PubMed Central

We derive the Iterative Confidence Enhancement of Tractography (ICE-T) framework to address the problem of path-length dependency (PLD), the streamline dispersivity confound inherent to probabilistic tractography methods. We show that PLD can arise as a non-linear effect, compounded by tissue complexity, and therefore cannot be handled using linear correction methods. ICE-T is an easy-to-implement framework that acts as a wrapper around most probabilistic streamline tractography methods, iteratively growing the tractography seed regions. Tract networks segmented with ICE-T can subsequently be delineated with a global threshold, even from a single-voxel seed. We investigated ICE-T performance using ex vivo pig-brain datasets where true positives were known via in vivo tracers, and applied the derived ICE-T parameters to a human in vivo dataset. We examined the parameter space of ICE-T: the number of streamlines emitted per voxel, and a threshold applied at each iteration. As few as 20 streamlines per seed-voxel, and a robust range of ICE-T thresholds, were shown to sufficiently segment the desired tract network. Outside this range, the tract network either approximated the complete white-matter compartment (too low threshold) or failed to propagate through complex regions (too high threshold). The parameters were shown to be generalizable across seed regions. With ICE-T, the degree of both near-seed flare due to false positives, and of distal false negatives, are decreased when compared with thresholded probabilistic tractography without ICE-T. Since ICE-T only addresses PLD, the degree of remaining false-positives and false-negatives will consequently be mainly attributable to the particular tractography method employed. Given the benefits offered by ICE-T, we would suggest that future studies consider this or a similar approach when using tractography to provide tract segmentations for tract based analysis, or for brain network analysis. PMID:24797510

Liptrot, Matthew G.; Sidaros, Karam; Dyrby, Tim B.

2014-01-01

67

Measurement of tropospheric OH by laser long-path absorption spectroscopy  

NASA Technical Reports Server (NTRS)

OH-radicals are measured by laser long-path absorption spectroscopy. A tunable Nd:YAG/dye laser system provides broadbanded light at 308 nm. The beam is expanded to 0.3 m and pointed to an array of retroreflectors placed at a distance of 2800 m. The returning beam is separated from the outgoing beam and focused into a spectrometer of 0.3 pm resolution. A 1024 element diode array is used as a detector. The signal is digitized by a 14 bit analog to digital converter. The ultimate aim is a detection limit of 10(exp 5) molecules cm(exp -3) of OH. However the measurements in 1991 allowed only the recognition of OH absorptions corresponding to 3 x 10(exp 6) OH cm(exp -3) with a signal to noise ratio of two. Improvements of the instrument are under way. The advantages of the DOAS method are: the accuracy of detection is guaranteed because loss of OH radicals within the device is avoided, the rate of OH production by the device is negligible, and absorptions of other trace gases could be corrected for; and the calibration procedure for the device is fast and easy. The disadvantages of the system are: time resolution is about minutes because about ten spectra had to be added to keep the noise level down, the OH concentration is averaged along the whole light path, weight (500 kg) and size (4x4 m) of the device; and approximately 10 l/min of coolant and supply of 8 kW electrical power are necessary.

Kraft, Michael; Perner, D.

1994-01-01

68

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)  

Microsoft Academic Search

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

Parshotam Sharma; Inderjit Singh Hudiara; Maninder Lal Singh

2011-01-01

69

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

70

Measurement of cranial optical path length as a function of age using phase resolved near infrared spectroscopy.  

PubMed

Near infrared spectroscopy (NIRS) has been used to measure concentration changes of cerebral hemoglobin and cytochrome in neonates, children, and adults, to study cerebral oxygenation and hemodynamics. To derive quantitative concentration changes from measurements of light attenuation, the optical path length must be known. This is obtained by multiplying the source/ detector separation by a laboratory measured differential path length factor (DPF) which accounts for the increased distance traveled by light due to scattering. DPF has been measured by time of flight techniques on small populations of adults and postmortem infants. The values for adults are greater than those for newborns, and it is not clear how to interpolate the present data for studies on children. Recent developments in instrumentation using phase resolved spectroscopy techniques have produced a bedside unit which can measure optical path length on any subject. We have developed an intensity modulated optical spectrometer which measures path length at four wavelengths. Two hundred and eighty three subjects from 1 d of age to 50 y were studied. Measurements were made at a fixed frequency of 200 MHz and a source detector separation of 4.5 cm. Results suggest a slowly varying age dependence of DPF, following the relation DPF690 = 5.38 + 0.049A0.877, DPF744 = 5.11 + 0.106A0.723, DPF807 = 4.99 + 0.067A0.814, and DPF832 = 4.67 + 0.062A0.819, where DPF690 is the DPF measured at 690 nm and A is age is expressed in years from full term. There was a wide scatter of values, however, implying that ideally DPF should be measured at the time of each study. PMID:8726247

Duncan, A; Meek, J H; Clemence, M; Elwell, C E; Fallon, P; Tyszczuk, L; Cope, M; Delpy, D T

1996-05-01

71

Determination of nanomolar concentrations of nitrite and nitrate in natural waters using long path length absorbance spectroscopy  

SciTech Connect

The concentrations of nitrite and nitrate in many natural waters are below the detection limits of conventional colorimetric analysis. A liquid core waveguide (LCW) has been used to extend the sensitivity of conventional colorimetric nitrite and nitrate determinations by more than an order of magnitude. Long path length absorbance spectroscopy (LPAS) with a 4.5 m path length LCW made of Teflon AF-2400 provides detection limits for NO{sub 2}{sup {minus}} and NO{sub 3}{sup {minus}} equal to 0.5 and 1.5 nM, respectively. The absorbance response of the LPAS system varies linearly with concentration. Calculations of azo dye molar absorbance using LPAS observations at nanomolar concentrations are in excellent agreement with molar absorbance results obtained with conventional measurement systems at much higher concentrations. For 1 nM NO{sub 2}{sup {minus}} and NO{sub 3}{sup {minus}} concentration differences, the 4.5 m path length LCW used in this work produces absorbance differences on the order of 0.02. No significant changes in the behavior of the LPAS system have been observed for periods of 6 month and more. The system is simple, rugged, and amenable to field studies.

Yao, W.; Byrne, R.H.; Waterbury, R.D. [Univ. of South Florida, St. Petersburg, FL (United States). Dept. of Marine Science] [Univ. of South Florida, St. Petersburg, FL (United States). Dept. of Marine Science

1998-09-01

72

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

73

PATH  

NSDL National Science Digital Library

Started in the 1970s as an agency to assist men and women in gaining access to a variety of birth control methods, PATH has since expanded its focus to provide "sustainable, culturally relevant [health] solutions, enabling communities worldwide to break longstanding cycles of poor health." The PATH website has more than a dozen videos and slideshows available to visitors at the "Our Multimedia" link near the bottom right hand corner of the homepage. A three-minute video entitled "Better Nutrition For Life" educates visitors about an innovative rice product that could bring greater nutrition to millions of malnourished people where rice is a staple food. The product is Ultra Rice, and is actually fortified pasta that looks, cooks, and tastes like rice, but is fortified with nutrients. The "rice" can be fortified with the needed nutrients the particular population being served is lacking. A slideshow about TB in the Ukraine, explains to visitors why there has been a resurgence of TB in Eastern Europe, and how PATH and its partners set out to help control it throughout the region.

74

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)  

Microsoft Academic Search

The effect of environmental factors in general and rain droplets in particular, on microwave propagation is a very well known\\u000a fact now. If the rain droplets are present in an inhomogeneous way across the path length of the microwave communication system\\u000a then, a new concept of path length reduction factor is introduced which accounts for the inhomogeneous nature of the

Parshotam Sharma; Inderjit Singh Hudiara; Maninder Lal Singh

2011-01-01

75

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

76

Tibiofemoral centroid velocity correlates more consistently with cartilage damage than does contact path length in two ovine models of stifle injury.  

PubMed

Anterior cruciate ligament (ACL) rupture and/or meniscal injury are known risk factors for post-traumatic osteoarthritis. We tested the hypothesis that increasingly abnormal tibiofemoral centroid path lengths and velocities would correlate with the severity of cartilage damage in injured sheep. Six sheep underwent combined ACL/medial collateral ligament transection (ACL/MCLx), five complete lateral meniscectomy (Mx), and four sham arthrotomy (Sham). Weighted centroids were used to estimate in vivo tibiofemoral cartilage contact path length during stance and the velocity of relative motion. Cartilage morphology was graded at dissection. Ligament transection significantly elongated plateau centroid path lengths and velocities, whereas condyle paths and velocities were reduced. Differences between plateau and femoral velocities (relative centroid velocity) were increased up to 10-fold over baseline values in the medial compartment. Reductions in Mx lateral compartment paths were significantly different from ACL/MCLx paths, but not relative to baseline or Sham values. Importantly, only centroid velocities consistently correlated with cartilage damage in either injury model, suggesting that while path length is valuable in detecting changes in the envelope of joint motion, it may average out meaningful peaks in the rate of relative motion that more closely relate to the mechanisms that might be damaging articular cartilage in these models. PMID:23832294

Beveridge, Jillian E; Heard, Bryan J; Shrive, Nigel G; Frank, Cyril B

2013-11-01

77

Directionality of real world networks as predicted by path length in directed and undirected graphs  

NASA Astrophysics Data System (ADS)

Many real world networks either support ordered processes, or are actually representations of such processes. However, the same networks contain large strong connectivity components and long circles, which hide a possible inherent order, since each vertex can be reached from each vertex in a directed path. Thus, the presence of an inherent directionality in networks may be hidden. We here discuss a possible definition of such a directionality and propose a method to detect it. Several common algorithms, such as the betweenness centrality or the degree, measure various aspects of centrality in networks. However, they do not address directly the issue of inherent directionality. The goal of the algorithm discussed here is the detection of global directionality in directed networks. Such an algorithm is essential to detangle complex networks into ordered process. We show that indeed the vast majority of measured real world networks have a clear directionality. Moreover, this directionality can be used to classify vertices in these networks from sources to sinks. Such an algorithm can be highly useful in order to extract a meaning from large interaction networks assembled in many domains.

Rosen, Yonatan; Louzoun, Yoram

2014-05-01

78

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

PubMed Central

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. PMID:21158298

Lu, Hsiao-Ming; Mann, Greg; Cascio, Ethan

2010-01-01

79

Leaf morphological effects predict effective path length and enrichment of 18O in leaf water of different Eucalyptus species  

NASA Astrophysics Data System (ADS)

Stable isotopes have been a valuable tool to study water or carbon fluxes of plants and ecosystems. In particular oxygen isotopes (?18O) in leaf water or plant organic material are now beginning to be established as a simple and integrative measure for plant - water relations. Current ?18O models, however, are still limited in their application to a broad range of different species and ecosystems. It remains for example unclear, if species-specific effects such as different leaf morphologies need to be included in the models for a precise understanding and prediction of ?18O signals. In a common garden experiment (Currency Creek Arboretum, South Australia), where over 900 different Eucalyptus species are cultivated in four replicates, we tested effects of leaf morphology and anatomy on ?18O signals in leaf water of 25 different species. In particular, we determined for all species enrichment in 18O of mean lamina leaf water above source water (?18O) as related to leaf physiology as well as leaf thickness, leaf area, specific leaf area and weight and selected anatomical properties. Our data revealed that diurnal ?18O in leaf water at steady state was significantly different among the investigated species and with differences up to 10% at midday. Fitting factors (effective path length) of leaf water ?18O models were also significantly different among the investigated species and were highly affected by species-specific morphological parameters. For example, leaf area explained a high percentage of the differences in effective path length observed among the investigated species. Our data suggest that leaf water ?18O can act as powerful tool to estimate plant - water relations in comparative studies but that additional leaf morphological parameters need to be considered in existing ?18O models for a better interpretation of the observed ?18O signals.

Kahmen, A.; Merchant, A.; Callister, A.; Dawson, T. E.; Arndt, S. K.

2006-12-01

80

Retrieval of atmospheric carbon dioxide and methane from GOSAT data with the photon path length probability density function method  

NASA Astrophysics Data System (ADS)

The Greenhouse Gases Observing Satellite "IBUKI" (GOSAT) is the world's first spacecraft to measure the concentrations of carbon dioxide (CO2) and methane (CH4). The satellite has been operating properly from January 23, 2009. This paper presents retrievals of CO2 and CH4 from GOSAT data with the photon pathlength probability density function (PPDF) method that has been developed at the National Institute of Environmental Studies. This paper focus on a validation of the retrievals using satellite data during 38 months of GOSAT operation from June 2009 and ground-based Fourier Transform Spectrometer measurements from the Total Carbon Column Observing Network (TCCON) as the reference data for the column-averaged dry air mole fractions of the atmospheric gases. The TCCON-GOSAT coincidence criteria for validating the satellite-based retrievals included GOSAT single scan data over land within a 5° radius latitude/ longitude circle centered at each of 12 TCCON stations. The ground-based TCCON data were mean values measured within plus/minus 1 hour of the GOSAT overpass time. We use the latest version of PPDF-based method that retrieves simultaneously gas abundance and light path modification through the atmosphere. The radiance spectra from all three GOSAT SWIR bands (0.76 ?m; 1.6 ?m and 2.0 ?m) were used to retrieve CO2 and basic PPDF parameters that described light path shortening and light path lengthening. The retrieval state vector also included vertical profile of CO2 mixing ratio; scaling factor of prior water vapor profile; and stretch factor for adjusting the position of the wave-number grids. Temperature and surface pressure data were prescribed and provided by Japan Meteorological Agency. For the methane retrievals we processed radiance spectra in 1.67-?m absorption band using PPDF parameters derived from simultaneous CO2 and PPDF retrievals. In particular, a statistical pairwise comparison between GOSAT and TCCON coincident measurements of CO2 column abundance (over 3500 GOSAT single scans) performed with the weighed least squares fit showed a correlation coefficient 0.8; a standard deviation of 1.9 ppm, negative bias of 0.4 ppm; and slope of 1.04 for the slope-intercept form of the linear regression. After a posteriori bias correction these characteristics were 0.9; 1.65 ppm; 0.01 ppm; and 0.99, respectively.

Oshchepkov, Sergey; Bril, Andrey; Yokota, Tatsuya; Yoshida, Yukio

2014-05-01

81

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

82

Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer.  

PubMed

A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO(2), HCHO, SO(2), H(2)O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg. PMID:16892129

Frins, Erna; Bobrowski, Nicole; Platt, Ulrich; Wagner, Thomas

2006-08-20

83

In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy: influence of photosensitizer formulation and tissue location  

NASA Astrophysics Data System (ADS)

In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan® in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg® and Foslip®, on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mg kg-1. FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R2) between FDPS and extraction was found for all formulations in the liver (R2=0.79). A much lower R2 between FDPS and extraction was found in lip (R2=0.46) and tongue (R2=0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution.

de Visscher, Sebastiaan A. H. J.; Witjes, Max J. H.; Kaš?áková, Slávka; Sterenborg, Henricus J. C. M.; Robinson, Dominic J.; Roodenburg, Jan L. N.; Amelink, Arjen

2012-06-01

84

The Noninvasive Measurement of Absolute Cerebral Deoxyhemoglobin Concentration and Mean Optical Path Length in the Neonatal Brain by Second Derivative Near Infrared Spectroscopy (Regular Articles)  

Microsoft Academic Search

We have used second differential near infrared spectroscopy of water to determine the mean optical path length of the neonatal brain. By obtaining the ratio of the second differential features of deoxyhemoglobin to those of water, the absolute cerebral concentration of deoxyhemoglobin can be monitored continuously and noninvasively. Nineteen neonates were studied; the gestational age at birth varied from 23

S. J. MATCHER; Chris Cooper; Hamamatsu Photonics

85

Path-length correction for the haemoglobin-concentration measurement using the skull cranial window by multi-spectral imaging analysis  

NASA Astrophysics Data System (ADS)

The concentration changes in oxygenated haemoglobin and deoxygenated haemoglobin in the brain cortex of guinea pigs associated with brain activation are measured from the multi-spectral images of the cortical tissue. The cortical tissue is observed through a thinned skull. The wavelength dependence of the optical path length is considered in the calculation of haemoglobin concentration. The results are compared with those obtained from the multi-spectral images of the exposed cortex to evaluate the influence of the thinned skull on the measurement of the concentration changes by multispectral imaging system. Although the skull thickness affected the sensitivity of the change in reflectance due to decrease in optical path in the cortical tissue, the influence of skull on the wavelength dependence of the optical path length can be ignored when the skull thickness is approximately less than 100 ?m.

Sakaguchi, Koichiro; Furukawa, Shunsuke; Katsura, Takushige; Yamazaki, Kyoko; Kawaguchi, Hideo; Maki, Atsushi; Okada, Eiji

2007-07-01

86

The noninvasive measurement of absolute cerebral deoxyhemoglobin concentration and mean optical path length in the neonatal brain by second derivative near infrared spectroscopy.  

PubMed

We have used second differential near infrared spectroscopy of water to determine the mean optical path length of the neonatal brain. By obtaining the ratio of the second differential features of deoxyhemoglobin to those of water, the absolute cerebral concentration of deoxyhemoglobin can be monitored continuously and noninvasively. Nineteen neonates were studied; the gestational age at birth varied from 23 to 38 wk, and the postconceptual age, when the spectra were recorded, ranged from 35 to 48 wk. The calculated mean deoxyhemoglobin concentration was 14.6 +/- 4.0 microM; the differential path length factor (mean optical path length/optode separation) calculated from the water peak at 730 nm was 4.66 +/- 1.01, and that calculated at the 830-nm peak was 3.91 +/- 0.75. These values are consistent with path length measurements using laser time-of-flight spectroscopy on postmortem neonates and phase-resolved spectroscopy on live neonates. Induced arterial oxygen saturation decreases from 98 to 93% showed no significant change in the mean optical path length, despite significant cerebral desaturation. Changes in the deoxyhemoglobin concentration after this procedure were identical, whether measured by second differential analysis at 760 nm or by multilinear regression over the wavelength range 740-900 nm. When combined with existing methods of measuring total cerebral hemoglobin concentration, second differential near infrared spectroscopy can be used to derive the mean cerebral oxygen saturation. A preliminary experiment outlined the feasibility of this approach and yielded a saturation value of 63%, consistent with near infrared sampling of a predominantly venous pool in the brain. PMID:8825383

Cooper, C E; Elwell, C E; Meek, J H; Matcher, S J; Wyatt, J S; Cope, M; Delpy, D T

1996-01-01

87

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

88

LONG PATH DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER AND EPA-APPROVED FIXED POINT METHODS INTERCOMPARISON  

EPA Science Inventory

Differential optical absorption spectrometry (DOAS) has been used by a number of investigators over the past 10 years to measure a wide range of gaseous air pollutants. ecently OPSIS AB, Lund, Sweden, has developed and made commercially available DOAS instrument that has a number...

89

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

90

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

91

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

92

Analyzing Water's Optical Absorption  

NASA Technical Reports Server (NTRS)

A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

2002-01-01

93

Tornado Paths  

NSDL National Science Digital Library

This website catalogs all the tornado paths in the United States since 1950. The tornado path data is overlaid onto a Google Maps base for easy browsing and manipulation of the map view. Clicking on individual tornados provides the user with information such as its Fujita rating, the amount of damage caused by the tornado, the size of the path that the tornado made, and the length of time the tornado was on the ground.

Samson, Perry; Michigan, University O.

94

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

95

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

96

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 SocietyÃÂs 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

97

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

98

Length-constrained Path-matchings in Graphs M. Ghodsi , M.T. Hajiaghayi y , M. Mahdian y , and V.S. Mirrokni y  

E-print Network

-matching in G covering S is a collection C of paths in G, such that every vertex of S is an endpoint of exactly-disjoint, or edge-disjoint, if the collection of paths has this property. The path-matching problem is to #12;nd (if by the paths, and the weight of the paths in weighted graphs can also be considered (see Cohen et al. [1

Hajiaghayi, Mohammad

99

Development of formulae for estimating amylose content, amylopectin chain length distribution, and resistant starch content based on the iodine absorption curve of rice starch.  

PubMed

Not only amylose but also amylopectin greatly affects the gelatinization properties of rice starch and the quality of cooked rice grains. We here characterized the starches of 32 rice cultivars and evaluated the relationship between their iodine absorption curve, apparent amylose content (AAC), pasting property, resistant starch (RS) content, and chain length distribution of amylopectin. We found that the iodine absorption curve differed among the various sample rice cultivars. Using the wavelength at which absorbance becomes maximum on iodine staining of starch (?max), we propose a novel index, "new ?max" (AAC/(?max of sample rice starches-?max of glutinous rice starch)). We developed the novel estimation formulae for AAC, RS contents, and amylopectin fractions with the use of ?max and "new ?max." These formulae would lead to the improved method for estimating starch properties using an easy and rapid iodine colorimetric method. PMID:25384364

Nakamura, Sumiko; Satoh, Hikaru; Ohtsubo, Ken'ichi

2014-11-11

100

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 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 76 m path length, 0.5 L volume multiple pass absorption cell. Detection is achieved using a thermoelectrically

R. Ellis; J. G. Murphy; R. van Haarlem; E. Pattey; J. O'Brien

2009-01-01

101

Effect of hydrocarbon chain length in 1,2-alkanediols on percutaneous absorption of metronidazole: toward development of a general vehicle for controlled release.  

PubMed

The objective of the present study is to investigate the effect of hydrocarbon chain length in 1,2-alkanediols on percutaneous absorption of metronidazole (MTZ). Twelve formulations (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol in 4% concentration, 1,2-hexanediol, and 1,2-heptanediol in 1% concentration, in the absence and presence of 1,4-cyclohexanediol, respectively) were studied in an in vitro hairless mouse skin model using Franz diffusion cell. Based on the flux values and retardation ratios (RR), a penetration retardation effect on percutaneous absorption of MTZ was observed for the formulations containing 1,2-diols having six- to seven-carbon chain in the presence of 1,4-cyclohexanediol (1,2-hexanediol with chain length of six hydrocarbons, RRs are 0.69 and 0.76 in the concentration of 4% and 1%, respectively; 1,2-heptanediol with chain length of seven hydrocarbons, RR is 0.78 in the concentration of 1%). On the other hand, no retardation effect was observed in formulations containing short alkyl chains (RRs of 1,2-propanediol, 1,2-butanediol, and 1,2-pentanediol are 0.99, 1.61, and 0.96, respectively). Instead, a penetration enhancement effect was observed for 1,2-diols having four and five carbons. In other words, effect of 1,2-alkanediols on percutaneous absorption of MTZ can be systematically modulated by simply varying number of -CH2 groups in the hydrocarbon chain-from being a penetration enhancer to retardant. These observations shed light on mechanism of the penetration enhancement and retardation effect and provide insight into rational design of penetration enhancers and retardants. Furthermore, the combination of 1,2-alkanediols and 1,4-cyclohexanediol could become a general vehicle for controlled release of pharmaceutical and cosmetic active ingredients. PMID:24395400

Li, Nan; Jia, Weibu; Zhang, Yan; Zhang, Michelle C; Tan, Fengping; Zhang, Jerry

2014-04-01

102

Earth's Atmospheric CO2 Saturated IR Absorption  

Microsoft Academic Search

Using the on-line SpectraCalc IR absorption simulator, the amount of IR absorption by the 15 mu line of the current atmospheric CO2 was obtained and compared with that of twice the amount of CO2. The simulation required a fixed density equivalent for the atmospheric path length. This was obtained by numerically integrating the NOAA Standard Atmospheric model. While the current

Ernst Wall

2008-01-01

103

Relation between bond-length alternation and two-photon absorption of a push pull conjugated molecules: a quantum-chemical study  

NASA Astrophysics Data System (ADS)

The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ( ?) of a series of prototypical ?-conjugated push-pull molecules are presented. The calculations of ? for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ( ? and ?) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of ? on the BLA parameter was noticed.

Bartkowiak, W.; Zale?ny, R.; Leszczynski, J.

2003-02-01

104

A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device.  

PubMed

In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions. PMID:20019398

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

2010-01-21

105

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

106

A long path, low temperature cell.  

PubMed

Design and performance are given of a multiple traversal low temperature absorption cell that operates routinely at a path length of 230 m. The system is comprised of an f/30-aperture White cell surrounded by an aluminum Dewar. The cell has been used in the temperature range 300-77 K and may be pressurized to 3 atm. Vacuum feedthrough adjustments are employed in order to correct for defocusing of the mirrors during the cooling process. PMID:20068970

Blickensderfer, R P; Ewing, G E; Leonard, R

1968-11-01

107

The influence of a probe on the optical path of atomic absorption spectrometer with a graphite tube atomizer  

NASA Astrophysics Data System (ADS)

We have studied the influence on the atomic absorption signal of the obscuring of the transmission beam by a probe for the two-stage atomization in a graphite tube atomizer. The following parameters were varied: the thickness of the probe (0.5-1.0 mm), its displacement from the optical axis of the spectrometer (up to 2 mm), the diameter of the transmission beam (1.3-4.0 mm), the slit width of the monochromator, and the shape of the intensity distribution over the cross section of the beam emitted either by a hollow cathode lamp, or a deuterium lamp, or an electrodeless lamp. We have shown that, using a probe with a thickness that is optimal for the two-stage atomization (1 mm), it is possible to register analytical absorption signals from 28 chemical elements out of 56 (except Hg), which can be determined in graphite atomizers, with a maximal sensitivity and with no optical interference. The remaining elements can be determined with a lower sensitivity because of the necessity to lower the temperature of the secondary atomization.

Zakharov, Yu. A.; Kokorina, O. B.; Okunev, R. V.

2014-04-01

108

The effects of forage particle length and exogenous phytase inclusion on phosphorus digestion and absorption in lactating cows.  

PubMed

Accurate estimates of phosphorus (P) availability from feed are needed to allow P requirements to be met with reduced P intake, thus reducing P excretion by livestock. Exogenous phytase supplementation in poultry and swine diets improves bioavailability of P, and limited research suggests that this strategy may have some application in dairy cattle rations. The effects of exogenous phytase and forage particle length on site and extent of P digestion were evaluated with 5 ruminally and ileally cannulated lactating cows (188 ± 35 d in milk). Cows were assigned in a 2 × 2 factorial arrangement of treatments in 2 incomplete Latin squares with four 21-d periods. Diets contained P slightly in excess of National Research Council requirements with all P from feed sources. During the last 4d of each period, total mixed ration, refusals, omasal, ileal, and fecal samples were collected and analyzed for total P, inorganic P (Pi), and phytate (Pp). Total P intake was not influenced by dietary treatments but Pp intake decreased and Pi intake increased with supplemental phytase, suggesting rapid action of the enzyme in the total mixed ration after mixing. Omasal flow of Pi decreased with phytase supplementation, but we observed no effect of diet in ileal flow or small intestinal digestibility of any P fraction. Fecal excretion of total P was slightly higher and Pp excretion was lower for cows receiving diets supplemented with phytase. Milk yield and composition were unaffected by diets. When phytase was added to the mixed ration, dietary Pp was rapidly degraded before intake and total-tract Pp digestion was increased. The lack of effect of phytase supplementation on dietary P utilization was probably because these late-lactation cows had a low P requirement and were fed P-adequate diets. PMID:24210479

Jarrett, J P; Wilson, J W; Ray, P P; Knowlton, K F

2014-01-01

109

Path planning for UAVs  

Microsoft Academic Search

In this paper, a two step path-planning algorithm for UAVs is proposed. The algorithm generates a stealthy path through a set of enemy radar sites of known location, and provides an intuitive way to trade-off stealth versus path length. In the first step, a suboptimal rough-cut path is generated through the radar sites by constructing and searching a graph based

S. A. Bortoff; E. Hartford

2000-01-01

110

Cross-Validation of Open-Path and Closed-Path Eddy-Covariance Techniques for Observing Methane Fluxes  

NASA Astrophysics Data System (ADS)

Methane () fluxes observed with the eddy-covariance technique using an open-path analyzer and a closed-path analyzer in a rice paddy field were evaluated with an emphasis on the flux correction methodology. A comparison of the fluxes obtained by the analyzers revealed that both the open-path and closed-path techniques were reliable, provided that appropriate corrections were applied. For the open-path approach, the influence of fluctuations in air density and the line shape variation in laser absorption spectroscopy (hereafter, spectroscopic effect) was significant, and the relative importance of these corrections would increase when observing small fluxes. A new procedure proposed by Li-Cor Inc. enabled us to accurately adjust for these effects. The high-frequency loss of the open-path analyzer was relatively large (11 % of the uncorrected covariance) at an observation height of 2.5 m above the canopy owing to its longer physical path length, and this correction should be carefully applied before correcting for the influence of fluctuations in air density and the spectroscopic effect. Uncorrected fluxes observed with the closed-path analyzer were substantially underestimated (37 %) due to high-frequency loss because an undersized pump was used in the observation. Both the bandpass and transfer function approaches successfully corrected this flux loss. Careful determination of the bandpass frequency range or the transfer function and the cospectral model is required for the accurate calculation of fluxes with the closed-path technique.

Iwata, Hiroki; Kosugi, Yoshiko; Ono, Keisuke; Mano, Masayoshi; Sakabe, Ayaka; Miyata, Akira; Takahashi, Kenshi

2014-04-01

111

Multiscattering-enhanced absorption spectroscopy.  

PubMed

An original scheme for sensitive absorption measurements, particularly well-suited for low analyte concentrations, is presented. The technique is based on multiscattering-enhanced absorption spectroscopy (MEAS) and benefits from the advantages of conventional absorption spectroscopy: simplicity, rapidity, and low costs. The technique relies on extending the optical path through the sensing volume by suspending dielectric beads in the solution containing the analytes of interest, resulting in multiple scattering of light, which increases the optical path length through the sample. This way, a higher sensitivity and lower limit of detection, compared to those of conventional absorption spectroscopy, can be achieved. The approach is versatile and can be used for a broad variety of analytes. Here, it is applied to the detection of phenol red, 10 nm gold nanoparticles, and envy green fluorescence dye; the limit of detection is decreased by a factor of 7.2 for phenol red and a factor of 3.3 for nanoparticles and dye. The versatility of this approach is illustrated by its application in increasing the sensitivity of colorimetric detection with gold nanoparticle probes and a commercially available hydrogen peroxide bioassay. The influence of different parameters describing the scattering medium is investigated in detail experimentally and numerically, with very good agreement between the two. Those parameters can be effectively used to tailor the enhancement for specific applications and analytes. PMID:25546088

Koman, Volodymyr B; Santschi, Christian; Martin, Olivier J F

2015-02-01

112

Azimuthal Anisotropy of {pi}{sup 0} Production in Au+Au Collisions at {radical}(s{sub NN})=200 GeV: Path-Length Dependence of Jet Quenching and the Role of Initial Geometry  

SciTech Connect

We have measured the azimuthal anisotropy of {pi}{sup 0} production for 1path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

Adare, A.; Bickley, A. A.; Ellinghaus, F.; Glenn, A.; Kinney, E.; Kiriluk, K.; Linden Levy, L. A.; Nagle, J. L.; Rosen, C. A.; Seele, J.; Wysocki, M. [University of Colorado, Boulder, Colorado 80309 (United States); Afanasiev, S.; Isupov, A.; Litvinenko, A.; Malakhov, A.; Peresedov, V.; Rukoyatkin, P.; Zolin, L. [Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation); Aidala, C.; Datta, A. [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003-9337 (United States)

2010-10-01

113

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

2014-12-10

114

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

E-print Network

Effective utilization of quantum-cascade distributed-feedback lasers in absorption spectroscopy quantum-cascade lasers. This technique was combined with a 100-m path-length multipass cell and a zero.6320, 010.1280. 1. Introduction Recently developed quantum-cascade lasers1 have been demonstrated

115

Absorption spectroscopy in the ultraviolet and visible spectral range of hexavalent chromium aqueous solutions  

NASA Astrophysics Data System (ADS)

In order to demonstrate the possibility of performing direct absorption spectroscopy of Hexavalent Chromium aqueous solutions, absorption measurements were performed at the dual- beam spectrophotometer in the 250 - 850 nm spectral range, with 10 mm and 100 mm path lengths. Low concentration (26 - 520 (mu) g/l) (and high concentration (2.6 - 52 mg/l) solutions were analyzed, showing that it is possible to implement a basic instrumentation for risk condition monitoring and a more advanced instrumentation for quantitative measurements.

Mignani, Anna G.; Spadoni, Lorenzo

1999-09-01

116

Atomic absorption spectrophotometer  

SciTech Connect

In atomic absorption spectrophotometer, a reference path may be provided for radiation which excludes the flame. This radiation provides a signal from a detector which varies only with the instrumental drift produced by variations in the radiation source brightness and by variations in detector gain. The signal can be used to compensate for drift in other signals received through a sample path including the flame. In the present invention, radiation passes through the sample path continuously during measurement, and only through the reference path between sample measurements. Movable mirrors shift the radiation between the paths upon externally applied commands. Conveniently, the reference path measurement is made while the flame is stabilized during the change between samples. The reference path measurements are stored and used to correct for drift.

Stockdale, T. J.

1985-04-02

117

Measuring Length  

NSDL National Science Digital Library

This article focuses on young students encountering the measurement of length. The article cites examples of key concepts in recognizing length as an attribute and in proper and improper ways to measure length. Conservation and additivity of length, standard and non-standard units, iteration, and the zero point are among the topics presented.

2009-08-01

118

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

119

Completely automated open-path FT-IR spectrometry.  

PubMed

Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured "short path-length" background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention. PMID:18946664

Griffiths, Peter R; Shao, Limin; Leytem, April B

2009-01-01

120

Spreading paths in partially observed social networks  

PubMed Central

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using a static, structurally realistic social network as a platform for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is. PMID:22587148

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-01-01

121

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

122

Path Pascal  

NASA Technical Reports Server (NTRS)

Path Pascal is high-level experimental programming language based on PASCAL, which incorporates extensions for systems and real-time programming. Pascal is extended to treat real-time concurrent systems.

Campbell, R. H.; Kolstad, R. B.; Holle, D. F.; Miller, T. J.; Krause, P.; Horton, K.; Macke, T.

1983-01-01

123

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

124

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

125

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

126

A conformation and orientation model of the carboxylic group of fatty acids dependent on chain length in a Langmuir monolayer film studied by polarization-modulation infrared reflection absorption spectroscopy.  

PubMed

The conformation of the carboxylic group of fatty acids in a Langmuir (L) monolayer film on water is described in relation to the aggregation property of the hydrocarbon chain. Polarization-modulation infrared reflection absorption spectra (PM-IRRAS) of L films of heptadecanoic acid (C(17)), octadecanoic acid (C(18)), and nonadecanoic acid (C(19)) exhibit systematic spectral changes in both the C-H and C=O stretching vibration regions. Through a stabilization analysis of the L films at a high surface pressure, the C(19) L film has been found outstandingly stable exhibiting no film shrink, while the other two compounds exhibit a large shrink at high surface pressure. By taking into account the uniquely high aggregation property of the hydrocarbon chains of C(19), the three major bands arising from the C=O stretching vibration mode propose three types of molecular conformations about the carboxylic group, which are elucidated by a balance of the hydration of the carboxylic group, the chain length of the hydrocarbon chain, and the surface pressure. PMID:20718412

Muro, Maiko; Itoh, Yuki; Hasegawa, Takeshi

2010-09-01

127

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

128

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

129

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

PubMed Central

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. PACS 78.40.Fy; 78.67.Uh; 78.67.-n PMID:25276106

2014-01-01

130

Quantitative infrared absorption cross sections of isoprene for atmospheric measurements  

SciTech Connect

The OH- and O3- initiated oxidations of isoprene, which is one of the primary volatile organic compounds produced by vegetation, are a major source of atmospheric formaldehyde and other oxygenated organics, yet little quantitative IR data exists for isoprene. We thus report absorption coefficients 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 19.96 cm path length cell at 0.112 cm-1 resolution, using a Bruker 66V FTIR. Composite spectra are derived from a minimum of seven pressures at each temperature.

Brauer, Carolyn S.; Blake, Thomas A.; Guenther, Alex B.; Sharpe, Steven W.; Sams, Robert L.; Johnson, Timothy J.

2014-11-19

131

A Random Walk on a Circular Path  

ERIC Educational Resources Information Center

This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.

Ching, W.-K.; Lee, M. S.

2005-01-01

132

Thermooptic-based differential measurements of weak solute absorptions with an interferometer.  

PubMed

An interferometric method of measuring small differences between weak optical absorptions of solutions has been developed using the thermooptic effect. To record the small changes in optical path length ~lambda/200 due to heating, it was necessary to stabilize the fringe pattern with respect to slow thermal drift using a galvanometer-driven compensator plate controlled by a closed feedback loop. Fringe shifts from background absorptions were nulled out to better than 1 part in 400, permitting the measurement of differences in absorptions between two solutions that were l/100th of background. Using laser powers of 100 mW, absorptions approximately 5 x 10(-6) cm(-1) (base e) could be measured with CC1(4) solutions. PMID:20389912

Cremers, D A; Keller, R A

1982-05-01

133

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

134

Measurements of NH3 absorption coefficients with a C-13/O-16/2 laser  

NASA Technical Reports Server (NTRS)

Measurements of NH3 absorption coefficients are presented for several transitions of a C-13(O-16)2 laser for small concentrations of NH3(p less than 1 torr) for absorption lines broadened to 1 atm with N2. NH3 absorption coefficients were determined for laser transitions R(8)(920.2194 wavelengths/cm) to R(28)(933.8808 wavelengths/cm) of the 00 1 - (10 0,02 0)I band. The strongest absorption coefficient K = 36.09 + or - 1.43 per (atm-cm) was measured for the R(18) transition for the NH3 line, aQ(6,6), and is larger than has been found in any previous measurements with a CO2 laser. The dependence of K on total pressure was also obtained for select transitions, and the frequency separation between the R(18) laser transition and the neighboring NH3 line aQ(6,6) was determined to be 550 + or - 50 MHz. These results are significant for long path absorption monitoring of NH3 with CO2 lasers since the path length can be reduced by approximately 40% and for heterodyne detection of NH3 since the relative position of the laser transition to the NH3 absorption line is well within the bandpass of Hg-Cd-Te photomixers.

Allario, F.; Seals, R. K., Jr.

1975-01-01

135

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

136

Short paths in expander graphs  

SciTech Connect

Graph expansion has proved to be a powerful general tool for analyzing the behavior of routing algorithms and the interconnection networks on which they run. We develop new routing algorithms and structural results for bounded-degree expander graphs. Our results are unified by the fact that they are all based upon, and extend, a body of work asserting that expanders are rich in short, disjoint paths. In particular, our work has consequences for the disjoint paths problem, multicommodify flow, and graph minor containment. We show: (i) A greedy algorithm for approximating the maximum disjoint paths problem achieves a polylogarithmic approximation ratio in bounded-degree expanders. Although our algorithm is both deterministic and on-line, its performance guarantee is an improvement over previous bounds in expanders. (ii) For a multicommodily flow problem with arbitrary demands on a bounded-degree expander, there is a (1 + {epsilon})-optimal solution using only flow paths of polylogarithmic length. It follows that the multicommodity flow algorithm of Awerbuch and Leighton runs in nearly linear time per commodity in expanders. Our analysis is based on establishing the following: given edge weights on an expander G, one can increase some of the weights very slightly so the resulting shortest-path metric is smooth - the min-weight path between any pair of nodes uses a polylogarithmic number of edges. (iii) Every bounded-degree expander on n nodes contains every graph with O(n/log{sup O(1)} n) nodes and edges as a minor.

Kleinberg, J. [MIT, Cambridge, MA (United States); Rubinfeld, R. [Cornell Univ., Ithaca, NY (United States)

1996-12-31

137

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

138

A cryogenic circulating advective multi-pass absorption cell.  

PubMed

A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10(7) cm(-3). A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena. PMID:22462957

Stockett, M H; Lawler, J E

2012-03-01

139

A cryogenic circulating advective multi-pass absorption cell  

SciTech Connect

A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10{sup 7} cm{sup -3}. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

Stockett, M. H.; Lawler, J. E. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States)

2012-03-15

140

A cryogenic circulating advective multi-pass absorption cell  

NASA Astrophysics Data System (ADS)

A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 107 cm-3. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

Stockett, M. H.; Lawler, J. E.

2012-03-01

141

Method of spectral subtraction of gas-phase Fourier transform infrared (FT-IR) spectra by minimizing the spectrum length.  

PubMed

A new method of spectral subtraction for gas-phase Fourier transform infrared (FT-IR) spectra was developed for long-path gas measurements. The method is based on minimization of the length of the spectrum that results from subtracting the spectrum of an individual component of a gas mixture (water, CO(2), etc.) from the experimental spectrum of the mixture. For this purpose a subtraction coefficient (k(min)) is found for which the length of the resulting spectrum is minimized. A mathematical simulation with two Lorentzian absorption bands was conducted and the limits of application for the proposed method were determined. Two experimental examples demonstrate that a successful result could be achieved in the case when the subtrahend spectrum contains a number of narrow absorption bands (such as the spectrum of water vapor). PMID:21819781

Kozlov, Denis; Besov, Alexey

2011-08-01

142

Measuring high spectral resolution specific absorption coefficients for use with hyperspectral imagery  

SciTech Connect

A portable, long path length (50 cm), flow through, absorption tube system is utilized to obtain in-situ specific absorption coefficients from various water environments consisting of both clear and turbid water conditions from an underway ship or vessel. The high spectral resolution absorption signatures can be obtained and correlated with measured water quality parameters along a ship track. The long path cuvette system is capable of measuring important water quality parameters such as chlorophyll-a, seston or total suspended matter, tannins, humics, fulvic acids, or dissolved organic matter (dissolved organic carbon, DOC). The various concentrations of these substances can be determined and correlated with laboratory measurements using the double inflection ratio (DIR) of the spectra based upon derivative spectroscopy. The DIR is determined for all of the possible combinations of the bands ranging from 362-1115 nm using 252 channels, as described previously by Bostater. The information gathered from this system can be utilized in conjunction with hyperspectral imagery that allows one to relate reflectance and absorption to water quality of a particular environment. A comparison is made between absorption signatures and reflectance obtained from the Banana River, Florida.

Keller, M.; Bostater, C. [Florida Institute of Technology, Melbourne, FL (United States)

1997-06-01

143

Optimization of hollow waveguides as absorption cells for spectroscopic gas sensing.  

PubMed

Flexible and low-loss hollow waveguide has many advantages as an absorption cell for spectroscopic gas sensing. The characteristics of the sensing system are dependent on the parameters of the hollow waveguide cell. In this paper, a mathematical model was proposed to analyze the waveguide cell by considering waveguide loss, effective optical path length, and signal-to-noise ratio of the system. Simulation results show that the gas absorption intensity and system sensitivity are dependent not only on the waveguide length but also on the bore-diameter, signal-to-noise ratio, and the concentration of the target gases. The results provide optimizing methods for the sensing system and algorithms for error compensation. Preliminary experiments on concentration detection of methane gas were carried out and measured data showed good agreements with the simulation results. PMID:23452494

Zhou, Jia-Qi; Lu, Wei-Jia; Yao, Zhang-Rui; Wei, Yu-Qing; Shi, Yi-Wei

2013-03-01

144

[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

145

Soliton absorption spectroscopy  

SciTech Connect

We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width by using a perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires a spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively mode-locked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurements in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improvement in the sensitivity and spectroscopic accuracy, which makes soliton absorption spectroscopy a promising measurement technique.

Kalashnikov, V. L.; Sorokin, E. [Institut fuer Photonik, TU Wien, Gusshausstr. 27/387, A-1040 Vienna (Austria)

2010-03-15

146

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

147

Path Coupling and Aggregate Path Coupling  

E-print Network

In this survey paper, we describe and characterize an extension to the classical path coupling method applied statistical mechanical models, referred to as aggregate path coupling. In conjunction with large deviations estimates, we use this aggregate path coupling method to prove rapid mixing of Glauber dynamics for a large class of statistical mechanical models, including models that exhibit discontinuous phase transitions which have traditionally been more difficult to analyze rigorously. The parameter region for rapid mixing for the generalized Curie-Weiss-Potts model is derived as a new application of the aggregate path coupling method.

Kovchegov, Yevgeniy

2015-01-01

148

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

149

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

150

Cooperative organic mine avoidance path planning  

NASA Astrophysics Data System (ADS)

The JHU/APL Path Planning team has developed path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Extending on previous years' efforts, we investigated real-world Naval mine avoidance requirements and developed a tactical decision aid (TDA) that satisfies those requirements. APL has developed new mine path planning techniques using graph based and genetic algorithms which quickly produce near-minimum risk paths for complicated fitness functions incorporating risk, path length, ship kinematics, and naval doctrine. The TDA user interface, a Java Swing application that obtains data via Corba interfaces to path planning databases, allows the operator to explore a fusion of historic and in situ mine field data, control the path planner, and display the planning results. To provide a context for the minefield data, the user interface also renders data from the Digital Nautical Chart database, a database created by the National Geospatial-Intelligence Agency containing charts of the world's ports and coastal regions. This TDA has been developed in conjunction with the COMID (Cooperative Organic Mine Defense) system. This paper presents a description of the algorithms, architecture, and application produced.

McCubbin, Christopher B.; Piatko, Christine D.; Peterson, Adam V.; Donnald, Creighton R.; Cohen, David

2005-06-01

151

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

152

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2011 CFR

... SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Technical...end points of a fixed link in the private operational...fixed point-to-point microwave services must equal...paragraph (c ): Links authorized prior...

2011-10-01

153

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2010 CFR

... SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Technical...end points of a fixed link in the private operational...fixed point-to-point microwave services must equal...paragraph (c ): Links authorized prior...

2010-10-01

154

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

155

Investigation of Diode Pumped Alkali Laser atmospheric transmission using tunable diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A field deployable ruggedized tunable diode laser absorption spectroscopy (TDLAS) device fiber coupled to a pair of 12.5" Ritchey-Chretien telescopes was used to study atmospheric propagation for open path lengths of 100 to 1,000 meters to estimate atmospheric transmission at key High Energy Laser (HEL) wavelengths. The potassium (K) version of the Diode Pumped Alkali Laser (DPAL) operates in between two of the sharp oxygen rotational features in the PP and the PQ branches. The device can be used to observe rotational temperature, concentrations, and atmospheric pressure. Molecular oxygen absorption lines near the potassium, and water vapor absorption lines near the rubidium and cesium DPALs at wavelengths near 770 nm, 795 nm, and 895 nm, respectively, were investigated using the Line-by-Line Radiative Transfer Model (LBLRTM) with the High Energy Laser End-to-End Simulation (HELEEOS). A tunable diode laser absorption spectroscopy (TDLAS) device was used to anchor simulations to actual outdoor atmospheric open-path collections. The implications of different laser gain cell configurations in DPAL systems are discussed, including spectral lineshape and atmospheric transmittance and are compared to existing high power laser systems.

Rice, Christopher A.

156

TATP stand-off detection with open path: FTIR techniques  

NASA Astrophysics Data System (ADS)

TATP is a very easy to synthesize [9], sensitive, high explosive [10] and high volatile explosive [1, 3, 7] with great absorption in the IR Spectra [4, 5, 6]. In this project we detect TATP gas traces with open path FTIR - techniques. The first project phase was to construct and build a heatable multi-reflection cell with adjustable optical path length and a heatable intake to evaporate solid TATP samples. In this cell reference TATP - spectra were collected under controlled conditions with a Bruker FTIR system (Typ OPAG 33). The next step was to find out how the TATP gas will be diluted in the ambient air and validate some physical properties which are described inconsistently in literature e.g. evaporation rates. We constructed a special double - T shaped chamber with stabile air conditions. In this chamber the dispersion kinetics of the TATP vapour could be tested. It turned out that the TATP vapours has the tendency to drop down. Therefore the highest TATP - concentrations were measured below the TATP sample. During the investigation for this study it turned out, that some materials scrub the TATP- vapour out of the air, e.g. Metals, fabric, leather. In the second phase of the project successful open path FTIR- measurements were taken in ambient air and will be continued with different system configurations of the OPAG 33 to lower the detection limits. Also successful measurements were taken in indoor ambient air with a Hyper spectral camera (passive FTIR with array sensor) to detect TATP in solid and gaseous phase. This technique allows detecting TATP and identifying the TATP source. The poster shows some selected results of the continued research.

Fischer, C.; Pohl, T.; Weber, K.; Vogel, A.; van Haren, G.; Schweikert, W.

2012-10-01

157

On the Drexel long path spectrophotometer: Status report  

SciTech Connect

A new horizontal version of the long path spectrophotometer is described and a preliminary measurement is reported. The attenuation length of unfiltered WITCO LP100 mineral oil is found to be 904 +- 34cm at a wavelength of 470 nm.

Ide, N.; Steinberg, R.I.

1987-01-03

158

Thermal Conductivity Spectroscopy Technique to Measure Phonon Mean Free Paths  

E-print Network

Size effects in heat conduction, which occur when phonon mean free paths (MFPs) are comparable to characteristic lengths, are being extensively explored in many nanoscale systems for energy applications. Knowledge of MFPs ...

Schmidt, A. J.

159

Filamentation of terawatts lasers pulses on 100m atmospheric path  

NASA Astrophysics Data System (ADS)

The experimental results of the filamentation terawatt femtosecond Ti:Sapphire-laser along an atmospheric path of 100- m length atmospheric path using different spatial focusing and pulse power. The high efficiency of controlling the position and length of the filamentation zone using various spatial focusing are presented. The dependences of the length and position of the filamentation of the initial degree of focus and pulse power, number of filaments along the filamentation zone is determined. The data are compared to the length of the field and the number of filaments filamentation with the results of our earlier experiments.

Apeksimov, D. V.; Burnashov, A. V.; Zemlyanov, A. A.; Iglakova, A. N.; Kabanov, A. M.; Kuchinskaya, O. I.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.

2014-11-01

160

Walden's Paths - Ensemble Edition  

NSDL National Science Digital Library

WaldenÂs 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. WaldenÂs 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

161

Robot path planning using a genetic algorithm  

NASA Technical Reports Server (NTRS)

Robot path planning can refer either to a mobile vehicle such as a Mars Rover, or to an end effector on an arm moving through a cluttered workspace. In both instances there may exist many solutions, some of which are better than others, either in terms of distance traversed, energy expended, or joint angle or reach capabilities. A path planning program has been developed based upon a genetic algorithm. This program assumes global knowledge of the terrain or workspace, and provides a family of good paths between the initial and final points. Initially, a set of valid random paths are constructed. Successive generations of valid paths are obtained using one of several possible reproduction strategies similar to those found in biological communities. A fitness function is defined to describe the goodness of the path, in this case including length, slope, and obstacle avoidance considerations. It was found that with some reproduction strategies, the average value of the fitness function improved for successive generations, and that by saving the best paths of each generation, one could quite rapidly obtain a collection of good candidate solutions.

Cleghorn, Timothy F.; Baffes, Paul T.; Wang, Liu

1988-01-01

162

Substrate and chain length dependencies of the thermal behavior of [CF3(CF2)m(CH2)nCOO]2Cd single monolayers investigated by infrared reflection absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Temperature-variable grazing incidence reflection absorption (GIR) spectra were recorded for the single monolayer of [CF3(CF2)m(CH2)nCOO)]2Cd [(m,n)=(7,10), (7,16), (7,22), (5,22), and (3,22)], transferred from aqueous Cd2+ subphase to gold- and aluminum-evaporated glass substrates. The spectra reveal that these monolayers have better thermal stability on Al substrates than on Au. An "interaction band" is identified at 1484˜1480 cm-1, due to the ?s(COO-) mode of carboxylate headgroups in ionic bonding with the Al surface. It is found that both the van der Waals interaction between the trans zig-zag hydrocarbon chains and the overlapping interaction between the fluorocarbon helixes are responsible for the systematic variation of the monolayer thermal behavior with (m,n). The thermal behavior of a single monolayer of cadmium stearate, serving as a model system, has been investigated to further confirm the spectral interpretation about the partially fluorinated monolayer. In addition, temperature-dependent friction measurements show that the single monolayers of (m,n)=(7,16), (7,22), (5,22), and (3,22) are potential molecular lubricants that can be used in the range of 25˜140 °C.

Ren, Yanzhi; Asanuma, Morito; Iimura, Ken-ichi; Kato, Teiji

2001-01-01

163

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

164

Pivoted document length normalization  

Microsoft Academic Search

Automatic information retrieval systems have to deal with documents of varying lengths in a text collection. Document length normalization is used to fairly retrieve documents of all lengths. In this study, we ohserve that a normalization scheme that retrieves documents of all lengths with similar chances as their likelihood of relevance will outperform another scheme which retrieves documents with chances

Amit Singhal; Chris Buckley; Manclar Mitra

1996-01-01

165

Characterization of soil organic matter composition at intact preferential flow path surfaces  

NASA Astrophysics Data System (ADS)

In structured soils, the interaction of percolating water and reactive solutes with the soil matrix is mostly restricted to surfaces of preferential flow paths. Surfaces of flow paths that are formed by cracks, decayed root channels or worm burrows are often covered by clay-organic coatings (i.e., cutanes), in which the outermost layer is mainly organic matter (OM). The composition of OM finally controls wettability, sorption, and transfer properties. However, the in-situ local distribution of OM properties along such surfaces is largely unknown to date because experimental techniques to study the relatively thin and vulnerable coatings at intact structure surfaces were not available. The objective of this study was to analyze the local mm-scale distribution and composition of SOM at preferential flow paths. The Fourier transformed infrared spectroscopy in diffuse reflectance mode (DRIFT) was used to determine spectral information of the intact structural surfaces (cracks and biopores). With the DRIFT-mapping technique, potential flow path types, such as earthworm burrows, root channels, and cracks of structured subsoil horizons were analyzed in 1 mm steps along transects of 15 up to 65 mm length. The distribution of OM composition was characterized by evaluating the ratios of the absorption band intensities of the alkyl- (C-H-) and carbonyl (C=O-) functional groups (CH/CO), which represent a measure of the potential wettability of the OM of the surface. Samples of different soil types (Luvisol, Regosol, Stagnosol, Cambisol), of different geological provenance (till, loess, mudstone, limestone), and of different land use (arable, forest) were analyzed. The CH/CO-ratio was generally higher for earthworm burrows and root channels as compared to crack surfaces and the soil matrix. Differences between flow path types could be observed with respect to soil type, parent material, and land use. The local distribution of the OM properties may affect sorption and mass transfer during preferential flow in structured soils.

Leue, M.; Gerke, H. H.; Ellerbrock, R. H.

2012-04-01

166

Tornado intensity estimated from damage path dimensions.  

PubMed

The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s(-1) for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width. PMID:25229242

Elsner, James B; Jagger, Thomas H; Elsner, Ian J

2014-01-01

167

Tornado Intensity Estimated from Damage Path Dimensions  

PubMed Central

The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s?1 for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width. PMID:25229242

Elsner, James B.; Jagger, Thomas H.; Elsner, Ian J.

2014-01-01

168

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

169

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

170

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

171

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

NASA Astrophysics Data System (ADS)

Two measuring methods of wide absorption spectrum by DFB-LDs are presented in detecting water vapor absorption line. One is subsection scanning method, it takes advantage of wide spectrum tuning range by 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 corresponding to specific temperature of DFB-LD, and scanning every section by current modulation for hundreds times and average the data to raise SNR, 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 absorption line-shape function, the absorption line can be described by fitting with partial measured data. The fitting absorption line is fitted well with the measured data, and the square of correlation coefficient (R-square) is 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.

2013-09-01

172

H216O absorption spectrum between 22250 and 22800 cm-1: Fourier transform spectroscopy with bright light source  

NASA Astrophysics Data System (ADS)

Measurements of water vapor absorption spectra in the visible spectral region near 0.44 mkm are performed using FTspectrometer IFS-125M and Light-emitting diode (LED) as source of radiation. Water vapor spectrum has been obtained by averaging over 17136 scans recorded at 34,8 m optical path length, temperature 24 ± 1 C and pressure of sample 24,8 mBar. Due to strong emission of LED source it was possible to achieve signal-to-noise ratio about 104 and to record weak lines with intensities of 6 10-27 cm/molecule. Comparisons with results of early works are made.

Serduykov, V. I.; Sinitsa, L. N.; Vasil'chenko, S. S.; Bykov, A. D.; Kruglova, T. V.; Polovtseva, E. R.; Scherbakov, A. P.

2014-11-01

173

Backscattering measurements of atmospheric aerosols at CO2 laser wavelengths: implications of aerosol spectral structure on differential-absorption lidar retrievals of molecular species.  

PubMed

The volume backscattering coefficients of atmospheric aerosol were measured with a tunable CO2 lidar system at various wavelengths in Utah (a desert environment) along a horizontal path a few meters above the ground. In deducing the aerosol backscattering, a deconvolution (to remove the smearing effect of the long CO2 lidar pulse and the lidar limited bandwidth) and a constrained-slope method were employed. The spectral shape beta(lambda) was similar for all the 13 measurements during a 3-day period. A mean aerosol backscattering-wavelength dependence beta(lambda) was computed from the measurements and used to estimate the error Delta(CL) (concentration-path-length product) in differential-absorption lidar measurements for various gases caused by the systematic aerosol differential backscattering and the error that is due to fluctuations in the aerosol backscattering. The water-vapor concentration-path-length product CL and the average concentration C = /L for a path length L computed from the range-resolved lidar measurements is consistently in good agreement with the water-vapor concentration measured by a meteorological station. However, I was unable to deduce, reliably, the range-resolved water-vapor concentration C(r), which is the derivative of the range-dependent product CL, because of the effect of residual noise caused mainly by errors in the deconvolved lidar measurements. PMID:18319835

Ben-David, A

1999-04-20

174

Length Conversions and Length-Weight Relations for Pallid Sturgeon  

Microsoft Academic Search

We developed conversion formulas for standard length to fork length, fork length to total length, and standard length to total length for 30 pallid sturgeons Scaphirhynchus albus from the upper Missouri River. Formulas for converting length to weight were also developed for each of the length measurements. We add our length and weight data on 30 specimens of this rare

K. D. Keenlyne; S. J. Maxwell

1993-01-01

175

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.

Christian, Wolfgang; Belloni, Mario

2006-01-19

176

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.

University, Australian N.

177

On brittle fracture paths  

Microsoft Academic Search

Two classes of fracture are defined: I — fracture path completely predictable, and II — fracture path predictable only after initial random propagation. Class I fractures occur when there is a line of principal stress passing through the tip of the initiating notch or slit across which the stress is a maximum away from the tip. All Class II fractures

B. Cotterell

1965-01-01

178

Multiphoton absorption cross section and virtual-state spectroscopy for the entangled n-photon state  

E-print Network

Multiphoton absorption cross section and virtual-state spectroscopy for the entangled n-photon absorption cross sections are also obtained. The absorption cross sections exhibit a linear dependence states involved in the interaction from the absorption cross section measured as a function of path delay

Teich, Malvin C.

179

Path integration in insects.  

PubMed

The most notable advance in our knowledge of path integration in insects is a new understanding of how the honeybee measures the distance that it travels during its foraging trips. Data from two groups show that the bee's odometer records distance in terms of the net amount of image motion over the retina that is accumulated during a flight. Progress has also been made in clarifying the relation between path integration and other navigational strategies. On unfamiliar ground, path integration is the only available means of navigation. In familiar surroundings, however, guidance by landmarks may override guidance by path integration. Path integration then becomes a back-up strategy that is used primarily when landmarks fail. PMID:11240286

Collett, T S; Collett, M

2000-12-01

180

Fracturing the optimal paths.  

PubMed

Optimal paths play a fundamental role in numerous physical applications ranging from random polymers to brittle fracture, from the flow through porous media to information propagation. Here for the first time we explore the path that is activated once this optimal path fails and what happens when this new path also fails and so on, until the system is completely disconnected. In fact many applications can also be found for this novel fracture problem. In the limit of strong disorder, our results show that all the cracks are located on a single self-similar connected line of fractal dimension D(b) approximately = 1.22. For weak disorder, the number of cracks spreads all over the entire network before global connectivity is lost. Strikingly, the disconnecting path (backbone) is, however, completely independent on the disorder. PMID:20366106

Andrade, J S; Oliveira, E A; Moreira, A A; Herrmann, H J

2009-11-27

181

Optical absorption of pure water in the blue and ultraviolet  

E-print Network

The key feature of the Integrating Cavity Absorption Meter (ICAM) is that it produces an isotropic illumination of the liquid sample and thereby dramatically minimizes scattering effects. The ICAM can produce an effective optical path...

Lu, Zheng

2007-09-17

182

Design of a partially compliant crank rocker mechanism using Ionic Polymer Metal Composite for path generation  

Microsoft Academic Search

Four-bar mechanisms traditionally are made of rigid links and they are used for path, motion or function generation. Actively changing the length of the rocker in a crank rocker four-bar mechanism results in the tip of the rocker following a closed path. In this paper a crank rocker mechanism has been designed with a variable length rocker using an Ionic

Biswanath Panda; Ashish Dutta

2010-01-01

183

Topological analysis of polymeric melts: Chain-length effects and fast-converging estimators for entanglement length  

NASA Astrophysics Data System (ADS)

Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length Ne which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive, and test new estimators which eliminate these systematic errors using information obtainable from the variation in entanglement characteristics with chain length. The new estimators produce accurate results for Ne from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.

Hoy, Robert S.; Foteinopoulou, Katerina; Kröger, Martin

2009-09-01

184

Homotopy and Path Integrals  

E-print Network

This is an introductory review of the connection between homotopy theory and path integrals, mainly focus on works done by Schulman [23] that he compared path integral on SO(3) and its universal covering space SU(2), DeWitt and Laidlaw [15] that they proved the theorem to the case of path integrals on the multiply-connected topological spaces. Also, we discuss the application of the theorem in Aharonov-Bohm effect given by [20,24]. An informal introduction to homotopy theory is provided for readers who are not familiar with the theory.

Fumika Suzuki

2011-08-31

185

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

186

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.

187

Restoration by Path Concatenation: Fast Recovery of MPLS Paths  

E-print Network

Restoration by Path Concatenation: Fast Recovery of MPLS Paths Yehuda Afek Anat Bremler-Barr Haim,natali,haimk}@math.tau.ac.il, {edith,mischu}@research.att.com Abstract A new general theory about restoration of network paths is first introduced. The theory pertains to restoration of shortest paths in a network following failure, e.g., we

Kaplan, Haim

188

Restoration by Path Concatenation: Fast Recovery of MPLS Paths  

E-print Network

Restoration by Path Concatenation: Fast Recovery of MPLS Paths Yehuda Afek Anat Bremler,natali,haimkg@math.tau.ac.il, fedith,mischug@research.att.com Abstract A new general theory about restoration of network paths is first introduced. The theory pertains to restoration of shortest paths in a network following failure, e.g., we

Bremler-Barr, Anat

189

Circumference and Arc Length  

NSDL National Science Digital Library

This unit will introduce you to circumference of a circle, and how to find the measurement of the edge of a piece of pizza! (Arc length!) Ok. Let's make sure you remember circumference of a circle, you know, the distance around a circle? Click on the following link and take notes! Circle Circumference Now we can use that to find the arc length, or the length of the crust part of the edge of a pizza! Take notes: Arcs in Circles Now, let's ...

Neubert, Mrs.

2011-03-24

190

[Study of remote sensing the flux of carbon dioxide gas with tunable diode laser absorption spectroscopy].  

PubMed

Tunable diode laser absorption spectroscopy (TDLAS) technique is a new method to detect trace gas qualitatively or quantificationally based on the scan characteristic of the diode laser to obtain the absorption spectra in the characteristic absorption region. TDLAS is a highly sensitive, highly selective and fast time response trace gas detection technique. In the present paper, a DFB laser at room temperature was used as the light source, wavelength modulation method was employed, and the second harmonic signal of one absorption line near 1.578 microm of carbon dioxide molecule was measured. A system was built for online monitoring of carbon dioxide concentration within the optical path of more than 700 meters at different heights. Combined with Alonzo Mourning-Obukhov length and characteristic velocity detected by large aperture scintillometer, the flux of carbon dioxide gas calculated by the experiential formula is within -60-60 mg x m(-2) x s(-1). The comparison of the datea detected by TDLAS system and the eddy covariance showed that the change of the data detected by TDLAS had a similar trend to that detected by the eddy covariance, and the best results can be produced by this method, breaking through the phenomenon of only providing the flux of trace gases near the ground at present, and making the measurement of trace gas fluxes within a large area possible. PMID:21595244

Song, Xue-mei; Liu, Jian-guo; Zhang, Yu-jun; Lu, Yi-huai; Zeng, Zong-yong; He, Ying; Cui, Yi-ben; Tian, Yong-zhi; Tian, Lin

2011-03-01

191

Open multipass absorption cell for in situ monitoring of stratospheric trace gas with telecommunication laser diodes.  

PubMed

A two-mirror multipass absorption cell that is operated open to the atmosphere from a stratospheric balloon to monitor in situ methane (in the 1.65-microm region) and water vapor (in the 1.39-microm region) with telecommunication laser diodes is described. A small Cassegrain-type telescope is used to couple the cell simultaneously with two near-infrared InGaAsP laser diodes by means of optical fibers. The 1-m cell provides an absorption path length of 56 m. The optical cell was carefully designed to be free of incidental fringing in the 10(-5) absorption range. It is used in combination with a dual-beam detector to obtain a detection limit of 10(-5) absorption units, a large dynamic range of the measurements of many orders of magnitude, and a precision error in the concentration determination of a few percents. The optical arrangement of the cell and its ability to be used to detect in situ trace gas in the stratosphere, in severe environmental conditions, are exposed. PMID:11905566

Durry, Georges; Danguy, Théodore; Pouchet, Ivan

2002-01-20

192

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

193

Very high finesse optical-feedback cavity-enhanced absorption spectrometer for low concentration water vapor isotope analyses.  

PubMed

So far, cavity-enhanced absorption spectroscopy (CEAS) has been based on optical cavities with a high finesse F that, however, has been limited by mirror reflectivity and by cavity transmission considerations to a few times 10,000. Here, we demonstrate a compact near-infrared optical-feedback CEAS instrument for water vapor isotope ratio measurements, with F>140,000. We show that this very high finesse can be effectively exploited to improve the detection sensitivity to the full extent predicted by the increased effective path length to reach a noise equivalent absorption sensitivity of 5.7×10(-11)??cm(-1)?Hz(-1/2) for a full spectrum registration (including possible effects of interference fringes and fit model inadequacies). PMID:24686607

Landsberg, J; Romanini, D; Kerstel, E

2014-04-01

194

Simulation of short-path high-precision industrial gas sensors using DFB diode lasers and Fourier transform absorbance ratio analysis and control methods  

NASA Astrophysics Data System (ADS)

Precision industrial gas sensor which operate at room temperature and pressures in the 100-1000 mbar range are simulated by using the characteristics of DFB GaAs/Sb based tunable diode lasers operating in the 1-5 micrometers band within a simple optical bench having an absorption path length of 1-5 cm and by using the Fourier transform absorbance ratio digital analysis and control methods to achieve resolutions in the sub ppmv range for gas mixtures. The direct detection absorption spectroscopy theory, methods and sensor structure are reviewed and newly developed analysis and control noise models are presented. Absolute precision in terms of gain accuracy and resolution relationships is presented for these methods. Simulation methods for the error terms are also presented. Digital simulation results on rejection of noise, fringes, laser power function and interference lines for H2O and CO2 sensor at selected wave numbers are presented.

Kidd, Gary E.

1999-12-01

195

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

196

A path planning method for human tracking agents using variable-term prediction based on dynamic k-nearest neighbor algorithm  

Microsoft Academic Search

This paper deals with a multi-agent path plan- ning problem for tracking humans in order to obtain detail information such like human behavior and characteristics. To achieve this, paths of agents are planned based on similarity between the predicted positions of humans and agents' field of views, and the path length in the path planning is determined according to the

Noriko Takemura; Yutaka Nakamura; Hiroshi Ishiguro

2011-01-01

197

Experimental determination of conjugation lengths in long polyene chains  

NASA Astrophysics Data System (ADS)

Since the low energy absorption spectrum of a linear polyene is dominated by the strongly allowed 1 1Ag?1 1Bu transition (S0 to S2), it can be reconstructed for any chain length if the 0-0 band excitation energy, the band profile, and intensity are known. From this premise, this paper uses information developed in high resolution experiments on well-defined linear polyenes to extract the distribution of effective conjugation lengths from absorption spectra of solutions of long linear polyenes. These distributions are found to be dominated by short conjugation lengths.

Kohler, Bryan E.; Samuel, I. D. W.

1995-10-01

198

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

199

A fuzzy shortest path with the highest reliability  

NASA Astrophysics Data System (ADS)

This paper concentrates on a shortest path problem on a network where arc lengths (costs) are not deterministic numbers, but imprecise ones. Here, costs of the shortest path problem are fuzzy intervals with increasing membership functions, whereas the membership function of the total cost of the shortest path is a fuzzy interval with a decreasing linear membership function. By the max-min criterion suggested in [R.E. Bellman, L.A. Zade, Decision-making in a fuzzy environment, Management Science 17B (1970) 141-164], the fuzzy shortest path problem can be treated as a mixed integer nonlinear programming problem. We show that this problem can be simplified into a bi-level programming problem that is very solvable. Here, we propose an efficient algorithm, based on the parametric shortest path problem for solving the bi-level programming problem. An illustrative example is given to demonstrate our proposed algorithm.

Keshavarz, Esmaile; Khorram, Esmaile

2009-08-01

200

OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM  

EPA Science Inventory

A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging fr...

201

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

202

An Unplanned Path  

ERIC Educational Resources Information Center

The authors elucidate what they saw as three important challenges to overcome along the path to becoming elementary school mathematics teacher leaders: marginal interest in math, low self-confidence, and teaching in isolation. To illustrate how these challenges were mitigated, they focus on the stories of two elementary school teachers--Laura and…

McGarvey, Lynn M.; Sterenberg, Gladys Y.; Long, Julie S.

2013-01-01

203

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

204

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

205

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

206

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

207

MASERATI: a RocketBorne tunable diode laser absorption spectrometer.  

PubMed

The MASERATI (middle-atmosphere spectrometric experiment on rockets for analysis of trace-gas influences) instrument is, to our knowledge, the first rocket-borne tunable diode laser absorption spectrometer that was developed for in situ measurements of trace gases in the middle atmosphere. Infrared absorption spectroscopy with lead salt diode lasers is applied to measure water vapor and carbon dioxide in the altitude range from 50 to 90 km and 120 km, respectively. The laser beams are directed into an open multiple-pass absorption setup (total path length 31.7 m) that is mounted on top of a sounding rocket and that is directly exposed to ambient air. The two species are sampled alternately with a sampling time of 7.37 ms, each corresponding to an altitude resolution of approximately 15 m. Frequency-modulation and lock-in techniques are used to achieve high sensitivity. Tests in the laboratory have shown that the instrument is capable of detecting a very small relative absorbance of 10(-4)-10(-5) when integrating spectra for 1 s. The instrument is designed and qualified to resist the mechanical stress occurring during the start of a sounding rocket and to be operational during the cruising phase of the flight when accelerations are very small. Two almost identical versions of the MASERATI instrument were built and were launched on sounding rockets from the Andøya Rocket Range (69 degrees N) in northern Norway on 12 October 1997 and on 31 January 1998. The good technical performance of the instruments during these flights has demonstrated that MASERATI is indeed a new suitable tool to perform rocket-borne in situ measurements in the upper atmosphere. PMID:18324036

Lübken, F J; Dingler, F; von Lucke, H; Anders, J; Riedel, W J; Wolf, H

1999-09-01

208

The application of differential optical absorption spectroscopy (DOAS) from space  

NASA Astrophysics Data System (ADS)

Trace gas measurements by absorptions spectroscopy make use of the attenuation of radiation by molecules. The central idea of Differential Optical Absorption Spectroscopy (DOAS) is to analyse strongly structured (fingerprint) absorptions of visible, UV, or near IR radiation by atmospheric trace gases. In contrast to traditional spectroscopic methods relying on measuring the attenuation of the radiation intensity at a few, selected wavelengths (typically pairs of `on line' and `off line' wavelengths) only, DOAS typically uses intensity measurements at hundreds or even thousands of wavelengths. The strength of DOAS lies in the excellent specificity, inherent calibration, the potential for real time measurements, and its remote sensing capabilities. Since its introduction in the late 1970's by Platt and Perner significant advances have been made in the DOAS technique, including the development of reliable evaluation techniques based and new methods allowing a realistic estimate of the resulting errors, also techniques to compensate for instrumental effects, like residual spectra, were developed. Most importantly the range of application of DOAS was greatly enhanced to include observations using scattered sunlight, multi axis observ ation (MAX-DOAS), vertical trace gas -concentration profiles, and measurements from satellites (e.g. the GOME, SCIAMACHY, GOME-2, and OMI instruments). At the same time the palette of species measurable by DOAS was expanded from the original SO2, NO2, CH2O, and O3 to include many free radicals (e.g. OH, NO3, IO, OIO, BrO, ClO, OClO), nitrous acid (HONO), and a large set of aromatic compounds (e.g. benzene, toluene, xylenes, phenols, benzaldehyde). In addition it is now possible to determine the photon path-length distribution in clouds by ground based observation of O2 and O4 bands. Here the new approaches, specific requirements and sample applications for space- borne DOAS instruments are described. Recent advances and directions of future development are dis c u s s e d .

Platt, U.

209

Shorter Path Constraints for the Resource Constrained Shortest Path Problem  

Microsoft Academic Search

Recently, new cost-based filtering algorithms for shorter-path con- straints have been developed. However, so far only the theoretical properties of shorter-path constraint filtering have been studied. We provide the first extensive experimental evaluation of the new algorithms in the context of the resource con- strained shortest path problem. We show how reasoning about path-substructures in combination with CP-based Lagrangian relaxation

Thorsten Gellermann; Meinolf Sellmann; Robert Wright

2005-01-01

210

Path-finding in real and simulated rats: assessing the influence of path characteristics on navigation learning.  

PubMed

A large body of experimental evidence suggests that the hippocampal place field system is involved in reward based navigation learning in rodents. Reinforcement learning (RL) mechanisms have been used to model this, associating the state space in an RL-algorithm to the place-field map in a rat. The convergence properties of RL-algorithms are affected by the exploration patterns of the learner. Therefore, we first analyzed the path characteristics of freely exploring rats in a test arena. We found that straight path segments with mean length 23 cm up to a maximal length of 80 cm take up a significant proportion of the total paths. Thus, rat paths are biased as compared to random exploration. Next we designed a RL system that reproduces these specific path characteristics. Our model arena is covered by overlapping, probabilistically firing place fields (PF) of realistic size and coverage. Because convergence of RL-algorithms is also influenced by the state space characteristics, different PF-sizes and densities, leading to a different degree of overlap, were also investigated. The model rat learns finding a reward opposite to its starting point. We observed that the combination of biased straight exploration, overlapping coverage and probabilistic firing will strongly impair the convergence of learning. When the degree of randomness in the exploration is increased, convergence improves, but the distribution of straight path segments becomes unrealistic and paths become 'wiggly'. To mend this situation without affecting the path characteristic two additional mechanisms are implemented: a gradual drop of the learned weights (weight decay) and path length limitation, which prevents learning if the reward is not found after some expected time. Both mechanisms limit the memory of the system and thereby counteract effects of getting trapped on a wrong path. When using these strategies individually divergent cases get substantially reduced and for some parameter settings no divergence was found anymore at all. Using weight decay and path length limitation at the same time, convergence is not much improved but instead time to convergence increases as the memory limiting effect is getting too strong. The degree of improvement relies also on the size and degree of overlap (coverage density) in the place field system. The used combination of these two parameters leads to a trade-off between convergence and speed to convergence. Thus, this study suggests that the role of the PF-system in navigation learning cannot be considered independently from the animals' exploration pattern. PMID:18446432

Tamosiunaite, Minija; Ainge, James; Kulvicius, Tomas; Porr, Bernd; Dudchenko, Paul; Wörgötter, Florentin

2008-12-01

211

SOCIAL PATH FOLLOWING Carmine Oliva  

E-print Network

of path following; each agent is now able to avoid static and dynamic obstacles along its path, to predict a specific profile for each agent, our system can also show how different stereotypes of people act in those

Karlsson, Brynjar

212

Helmholtz Path Integrals  

NASA Astrophysics Data System (ADS)

The multidimensional, scalar Helmholtz equation of mathematical physics is addressed. Rather than pursuing traditional approaches for the representation and computation of the fundamental solution, path integral representations, originating in quantum physics, are considered. Constructions focusing on the global, two-way nature of the Helmholtz equation, such as the Feynman/Fradkin, Feynman/Garrod, and Feynman/DeWitt-Morette representations, are reviewed, in addition to the complementary phase space constructions based on the exact, well-posed, one-way reformulation of the Helmholtz equation. Exact, Feynman/Kac, stochastic representations are also briefly addressed. These complementary path integral approaches provide an effective means of highlighting the underlying physics in the solution representation, and, subsequently, exploiting this more transparent structure in natural computational algorithms.

Fishman, Louis

2006-05-01

213

Lander flight path analysis  

NASA Technical Reports Server (NTRS)

The primary functions of the Lander Flight Path Analysis Team (LFPAT) were to (1) design the Viking Lander (VL) descent trajectory and compute the descent guidance parameters for command transmission to the Viking Lander and Viking Orbiter (VO), (2) reconstruct the VL trajectory from separation to touchdown using data transmitted from the VL to Earth via the VO during descent, and (3) predict the VL/VO relay link system performance during descent and post touchdown. The preflight VL capability, the history of proposed descent trajectory designs as the site selection process evolved, and the final trajectory design and guidance parameters for each vehicle are addressed along with the trajectory reconstruction process, including the overall reconstructed VL flight path summary and a detailed discussion of the entry trajectory and atmosphere reconstruction results. The postland relay link prediction function is discussed.

Euler, E. A.; Adams, G. L.; Hopper, F. W.

1979-01-01

214

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

215

Path Integrals in Quantum Mechanics  

Microsoft Academic Search

Jean Zinn-Justin's textbook Path Integrals in Quantum Mechanics aims to familiarize the reader with the path integral as a calculational tool in quantum mechanics and field theory. The emphasis is on quantum statistical mechanics, starting with the partition function Tr exp(-? H) and proceeding through the diffusion equation to barrier penetration problems and their semiclassical limit. The 'real time' path

J Louko

2005-01-01

216

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

217

[On using tunable diode laser absorption spectroscopy to determine gas fluxes over cropland].  

PubMed

Tunable diode laser absorption spectroscopy (TDLAS) is a compact, automated, high precision technique and fit for in-situ or field measurements. Two spectroscopy measurement systems, TDLAS and NDIR (non-dispersive infrared spectroscopy), were used to monitor trace gas emission over cropland at Fengqiu Agricultural Ecology Experimental Station for one month. The fluxes of carbon dioxide were estimated by flux-gradient and eddy covariance method, respectively. A footprint model was developed during experiment. Based on this model, the source areas of TDLAS and NDIR were investigated. The effects of different factors on the flux measurement were also analyzed. The authors concluded that the source areas for the two techniques are discrepant in most of the cases. The source areas increase with path length and detecting height. This result will help the installation of instruments. PMID:22715787

Tian, Yong-zhi; Liu, Jian-guo; Zhang, Yu-jun; Lu, Yi-huai; He, Ying

2012-04-01

218

Path Planning on a Compressed Terrain Daniel M. Tracy  

E-print Network

-planning algorithm simulates a smugglers and border guards scenario. First, we place observers on a ter- rain so- tection by an observer, path length, and uphill movement. The smuggler is allowed the full range of inter-elevation point terrain visibility is essential for surveying, cell phone tower place- ment

Varela, Carlos

219

Hausdorff dimension of a particle path in a quantum manifold  

NASA Astrophysics Data System (ADS)

After recalling the concept of the Hausdorff dimension, we study the fractal properties of a quantum particle path. As a novelty we consider the possibility for the space where the particle propagates to be endowed with a quantum-gravity-induced minimal length. We show that the Hausdorff dimension accounts for both the quantum mechanics uncertainty and manifold fluctuations. In addition the presence of a minimal length breaks the self-similarity property of the erratic path of the quantum particle. Finally we establish a universal property of the Hausdorff dimension as well as the spectral dimension: They both depend on the amount of resolution loss which affects both the path and the manifold when quantum gravity fluctuations occur.

Nicolini, Piero; Niedner, Benjamin

2011-01-01

220

Scanning path optimization for ultrasound surgery  

NASA Astrophysics Data System (ADS)

One of the problems in ultrasound surgery is the long treatment times when large tumour volumes are sonicated. Large tumours are usually treated by scanning the tumour volume using a sequence of individual focus points. During the scanning, it is possible that surrounding healthy tissue suffers from undesired temperature rise. The selection of the scanning path so that the tumour volume is treated as fast as possible while temperature rise in healthy tissue is minimized would increase the efficiency of ultrasound surgery. The main purpose of this paper is to develop a computationally efficient method which optimizes the scanning path. The optimization algorithm is based on the minimum time formulation of the optimal control theory. The developed algorithm uses quadratic cost criteria to obtain the desired thermal dose in the tumour region. The derived method is evaluated with numerical simulations in 3D which are applied to ultrasound surgery of the breast in simplified geometry. Results from the simulations show that the treatment time as well as the total applied energy can be decreased from 16% to 43% as compared to standard sonication. The robustness of the optimized scanning path is studied by varying the perfusion and absorption in the tumour region.

Malinen, Matti; Huttunen, Tomi; Kaipio, Jari P.; Hynynen, Kullervo

2005-08-01

221

Efficient optical path folding by using multiple total internal reflections in a microcavity  

E-print Network

We propose using an asymmetric resonant microcavity for the efficient generation of an optical path that is much longer than the diameter of the cavity. The path is formed along a star polygonal periodic orbit within the cavity, which is stable and confined by total internal reflection. We fabricated a semiconductor device based on this idea with an average diameter of 0.3 mm, and achieved a path length of 2.79 mm experimentally.

Shinohara, Susumu; Fukushima, Takehiro; Harayama, Takahisa; Arai, Kenichi; Yoshimura, Kazuyuki

2014-01-01

222

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.

2010-01-01

223

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.

Lessonplans, Utah

2012-09-18

224

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

225

Accurate Liquid Water Path Retrieval from Low-Cost Microwave Radiometers Using Additional Information from a Lidar Ceilometer and Operational Forecast Models  

E-print Network

radiometers to derive both liquid water path (LWP) and water vapor path (WVP) is well established, but uncertainties over the dry, water vapor, and liquid water absorption coef- ficients and the radiometricAccurate Liquid Water Path Retrieval from Low-Cost Microwave Radiometers Using Additional

Hogan, Robin

226

OSCILLATING FRACTURE PATHS IN THIN BRITTLE SHEETS: WHEN GEOMETRY RULES CRACK PROPAGATION  

E-print Network

OSCILLATING FRACTURE PATHS IN THIN BRITTLE SHEETS: WHEN GEOMETRY RULES CRACK PROPAGATION B.AUDOLY1 crack propagation when a cutting tip of moderately large width is driven through a thin brittle polymer crack paths scale linearly with the width of the cutting tip over a wide range of length scales

Reis, Pedro Miguel

227

Ab-initio path integral techniques for molecules  

E-print Network

Path integral Monte Carlo with Green's function analysis allows the sampling of quantum mechanical properties of molecules at finite temperature. While a high-precision computation of the energy of the Born-Oppenheimer surface from path integral Monte Carlo is quite costly, we can extract many properties without explicitly calculating the electronic energies. We demonstrate how physically relevant quantities, such as bond-length, vibrational spectra, and polarizabilities of molecules may be sampled directly from the path integral simulation using Matsubura (temperature) Green's functions (imaginary-time correlation functions). These calculations on the hydrogen molecule are a proof-of-concept, designed to motivate new work on fixed-node path-integral calculations for molecules.

Daejin Shin; Ming-Chak Ho; J. Shumway

2006-11-09

228

Ab-initio path integral techniques for molecules  

E-print Network

Path integral Monte Carlo with Green's function analysis allows the sampling of quantum mechanical properties of molecules at finite temperature. While a high-precision computation of the energy of the Born-Oppenheimer surface from path integral Monte Carlo is quite costly, we can extract many properties without explicitly calculating the electronic energies. We demonstrate how physically relevant quantities, such as bond-length, vibrational spectra, and polarizabilities of molecules may be sampled directly from the path integral simulation using Matsubura (temperature) Green's functions (imaginary-time correlation functions). These calculations on the hydrogen molecule are a proof-of-concept, designed to motivate new work on fixed-node path-integral calculations for molecules.

Shin, D; Shumway, J; Ho, Ming-Chak; Shin, Daejin

2006-01-01

229

Design of a simple cryogenic system for ultraviolet-visible absorption spectroscopy with a back-reflectance fiber optic probe.  

PubMed

We report a convenient and inexpensive technique for the rapid acquisition of absorption spectra from small samples at cryogenic temperatures using a home built cryostat with novel collection optics. A cylindrical copper block was constructed with a coaxial bore to hold a 4.00 mm diameter electron paramagnetic resonance (EPR) tube and mounted on a copper feed in thermal contact with liquid nitrogen. A 6.35 mm diameter hole was bored into the side of the cylinder so a fiber optic cable bundle could be positioned orthogonally to the EPR tube. The light passing through the sample is reflected off of the opposing surfaces of the EPR tube and surrounding copper, back through the sample. The emergent light is then collected using the fiber optic bundle and analyzed using a dispersive spectrometer. Absorption spectra for KMnO4 were measured between 400 and 700 nm. Absorption intensity at 506, 525, 545, and 567 nm was found to be proportional to concentration, displaying Beer's law-like behavior. The EPR tube had an internal diameter of 3.2 mm; the double pass of the probe beam through the sample affords a central path length of about 6.4 mm. Comparing these measurements with those recorded on a conventional tabletop spectrometer using a cuvette with a 10.00 mm path length, we consistently found a ratio between intensities of 0.58 rather than the anticipated 0.64. These 6% smaller values we attribute to the curvature of the EPR tube and transmission/reflection losses. This system is particularly well-suited to studying the kinetics and dynamics of chemical reactions at cryogenic temperatures. The rapid response (100 ms) and multiplex advantage provided the opportunity of recording simultaneous time courses at several wavelengths following initiation of a chemical reaction with a pulsed laser source. PMID:24405962

Vinyard, Andrew; Hansen, Kaj A; Byrd, Ross; Stuart, Douglas A; Hansen, John E

2014-01-01

230

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

231

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

232

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 â 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

233

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.

1997-01-01

234

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

235

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

236

Acetylene weak bands at 2.5 $?$m from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy  

E-print Network

The spectral dynamics of a mid-infrared multimode Cr^2+:ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C_2H_2 in natural isotopic abundance are recorded around 4000 cm^-1 with kilometric absorption path lengths and sensitivities better than 3 10^-8 cm-1. Two cold bands are newly identified and assigned to the n_1+n_4^1 and n_3+n_5^1 transitions of ^12C^13CH_2. The n_1+n_5^1 band of ^12C_2HD and fourteen ^12C_2H_2 bands are observed, among which for the first time n_2+2n_4^2+n_5^-1.

Véronique Girard; Robert Farrenq; Evgeni Sorokin; Irina T. Sorokina; Guy Guelachvili; Nathalie Picqué

2006-12-01

237

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

NASA Technical Reports Server (NTRS)

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 results are presented in tables and graphs. It is found that the adiabatic energy of the 1A2 state lies 9990 + or - 70/cm (1.24 + or - 0.01 eV) above the electronic ground state, close to the O + O2 dissociation limit. The applicability of the present results to studies of O3 in the upper atmosphere is indicated.

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

1990-01-01

238

CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5-4 ?m range TEC mercury-cadmium-telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm-1, a 1 ? minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

Krzempek, Karol; Jahjah, Mohammad; Lewicki, Rafa?; Stefa?ski, Przemys?aw; So, Stephen; Thomazy, David; Tittel, Frank K.

2013-09-01

239

CW DFB RT diode laser based sensor for trace-gas detection of ethane using novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable laser diode absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS) as the detection technique. TDLAS was performed with an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm. For an interference free C2H6 absorption line located at 2976.8 cm-1 a 1? minimum detection limit of 130 pptv with a 1 second lock-in amplifier time constant was achieved.

Jahjah, Mohammad; Lewicki, Rafal; Tittel, Frank K.; Krzempek, Karol; Stefanski, Przemyslaw; So, Stephen; Thomazy, David

2013-01-01

240

Telomere length in reproduction.  

PubMed

Telomeres, noncoding hexameric tandem repeats located at the ends of chromosomes, maintain chromosome stability and genome integrity. These guanine-rich repeats are highly conserved during evolution, and their role is dependent on their length and structure. They have multiple functions, including regulating the reproductive lifespan by mediating synapsis and homologous recombination of the chromosomes. Short telomeres result in meiotic arrest, segregation abnormalities and dysjunction, which lead to an increased incidence of aneuploid germ cells. In addition, shortened telomeres in men result in apoptosis of germ cells, whereas, in women, they result in meiotic arrest. In somatic cells, telomere shortening occurs at each consecutive round of replication, which induces senescence in vitro and in vivo. However there is a 2-fold elongation of telomeres during spermatogenesis. Spermatozoa, are terminally differentiated cells, have longer telomeres than spermatogonia and pachytene spermatocytes. In addition to genetic factors, lifestyle factors and psychological stress also play crucial role in modulating telomere length. Because not much is known about its role in reproduction, we focused this review on the function, structure and length dynamics of the telomere in the reproductive process. PMID:22928904

Thilagavathi, J; Venkatesh, S; Dada, R

2013-10-01

241

Planck-Length Phenomenology  

E-print Network

This author's recent proposal of interferometric tests of Planck-scale-related properties of space-time is here revisited from a strictly phenomenological viewpoint. The results announced previously are rederived using elementary dimensional considerations. The dimensional analysis is then extended to the other two classes of experiments (observations of neutral kaons at particle accelerators and observations of the gamma rays we detect from distant astrophysical sources) which have been recently considered as opportunities to explore "foamy" properties of space-time. The emerging picture suggests that there is an objective and intuitive way to connect the sensitivities of these three experiments with the Planck length. While in previous studies the emphasis was always on some quantum-gravity scenario and the analysis was always primarily aimed at showing that the chosen scenario would leave a trace in a certain class of doable experiments, the analysis here reported takes as starting point the experiments and, by relating in a direct quantitative way the sensitivities to the Planck length, provides a model-independent description of the status of Planck-length phenomenology.

Giovanni Amelino-Camelia

2000-08-04

242

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.

Johnson, Jennifer

243

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

244

Coherence length of cosmic background radiation enlarges the attenuation length of the ultra-high energy proton  

E-print Network

It is pointed out that an agreement of the one particle energy spectrum of the cosmic background radiation (CMBR) with Plank distribution of 2.725 [K] does not give a strong constraint on the coherence length of CMBR if the mean free path of CMBR is very long. The coherence length in this situation is estimated as a few times of $k_BT$. Due to this finite coherence length, the attenuation length of ultra-high energy cosmic rays (UHECR) is reduced in the $\\Delta $ resonance region,i.e., around $10^{20}$ [eV]. The small attenuation length makes the suppression of the flux of cosmic rays in this energy region less prominent than the naive estimation

Kenzo Ishikawa; Yutaka Tobita

2010-03-09

245

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

246

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

247

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

248

Lengths on rotating platforms  

NASA Astrophysics Data System (ADS)

The paper treats the issue of the length of a rotating circumference as seen from on board the moving disk and from an inertial reference frame. It is shown that, properly defining a measuring process, the result is in both cases 2?R thus dissolving the Ehrenfest paradox. The same holds good when considering that, for the rotating observer, the perceived radius coincides with the curvature radius of a space-time helix and a complete round trip corresponds to an angle which differs from the one seen by the inertial observer. The apparent contradiction with the Lorentz contraction is discussed.

Tartaglia, A.

1999-02-01

249

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.

250

Integration across Time Determines Path Deviation Discrimination for Moving Objects  

PubMed Central

Background Human vision is vital in determining our interaction with the outside world. In this study we characterize our ability to judge changes in the direction of motion of objects–a common task which can allow us either to intercept moving objects, or else avoid them if they pose a threat. Methodology/Principal Findings Observers were presented with objects which moved across a computer monitor on a linear path until the midline, at which point they changed their direction of motion, and observers were required to judge the direction of change. In keeping with the variety of objects we encounter in the real world, we varied characteristics of the moving stimuli such as velocity, extent of motion path and the object size. Furthermore, we compared performance for moving objects with the ability of observers to detect a deviation in a line which formed the static trace of the motion path, since it has been suggested that a form of static memory trace may form the basis for these types of judgment. The static line judgments were well described by a ‘scale invariant’ model in which any two stimuli which possess the same two-dimensional geometry (length/width) result in the same level of performance. Performance for the moving objects was entirely different. Irrespective of the path length, object size or velocity of motion, path deviation thresholds depended simply upon the duration of the motion path in seconds. Conclusions/Significance Human vision has long been known to integrate information across space in order to solve spatial tasks such as judgment of orientation or position. Here we demonstrate an intriguing mechanism which integrates direction information across time in order to optimize the judgment of path deviation for moving objects. PMID:18414653

Whitaker, David; Levi, Dennis M.; Kennedy, Graeme J.

2008-01-01

251

Kinetic theory of random graphs: From paths to cycles  

NASA Astrophysics Data System (ADS)

The structural properties of evolving random graphs are investigated. Treating linking as a dynamic aggregation process, rate equations for the distribution of node to node distances (paths) and of cycles are formulated and solved analytically. At the gelation point, the typical length of paths and cycles, l , scales with the component size k as ltilde k1/2 . Dynamic and finite-size scaling laws for the behavior at and near the gelation point are obtained. Finite-size scaling laws are verified using numerical simulations.

Ben-Naim, E.; Krapivsky, P. L.

2005-02-01

252

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

253

Status of Fluid and Electrolyte Absorption in Cystic Fibrosis  

PubMed Central

Salt and fluid absorption is a shared function of many of the body’s epithelia, but its use is highly adapted to the varied physiological roles of epithelia-lined organs. These functions vary from control of hydration of outward-facing epithelial surfaces to conservation and regulation of total body volume. In the most general context, salt and fluid absorption is driven by active Na+ absorption. Cl? is absorbed passively through various available paths in response to the electrical driving force that results from active Na+ absorption. Absorption of salt creates a concentration gradient that causes water to be absorbed passively, provided the epithelium is water permeable. Key differences notwithstanding, the transport elements used for salt and fluid absorption are broadly similar in diverse epithelia, but the regulation of these elements enables salt absorption to be tailored to very different physiological needs. Here we focus on salt absorption by exocrine glands and airway epithelia. In cystic fibrosis, salt and fluid absorption by gland duct epithelia is effectively prevented by the loss of cystic fibrosis transmembrane conductance regulator (CFTR). In airway epithelia, salt and fluid absorption persists, in the absence of CFTR-mediated Cl? secretion. The contrast of these tissue-specific changes in CF tissues is illustrative of how salt and fluid absorption is differentially regulated to accomplish tissue-specific physiological objectives. PMID:23284077

Reddy, M.M.; Stutts, M. Jackson

2013-01-01

254

Finding reaction paths using the potential energy as reaction coordinate.  

PubMed

The intrinsic reaction coordinate curve (IRC), normally proposed as a representation of a reaction path, is parametrized as a function of the potential energy rather than the arc-length. This change in the parametrization of the curve implies that the values of the energy of the potential energy surface points, where the IRC curve is located, play the role of reaction coordinate. We use Caratheodory's relation to derive in a rigorous manner the proposed parametrization of the IRC path. Since this Caratheodory's relation is the basis of the theory of calculus of variations, then this fact permits to reformulate the IRC model from this mathematical theory. In this mathematical theory, the character of the variational solution (either maximum or minimum) is given through the Weierstrass E-function. As proposed by Crehuet and Bofill [J. Chem. Phys. 122, 234105 (2005)], we use the minimization of the Weierstrass E-function, as a function of the potential energy, to locate an IRC path between two minima from an arbitrary curve on the potential energy surface, and then join these two minima. We also prove, from the analysis of the Weierstrass E-function, the mathematical bases for the algorithms proposed to locate the IRC path. The proposed algorithm is applied to a set of examples. Finally, the algorithm is used to locate a discontinuous, or broken, IRC path, namely, when the path connects two first order saddle points through a valley-ridged inflection point. PMID:18345872

Aguilar-Mogas, Antoni; Giménez, Xavier; Bofill, Josep Maria

2008-03-14

255

Path of the Sun at Different Latitudes  

NSDL National Science Digital Library

There is a lot of information packed into this Flash animation. Find the path of the sun above the horizon (on the celestial sphere) for four locations (both poles, equator, and 41 degrees north) during equinox and solstices. An important point that can be extrapolated from this animation is that although each pole has perpetual day during its respective summer solstice, the sun never exceeds around 24 degrees above the horizon. Given the sun�s oblique rays, there is enhanced atmospheric scattering and absorption resulting in lower temperatures. In addition, ice shelves and glaciers promote high albedos, further lowering temperatures. Thus, it�s a refrigerator even during perpetual day. The animation can easily be rewound or paused to stress important points.

Burrows, Charles; District, East R.

256

Outdoor visual path following experiments  

Microsoft Academic Search

In this paper the performance of a topological- metric visual path following framework is investigated in different environments. The framework relies on a monocular camera as the only sensing modality. The path is represented as a series of reference images such that each neighboring pair contains a number of common landmarks. Local 3D geometries are reconstructed between the neighboring reference

Albert Diosi; Anthony Remazeilles; Sinisa Segvic; François Chaumette

2007-01-01

257

Path integrals as discrete sums  

SciTech Connect

We present a new formulation of Feynman's path integral, based on Voronin's theorems on the universality of the Riemann zeta function. The result is a discrete sum over paths,'' each given by a zeta function. A new measure which leads to the correct quantum mechanics is explicitly given.

Bitar, K.; Khuri, N.N.; Ren, H.C. (Supercomputer Computations Research Institute, Florida State University, Tallahasee, Florida (USA) Department of Physics, The Rockefeller University, New York, New York (USA))

1991-08-12

258

Data Generation for Path Testing  

Microsoft Academic Search

We present two stochastic search algorithms for generating test cases that execute specified paths in a program. The two algorithms are: a simulated annealing algorithm (SA), and a genetic algorithm (GA). These algorithms are based on an optimization formulation of the path testing problem which include both integer- and real-value test cases. We empirically compare the SA and GA algorithms

Nashat Mansour; Miran Salame

2004-01-01

259

Path Generation of Regular Polygon Using a Geared-Parallelogram Mechanism  

NASA Astrophysics Data System (ADS)

The paper proposes a geared-parallelogram mechanism (GPM) for path generation of regular polygon. The model presents the structural features of the mechanism as shown in Fig. 1 which forms the basis for the guiding features of its path and also for the guiding function in its kinematic parameters and dimensions. It is shown from the analysis results that length l2 has an effect on the size of the path, the initial phase ? on path direction and transmission ratio k on number of polygon sides. More important is that length ratio ? plays a crucial role in path curvature and defines indirectly the straightness for the regular polygon of path generation. In order to generate the path of regular polygon, some available value ranges of each parameter have been suggested. An example to solve path generation task with such mechanism using the method presented in this paper is given, through which a practical procedure to develop a synthesis tool for generating a regular polygon path will be provided. Fig. 1 Structural diagram of GPM

Lin, S.; Fan, Y.; Ren, Z.; Hanke, U.

260

Energy-Length Rule  

E-print Network

Lorentz ordering (causality) implies the following rule: for any given energy p0 of a system there is a certain interval c0 on x0 so that their product is the Lorentz ordering constant L It means p0c0 = L. The constant L=hc. Hence Planck constant h in a similar way as c are both consequences of Lorentz metric. The basic ideas are: 1. Lorentz metric implies that x0 must represent a length like the other components of x in X 2. The dual metric space X* is well defined since the Lorentz metric tensor is not singular. The components of the vectors p in X*are interpreted as representing energy. The properties of the physical systems that are direct consequences of the detailed structure of X and X*, and so expressed through the Lorentz Limit L are presented.

Alexandru C Mihul; Eleonora A Mihul

2006-08-25

261

Metagenomics: read length matters.  

PubMed

Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (approximately 100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (approximately 750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72% of the COG hits found using long reads. Noting the current limitation in computational approaches for the analysis of short sequences, the use of short-read-length libraries does not appear to be an appropriate tool for the metagenomic characterization of microbial communities. PMID:18192407

Wommack, K Eric; Bhavsar, Jaysheel; Ravel, Jacques

2008-03-01

262

Metagenomics: Read Length Matters? †  

PubMed Central

Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (?100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (?750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72% of the COG hits found using long reads. Noting the current limitation in computational approaches for the analysis of short sequences, the use of short-read-length libraries does not appear to be an appropriate tool for the metagenomic characterization of microbial communities. PMID:18192407

Wommack, K. Eric; Bhavsar, Jaysheel; Ravel, Jacques

2008-01-01

263

Symmetry distribution between hook length and part length for partitions  

E-print Network

2009/04/09 Symmetry distribution between hook length and part length for partitions Christine Bessenrodt and Guo-Niu Han ABSTRACT. -- It is known that the two statistics on integer partitions "hook and to the left of v, in the same column as v and under v). See Fig.1. We define the hook length (resp. part

Bessenrodt, Christine

264

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

265

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

266

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.

267

Numerical path integral techniques for long time dynamics of quantum dissipative systems  

NASA Astrophysics Data System (ADS)

Recent progress in numerical methods for evaluating the real-time path integral in dissipative harmonic environments is reviewed. Quasi-adiabatic propagators constructed numerically allow convergence of the path integral with large time increments. Integration of the harmonic bath leads to path integral expressions that incorporate the exact dynamics of the quantum particle along the adiabatic path, with an influence functional that describes nonadiabatic corrections. The resulting quasi-adiabatic propagator path integral is evaluated by efficient system-specific quadratures in most regimes of parameter space, although some cases are handled by grid Monte Carlo sampling. Exploiting the finite span of nonlocal influence functional interactions characteristic of broad condensed phase spectra leads to an iterative scheme for calculating the path integral over arbitrary time lengths. No uncontrolled approximations are introduced, and the resulting methodology converges to the exact quantum result with modest amounts of computational power. Applications to tunneling dynamics in the condensed phase are described.

Makri, Nancy

1995-05-01

268

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

269

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing  

E-print Network

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2013 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural

Mousavi, Mohammad

270

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing  

E-print Network

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2012 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural

Mousavi, Mohammad

271

Torsional and cyclic fatigue resistances of glide path preparation instruments: G-file and PathFile.  

PubMed

This study aimed to compare cyclic fatigue and torsional resistances of glide path creating instruments with different tapers and tip sizes. Two sizes (G1 and G2) from G-File system and three sizes (PathFile #1, #2, and #3) from PathFile system were used for torsional resistance and cyclic fatigue resistance tests (n?=?10). The torsional resistance was evaluated at 2-, 3-, 4-, 5-, and 6-mm from the file tip by plotting the torsional load changes until fracture by rotational loading of 2?rpm. The cyclic fatigue resistance was compared by measuring the number of cycles to failure. Data were analyzed statistically using one-way ANOVA and Duncan's post-hoc comparison. The length of the fractured file fragment was also measured. All fractured fragments were observed under a scanning electron microscope (SEM). Although G-2 file showed a lower torsional strength than PathFile #3 at 2- and 3-mm levels (p??0.05). The smaller files of each brand had a significantly higher cyclic fatigue resistance than the bigger ones (p?PathFile #1 and #2 had higher fatigue resistances than G-files (p?PathFile #3, G-2 showed the lowest and PathFile #1 showed the highest resistances among the tested groups (p?path with minimal risk of fracture. PMID:24737525

Sung, Sang Yup; Ha, Jung-Hong; Kwak, Sang-Won; Abed, Rashid El; Byeon, Kyeongmin; Kim, Hyeon-Cheol

2014-01-01

272

Metagenomics: Read length matters  

E-print Network

Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (?100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (?750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72 % of the COG hits found using long reads.

K. Eric Wommack; Jaysheel Bhavsar; Jacques Ravel

2008-01-01

273

Precision Neutron Scattering Length Measurements with Neutron Interferometry  

NASA Astrophysics Data System (ADS)

Since its inception, single-crystal neutron interferometry has often been utilized for precise neutron scattering length, b, measurements. Scattering length data of light nuclei is particularly important in the study of few nucleon interactions as b can be predicted by two + three nucleon interaction (NI) models. As such they provide a critical test of the accuracy 2+3 NI models. Nuclear effective field theories also make use of light nuclei b in parameterizing mean-field behavior. The NIST neutron interferometer and optics facility has measured b to less than 0.8% relative uncertainty in polarized ^3He and to less than 0.1% relative uncertainty in H, D, and unpolarized ^3He. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons are Bragg diffracted in the blades to produce two spatially separate (yet coherent) beam paths much like an optical Mach-Zehnder interferometer. A gas sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths which is proportional to b. This talk will focus on the latest scattering length measurement for n-^4He which ran at NIST in Fall/Winter 2010 and is currently being analyzed.

Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Shahi, C. B.; Wietfeldt, F. E.; Black, T. C.

2011-10-01

274

Coaxial atomizer liquid intact lengths  

NASA Technical Reports Server (NTRS)

Average intact lengths of round liquid jets generated by airblast coaxial atomizer were measured from over 1500 photographs. The intact lengths were studied over a jet Reynolds number range of 18,000 and Weber number range of 260. Results are presented for two different nozzle geometries. The intact lengths were found to be strongly dependent on Re and We numbers. An empirical equation was derived as a function of these parameters. A comparison of the intact lengths for round jets and flat sheets shows that round jets generate shorter intact lengths.

Eroglu, Hasan; Chigier, Norman; Farago, Zoltan

1991-01-01

275

Long Path Quantum Cascade Laser Based Sensor for Environment Sensing/Ambient Detection of CH4 and N2O  

NASA Astrophysics Data System (ADS)

Methane (CH4) and Nitrous Oxide (N2O) are long-lived greenhouse gases in the atmosphere with significant global warming effects. These gases also are known to be produced in a number of anthropogenic settings such as manure management systems, which releases substantial GHGs and is mandated by the EPA to provide continuous monitoring. In addition, natural gas leaks in urban areas is another source of strong spatially inhomogeneous methane emissions Most open path methods for quantitative detection of trace gases utilize either Fourier Transform Spectrometer (FTIR) or near-IR differential optical absorption spectroscopy (DOAS). Although, FTIR is suitable for ambient air monitoring measurement of more abundant gases such as CO2 and H20 etc., the lack of spectral resolution makes the retrieval of weaker absorbing features such as N20 more difficult. On the other hand, conventional DOAS systems can be large and impractical. As an alternative, we illustrate a robust portable quantum cascade laser (QCL) approach for simultaneous detection of CH4 and N2O. In particular, gas spectra were recorded by ultrafast pulse intensity (thermal) chirp tuning over the 1299 - 1300cm-1 spectral window. Etalon measurements insure stable tuning was obtained. To deal with multiple species, a LSQ spectral fitting approach was used which accounted for both the overlapping trace gases , background water vapor as well as detector drift and calibration. In summary, ambient concentrations of CH4 with and N2O with accuracy < 1% was obtained on the order of 5ms using optical paths of 500 m path length. In addition, unattended long term operation was demonstrated and validations using other sensors when possible were shown to be consistent. The system accuracy is limited by systemic errors, which are still being explored.

Castillo, P. C.; Sydoryk, I.; Gross, B.; Moshary, F.

2013-12-01

276

Propagation and absorption of high-intensity femtosecond laser radiation in diamond  

NASA Astrophysics Data System (ADS)

Femtosecond interferometry has been used to experimentally study the photoexcitation of the electron subsystem of diamond exposed to femtosecond laser pulses of intensity 1011 to 1014 W cm-2. The carrier concentration has been determined as a function of incident intensity for three harmonics of a Ti : sapphire laser (800, 400 and 266 nm). The results demonstrate that, in a wide range of laser fluences (up to those resulting in surface and bulk graphitisation), a well-defined multiphoton absorption prevails. We have estimated nonlinear absorption coefficients for pulsed radiation at ? = 800 nm (four-photon transition) and at 400 and 266 nm (indirect and direct two-photon transitions, respectively). It has also been shown that, at any considerable path length of a femtosecond pulse in diamond (tens of microns or longer), the laser beam experiences a severe nonlinear transformation, determining the amount of energy absorbed by the lattice, which is important for the development of technology for diamond photostructuring by ultrashort pulses. The competition between wave packet self-focusing and the plasma defocusing effect is examined as a major mechanism governing the propagation of intense laser pulses in diamond.

Kononenko, V. V.; Konov, V. I.; Gololobov, V. M.; Zavedeev, E. V.

2014-12-01

277

Industrial applications of open-path Fourier transform infrared spectrometry  

NASA Astrophysics Data System (ADS)

A commercially available fieldable Fourier transform infrared (FT-IR) spectrometer has been evaluated for monitoring volatile organic compounds (VOCs) in and around incineration equipment for VOC emissions. During this data collection a 20 X 20 inch polished stainless steel plate was used as the reflection surface, to evaluate the use of less expansive optics for industrial applications. Research has also progressed on developing a method to produce an I0 spectrum utilizing a short path length.

Spartz, Martin L.; Eldridge, Jess S.; Hipple, Gary D.; Reagen, William K.; Stock, Jeffrey W.

1994-01-01

278

Extreme light absorption in a necking-free monolayer of resonant-size nanoparticles for photoelectrochemical cells  

NASA Astrophysics Data System (ADS)

Semiconductor photoelectrodes for water oxidation that absorb visible light usually have poor electronic transport properties and small optical absorption coefficients near their absorption edge. Therefore, innovative designs that lead to significant optical absorption in relatively thin layers of these compounds are highly desirable. Here, using full-field electromagnetic optical simulations, we demonstrate that a monolayer of resonant-size {{BiV}}{{{{O}}}_{4}} spheres can provide enhancement up to a factor of two in solar light absorption relative to dense planar layers. In this monolayer, {{BiV}}{{{{O}}}_{4}} spheres do not need to be interconnected; therefore, such monolayers are flexible and their fabrication process does not require the complicated necking steps to establish electrical contact among the nanoparticles. These resonant-size spheres support Mie resonance modes that efficiently trap light and hence significantly increase effective optical path length. Under air mass 1.5 global (AM1.5G) irradiation, the maximum achievable photocurrent density (MAPD) in a monolayer of 250 nm diameter {{BiV}}{{{{O}}}_{4}} spheres reaches 4.9 mA.cm^{-2}. This is about twofold improvement over the MAPD for a 250 nm thick dense planar layer and well above the 3.8\\;{{mA}}.{{c}}{{{{m}}}^{-2}} MAPD for a 1 ?m thick dense planar layer. In addition, it is shown that lower-order resonance modes of the spheres are superior to higher-order modes for broadband optical absorption. The insight provided in this work can also be applied to nitride and oxynitride photoanode materials.

Dabirian, Ali

2014-07-01

279

Partnership for Advancing Technologies in Housing (PATH)  

NSF Publications Database

... Technology Systems Interactions and Whole House Approaches PATH?s mission is to advance technology ... technology arena. Far reaching exploratory research that can lead to breakthrough technologies and ...

280

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

281

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

282

Collaborative Authoring of Walden's Paths  

E-print Network

of educators, the authoring tool allows educators to collaboratively build a Walden's Path by filtering and organizing web pages into an ordered linear structure for the common information needs, which can be extended, tailored and modified into a derivative...

Li, Yuanling

2012-10-19

283

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

284

Quantum Mechanics: Sum Over Paths  

NSDL National Science Digital Library

Created by Edwin F. Taylor a former professor at the Department of Physics at the Massachusetts Institute of Technology, this material describes methods of presenting quantum mechanics using the path-integral formulation. Included are links to a paper and presentation outlining the method, software to simulate the path integrals, and student workbook materials. This course has been used for introducing quantum physics to high school teachers.

Taylor, Edwin F.

2009-05-26

285

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

286

Intestinal magnesium absorption.  

PubMed

Available data on the mechanism of Mg absorption is mainly descriptive in nature. There is data to support the existence of both gradient-driven and saturable Mg absorption. It is not clear, however, which process predominates under normal conditions. Evidence for a saturable process is based on a curvilinear relationship between dietary or luminal [Mg] and Mg uptake. Whether this is due to a carrier-mediated mechanism or due to alterations in absorption through the paracellular route remains to be determined. A careful review of the literature indicates that the predominate site of Mg absorption is the distal small intestine. Most of these studies, however, have been done in isolated segments which may not adequately reflect absorption in an undisturbed gastrointestinal tract. Future work will need to focus on identifying and characterizing Mg transport at the cellular and paracellular level as well as developing more sophisticated strategies for examining Mg absorption in the whole animal. PMID:8264506

Kayne, L H; Lee, D B

1993-01-01

287

Planning of Axiom Absorptions  

E-print Network

Abstract. Absorptions are generally employed in Description Logics (DL) reasoners in a uniform way regardless of the structure of an input knowledge base. In this paper we present an approach to encode some state-of-the-art absorption techniques into a state space planner, aiming to achieve a better solution. The planner applies appropriate operators to general axioms and produces a solution with a minimized cost to automatically organize these absorptions in a certain sequence to facilitate DL reasoning. Compared to predetermined or fixed applications of established absorptions, such a solution is more flexible and probable to absorb more general axioms into an unfoldable TBox. 1

unknown authors

288

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

289

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

290

Anti-interference performance of multi-path direct sequence spread spectrum wireless communication system  

Microsoft Academic Search

In order to improve information transmission rate in unit bandwidth, using direct-sequence spread-spectrum CDMA thinking, creatively present a new multi-path direct sequence spread spectrum wireless communication systems' model, and give its multi-path interference performance based on MATLAB. Simulation results show that the system can increase the information transmission rate in unit bandwidth through enhancing the length of the spreading code

Caijiao Xue

2010-01-01

291

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

292

Emission and Absorption Lines  

NSDL National Science Digital Library

This webpage from the University of California, Riverside offers an explanation of emission and absorption lines. A diagram, with descriptive text, shows how light from a star can produce each type of line. Also, an image of solar absorption lines is provided.

Wudka, Jose

2007-12-20

293

Incarceration Length, Employment, and Earnings  

Microsoft Academic Search

This paper estimates effects of increases in incarceration length on employment and earnings prospects of individuals after their release from prison. I utilize a variety of research designs including controlling for observable factors and using instrumental variables for incarceration length based on randomly assigned judges with different sentencing propensities. The results show no consistent evidence of adverse labor market consequences

Jeffrey R. Kling

2006-01-01

294

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)

Math, Illuminations N.

2009-01-28

295

Line Lengths and Starch Scores.  

ERIC Educational Resources Information Center

Investigates readability of different line lengths in advertising body copy, hypothesizing a normal curve with lower scores for shorter and longer lines, and scores above the mean for lines in the middle of the distribution. Finds support for lower scores for short lines and some evidence of two optimum line lengths rather than one. (SKC)

Moriarty, Sandra E.

1986-01-01

296

Petawatt laser absorption bounded.  

PubMed

The interaction of petawatt (10(15)?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

297

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

298

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

299

Gestation length in farmed reindeer.  

PubMed

Reindeer (Rangifer tarandus tarundus) are the only cervids indigenous to the arctic environment. In Alaska, reindeer are a recognized agricultural species and an economic mainstay for many native populations. Traditionally raised in extensive free-ranging systems, a recent trend toward intensive farming requires a more in-depth knowledge of reproductive management. Reported gestation length in reindeer varies, ranging from 198 to 229 d in studies performed at the University of Alaska Fairbanks. A switchback study that manipulated only breeding date demonstrated a mean increase in gestation length of 8.5 d among females bred early in the season. The negative correlation between conception date and gestation length is consistent with reindeer research at other locations and reports of variable gestation length in a growing number of domestic and non-domestic species. This paper reviews the phenomenon in reindeer and discusses some of the factors known to affect gestation length as well as possible areas for future research. PMID:21755691

Shipka, M P; Rowell, J E

2010-01-01

300

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...

301

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

302

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

2013-12-15

303

Remote sensing of NO using a differential absorption lidar.  

PubMed

Single-ended remote sensing measurements of atmospheric NO have been made using differential absorption of frequency-doubled pulsed CO(2) laser radiation backscattered from topographic targets. Returns were obtained from targets at ranges out to 1.4 km, and significant NO concentrations above ambient were observed over a path which crossed a traffic roadway at a range of 0.5 km. In view of the severe atmospheric water vapor absorption in the spectral region containing the NO absorption band, the range dependence of the lidar returns was also measured in order to determine the differential absorption of the ambient atmosphere.The results differed significantly from those computed from atmospheric transmission data tapes. PMID:20234607

Menyuk, N; Killinger, D K; Defeo, W E

1980-10-01

304

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

305

Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10?m thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the detectable sensitivity is of the order of 1ppm.

Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

2010-04-01

306

Path-integral seismic imaging  

Microsoft Academic Search

A new type of seismic imaging, based on Feynman path integrals for waveform mod- elling, is capable of producing accurate subsurface images without any need for a reference velocity model. Instead of the usual optimization for traveltime curves with maximal signal semblance, a weighted summation over all representative curves avoids the need for velocity analysis, with its common difficulties of

E. Landa; S. Fomel; T. J. Moser

2006-01-01

307

Path integrals for potential scattering  

Microsoft Academic Search

Two path integral representations for the T matrix in nonrelativistic potential scattering are derived and proved to produce the complete Born series when expanded to all orders. They are obtained with the help of ``phantom'' degrees of freedom which take away explicit phases that diverge for asymptotic times. In addition, energy conservation is enforced by imposing a Faddeev-Popov-like constraint in

R. Rosenfelder

2009-01-01

308

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...

309

Hand-ginned cotton length distributions  

Technology Transfer Automated Retrieval System (TEKTRAN)

Instrumentation such as the Advanced Fiber Information System (AFIS™) analyzes cotton (Gossypium hirsutum L.) fiber length distributions because variations in fiber length distribution impacts spinning performance. AFIS provides mean length, upper quartile length, fineness, and maturity for fibers ...

310

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

311

Unrestrained Computation of Free Energy along a Path  

PubMed Central

We apply the adaptive biasing potential (ABP) method to optimize the principal curve defining a conformational transition between two known end states and to subsequently compute the one-dimensional potential of mean force as a function of arc length along the principal curve. This approach allows the use of the ABP method in a collective variable space of arbitrary dimension and offers several advantages over line-search methods. First, configurations are neither generated along an initial path for the transition nor equilibrated during evolution of the path. Second, and most importantly, the powerful sampling provided by the ABP serves to accelerate the dynamics during the optimization and computation of the free energy. Finally, the free energy is formulated as a potential of mean force that captures changes in the reaction channel along the principal curve, in contrast to the free energy profile evaluated from the local free-energy gradient in restrained path optimization methods. We first demonstrate the ABP formulation of path optimization using a two-dimensional potential surface and then with a more complex system of Src protein tyrosine kinase. The method is shown to be efficient and robust in the case of rugged, free-energy landscapes. PMID:22816870

Dickson, Bradley M.; Huang, He; Post, Carol Beth

2013-01-01

312

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

313

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

314

Scale Length of Disk Galaxies  

NASA Astrophysics Data System (ADS)

As a part of a Euro-VO research initiative, we have undertaken a programme aimed at studying the scale length of 54909 Sa-Sd spiral galaxies from the SDSS DR6 catalogue. We have retrieved u, g, r, i, z-band images for all galaxies in order to derive the light profiles. We also calculate asymmetry parameters to select non-disturbed disks for which we will derive exponential disk scale lengths. As images in different bands probe different optical depths and stellar populations, it is likely that a derived scale length value should depend on waveband, and our goal is to use the scale length variations with band pass, inclination, galaxy type, redshift, and surface brightness, in order to better understand the nature of spiral galaxies.

Fathi, K.; Allen, M.; Gonzalez-Solares, E.; Hatziminaoglou, E.; Peletier, R.

2009-07-01

315

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

316

Drug Absorption Principles  

Microsoft Academic Search

Pharmacokinetics describes drug absorption, distribution, metabolism, and excretion processes. Absorption is the rate and\\u000a extent at which drugs reach the systemic circulation from the site of administration. Distribution of a drug includes all\\u000a the processes that are involved from the time when the drug reaches the circulation to the time when it (or a metabolite of\\u000a the drug) leaves the

Xianhua Cao; Lawrence X. Yu; Duxin Sun

317

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

318

Optical absorption measurement system  

DOEpatents

The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

Draggoo, Vaughn G. (Livermore, CA); Morton, Richard G. (San Diego, CA); Sawicki, Richard H. (Pleasanton, CA); Bissinger, Horst D. (Livermore, CA)

1989-01-01

319

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

320

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

321

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

322

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

323

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

324

Defining and evaluating wrapping surfaces for MRI-derived spinal muscle paths.  

PubMed

Muscle paths can be approximated in biomechanical models by wrapping the path around geometric objects; however, the process for selecting and evaluating wrapping surface parameters is not well defined, especially for spinal muscles. In this study, we defined objective methods to select the shape, orientation, size and location of wrapping surfaces and evaluated the wrapping surfaces using an error metric based on the distance between the modeled muscle path and the centroid path from magnetic resonance imaging (MRI). We applied these methods and the error metric to a model of the neck musculature, where our specific goals were (1) to optimize the vertebral level at which to place a single wrapping surface per muscle; and (2) to define wrapping surface parameters in the neutral posture and evaluate them in other postures. Detailed results are provided for the sternocleidomastoid and the semispinalis capitis muscles. For the sternocleidomastoid, the level where the wrapping surface was placed did not significantly affect the error between the modeled path and the centroid path; use of wrapping surfaces defined from the neutral posture improved the representation of the muscle path compared to a straight line in all postures except contralateral rotation. For the semispinalis capitis, wrapping surfaces placed at C3 or C4 resulted in lower error compared to other levels; and the use of wrapping surfaces significantly improved the muscle path representation in all postures. These methods will be used to improve the estimates of muscle length, moment arm and moment-generating capacity in biomechanical models. PMID:18402966

Vasavada, Anita N; Lasher, Richard A; Meyer, Travis E; Lin, David C

2008-01-01

325

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

326

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

327

Circular Digraph Walks, k-Balanced Strings, Lattice Paths and Chebychev Polynomials  

Microsoft Academic Search

We count the number of walks of length n on a k-node circular digraph that cover all k nodes in two ways. The first way illustrates the transfer-matrix method. The second involves counting various classes of height-restricted lattice paths. We observe that the results also count so-called k-balanced strings of length n, generalizing a 1996 Putnam problem.

Evangelos Georgiadis; David Callan; Qing-Hu Hou

2008-01-01

328

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

329

A study of water vapor absorption at CO2 laser frequencies using a differential spectrophone and white cell  

Microsoft Academic Search

Water vapor absorption at CO2 laser frequencies has been studied using a differential spectrophone and a long path multiple traversal cell. The results of these measurements have been analyzed in terms of the Lorentz line shape and the far wing model for continuum absorption in the 9-10 micrometers wavelength region. An electronically stabilized, grating tunable cw CO2 laser with a

J. C. Peterson

1978-01-01

330

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

331

Thermodynamic length, time, speed, and optimum path to minimize entropy production  

Microsoft Academic Search

In addition to the Riemannian metricization of the thermodynamic state space, local relaxation times offer a natural time scale, too. Generalizing existing proposals, we relate {\\\\it thermodynamic} time scale to the standard kinetic coefficients of irreversible thermodynamics. Criteria for minimum entropy production in slow, slightly irreversible processes are discussed. Euler-Lagrange equations are derived for optimum thermodynamic control for fixed clock-time

L. Diósi; K. Kulacsy; B. Lukács; A. Rácz

1996-01-01

332

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2011 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO, AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Television Broadcast Auxiliary Stations §...

2011-10-01

333

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

334

Length-weight and length-length relationships of fish species from the Aegean Sea (Greece)  

Microsoft Academic Search

Summary We present the relationships between total (TL), fork(FL) and standard (SL) length for 37 fish species and the relationships between TL and wet weight for 40 fish species from the Aegean Sea (Cyclades; Greece). The relationships between TL, FL and SL were all linear (for all cases: r2 > 0.928). The values of the exponent b of the length-weight

D. K. Moutopoulos; K. I. Stergiou

2002-01-01

335

Path-Based Failure and Evolution Management  

Microsoft Academic Search

We present a new approach to managing failures and evolution in large, complex distributed systems using runtime paths. We use the paths that requests follow as they move through the system as our core abstraction, and our \\

Mike Y. Chen; Anthony Accardi; Emre Kiciman; David A. Patterson; Armando Fox; Eric A. Brewer

2004-01-01

336

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

337

Copper foil provides uniform heat sink path  

NASA Technical Reports Server (NTRS)

Thermal path prevents voids and discontinuities which make heat sinks in electronic equipment inefficient. The thermal path combines the high thermal conductivity of copper with the resiliency of silicone rubber.

Phillips, I. E., Jr.; Schreihans, F. A.

1966-01-01

338

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

339

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

340

Multiple paths to encephalization and technical civilizations.  

PubMed

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. PMID:22139517

Schwartzman, David; Middendorf, George

2011-12-01

341

Persistence Length of Stable Microtubules  

NASA Astrophysics Data System (ADS)

Microtubules are a vital component of the cytoskeleton. As the most rigid of the cytoskeleton filaments, they give shape and support to the cell. They are also essential for intracellular traffic by providing the roadways onto which organelles are transported, and they are required to reorganize during cellular division. To perform its function in the cell, the microtubule must be rigid yet dynamic. We are interested in how the mechanical properties of stable microtubules change over time. Some "stable" microtubules of the cell are recycled after days, such as in the axons of neurons or the cilia and flagella. We measured the persistence length of freely fluctuating taxol-stabilized microtubules over the span of a week and analyzed them via Fourier decomposition. As measured on a daily basis, the persistence length is independent of the contour length. Although measured over the span of the week, the accuracy of the measurement and the persistence length varies. We also studied how fluorescently-labeling the microtubule affects the persistence length and observed that a higher labeling ratio corresponded to greater flexibility.

Hawkins, Taviare; Mirigian, Matthew; Selcuk Yasar, M.; Ross, Jennifer

2011-03-01

342

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

343

Application of Length-Based DNA Computing for Complex Scheduling Problem  

Microsoft Academic Search

This paper discussed the implementation ideas and experimental procedures to solve an engineering related combinatorial problem using DNA computing approach. An elevator scheduling problem is chosen as a benchmark where all the elevator traveled paths are represented by DNA sequence of specific length that represent the elevator's traveling time in a proportional way based on certain initial conditions such as

Mohd Saufee Muhammad; Zuwairie Ibrahim; Satomi Ueda; Osamu Ono; Marzuki Khalid

2005-01-01

344

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

345

High-temperature laser interferometer for thermal expansion and optical-length measurements  

Microsoft Academic Search

A simple laser interferometer has been utilized to measure the thermal expansion and optical-length variation with temperature of highly reactive fluorides at high temperatures. The interferometer is a modification of the Jamin interferometer in which a laser beam is split into two parallel beams which traverse nearly identical paths and are reflected from the sample and a reference mirror. The

T. S. AuroraS; S. M. Day; V. King; D. O. Pederson

1984-01-01

346

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

347

Multiphoton Path Entanglement by Nonlocal Bunching  

Microsoft Academic Search

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2005-01-01

348

Multilinear decomposition of human walking paths  

Microsoft Academic Search

In a previous work, the authors have shown how the Principal Components Analysis (PCA) of a set of human walking paths provides sufficient information to derive a linear human-like path generator based on examples. The present work aims to provide an analysis of human walking paths from the perspective of multilinear algebra, using the n-mode Singular Value Decomposition (SVD). This

Christian A. Ramirez; M. Castela?n; G. Arechavaleta

2010-01-01

349

SOME PROPERTIES OF PATH MEASURES CHRISTIAN LEONARD  

E-print Network

an unbounded measure. Indeed, its reversing measure is Lebesgue measure (or any of its positive multiple x Rn . Obviously, this path measure has the same unbounded mass as Lebesgue measure.SOME PROPERTIES OF PATH MEASURES CHRISTIAN L´EONARD Abstract. We call any measure on a path space

Paris-Sud XI, Université de

350

Evaluation of the Learning Path Specification  

ERIC Educational Resources Information Center

Flexible lifelong learning requires that learners can compare and select learning paths that best meet individual needs, not just in terms of learning goals, but also in terms of planning, costs etc. To this end a learning path specification was developed, which describes both the contents and the structure of any learning path, be it formal,…

Janssen, Jose; Berlanga, Adriana J.; Koper, Rob

2011-01-01

351

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

352

Test data generation and feasible path analysis  

Microsoft Academic Search

This paper describes techniques used by Test Specifica- tion and Determination Tool (TSDT), an experimental prototype for analysis and testing of critical applica- tions written in Ada. Two problems dominate structural testing of programs: exponential explosion in the num- ber of execution paths and feasible path determination, A path is feasible if there exists some input that will cause the

Robert Jasper; Mike Brennan; Keith E. Williamson; Bill Currier; David Zimmerman

1994-01-01

353

Improving the Quality of Non-Holonomic Motion by Hybridizing C-PRM Paths  

E-print Network

Sampling-based motion planners are an effective means for generating collision-free motion paths. However, the quality of these motion paths, with respect to different quality measures such as path length, clearance, smoothness or energy, is often notoriously low. This problem is accentuated in the case of non-holonomic sampling-based motion planning, in which the space of feasible motion trajectories is restricted. In this study, we combine the C-PRM algorithm by Song and Amato with our recently introduced path-hybridization approach, for creating high quality non-holonomic motion paths, with combinations of several different quality measures such as path length, smoothness or clearance, as well as the number of reverse car motions. Our implementation includes a variety of code optimizations that result in nearly real-time performance, and which we believe can be extended with further optimizations to a real-time tool for the planning of high-quality car-like motion.

Berger, Itamar; Zohar, Gal; Raveh, Barak; Halperin, Dan

2010-01-01

354

Application of open-path spectroscopic measurement techniques (FTIR) for the up-scaling of greenhouse gas emissions from soils  

NASA Astrophysics Data System (ADS)

The path-averaging, multi-component Fourier Transform Infrared (FTIR) absorption spectrometry at an open path of 100 m length is applied for the up-scaling of greenhouse gas (GHG) flux measurements from soil surfaces. For the detection of the emissions of N2O and further GHG from arable field soils a measuring tunnel for controlled enrichment of released gases was installed at the soil surface covering an area of 495 or 306 m2. The concentrations of GHG were measured by FTIR across the whole measuring tunnel. The precision of the FTIR system is discussed to detect the concentration increases during a time period of up to two hours. During a 2-years-time frame the N2O fluxes between the soil and the atmosphere at the agricultural field varied between 1.0 and 21 ?g N2O-N m-2 h-1. A non-intrusive emission and flux measurement method at a scale from 100 m up to 27.000 m2 on the basis of the fluxgradient method (0.50 and 2.70 m height above surface) was developed and tested by means of FTIR (N2O and further GHG concentrations) and area averaging meteorological measurements (determination of horizontal winds and friction velocity using acoustic tomography). To detect the concentration gradient between the two heights the precision of the FTIR system is discussed. Two campaigns in October 2007 and June 2008 were performed with this new methodology when wind speeds were low. The measurement errors are discussed and the results compared with the measurement tunnel results that were higher by up to 25 %.

Schäfer, Klaus; Jahn, Carsten; Wiwiorra, Michael; Schleichardt, Anja; Emeis, Stefan; Raabe, Armin; Böttcher, Jürgen; Landmeyer, Nils-Demian; Bonecke, Christoph; Deurer, Marcus; von der Heide, Carolin; Weymann, Daniel

2009-09-01

355

Parametric study of the absorption cross section for a moderately conducting thin cylinder  

NASA Astrophysics Data System (ADS)

A system has been developed to measure the absorption cross section for a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths of the fibers considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 mu m. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.

Gurton, Kristan P.; Bruce, Charles W.

1995-05-01

356

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

357

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

2006-07-28

358

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

359

Electron Mean Free Path in Epitaxial Ta(001) Layers  

NASA Astrophysics Data System (ADS)

Epitaxial tantalum layers were grown on MgO(001) by ultrahigh vacuum magnetron sputter deposition at 650 °C to thicknesses d ranging from 5 nm to 2 mum. X-ray diffraction including o-2theta, o rocking curve, and ? scans confirm that the layers are Ta(001) single crystals, while X-ray reflectivity indicates that their roughness is < 0.1 nm for short lateral length scales. The measured room temperature resistivity increases from 12.6+/-0.6 muO-cm for large d to 42.1+/-0.9 muO-cm for d = 5 nm. This increase is well described by the Fuchs-Sondheimer model, yielding a Ta room temperature bulk electron mean free path of lambda294K = 28+/-1 nm. Corresponding measurements in liquid nitrogen yield lambda77K = 65+/-5 nm. These values are approximately an order of magnitude larger than 2.35 and 8.36 nm, respectively, expected from the free electron model. This large discrepancy is attributed to the highly non-spherical Ta Fermi surface. More importantly, the ratio of the measured mean free path lambda77K/ lambda 294K= 2.32 is 1.5x smaller than the ratio of the measured bulk resistivities rho294Krho77K. This suggests that either (i) the mean free path is strongly band dependent, (ii) surface roughness contributes greatly to electron scattering at low temperatures in films of thickness on the order of the mean free path, or (iii) the electron mean free path at low temperature is restricted by the presence of impurities, evidenced by a measured residual resistivity.

Guan, Daniel

360

Overview of bunch length measurements.  

SciTech Connect

An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed.

Lumpkin, A. H.

1999-02-19

361

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

362

Hypertext Paths and the World-Wide Web: Experiences with Walden's Paths  

Microsoft Academic Search

Walden's Paths applies the concept of hypertextual paths to the World-Wide Web. Walden's Paths is being developed for use in the K-12 school environment. The heterogene- ity of the Web coupled with the desirability of supporting the teacher-student relationship make this an interesting and challenging project. We describe the Walden's Paths imple- mentation, discuss ...

Richard Furuta; Frank M. Shipman III; Catherine C. Marshall; Donald Brenner; Hao-wei Hsieh

1997-01-01

363

Percutaneous absorption from soil.  

PubMed

Abstract Some natural sites, as a result of contaminants emitted into the air and subsequently deposited in soil or accidental industrial release, have high levels of organic and non-organic chemicals in soil. In occupational and recreation settings, these could be potential sources of percutaneous exposure to humans. When investigating percutaneous absorption from soil - in vitro or vivo - soil load, particle size, layering, soil "age" time, along with the methods of performing the experiment and analyzing the results must be taken into consideration. Skin absorption from soil is generally reduced compared with uptake from water/acetone. However, the absorption of some compounds, e.g., pentachlorophenol, chlorodane and PCB 1254, are similar. Lipophilic compounds like dichlorodiphenyltrichloroethane, benzo[A]pyrene, and metals have the tendency to form reservoirs in skin. Thus, one should take caution in interpreting results directly from in vitro studies for risk assessment; in vivo validations are often required for the most relevant risk assessment. PMID:25205703

Andersen, Rosa Marie; Coman, Garrett; Blickenstaff, Nicholas R; Maibach, Howard I

2014-01-01

364

Portable Instrument to Measure CDOM Light Absorption in Aquatic Systems: WPI Success Story  

NASA Technical Reports Server (NTRS)

World Precision Instruments, Inc. (WPI), of Sarasota, FL, in collaboration with NASA's John C. Stennis Space Center, has developed an innovative instrument to accurately measure Colored Dissolved Organic Matter (CDOM) absorption in the field. This successful collaboration has culminated in an exciting new device, called the UltraPath, now commercially available through WPI. Traditional methods of measuring absorption of dissolved materials require special handling and storage prior to measurement. Use of laboratory spectrophotometers as the measuring devices have proven time consuming, cumbersome, and delicate to handle. The UltraPath provides a low-cost, highly sensitive, rugged, portable system that is capable of high sensitivity measurements in widely divergent waters.

2001-01-01

365

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

366

Longest Path Problems on Ptolemaic Graphs  

NASA Astrophysics Data System (ADS)

Longest path problem is a problem for finding a longest path in a given graph. While the graph classes in which the Hamiltonian path problem can be solved efficiently are widely investigated, there are few known graph classes such that the longest path problem can be solved efficiently. Polynomial time algorithms for finding a longest cycle and a longest path in a Ptolemaic graph are proposed. Ptolemaic graphs are the graphs that satisfy the Ptolemy inequality, and they are the intersection of chordal graphs and distance-hereditary graphs. The algorithms use the dynamic programming technique on a laminar structure of cliques, which is a recent characterization of Ptolemaic graphs.

Takahara, Yoshihiro; Teramoto, Sachio; Uehara, Ryuhei

367

Cellular Absorption of Herbicides  

NSDL National Science Digital Library

Before a herbicide can kill a plant, it must be absorbed by the plant’s leaves or roots and enter a cell which possesses the metabolic pathway the herbicide targets.  This lesson follows the fate of the herbicide after it has entered the plant via leaf or root tissue, and explains the factors controlling transport of a herbicide into plant cells.  This lesson describes 1) the barriers to herbicide entry, such as the plant cell membrane, 2) the role that the herbicide’s chemical properties have on the rate of cellular absorption, and 3) experimental approaches to understanding herbicide absorption at the cellular level.

368

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

369

Telomere length in human blastocysts.  

PubMed

This is a retrospective study aiming to assess telomere length in human embryos 4 days post fertilization and to determine whether it is correlated to chromosomal ploidy, embryo developmental rate and patient age. Embryos were donated from patients undergoing treatment in the assisted conception unit. Seven couples took part, generating 35 embryos consisting of 1130 cells. Quantitative fluorescent in-situ hybridization (FISH) measured the telomere length of every cell using a pan-telomeric probe. Conventional FISH on six chromosomes was used to assess aneuploidy in the same cells. Maternal and paternal age, referral reason, embryo developmental rate and type of chromosomal error were taken into account. Chromosomally abnormal cells were associated with shorter telomeres than normal cells for embryos that were developmentally slow. Cells produced by women of advanced maternal age and those with a history of repeated miscarriage tended to have substantially shorter telomeres. There was no significant difference in telomere length with respect to the rate of embryo development 5 days post fertilization. Telomeres play an important role in cell division and shorter telomeres may affect embryonic ploidy. Reduced telomere length was associated with aneuploid cells and embryos from women of advanced maternal age. PMID:24581987

Mania, Anastasia; Mantzouratou, Anna; Delhanty, Joy D A; Baio, Gianluca; Serhal, Paul; Sengupta, Sioban B

2014-05-01

370

Telomere Length Wildlife Aging Technique  

E-print Network

2/22/2009 1 Telomere Length as a Wildlife Aging Technique Forestry, Wildlife and Fisheries GraduateNon-invasive genetic sampling Telomeres: · Form · Function · Methods of measuring · Telomeres in wildlife aging #12;2/22/2009 4 Telomere Form: ·Short repeated sequences of DNA ·Found at the ends of linear eukaryotic

Gray, Matthew

371

Persistent Criminality and Career Length  

ERIC Educational Resources Information Center

This study is an examination of persistent offending and its implications for the understanding and investigation of desistance and career length. Persistence, especially as it is operationalized using official measures, is characterized as fundamentally a measure of resistance to formal social control: continued crime in the face of increasingly…

Haapanen, Rudy; Britton, Lee; Croisdale, Tim

2007-01-01

372

Seismic Hazard and Fault Length  

Microsoft Academic Search

If mx is the largest earthquake magnitude that can occur on a fault, then what is mp, the largest magnitude that should be expected during the planned lifetime of a particular structure? Most approaches to these questions rely on an estimate of the Maximum Credible Earthquake, obtained by regression (e.g. Wells and Coppersmith, 1994) of fault length (or area) and

N. M. Black; D. D. Jackson; L. Mualchin

2005-01-01

373

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

374

Timeless path integral for relativistic quantum mechanics  

NASA Astrophysics Data System (ADS)

Starting from the canonical formalism of relativistic (timeless) quantum mechanics, the formulation of a timeless path integral is rigorously derived. The transition amplitude is reformulated as the sum, or functional integral, over all possible paths in the constraint surface specified by the (relativistic) Hamiltonian constraint, and each path contributes with a phase identical to the classical action divided by ?. The timeless path integral manifests the timeless feature as it is completely independent of the parametrization for paths. For the special case that the Hamiltonian constraint is a quadratic polynomial in momenta, the transition amplitude admits the timeless Feynman's path integral over the (relativistic) configuration space. Meanwhile, the difference between relativistic quantum mechanics and conventional nonrelativistic (with time) quantum mechanics is elaborated on in light of the timeless path integral.

Chiou, Dah-Wei

2013-06-01

375

Highly-Sensitive and Efficient Infrared Absorption Spectroscopy  

E-print Network

Highly-Sensitive and Efficient Infrared Absorption Spectroscopy of Molecular Ions Mike Lindsay Oka diameter inner bore ·Discharge column length ~1 m ·Gas flow rate ~ 200 L/Min ·TRot ~500 K, TVib ~ 1500 K of molecular species High-spatial resolution Measurement of spectral fingerprint Generally applicable Low

Lindsay, C. Michael

376

Path Integration: Effect of Curved Path Complexity and Sensory System on Blindfolded Walking  

PubMed Central

Path integration refers to the ability to integrate continuous information of the direction and distance travelled by the system relative to the origin. Previous studies have investigated path integration through blindfolded walking along simple paths such as straight line and triangles. However, limited knowledge exists regarding the role of path complexity in path integration. Moreover, little is known about how information from different sensory input systems (like vision and proprioception) contributes to accurate path integration. The purpose of the current study was to investigate how sensory information and curved path complexity affect path integration. Forty blindfolded participants had to accurately reproduce a curved path and return to the origin. They were divided into four groups that differed in the curved path, circle (simple) or figure-eight (complex), and received either visual (previously seen) or proprioceptive (previously guided) information about the path before they reproduced it. The dependent variables used were average trajectory error, walking speed, and distance travelled. The results indicated that (a) both groups that walked on a circular path and both groups that received visual information produced greater accuracy in reproducing the path. Moreover, the performance of the group that received proprioceptive information and later walked on a figure-eight path was less accurate than their corresponding circular group. The groups that had the visual information also walked faster compared to the group that had proprioceptive information. Results of the current study highlight the roles of different sensory inputs while performing blindfolded walking for path integration. PMID:22840893

Koutakis, Panagiotis; Mukherjee, Mukul; Vallabhajosula, Srikant; Blanke, Daniel J.; Stergiou, Nicholas

2012-01-01

377

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

378

Broadband solar absorption enhancement via periodic nanostructuring of electrodes  

NASA Astrophysics Data System (ADS)

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.

Adachi, Michael M.; Labelle, André J.; Thon, Susanna M.; Lan, Xinzheng; Hoogland, Sjoerd; Sargent, Edward H.

2013-10-01

379

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

380

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) that is one of the primary contributors to annual global VOC emissions. Produced by vegetation as well as anthropogenic sources, the OH- and O3-initiated oxidations of isoprene are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, however, limiting the ability to quantify isoprene emissions via stand-off infrared or in situ detection. We thus report absorption coefficients 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 66v FTIR. Composite spectra are derived from a minimum of seven isoprene sample pressures at each temperature and the number densities are normalized to 296 K and 1 atmosphere.

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

2014-04-01

381

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...

382

Gas Lamp Absorption  

NSDL National Science Digital Library

This resource, part of the Spectroscopy Lab Suite, simulates optical transitions in gasses. Absorption spectra from gas emission tubes illuminated by a white light are shown, along with a tool for students to create bound state energy levels and electronic transitions to match the observed spectra.

Group, Kansas S.; Zollman, Dean A.

2004-03-05

383

Lipids: Absorption and transport  

Technology Transfer Automated Retrieval System (TEKTRAN)

Due to the hydrophobic nature of lipids, dietary fat is handled differently than protein or carbohydrate with respect with digestion and absorption. Dietary fats are broken down throughout the gastrointestinal system. A unique group of enzymes and cofactors allows this process to proceed in an eff...

384

FIBONACCI LENGTH AND EFFICIENCY IN GROUP PRESENTATIONS  

E-print Network

FIBONACCI LENGTH AND EFFICIENCY IN GROUP PRESENTATIONS Peter Philip Campbell Ph.D. Thesis . . . . . . . . . . . . . 14 2 Introduction to Fibonacci length and generalizations 19 1 Introduction and apology considerations . . . . . . . . . . . . . . . . . 47 3.1 Fibonacci length

St Andrews, University of

385

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

386

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.

1998-01-01

387

Nebular Hydrogen Absorption in the Ejecta of Eta Carinae  

NASA Technical Reports Server (NTRS)

Space Telescope Imaging Spectrograph (STIS) observations of Eta Carinae and immediate ejecta reveal narrow Balmer absorption lines in addition to the nebular-scattered broad P-Cygni absorptions. The narrow absorption correlates with apparent disk structure that separates the two Homunculus lobes. We trace these features about half way up the Northern lobe until the scattered stellar Balmer line doppler-shifts redward beyond the nebular absorption feature. Three-dimensional data cubes, made by mapping the Homunculus at Balmer alpha and Balmer beta with the 52 x 0.1 arcsecond aperture and about 5000 spectral resolving power, demonstrate that the absorption feature changes slowly in velocity with nebular position. We have monitored the stellar Balmer alpha line profile of the central source over the past four years. The equivalent width of the nebular absorption feature changes considerably between observations. The changes do not correlate with measured brightness of Eta Carinae. Likely clumps of neutral hydrogen with a scale size comparable to the stellar disk diameter are passing through the intervening light path on the timescales less than several months. The excitation mechanism involves Lyman alpha radiation (possibly the Lyman series plus Lyman continuum) and collisions leading to populating the 2S metastable state. Before the electron can jump to the ground state by two photon emission (lifetime about 1/8 second), a stellar Balmer photon is absorbed and the electron shifts to an NP level. We see the absorption feature in higher Balmer lines, and but not in Paschen lines. Indeed we see narrow nebular Paschen emission lines. At present, we do not completely understand the details of the absorption. Better understanding should lead to improved insight of the unique conditions around Eta Carinae that leads to these absorptions.

Gull, Theodore R.; Ishibashi, K.; Davidson, K.; Fisher, Richard R. (Technical Monitor)

2000-01-01

388

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

389

Metal and dielectric nanoparticle scattering for improved optical absorption in photovoltaic devices  

E-print Network

length for thin photovoltaic films,1,2 and optical absorp- tion enhancement via scattering from metallicMetal and dielectric nanoparticle scattering for improved optical absorption in photovoltaic scattering by Au and silica nanoparticles placed atop silicon photovoltaic devices on absorption

Yu, Edward T.

390

Genetic-algorithm-based path optimization methodology for spatial decision  

NASA Astrophysics Data System (ADS)

In this paper, we proposed a method based on GA to solve the path-optimization problem. Unlike the traditional methods, it considers many other factors besides the road length including the task assignment and its balance, which are beyond the capability of path analysis and make this problem a Combinatorial Optimization problem. It can't be solved by a traditional graph-based algorithm. This paper proposes a new algorithm that integrates the Graph Algorithm and Genetic Algorithm together to solve this problem. The traditional Graph-Algorithm is responsible for preprocessing data and GA is responsible for the global optimization. The goal is to find the best combination of paths to meet the requirement of time, cost and the reasonable task assignment. The prototype of this problem is named the TSP (Traveling Salesman Problem) problem and known as NP-Hard Problem. However, we demonstrate how these problems are resolved by the GA without complicated programming, the result proves it's effective. The technique presented in this paper is helpful to those GIS developer working on an intelligent system to provide more effective decision-making.

Yu, Liang; Bian, Fuling

2006-10-01

391

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

392

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

393

Optimum gradient of mountain paths.  

PubMed

By combining the experiment results of R. Margaria (Atti Accad. Naz. Lincei Memorie 7: 299-368, 1938), regarding the metabolic cost of gradient locomotion, together with recent insights on gait biomechanics, a prediction about the most economical gradient of mountain paths (approximately 25%) is obtained and interpreted. The pendulum-like mechanism of walking produces a waste of mechanical work against gravity within the gradient range of up to 15% (the overall efficiency is dominated by the low transmission efficiency), whereas for steeper values only the muscular efficiency is responsible for the (slight) metabolic change (per meter of vertical displacement) with respect to gradient. The speeds at the optimum gradient turned out to be approximately 0.65 m/s (+0.16 m/s vertical) and 1.50 m/s (-0.36 m/s vertical), for uphill and downhill walking, respectively, and the ascensional energy expenditure was 0.4 and 2.0 ml O2.kg body mass-1.vertical m-1 climbed or descended. When the metabolic power becomes a burden, as in high-altitude mountaineering, the optimum gradient should be reduced. A sample of real mountain path gradients, experimentally measured, mimics the obtained predictions. PMID:8594031

Minetti, A E

1995-11-01

394

69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER UNDER CONSTRUCTION. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

395

Identifying the primitive path mesh in entangled polymer liquids.  

SciTech Connect

Similar to entangled ropes, polymer chains cannot slide through each other. These topological constraints, the so-called entanglements, dominate the viscoelastic behavior of high-molecular-weight polymeric liquids. Tube models of polymer dynamics and rheology are based on the idea that entanglements confine a chain to small fluctuations around a primitive path which follows the coarse-grained chain contour. To establish the microscopic foundation for these highly successful phenomenological models, we have recently introduced a method for identifying the primitive path mesh that characterizes the microscopic topological state of computer-generated conformations of long-chain polymer melts and solutions. Here we give a more detailed account of the algorithm and discuss several key aspects of the analysis that are pertinent for its successful use in analyzing the topology of the polymer configurations. We also present a slight modification of the algorithm that preserves the previously neglected self-entanglements and allows us to distinguish between local self-knots and entanglements between distant sections of the same chain. Our results indicate that the latter make a negligible contribution to the tube and that the contour length between local self-knots, N{sub 1k} is significantly larger than the entanglement length N{sub e}.

Sukumaran, Sathish K. (Max-Planck-Institut fur Polymerforshung, Postfach, Mainz, Germany); Kremer, Kurt (Max-Planck-Institut fur Polymerforshung, Postfach, Mainz, Germany); Grest, Gary Stephen; Everaers, Ralf (Max-Planck-Institut fur Physik komplexer Systeme, Dresden, Germany)

2004-10-01

396

Height prediction from ulna length.  

PubMed

Height is fundamental to assessing growth and nutrition, calculating body surface area, and predicting pulmonary function in childhood. Its measurement is hindered by muscle weakness, joint, or spinal deformity. Arm span has been used as a substitute, but is inaccurate. The objective of the study was to identify a limb measurement that precisely and reproducibly predicts height in childhood. Males (n=1144) and females (n=1199), aged 5 years 4 months to 19 years 7 months, without disability were recruited from Melbourne schools. Height, arm span, ulna, forearm, tibia, and lower leg lengths were measured with a Harpenden stadiometer and anthropometer. Prediction equations for height based on ulna length (U) and age in years (A) were developed using linear regression. Ulna centile charts were developed by the LMS method. For males, height (cm)=4.605U+1.308A+28.003 (R2=0.96); for females, height (cm)=4.459U+1.315A+31.485 (R2=0.94). Intra- and inter-observer variability was 0.41% and 0.61% relative to the mean, respectively. Height prediction equations from tibia, forearm, and lower leg length were calculated. We show that ulna measurement is reproducible and precisely predicts height in school-age children. It appears to be superior to arm span measurement when neuromuscular weakness, joint, or spinal deformity exists. Ulna growth charts should facilitate growth assessment. PMID:15230461

Gauld, Leanne M; Kappers, Johanna; Carlin, John B; Robertson, Colin F

2004-07-01

397

Estimating the average carbon chain length of saturated fatty acid esters by infrared spectroscopy  

Microsoft Academic Search

The average carbon chain length of saturated fatty acid esters can be determined by comparing absorption intensities in the\\u000a 3.3 and 5.75 ? infrared regions. Data are presented for triglycerides, monoglycerides, and methyl esters. The method was used\\u000a to follow the fractionation of hydrogenated milk fat from acetone, and the average values for fatty acid chain length were\\u000a in good

P. G. Keeney

1962-01-01

398

Evaluation of Multiangle Absorption Photometry for Measuring Aerosol Light Absorption  

Microsoft Academic Search

A new multiangle absorption photometer for the measurement of aerosol light absorption was recently introduced that builds on the simultaneous measurement of radiation transmitted through and scattered back from a particle-loaded fiber filter at multiple detection angles. The absorption coefficient of the filter-deposited aerosol is calculated from the optical properties of the entire filter system, which are determined by a

Andreas Petzold; Herbert Schloesser; Patrick J. Sheridan; W. Patrick Arnott; John A. Ogren; Aki Virkkula

2005-01-01

399

Revealing quantum path details in high-field physics  

NASA Astrophysics Data System (ADS)

The fundamental mechanism underlying harmonic emission in the strong-field regime is governed by tunnel ionization of the atom, followed by the motion of the electron wave packet in the continuum, and finally by its recollision with the atomic core. Due to the quantum nature of the process, the properties of the electron wave packet strongly correlate with those of the emitted radiation. Here, by spatially resolving the interference pattern generated by overlapping the harmonic radiation emitted by different interfering electron quantum paths, we have succeeded in unravelling the intricacies associated with the recollision process. This has been achieved by mapping the spatial extreme-ultraviolet (EUV)-intensity distribution onto a spatial ion distribution, produced in the EUV focal area through the linear and nonlinear processes of atoms. By in situ manipulation of the intensity-dependent motion of the electron wave packets, we have been able to directly measure the difference between the harmonic emission times and electron path lengths resulting from different electron trajectories. Due to the high degree of accuracy that the present approach provides, we have been able to demonstrate the quantum nature of the recollision process. This is done by quantitatively correlating the photoemission time and the electron quantum path-length differences, taking into account the energy-momentum transfer from the driving laser field into the system. This information paves the way for electron-photon correlation studies at the attosecond time scale, while it puts the recollision process from the semiclassical prospective into a full quantum-mechanical context.

Kolliopoulos, G.; Bergues, B.; Schröder, H.; Carpeggiani, P. A.; Veisz, L.; Tsakiris, G. D.; Charalambidis, D.; Tzallas, P.

2014-07-01

400

Direct and quantitative photothermal absorption spectroscopy of individual particulates  

NASA Astrophysics Data System (ADS)

Photonic structures can exhibit significant absorption enhancement when an object's length scale is comparable to or smaller than the wavelength of light. This property has enabled photonic structures to be an integral component in many applications such as solar cells, light emitting diodes, and photothermal therapy. To characterize this enhancement at the single particulate level, conventional methods have consisted of indirect or qualitative approaches which are often limited to certain sample types. To overcome these limitations, we used a bilayer cantilever to directly and quantitatively measure the spectral absorption efficiency of a single silicon microwire in the visible wavelength range. We demonstrate an absorption enhancement on a per unit volume basis compared to a thin film, which shows good agreement with Mie theory calculations. This approach offers a quantitative approach for broadband absorption measurements on a wide range of photonic structures of different geometric and material compositions.

Tong, Jonathan K.; Hsu, Wei-Chun; Eon Han, Sang; Burg, Brian R.; Zheng, Ruiting; Shen, Sheng; Chen, Gang

2013-12-01

401

Absorption spectroscopy of individual single-walled carbon nanotubes  

E-print Network

Current methods for producing single-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 offer the possibility to examine these heterogeneities provided that both SWNT species are equally well detected. Here, we used photothermal heterodyne detection to record absorption images and spectra of individual SWNTs. Because this photothermal method relies only on light absorption, it readily detects metallic nanotubes as well as the emissive semiconducting species. The first and second optical transitions in individual semicontucting nanotubes have been probed. Comparison between the emission and absorption spectra of the lowest-lying optical transition reveal mainly small Stokes shifts. Side bands in the near-infrared absorption spectra are observed and assigned to exciton-phonon bound states. No such sidebands are detected around the lowest transiti...

Berciaud, Stéphane; Poulin, Philippe; Weisman, R Bruce; Lounis, Brahim

2007-01-01

402

Sequential Path Entanglement for Quantum Metrology  

PubMed Central

Path entanglement is a key resource for quantum metrology. Using path-entangled states, the standard quantum limit can be beaten, and the Heisenberg limit can be achieved. However, the preparation and detection of such states scales unfavourably with the number of photons. Here we introduce sequential path entanglement, in which photons are distributed across distinct time bins with arbitrary separation, as a resource for quantum metrology. We demonstrate a scheme for converting polarization Greenberger-Horne-Zeilinger entanglement into sequential path entanglement. We observe the same enhanced phase resolution expected for conventional path entanglement, independent of the delay between consecutive photons. Sequential path entanglement can be prepared comparably easily from polarization entanglement, can be detected without using photon-number-resolving detectors, and enables novel applications.

Jin, Xian-Min; Peng, Cheng-Zhi; Deng, Youjin; Barbieri, Marco; Nunn, Joshua; Walmsley, Ian A.

2013-01-01

403

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

404

The influence of alkane chain length on the skin irritation potential of 1,2-alkanediols.  

PubMed

Several studies have reported that 1,2-alkanediols show increasing anti-microbial activity as their alkane chain length increases. However, there are no reports on the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. To investigate the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. The objective and subjective (sensory) skin irritation potentials of five 1,2-alkanediols - 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol and 1,2-decanediol - were evaluated. We also estimated percutaneous absorption by measuring in vitro skin penetration using a Franz diffusion cell system. Like anti-microbial activity, sensory irritation potential increased as alkane chain length increased, most likely due to increasing membrane interference and/or intrinsic toxicity of 1,2-alkanediols. 1,2-Hexanediol showed the lowest objective skin irritation potential, which increased when the alkane chain length decreased or increased. Furthermore, percutaneous absorption negatively correlated with the alkane chain length of 1,2-alkanediols. These results show that a lower skin absorption potential is not indicative of a low skin irritation potential. Our results suggest that the factors and processes involved in skin irritation potential are complex and that skin irritation potential is influenced by intrinsic toxicity and the potential for penetration or integration in the lipid bilayer. PMID:21585401

Lee, E; An, S; Cho, S-A; Yun, Y; Han, J; Hwang, Y K; Kim, H K; Lee, T R

2011-10-01

405

Optical Scattering Lengths in Large Liquid-Scintillator Neutrino Detectors  

E-print Network

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents PXE, LAB, and Dodecane which are under discussion for next-generation experiments like SNO+, Hanohano, or LENA. Results comprise the wavelength range from 415 to 440nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector.

Wurm, Michael; Goeger-Neff, Marianne; Hofmann, Martin; Lachenmaier, Tobias; Lewke, Timo; Undagoitita, Teresa Marrodan; Meindl, Quirin; Moellenberg, Randoplh; Oberauer, Lothar; Potzel, Walter; Tippmann, Marc; Todor, Sebastian; Traunsteiner, Christoph; Winter, Juergen

2010-01-01

406

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

407

Corrosion Problems in Absorption Chillers  

ERIC Educational Resources Information Center

Absorption chillers use a lithium bromide solution as the medium of absorption and water as the refrigerant. Discussed are corrosion and related problems, tests and remedies, and cleaning procedures. (Author/MLF)

Stetson, Bruce

1978-01-01

408

Steam Path Audits on Industrial Steam Turbines  

E-print Network

steam Path Audits on Industrial steam Turbines DOUGLAS R. MITCHELL. ENGINEER. ENCOTECH, INC., SCHENECTADY, NEW YORK ABSTRACT The electric utility industry has benefitted from steam path audits on steam turbines for several years. Benefits... include the ability to identify areas of performance degradation during a turbine outage. Repair priorities can then be set in accordance with quantitative results from the steam path audit. As a result of optimized repair decisions, turbine...

Mitchell, D. R.

409

Multiphoton Path Entanglement by Nonlocal Bunching  

NASA Astrophysics Data System (ADS)

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.

Eisenberg, H. S.; Hodelin, J. F.; Khoury, G.; Bouwmeester, D.

2005-03-01

410

Multiphoton Path Entanglement by Nonlocal Bunching  

Microsoft Academic Search

Multiphoton path entanglement is created without applying post-selection, by\\u000amanipulating the state of stimulated parametric down-conversion. A specific\\u000ameasurement on one of the two output spatial modes leads to the non-local\\u000abunching of the photons of the other mode, forming the desired multiphoton path\\u000aentangled state. We present experimental results for the case of a heralded\\u000atwo-photon path entangled state

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2005-01-01

411

Multiphoton path entanglement by nonlocal bunching.  

PubMed

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers. PMID:15783951

Eisenberg, H S; Hodelin, J F; Khoury, G; Bouwmeester, D

2005-03-11

412

Walden's Paths quiz: system design and implementation  

E-print Network

assessment io guide instruction, to provide fccdback to students, and to plan for further development ol the path or the Web pages included in the path. Cox and Junkin [13] discuss how instructors can use the results of an automatically evaluated test... Walden's Paths Quiz: System Design and Implementation. (December 2002) Avital Jayant Arora, B. E. , Universiiy of Bombay Chair of Advisory Committee: Dr. Richard Furuta Thts thesis describes the motivation for onlme testing, compares the effectiveness...

Arora, Avital Jayant

2012-06-07

413

Microwave propagation over mountain-diffraction paths  

Microsoft Academic Search

An experimental study was undertaken to obtain a more complete picture of wide-band transmission via microwave propagation over mountain-diffraction paths. Such paths are characterized by obstacles of irregular shape, and pathlength very large compared to wavelength. Swept-frequency transmission was used to provide a record of signal-level variations with time and frequency on two different paths. Other observations included polarization dependence,

A. Carlson

1966-01-01

414

Relic neutrino absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the Universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 1021 eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasidegenerate to optimize the dip, which implies m??0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.

Eberle, Birgit; Ringwald, Andreas; Song, Liguo; Weiler, Thomas J.

2004-07-01

415

Scaling of Avian Primary Feather Length  

Microsoft Academic Search

The evolution of the avian wing has long fascinated biologists, yet almost no work includes the length of primary feathers in consideration of overall wing length variation. Here we show that the length of the longest primary feather () contributing to overall wing length scales with negative allometry against total arm (ta = humerus+ulna+manus). The scaling exponent varied slightly, although

Robert L. Nudds; Gary W. Kaiser; Gareth J. Dyke; Andrew Farke

2011-01-01

416

Length-dependent dynamics of microtubules  

NASA Astrophysics Data System (ADS)

Certain regulatory proteins influence the polymerization dynamics of microtubules by inducing catastrophe with a rate that depends on the microtubule length. Using a discrete formulation, here we show that, for a catastrophe rate proportional to the microtubule length, the steady-state probability distributions of length decay much faster with length than an exponential decay as seen in the absence of these proteins.

Yadav, Vandana; Mukherji, Sutapa

2011-12-01

417

Langevin equation path integral ground state.  

PubMed

We propose a Langevin equation path integral ground state (LePIGS) approach for the calculation of ground state (zero temperature) properties of molecular systems. The approach is based on a modification of the finite temperature path integral Langevin equation (PILE) method (J. Chem. Phys. 2010, 133, 124104) to the case of open Feynman paths. Such open paths are necessary for a ground state formulation. We illustrate the applicability of the method using model systems and the weakly bound water-parahydrogen dimer. We show that the method can lead to converged zero point energies and structural properties. PMID:23738885

Constable, Steve; Schmidt, Matthew; Ing, Christopher; Zeng, Tao; Roy, Pierre-Nicholas

2013-08-15

418

The Logic behind Feynman's Paths  

E-print Network

The classical notions of continuity and mechanical causality are left in order to refor- mulate the Quantum Theory starting from two principles: I) the intrinsic randomness of quantum process at microphysical level, II) the projective representations of sym- metries of the system. The second principle determines the geometry and then a new logic for describing the history of events (Feynman's paths) that modifies the rules of classical probabilistic calculus. The notion of classical trajectory is replaced by a history of spontaneous, random an discontinuous events. So the theory is reduced to determin- ing the probability distribution for such histories according with the symmetries of the system. The representation of the logic in terms of amplitudes leads to Feynman rules and, alternatively, its representation in terms of projectors results in the Schwinger trace formula.

Edgardo T. Garcia Alvarez

2010-11-22

419

Testable scenario for relativity with minimum length  

NASA Astrophysics Data System (ADS)

I propose a general class of spacetimes whose structure is governed by observer-independent scales of both velocity (/c) and length (Planck length), and I observe that these spacetimes can naturally host a modification of FitzGerald-Lorentz contraction such that lengths which in their inertial rest frame are bigger than a ``minimum length'' are also bigger than the minimum length in all other inertial frames. With an analysis in leading order in the minimum length, I show that this is the case in a specific illustrative example of postulates for relativity with velocity and length observer-independent scales.

Amelino-Camelia, G.

2001-06-01

420

Optical absorption in amorphous silicon  

SciTech Connect

The role that disorder plays in shaping the form of the optical absorption spectrum of hydrogenated amorphous silicon is investigated. Disorder leads to a redistribution of states, which both reduces the Tauc gap and broadens the absorption tail. The observed relationship between the Tauc gap and the breadth of the absorption tail is thus explained.

O`Leary, S.K.; Zukotynski, S.; Perz, J.M.; Sidhu, L.S. [Univ. of Toronto, Ontario (Canada). Dept. of Electrical and Computer Engineering

1996-12-31

421

The Length of Time's Arrow  

SciTech Connect

An unresolved problem in physics is how the thermodynamic arrow of time arises from an underlying time reversible dynamics. We contribute to this issue by developing a measure of time-symmetry breaking, and by using the work fluctuation relations, we determine the time asymmetry of recent single molecule RNA unfolding experiments. We define time asymmetry as the Jensen-Shannon divergencebetween trajectory probability distributions of an experiment and its time-reversed conjugate. Among other interesting properties, the length of time's arrow bounds the average dissipation and determines the difficulty of accurately estimating free energy differences in nonequilibrium experiments.

Feng, Edward H.; Crooks, Gavin E.

2008-08-21

422

AMLT - Anisotropic mixing length theory  

NASA Technical Reports Server (NTRS)

The standard mixing length theory (MLT) assumes that the largest eddies are the only ones that contribute to convection and that they are isotropic. These two requirements are internally inconsistent since it is experimentally known that only small eddies are isotropic while large ones exhibit large degrees of anisotropy. A new model called anisotropic MLT (AMLT) is presented here, together with a model that relates the anisotropy to other quantities of the problem. The new AMLT equations are solved for two cases of stellar structure calculations.

Canuto, V. M.

1989-01-01

423

The Length of My Foot  

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "How Big is a Foot" by Rolf Myller and learn about units. Then, learners visit four measurement centers. In each center, learners will measure items with various kinds of units. Learners use non-standard units to measure their shoes, the distance between beanbags and a bullâs-eye target, their body parts (arms, legs, etc.), and some everyday objects. This lesson guide includes instructions on how to set up a "Shoe Store" dramatic play area that can be used to introduce learners to measurement prior to this activity.

Lyman, Nichol

2012-09-26

424

Precision measurement of the n-4He scattering length using neutron interferometry  

NASA Astrophysics Data System (ADS)

The NIST neutron interferometer and optics facility (NIOF) is currently performing a precision measurement of the n-4He scattering length to less than 0.3% relative uncertainty. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons entering the interferometer are Bragg diffracted in the blades to produce two spatially separate yet coherent beam paths much like an optical Mach-Zehnder interferometer. A sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths. This phase difference is directly related to the sample's scattering length. Neutron scattering lengths are one parameter that can be predicted using advanced theoretical models describing two and three nucleon interactions. In an effort to provide tests and/or benchmarks of these theoretical models, the NIOF has already performed precision measurements of neutron scattering lengths to less than 1% relative uncertainty in several low Z gases: H, D, 3He, and polarized 3He. A preliminary result of this work will be given.

Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Black, T. C.; Shahi, C. B.; Wietfeldt, F. E.

2010-11-01

425

Density dependence of electron mean-free paths from low to high energies  

NASA Astrophysics Data System (ADS)

The mean-free path of an electron scattering inelastically in a degenerate electron gas at zero temperature has been calculated, using the dielectric function/self-energy formalism of Ritchie [Phys. Rev. 114, 644 (1959)]. The objective of this work is to model accurately the mean-free path as a function of photoelectron energy and density for use in the calculation of extended x-ray absorption fine structure (EXAFS) [Rev. Mod. Phys. 53, 1 (1981)] of fluids and plasmas whose structure can be described by a radial distribution function. Results are compared with proposed universal mean-free path formulas and it is found that a more generalized version of a power law provides an adequate fit. A table of the best-fit parameters of this law at a range of densities of interest for the EXAFS colliding shock experiments on foil targets is presented.

Gordon, F. I.; Djaoui, A.

1992-12-01

426

Model Checking Almost All Paths Can Be Less Expensive than Checking All Paths  

E-print Network

Model Checking Almost All Paths Can Be Less Expensive than Checking All Paths Matthias Schmalz 1 and nite-state systems, the two notions of smallness coincide. More importantly, they coincide 1 Matthias.Schmalz

Varacca, Daniele - Laboratoire Preuves, Programmes et Systèmes, Université Paris 7

427

Methodology for Augmenting Existing Paths with Additional Parallel Transects  

SciTech Connect

Visual Sample Plan (VSP) is sample planning software that is used, among other purposes, to plan transect sampling paths to detect areas that were potentially used for munition training. This module was developed for application on a large site where existing roads and trails were to be used as primary sampling paths. Gap areas between these primary paths needed to found and covered with parallel transect paths. These gap areas represent areas on the site that are more than a specified distance from a primary path. These added parallel paths needed to optionally be connected together into a single path—the shortest path possible. The paths also needed to optionally be attached to existing primary paths, again with the shortest possible path. Finally, the process must be repeatable and predictable so that the same inputs (primary paths, specified distance, and path options) will result in the same set of new paths every time. This methodology was developed to meet those specifications.

Wilson, John E.

2013-09-30

428

Path Planning Using a Hybrid Evolutionary Algorithm Based on Tree Structure Encoding  

PubMed Central

A hybrid evolutionary algorithm using scalable encoding method for path planning is proposed in this paper. The scalable representation is based on binary tree structure encoding. To solve the problem of hybrid genetic algorithm and particle swarm optimization, the “dummy node” is added into the binary trees to deal with the different lengths of representations. The experimental results show that the proposed hybrid method demonstrates using fewer turning points than traditional evolutionary algorithms to generate shorter collision-free paths for mobile robot navigation. PMID:24971389

Wang, Siao-En; Guo, Jian-Horn

2014-01-01

429

Multi-path light extinction approach for high efficiency filtered oil particle measurement  

NASA Astrophysics Data System (ADS)

This work present a multi-pathlight extinction approach to determine the oil mist filter efficiency based on measuring the concentration and size distribution of oil particles. Light extinction spectrum(LES) technique was used to retrieve the oil particle size distribution and concentration. The multi-path measuring cell was designed to measure low concentration and fine particles after filtering. The path-length of the measuring cell calibrated as 200 cm. The results of oil particle size with oil mist filtering were obtained as D32 = 0.9?m. Cv=1.6×10-8.

Pengfei, Yin; Jun, Chen; Huinan, Yang; Lili, Liu; Xiaoshu, Cai

2014-04-01

430

Path planning using a hybrid evolutionary algorithm based on tree structure encoding.  

PubMed

A hybrid evolutionary algorithm using scalable encoding method for path planning is proposed in this paper. The scalable representation is based on binary tree structure encoding. To solve the problem of hybrid genetic algorithm and particle swarm optimization, the "dummy node" is added into the binary trees to deal with the different lengths of representations. The experimental results show that the proposed hybrid method demonstrates using fewer turning points than traditional evolutionary algorithms to generate shorter collision-free paths for mobile robot navigation. PMID:24971389

Ju, Ming-Yi; Wang, Siao-En; Guo, Jian-Horn

2014-01-01

431

Mid-infrared FEL absorption spectra  

NASA Astrophysics Data System (ADS)

The Vanderbilt Mark III FEL is a tunable source of high- intensity coherent mid-infrared radiation occurring as a train of picosecond pulses spaced 350ps apart. The laser beam is transported to each laboratory under vacuum, but is typically transmitted through some distance of atmosphere before reaching the target. Losses due to absorption by water vapor and CO2 can be large, and since the bandwidth of the FEL is several percent of the wavelength, the spectrum can be altered by atmospheric absorptions. In order to provide an accurate representation of the laser spectrum delivered to the target, and to investigate any non-linear effects associated with transport of the FEL beam, we have recorded the spectrum of the FEL output using a vacuum spectrometer positioned after measured lengths of atmosphere. The spectrometer is equipped with a linear pyroelectric array which provides the laser spectrum for each pulse. Absorption coefficients are being measured for laboratory air, averaged over the bandwidth of the FEL. The high peak powers of this Fel have induced damage in common infrared-transparent materials; we are also measuring damage thresholds for several materials at various wavelengths.

Kozub, John A.; Feng, Bibo; Gabella, William E.

2002-04-01

432

Resynthesis of Combinational Circuts for Path Count Reduction and for Path Delay Fault Testability  

Microsoft Academic Search

Path delay fault model is the most suitable model for detecting distributed manufacturing defects that can cause delay faults. However, the number of paths in a modern design can be extremely large and the path delay testability of many practical designs could be very low. In this paper we show how to resynthesize a combinational circuit in order to reduce

Angela Krstic; Kwang-Ting Cheng

1996-01-01

433

Backup Path Re-optimizations for Shared Path Protection in Multi-domain Networks  

Microsoft Academic Search

Within the context of dynamic routing models for shared path protection in multi-domain networks, we propose a backup path re-optimization phase with possible rerouting of the existing backup paths in order to increase the bandwidth sharing among them while minimizing the network backup cost. The re- optimization phase is activated periodically or when routing a new connection fails because of

B. Jaumard; T. Dieu Linh Truong

2006-01-01

434

Air flow and length noise in displacement interferometry  

NASA Astrophysics Data System (ADS)

We report on an evaluation of the influence that fast changes of the refractive index has on the uncertainty of interferometric displacement measurement. Measurement of position within a limited range is typical for coordinate measuring systems such as nanometrology standards combining scanning probe microscopy (SPM) with precise positioning. For long-range systems the varying refractive index of air contributes the most to the overall uncertainty. We proposed to extend the principle of compensation of the fluctuations of the refractive index of air through monitoring the optical length within the measuring range of the displacement measuring interferometer. In this contribution we evaluate the level of uncertainty associated with the nature of the fluctuations of the refractive index of air in laser interferometry. We have observed that its fast variations, seen as length noise, are not linearly proportional to the measuring beam path but play a significant role only over distances longer than 50 mm. Over longer distances the length noise rises proportionally. The measurements were performed under conditions typical for metrology SPM systems.

Holá, Miroslava; ?íp, Ond?ej; Sarbort, Martin; Lazar, Josef

2015-01-01

435

Infrared neural stimulation: beam path in the guinea pig cochlea  

PubMed Central

It has been demonstrated INS can be utilized to stimulate spiral ganglion cells in the cochlea. Although neural stimulation can be achieved without direct contact of the radiation source and the tissue, the presence of fluids or bone between the target structure and the radiation source may lead to absorption or scattering of the radiation, which may limit the efficacy of INS. The present study demonstrates the neural structures in the radiation beam path that can be stimulated. Histological reconstructions and microCT of guinea pig cochleae stimulated with an infrared laser suggest that the orientation of the beam from the optical fiber determined the site of stimulation in the cochlea. Best frequencies of the INS-evoked neural responses obtained from the central nucleus of the inferior colliculus matched the histological sites in the spiral ganglion. PMID:21763410

Moreno, Laura E; Rajguru, Suhrud M; Matic, Agnella Izzo; Yerram, Nitin; Robinson, Alan M; Hwang, Margaret; Stock, Stuart; Richter, Claus-Peter

2011-01-01

436

Absorption heat pumps  

NASA Astrophysics Data System (ADS)

The aim of the study was to analyze the technical and economic feasibility of absorption heat pumps in Finland. The work was done as a case study: the technical and economic analyses have been carried out for six different cases, where in each the suitable size and type of the heat pump plant and the auxiliary components and connections were specified. The study also detailed the costs concerning the procurement, installation and test runs of the machinery, as well as the savings in energy costs incurred by the introduction of the plant. Conclusions were drawn of the economic viability of the applications studied. The following cases were analyzed: heat recovery from flue gases and productin of district heat in plants using peat, natural gas, and municipal wastes as a fuel. Heat recovery in the pulp and paper industry for the upgrading of pressure of secondary steam and for the heating of white liquor and combustion and drying the air. Heat recovery in a peat-fulled heat and power plant from flue gases that have been used for the drying of peat. According to the study, the absorption heat pump suits best to the production of district heat, when the heat source is the primary energy is steam produced by the boiler. Included in the flue as condensing is the purification of flue gases. Accordingly, benefit is gained on two levels in thick applications. In heat and power plants the use of absorption heat pumps is less economical, due to the fact that the steam used by the pump reduces the production of electricity, which is rated clearly higher than heat.

Huhtinen, M.; Heikkilae, M.; Andersson, R.

1987-03-01

437

Energetic Path Finding Across Massive Terrain Data  

E-print Network

Energetic Path Finding Across Massive Terrain Data Andrew Tsui and Zo¨e Wood California Polytechnic of this work include: ­ Tools for managing and performing energetic analysis on massive out-of- core datasets builds on two previous projects involving human centered paths across terrain data, Energetic Analyst [5

Wood, Zoë J.

438

Career path of a corruption entrepreneur  

Microsoft Academic Search

The study of criminal career paths is necessary to understand the methods of success employed by high-performing criminals. The aim of this article is to focus on the career path of Jack Herbert who set up and maintained extensive corruption networks between organised crime groups and police in the Australian state of Queensland. This study builds on Morselli's work on

Mark Lauchs; Zoe Staines

2012-01-01

439

Asymmetric fluctuation relaxation paths in FPU models  

NASA Astrophysics Data System (ADS)

A recent theory by Bertini, De Sole, Gabrielli, Jona-Lasinio and Landim predicts a temporal asymmetry in the fluctuation-relaxation paths of certain observables of nonequilibrium systems in local thermodynamic equilibrium. We find temporal asymmetries in the fluctuation-relaxation paths of a form of local heat flow, in the nonequilibrium FPU- ? model of Lepri, Livi and Politi.

Giberti, C.; Rondoni, L.; Vernia, C.

2006-06-01

440

Finding Regular Simple Paths in Graph Databases  

Microsoft Academic Search

We consider the following problem: given a labelled directed graph and a regular expression , find all pairs of nodes connected by a simple path such that theconcatenation of the labels along the path satisfies . The problem is motivated by the observation that many recursive queries in relational databases can be expressed in this form, and by the implementation

Alberto O. Mendelzon; Peter T. Wood

1989-01-01

441

Adaptively Ubiquitous Learning in Campus Math Path  

ERIC Educational Resources Information Center

The purposes of this study are to develop and evaluate the instructional model and learning system which integrate ubiquitous learning, computerized adaptive diagnostic testing system and campus math path learning. The researcher first creates a ubiquitous learning environment which is called "adaptive U-learning math path system". This system…

Shih, Shu-Chuan; Kuo, Bor-Chen; Liu, Yu-Lung

2012-01-01

442

Katrina'sPath Lake Pontchartrain  

E-print Network

'sPath Katrina's Storm Surge #12;Now Scenario Hurricane Toufectis · Approaches from the ESE, traveling WNW · SSC to Katrina #12;Gotwals'Path Now Scenario Hurricane Gotwals · Katrina is as Katrina was · Storm track moved 4 Hurricane Horton · Katrina is as Katrina was · Adding roughly 10" sea level rise (25cm) Impacts · Similar

443

Intestinal absorption of vitamins.  

PubMed

This article provides an overview of advances in understanding the cellular and molecular mechanisms and regulation of intestinal absorption processes of vitamins. The vitamins covered are the water-soluble vitamins folic acid, cobalamin (vitamin B12), biotin, pantothenic acid, and thiamine (vitamin B1) and the lipid-soluble vitamin A. For folate, significant advances have been made in regard to i) digestion of dietary folate polyglutamates to folate monoglutamates by the cloning of the responsible enzyme; ii) identification of the cDNA responsible for the intestinal folate transporter; iii) delineation of intracellular mechanisms that regulate small intestinal folate uptake; and iv) identification and characterization of a specific, pH-dependent, carrier-mediated system for folate uptake at the luminal (apical) membrane of human colonocytes. Studies on cobalamine have focused on cellular and molecular characterization of the intrinsic factor and its receptor. Studies on biotin transport in the small intestine have shown that the uptake process is shared by another water-soluble vitamin, pantothenic acid. Furthermore, a Na-dependent, carrier-mediated biotin uptake system that is also shared with pantothenic acid has been identified at the apical membrane of human colonocytes. This carrier is believed to be responsible for the absorption of the bacterially synthesized biotin and pantothenic acid in the large intestine. Also, preliminary studies have reported the cloning of a biotin transporter from the small intestine. As for thiamine intestinal transport, a study has shown thiamine uptake by small intestinal biopsy specimens to be via a carrier-mediated, Na-independent mechanism, which appears to be up-regulated in thiamine deficiency. Studies on vitamin A intestinal absorption have shown the existence of a receptor-mediated mechanism for the uptake of retinol bound to retinol-binding protein in the small intestine of suckling rats. Another study has shown that retinoic acid increases the mRNA level of the cellular retinol binding protein II and the rate of retinol uptake by Caco-2 intestinal epithelial cells. The study suggested that retinoids may play a role in the regulation of vitamin A intestinal absorption. PMID:17023940

Said, H M; Kumar, C

1999-03-01

444

Scattering with absorptive interaction  

NASA Astrophysics Data System (ADS)

The S matrix for a wide class of complex and nonlocal potentials is studied, with special attention given to the motion of singularities in the complex k plane as a function of the imaginary coupling strength. Modifications of Levinson's theorem are obtained and discussed. Analytic approximations to the S matrix in the vicinity of narrow resonances are exhibited and compared to numerical results of resonating-group calculations. The problem of defining resonances in the case of complex interactions is discussed, making contact with the usual analysis of scattering in terms of Argand diagrams. NUCLEAR REACTIONS Scattering theory, S matrix for absorptive potentials.

Cassing, W.; Stingl, M.; Weiguny, A.

1982-07-01

445

Antiproton Absorption in Nuclei  

E-print Network

We present the analysis of experimental data on forward antiproton production on nuclei. The calculations are done in the framework of a folding model which takes properly into account both incoherent direct proton-nucleon and cascade pion-nucleon antiproton production processes as well as internal nucleon momentum distribution. The effective antiproton-nucleon cross section in nuclear matter and the imaginary part of the antiproton nuclear optical potential are estimated to be 25-45 mb and -(38-56) MeV at normal nuclear matter density, respectively. The results of the performed analysis evidence for the decreasing of antiproton absorption in the nuclear medium.

Yu. T. Kiselev; E. Ya. Paryev

2006-01-11

446

Saturable absorption of intense hard X-rays in iron  

NASA Astrophysics Data System (ADS)

In 1913, Maurice de Broglie discovered the presence of X-ray absorption bands of silver and bromine in photographic emulsion. Over the following century, X-ray absorption spectroscopy was established as a standard basis for element analysis, and further applied to advanced investigation of the structures and electronic states of complex materials. Here we show the first observation of an X-ray-induced change of absorption spectra of the iron K-edge for 7.1-keV ultra-brilliant X-ray free-electron laser pulses with an extreme intensity of 1020?W?cm?2. The highly excited state yields a shift of the absorption edge and an increase of transparency by a factor of 10 with an improvement of the phase front of the transmitted X-rays. This finding, the saturable absorption of hard X-rays, opens a promising path for future innovations of X-ray science by enabling novel attosecond active optics, such as lasing and dynamical spatiotemporal control of X-rays.

Yoneda, Hitoki; Inubushi, Yuichi; Yabashi, Makina; Katayama, Tetsuo; Ishikawa, Tetsuya; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru

2014-10-01

447

Study on optical weak absorption of borate crystals  

NASA Astrophysics Data System (ADS)

Borate crystal is an important type of nonlinear optical crystals used in frequency conversion in all-solid-state lasers. Especially, LiB3O5 (LBO), CsB3O5 (CBO) and CsLiB6O10 (CLBO) are the most advanced. Although these borate crystals are all constructed by the same anionic group-(B3O7)5-, they show different nonlinear optical properties. In this study, bulk weak absorption values of three borate crystals have been studied at 1064 nm by a photothermal common-path interferometer. The bulk weak absorption values of them along [1 0 0], [0 1 0] and [0 0 1] directions were obtained, respectively, to be approximately 17.5 ppm cm-1, 15 ppm cm-1 and 20 ppm cm-1 (LBO); 80 ppm cm-1, 100 ppm cm-1 and 40 ppm cm-1 (CBO); 600 ppm cm-1, 600 ppm cm-1 and 150 ppm cm-1 (CLBO) at 1064 nm. The results showed an obvious discrepancy of the values of these crystals along three axis directions. A correlation between the bulk weak absorption property and crystal intrinsic structure was then discussed. It is found that the bulk weak absorption values strongly depend on the interstitial area surrounded by the B-O frames. The interstitial area is larger, the bulk weak absorption value is higher.

Li, Xiaomao; Hu, Zhanggui; Yue, Yinchao; Yu, Xuesong; Lin, Zheshuai; Zhang, Guochun

2013-10-01

448

Saturable absorption of intense hard X-rays in iron.  

PubMed

In 1913, Maurice de Broglie discovered the presence of X-ray absorption bands of silver and bromine in photographic emulsion. Over the following century, X-ray absorption spectroscopy was established as a standard basis for element analysis, and further applied to advanced investigation of the structures and electronic states of complex materials. Here we show the first observation of an X-ray-induced change of absorption spectra of the iron K-edge for 7.1-keV ultra-brilliant X-ray free-electron laser pulses with an extreme intensity of 10(20)?W?cm(-2). The highly excited state yields a shift of the absorption edge and an increase of transparency by a factor of 10 with an improvement of the phase front of the transmitted X-rays. This finding, the saturable absorption of hard X-rays, opens a promising path for future innovations of X-ray science by enabling novel attosecond active optics, such as lasing and dynamical spatiotemporal control of X-rays. PMID:25270525

Yoneda, Hitoki; Inubushi, Yuichi; Yabashi, Makina; Katayama, Tetsuo; Ishikawa, Tetsuya; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru

2014-01-01

449

X-Ray Absorption Fine Structure Applied to Ferroelectrics  

NASA Astrophysics Data System (ADS)

This chapter is devoted to explaining the foundation and merits of the application of synchrotron radiation for studying the X-ray absorption fine structure (XAFS) in ferroelectric materials. XAFS in the local order allows the follows: determining the oxidation states, interatomic distances, Debye-Waller factors and the coordination number of atoms at the first few shells around the absorbing atom, up to 0.5 nm. The text explains the features of the photoelectric effect, as well as its relationship with the absorption edges of each element. Applying the Fermi's Golden Rule, it is explained that the fine structure of absorption edge spectra is the result of the interference of the photoelectron single- and multiple-scattering. This gives rise to the effects of X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS). The content includes significant effects for the study of ferroelectric materials in XANES: energy shift of the edge position, pre-edge transitions and white-lines. Subsequently, the experimental methods and EXAFS spectra processing, by both empirical methods and theoretical models with multiple scattering paths, are presented. Finally, we offer some works representing XAFS applied to ferroelectrics, from the explanation of the displacive or order-disorder nature of the materials PbTiO3 and BaTiO3, to those dedicated to relaxors and Aurivillius oxides.

Cabrera, Maria Elena Montero

450

Converging towards the optimal path to extinction  

PubMed Central

Extinction appears ubiquitously in many fields, including chemical reactions, population biology, evolution and epidemiology. Even though extinction as a random process is a rare event, its occurrence is observed in large finite populations. Extinction occurs when fluctuations owing to random transitions act as an effective force that drives one or more components or species to vanish. Although there are many random paths to an extinct state, there is an optimal path that maximizes the probability to extinction. In this paper, we show that the optimal path is associated with the dynamical systems idea of having maximum sensitive dependence to initial conditions. Using the equivalence between the sensitive dependence and the path to extinction, we show that the dynamical systems picture of extinction evolves naturally towards the optimal path in several stochastic models of epidemics. PMID:21571943

Schwartz, Ira B.; Forgoston, Eric; Bianco, Simone; Shaw, Leah B.

2011-01-01

451

A clinical path for adult diabetes.  

PubMed

The use of clinical paths for patient care management was explored by this development team as a mechanism to provide consistent, high-quality care to hospitalized patients in high-volume, high-risk diagnostic categories. Reviewing the historical aspects and importance of clinical paths helped expand the team's perspective to incorporate pre- and posthospitalization phases of patient care into the clinical path being developed. A multidisciplinary team of physicians, nurses, health educators, and dietitians from both inpatient and outpatient departments of Kaiser-Santa Teresa Medical Center in San Jose, California, devised and implemented an Adult Diabetes Mellitus care path. Staff education preceded the implementation of the care paths. Measurements of quality indicators showed improvements in patient satisfaction, patient education, patient knowledge, and nutrition assessments. PMID:9416030

Courtney, L; Gordon, M; Romer, L

1997-01-01

452

Absorption spectra of liquid water and aqueous buffers between 0.3 and Department of Physics, University of California, Santa Barbara, California 93106  

E-print Network

Absorption spectra of liquid water and aqueous buffers between 0.3 and 3.72 THz Jing Xua Department-dependent terahertz absorption with attenuation lengths on the order of tens of micrometers. To access this spectral.5 THz, these studies provide a well- documented absorption spectrum for liquid water, at approxi- mately

Xu, Jing

453

Bergman Kernel from Path Integral  

NASA Astrophysics Data System (ADS)

We rederive the expansion of the Bergman kernel on Kähler manifolds developed by Tian, Yau, Zelditch, Lu and Catlin, using path integral and perturbation theory, and generalize it to supersymmetric quantum mechanics. One physics interpretation of this result is as an expansion of the projector of wave functions on the lowest Landau level, in the special case that the magnetic field is proportional to the Kähler form. This is relevant for the quantum Hall effect in curved space, and for its higher dimensional generalizations. Other applications include the theory of coherent states, the study of balanced metrics, noncommutative field theory, and a conjecture on metrics in black hole backgrounds discussed in [24]. We give a short overview of these various topics. From a conceptual point of view, this expansion is noteworthy as it is a geometric expansion, somewhat similar to the DeWitt-Seeley-Gilkey et al short time expansion for the heat kernel, but in this case describing the long time limit, without depending on supersymmetry.

Douglas, Michael R.; Klevtsov, Semyon

2010-01-01

454

Biological path to nanoelectronics devices  

NASA Astrophysics Data System (ADS)

The biology and semiconductor technology have progressed independently. There was a large distance between them and a substantial interdisciplinary research area was left untouched. Recently, this situation is changing. Some researchers are stimulating semiconductor technology to introduce bio-molecules into the nano-fabrication process. We proposed a new process for fabricating functional nano-structure on a solid surface using protein supramolecules, which is named "Bio Nano Process" (BNP). We employed a cage-shaped protein, apoferritin and synthesized several kinds of nanoparticles (NP) in the apoferritin cavity. A two-dimensional array of them was made on the silicon wafer and this array was heat treated or UV/ozone treated. These processes produced a two-dimensional inorganic NP array on the silicon surface. The size of NP is small enough as quantum dots and the floating nanodots memory using this NP array is now under development. We also proposed another process using the obtained nanodot array as the nanometric etching mask. This was realized by the neutral beam etching and 7nm Si nano columns with high aspect ratio were fabricated. These experimental results demonstrated that the BNP can fabricate the inorganic nanostructure using protein supramolecules and the BNP opened up a biological path to nanoelectronics devices.

Yamashita, Ichiro

2005-02-01

455

Path integral for inflationary perturbations  

NASA Astrophysics Data System (ADS)

The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anticommuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level three-point and four-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.

Prokopec, Tomislav; Rigopoulos, Gerasimos

2010-07-01

456

Path Integral for Inflationary Perturbations  

E-print Network

The quantum theory of cosmological perturbations in single field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anti-commuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level 3-point and 4-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.

Tomislav Prokopec; Gerasimos Rigopoulos

2010-12-11

457

Path integral for inflationary perturbations  

SciTech Connect

The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anticommuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level three-point and four-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.

Prokopec, Tomislav [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht (Netherlands); Rigopoulos, Gerasimos [Helsinki Institute of Physics, P.O. Box 64, FIN-00014, University of Helsinki (Finland)

2010-07-15

458

Decision paths in complex tasks  

NASA Technical Reports Server (NTRS)

Complex real world action and its prediction and control has escaped analysis by the classical methods of psychological research. The reason is that psychologists have no procedures to parse complex tasks into their constituents. Where such a division can be made, based say on expert judgment, there is no natural scale to measure the positive or negative values of the components. Even if we could assign numbers to task parts, we lack rules i.e., a theory, to combine them into a total task representation. We compare here two plausible theories for the amalgamation of the value of task components. Both of these theories require a numerical representation of motivation, for motivation is the primary variable that guides choice and action in well-learned tasks. We address this problem of motivational quantification and performance prediction by developing psychophysical scales of the desireability or aversiveness of task components based on utility scaling methods (Galanter 1990). We modify methods used originally to scale sensory magnitudes (Stevens and Galanter 1957), and that have been applied recently to the measure of task 'workload' by Gopher and Braune (1984). Our modification uses utility comparison scaling techniques which avoid the unnecessary assumptions made by Gopher and Braune. Formula for the utility of complex tasks based on the theoretical models are used to predict decision and choice of alternate paths to the same goal.

Galanter, Eugene

1991-01-01

459

Accurate laser measurements of ozone absorption cross-sections in the Hartley band  

NASA Astrophysics Data System (ADS)

Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 × 10-18 cm2 molecule-1 with an expanded relative uncertainty of 0.84 %. This is lower than the conventional value currently in use and measured by Hearn in 1961 with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross sections with reduced uncertainties, a system to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier Transform Infrared spectroscopy was setup. This resulted in new measurements of absolute values of ozone absorption cross sections of 9.48 × 10-18, 10.44 × 10-18, and 11.07 × 10-18 cm2 molecule-1, with relative expanded uncertainties better than 0.6%, for the wavelengths (in vacuum) of 244.062, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non UV photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

Viallon, J.; Lee, S.; Moussay, P.; Tworek, K.; Petersen, M.; Wielgosz, R. I.

2014-08-01

460

Novel In-situ Calibrations for Open-path Ammonia Sensing  

NASA Astrophysics Data System (ADS)

As a major gas phase precursor of fine particulate matter, ammonia plays an important role in the nitrogen cycle. However, its concentration is rather poorly quantified due to various measurement challenges. Open-path detection addresses the sampling issue caused by surface affinity of ammonia and greatly simplifies the sensor design. We have developed an open-path ammonia sensor using a quantum cascade (QC) laser at 9.06 ?m. The sensor has been deployed in 2010 CALNEX campaign in Bakersfield, CA and locally in Princeton in July 2011. The sensor achieved a field detection limit of 1 ppbv ammonia at 1 Hz. Open-path measurements avoid the common sampling problems and biases for ammonia, but ultimately one needs to enclose the open-path system for calibration. To this end, an off-line spectroscopic method to calibrate the ammonia signal was successfully used in CALNEX using ethylene, a stable, relatively inert gas. Ethylene occurs at ambient pptv atmospheric mixing ratios and does thus not cause interference at ambient conditions. However, at much higher concentrations used to calibrate, ethylene exhibits a significant absorption feature that is just offset spectrally from the ammonia absorption feature but comparable in size and thus can serve as a reference absorption signal for ammonia. The open-path QC ammonia measurements intercompared well with ion chromatography measurements in the 5-35 ppbv range. Line shape parameters of both ammonia and ethylene were measured experimentally to confirm the spectroscopic reference calibration technique, and the results were within 10% of HITRAN values over a range of 265-300 K and 10-1000 hPa. Wavelength modulation spectroscopy (WMS) is used in the sensor to enhance the sensitivity as a baseline-free sensing technique. A numerical model was developed to simulate and validate the WMS signals with the experimental spectroscopic data. Model simulations indicate that the 2f WMS signal magnitude for ammonia is largely invariant to pressure and temperature changes. A 2.5 cm reduced pressure in-line ethylene calibration cell was simulated by the WMS model with the goal of in-situ, continuous calibrations for our open-path system. The simulation indicates that ambient ammonia spectra have little interference (<1% over 0-100 ppbv NH3) on the ethylene 2f reference signal when a novel dual modulation is performed. This in-line ethylene calibration technique enables open-path and continuous calibration methods for atmospheric ammonia, and experimental and field results will be demonstrated.

Sun, K.; Tao, L.; Miller, D. J.; Khan, M. A.; Zondlo, M. A.

2011-12-01

461

Precision Neutron Scattering Length Measurements Using Neutron Interferometry  

NASA Astrophysics Data System (ADS)

The neutron interferometer, pioneered by Werner and Rauch in the 1970's, splits the neutron matter wave into two paths by Bragg diffraction in a perfect silicon crystal, then recombines them coherently to produce a interference signal measured by a neutron counter, thereby directly obtaining an interaction amplitude via the phase shift. It has been used to make famous demonstrations of quantum phenomena that are now found in many textbooks. It is also an ideal instrument for precision measurement of low-energy neutron scattering lengths that are important for developing and testing nuclear potential models and effective field theories, and probing neutron substructure. I will describe previous experiments and the current program at the NIST Neutron Interferometry and Optics Facility.

Wietfeldt, Fred

2008-10-01