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1

Light absorption cell combining variable path and length pump  

DOEpatents

This invention is comprised of 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, W.S.

1992-12-31

2

Using integrating spheres as absorption cells: path-length distribution and application of Beer's law  

Microsoft Academic Search

We have modeled the path-length distribution in an integrating sphere used as a multipass optical cell for absorption measurements. The measured radiant flux as a function of analyte concentration is nonlinear as a result, deviating from that expected for a single path length. We have developed a full numerical model and introduce a new analytical relationship that describes this behavior

Jane Hodgkinson; Dackson Masiyano; Ralph P. Tatam

2009-01-01

3

Effective optical path length investigation for cubic diffuse cavity as gas absorption cell  

NASA Astrophysics Data System (ADS)

A simple cubic-shaped cavity with a high-diffuse-reflectivity inner coating as a novel gas detection cell was developed. 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. The law for a spherical cavity was applied and modified to a cubic cavity as a function of reflectivity ?, port fraction f, and the side length. Single-pass average path length of the cubic cavity was 0.723(7) times the side length. EOPL can be modified conveniently by adjusting the parameters of the cavity.

Yu, Jia; Zheng, Fu; Gao, Qiang; Li, Yinjie; Zhang, Yungang; Zhang, Zhiguo; Wu, Shaohua

2013-10-01

4

Variable path length spectrophotometric probe  

DOEpatents

This invention consists of 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, P.E.; McCarty, J.E.; Haggard, R.A.

1991-12-31

5

Variable path length spectrophotometric probe  

DOEpatents

This invention consists of 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, P.E.; McCarty, J.E.; Haggard, R.A.

1991-01-01

6

UV Laser Long-Path Absorption Spectroscopy.  

National Technical Information Service (NTIS)

Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained ...

H. Dorn T. Brauers R. Neuroth

1994-01-01

7

Free Path Lengths in Quasi Crystals  

NASA Astrophysics Data System (ADS)

The Lorentz gas is a model for a cloud of point particles (electrons) in a distribution of scatterers in space. The scatterers are often assumed to be spherical with a fixed diameter d, and the point particles move with constant velocity between the scatterers, and are specularly reflected when hitting a scatterer. There is no interaction between point particles. An interesting question concerns the distribution of free path lengths, i.e. the distance a point particle moves between the scattering events, and how this distribution scales with scatterer diameter, scatterer density and the distribution of the scatterers. It is by now well known that in the so-called Boltzmann-Grad limit, a Poisson distribution of scatterers leads to an exponential distribution of free path lengths, whereas if the scatterer distribution is periodic, the free path length distribution asymptotically behaves as a power law. This paper considers the case when the scatters are distributed on a quasi crystal, i.e. non periodically, but with a long range order. Simulations of a one-dimensional model are presented, showing that the quasi crystal behaves very much like a periodic crystal, and in particular, the distribution of free path lengths is not exponential.

Wennberg, Bernt

2012-06-01

8

Path-length-resolved optical Doppler perfusion monitoring.  

PubMed

We report the first path-length-resolved perfusion measurements on human skin measured with a phase-modulated low-coherence Mach-Zehnder interferometer with spatially separated fibers for illumination and detection. Optical path lengths of Doppler shifted and unshifted light and path-length-dependent Doppler broadening of multiply scattered light from skin are measured from the Doppler broadened interference peaks appearing in the power spectrum. Perfusion and its variations during occlusion are measured in real time for a given optical path length, and the results are compared with the perfusion signal obtained with a conventional laser Doppler perfusion monitor. PMID:18163803

Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G; Steenbergen, Wiendelt

9

On the Joint Path Lengths Distribution in Random Binary Trees  

Microsoft Academic Search

During the 10th Seminar on Analysis of Algorithms, MSRI, Berkeley, June 2004, Knuth posed the problem of analyzing the left and the right path length in a random binary trees. In particular, Knuth asked about properties of the generating function of the joint distribution of the left and the right path lengths. In this paper, we mostly focus on the

Charles Knessl; Wojciech Szpankowski

2005-01-01

10

Unobtrusive interferometer tracking by path length oscillation for multidimensional spectroscopy.  

PubMed

We track the path difference between interferometer arms with few-nanometer accuracy without adding optics to the beam path. We measure the interference of a helium-neon beam that copropagates through the interferometer with midinfrared pulses used for multidimensional spectroscopy. This can indicate motion, but not direction. By oscillating the path length of one arm with a mirror on a piezoelectric stack and monitoring the oscillations of the recombined helium-neon beam, the direction can be calculated, and the path delay can be continuously tracked. PMID:19654639

Lee, Kevin F; Bonvalet, Adeline; Nuernberger, Patrick; Joffre, Manuel

2009-07-20

11

Path lengths, correlations, and centrality in temporal networks  

NASA Astrophysics Data System (ADS)

In temporal networks, where nodes interact via sequences of temporary events, information or resources can only flow through paths that follow the time ordering of events. Such temporal paths play a crucial role in dynamic processes. However, since networks have so far been usually considered static or quasistatic, the properties of temporal paths are not yet well understood. Building on a definition and algorithmic implementation of the average temporal distance between nodes, we study temporal paths in empirical networks of human communication and air transport. Although temporal distances correlate with static graph distances, there is a large spread, and nodes that appear close from the static network view may be connected via slow paths or not at all. Differences between static and temporal properties are further highlighted in studies of the temporal closeness centrality. In addition, correlations and heterogeneities in the underlying event sequences affect temporal path lengths, increasing temporal distances in communication networks and decreasing them in the air transport network.

Pan, Raj Kumar; Saramäki, Jari

2011-07-01

12

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

13

Limited-path-length entanglement percolation in quantum complex networks  

NASA Astrophysics Data System (ADS)

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

Cuquet, Martí; Calsamiglia, John

2011-03-01

14

Path lengths, correlations, and centrality in temporal networks.  

PubMed

In temporal networks, where nodes interact via sequences of temporary events, information or resources can only flow through paths that follow the time ordering of events. Such temporal paths play a crucial role in dynamic processes. However, since networks have so far been usually considered static or quasistatic, the properties of temporal paths are not yet well understood. Building on a definition and algorithmic implementation of the average temporal distance between nodes, we study temporal paths in empirical networks of human communication and air transport. Although temporal distances correlate with static graph distances, there is a large spread, and nodes that appear close from the static network view may be connected via slow paths or not at all. Differences between static and temporal properties are further highlighted in studies of the temporal closeness centrality. In addition, correlations and heterogeneities in the underlying event sequences affect temporal path lengths, increasing temporal distances in communication networks and decreasing them in the air transport network. PMID:21867255

Pan, Raj Kumar; Saramäki, Jari

2011-07-18

15

In-situ Measurements of Tropospheric Hydroxyl Radicals by Folded Long-Path Laser Absorption During the Field Campaign POPCORN  

Microsoft Academic Search

Absolutely calibrated in-situ measurements of tropospheric hydroxyl radicals, formaldehyde, sulfur dioxide, and naphthalene (C10H8) were performed by long-path laser absorption spectroscopy during the field campaign POPCORN. The absorption light path was folded into an open optical multiple reflection cell with a mirror separation of 38.5 m. Using a light path length of 1848 m and an integration time of 200

Uwe Brandenburger; Theo Brauers; Hans-Peter Dorn; Martin Hausmann; Dieter H. Ehhalt

1998-01-01

16

Air pollution monitoring with a computer-controlled CO 2 -laser long-path absorption system  

Microsoft Academic Search

A CO2-laser long-path absorption system has been developed. It is highly automated with computer-controlled laser-line selection and real-time data processing. The system has been used to monitor ethylene and vinyl chloride concentrations over a petrochemical factory area. The ethylene concentrations ranged from below 0.02 ppm to 45 ppm. The vinyl chloride concentrations were less than 0.05 ppm. Different path lengths

B. Marthinsson; J. Johansson; S. T. Eng

1980-01-01

17

Common path endoscopic optical coherence tomography with outside path length compensation  

NASA Astrophysics Data System (ADS)

Endoscopic optical coherence tomography (OCT) allowing high-resolution imaging of internal tissue is attractive for medical imaging. Fibre, fibre bundle or GRIN lens rod acting as endoscopic probe is placed in the sample arm of a Michelson interferometer in current endoscopic OCT systems, this arrangement has to be carefully configured to avoid dispersion and polarization fading. In this study, a common path OCT system with outside path length compensation is presented. The system based on Fizeau configuration requires a Michelson interferometer to compensate the optical path difference between the reference and signal light in the Fizeau sensing interferometer. Experiments of path length compensation and vibration are conducted, and the results demonstrate that this outside compensation method is feasible and the system is immune to the vibration which occurs at the Fizeau sensing interferometer. This OCT imaging approach is very suitable for endoscopic imaging and detailed endoscopic OCT system is also presented. Several samples were imaged to demonstrate the performance of the proposed OCT system.

Yang, Yaliang; Ding, Zhihua; Meng, Jie; Wu, Lan; He, Zi"ang; Wu, Tong; Chen, Minghui

2007-10-01

18

High-speed simulation of skin spectral reflectance based on an optical path-length matrix method and its application  

NASA Astrophysics Data System (ADS)

In this paper, we propose optical path-length matrix method for high-speed simulation of photon migration in human skin. The optical path-length matrix is defined as the probability density distribution of optical pathlength in the skin. Generally, Monte Carlo simulation is used to simulate a skin reflectance, since it can simulate the reflectance accurately. However, it requires a huge computation time, thus this is not easily applicable in practical imaging system with large number of pixels. On the other hand, the proposed optical path-length matrix method achieves the simulation in shorter time. The skin model was assumed to be two-layered media of the epidermal and dermal layers. For obtaining the path-length matrix, photon migration in the model without any absorption was simulated only once by Monte Carlo simulation for each wavelength, and the probabilistic density histograms of the optical path-length at each layer were acquired and stored in the optical path-length matrix. Skin spectral reflectance for arbitrary absorption can be calculated easily by accumulating all combination of an element in the above pre-recomputed path-length matrix and absorption coefficient based on the Beer-Lambert law. Our proposed method was compared with the conventional Monte Carlo simulation. Computational time of the proposed method was approximately two minutes; while that of the conventional method was 15 hours. In addition, error margin of the proposed method was approximately less than 1.6%. This method would applied to skin spectral image analysis for skin chromophore quantification.

Fujiwara, Izumi; Yamamoto, Satoshi; Yamauchi, Midori; Ogawa-Ochiai, Keiko; Nakaguchi, Toshiya; Tsumura, Norimichi

2011-02-01

19

Path length determines the tunneling decay of substituted carbenes.  

PubMed

Quantum mechanical tunneling of atoms allows chemical reactions to proceed through barriers too high for thermally activated processes. This causes hydroxycarbenes to decay rapidly and at a temperature-independent rate even at 11 K. In methylhydroxycarbene, tunneling causes decay through a mechanism that reveals a high but thin barrier rather than an alternative with a lower but broader barrier. No accurate estimates of the widths of such barriers and the lengths of tunneling paths were available. Herein, such a measure is provided by calculating the length of the tunneling paths by using instanton theory. Potential energies are provided by density functional theory verified by explicitly correlated coupled cluster CCSD(T) energies. Our results explain the decay efficiency in the known cases and suggest new substitutions to tune the effects of barrier widths and heights. Fluorination and replacement of the hydroxyl group by a thiol group change the qualitative character of the decay. Methylaminocarbene is predicted to be stable for thousands of years. PMID:23609956

Kästner, Johannes

2013-04-22

20

Path-length-resolved measurements of multiple scattered photons in static and dynamic turbid media using phase-modulated low-coherence interferometry.  

PubMed

In optical Doppler measurements, the path length of the light is unknown. To facilitate quantitative measurements, we develop a phase-modulated Mach-Zehnder interferometer with separate fibers for illumination and detection. With this setup, path-length-resolved dynamic light scattering measurements of multiple scattered light in static and dynamic turbid media are performed. Optical path length distributions spanning a range from 0 to 11 mm are measured from the area under the phase modulation peak around the modulation frequency in the power spectrum. A Doppler-broadened phase modulation interference peak is observed that shows an increase in the average Doppler shift with optical path length, independent of absorption. Validation of the estimated path length distributions is done by measuring their deformation for increasing absorption and comparing these observations with predictions based on Lambert-Beer's law. PMID:17477735

Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G; Steenbergen, Wiendelt

21

Long-length contaminated equipment disposal process path document  

SciTech Connect

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

McCormick, W.A.

1998-09-30

22

Effect of discrete scatterers in CSF layer on optical path length in the brain  

NASA Astrophysics Data System (ADS)

Adequate modeling of light propagation in the complex and heterogeneous tissue of the human head is very important for quantitative near infrared spectroscopy and optical imaging. The presence of a clear and non-scattering CSF layer around the brain has been previously shown to strongly affect light propagation in the head. However the CSF layer is not totally filled with a non-scattering fluid and quite a few fine arachnoid trabeculae are actually present in the layer. In this study light propagation in an adult head model with discrete scatterers distributed within the CSF layer has been predicted by Monte Carlo simulation in order to investigate the effect of scattering caused by the arachnoid trabecula in the CSF layer. Results show that the presence of the arachnoid trabeculae affect the total optical path length, a parameter which can be directly measured by time-resolved measurement. However, the partial optical path length in the brain tissue, which relates the sensitivity of the near infrared spectroscopy signal to absorption changes in the brain is strongly affected by the CSF layer even in the presence of the arachnoid trabeculae. The increased partial optical path length results from an increased lateral spreading of the NIR light within the gray matter of the cortex.

Okada, Eiji; Delpy, David T.

2000-11-01

23

Long path atomic/ionic absorption spectrometry in an inductively coupled plasma.  

PubMed

A novel approach was taken to increase the atomic/ionic absorption path length in an inductively coupled plasma (ICP) by using a water-cooled quartz "T-shaped" bonnet. Atomic and ionic absorption spectrometry was performed utilizing a continuum source and line sources. Absorption spectra of synthetic multielement solutions were collected with a photodiode array. Sample introduction into the ICP was accomplished with an ultrasonic nebulizer. To prevent the bonnet from cracking, low radio frequency powers were utilized (i.e., 400-600 W). Plasma diagnostics were performed to study the plasma temperature and electron number density within the "T-shaped" bonnet. Analytical figures of merit were found to be better than those obtained from previous work attempted with inductively coupled plasma atomic absorption spectroscopy and approaching that of flame atomic absorption spectroscopy. PMID:2316872

Mignardi, M A; Smith, B W; Winefordner, J D

1990-03-15

24

Simulation of experimental investigations of X-ray spectral path lengths on Iskra-5 laser facility  

SciTech Connect

We describe an improved Slater average-ion model employed in the numerical-theoretical analysis of experimental data, which were obtained in the investigation of X-ray spectral path lengths performed on the Iskra-5 laser facility at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). The proposed model permits determining the spectral characteristics of the X-ray radiation with an accuracy of a few electronvolts. We outline the results of simulations of experiments with X-ray radiation-heated aluminium and germanium specimens of initial thickness of {approx}0.1 mm, in which absorption lines arising from 1s-2p transitions in Al and the absorption band arising from 2p-3d transitions in Ge were recorded.

Bel'kov, S A; Sharov, O O [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-10-31

25

Long path differential absorption measurements of tropospheric molecules  

NASA Astrophysics Data System (ADS)

The measurement of the important atmospheric molecules O3, NO2, CH2O, H2O, NO3, and HONO can be measured using long path differential absorption spectroscopy. The experiment is located at the Fritz Peak Observatory, 17 km west of Boulder, Colorado. This site permits both the measurement of clean continental air during times of westerly air flow, as well as polluted urban air during easterly up-slope episodes. The spectrograph used in this study is a low resolution double crossed Czerny-Turner, with a well matched receiving telescope. This spectrograph uses a 1 x 1024 element Reticon diode array detector to measure the molecular absorption spectra of these molecules in 40 nm bands in the near ultraviolet-visible region. The total optical path for this experiment is 20.6 km, and the path is folded by a 121 element retroreflector array thereby allowing the light source and spectrograph to be in the same location. Deduction of atmospheric concentrations these molecules over this path is accomplished by using a least squares procedure that employs the method of singular-value decomposition.

Harder, Jerald; Mount, George

1991-09-01

26

Computing Minimum Length Paths of a Given Homotopy Class.  

National Technical Information Service (NTIS)

The universal covering space of a surface is used to generalize previous results on computing paths in a simple polygon. Optimizing paths among obstacles in the plane are looked at under the Euclidean and link metrics and polygonal convex distance functio...

J. Hershberger J. Snoeyink

1990-01-01

27

Frequency path-length scaling of severe tornadoes during individual tornado outbreaks  

NASA Astrophysics Data System (ADS)

In this study we consider severe tornadoes, which we define as tornadoes with path lengths L > 10 km, in the continental USA (USA Storm Prediction Center Severe Weather Database). We find that for the period 1982-2011, for individual severe tornadoes (L > 10 km): (i) There is a strong linear scaling between the number of severe tornadoes in a year and their total path length in that year. (ii) The cumulative frequency path length data suggests that, not taking into account any changing trends over time, we would expect in a given year (on average) one severe tornado with a path length L > 115 km and in a decade (on average) one severe tornado with a path length L > 215 km. (iii) The noncumulative frequency-length statistics of severe tornado touchdown path lengths, 20 < L <200 km, is well approximated by an inverse power-law relationship with exponent near 3. We then consider the frequency path-length scaling of severe tornadoes (L > 10 km) during two tornado outbreaks, 27 April 2011 (67 severe tornadoes) and 25 May 2011 (16 severe tornadoes), and find similar statistical distributions with robust scaling. We believe that our robust scaling results provide evidence that touchdown path lengths can be used as quantitative measures of the systematic properties of severe tornadoes and severe tornado outbreaks.

Malamud, Bruce D.; Turcotte, Donald L.

2013-04-01

28

Probable X-Ray Mass Absorption Coefficients for Wave-Lengths Shorter Than the K Critical Absorption Wave-Length  

Microsoft Academic Search

Absorption coefficients of all elements may be calculated, from short wave-lengths up to the K critical absorption wave-length by the expression: ??&rgr;=??3Z2(2Z?A)???4Z5(2Z?A)+?eN0(Z?A). This formula holds for all elements when suitable values for ? and ? are chosen. Factors ? and ? are related to the atomic number, Z, by the expressions ?=(aZ2+bZ?c), and ?=(dZ2?eZ+f). Different values of the constants a,

John A. Victoreen

1943-01-01

29

Joint statistics of photon path length and cloud optical depth: Case studies  

NASA Astrophysics Data System (ADS)

We show the joint statistics of photon path length and cloud optical depth for cloudy sky cases observed at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site between September and December 1997. The photon path lengths are retrieved from moderate resolution oxygen A-band observations taken by a rotating shadow band spectroradiometer (RSS). For high optical depth cloud cases, two different populations in the scattergram of the path length versus cloud optical depth are apparent. One population is a result of single-layer cloud cases that exhibit a small variation of path length enhancement over a large optical depth range, together with a strong correlation between the radiation field and the cloud liquid water path, while the second population is attributed to multiple-layer cloud cases with large variability of enhanced photon path lengths. When the optical depth is less than 5, the population of cases appears to bifurcate as the solar air mass increases, with the lower branch exhibiting pressure-weighted path lengths shorter than the direct beam path lengths at these larger solar zenith angles. Using information from a millimeter-wave cloud radar, together with lidar and balloon-borne sonde data to further analyze these cases demonstrates that this bifurcation is caused by the altitude of the scattering; thin clouds aloft produce the lower branch and low-level aerosols produce the upper branch.

Min, Qilong; Harrison, Lee C.; Clothiaux, Eugene E.

2001-04-01

30

Measurements of attenuation and absorption lengths with the KASCADE experiment  

NASA Astrophysics Data System (ADS)

The attenuation of the electron shower size beyond the shower maximum is studied with the KASCADE extensive air shower (EAS) experiment in the primary energy range of about 1014-1016 eV. Attenuation and absorption lengths are determined by applying different approaches, including the method of constant intensity, the decrease of the flux of EASs with increasing zenith angle, and its variation with ground pressure. We observe a significant dependence of the results on the applied method. The determined values of the attenuation length ranges from 175 to 196 g/cm2 and of the absorption length from 100 to 120 g/cm2. The origin of these differences is discussed emphasizing the influence of intrinsic shower fluctuations.

KASCADE Collaboration; Antoni, T.; Apel, W. D.; Badea, A. F.; Bekk, K.; Bercuci, A.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Büttner, C.; Chilingarian, A.; Daumiller, K.; Doll, P.; Engel, R.; Engler, J.; Feßler, F.; Gils, H. J.; Glasstetter, R.; Haeusler, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Iwan, A.; Kampert, K.-H.; Klages, H. O.; Maier, G.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Müller, M.; Obenland, R.; Oehlschläger, J.; Ostapchenko, S.; Petcu, M.; Rebel, H.; Risse, M.; Roth, M.; Schatz, G.; Schieler, H.; Scholz, J.; Thouw, T.; Ulrich, H.; Vardanyan, A.; Weber, J. H.; Weindl, A.; Wentz, J.; Wochele, J.; Zabierowski, J.

2003-09-01

31

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2012 CFR

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path...point-to-point and the common carrier fixed point-to-point microwave services must equal or exceed the value set forth in...

2012-10-01

32

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2011 CFR

...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path...point-to-point and the common carrier fixed point-to-point microwave services must equal or exceed the value set forth in...

2011-10-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

34

Two Upper Bounds for the Weighted Path Length of Binary Trees.  

National Technical Information Service (NTIS)

Rooted binary trees with weighted nodes are structures encountered in many areas, such as coding theory, searching and sorting, information storage and retrieval. The path length is a meaningful quantity which gives indication about the expected time of a...

J. L. Pradels

1973-01-01

35

A model for the tropospheric excess path length of radio waves from surface meteorological measurements  

Microsoft Academic Search

Two models are given for predicting of the excess path length of radio waves from ground-based measurements of pressure, temperature, and humidity, at zenith and at a given apparent elevation angle. The models use the same formulation for the hydrostatic component of the excess path, but use different methods for the wet component. For the hydrostatic component, the models provide

H. Berrada Baby; P. Gole; J. Lavergnat

1988-01-01

36

Fiber optic acoustic hydrophone with double Mach–Zehnder interferometers for optical path length compensation  

Microsoft Academic Search

We report on the development of a fiber optic acoustic hydrophone which consists of a sensing Mach–Zehnder (MZ) interferometer and a compensating MZ interferometer for optical path length compensation. This double-interferometer configuration has the following advantages: the hydrophone is a true heterodyne device; a laser source with a short coherence length can be used; the sensing interferometer is completely passive;

T. K Lim; Y Zhou; Y Lin; Y. M Yip; Y. L Lam

1999-01-01

37

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

Microsoft Academic Search

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

William N. Plick; Christoph F. Wildfeuer; Petr M. Anisimov; Jonathan P. Dowling

2009-01-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

39

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2011 CFR

...than those specified in the Table, the EIRP shall not exceed...Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table above for the frequency band...authorizations, subject to periodic renewal. (c) Upon...

2011-10-01

40

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2012 CFR

...than those specified in the Table, the EIRP shall not exceed...Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table above for the frequency band...authorizations, subject to periodic renewal. (c) Upon...

2012-10-01

41

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

Microsoft Academic Search

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

Hans-georg Beyer; Dirk V. Arnold

2003-01-01

42

Study of temperature dependence of the optical path length in ion doped solids  

NASA Astrophysics Data System (ADS)

The aim of this work is to use Thermal Lens (TL) technique to measure the absolute value of the temperature coefficient of optical path length (ds/dT) in several optical materials. We studied fluoride, calcium aluminate glasses and YAG, YVO4, YLF, LiSAF, LiSGaF laser crystals.

Andrade, A. A.; Catunda, Tomaz; Mura, J.; Baesso, Mauro L.

2003-11-01

43

Study of temperature dependence of the optical path length in ion doped solids  

Microsoft Academic Search

The aim of this work is to use Thermal Lens (TL) technique to measure the absolute value of the temperature coefficient of optical path length (ds\\/dT) in several optical materials. We studied fluoride, calcium aluminate glasses and YAG, YVO4, YLF, LiSAF, LiSGaF laser crystals.

A. A. Andrade; Tomaz Catunda; J. Mura; Mauro L. Baesso

2003-01-01

44

Water absorption length measurement with the ANTARES optical beacon system  

NASA Astrophysics Data System (ADS)

ANTARES is a neutrino telescope located in the Mediterranean Sea with the aim of detecting high energy neutrinos of extra-terrestrial origin. It consists of a three dimensional array on 12 detection lines of photomultiplier tubes (PMTs) able to detect the Cherenkov light induced by muons produced in the interaction of neutrinos with the surrounding water and seabed. To reach the best angular resolution, good time and positioning calibrations are required. The propagation of Cherenkov photons strongly depends on the optical properties of the sea water, which has an impact on the reconstruction efficiency. The determination of the optical parameters, as the absorption and scattering lengths, is crucial to calculate properly the effective area and the angular resolution of the detector. The ANTARES optical beacon system consists of pulsed and fast, well controlled light sources distributed throughout the detector to carry out in situ the relative time calibration of the detector components. In this contribution we show some results on the sea water optical properties and their stability measured with the optical beacon system.

Yepes-Ramirez, Harold; ANTARES Collaboration

2011-01-01

45

Genetic Algorithm for Solving Fuzzy Shortest Path Problem in a Network with mixed fuzzy arc lengths  

NASA Astrophysics Data System (ADS)

We are concerned with the design of a model and an algorithm for computing a shortest path in a network having various types of fuzzy arc lengths. First, we develop a new technique for the addition of various fuzzy numbers in a path using ? -cuts by proposing a linear least squares model to obtain membership functions for the considered additions. Then, using a recently proposed distance function for comparison of fuzzy numbers. we propose a new approach to solve the fuzzy APSPP using of genetic algorithm. Examples are worked out to illustrate the applicability of the proposed model.

Mahdavi, Iraj; Tajdin, Ali; Hassanzadeh, Reza; Mahdavi-Amiri, Nezam; Shafieian, Hosna

2011-06-01

46

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

Microsoft Academic Search

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

William N. Plick; Christoph F. Wildfeuer; Petr M. Anisimov; Jonathan P. Dowling

2009-01-01

47

Transcranial optical path length in infants by near-infrared phase-shift spectroscopy  

Microsoft Academic Search

Background. Near-infrared spectroscopy (NIRS) is an emerging technique for noninvasive, bedside monitoring of cerebral oxygenation and\\u000a blood flow. Traditionally, it has relied on the Beer's Law relationship in which the concentration of light-absorbing oxygen-carrying\\u000a pigments is proportional to their light absorbance, and inversely proportional to an optical path length (a measure of the\\u000a distance traveled by photons passing through the

David A. Benaron; C. Dean Kurth; James M. Steven; Maria Delivoria-Papadopoulos; Britton Chance

1995-01-01

48

Decreasing the optical path length in an optoelectronic module using silicon micromachining  

NASA Astrophysics Data System (ADS)

In order to decrease the optical path length of an optoelectronic module, two ways of achieving 0960-1317/9/2/006/img1 silicon mirrors with trenches defining the mirror size are presented: dicing, and dry etching. The dicing was performed with a Disco DAD 361 dicing machine. To define the dry etched trench UV-lithography on electrodeposited resist was used. The electrodeposition was performed using commercially available positive photoresist PEPR 2400 from Shipley Ltd.

Richard, Åse; Rangsten, Pelle; Strandman, Carola; Bäcklund, Ylva

1999-06-01

49

Thermal lens determination of the temperature coefficient of optical path length in optical materials  

NASA Astrophysics Data System (ADS)

In this work thermal lens spectrometry is applied to determine the temperature coefficient of optical path length in several optical materials. Polymer, fluoride and low silica calcium aluminosilicate glasses and YAG, YVO4, YLF, LiSAF, and LiSGaF crystals were analyzed. The results showed the ability of the thermal lens method to obtain the absolute values of this so important optical parameter, which is crucial for those who work in the designing of solid state laser cavity.

Andrade, A. A.; Catunda, T.; Bodnar, I.; Mura, J.; Baesso, M. L.

2003-01-01

50

Thermal lens determination of the temperature coefficient of optical path length in optical materials  

Microsoft Academic Search

In this work thermal lens spectrometry is applied to determine the temperature coefficient of optical path length in several optical materials. Polymer, fluoride and low silica calcium aluminosilicate glasses and YAG, YVO4, YLF, LiSAF, and LiSGaF crystals were analyzed. The results showed the ability of the thermal lens method to obtain the absolute values of this so important optical parameter,

A. A. Andrade; T. Catunda; I. Bodnar; J. Mura; M. L. Baesso

2003-01-01

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

Simultaneous Water Vapor and Dry Air Path Length Measurements with the Keck Interferometer Nuller  

NASA Astrophysics Data System (ADS)

K-band phase and group delay measurements of atmospheric turbulence are used as part of the Keck Interferometer nuller cophasing system to provide high-bandwidth path length compensation at N band. Because of atmospheric dispersion, the path length fluctuations from dry air and water vapor must be estimated separately, and the computation of the N-band feedforward quantities from the K-band measurements is described. Simultaneous K and N-band sky data are presented that show good correspondence with the underlying atmospheric models. Simultaneous power spectra of dry air and water vapor path length turbulence measured on an 85 m baseline with the Keck Interferometer over 44 nights between 2007 June and 2009 July are also presented. From the median power spectra, the rms path length fluctuations at band from water vapor are found to be 48 times smaller than those for dry air, and the absolute level of the water vapor path length fluctuations is found to be a factor of 2 smaller than predicted based on archival data from the CSO test radio interferometer. It is postulated that part of the difference is attributable to surface-layer water vapor turbulence, which would be smaller at the elevation of the Keck telescopes than for the test antennas, similar to surface-layer effects seen in dry air seeing at Mauna Kea. The midfrequency power spectral amplitude better characterizes the residuals for a feedforward compensation system, and this value is found to be a factor of 65 smaller at K band for water vapor than for dry air; the difference compared to the ratio of the rms values is attributable to the lower effective wind speed of the water vapor turbulence, and thus lower control bandwidths are required for compensation than a simple scaling based on rms fluctuations would indicate. The water vapor coherence time is also shown to have modest correlations with both precipitable water vapor and the dry air coherence time, although the variability of the water vapor turbulence strength is larger than that of the dry air turbulence.

Colavita, M. M.

2010-05-01

53

Length Determination of a Fixed-Path Cylindrical Resonator with the Dual Wavelength Laser Interference Method  

NASA Astrophysics Data System (ADS)

The length is one of the key parameters for a cylindrical acoustic resonator used for measurement of the Boltzmann constant. A research project has been conducted in the National Institute of Metrology (NIM), China, for the re-determination of the Boltzmann constant with a fixed-path cylindrical acoustic resonator. This paper describes the procedure for the length determination. The excess fraction method was applied to accurately obtain the length of the resonator. This method is performed in a two-step procedure. First, the length is coarsely determined as L 1 with an uncertainty of 1.5 ?m in the length division of NIM. Second, the result of the coarse measurement is further interpolated by the dual wavelength laser interferometer with a resolution of 1 nm, which is composed of a 633 nm He-Ne laser and a 657 nm semiconductor laser. A Michelson wavemeter has been constructed for calibration of the wavelength of the semiconductor laser. The length variation of the resonator has to be measured from room temperature to the triple point of water (TPW). As a result, the laser interferometer can be also used as a precise dilatometer. The result and the measurement uncertainty of the length measurement are given in this paper.

Sun, J. P.; Zhang, J. T.; Zhang, X. Y.; Lin, H.; Feng, X. J.

2011-08-01

54

Exact evaluation of the cutting path length in a percolation model on a hierarchical network  

NASA Astrophysics Data System (ADS)

This work presents an approach to evaluate the exact value of the fractal dimension of the cutting path dfCP on hierarchical structures with finite order of ramification. Our approach is based on a renormalization group treatment of the universality class of watersheds. By making use of the self-similar property, we show that dfCP depends only on the average cutting path (CP) of the first generation of the structure. For the simplest Wheastone hierarchical lattice (WHL), we present a mathematical proof. For a larger WHL structure, the exact value of dfCP is derived based on a computer algorithm that identifies the length of all possible CP's of the first generation.

Andrade, R. F. S.; Herrmann, H. J.

2013-04-01

55

Angstrom-Range Optical Path-Length Measurement with a High-Speed Scanning Heterodyne Optical Interferometer  

NASA Astrophysics Data System (ADS)

A highly accurate method of optical path-length measurement is introduced by use of a scanning heterodyne optical interferometer with no moving parts. The instrument has demonstrated the potential to measure optical path length at angstrom resolution over continuous thickness in the micrometer range. This optical path length can be used to calculate the thickness of any material if the refractive index is known or to measure the refractive index of the material if the thickness is known. The instrument uses a single acousto-optic device in an in-line ultra-stable reflective geometry to implement rapid scanning in the microsecond domain for thickness measurements of the test medium.

Riza, Nabeel A.; Arain, Muzammil A.

2003-05-01

56

On the path length of an excess electron interacted with optical phonons in a molecular chain  

NASA Astrophysics Data System (ADS)

We show that in a molecular chain with dispersionless phonons at zero temperature, a “quasistationary” moving soliton state of an excess electron is possible. As the soliton velocity vanishes, the path length of the excess electron exponentially tends to infinity. It is demonstrated that in the presence of dispersion, when the soliton initial velocity exceeds the maximum group velocity of the chain, the soliton slows down until it reaches the maximum group velocity and then moves stationarily at this maximum group velocity. A conclusion is made of the fallacy of some works were the existence of moving polarons in a dispersionless medium is considered infeasible.

Lakhno, V. D.

2008-08-01

57

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

NASA Astrophysics Data System (ADS)

Electron bunch lengthening due to space-charge forces in state-of-the-art rf photoinjectors limits the minimum bunch length attainable to several hundreds of femtoseconds. Although this can be alleviated by increasing the transverse dimension of the electron bunch, a larger initial radius causes path-length differences in both the rf cavity and in downstream focusing elements. In this paper we show that a curved cathode virtually eliminates these undesired effects. Detailed numerical simulations confirm that significantly shorter bunches are produced by an rf photogun with a curved cathode compared to a flat cathode device. The proposed novel method will be used to provide 100 fs duration electron bunches for injection into a laser-driven plasma wakefield accelerator.

de Loos, M. J.; van der Geer, S. B.; Saveliev, Y. M.; Pavlov, V. M.; Reitsma, A. J. W.; Wiggins, S. M.; Rodier, J.; Garvey, T.; Jaroszynski, D. A.

2006-08-01

58

Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurements of diffuse light.  

PubMed

The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a turbid suspension of particles undergoing Brownian and translational motion. The path length resolution of this instrument is compared with a system using single mode fibers for illumination and detection. The optical path lengths are determined from the zero order moment of the phase modulation peak in the power spectrum. The weighted first moment, which is equal to the average Doppler shift, shows a linear response for different mean flow velocities within the physiological range. PMID:18163752

Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G; Steenbergen, Wiendelt

2007-12-01

59

In-situ detection of tropospheric OH radicals by folded long-path laser absorption. Results from the POPCORN Field Campaign in August 1994  

NASA Astrophysics Data System (ADS)

Ground based in-situ measurements of tropospheric hydroxyl radicals were conducted by folded long-path laser absorption as part of the field campaign POPCORN in August 1994. The OH instrument used an open optical multiple-reflection cell of 38.5 m base length through which the laser beam was passed up to 80 times. The broadband emission of a short-pulse UV laser together with a multichannel detection system allowed the simultaneous observation of six OH absorption lines in a spectral interval of ???0.24 nm at 308.1nm (A²?+,?? = 0? X²?,?? = 0 transition). Along with the OH radicals, the trace gases SO2, HCHO, and naphthalene were measured by this technique. The large spectral detection range covered a multitude of rotational absorption lines of these trace gases which were all used for multicomponent analysis, thus allowing a specific and sensitive detection of tropospheric OH radicals. An average 2? detection limit of 1.5 × 106 OH/cm³ for an integration time of 200 seconds and an absorption light path length of 1848 m was determined from the field measurements. In total, 392 OH data were obtained by long-path absorption during 16 days of field measurements. The observed OH concentrations reached peak values of 13 × 106 cm-3 at noon.

Dorn, H.-P.; Brandenburger, U.; Brauers, T.; Hausmann, M.; Ehhalt, D. H.

60

Relationship between path length and attenuation of radio waves transmitted in a uniform rain-filled medium  

Microsoft Academic Search

It has been accepted that rain attenuation (in an environment in which the rainfall rate is assumed uniform along the whole length of the radio link) is linear with respect to path length. It is shown here that for nonspherical raindrops this is not generally the case. Results over the frequency band 3-30 GHz are presented. These demonstrate that, in

S. A. J. Upton; B. G. Evans; A. R. Holt

1982-01-01

61

The absorption of electromagnetic radiation by metal cylinders of finite length  

Microsoft Academic Search

For metallic cylinders with a conductivity s=1018 s-1 and length to radius ratios in the range 3×104 to 3×105 the Mie-type solution for the absorption coefficient merges smoothly, with a domain of overlap, into the Rayleigh solution. The absorption effects are then shown to be rigorously determined at all wavelengths. A cosmological application is briefly discussed.

N. C. Wickramasinghe; A. N. Wickramasinghe; F. Hoyle

1992-01-01

62

In situ detection of tropospheric OH radicals by folded long-path laser absorption. Results from the POPCORN field campaign in August 1994  

Microsoft Academic Search

Ground based in situ measurements of tropospheric hydroxyl radicals were conducted by folded long-path laser absorption as part of the field campaign POPCORN in August 1994. The OH instrument used an open optical multiple-reflection cell of 38.5 m base length through which the laser beam was passed up to 80 times. The broadband emission of a short-pulse UV laser together

H.-P. Dorn; U. Brandenburger; T. Brauers; M. Hausmann; D. H. Ehhalt

1996-01-01

63

On the effect of the path length of small-world networks on epidemic dynamics.  

PubMed

We show how one can trace in a systematic way the coarse-grained solutions of individual-based stochastic epidemic models evolving on heterogeneous complex networks with respect to their topological characteristics. In particular, we illustrate the "distinct" impact of the average path length (with respect to the degree and clustering distributions) on the emergent behavior of detailed epidemic models; to achieve this we have developed an algorithm that allows its tuning at will. The framework could be used to shed more light on the influence of weak social links on epidemic spread within small-world network structures, and ultimately to provide novel systematic computational modeling and exploration of better contagion control strategies. PMID:22460641

Reppas, Andreas I; Spiliotis, Konstantinos; Siettos, Constantinos I

2012-03-01

64

A long path length spectroelectrochemical behavior analysis of the coabsorption system.  

PubMed

The coabsorption system in which both species Red and Ox absorb at the same wavelength was investigated by the long path length spectroelectrochemical technique. The variation of the system absorbance at the isosbestic point with time, which is strongly dependent upon the diffusion coefficients and their difference, was calculated by employing the method of digital simulation under semi-infinite condition. Simulated results indicated that each A(t)-t curve corresponded to definite values of D(R) and D(O) on the condition that D(R) is not equal to D(O). The species diffusion coefficients were evaluated by comparing the spectroelectrochemical experimental result at the isosbestic point with the simulated result, and experimentally verified by the study of electrooxidation of hydroquinone. PMID:18968051

Zhang, J; Zhou, A; Xie, Q; Wei, W

2000-08-16

65

Experimental determination of the effect of temperature on refractive index and optical path length of glass.  

PubMed

With the Fizeau interferometer method, the change in optical path length with temperature is measured at six wavelengths for twenty new Corning optical glasses. The sample, a polished block with a few seconds of wedge, is held in a double-walled chamber with temperature control provided over the range -20 degrees C to +80 degrees C by a circulating water-glycol mixture. A Gaertner interferometer viewing apparatus is modified by addition of a monitor head that permits simultaneous photoelectric fringe detecting and viewing. Measurement of thermal expansion with the Plummer-Hagy high precision dilatometer permits the extraction of the temperature coefficient of absolute refractive index from the optical path measurement. The coefficient of refractive index relative to standard air at the temperature of the glass is found by further data reduction using Edlén's equations. The experimental values of the index change as a function of temperature are curve-fitted by a FORTRAN program, and the slopes are computed to give instantaneous values of the coefficients. The average residual for the fit is about 1.0 x 10(-6). The precision of the absolute coefficient values is estimated to be +/-0.05 x 10(-6). Representative data for one glass are presented to illustrate the results available from this work. PMID:20111284

Parker, C J; Popov, W A

1971-09-01

66

Measurement of tropospheric OH concentrations by laser long-path absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Broadband laser long-path absorption (LPA) spectroscopy was used to measure the tropospheric OH concentrations in summer 1987 at Juelich, West Germany. The OH absorption spectra were recorded by a multichannel spectrometric detector. A second LPA spectrometer measured the concentrations of NO2, HCHO, and SO2. Also, O3, aerosol concentrations, meteorological parameters, and calibrated photolysis frequencies of O3 and NO2 were recorded. CO, CH4, and light hydrocarbons concentrations were determined by gas chromatographic analysis. The results of the measurements are presented, showing OH concentrations up to 6,800,000 molecules/cu cm.

Dorn, H.-P.; Callies, J.; Platt, U.; Ehhalt, D. H.

1988-11-01

67

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

68

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.  

PubMed

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. PMID:22352662

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

2012-01-01

69

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

Microsoft Academic Search

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

David L. Auble; Tilden P. Meyers

1992-01-01

70

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

71

Electron inelastic mean free path, electron attenuation length, and low-energy electron-diffraction theory  

NASA Astrophysics Data System (ADS)

Low-energy electron diffraction (LEED) theory is used for describing the electron transport in crystalline solids with the purpose of determining the electron attenuation length. The inelastic scattering of the primary electron in the electron gas of the material is introduced into the LEED theory in terms of the electron inelastic mean free path derived by Tanuma, Powell, and Penn from the Lindhard dielectric function and optical data [Surf. Interface Anal. 17, 911 (1991)]. The theorem of flux reversal for electrons in situations of inward and outward propagation is deduced from local inversion symmetry and specific boundary conditions at the sources. The theory is applied to 50-400 eV electrons incident on the three low-index surfaces of copper, and a fair agreement is found with a previous Monte Carlo simulation of the electron transport in amorphous copper. In addition to the inelastic electron-electron gas scattering, the inelastic electron-phonon scattering has a significant effect on the attenuation length in a crystalline material. The temperature parameter, necessary in a LEED calculation, does not occur in current Monte Carlo simulations. Common scattering potential models, at low energy, for LEED and for Auger electron spectroscopy and x-ray photoemission spectroscopy are discussed.

Rundgren, J.

1999-02-01

72

Alleviating the effects of light scattering in multivariate calibration of near-infrared spectra by path length distribution correction.  

PubMed

Near-infrared (NIR) spectroscopy has been used for noninvasive measurements of solid and liquid samples, through highly scattering media such as colloids, food, and tissue. It has seen many applications in agriculture, medicine, and petroleum industries, mainly due to the minimal sample preparation that is required. This minimal sample preparation does come at a cost to the analyst, since the high signal-to-noise ratio of a typical NIR instrument can be riddled with effects stemming from heterogeneity and the scattering of light. This work proposes a novel preprocessing method, the path length distribution correction (PDC) method, to correct spectral nonlinearities in samples of highly scattering media. These nonlinearities stem from the distribution of path lengths of the incident light, which are a result of the scattering of light in the sample. Recent developments in time-of-flight (TOF) spectroscopy have allowed for the acquisition of the distribution of times that photons travel within a sample simultaneous with the collection of the NIR spectrum. The TOF distribution is used to estimate a path length distribution within a sample, which is then used to fix the measurement spectra, giving each spectrum an apparent path length of unity. The PDC-corrected spectra can then be used with traditional multivariate calibration methods such as principal component regression (PCR) and partial least squares (PLS). Another discussion looks at the viability of using a lognormal distribution as a simple approximation of the TOF distribution. This would be very useful in circumstances in which experimental TOF distributions are not collected. PDC is shown to significantly improve prediction errors in experimental data sets, while diagnostic plots indicate that the corrected spectra do appear to have a path length of unity, thus alleviating effects of the distribution of path lengths. PMID:20223057

Leger, Marc N

2010-03-01

73

Mean emission length approach to multidimensional radiative transfer including scattering and real gas absorption  

NASA Astrophysics Data System (ADS)

A computational approach to radiative emission analysis is presented for applications where multidimensional, absorbing, emitting, and scattering media are important and real gas contributions must be incorporated. The mean emission length method of solving for the energy transfer is developed as an approximate yet accurate approach to such problems. Although developed using the photon path length method, the resulting analysis does not require knowledge of the photon path length distribution functions. Examples of the application of this approach for emission are included with particular emphasis upon its utility in problems involving real gases and scattering particles. Numerical results for planar and cylindrical media for ranges of optical depth and scattering albedo are presented, and the superior accuracy and computational efficiency of this method as compared to other common approaches are demonstrated.

Walters, D. V.; Buckius, R. O.

1992-01-01

74

NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30-14:30 LT - local time).

Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

2012-05-01

75

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

PubMed

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

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

2013-05-01

76

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

77

Open-path trace gas detection of ammonia based on cavity-enhanced absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A compact open-path optical ammonia detector is developed. A tunable external-cavity diode laser operating at 1.5 ?m is used to probe absorptions of ammonia via the cavity-enhanced absorption (CEA) technique. The detector is tested in a climate chamber. The sensitivity and linearity of this system are studied for ammonia and water at atmospheric pressure. A cluster of closely spaced rovibrational overtone and combination band transitions, observed as one broad absorption feature, is used for the detection of ammonia. On these molecular transitions a detection limit of 100 ppb (1 s) is determined. The ammonia measurements are calibrated independently with a chemiluminescence monitor. Compared to other optical open-path detection methods in the 1-2 ?m region, the present result shows an improved sensitivity for contactless ammonia detection by over one order of magnitude. Using the same set-up, a detection limit of 100 ppm (1 s) is determined for the detection of water at atmospheric pressure.

Peeters, R.; Berden, G.; Apituley, A.; Meijer, G.

78

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

NASA Astrophysics Data System (ADS)

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

Auble, David L.; Meyers, Tilden P.

1992-05-01

79

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

80

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

NASA Astrophysics Data System (ADS)

We have constructed a five station 12 GHz atmospheric phase interferometer (API) for the Submillimeter Array (SMA) located near the summit of Mauna Kea, Hawaii. Operating at the base of unoccupied SMA antenna pads, each station employs a commercial low noise mixing block coupled to a 0.7 m off-axis satellite dish which receives a broadband, white noise-like signal from a geostationary satellite. The signals are processed by an analog correlator to produce the phase delays between all pairs of stations with projected baselines ranging from 33-261 m. Each baseline's amplitude and phase is measured continuously at a rate of 8 kHz, processed, averaged and output at 10 Hz. Further signal processing and data reduction is accomplished with a Linux computer, including the removal of the diurnal motion of the target satellite. The placement of the stations below ground level with an environmental shield combined with the use of low temperature coefficient, buried fiber optic cables provides excellent system stability. The sensitivity in terms of rms path length is 1.3 microns which corresponds to phase deviations of about 1° of phase at the highest operating frequency of the SMA. The two primary data products are: (1) standard deviations of observed phase over various time scales, and (2) phase structure functions. These real-time statistical data measured by the API in the direction of the satellite provide an estimate of the phase front distortion experienced by the concurrent SMA astronomical observations. The API data also play an important role, along with the local opacity measurements and weather predictions, in helping to plan the scheduling of science observations on the telescope.

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

2012-12-01

81

Anomalous results obtained for long-path measurements of both continuum absorption and level populations in a pure recombining hydrogen plasma  

NASA Astrophysics Data System (ADS)

The continuum absorption in a pure hydrogen plasma between 6400 and 6545 A has been measured using laser spectroscopy over a 400 m path length. Contributions to the opacity from a number of processes have been calculated, including the bound-free absorption from high-lying neutral hydrogen levels, estimated from a direct interferometric measurement of the n = 2 level population. Theoretical values for the n = 2 level population, calculated using a 20-level collisional-radiative code, disagree with the measured values by up to a factor of three, and calculations of the absorption fail to explain the measured results by approximately an order of magnitude. No explanation for these discrepancies is obvious.

Nightingale, M. P. S.; Burgess, D. D.

1983-11-01

82

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

NASA Astrophysics Data System (ADS)

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

Everaers, Ralf

2012-08-01

83

Tropospheric path-length correction using a dual-frequency transportable radiometer  

NASA Astrophysics Data System (ADS)

It is demonstrated that the electrical path delay of microwaves due to tropospheric water vapor and clouds can be measured and corrected by means of a dual-frequency water-vapor radiometer (WVR) working at 23.8 and 31.5 GHz. The path delay can be calculated by a linear combination of the brightness temperatures measured at these two frequencies. The required inversion coefficients were calculated using a set of one-year radiosonde data from Payerne, Switzerland. Comparing the path delay calculated from radiosonde data and from WVR, the latter yields higher accuracy and better temporal and spatial resolution. After the calibration, the rms accuracy of the path delays is less than 0.8 cm in zenith and less than 9 percent for elevation angles above 15 deg.

Puliafito, S. E.; Buerki, Beat

84

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

PubMed

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

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

2009-01-01

85

Strategies for Incorporating Knowledge Defects and Path Length in Trust Aggregation  

Microsoft Academic Search

\\u000a The ability for a user to accurately estimate the amount of trust to be placed in a peer user is gaining more and more attention\\u000a in social network applications. Trust aggregation provides this ability by identifying paths that connect users in the network,\\u000a and by merging trust opinions expressed by users along these paths. However, as individual trust opinions are

Nele Verbiest; Chris Cornelis; Patricia Victor; Enrique Herrera-Viedma

2010-01-01

86

Distinct Clusterings and Characteristic Path Lengths in Dynamic Small-World Networks with Identical Limit Degree Distribution  

NASA Astrophysics Data System (ADS)

Many real-world networks belong to a particular class of structures, known as small-world networks, that display short distance between pair of nodes. In this paper, we introduce a simple family of growing small-world networks where both addition and deletion of edges are possible. By tuning the deletion probability q t , the model undergoes a transition from large worlds to small worlds. By making use of analytical or numerical means we determine the degree distribution, clustering coefficient and average path length of our networks. Surprisingly, we find that two similar evolving mechanisms, which provide identical degree distribution under a reciprocal scaling as t goes to infinity, can lead to quite different clustering behaviors and characteristic path lengths. It is also worth noting that Farey graphs constitute the extreme case q t ?0 of our random construction.

Shang, Yilun

2012-11-01

87

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.

88

Testing single and double limb standing balance performance: comparison of COP path length evaluation between two devices.  

PubMed

Center of pressure (COP) path length evaluation was commonly applied to measure postural sway and usually obtained from gold standard force plates. Thus, we comparatively investigated the feasible and less-expensive GKS® balance system (GKS) with the Kistler® force platform (KIS). 34 non-specifically trained but active adults (14 males, 20 females, age: 25.4±4.8 years; weight: 69.3±12.3 kg; height: 1.75±0.09 m, sports activity: 5.8±3.6 hours per week) were randomly tested on both devices during double and single limb stance with opened and closed eyes. Irrespective of the analysed time frame, repeated measures analyses of variances revealed higher path length readings for GKS compared to KIS for 30 s (F=6.8, p=0.01) and 10 s (F=21.2, p=0.001). Large effect sizes of the COP path length differences between GKS and KIS decreased from easy tasks (double limb, eyes open; d(30-s)=2.55, d(10-s)=2.04) to the most severe task (single limb, eyes closed; d(30-s)=0.02, d(10-s)=0.23). According to Bland and Altman, the limits of agreements indicated a high random variability component (between 29%, double limb, eyes open and 67%, single limb, eyes closed). The overall intraclass correlation coefficients (ICC) across all four standing balance tasks were moderate for the 30 s- (0.57) as well as the 10 s-analysis (0.65). In conclusion, the COP path length displacements obtained from the GKS balance system seem to differ with a considerable random variability from Kistler force platform data. Thus, measurements of the evaluated devices should not be used interchangeably. Further methodological investigations regarding balance measures seem warranted. PMID:22565319

Donath, Lars; Roth, Ralf; Zahner, Lukas; Faude, Oliver

2012-05-06

89

The Absorption of X-Rays of Wave-Length down to.08A  

Microsoft Academic Search

Mass absorption coffiecients of C, paraffine, S and 16 metal elements from Al to U for wave-lengths.56 to.08A have been measured in continuation of previous work1 which covered most of these elements in the range.71 to.10A. The general radiation from a tungsten target (operated at voltages up to 200 kv) was dispersed by a crystal into an ionization chamber. By

S. J. Allen

1926-01-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

91

Open-path tunable diode laser absorption spectroscopy for acquisition of fugitive emission flux data.  

PubMed

Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. Environmental Protection Agency (EPA) has developed a ground-based optical remote-sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transform infrared spectroscopy (OP-FTIR) has been the primary technique for acquisition of pollutant concentration data used in this emission measurement method. For a number of environmentally important compounds, such as ammonia and methane, open-path tunable diode laser absorption spectroscopy (OP-TDLAS) is shown to be a viable alternative to Fourier transform spectroscopy for pollutant concentration measurements. Near-IR diode laser spectroscopy systems offer significant operational and cost advantages over Fourier transform instruments enabling more efficient implementation of the measurement strategy. This article reviews the EPA's fugitive emission measurement method and describes its multipath tunable diode laser instrument. Validation testing of the system is discussed. OP-TDLAS versus OP-FTIR correlation testing results for ammonia (R2 = 0.980) and methane (R2 = 0.991) are reported. Two example applications of tunable diode laser-based fugitive emission measurements are presented. PMID:15991674

Thoma, Eben D; Shores, Richard C; Thompson, Edgar L; Harris, D Bruce; Thorneloe, Susan A; Varma, Ravi M; Hashmonay, Ram A; Modrak, Mark T; Natschke, David F; Gamble, Heather A

2005-05-01

92

Measurement of the (?2+2?3) band of methane by photoacoustic and long path absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The optical absorption spectrum of the (?2+2?3) combination band of methane in the 1.33 ?m range was investigated by photoacoustic and FTIR long path spectroscopy. The photoacoustic measurements were performed with a commercial external cavity diode laser (ECDL) and a differential photoacoustic (PA) detector. The absorption spectrum was obtained by scanning the wavelength of the ECDL through the 1317-1343 nm range of the methane (?2+2?3) band. A certified mixture of 1000 ppmV methane in synthetic air was used in a continuous flow mode. A linear concentration dependence of the PA signal was observed in the region of 10-1000 ppmV CH4. The absorption coefficients calculated from the measured sound pressure are in good agreement with the values given in the literature for several R-branch lines. Optical absorption measurements were performed with a long path White cell in combination with a FTIR spectrometer.

Miklós, A.; Hess, P.; Romolini, A.; Spada, C.; Lancia, A.; Kamm, S.; Schäfer, S.

1999-03-01

93

Interferometric interrogation of in-fiber Bragg grating sensors without mechanical path length scanning  

Microsoft Academic Search

We report the interrogation of a fiber Bragg grating (FBG) using an interferometer with a tilted mirror such that the optical path difference is a function of position on an array detector. Absolute measurements of mean resonant wavelength from the phase of the analytic signal of the spatial interferogram are determined, and a technique based on using a reference laser

Dominic F. Murphy; Dónal A. Flavin; Roy McBride; Julian D. C. Jones

2001-01-01

94

Intrinsic shortest path length: a new, accurate a priori wirelength estimator  

Microsoft Academic Search

A priori wirelength estimation is concerned with predicting various wirelength characteristics before placement. In this work we propose a novel, accurate estimator of net lengths. We observe that in \\

Andrew B. Kahng; Sherief Reda

2005-01-01

95

Effect of Wave-Number Error on the Computation of Path-Length Delay in White-Light Interferometry  

NASA Astrophysics Data System (ADS)

We analyze the error in computed optical path-length delay when using a phase-shifting interferometry (PSI) algorithm with an error in the operating wavelength. The delay error decomposes into two terms. The first is the error in the conversion from a phase measurement to the delay because of the incorrect wavelength, and the second is the error made in the phase measurement itself that is due to the wavelength error. The most important aspect of this investigation is to ascertain this latter error. A general characterization is obtained, and a particularly simple formula is developed for the special case of least-squares estimation involving only the ratio of the wave-number error to the wave number and a multiplicative factor that is an a priori computable nonlinear function of the ratio of the modulator stroke length to the operating wavelength. Because the ultimate path-length error is a function of the two terms, a new set of PSI algorithms that compensate the computed phase error to cancel the conversion error is developed. Numerical simulations are presented to validate the analysis and establish the insensitivity of the new algorithms to wave-number error.

Milman, Mark H.; Catanzarite, Joe; Turyshev, Slava G.

2002-08-01

96

Measurement of Urban Air Quality by an Open-Path Quantum Cascade Laser Absorption Spectrometer in Beijing During Summer 2008  

NASA Astrophysics Data System (ADS)

The 2008 Olympic Games focused attention on the air quality of Beijing, China and served as an important test-bed for developing, deploying, and testing new technologies for analysis of air quality and regional climate in urban environments. Poor air quality in urban locations has a significant detrimental effect on the health of residents while also impacting both regional and global climate change. As a result, there exists a great need for highly sensitive trace gas sensors for studying the atmosphere of the urban environment. Open-path remote sensors are of particular interest as they can obtain data on spatial scales similar to those used in regional climate models. Quantum cascade lasers (QCLs) can be designed for operation in the mid-infrared (mid-IR) with a central wavelength anywhere between 3 to 24 ?m and made tunable over a wavelength interval of over 0.1 ?m. The Quantum Cascade Laser Open-Path System (QCLOPS) is a mid-infrared laser absorption spectrometer that uses a tunable, thermoelectrically cooled, pulsed Daylight Solutions Inc. QCL for measurement of trace gases. The system is aimed at applications with path lengths ranging from approximately 0.1 to 1.0 km. The system is designed to continuously monitor multiple trace gases [water vapor (H2O), ozone (O3), ammonia (NH3), and carbon dioxide (CO2)] in the lower atmosphere. A field campaign from July to September 2008 in Beijing used QCLOPS to study trace gas concentrations before, during, and after the Olympic Games in an effort to capture changes induced by emissions reduction methods. QCLOPS was deployed at the Institute of Atmospheric Physics - Chinese Academy of Sciences on the roof of a two-story building, at an approximate distance of 2 miles from the Olympic National Stadium ("The Bird's Nest.") QCLOPS operated with an open-path round trip distance of approximately 75 m. The system ran with minimal human interference, twenty-four hours per day for the full campaign period. In order to collect data over numerous absorption peaks belonging to the target gases of H2O, NH3, O3, and CO2, measurements were made at 317 different wavelengths within the full tuning range of the laser (1020 - 1070 cm-1). We present the design of this novel sensor which was successfully built, deployed, and operated with minimal operator intervention for the three month field campaign period. Furthermore, we present the results of the field campaign and the capabilities of the QCLOPS system to measure fluctuations of the trace gases at parts-per-billion levels. The time series data illustrate the changing levels of the trace gases over the campaign period. In addition, data from commercial sensors simultaneously deployed at the field site are presented as a validation of the capabilities of the QCLOPS system. This work was supported by MIRTHE (NSF-ERC #EEC-0540832).

Michel, A. P.; Liu, P. Q.; Yeung, J. K.; Zhang, Y.; Baeck, M. L.; Pan, X.; Dong, H.; Wang, Z.; Smith, J. A.; Gmachl, C. F.

2009-05-01

97

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.

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

2010-01-01

98

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

99

Phrase Length Matters: The Interplay between Implicit Prosody and Syntax in Korean "Garden Path" Sentences  

ERIC Educational Resources Information Center

|In spoken language comprehension, syntactic parsing decisions interact with prosodic phrasing, which is directly affected by phrase length. Here we used ERPs to examine whether a similar effect holds for the on-line processing of written sentences during silent reading, as suggested by theories of "implicit prosody." Ambiguous Korean sentence…

Hwang, Hyekyung; Steinhauer, Karsten

2011-01-01

100

Long Path Atmospheric Ozone Absorption in the 9-10-micro Region Observed from a Balloon-Borne Spectrometer.  

PubMed

A balloon-borne spectrometer was used to measure the atmospheric absorption of solar radiation in the 9-10-micro region as a function of altitude. Among the numerous spectra recorded, several were made with very long optical paths above the troposphere obtained from floating altitude (~30 km) while the sun set. When the experimental results are compared with calculated spectra, based on line by line parameters of the nu(3) and nu(1) fundamentals of ordinary ozone, (16)O(3), combined with the Curtis-Godson approximation, large discrepancies are found for the long path spectra. It is shown that the hot bands nu(3), + nu(2), - nu(2), and nu(3), + nu(3), - nu(3), of the (16)O(3), and the nu(3) fundamentals of the isotopic species (16)O(18)O(16)O and (16)O(16)O(18)O, can contribute significant absorption for long paths such as obtained in this experiment. Such long paths also give rise to significant absorptions by the nu(3) - nu(1) and the nu(3) - 2nu(2) degrees bands of CO(2). Including these weak bands in the calculated spectra leads to good agreement with the observed data. PMID:20076244

Goldman, A; Kyle, T G; Murcray, D G; Murcray, F H; Williams, W J

1970-03-01

101

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

102

Chord-length and free-path distribution functions for many-body systems  

Microsoft Academic Search

We study fundamental morphological descriptors of disordered media (e.g., heterogeneous materials, liquids, and amorphous solids): thechord-lengthdistributionfunctionp(z) and the free-pathdistributionfunctionp(z,a). For concreteness, we will speak in the language of heterogeneous materials composed of two different materials or ‘‘phases.’’ The probability density function p(z) describes the distribution of chord lengths in the sample and is of great interest in stereology. For example,

Binglin Lu; S. Torquato

1993-01-01

103

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. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1745-1756, 2013. PMID:23832294

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

2013-07-06

104

Probing nanoscopic droplet interfaces in aqueous solution with vibrational sum-frequency scattering: A study of the effects of path length, droplet density and pulse energy  

NASA Astrophysics Data System (ADS)

We present a description of sum frequency scattering experiments to probe the interfacial vibrational spectrum of nanoscopic oil droplets dispersed in water. SF scattering measurements as a function of optical path length, infrared (IR) pulse energy and particle density show that for different IR excitation wavelengths a different optimum experimental geometry exists. The optimum optical path length matches roughly the 1/e absorbance length in D2O of the used IR frequency. The intensity depends linearly on the particle density. The SF intensity also scales linearly with the IR pulse energy, whereas no changes are observed in the spectral shape.

de Aguiar, Hilton B.; Samson, Jean-Sebastien; Roke, Sylvie

2011-08-01

105

Temperature-dependent ballistic transport in a channel with length below the scattering-limited mean free path  

NASA Astrophysics Data System (ADS)

The temperature-dependent ballistic transport, using nonequilibrium Arora distribution function (NEADF), is shown to result in mobility degradation with reduction in channel length, in direct contrast to expectation of a collision-free transport. The ballistic mean free path (mfp) is much higher than the scattering-limited long-channel mfp, yet the mobility is amazingly lower. High-field effects, converting stochastic velocity vectors to streamlined ones, are found to be negligible when the applied voltage is less than the critical voltage appropriate for a ballistic mfp, especially at cryogenic temperatures. Excellent agreement with the experimental data on a metal-oxide-semiconductor field-effect transistor is obtained. The applications of NEADF are shown to cover a wide spectrum, covering regimes from the scattering-limited to ballistic, from nondegenerate to degenerate, from nanowire to bulk, from low- to high-temperature, and from a low electric field to an extremely high electric field.

Arora, Vijay K.; Zainal Abidin, Mastura Shafinaz; Tan, Michael L. P.; Riyadi, Munawar A.

2012-03-01

106

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

107

Path length distributions for solar photons under cloudy skies: Comparison of measured first and second moments with predictions from classical and anomalous diffusion theories  

NASA Astrophysics Data System (ADS)

Using high-resolution oxygen A band spectrometry (?/?? = 60000) in the 767.7-770.7 nm wavelength range, we investigate the first and second moments of the distributions of path lengths of photons in transmitted skylight for different cloud conditions. Our observations are supported by measurements of column liquid water path by multichannel microwave radiometry, cloud structure by millimeter cloud radar observations, and cloud base by a laser ceilometer. For the investigated multilayer cloud covers (decks of stratus, cumulus, altostratus, and cirrus), our measurements indicate that the photon path statistics are mostly governed by anomalous diffusion, whereby classical diffusion occurs in the limiting case of a single compact (plane parallel) cloud layer. The ratio for the inferred second and first moments of the path lengths confirms the relation recently derived by Davis and Marshak (2002) for photon diffusion in single optically thick cloud layers and extends it to more complex cloud geometry.

Scholl, T.; Pfeilsticker, K.; Davis, A. B.; Klein Baltink, H.; Crewell, S.; LöHnert, U.; Simmer, C.; Meywerk, J.; Quante, M.

2006-06-01

108

Long term NO2 measurements in Hong Kong using LED based Long Path Differential Optical Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 concentrations in the Kowloon Tong and Mong Kok district of Hong Kong and we compare the measurement results to concentrations reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time.

Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

2011-11-01

109

Measurement of tropospheric trace gases by long-path differential absorption spectroscopy during the 1993 OH Photochemistry Experiment  

NASA Astrophysics Data System (ADS)

In August and September 1993 a comparative study of tropospheric long-path absorption techniques with in situ methods was performed for both the hydroxyl radical and the other important trace species. Long-path measurements were made over the 10.3 km path between Fritz Peak Observatory and Caribou Mine in the mountains 17 km west of Boulder, Colorado. At Caribou Mine, a 121 element, 1 m2 retroreflector array folds the optical path to give a total path of 20.6 km. The in situ instruments were located at Idaho Hill 0.5 km northwest of Caribou Mine. The optical design and analysis techniques used to obtain the path-integrated concentrations of O3, CH2O, SO2, and NO2 will be presented. The spectrograph used in this study is a 1/4 m double, crossed Czerny-Turner that employs a diode array detector allowing the acquisition of 40 nm spectral bands in the near UV and visible spectral regions. This system also utilizes automatic alignment and self-adjusting time integration so the system will acquire data in an unattended mode. The spectral bands selected for this study permit the simultaneous measurement of O3, NO2, CH2O, and SO2; NO2 and H2O; and NO3 and H2O. The data analysis uses a nonlinear least squares regression procedure to deduce the concentration of each of the species present in the atmosphere and also provides an effective method for removing the influence of scattered solar light for daytime measurements. An estimate of the measurement precision can be found by comparing atmospheric spectra analyzed with two different IO spectra; one measured through the atmosphere and the other a direct arc lamp spectrum.

Harder, J. W.; Jakoubek, R. O.; Mount, G. H.

1997-03-01

110

Review and analysis of VHF/UHF field strength measurements: Measurements at VHF over path lengths greater than 100 km  

NASA Astrophysics Data System (ADS)

In 1983 CCIRIWP 5/5 put forward a number of proposals for improvements to the field strength prediction methods of CCIR Recommendation 370 and associated Report 239, as used for international planning negotiations in the VHF and UHF Broadcast Bands. Described are the results of studies carried out by the BBC, in conjunction with other propagation investigations, to assess the validity of those proposals of IWP 5/5 which relate to propagation over path lengths in excess of about 100 km in the VHF Bands. It is concluded that these proposals can be supported with only one exception, relating to an addition of 7 dB to beyond-horizon oversea curves. Subsequently, the VHF proposals (excepting the one relating to the 7 dB correction) have been endorsed by CCIR Study Group 5 and adopted by the Plenar Meeting in 1986 for inclusion as modifications to Recommendation 370. Even so, limitations in the exsiting methods are identified and further work is proposed.

Sandell, R. S.; Bell, C. P.; Taplin, D. W.

1986-12-01

111

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

EPA Science Inventory

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

112

Preliminary simulation of hyporheic hydrology suggests systematic changes in hyporheic flow path length and residence time in response to reach-scale channel restoration in Meacham Creek, OR  

NASA Astrophysics Data System (ADS)

Hyporheic hydrologic response to stream restoration has typically focused on hydrodynamics associated with individual features or habitat units rather than whole reaches. Here we present preliminary results from MODFLOW simulations that compare modeled hyporheic hydrology prior to and after major channel reconfiguration associated with a recently completed reach-scale channel restoration on Meacham Creek in northeastern Oregon. Our model was parameterized using LiDAR floodplain surface elevation data and empirically-derived estimates of aquifer properties. Results show that groundwater flow path length and cumulative residence time distributions are apt to be altered by channel reconfiguration. For example, our model shows that the relatively high-gradient and straight baseline channel is dominated by either short or long flow path lengths, with relatively few medium length flow paths. In contrast, the proposed restoration channel is more sinuous and has a lower gradient. Our modeling suggests that the restoration channel will have a broader distribution of flow path lengths and residence times. We used model results to select well locations for intensive monitoring of groundwater surface elevation and temperature. Monitoring will continue through 2012 and is designed to evaluate model predictions as well as to document the effects of the channel restoration on surface water-groundwater interactions and concomitant effects on water temperature.

Amerson, B. E.; Poole, G.

2011-12-01

113

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

114

Open-Path Tunable Diode Laser Absorption Spectroscopy for Acquisition of Fugitive Emission Flux Data  

Microsoft Academic Search

Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. Environmental Protection Agency (EPA) has developed a ground-based optical remote-sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transform infrared spectroscopy (OP–FTIR) has been the primary technique for acquisition of pollutant concentration data used in this emission measurement method.

Eben D. Thoma; Richard C. Shores; Edgar L. Thompson; D. Bruce Harris; Susan A. Thorneloe; Ravi M. Varma; Ram A. Hashmonay; Mark T. Modrak; David F. Natschke; Heather A. Gamble

2005-01-01

115

Delivery Path Length and Holding Tree Minimization Method of Securities Delivery among the Registration Agencies Connected as Non-Tree  

NASA Astrophysics Data System (ADS)

To dematerialize the securities such as stocks or cooporate bonds, the securities were registered to account in the registration agencies which were connected as tree. This tree structure had the advantage in the management of the securities those were issued large amount and number of brands of securities were limited. But when the securities such as account receivables or advance notes are dematerialized, number of brands of the securities increases extremely. In this case, the management of securities with tree structure becomes very difficult because of the concentration of information to root of the tree. To resolve this problem, using the graph structure is assumed instead of the tree structure. When the securities are kept with tree structure, the delivery path of securities is unique, but when securities are kept with graph structure, path of delivery is not unique. In this report, we describe the requirement of the delivery path of securities, and we describe selecting method of the path.

Shimamura, Atsushi; Moritsu, Toshiyuki; Someya, Harushi

116

Development of a sensitive long path absorption photometer to quantify peroxides in aerosol particles (Peroxide-LOPAP)  

NASA Astrophysics Data System (ADS)

A new off-line instrument to quantify peroxides in aerosol particles using iodometry in long path absorption spectroscopy has been developed and is called peroxide long path absorption photometer (Peroxide-LOPAP). The new analytical setup features important technical innovations compared to hitherto published iodometric peroxide measurements. Firstly, the extraction, chemical conversion and measurement of the aerosol samples are performed in a closed oxygen-free (~ 1 ppb) environment. Secondly, a 50-cm optical detection cell is used for an increased photometric sensitivity. The limit of detection was 0.1 ?M peroxide in solution or 0.25 nmol m-3 with respect to an aerosol sample volume of 1 m3. The test reaction was done at a constant elevated temperature of 40 °C and the reaction time was 60 min. Calibration experiments showed that the test reaction with all reactive peroxides, i.e. hydrogen peroxide (H2O2), peracids and peroxides with vicinal carbonyl groups (e.g. lauroyl peroxide) goes to completion and their sensitivity (slope of calibration curve) varies by only ±5%. However, very inert peroxides have a lower sensitivity. For example, tert-butyl hydroperoxide shows only 37% sensitivity compared to H2O2 after 1 h. A kinetic study revealed that even after 5 h only 85% of this inert compound had reacted. The time trends of the peroxide content in secondary organic aerosol (SOA) from the ozonolysis and photo-oxidation of ?-pinene in smog chamber experiments were measured. The highest mass fraction of peroxides with 34% (assuming a molecular weight of 300 g mol-1) was found in freshly generated SOA from ?-pinene ozonolysis. Mass fractions decreased with increasing NO levels in the photo-oxidation experiments. A decrease of the peroxide content was also observed with aging of the aerosol, indicating a decomposition of peroxides in the particles.

Mertes, P.; Pfaffenberger, L.; Dommen, J.; Kalberer, M.; Baltensperger, U.

2012-10-01

117

Reliability of liquid core optical waveguides for sensitive optical absorption measurements of trace species in water  

Microsoft Academic Search

Long path optical waveguides can be used in optical absorption measurements to increase the optical path length and, thus, the overall absorption of a sample. Recently, 1m long coiled Liquid Waveguide Capillary Cells (LWCC) have been used by analytical spectroscopists to measure the absorption strength of weakly absorbing liquids. However, most of these measurements have used conventional light sources such

Avishekh Pal

2005-01-01

118

Performance Simulations of Spaceborne Methane Observations by Integrated-Path Differential Absorption Lidar  

NASA Astrophysics Data System (ADS)

A lidar-based satellite instrument for global observations of atmospheric methane is foreseen whose expected performance and technical feasibility are currently investigated in planning phase 0/A. Methane is, after carbon dioxide, the second most important greenhouse gas, whereby its anthropogenic emissions are much more uncertain. In addition, climate change may cause an important positive feedback of yet unknown intensity by release of methane from melting permafrost soils and ocean sediments. The current observational network is not able to monitor these sources with sufficient density and accuracy: While the ground-based in-situ network is too sparse, existing passive remote sensors on spacecraft are not accurate enough. Preliminary studies show that lidar with a realistic instrument design on a LEO platform has the potential to overcome these shortcomings and to measure methane with an accuracy and spatial resolution that satisfies the requirements of the user community. The presentation will include basic issues such as the selection of suitable methane absorption wavelengths, key per-formance parameters of instrument and spacecraft, and an assessment of the residual bias. It will highlight critical performance parameters such as instrument noise and surface reflectivity, and list the instrument and platform characteristics needed to fulfil the user requirements.

Kiemle, Christoph; Quatrevalet, Mathieu; Ehret, Gerhard; Amediek, Axel

119

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.

120

CHARM-F: An airborne integral path differential absorption lidar for simultaneous measurements of carbon dioxide and methane columns  

NASA Astrophysics Data System (ADS)

CHARM-F (CO2 and CH4 Atmospheric Remote Monitoring - Flugzeug) is DLR's airborne Integral Path Differential Absorption (IPDA) lidar for simultaneous measurements of the column-weighted average dry-air mixing ratios of atmospheric carbon dioxide and methane, designed to be flown on DLR's new High-Altitude, LOng-range research aircraft, HALO. It is meant to serve as a demonstrator of the use of spaceborne active optical instruments in inferring atmospheric CO2 and CH4 surface fluxes from total column measurements by inverse modeling. As it will be shown, this is enabled by HALO's high flight altitude and its range of 8000 km, which will make it possible to produce real-world data at truly regional scales with a viewing geometry and vertical weighting function similar to those enabled by a space platform. In addition, CHARM-F has the potential to be used as a validation tool not only for active but also passive spaceborne instruments utilizing scattered solar radiation for remote sensing of greenhouse gases. Building on the expertise from CHARM, a helicopter-borne methane IPDA lidar for pipeline monitoring developed in collaboration with E.ON, and WALES, DLR's water vapour differential absorption lidar, CHARM-F relies on a double-pulse transmitter architecture producing nanosecond pulses which allows for a precise ranging and a clean separation of atmospheric influences from the ground returns leading to an unambiguously defined column. One pulse is tuned to an absorption line of the trace gas under consideration, the other to a nearby wavelength with much less absorption. The close temporal separation of 250 ?s within each pulse pair ensures that nearly the same spot on ground is illuminated. The ratio of both return signals is then a direct function of the column-weighted average dry-air mixing ratio. The two laser systems, one for each trace gas, use highly efficient and robust Nd:YAG lasers to pump an optical parametric oscillator (OPO) level which converts the pump radiation to the desired wavelengths. Because typical surface CO2 and CH4 sources and sinks alter the total column only by a few percent, the required precision and accuracy are very stringent. This puts particularly challenging requirements on the spectral properties of the emitted pulses. To achieve single mode operation with very high spectral purity, both pumps and OPOs are injection seeded. Absolute stability of the emitted wavelengths is achieved by locking the seed lasers to the same absorption lines as those used in the atmosphere by means of a single absorption cell filled with a mixture of CO2 and CH4, and monitoring the wavelength deviations between each outgoing laser pulse and the corresponding seed laser to detect and correct for possible mode pulling effects. Another key requirement is the monitoring of the relative outgoing pulse energies with high accuracy, which is based on a specifically designed optical architecture. Assembly and laboratory tests of the instrument are on-going, the first ground tests are planned for summer 2012.

Amediek, A.; Büdenbender, H.-C.; Ehret, G.; Fix, A.; Kiemle, C.; Quatrevalet, M.; Wirth, M.; Hoffmann, D.; Löhring, J.; Klein, V.

2012-04-01

121

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

PubMed

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

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

2010-02-16

122

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.

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

2010-01-01

123

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

124

Global observations of atmospheric CH4 by Integrated Path Differential-Absorption Lidar: the French-German Climate Monitoring Initiative  

NASA Astrophysics Data System (ADS)

Atmospheric methane (CH4) is a powerful greenhouse gas, which has a Greenhouse Warming Potential (GWP) of 25 relative to CO2 on a time scale of 100 years. Despite the fact that the imbalance between the sources and sinks has decreased in the early 1990's to an insignificant value, a significant renewal of the CH4 growth is reported in recent years. Questions arise whether an increase of atmospheric CH4 might be fostered through melting of permafrost soil in the Arctic region or arise from changes of the tropical wetlands which comprise the biggest natural methane source. Another reason could be the change in the agro-industrial era of predominant human influence or the very large deposits of CH4 as gas hydrates on ocean shelves that are vulnerable to ocean warming. The French-German Climate Monitoring Initiative, which has recently been selected to undergo Phase0/A studies in a joint project by the space agencies CNES (France)and DLR (Germany), targets on satellite observations of atmospheric CH4 for the improvement of our knowledge on regional to synoptic scale CH4 sources on a global basis. As a novel feature, the observational instrument of this mission will be an Integrated Path Differential-Absorption (IPDA) Lidar system embarked on board of the French Myriade platform for the measurement of the column-weighted dry-air mixing ratio of CH4 in a nadir viewing configuration. This data will be provided by the lidar technique with no bias due to particles scattering in the light path and can directly be used as input for flux inversion models. In our presentation we will discuss the observational principle and the sampling strategy of the envisaged mission in connection to the needs for CH4 flux inversion experiments. In addition, we report on supporting campaign activities on airborne measurements of Lidar reflectivity data in the respective spectral region. The airborne data is of prime interest for the generation of pseudo CH4 data examples using the satellite instrument in order to address questions how to optimally aggregate the satellite measurements for maximum information content and minimum error. The field campaign was funded by the European Space Agency (ESA) in the framework of the A-SCOPE mission evaluation activity on active remote sensing of CO2 from space-borne platform.

Ehret, Gerhard; Flamant, Pierre; Ciais, Philippe; Fabien, Gibert; Amediek, Axel; Kiemle, Christoph; Fix, Andreas; Quatrevalet, Mathieu; Wirth, Martin

125

Extended x-ray absorption fine structure measurement of bond-length strain in epitaxial Gd2O3 on GaAs(001)  

Microsoft Academic Search

Extended X-ray absorption fine structure (EXAFS) has been used to measure the bond length in a 23 A epitaxially grown Gd2O3 film on GaAs(001). The Gd-O bond length is determined to be 2.389 ± 0.013 A, which corresponds to an increase of 2.7% or 0.063 A relative to the bond length in bulk Gd2O3 powder. In the plane of the

Erik Nelson; Joseph Woicik; Minghwei Hong

2000-01-01

126

Intercomparison of OH Radical Measurements by Long-Path Absorption and Laser Induced Fluorescence in the Atmosphere Simulation Chamber SAPHIR  

NASA Astrophysics Data System (ADS)

A striking advantage of the SAPHIR chamber is the availability of two spectroscopic detection instruments for OH radicals: Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS). Both instruments have already been compared in 1994 during the field measurement campaign POPCORN. They agreed well with a correlation coefficient of r=0.90 and a weighted linear fit with a slope of 1.09 +- 0.12. However, OH measurements in the simulation chamber differ significantly from measurements in ambient air. While DOAS measures OH as an integral value along the central longitudinal axis of SAPHIR, LIF samples the air locally and close (2 cm) to the floor of the chamber. Thus, the LIF measurements might be possibly affected by local concentration gradients caused by insufficient mixing of the chamber air or by deposition to the wall. On the other hand, if turbulent mixing of the chamber air is weak and high concentrations of ozone are used in experiments, the DOAS instrument might be subject to artificial formation of OH radicals in the air volume which is illuminated by the detection laser. This interference results from laser induced photolysis of ozone and the subsequent reaction of water vapor with the excited oxygen atoms formed. Thus it is of decisive importance to compare OH measurements from both instruments in order to investigate potential disturbing effects due to the specific sampling properties of both instruments within SAPHIR. We report on OH measurements accomplished simultaneously with both instruments using different trace gas compositions and experimental conditions.

Dorn, H.-P.; Brauers, T.; Greif, J.; Häseler, R.; Hofzumahaus, A.; Holland, F.; Rupp, L.

2003-04-01

127

Analysis of sensitivity and optical path-length in non-invasive measurement of glucose with near infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Non-invasive glucose monitoring with optical methods has obtained increasing interest, in that the methods have shown great benefit for diabetes. Nevertheless, low sensitivity and signal to noise ratio (ratio of effective photons) are two major difficulties in non-invasively NIR spectral monitoring of blood glucose concentration. Designing the optical probe properly is one of the effective ways to improve measuring sensitivity and ratio of effective photons. In this paper, definition about ratio of effective photons in measurement of glucose is introduced. And then effect of glucose on optical properties of human skin is analyzed, based on this, two kind of sensitivities for diffuse reflectance, namely sensitivity to absorption and that to scattering, is derived. To investigate the ratio of effective photons and sensitivities, Monte Carlo simulations have been performed on a three-layered media with optical parameters similar to those of human skin. The results have shown that (1) high ratio of effective photons, even as high as 60%, can be obtained by choosing proper the separation between source and detector; (2) sensitivity of diffuse reflectance to absorption and scattering has different dependence on source-detector separation, which enables one can have different options by making use of different effect from glucose level changing. In the end, some suggestions have been put forward to improve precision of measurement of blood glucose.

Luo, Yunhan; Liu, Rong; Chen, Wenliang; Cui, Houxin; Xu, Kexin

2005-03-01

128

Absorption  

NSDL National Science Digital Library

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

Katie Hale (CSUF;)

2002-09-26

129

Application of maximum likelihood estimator in nano-scale optical path length measurement using spectral-domain optical coherence phase microscopy  

PubMed Central

Spectral-domain optical coherence phase microscopy (SD-OCPM) measures minute phase changes in transparent biological specimens using a common path interferometer and a spectrometer based optical coherence tomography system. The Fourier transform of the acquired interference spectrum in spectral-domain optical coherence tomography (SD-OCT) is complex and the phase is affected by contributions from inherent random noise. To reduce this phase noise, knowledge of the probability density function (PDF) of data becomes essential. In the present work, the intensity and phase PDFs of the complex interference signal are theoretically derived and the optical path length (OPL) PDF is experimentally validated. The full knowledge of the PDFs is exploited for optimal estimation (Maximum Likelihood estimation) of the intensity, phase, and signal-to-noise ratio (SNR) in SD-OCPM. Maximum likelihood (ML) estimates of the intensity, SNR, and OPL images are presented for two different scan modes using Bovine Pulmonary Artery Endothelial (BPAE) cells. To investigate the phase accuracy of SD-OCPM, we experimentally calculate and compare the cumulative distribution functions (CDFs) of the OPL standard deviation and the square root of the Cramér-Rao lower bound (1/2SNR) over 100 BPAE images for two different scan modes. The correction to the OPL measurement by applying ML estimation to SD-OCPM for BPAE cells is demonstrated.

Motaghian Nezam, S. M. R.; Joo, C; Tearney, G. J.; de Boer, J. F.

2009-01-01

130

Absorption  

PubMed Central

Given that mind–body interventions constitute a major portion of complementary and alternative medicine used by the public, it seems important to explore those human characteristics that may contribute to the efficacy of mind–body interventions in those who are most likely to benefit. One such characteristic, absorption, reflects an individual’s cognitive capacity for involvement in sensory and imaginative experiences in ways that alter an individual’s perception, memory, and mood with behavioral and biological consequences. Thus, one’s level of absorption may potentially create differential treatment effects in mind–body intervention outcomes. Conducting practical clinical trials helps address the challenge of determining whether a specific mind–body modality intervention may be effective. Such trials may be strengthened by including measures of personality dimensions such as absorption.

Menzies, Victoria; Taylor, Ann Gill; Bourguignon, Cheryl

2009-01-01

131

Integrated absorption intensity and Einstein coefficients for the O2 a 1?g-X 3?g- (0,0) transition: A comparison of cavity ringdown and high resolution Fourier transform spectroscopy with a long-path absorption cell  

NASA Astrophysics Data System (ADS)

The two experimental techniques of cavity ringdown spectroscopy and high-resolution, long-path Fourier transform spectroscopy have been used to measure quantitative absorption spectra and determine the integrated absorption intensity (Sint,B) for the O2 a 1?g-X 3?g- (0,0) band. Einstein A-factors and radiative lifetimes for the O2 a 1?g v=0 state have been derived from the Sint,B values. The two methods give values for the integrated absorption intensity that agree to within 2%. The value recommended from the results of this study is Sint,B=3.10+/-0.10×10-24 cm molecule-1, corresponding to an Einstein-A coefficient of A=2.19+/-0.07×10-4 s-1 and a radiative lifetime of ?rad=76 min. The measurements are in excellent agreement with the recent absorption study of Lafferty et al. [Appl. Opt. 37, 2264 (1998)] and greatly reduce the uncertainty in these parameters, for which accurate values are required for determination of upper stratospheric and mesospheric ozone concentrations.

Newman, Stuart M.; Lane, Ian C.; Orr-Ewing, Andrew J.; Newnham, David A.; Ballard, John

1999-06-01

132

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

133

Optical absorption of pure water in the blue and ultraviolet  

Microsoft Academic Search

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 length up to several meters. As a consequence, it is capable of measuring absorption coefficients as low as 0.001 m-1. The early version of the

Zheng Lu

2006-01-01

134

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

2009-12-17

135

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  

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

136

Long-atmospheric-path measurements of near-visible absorption lines of O2 isotopes and H2O with a prototype AlGaAs laser transceiver system  

Microsoft Academic Search

This paper describes the use of AlGaAs tunable diode lasers for the line-locked wavelength modulation spectroscopic measurements for monitoring of long-path absorption by trace atmospheric species like O2 isotopes and H2O vapor. Theoretical calibration curves were found to be in agreement with measured harmonic signals. Automated sensor operation was demonstrated over several atmospheric paths without the need for realignment or

Neil Goldstein; Steven M. Adler-Golden

1993-01-01

137

A comparison of Arctic BrO measurements by chemical ionization mass spectrometry and long path-differential optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A measurement intensive was carried out in Barrow, Alaska, in spring 2009 as part of the Ocean-Atmosphere-Sea-Ice-Snowpack (OASIS) program. The central focus of this campaign was the role of halogen chemistry in the Arctic. A chemical ionization mass spectrometer (CIMS) performed in situ bromine oxide (BrO) measurements. In addition, a long path-differential optical absorption spectrometer (LP-DOAS) measured the average concentration of BrO along light paths of either 7.2 or 2.1 km. A comparison of the 1 min observations from both instruments is presented in this work. The two measurements were highly correlated and agreed within their uncertainties (R2 = 0.74, slope = 1.10, and intercept = -0.15 pptv). Better correlation was found (R2 = 0.85, slope = 1.04, and intercept = -0.11 pptv) for BrO observations at moderate wind speeds (>3 m s-1 and <8 m s-1) and low nitric oxide (NO) mixing ratios (<100 pptv). The improved agreement is likely due to the elimination of periods when the spatial distribution of BrO is inhomogeneous. The detection limit obtained for the CIMS was 2.6 pptv (3?) for a 4 s integration period, and the estimated uncertainty was ˜30%. The detection limits for the LP-DOAS ranged from 0.7 to 5 pptv (3?) depending on the level of ambient light and the chosen light path, and the estimated systematic error was 10%. The agreement between the CIMS and LP-DOAS is excellent and demonstrates the capability of both instruments to selectively and accurately measure BrO with high sensitivity.

Liao, J.; Sihler, H.; Huey, L. G.; Neuman, J. A.; Tanner, D. J.; Friess, U.; Platt, U.; Flocke, F. M.; Orlando, J. J.; Shepson, P. B.; Beine, H. J.; Weinheimer, A. J.; Sjostedt, S. J.; Nowak, J. B.; Knapp, D. J.; Staebler, R. M.; Zheng, W.; Sander, R.; Hall, S. R.; Ullmann, K.

2011-07-01

138

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

139

Absolute absorption intensities of liquids: the determination of secondary infrared absorption intensity standards; absorption intensities of benzene, chlorobenzene and toluene  

Microsoft Academic Search

The presentation of absorption intensities in infrared spectra is usually limited to relative intensities, instead of absolute intensities. The measurement of absolute intensities would be facilitated by the existence of accepted secondary intensity standards that could be used to calibrate the path length of a transmission cell or the number of reflections in an attenuated total reflection cell. Under the

John E. Bertie; R. N. Jones; Yoram Apelblat; C. D. Keefe

1994-01-01

140

Influence of pressure and atomizer length on absorption curves in ETA-AAS measurements for standardless analysis  

Microsoft Academic Search

A new method for standardless analysis in electrothermal atomic absorption spectroscopy has been recently proposed whose\\u000a implementation requires the use of special atomizers and power supplies not available in the market. Up to now, with the\\u000a proposed method, only volatile elements have been determined with good results because it can be applied only if all atoms\\u000a injected are simultaneously present

F. N. Rossi; D. Melucci; C. Locatelli; P. Reschiglian; G. Torsi; A. Millemaggi

1998-01-01

141

Space-borne remote sensing of CO2, CH4, and N2O by integrated path differential absorption lidar: a sensitivity analysis  

NASA Astrophysics Data System (ADS)

CO2, CH4, and N2O are recognised as the most important greenhouse gases, the concentrations of which increase rapidly through human activities. Space-borne integrated path differential absorption lidar allows global observations at day and night over land and water surfaces in all climates. In this study we investigate potential sources of measurement errors and compare them with the scientific requirements. Our simulations reveal that moderate-size instruments in terms of telescope aperture (0.5 1.5 m) and laser average power (0.4 4 W) potentially have a low random error of the greenhouse gas column which is 0.2% for CO2 and 0.4% for CH4 for soundings at 1.6 ?m, 0.4% for CO2 at 2.1 ?m, 0.6% for CH4 at 2.3 ?m, and 0.3% for N2O at 3.9 ?m. Coherent detection instruments are generally limited by speckle noise, while direct detection instruments suffer from high detector noise using current technology. The wavelength selection in the vicinity of the absorption line is critical as it controls the height region of highest sensitivity, the temperature cross-sensitivity, and the demands on frequency stability. For CO2, an error budget of 0.08% is derived from our analysis of the sources of systematic errors. Among them, the frequency stability of ± 0.3 MHz for the laser transmitter and spectral purity of 99.9% in conjunction with a narrow-band spectral filter of 1 GHz (FWHM) are identified to be challenging instrument requirements for a direct detection CO2 system operating at 1.6 ?m.

Ehret, G.; Kiemle, C.; Wirth, M.; Amediek, A.; Fix, A.; Houweling, S.

2008-03-01

142

Spectroscopy in an extremely thin vapor cell: Comparing the cell-length dependence in fluorescence and in absorption techniques  

SciTech Connect

We compare the behavior of absorption and of resonance fluorescence spectra in an extremely thin Rb vapor cell as a function of the ratio of L/{lambda}, with L the cell thickness (L{approx}150-1800 nm) and {lambda} the wavelength of the Rb D{sub 2} line ({lambda}=780 mn). The Dicke-type coherent narrowing [G. Dutier et al., Europhys. Lett. 63, 35 (2003)] is observed only in transmission measurements, in the linear regime, with its typical collapse and revival, which reaches a maximum for L=(2n+1){lambda}/2 (n integer). It is shown not to appear in fluorescence, whose behavior-amplitude, and spectral width, is more monotonic with L. Conversely, at high-intensity, the sub-Doppler saturation effects are shown to be the most visible in transmission around L=n{lambda}.

Sarkisyan, D.; Varzhapetyan, T.; Sarkisyan, A.; Malakyan, Yu.; Papoyan, A.; Lezama, A.; Bloch, D.; Ducloy, M. [Institute for Physical Research, NAS of Armenia, Ashtarak-2, 378410 Armenia (Armenia); Instituto de Fisica, Facultad de Ingenieria, C.P. 30, Montevideo (Uruguay); Labaratoire de Physique des Lasers, UMR 7538 du CNRS, Universite Paris 13, F-93430 Villetaneuse (France)

2004-06-01

143

CHARM-F: An airborne Integrated Path Differential Absorption (IPDA) LIDAR for the simultaneous measurement of CO2 and CH4 Columns  

NASA Astrophysics Data System (ADS)

Currently, Deutsches Zentrum für Luft- und Raumfahrt (DLR) - in collaboration with Fraunhofer-Institut für Lasertechnik (ILT) and Kayser-Threde GmbH (KT) - is developing CHARM-F, an Integrated Path Differential Absorption (IPDA) LIDAR for simultaneous measurement of CO2 and CH4 columns. Design goal is a compact and rugged instrument optimized for airborne use on board of DLR's long range research aircraft HALO. The main scientific goal of the instrument is to provide precise column measurements of CO2 and CH4 to infer fluxes of these important greenhouse gases by means of inverse modeling. For this purpose, very stringent requirements concerning accuracy and precision have to be met since typical surface sources and sinks alter the total column only by a few percent. To achieve this, CHARM-F uses laser sources emitting pulse-pairs with nanosecond duration which allows for a precise ranging and a proper separation of atmospheric influences (i.e. aerosol and clouds) from the ground return leading to an unambiguously defined column (no airmass factors involved). Two laser systems - one for each trace gas - are employed using highly efficient and robust Nd:YAG lasers to pump optical parametric oscillators (OPO) which convert the pump radiation to the desired measurement wavelengths in the near infrared. Each laser system emits a pulse pair having different wavelengths. One is tuned to an absorption line of the trace gas under consideration and the other one to a nearby wavelength with much less absorption. The close temporal pulse separation of 250 ?s together with a relatively large spot size of 30 m on ground ensures that nearly the same area is illuminated by both pulses. To achieve single-mode operation, both the pump and the OPO are injection seeded. The seed lasers are locked to a gas cell filled with a mixture of CO2 and CH4 to ensure an absolute wavelength calibration. Furthermore, deviations of the wavelength between outgoing laser pulse and the seed lasers are measured to detect and to correct for possible mode pulling effects. A new pulse energy calibration concept using fiber-coupled integrating spheres is employed to allow for a proper normalization of the return signal strength. Assembly and laboratory tests of the instrument will start by end of 2011, the first flight test is planned for fall of 2012. CHARM-F is also intended to serve as an airborne demonstrator for the French-German climate satellite MERLIN that will be launched in 2016.

Wirth, M.; Amediek, A.; Büdenbender, C.; Ehret, G.; Fix, A.; Kiemle, C.; Quatrevalet, M.; Hoffmann, D.; Löhring, J.; Klein, V.; Schöggl, R.

2011-12-01

144

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

SciTech Connect

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

Tschopp, Mark A.; Solanki, K. N.; Gao, Fei; Sun, Xin; Khaleel, Mohammad A.; Horstemeyer, Mark

2012-02-10

145

A two-laser beam technique for improving the sensitivity of low frequency open path tunable diode laser absorption spectrometer (OP-TDLAS) measurements  

NASA Astrophysics Data System (ADS)

Open path tunable diode-laser absorption spectroscopy (OP-TDLAS) is a promising technique to detect low concentrations of possible biogenic gases on Mars. This technique finds the concentration of a gas by measuring the amount of laser light absorbed by gaseous molecules at a specific wavelength. One of the major factors limiting sensitivity in the TDLAS systems operating at low modulation frequencies is 1/f noise. 1/f noise is minimized in many spectroscopy systems by the use of high frequency modulation techniques. However, these techniques require complex instruments that include reference cells and other devices for calibration, making them relatively large and bulky. We are developing a spectroscopy system for space applications that requires small, low mass and low power instrumentation, making the high frequency techniques unsuitable. This paper explores a new technique using two-laser beam to reduce the affect of 1/f noise and increase the signal strength for measurements made at lower frequencies. The two lasers are excited at slightly different frequencies. An algorithm is used to estimate the noise in the second harmonic from the combined spectra of both lasers. This noise is subtracted from the signal to give a more accurate measurement of gas concentration. The error in estimation of 1/f noise is negligible as it corresponds to noise level made at much higher frequencies. Simulation results using ammonia gas and two lasers operating at 500 and 510 Hz respectively shows that this technique is able to decrease the error in estimation of gas concentration to 1/6 its normal value.

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

2013-09-01

146

Evaluation of total emittance of an isothermal nongray absorbing, scattering gas-particle mixture based on the concept of absorption mean beam length  

SciTech Connect

A general methodology to evaluate the total emittance of an isothermal, nongray, isotropically scattering particle-gas mixture is illustrated. Based on the concept of absorption mean beam length (AMBL), the methodology is demonstrated to be computationally efficient and accurate. As an illustration, the total emittance of a slab containing carbon particles and CO[sub 2] is evaluated. The nongray extinction coefficient and scattering albedo of carbon particles are calculated based on Mie theory and the available index of refraction data. The narrow-band fixed-line-spacing model (Edwards et al., 1967) is used to characterize the nongray spectral absorption coefficient of CO[sub 2]. Numerical data show that the combined nongray and scattering effects are quite significant. For particles with moderate and large radius (say, [ge]1[mu]m), ignoring the effect of scattering can lead to error in the prediction of total emittance by more than 20 percent. The no-scattering results also yield incorrect qualitative behavior of the total emittance in terms of its dependence on the mixture temperature and particle concentration. The accuracy of many of the existing predictions of total emittance of gas-particle mixtures that ignore the scattering effect is thus highly uncertain.

Yuen, W.W.; Ma, A. (Univ. of California, Santa Barbara (United States))

1992-08-01

147

Application of a long-path differential optical absorption spectrometer (LP-DOAS) on the measurements of NO 2, SO 2, O 3, and HNO 2 in Gwangju, Korea  

Microsoft Academic Search

A differential optical absorption spectrometer (DOAS) technique has been applied to monitor airborne trace pollutants including NO2, SO2, O3, and HNO2 in the ultraviolet (UV) region (290–350nm) over a 1.5km beam path (two ways) during an intensive measurement campaign held at Gwangju, Korea (March 2002). Their mean mixing ratios (and standard deviations) were computed as 11.3 (8.8), 1.9 (1.7), 17.1

Jeongsoon Lee; Ki-Hyun Kim; Young J. Kim; Jaihoon Lee

2008-01-01

148

Long-atmospheric-path measurements of near-visible absorption lines of O[sub 2] isotopes and H[sub 2]O with a prototype AlGaAs laser transceiver system  

Microsoft Academic Search

Near-visible absorption lines of ambient H[sub 2]O vapor and normal and heavy isotopes of O[sub 2] have been measured over atmospheric paths of up to 0.46 km by using two wavelength-modulated, line-locked AlGaAs laser sources with a retroreflector--telescope system. The absolute signal levels agree with theoretical calculations for the O[sub 2] isotopes to within 2%, which is similar to the

N. Goldstein; S. M. Adler-Golden

1993-01-01

149

Azimuthal Anisotropy of pi Production in Au+Au Collisions at s_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 1 < p{sub T} < 18 GeV/c for Au+Au collisions at {radical}s{sub NN} = 200 GeV. The observed anisotropy shows a gradual decrease for 3 {approx}< p {approx}< 7-10 GeV/c, but remains positive beyond 10 GeV/c. The magnitude of this anisotropy is underpredicted, up to at least {approx}10 GeV/c, by current perturbative QCD (PQCD) energy-loss model calculations. An estimate of the increase in anisotropy expected from initial-geometry modification due to gluon saturation effects and fluctuations is insufficient to account for this discrepancy. Calculations that implement a path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

Adare, A. [University of Colorado, Boulder; Awes, Terry C [ORNL; Cianciolo, Vince [ORNL; Efremenko, Yuri [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Enokizono, Akitomo [Oak Ridge National Laboratory (ORNL); Read Jr, Kenneth F [ORNL; Silvermyr, David O [ORNL; Sorensen, Soren P [University of Tennessee, Knoxville (UTK); Stankus, Paul W [ORNL; PHENIX, Collaboration [The

2010-01-01

150

Binary Decision Diagrams: A Mathematical Model for the Path-Related Objective Functions  

Microsoft Academic Search

This paper describes a mathematical model for all path length parameters (APL: Average Path Length, LPL: Longest Path Length, and SPL: Shortest Path Length) of Binary Decision Diagrams (BDDs). The proposed model is based on an empirical analysis of randomly generated Boolean functions. The formal core of the developed model is a unique equation for the path-related objective functions over

P. W. C. PRASAD; ALI ASSI; BRUCE MILLS

2006-01-01

151

A feasibility study for active remote sensing of atmospheric carbon monoxide based on differential absorption of infrared radiation along vertical paths  

Microsoft Academic Search

The authors describe a differential method for estimating mean concentrations of atmospheric molecular components along a quasivertical rectilinear Earth-air path utilizing a transmitter-receiver pair operating at infrared. The choice of a differential method is due to the need to limit calibration problems without utilizing more complex and costly systems such as DIAL, whose capabilities are definitely oversized for this kind

A. Cuccoli; Luca Facheris; Dino Giuli; Simone Tanelli

2001-01-01

152

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

Microsoft Academic Search

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

SERAPHIN A. SULLIVAN

1963-01-01

153

Fuzzy shortest path problems incorporating interactivity among paths  

Microsoft Academic Search

This paper deals with a shortest path problem on a network in which a fuzzy number, instead of a real number, is assigned to each arc length. Such a problem is “ill-posed” because each arc cannot be identified as being either on the shortest path or not. Therefore, based on the possibility theory, we introduce the concept of “degree of

Shinkoh Okada

2004-01-01

154

Photonic crystal slot waveguide for high sensitivity on-chip near-infrared optical absorption spectroscopy of xylene in water  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a 300?m long silicon photonic crystal slot waveguide for on-chip near-infrared absorption spectroscopy. Based on the Beer-Lambert absorption law, our device combines slow light in photonic crystal waveguide with high electric field intensity in low-index 75nm wide slot, which effectively increases the optical absorption path length of the analyte. We demonstrate near-infrared absorption spectroscopy of xylene in water, independent of near-infrared absorption signatures of water, with a hydrophobic PDMS sensing phase that extracts xylene from water. Xylene concentrations up to 100ppb (parts per billion) (86?g/L) in water were measured.

Chakravarty, Swapnajit; Lai, Wei-Cheng; Wang, Xiaolong; Lin, Che-Yun; Chen, Ray T.

2011-05-01

155

Photonic crystal slot waveguide absorption spectrometer for on-chip near-infrared spectroscopy of xylene in water  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a 300 ?m long silicon photonic crystal slot waveguide near-infrared absorption spectrometer. Based on Beer-Lambert absorption law, our on-chip absorption spectrometer combines slow light in a photonic crystal waveguide with a high electric field intensity in a low-index 75 nm wide slot, which effectively increases the optical absorption path length of the analyte. We demonstrate near-infrared absorption spectroscopy of xylene in water, with a polydimethyl siloxane sensing phase for xylene extraction from water. Xylene concentrations up to 100 ppb (parts per billion) (86 ?g/l) in water were measured.

Lai, Wei-Cheng; Chakravarty, Swapnajit; Wang, Xiaolong; Lin, Cheyun; Chen, Ray T.

2011-01-01

156

Application of a long-path differential optical absorption spectrometer (LP-DOAS) on the measurements of NO(2), SO(2), O(3), and HNO(2) in Gwangju, Korea.  

PubMed

A differential optical absorption spectrometer (DOAS) technique has been applied to monitor airborne trace pollutants including NO(2), SO(2), O(3), and HNO(2) in the ultraviolet (UV) region (290-350 nm) over a 1.5 km beam path (two ways) during an intensive measurement campaign held at Gwangju, Korea (March 2002). Their mean mixing ratios (and standard deviations) were computed as 11.3 (8.8), 1.9 (1.7), 17.1 (19.3), and 0.5 (0.4)ppbv, respectively. As a means to evaluate the performance of the long-path DOAS (LP-DOAS) system with conventional point monitoring systems (PMS), correlation analysis was conducted between the two data sets. These data sets were then inspected to account for the influence of the environmental conditions on the correlation strength between the two systems, especially with respect to light level and wind speed. To facilitate the comparison, correlation analyses were conducted after dividing the data sets for those parameters into several classes. The strength of the correlations between DOAS and meteorological parameters was also examined to evaluate their effects on the DOAS performance. It was found that, among the four pollutant species, O(3) is the most sensitive to changes in meteorological conditions in relation with atmospheric mixing conditions. The overall results of our study indicate that open-path monitoring techniques can be used to effectively diagnose air quality and be substituted for the conventional point monitoring methods with the proper consideration of those parameters affecting the DOAS sensitivity (e.g., light level and wind speed). PMID:17335958

Lee, Jeongsoon; Kim, Ki-Hyun; Kim, Young J; Lee, Jaihoon

2007-03-01

157

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

158

Path Sensitization in Critical Path Problem  

Microsoft Academic Search

Since the delay of a circuit is determined by the delay of its longest sensitizable paths (such paths are called critical paths), the problem of estimating the delay of a circuit is called critical path problem. One important aspect of the critical path problem is to decide whether a path is sensitizable. A framework which allows various previously proposed path

Hsi-chuan Chen; David Hung-chang Du

1991-01-01

159

Diode laser absorption measurements of CH 3 Cl and CH 4 near 1.65 m  

Microsoft Academic Search

Two distributed-feedback (InGaAsP) diode lasers were used to record high-resolution absorption spectra of the parallel and the perpendicular components of the 2 4 band of methyl chloride (CH 3 Cl) and the 2 3 band of methane (CH 4 ) near 1.65 m. The room-temperature absorption measurements, which were conducted in a multipass cell with a variable path length (878

Shang-I. Chou; Douglas S. Baer; Ronald K. Hanson

1997-01-01

160

Differential optical absorption spectroscopy measurement of CO2 using a nanosecond white light continuum.  

PubMed

We built a differential optical absorption spectroscopy system to measure near-surface CO2 absorption in the atmosphere using a nanosecond white light continuum. The white light laser can cover wavelengths ranging from 420 to 2400 nm, where the CO2 and H2O absorption lines are located. At an optical path length of 568 m, it was possible to evaluate atmospheric CO2 concentration from absorption bands of CO2 and H2O in the vicinity of 2000 nm detected by broadband white light simultaneously. PMID:22179882

Somekawa, Toshihiro; Manago, Naohiro; Kuze, Hiroaki; Fujita, Masayuki

2011-12-15

161

Beneficial roles of Al back reflectors in optical absorption of Si nanowire array solar cells  

NASA Astrophysics Data System (ADS)

We investigate the influence of Al back reflectors on the optical absorption spectra of Si nanowire (NW) arrays by using the finite-difference time-domain simulation method. A flat Al layer enhances the absorption in the NW array due to not only the reflection-induced optical path length enlargement but also reflection of light between NWs and localized surface plasmon induced optical field confinement. An Al underlayer with a grating structure allows grating-coupled surface plasmon polariton excitation and raise the optical absorption in the Si NWs. Interplay among all these factors on the optical absorption and expected solar cell performance of the NW arrays is discussed.

Lee, Eunsongyi; Zhou, Keya; Gwon, Minji; Jung, Jin-Young; Lee, Jung-Ho; Kim, Dong-Wook

2013-09-01

162

Measurement of light absorption by aquatic particles: improvement of the quantitative filter technique by use of an integrating sphere approach.  

PubMed

Determination of particulate absorption in natural waters is often made by measuring the transmittance of samples on glass-fiber filters with the so-called quantitative filter technique (QFT). The accuracy of this technique is limited due to variations in the optical properties of the sample/filter composite, and due to uncertainties in the path-length amplification induced by multiple scattering inside the filter. Some variations in the optical properties of the sample/filter composite can be compensated by additional measurements of the filter's reflectance (transmittance-reflectance method [T-R] [S. Tassan and G. M. Ferrari, Limnol. Oceanogr. 40, 1358 (1995)]). We propose a different, rarely used approach, namely to measure the filter's absorptance in the center of a large integrating sphere, to avoid problems with light losses due to scattering. A comparison with other QFTs includes a sensitivity study for different error sources and determination of path-length amplification factors for each measurement technique. Measurements with a point-source integrating-cavity absorption meter were therefore used to determine the true absorption. Filter to filter variability induced a much lower error in absorptance compared to a measured transmittance. This reduced error permits more accurate determination of the usually low absorption coefficient in the near IR spectral region. The error of the T-R method was lower than that of the transmittance measurement but slightly higher than that of an absorptance measurement. The mean path-length amplification was much higher for the absorptance measurement compared to the T-R method (4.50 versus 2.45) but was found to be largely independent of wavelength and optical density. With natural samples the path-length amplification was less variable for the absorptance measurement, reducing the overall error for absorption to less than ±14%, compared to ±25% for the T-R method. PMID:22441480

Röttgers, Rüdiger; Gehnke, Steffen

2012-03-20

163

Time optimal paths for high speed maneuvering  

SciTech Connect

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

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

1993-01-01

164

Intracavity absorption spectroscopy with a tunable multimode traveling-wave ring Ti:sapphire laser.  

PubMed

A tunable multimode unidirectional traveling-wave Ti:sapphire laser was developed to measure in situ the atmospheric absorption spectra using intracavity absorption spectroscopy. The effective absorption path length was 2100 km. O2 and H2O vapor lines in atmosphere with absorption coefficients of 10(-6)-10(-8) cm(-1) were measured with uncertainties <5%, and the absorption coefficients were in agreement with those estimated from the HITRAN database. By tuning the wavelength, a weak absorption line with an absorption coefficient of 10(-9) cm(-1) was measured with a sensitivity of 2×10(-10) cm(-1). The sensitivity was limited by the residual parasitic variation that appeared in the spectrum. PMID:22781240

Ueda, Tomoyuki; Kato, Naoya; Takemura, Akira; Koishi, Hiroyuki; Morinaga, Atsuo

2012-07-10

165

X-ray-absorption near-edge structure of 3d transition elements in tetrahedral coordination: The effect of bond-length variation  

SciTech Connect

The x-ray-absorption near-edge structure (XANES) of transition elements in tetrahedral coordination in crystals and glasses has been studied. We have identified the XANES features in the continuum that can be assigned to multiple scattering within the first coordination shell. The energy positions E/sub r/ of the XANES peaks in the continuum follow the rule (E/sub r/-E/sub b/)d/sup 2/ = const, where E/sub b/ is the energy of the prepeak, defined as the first core excitation to the bound antibonding state of T/sub 2/ symmetry, and d is the interatomic distance. This plot allows us to determine the tetrahedral coordination of a vanadium impurity in a SiO/sub 2/ glass and to get an estimation of the vanadium-oxygen distance (1.77 +- 0.05 A).

Bianconi, A.; Fritsch, E.; Calas, G.; Petiau, J.

1985-09-15

166

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

167

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

168

k-Link Shortest Paths in Weighted Subdivisions  

Microsoft Academic Search

We study the shortest path problem in weighted polygonal subdivisions of the plane, with the additional constraint of an upper bound, k, on the number of links (segments) in the path. We prove structural properties of optimal paths and utilize these results to ob- tain approximation algorithms that yield a path having O(k) links and weighted length at most (1

Ovidiu Daescu; Joseph S. B. Mitchell; Simeon C. Ntafos; James D. Palmer; Chee-keng Yap

2005-01-01

169

Off-axis paths in spherical mirror interferometers  

Microsoft Academic Search

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

D. Herriott; H. Kogelnik; R. Kompfner

1964-01-01

170

TDLAS-based open-path laser hygrometer using simple reflective foils as scattering targets  

NASA Astrophysics Data System (ADS)

We present a new, very simple to use and very easy to align, inexpensive, robust, mono-static optical hygrometer based on tunable diode laser absorption spectroscopy (TDLAS) that makes use of very inexpensive reflective foils as scattering targets at the distant side of the absorption path. Various alternative foils as scattering targets were examined concerning their reflective behaviour and their suitability for TDLAS applications. Using a micro prismatic reflection tape as the optimum scattering target we determined absolute water vapour concentrations employing open path TDLAS. With the reflection tape being in a distance of 75 cm to 1 m (i.e., absorption path lengths between 1.5 and 2 m) we detected ambient H2O concentrations of up to 12,300 ppmv with detectivities of 1 ppm which corresponds to length and bandwidth normalized H2O detection limits of up to 0.9 ppmv m/ sqrt {{Hz}} , which is only a factor of 2 worse than our previous bi-static TDLAS setups (Hunsmann, Appl. Phys. B 92:393-401, 1). This small sensitivity disadvantage is well compensated for by the simplicity of the spectrometer setup and particularly by its extreme tolerance towards misalignment of the scattering target.

Seidel, A.; Wagner, S.; Ebert, V.

2012-11-01

171

An introduction to critical paths.  

PubMed

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

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

172

Paths in m-ary interval trees  

Microsoft Academic Search

We introduce the m-ary interval tree, a random structure that underlies interval division and simultaneous parking problems. Certain significant paths in the m-ary interval trees are considered. When appropriately normed, the length of these paths are shown to converge in distribution to a normal random variable. The work extends the study of incomplete binary interval trees in Itoh and Mahmoud

Mehri Javanian; Hosam M. Mahmoud; Mohammad Vahidi-asl

2004-01-01

173

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

174

Ladybug Lengths  

NSDL National Science Digital Library

This experience focuses studentâs attention on the attributes of length and gives students the opportunity to develop knowledge of and skills in using nonstandard units of measurement. The lesson begins with a connection to children's literature. As students practice measuring length, they do so using nonstandard units.

Math, Illuminations N.

2009-01-28

175

Efficient path profiling  

Microsoft Academic Search

A path profile determines how many times each acyclic path in a routine executes. This type of profiling subsumes the more common basic block and edge profiling, which only approximate path frequencies. Path profiles have many potential uses in program performance tuning, profile-directed compilation, and software test coverage. This paper describes a new algorithm for path profiling. This simple, fast

Thomas Ball; James R. Larus

1996-01-01

176

Flight Path Displays.  

National Technical Information Service (NTIS)

Aircraft display technology has advanced to the state where the flight path display, an integrated format on which both the vertical and horizontal path are graphically represented, is feasible. This report researches efforts made to design flight paths f...

D. A. Warner

1979-01-01

177

Finger Length  

NSDL National Science Digital Library

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

Science Update;

2005-03-28

178

Curvature-constrained directional-cost paths in the plane  

Microsoft Academic Search

This paper looks at the problem of finding the minimum cost curvature-constrained path between two directed points where the\\u000a cost at every point along the path depends on the instantaneous direction. This generalises the results obtained by Dubins\\u000a for curvature-constrained paths of minimum length, commonly referred to as Dubins paths. We conclude that if the reciprocal\\u000a of the directional-cost function

Alan J. Chang; Marcus Brazil; J. Hyam Rubinstein; Doreen A. Thomas

2012-01-01

179

Detection and discrimination using multiple-wavelength differential absorption lidar  

NASA Astrophysics Data System (ADS)

A methodology is presented for generalizing two-wavelength single-material differential absorption lidar to multiple wavelengths for use in simultaneous multimaterial detection and discrimination. A key role in the analysis is played by the concentration path length (CL) product covariance matrix Lambda (CL) which generalizes the CL variance. Detection statistics for a multiwavelength alarm system are computed using Lambda (CL) with a multivariate normal distribution for the estimated CL product values. Off-diagonal elements in Lambda (CL) are found to affect significantly the predicted performance of two-material detection systems.

Warren, R. E.

1985-11-01

180

Robust real-time NURBS path interpolators  

Microsoft Academic Search

In a review of the real-time non-uniform rational B-splines (NURBS) path interpolation method in CNC controllers, it was found that none of the NURBS interpolators described in the literature has the necessary robustness against an extreme knot distribution. The problems begin with the calculation of the total length of the NURBS path: most interpolators handle knots as a global curve

W. T. Lei; S. B. Wang

2009-01-01

181

Cryogenic absorption cells operating inside a Bruker IFS125HR: First results for 13CH 4 at 7 ?m  

Microsoft Academic Search

New absorption cells designed specifically to achieve stable temperatures down to 66K 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 20.38cm were constructed of oxygen free high conductivity (OFHC) copper and

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

2010-01-01

182

Cryogenic absorption cells operating inside a Bruker IFS125HR: First results for 13CH4 at 7 mum  

Microsoft Academic Search

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)

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

2010-01-01

183

Methane absorption in the atmosphere of Jupiter from 1800 to 9500 cm-1 and implications for vertical cloud structure  

Microsoft Academic Search

New measurements of the low-temperature near-infrared absorption of methane (Sihra, 1998, Laboratory measurements of near-infrared methane bands for remote sensing of the jovian atmosphere, Ph.D. thesis, University of Oxford) have been combined with existing, longer path-length, higher-temperature data of Strong et al. (1993, Spectral parameters of self- and hydrogen-broadened methane from 2000 to 9500 cm-1 for remote sounding of the

P. G. J. Irwin; K. Sihra; N. Bowles; F. W. Taylor; S. B. Calcutt

2005-01-01

184

Methane absorption in the atmosphere of Jupiter from 1800 to 9500 cm ?1 and implications for vertical cloud structure  

Microsoft Academic Search

New measurements of the low-temperature near-infrared absorption of methane (Sihra, 1998, Laboratory measurements of near-infrared methane bands for remote sensing of the jovian atmosphere, Ph.D. thesis, University of Oxford) have been combined with existing, longer path-length, higher-temperature data of Strong et al. (1993, Spectral parameters of self- and hydrogen-broadened methane from 2000 to 9500 cm?1 for remote sounding of the

P. G. J. Irwin; K. Sihra; N. Bowles; F. W. Taylor; S. B. Calcutt

2005-01-01

185

Differential optical absorption spectrometer for measuring atmospheric trace gases  

NASA Astrophysics Data System (ADS)

The construction of a differential optical absorption spectrometer (DOAS) is described. The instrument was designed for making automated measurements, with relatively high detection sensitivities, of important tropospheric trace gases, and with the ability to operate in rugged environments without frequent attention. Major innovative features of the instrument include a retroreflector to fold the light path, a diode array detector, and computer-controlled operation of the entire instrument package. The advantages of these modifications with respect to previously reported designs are discussed in detail. This DOAS has been employed since 1989 to measure NO3 (1 ppt), NO2 (0.6 ppb), HONO, O3, and CH2O (0.8 ppb), where the mixing ratios in parentheses indicate the detection limits over a 5 km path length and 4 min integration time, for the species where these could be determined.

Plane, John M. C.; Nien, Chia-Fu

1992-03-01

186

KSPTH: A Subroutine for the K Shortest Paths in a Sabotage Graph.  

National Technical Information Service (NTIS)

Finding shortest paths in a weighted graph model is one way for a safeguards analyst to locate weaknesses in a facility's barrier and alarm system. KSPTH can be used to rank sabotage paths according to path length so that the K shortest paths can be studi...

B. L. Hulme D. B. Holdridge

1977-01-01

187

DISCUSS: Critical Path Analysis  

NSDL National Science Digital Library

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

Hunt, Neville; Baker, Barrie

2009-04-23

188

Optical absorption of pure water in the blue and ultraviolet  

NASA Astrophysics Data System (ADS)

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 length up to several meters. As a consequence, it is capable of measuring absorption coefficients as low as 0.001 m-1. The early version of the ICAM was used previously to measure the absorption spectrum of pure water over the 380-700 nm range. To extend its range into the ultraviolet, several modifications have been completed. The preliminary tests showed that the modified ICAM was able to measure the absorption of pure water for the wavelength down to 300 nm. After extensive experimental investigation and analysis, we found that the absorption of SpectralonRTM (the highly diffusive and reflective material used to build the ICAM) has a higher impact on measurements of absorption in the UV range than we had expected. Observations of high values for pure water absorption in the UV, specifically between 300 and 360 nm, are a consequence of absorption by the Spectralon RTM. These results indicated that even more serious modifications were required (e.g. SpectralonRTM can not be used for a cavity in the UV). Consequently, we developed a new diffuse reflecting material and used fused silica powder (sub-micron level) sealed inside a quartz cell to replace the inner SpectralonRTM cavity of the ICAM. The new data is in excellent agreement with the Pope and Fry data (380-600 nm) and fills the gap between the 320 nm data of Quickenden and Irvin and 380 nm data of Pope and Fry. We present definitive results for the absorption spectrum of pure water between 300 and 600 nm.

Lu, Zheng

189

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

190

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

191

Evaluating the Quality of Clustering Algorithms Using Cluster Path Lengths  

Microsoft Academic Search

\\u000a Many real world systems can be modeled as networks or graphs. Clustering algorithms that help us to organize and understand\\u000a these networks are usually referred to as, graph based clustering algorithms. Many algorithms exist in the literature for\\u000a clustering network data. Evaluating the quality of these clustering algorithms is an important task addressed by different\\u000a researchers. An important ingredient of

Faraz Zaidi; Daniel Archambault; Guy Melançon

2010-01-01

192

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

193

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

194

Genetic algorithm based path planning for a mobile robot  

Microsoft Academic Search

In this paper, a novel genetic algorithm based approach to path planning of a mobile robot is proposed. The major characteristic of the proposed algorithm is that the chromosome has a variable length. The location target and obstacles are included to find a path for a mobile robot in an environment that is a 2D workplace discretized into a grid

Jianping Tu; Simon X. Yangt

2003-01-01

195

Visibility line based methods for UAV path planning  

Microsoft Academic Search

This paper addresses path planning algorithms for an uninhabited aerial vehicle (UAV) based on visibility lines (VL) method for real time applications. VL has been chosen because it provides a solution with optimal path length i.e. minimal distance travelled from starting point to target point. However, as known, the main problem with VL is that the computational burdensome grows exponentially

Rosli Omar; Da-Wei Gu

2009-01-01

196

Optimal shortest path queries in a simple polygon  

Microsoft Academic Search

Let P be a simple polygon with n sides. This paper shows how to preprocess the polygon so that, given two query points p and q inside P, the length of the shortest path inside the polygon from p to q can be found in time &Ogr;(log n). The path itself must be polygonal and can be extracted in additional

Leonidas J. Guibas; John Hershberger

1987-01-01

197

[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

198

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

Microsoft Academic Search

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

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

2008-01-01

199

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.

200

Shortest path algorithms  

Microsoft Academic Search

Theshortest path problem is considered from a computational point of view. Eight algorithms which solve theshortest path tree problem on directed graphs are presented, together with the results of wide-ranging experimentation designed to compare their relative performances on different graph topologies. The focus of this paper is on the implementation of the different data structures used in the algorithms. A

Giorgio Gallo; Stefano Pallottino

1988-01-01

201

Visualizing Paths in Context  

Microsoft Academic Search

Data about movement through a space is increasingly becoming available for capture and analysis. In many applications, this data is captured or modeled as transitions between a small number of areas of interests, or a finite set of states, and these transitions constitute paths in the space. Similarities and differences between paths are of great importance to such analyses, but

Fabio Pellacini; Lori Lorigo; Geri Gay

2006-01-01

202

Agricultural robot path tracking based on predictable path  

Microsoft Academic Search

In order to realize the path tracking of agricultural robot in complex farmland environment and improve its speed and accuracy, a kind of agricultural robot path tracking method based predictable path was put forward in this paper. The definition of predictable path and fitting were presented, the positioning principles and methods were described in detail. The implementation method of path

Chi Gao; Yougang Su; Hui Ma

2010-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

204

Minimal entropy probability paths between genome families.  

PubMed

We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non-rich vectors, does not involve variational theory and does not involve differential equations, but is a better approximation of the minimal entropy path distance than the distance //b-a//(2). We compute minimal entropy distance matrices for examples of DNA myostatin genes and amino-acid sequences across several species. Output tree dendograms for our minimal entropy metric are compared with dendograms based on BLAST and BLAST identity scores. PMID:15133624

Ahlbrandt, Calvin; Benson, Gary; Casey, William

2003-12-02

205

Earth's Atmospheric CO2 Saturated IR Absorption  

NASA Astrophysics Data System (ADS)

Using the on-line SpectraCalc IR absorption simulator, the amount of IR absorption by the 15 ? 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 line is saturated, doubling the CO2 will cause a slight width increase. Using this and the blackbody radiation curve plus considering the effects of water vapor, the temperature rise of the Earth will be less than 2.5 deg. C. Integrating a NASA Martian atmospheric model, we find that the Martian atmosphere has 45 times more CO2 to penetrate than Earth, and yet, the Martian diurnal temperature swings exceed those of the Sahara desert. I.e., large amounts of CO2 alone do not necessarily cause planetary warming. As the oceans warm from any cause, more CO2 is boiled out, but if they cool, they will absorb more CO2 just as a carbonated drink does, so that temperature and CO2 density will correlate. It is to be noted that the Earth's known petroleum reserves contain only enough CO2 to increase the atmospheric CO2 by some 15%.

Wall, Ernst

2008-10-01

206

Spectroscopic method for determination of the absorption coefficient in brain tissue.  

PubMed

I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, ?a. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(?a)+d ln(Is)ln(?a), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes. PMID:21054121

Johansson, Johannes D

207

Path-summation waveforms  

NASA Astrophysics Data System (ADS)

In this paper, we examine an efficient, practical method to calculate approximate, finite-frequency waveforms for the early signals from a point source in 3-D acoustic media with smoothly varying velocity and constant density. In analogy to the use of Feynman path integrals in quantum physics, we obtain an approximate waveform solution for the scalar wave equation by a Monte Carlo summation of elementary signals over a representative sample of all possible paths between a source and observation point. The elementary signal is formed from the convolution of the source time function with a time derivative of the Green's function for the homogeneous problem. For each path, this elementary signal is summed into a time series at a traveltime obtained from an integral of slowness along the path. The constructive and destructive interference of these signals produces the approximate waveform response for the range of traveltimes covered by the sampled paths. We justify the path-summation technique for a smooth medium using a heuristic construction involving the Helmholtz-Kirchhoff integral theorem. The technique can be applied to smooth, but strongly varying and complicated velocity structures. The approximate waveform includes geometrical spreading, focusing, defocusing and phase changes, but does not fully account for multiple scattering. We compare path-summation waveforms with the exact solution for a 3-D geometry involving a low-velocity spherical inclusion, and with finite-difference waveforms for a 2-D structure with realistic, complicated velocity variations. In contrast to geometrical-ray methods, the path-summation approach reproduces finite-frequency wave phenomena such as diffraction and does not exhibit singular behaviour. Relative to the finite-difference numerical method, the path-summation approach requires insignificant computer memory and, depending on the number of waveforms required, up to one to two orders of magnitude less computing time. The sampled paths and associated traveltimes produced by the path summation give a relation between the medium and the signal on the waveform that is not available with finite-difference and finite-element methods. Furthermore, the speed and accuracy of the path-summation method may be sufficient to allow 3-D waveform inversion using stochastic, non-linear, global search methods.

Lomax, Anthony

1999-09-01

208

Tortuous path chemical preconcentrator  

SciTech Connect

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

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

2010-09-21

209

Localization in a disordered multi-mode waveguide with absorption or amplification  

NASA Astrophysics Data System (ADS)

An analytical and numerical study of transmission of radiation through a multi-mode waveguide containing a random medium with a complex dielectric constant ? = ?' + i?'' is presented. Depending on the sign of ?'', the medium is absorbing or amplifying. The transmitted intensity decays exponentially ~ exp(-L/?) as the waveguide length L -> ?, regardless of the sign of ?''. The localization length ? is computed as a function of the mean free path l, the absorption or amplification length ?-1, and the number of modes in the waveguide N. The method used is an extension of the Fokker-Planck approach of Dorokhov, Mello, Pereyra and Kumar to non-unitary scattering matrices. Asymptotically exact results are obtained for N>1 and ? >1/N2l . An approximate interpolation formula for all ? agrees reasonably well with numerical simulations.

Misirpashaev, T. Sh.; Paasschens, J. C. J.; Beenakker, C. W. J.

1997-02-01

210

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.

211

Path integrals and parastatistics  

NASA Astrophysics Data System (ADS)

The propagator and corresponding path integral for a system of identical particles obeying parastatistics are derived. It is found that the statistical weights of topological sectors of the path integral for parafermions and parabosons are simply related through multiplication by the parity of the permutation of the final positions of the particles. Appropriate generalizations of statistics are proposed obeying unitarity and factorizability (strong cluster decomposition). The realization of simple maximal occupancy (Gentile) statistics is shown to require ghost states.

Polychronakos, Alexios P.

1996-02-01

212

PathFinder Science  

NSDL National Science Digital Library

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

213

Efficient Computation of Minimum Exposure Paths in a Sensor Network Field  

Microsoft Academic Search

The exposure of a path p is a measure of the likelihood that an object traveling along p is detected by a network of sensors and it is formally defined as an integral over all points x of p of the sensibility (the strength of the signal coming from x) times the element of path length. The minimum exposure path

Hristo N. Djidjev

2007-01-01

214

A Path Analysis of Variables Influencing Labour Turnover  

Microsoft Academic Search

A brief questionnaire was devised to study the determinants of length of service for a sample of 57 former telephone advertisement sales girls. Path analysis was used to explore the hypothesized complex pattern of interrelationships among the variables. It was found that optimal challenge and social integration had direct effects on length of service. Job evaluation, pressure and higher order

John S. Gow; Alfred W. Clark; Graham S. Dossett

1974-01-01

215

Combined Monte Carlo and path-integral method for simulated library of time-resolved reflectance curves from layered tissue models  

NASA Astrophysics Data System (ADS)

Monte Carlo (MC) simulations are considered the "gold standard" for mathematical description of photon transport in tissue, but they can require large computation times. Therefore, it is important to develop simple and efficient methods for accelerating MC simulations, especially when a large "library" of related simulations is needed. A semi-analytical method involving MC simulations and a path-integral (PI) based scaling technique generated time-resolved reflectance curves from layered tissue models. First, a zero-absorption MC simulation was run for a tissue model with fixed scattering properties in each layer. Then, a closed-form expression for the average classical path of a photon in tissue was used to determine the percentage of time that the photon spent in each layer, to create a weighted Beer-Lambert factor to scale the time-resolved reflectance of the simulated zero-absorption tissue model. This method is a unique alternative to other scaling techniques in that it does not require the path length or number of collisions of each photon to be stored during the initial simulation. Effects of various layer thicknesses and absorption and scattering coefficients on the accuracy of the method will be discussed.

Wilson, Robert H.; Vishwanath, Karthik; Mycek, Mary-Ann

2009-02-01

216

Localization of the start and the end point of a moving stimulus path during eye tracking.  

PubMed

The subjects track visually a smoothly moving light target which increases its brightness at a definite point in the visual field and after traversing a path with a definite length, again decreases its brightness to the initial level. The subjects' task is to localize the start and the end point of this path. Systematic misperceptions are observed in the performance of the task, influenced by the position of the stimulus in the visual field and by the length of the path. The mislocation of the end point of the stimulus path is algebraically smaller than the mislocation of the start point. The data are not in agreement with the hypothesis that the visual system first determines the path length and then determines the path position as a whole. The most probable assumption is accepted to be that the processes of localization of the start and the end point of the path are not independent. PMID:7405590

Mateeff, S

1980-01-01

217

The Calculation of X-Ray Mass Absorption Coefficients  

Microsoft Academic Search

An empirical method of calculating mass absorption coefficients is given. Complete tables of constants are presented for calculating ??&rgr; for all elements and for wave-lengths less than the K critical absorption wave-length. Partial tables give constants for wave-lengths between the L1 and M1 critical wave-lengths.Calculated mass absorption coefficients are given for the common elements.

John A. Victoreen

1949-01-01

218

Binary Trees, Left and Right Paths, WKB Expansions, and Painleve Transcendents  

Microsoft Academic Search

During the 10th Seminar on Analysis of Algorithms, MSRI, Berkeley, June 2004, Knuth posed the problem of analyzing the left and the right path length in a random binary trees. In particular, Knuth asked about properties of the generating function of the joint distribution of the left and the right path lengths. In this paper, we mostly focus on the

Charles Knessl; Wojciech Szpankowski

219

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

Microsoft Academic Search

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

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

1985-01-01

220

Limb Length Discrepancy  

MedlinePLUS

... area. This procedure will not cause an immediate correction in length. Instead, the limb length discrepancy will ... this option include the possibility of slight over-correction or under-correction of the limb length discrepancy. ...

221

Oscillatory fracture paths in thin elastic sheets  

NASA Astrophysics Data System (ADS)

We report results on a novel mode of quasi-static oscillatory crack propagation in thin elastic sheets [1]. A cutting tip of width w is perpendicularly driven through a thin brittle polymer film, held along its lateral boundaries, that progressively cuts the material as it advances [2]. For thin enough cutting tips (w < wc with w_c=0.2mm) the fracture path is straight. However, for w > w_c, the crack follows a well defined and highly reproducible oscillatory path. The amplitude and wavelength of the oscillatory crack paths scale linearly with the width of the cutting tip over a wide range of length scales but are independent of both of the cutting speed and the width of the sheet. We develop a model for this phenomena, based on the coupling between crack propagation and out-of-plane deformations of the film, which exhibits behaviour in remarkably good agreement with the experimental crack paths. [1] B. Roman, P.M. Reis, B. Audoly , S. DeVilliers, V. Viguié, D. Vallet, Oscillatory fracture paths in thin elastic sheets C.R. de Mecanique, vol 331, no 12, p. 811--816 (2003). [2] http://www.lmm.jussieu.fr/platefracture/

Reis, Pedro Miguel; Audoly, Basile; Roman, Benoit

2004-03-01

222

Sampling diffusive transition paths  

SciTech Connect

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

F. Miller III, Thomas; Predescu, Cristian

2006-10-12

223

Demonstration of scan path optimization in proton therapy  

SciTech Connect

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

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

2007-09-15

224

Disorder-induced Limited Path Percolation  

NASA Astrophysics Data System (ADS)

We introduce a model of percolation induced by disorder, where an initially homogeneous network with links of equal weight is disordered by the introduction of heterogeneous weights for the links. We consider a pair of nodes i and j to be mutually reachable when the ratio ?ij of the optimal path length between them before and after the introduction of disorder does not increase beyond a tolerance ratio ?. These conditions reflect practical limitations of reachability better than the usual percolation model, which entirely disregards path length when defining connectivity and, therefore, communication. We find that this model leads to a first-order phase transition in both 2-dimensional lattices and in Erd?s-Rényi networks, and in the case of the latter, the size of the discontinuity implies that the transition is effectively catastrophic, with almost all system pairs undergoing the change from reachable to unreachable. Using the theory of optimal path lengths under disorder, we are able to predict the percolation threshold. For real networks subject to changes while in operation, this model should perform better in predicting functional limits than current percolation models.

López, E.; Braunstein, L. A.

2012-03-01

225

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

226

High-sensitivity near-IR absorption measurements of nanoliter samples in a cavity enhanced fiber sensor  

NASA Astrophysics Data System (ADS)

A compact fiber optic sensor is described using Incoherent Broad-Band Cavity Enhanced Absorption Spectroscopy for sensitive detection of nanoliter samples of aqueous chemicals and microorganisms in capillaries. Absorption was measured in a 70 ?m gap, comparable to the inside diameter of a capillary used for electrophoresis, between the ends of two short segments of multimode fiber. The other ends of the fibers were optically contacted to dielectric mirrors to form an 11-cm cavity resonator. Light from a superluminescent diode (?=1054 nm, BW=35 nm FWHM) was coupled into one end of the cavity, and transmission through the cavity was measured using a silicon photodiode. Dilute aqueous solutions of near infrared dye were used to determine the minimum detectable absorption change of 4x10-6 for 10 second integration and unity signal-to-noise ratio, which is approximately two orders of magnitude more sensitive than previously published results for systems with comparable sample path lengths.

Gomez, Anthony L.; Fruetel, Julia A.; Bambha, Ray P.

2009-08-01

227

Sensitive trace gas detection with cavity enhanced absorption spectroscopy using a continuous wave external-cavity quantum cascade laser  

NASA Astrophysics Data System (ADS)

Trace gas sensing in the mid-infrared using quantum cascade lasers (QCLs) promises high specificity and sensitivity. We report on the performance of a simple cavity enhanced absorption spectroscopy (CEAS) sensor using a continuous wave external-cavity QCL at 7.4 ?m. A noise-equivalent absorption coefficient ?min of 2.6 × 10-8 cm-1 in 625 s was achieved, which corresponds to a detection limit of 6 +/- 1 ppb of CH4 in 15 millibars air for the R(3) transition at 1327.074 cm-1. This is the highest value of noise-equivalent absorption and among the longest effective path length (1780 m) reported to date with QCL-based CEAS.

van Helden, J. H.; Lang, N.; Macherius, U.; Zimmermann, H.; Röpcke, J.

2013-09-01

228

Following the Path  

ERIC Educational Resources Information Center

This article profiles Diane Stanley, an author and illustrator of children's books. Although she was studying to be a medical illustrator in graduate school, Stanley's path changed when she got married and had children. As she was raising her children, she became increasingly enamored of the colorful children's books she would check out of the…

Rodia, Becky

2004-01-01

229

Paths of Innovation  

Microsoft Academic Search

In 1903 the Wright brothers' airplane travelled a couple of hundred yards. Today fleets of streamlined jets transport millions of people each day to cities worldwide. Between discovery and application, between invention and widespread use, there is a world of innovation, of tinkering, improvement and adaptation. This is the world David Mowery and Nathan Rosenberg map out in Paths of

David C. Mowery; Nathan Rosenberg

230

Intrusion Path Analysis.  

National Technical Information Service (NTIS)

The design and implementation of an Intrusion Path Analysis (IPA) function came about as a result of the upgrades to the security systems at the Savannah River Site (SRS), near Aiken, South Carolina. The stated requirements for IPA were broad, leaving opp...

R. D. Hardwick

1989-01-01

231

(Intrusion Path Analysis)  

Microsoft Academic Search

The design and implementation of an Intrusion Path Analysis (IPA) function came about as a result of the upgrades to the security systems at the Savannah River Site (SRS), near Aiken, South Carolina. The stated requirements for IPA were broad, leaving opportunity for creative freedom during design and development. The essential elements were that it: be based on alarm and

Hardwick

1989-01-01

232

Paths to Remarriage  

Microsoft Academic Search

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

Graham B. Spanier; Paul C. Glick

1980-01-01

233

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

234

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

PubMed

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

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

2006-09-01

235

Optimal Path and Minimal Spanning Trees in Random Weighted Networks  

Microsoft Academic Search

We review results on the scaling of the optimal path length in random\\u000anetworks with weighted links or nodes. In strong disorder we find that the\\u000alength of the optimal path increases dramatically compared to the known small\\u000aworld result for the minimum distance. For Erd\\\\H{o}s-R\\\\'enyi (ER) and scale\\u000afree networks (SF), with parameter $\\\\lambda$ ($\\\\lambda >3$), we find that

Lidia A. Braunstein; Zhenhua Wu; Yiping Chen; Sergey V. Buldyrev; Tomer Kalisky; Sameet Sreenivasan; Reuven Cohen; Eduardo López; Shlomo Havlin; H. Eugene Stanley

2007-01-01

236

Absorption and Photoinduced Absorption of Aniline Oligomers.  

NASA Astrophysics Data System (ADS)

We have prepared aniline oligomers of 4 (tetramer), 8 (octamer) and 16 (hexadecamer) rings in length in the emeraldine oxidation state. The absorption spectra of oligomers show a gradual change in the energy of the molecular exciton peak from 2.2 eV for the tetramer to 2.0 eV for the polymer with no concomitant significant change in the higher energy peak at ~ 4.0 eV. We also report the longtime photoinduced absorption for tetramer, octamer and hexadecamer. The photoinduced features of the hexadecamer, i.e., peaks at ~ 1.5 eV and ~ 3.2 eV, bleaching at ~ 2.0 eV have their analogs in the polymer(R.P. McCall et al.) Phys. Rev. B 41, 5202 (1990); K.A. Coplin et al. Phys. Rev. Lett. 72, 3206 (1994). while the additional peak at ~ 1.8 eV was observed only in the octamer and tetramer. The similarity between photoinduced spectra of polymer and oligomers demonstrates that photoexcited states in polyaniline have a short length scale. This contrasts with data for sexithiophene(J. Poplawski et al.) Mol. Cryst. Liq. Cryst. 256, 407 (1994). and ? -carotene(E. Ehrenfreund et al.) Chem. Phys. Lett. 196, 84 (1992).. The results will be discussed in the context of models for excited states for polyanilines.

Saprigin, A.; Epstein, A. J.; Feng, J.; Zhang, W. J.; MacDiarmid, A. G.

1997-03-01

237

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

PubMed

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

Le, Trang; Tao, Shiquan

2011-07-11

238

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

SciTech Connect

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

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

1993-08-01

239

Force Microscopy Using Common-Path Optical-Heterodyne Interferometer  

NASA Astrophysics Data System (ADS)

This paper proposes a common-path optical-heterodyne interferometer for developing a very stable force microscope. The deflections of the force-sensing cantilever are detected by the optical heterodyne method which reduces low-frequency noise. The optical system is a common-path interferometer using a Wollaston prism, which reduces the effects of mechanical vibrations and perturbation of the optical path length. In this paper, we proposed the optical system, constructed a system and measured the surface profile of optical disk grooves.

Kikuta, Hisao; Asai, Shigeki; Yasukochi, Hiroyuki; Iwata, Koichi

1991-03-01

240

Path Loss Model for Non-Line-of-Sight Ultraviolet Multiple Scattering Channels.  

National Technical Information Service (NTIS)

An ultraviolet (UV) signal transmission undergoes rich scattering and strong absorption by atmospheric particulates. We develop a path loss model for a Non-Line-of-Sight (NLOS) link. The model is built upon probability theory governing random migration of...

B. M. Sadler H. Ding Z. Xu

2010-01-01

241

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...

242

Optical hygrometer using differential absorption of hydrogen Lyman-alpha radiation  

Microsoft Academic Search

An optical hygrometer based on the differential absorption of the H Lyman-alpha line has been designed and built for use in atmospheric field studies. The absorption is determined along two separate paths containing sample and dry reference air, respectively, hence eliminating undesired absorption by O2. At the same time the differential absorption eliminates problems related to intensity variations in the

Andre Zuber; Georg Witt

1987-01-01

243

Exact train pathing  

Microsoft Academic Search

Suppose we are given a schedule of train movements over a rail network into which a new train is to be included. The origin\\u000a and the destination are specified for the new train; it is required that a schedule (including the path) be determined for\\u000a it so as to minimize the time taken without affecting the schedules for the old

Viswanath Nagarajan; Abhiram G. Ranade

2008-01-01

244

Adaptive Fast Path Architecture  

Microsoft Academic Search

Adaptive Fast Path Architecture (AFPA) is a software architecture that dramatically improves the efficiency, and therefore the capacity, of Web and other network servers. The architecture includes a RAM-based cache that serves static content and a reverse proxy that can distribute requests for dynamic content to multiple servers. These two mechanisms are combined using a ?exible layer-7 (content-based) routing facility.

Elbert C. Hu; Philippe Joubert; Robert B. King; Jason D. Lavoie; John M. Tracey

2001-01-01

245

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

246

Nutrient absorption.  

PubMed

Many advances in the study of nutrient absorption have been made with the use of molecular and genetic techniques; however, standard in vivo studies have provided interesting and important new information. Omega-3 long-chain fatty acids have unexpected effects on lipoprotein formation and secretion in neonatal intestinal cells; this needs to be considered in the modification of infant formulas. Rexinoids affect intestinal cholesterol homeostasis via two receptors: retinoic acid receptor/liver X receptor (cholesterol efflux to lumen) and retinoic acid receptor/farnesoid X receptor (cholesterol catabolism). Absorption of the antioxidant plant polyphenol quercetin involves interaction with the glucose transporter and deglycolsylation and conjugation reactions. Cells of the polarized human colon cancer cell line, CaCo-2, take up phenylalanine by two mechanisms: passive uptake across the basolateral membrane, and temperature-dependent transcellular movement from apical to basolateral media. Absorption of vitamins A and E is markedly enhanced in normal and damaged intestine by the administration of restructured triacylglycerols derived from fish oil and medium-chain fatty acids. Surprisingly, dietary protein and phosphorus apparently have no significant effect on the efficiency of calcium absorption in adult women. Finally, many studies examined a variety of genes that regulate iron absorption and homeostasis. PMID:17033282

Nutting, David F; Kumar, N Suresh; Siddiqi, Shadab A; Mansbach, Charles M

2002-03-01

247

Signal optimization, noise reduction, and systematic error compensation methods in long-path DOAS measurements  

Microsoft Academic Search

The increment of the exploitable optical path represents one of the most important efforts in the differential optical absorption spectroscopy (DOAS) instruments improvement. The methods that allow long path measurements in the UV region are presented and discussed in this paper. These methods have been experimented in the new Italian DOAS instrument - SPOT - developed and manufactured by Kayser

Emilio Simeone; Alessandro Donati

1998-01-01

248

Arc Length Gone Global  

ERIC Educational Resources Information Center

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

Boudreaux, Gregory M.; Wells, M. Scott

2007-01-01

249

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

250

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.

Bleakley, Hoyt; Lin, Jeffrey

2012-01-01

251

Byrds Flight Path  

NSDL National Science Digital Library

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

Biddlecome, Tom; Snodgrass, Stuart; Newcombe, Marte; Jezek, Ken

1999-11-08

252

Semiclassical Ehrenfest paths  

NASA Astrophysics Data System (ADS)

Trajectories are a central concept in our understanding of classical phenomena and also in rationalizing quantum mechanical effects. In this work we provide a way to determine semiclassical paths, approximations to quantum averages in phase space, directly from classical trajectories. We avoid the need of intermediate steps, like particular solutions to the Schroedinger equation or numerical integration in phase space by considering the system to be initially in a coherent state and by assuming that its early dynamics is governed by the Heller semiclassical approximation. Our result is valid for short propagation times only, but gives non-trivial information on the quantum-classical transition.

Liberalquino, Rafael; Parisio, Fernando

2013-08-01

253

The Path of Pollution  

NSDL National Science Digital Library

This lesson plan has students follow the path of pollution from the Chernobyl nuclear accident. They will name and locate countries to which radiation traveled and describe how air pollution moves from one area to another. In addition they will compare the chronological sequence of radiation travel with geographic distribution. Provided are: essential elements, objective, focus, a list of materials, background information, procedure, and ideas for extension and evaluation. Links provide the history of the accident and the data required to complete the investigation.

254

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

255

Photodeactivation paths in norbornadiene.  

PubMed

The first high level ab initio quantum-chemical calculations of potential energy surfaces (PESs) for low-lying singlet excited states of norbornadiene in the gas phase are presented. The optimization of the stationary points (minima and conical intersections) and the recalculation of the energies were performed using the multireference configuration interaction with singles (MR-CIS) and the multiconfigurational second-order perturbation (CASPT2) methods, respectively. It was shown that the crossing between valence V2 and Rydberg R1 states close to the Franck-Condon (FC) point permits an easy population switch between these states. Also, a new deactivation path in which the doubly excited state with (?3)(2) configuration (DE) has a prominent role in photodeactivation from the R1 state due to the R1/DE and the DE/V1 conical intersections very close to the R1 and DE minima, respectively, was proposed. Subsequent deactivation from the V1 to the ground state goes through an Olivucci-Robb-type conical intersection that adopts a rhombic distorted geometry. The deactivation path has negligible barriers, thereby making ultrafast radiationless decay to the ground state possible. PMID:23553256

Antol, Ivana

2013-04-03

256

pathChirp: Efficient Available Bandwidth Estimation for Network Paths  

SciTech Connect

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, pathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, pathChirp does not require synchronous nor highly stable clocks at the sender and receiver. We test pathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using only a fraction of the number of probe bytes that current state-of-the-art techniques use.

Cottrell, Les

2003-04-30

257

Planck Length and Cosmology  

NASA Astrophysics Data System (ADS)

We show that an unification of quantum mechanics and general relativity implies that there is a fundamental length in Nature in the sense that no operational procedure would be able to measure distances shorter than the Planck length. Furthermore we give an explicit realization of an old proposal by Anderson and Finkelstein who argued that a fundamental length in nature implies unimodular gravity. Finally, using hand waving arguments we show that a minimal length might be related to the cosmological constant which, if this scenario is realized, is time dependent.

Calmet, Xavier

258

pathChirp: Efficient Available Bandwidth Estimation for Network Paths  

Microsoft Academic Search

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing

Les

2003-01-01

259

A new calibration system for lightweight, compact and mobile Cavity-Enhanced Differential Optical Absorption Spectroscopy instruments  

NASA Astrophysics Data System (ADS)

Absorption Spectroscopy has been employed for several decades now to study the earth's atmosphere. While the focus has been on remote sensing for a long time, lately there has been a renewed interest in in-situ methods, as point measurements allow an easier interpretation for highly inhomogeneous distributions of gases of interest compared to the integration approach of most remote sensing methods. One comparatively new method offering both advantages of in-situ measurements as well as being contactless is open-path Cavity-Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS). Broadband open-path CE-DOAS instruments have been used for ten years now, and in the meantime allow the measurement of numerous atmospheric trace gases (e.g. NO2, NO3, IO, CHOCHO, HCHO). While those instruments were bulky and not very mobile at first, recent developments resulted in relatively lightweight (< 30 kg) instruments with a relatively low power consumption allowing mobile open-path measurements at remote field locations. An important operational issue has been the path length calibration in the field, necessary for the determination of the concentration of measured gases. Until now, often calibration gases were used with different scattering properties than air or known concentrations. However this methods has several major shortcomings, being rather inconvenient and cumbersome in the field with the need for compressed gas cylinders, as well as time consuming, preventing a quick check of the state of the instrument in the field after changing measurement locations. Here we present a new wavelength-resolved method for broadband CE-DOAS path length calibration. A small, custom made ring-down system is employed with a pulsed LED as light source. The wavelength is then resolved by tilting a narrow band interference filter. The system not only allows quick, automated path length calibrations without physical interaction on the instrument, but also saves weight, space and the necessity to transport compressed gas cylinders, which is a great advantage e.g. for measurements in remote coastal areas or polar regions. The technical implementation is presented and compared to other CE-DOAS calibration methods.

Zielcke, Johannes; Horbanski, Martin; Pöhler, Denis; Frieß, Udo; Platt, Ulrich

2013-04-01

260

Shortest Paths in Euclidean Space with Polyhedral Obstacles.  

National Technical Information Service (NTIS)

This document considers the problem of finding a minimum length path between two points in Euclidean space which avoids a set (not necessarily convex) polyhedral obstacles; we let n denote the number of the obstacle edges and k denote the number of island...

J. H. Reif J. A. Storer

1985-01-01

261

Dynamic path planning in sensor-based terrain acquisition  

Microsoft Academic Search

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

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

1990-01-01

262

Recent Results From the JPL Carbon Dioxide Laser Absorption Spectrometer  

Microsoft Academic Search

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

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

2007-01-01

263

Evaluation of an Open-Path Fourier Transform Infrared Spectrophotometer Using an Exposure Chamber  

Microsoft Academic Search

This study investigated the use of a controlled outdoor exposure chamber to evaluate the accuracy of an open-path Fourier transform infrared (OP-FTIR) spectrometer, using path lengths that are found in the workplace. A range of stable homogenous pollutant concentrations of toluene and cyclohexane were generated in the chamber, multiple backgrounds were taken throughout each sampling day, and open-path measurements were

L. A. Todd

1996-01-01

264

Fast real-time NURBS path interpolation for CNC machine tools  

Microsoft Academic Search

In this paper, a novel fast real-time non-uniform rational B-spline (NURBS) path interpolation method is presented. This method efficiently integrates the data processing of a NURBS path in a CNC controller, from pre-processing to real-time interpolation. In the calculation of the total length of the NURBS path, the numerical adaptive quadrature method adapts to the integrand, i.e. the first derivative

W. T. Lei; M. P. Sung; L. Y. Lin; J. J. Huang

2007-01-01

265

Development of an open path THz transmissometer for deterministic and random propagation studies  

NASA Astrophysics Data System (ADS)

The design of an open-path 320 GHz - 340 GHz coherent transmissometer for experimental measurements of amplitude scintillation, phase scintillation, angle-of-arrival (AoA) fluctuations, and transverse coherence near the 325.1529 GHz water absorption resonance is presented. The system uses a uni-directional transmitter and two phase-coherent receivers with adjustable transverse. The objective of the experiment is to verify and improve existing propagation models for use by designers of applied THz systems for remote sensing, radiolocation, or communications. System stability will be verified using a short range near-ground test path of several ~10's of meters length using a cable for locking the transmitter local oscillator (LO) to the receivers' LOs. This short range configuration, similar to tests conducted at Flatville, Illinois during the 1980s, permits characterization of system errors in all of the above parameters, thus yielding a baseline for the long range experiments. Characterization of the phase-coherent RF link will be studied vis-à-vis anticipated theoretical performance based on the Rytov approximation. The system will then be configured for long term open-path measurements on a 1.78 km elevated link between the University of Colorado at Boulder (CU) and the National Telecommunications and Information Administration (NTIA) Mesa site at the NOAA-NIST campus in Boulder, Colorado. The system will provide long range coherent THz propagation statistics during continuous longduration study of turbulent atmospheric propagation effects over an extensive array of atmospheric conditions in a realistic operational environment.

Scally, Lawrence J.; Gasiewski, Albin J.; Fritz, Jason

2012-05-01

266

Steered transition path sampling.  

PubMed

We introduce a path sampling method for obtaining statistical properties of an arbitrary stochastic dynamics. The method works by decomposing a trajectory in time, estimating the probability of satisfying a progress constraint, modifying the dynamics based on that probability, and then reweighting to calculate averages. Because the progress constraint can be formulated in terms of occurrences of events within time intervals, the method is particularly well suited for controlling the sampling of currents of dynamic events. We demonstrate the method for calculating transition probabilities in barrier crossing problems and survival probabilities in strongly diffusive systems with absorbing states, which are difficult to treat by shooting. We discuss the relation of the algorithm to other methods. PMID:22779577

Guttenberg, Nicholas; Dinner, Aaron R; Weare, Jonathan

2012-06-21

267

Steered transition path sampling  

NASA Astrophysics Data System (ADS)

We introduce a path sampling method for obtaining statistical properties of an arbitrary stochastic dynamics. The method works by decomposing a trajectory in time, estimating the probability of satisfying a progress constraint, modifying the dynamics based on that probability, and then reweighting to calculate averages. Because the progress constraint can be formulated in terms of occurrences of events within time intervals, the method is particularly well suited for controlling the sampling of currents of dynamic events. We demonstrate the method for calculating transition probabilities in barrier crossing problems and survival probabilities in strongly diffusive systems with absorbing states, which are difficult to treat by shooting. We discuss the relation of the algorithm to other methods.

Guttenberg, Nicholas; Dinner, Aaron R.; Weare, Jonathan

2012-06-01

268

A distributed shortest path protocol  

NASA Astrophysics Data System (ADS)

We present a distributed protocol for obtaining the shortest paths between all pairs of nodes in a network with weighted links. The protocol is based on an extension of the Dijkstra (centralized) shortest path algorithm and uses collaboration between neighboring nodes to transfer the information needed at the nodes for the successive construction of the shortest paths. A formal description of the protocol is given by indicating the exact algorithm performed by each node. The validation proofs are greatly simplified by separating the communication mechanism from the computation at the nodes, the latter being the transposition of the Dijkstra shortest path algorithm to the decentralized protocol.

Zerbib, F. B. M.; Segall, A.

1981-06-01

269

An Analytical Approach to Optimize NC Tool Path Planning for Face Milling Flat Convex Polygonal Surfaces  

Microsoft Academic Search

CAD\\/CAM systems currently generate the tool cutter path for many NC operations. However no mathematical model is available for computing an optimal tool cutter path for face milling. By utilizing such a model, the minimum length of cut can be identified for face milling flat surfaces. In this paper, the authors present an analytical procedure from which the optimal cutting

HSU-PIN WANG; HENG CHANG; RICHARD A. WYSK

1988-01-01

270

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path Switching or History-Aware Path Switching?  

Microsoft Academic Search

Multihoming Intelligent Route Control (IRC) plays a significant role in improving the performance of Internet accesses. However,\\u000a in a competitive environment, IRC systems may introduce persistent route oscillations, causing significant performance degradation.\\u000a In this study, three design alternatives to cope with this issue are investigated: Randomized Path Monitoring, Randomized\\u000a Path Switching and History-aware Path Switching. The simulation results show that

Alexandre Fonte; José Martins; Marilia Curado; Edmundo Monteiro

2008-01-01

271

Measurements of direct path and folded path optical scintillation path weightings  

NASA Astrophysics Data System (ADS)

A theoretical prediction by Dr. Avihu Ze'evi of the relative contribution to the optical scintillation by different points along the path was described by a weight function for direct and exact folded path spherical wave sources. In an effort to verify this prediction a turbulence chamber was built to allow a controlled turbulence source to be moved and measured at different path positions in conjunction with scintillation measurements. The experimental results follow Dr. Ze'evi's general pattern but both sources are less weighted at the detector end than predicted and the folded path is more heavily weighted at the target end than predicted.

Costantine, A. G.

1983-06-01

272

Path Diversity Aware Interdomain Routing  

Microsoft Academic Search

Abstract—As the Internet becomes the critical information infrastructure for both personal and business applications, fast and reliable routing protocols need to be designed to maintain the performance of those applications in the presence of failures. Today’s interdomain routing protocol, BGP, is known to be slow in reacting and recovering from network failures. Increasing path diversity by advertising multiple paths is

Feng Wang; Lixin Gao

2009-01-01

273

Fracture paths and ultrananocrystalline diamond  

Microsoft Academic Search

We use the simulated fracture of ultrananocrystalline diamond (UNCD) to illustrate how different fracture paths can result in different predictions of system properties. At zero temperature, the system is unable to explore the potential energy surface far from the fracture path being investigated. This can result in misleading predictions for the mechanical properties of UNCD. In non-zero temperature simulations, the

Jeffrey T. Paci; Lipeng Sun; Ted Belytschko; George C. Schatz

2005-01-01

274

Path Analysis: A Brief Introduction.  

ERIC Educational Resources Information Center

Path analysis is presented as a technique that can be used to test on a priori model based on a theoretical conceptualization involving a network of selected variables. This being an introductory source, no previous knowledge of path analysis is assumed, although some understanding of the fundamentals of multiple regression analysis might be…

Carducci, Bernardo J.

275

Obstacle avoidance and path planning  

Microsoft Academic Search

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

Stephen Cameron

1994-01-01

276

Coefficients of Effective Length.  

ERIC Educational Resources Information Center

Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

Edwards, Roger H.

1981-01-01

277

Length of Stay  

PubMed Central

Five methodologies for predicting hospital length of stay were developed and compared. Two—a subjective Bayesian forecaster and a regression forecaster—also measured the relative importance of the symptomatic and demographic factors in predicting length of stay. The performance of the methodologies was evaluated with several criteria of effectiveness and one of cost. The results should provide encouragement for those interested in computer applications to utilization review and to scheduling inpatient admissions.

Gustafson, David H.

1968-01-01

278

An advanced open-path atmospheric monitor design  

SciTech Connect

The conceptual design of an open-path atmospheric monitor combines an acousto-optic tunable filter for emission spectroscopy (3-14 {mu}m) with a mid-IR (4.6-5.4 {mu}m) for absorption spectroscopy. It utilizes mostly commercially available components, covers a large area ({approximately}4 km radius), measures the distance to any reflecting object, can take measurements along any line-of-sight, and is eye safe. Of twenty test pollutants it is to detect, the concentrations of all twenty will be measurable via emission spectroscopy and ten by the more sensitive absorption spectroscopy.

Taylor, L.; Suhre, D. [Westinghouse Electric Corp., Pittsburgh, PA (United States); Mech, S. [Westinghouse Hanford Co., Richland, WA (United States)

1996-05-01

279

Editorial: Redefining Length  

SciTech Connect

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

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

2011-07-15

280

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

NASA Astrophysics Data System (ADS)

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.; Yu, W.; Zhuo, H. B.; Zhou, C. T.; Ma, Y. Y.; Yang, X. H.; Yu, T. P.; Zou, D. B.; Luan, S. X.; Yin, Y.; Shao, F. Q.; Peng, X. J.

2013-07-01

281

The Energy Dependence of the Fragmentation Parameters and Interaction Mean Free Paths in Nuclear Emulsion for Heavy Cosmic Ray Nuclei.  

National Technical Information Service (NTIS)

It is generally assumed that the fragmentation parameters and absorption mean free paths used in extrapolating the charge spectrum of cosmic ray nuclei to the top of the atmosphere are independent of energy. However recent results suggest that these quant...

T. E. Cleghorn

1967-01-01

282

A stochastic wire length distribution for gigascale integration (GSI)  

Microsoft Academic Search

Based on Rent's Rule, a well established empirical relationship, a rigorous derivation of a complete wire length distribution for on-chip random logic networks is performed. This distribution is used to enhance a critical path model; to derive a preliminary dynamic power dissipation model; and to describe optimal architectures for multilevel wiring networks that provide maximum interconnect density

Jeffrey A. Davis; V. K. De; J. D. Meindl

1997-01-01

283

ABSORPTION ANALYZER  

DOEpatents

A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

1961-11-14

284

Optimal Shortest Path Queries in a Simple Polygon  

Microsoft Academic Search

Abstract Let P be a simple polygon with n sides. This paper shows how to preprocess,the polygon so that, given two query points p and q inside P, the length of the shortest,path,inside the polygon($#$to q can be found,in time,O(Iogn). The path,itself must,be polygonal and can be extracted,in additional,time proportional,to the number,of turns,it makes.,The preprocessing consists of triangulation,plus a linear

Leonidas J. Guibas; John Hershberger

1989-01-01

285

Far-from-equilibrium measurements of thermodynamic length  

SciTech Connect

Thermodynamic length is a path function that generalizes the notion of length to the surface of thermodynamic states. Here, we show how to measure thermodynamic length in far-from-equilibrium experiments using the work fluctuation relations. For these microscopic systems, it proves necessary to define the thermodynamic length in terms of the Fisher information. Consequently, the thermodynamic length can be directly related to the magnitude of fluctuations about equilibrium. The work fluctuation relations link the work and the free energy change during an external perturbation on a system. We use this result to determine equilibrium averages at intermediate points of the protocol in which the system is out-of-equilibrium. This allows us to extend Bennett's method to determine the potential of mean force, as well as the thermodynamic length, in single molecule experiments.

Feng, Edward H.; Crooks, Gavin E.

2008-11-05

286

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.

287

Variable focal length microlenses  

NASA Astrophysics Data System (ADS)

Refractive surface relief microlenses (150 ?m diameter) are immersed in nematic liquid crystal in a cell. Application of a variable voltage across the cell effectively varies the refractive index of the liquid crystal and results in a change of the focal length by the lensmakers formula (E. Hecht, Optics, 2nd edn., Addison-Wesley, Reading, Massachusetts, 1987, p. 138). We describe the cell design and construction and demonstrate a range of focal lengths from +490 to +1000 ?m for 2 to 12 V applied. A diverging lens results when the voltage is lower. Theoretical models are developed to account for some of the observed aberrations.

Commander, L. G.; Day, S. E.; Selviah, D. R.

2000-04-01

288

Squeezed States and Path Integrals.  

National Technical Information Service (NTIS)

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 ...

I. Daubechies J. R. Klauder

1992-01-01

289

Sampling by Length.  

ERIC Educational Resources Information Center

Discussion of sampling methods used in information science research focuses on Fussler's method for sampling catalog cards and on sampling by length. Highlights include simple random sampling, sampling with probability equal to size without replacement, sampling with replacement, and examples of estimating the number of books on shelves in certain…

Handley, John C.

1991-01-01

290

Reversible variable length codes  

Microsoft Academic Search

Proposes some reversible variable length codes (RVLCs) which can be decoded instantaneously both in the forward and backward directions and have high transmission efficiency. These codes can be used, for example, in the backward reconstruction of video signals from the data last received when some signal is lost midway in the transmission. Schemes for a symmetrical RVLC requiring only a

Y. Takishima; M. Wada; H. Murakami

1995-01-01

291

Sampling by Length.  

ERIC Educational Resources Information Center

|Discussion of sampling methods used in information science research focuses on Fussler's method for sampling catalog cards and on sampling by length. Highlights include simple random sampling, sampling with probability equal to size without replacement, sampling with replacement, and examples of estimating the number of books on shelves in…

Handley, John C.

1991-01-01

292

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

293

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

294

Real Time Path Integral Methods  

Microsoft Academic Search

An efficient methodology has been developed for simulating the long-time dynamics of quantum dissipative processes modeled in terms of a system coupled to a multidimensional harmonic bath. The starting point is expression of the path integral in terms of a quasi-adiabatic propagator which allows large time increments. The resulting quasi-adiabatic propagator path integral is evaluated on a system-specific discrete variable

Nancy Makri

1998-01-01

295

Formal Language Constrained Path Problems  

Microsoft Academic Search

Given an alphabet ?, a (directed) graph G whose edges are weighted and ?-labeled, and a formal language L ? ??, the formal-language-constrained shortest\\/simple path problem con- sists of finding a shortest (simple) path p in G complying with the additional constraint that l(p) ? L. Here l(p) denotes the unique word obtained by concatenating the ?-labels of the edges

Christopher L. Barrett; Riko Jacob; Madhav V. Marathe

1998-01-01

296

[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

297

Path matched vibration insensitive Fizeau interferometer  

NASA Astrophysics Data System (ADS)

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization path matching mechanism. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. Microwave modulation of a high powered red laser diode is used to create a 15 mW laser source having a coherence length of 250 um with minimal sidelobe ringing. With a 15 mW source, the maximum camera shutter speed, used when measuring a 4% reflector, was 150 usec, resulting in very robust vibration insensitivity. Additionally, stray light interference is substantially reduced due to the source's short coherence, allowing the measurement of thin transparent optics. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers. This work starts with a basic review of interferometry, phase shifting, and polarization as a lead in to a description of the theory and operation of the pixelated mask spatial carrier phase shifting technique. An analysis of the standard Fizeau Interferometer is then given. This is followed by detailed theoretical discussion of the path matched vibration insensitive (PMVI) Fizeau, which includes a theoretical model of the effects of multiple beam return from the test surface when measuring high value reflectors. The coherence properties of laser diodes are then discussed, a theoretical model for the effects of high frequency drive current is derived, and experimental results are given. Finally, the performance of the PMVI Fizeau is experimentally analyzed, potential error sources discussed, and suggestions for improvements provided.

Kimbrough, Bradley Trent

298

Modulated microwave absorption in superconducting mercury  

SciTech Connect

Modulated microwave absorption spectra associated with the intermediate state have been observed at 15.1 GHz for an oblong mercury sample. The use of a liquid-helium bath eliminated the thermal instabilities associated with modern, gas-flow cooling systems. Differences in the absorption signals observed with low modulation amplitudes, which depend on the direction of passage through the intermediate region, could be due to either the supercooling of the normal state below /ital H//sub /ital c// or the dependence of the domain topology on the thermodynamic path.

Rubins, R. S.; Black, T. D.; Jeong, D. Y.

1989-08-01

299

Gait adaptations to different paths of stair descent.  

PubMed

Gait characteristics during stair descent have been characterized for a straight descent path; however, pedestrians are likely to encounter a variety of staircase designs that allow one to descend at an angle (i.e. an oblique or monumental staircase). The purpose of this study was to determine the temporospatial lower limb joint kinematics differences between descending a staircase on straight versus oblique descent paths. Sixteen subjects (8 males, 8 females) descended a staircase under three different conditions: straight descent and at a 25° and 45° angle compare to the straight path. Cycle time, cadence, speed, step width, and step length were significantly affected by descent angle, while the proportion of the cycle dedicated to the stance and swing phases remained constant over the descent paths. Peak knee flexion angle increased by approximately 2.5° in the 45° condition compared to the 0° condition (p=0.0044); however, the remainder of the time series was unchanged. A decreased step width and increased step length occurred to allow the foot to sufficiently clear the steps. Changes in the temporospatial variables, hip joint angle and a constant stance/swing proportion demonstrates that these adaptations may be made to maintain characteristics of the gait cycle and prevent subjects from adopting an unfamiliar gait pattern. PMID:23583606

Gallagher, Kaitlin M; Vandenbussche, Jessica; Callaghan, Jack P

2013-04-11

300

Critical line length determination  

Microsoft Academic Search

One of the most severe faults for a circuit breaker to interrupt is the short-line fault (SLF). In this paper, digital testing is applied to determine the critical line length, i.e. the short-line fault percentage that stresses the circuit breaker most, for three different circuit breakers. Three arc models have been used for the calculations and three indicators have been

P. H. Schavemaker; L. van der Sluis; A. J. P. de Lange

2000-01-01

301

Atomic Absorption Spectroscopy.  

National Technical Information Service (NTIS)

Contents: Theory of atomic absorption measurements; Atomic-absorption spectrophotometers; The preparation of absorbing media. General principles; Flames; Graphite cuvettes; and Some special applications of the atomic-absorption method.

V. V. Lvov

1969-01-01

302

Extending differential optical absorption spectroscopy for limb measurements in the UV  

Microsoft Academic Search

Methods of UV\\/VIS absorption spectroscopy to determine the constituents in the Earth's atmosphere from measurements of scattered light are often based on the Beer-Lambert law, like e.g. Differential Optical Absorption Spectroscopy (DOAS). Therefore they are strictly valid for weak absorptions and narrow wavelength intervals (strictly only for monochromatic radiation). For medium and strong absorption (e.g. along very long light-paths like

S. Kühl; T. Deutschmann; U. Platt; T. Wagner

2009-01-01

303

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.

2013-06-01

304

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

305

Attenuation of Photosynthetically Active Radiation by Aerosols and Characterization of Aerosol Absorption from AERONET  

NASA Astrophysics Data System (ADS)

Accurate knowledge of the intensity of incident photosynthetically active radiation (PAR; 400-700 nm) at the surface is important for understanding possible effects on crop productivity and on the net primary productivity of natural ecosystems. Not only the magnitude of the PAR irradiance but also the distribution of that irradiance into direct and diffuse components can have an effect on photosynthesis. In many regions clouds are the primary attenuator of PAR flux, however in some regions there are significant reductions in PAR irradiance at the surface due to aerosol attenuation. The two primary aerosol optical parameters affecting PAR attenuation are the aerosol optical depth which is related to particulate concentration in the total column, and aerosol absorption which is related to the black carbon concentration for pollution and biomass burning aerosols. Model computations show the magnitude of reduction in PAR irradiance as optical depth increases and as aerosol absorption increases, and the increases in diffuse fraction as aerosol optical depth increases and decreases in diffuse fraction as absorption increases. Examples are shown of the retrieval of aerosol absorption (parameterized by the single scattering albedo) from measurements of irradiance and diffuse fraction in conjunction with spectral aerosol optical depth in the PAR wavelength interval. Since PAR flux reduction by aerosols increases as optical path length increases, there is also the effect of greater attenuation in early morning and late afternoon, possibly reducing the effective photoperiod. We also show aerosol absorption retrievals from the new Version 2.0 AERONET retrievals that are more accurate than Version 1.0 due to better characterization of surface reflectance, providing the basic aerosol characterization needed to estimate cloudless sky PAR fluxes.

Eck, T. F.; Holben, B. N.; Schafer, J. S.; Sinyuk, A.; Smirnov, A.; Slutsker, I.

2007-05-01

306

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

307

Dynamic behavior of shortest path routing algorithms for communication networks  

NASA Astrophysics Data System (ADS)

Several proposed routing algorithms for store and forward communication networks, including one currently in operation in the ARPANET, route messages along shortest paths computed by using some set of link lengths. When these lengths depend on current traffic conditions as they must in an adaptive algorithm, dynamic behavior questions such as stability convergence, and speed of convergence are of interest. This paper is the first attempt to analyze systematically these issues. It is shown that minimum queuing delay path algorithms tend to exhibit violent oscillatory behavior in the absence of a damping mechanism. The oscillations can be damped by means of several types of schemes, two of which are analyzed in this paper. In the first scheme a constant bias is added to the queuing delay thereby providing a preference towards paths with a small number of links. In the second scheme the effects of several past routings are averaged as, for example, when the link lengths are computed and communicated asynchronously throughout the network.

Bertsekas, D. P.

1980-06-01

308

A Unified Approach to Path Problems  

Microsoft Academic Search

A general method is described for solving path problems on directed graphs. Such path problems include finding shortest paths, solving sparse systems of hnear equaUons, and carrying out global flow analysis of computer programs The method consists of two steps First, a collecUon of regular expressions representmg sets of paths m the graph Is constructed This can be done by

Robert Endre Tarjan; TAR JAN

1981-01-01

309

Underwater path planing using fast marching algorithms  

Microsoft Academic Search

In this paper, new tools for obstacle avoidance and path planning for underwater vehicles are presented. The authors' technique, based on a level set formulation of the path planning problem, extracts optimal paths from complex and continuous environments in a complete and consistent manner. Fast marching algorithm is known to be efficient for finding cost optimal path in mobile robotics

Clément Pêtrès; Yan Pailhast; Yvan Petilloti; Dave Lanes

2005-01-01

310

Paths, Trees and Cycles in Tournaments  

Microsoft Academic Search

We survey results on paths, trees and cycles in tournaments. The main subjects are hamiltonian paths and cycles, vertex and arc disjoint paths with prescribed endvertices, arc-pancyclicity, oriented paths, trees and cycles in tour- naments. Several unsolved problems are included.

Jørgen Bang-Jensen; Gregory Gutin

311

Not-so-resonant, resonant absorption  

SciTech Connect

When an intense electromagnetic wave is incident obliquely on a sharply bounded overdense plasma, strong energy absorption can be accounted for by the electrons that are dragged into the vacuum and sent back into the plasma with velocities vapprox. =v/sub osc/. This mechanism is more efficient than usual resonant absorption for v/sub osc//..omega..>L, with L being the density gradient length. In the very high-intensity CO/sub 2/-laser--target interaction, this mechanism may account for most of the energy absorption.

Brunel, F.

1987-07-06

312

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

SciTech Connect

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

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

2005-05-15

313

The temperature dependence of the absorption edge in bismuth vanadate crystals (BiVO4)  

Microsoft Academic Search

The temperature dependence of the absorption edge in bismuth vanadate single crystal was measured, and it has turned out that the absorption edge shifts towards the longer wave-length side with increasing temperature

Yoshihiro Ishibashi; Takashi Fujii; Akikatsu Sawada

1982-01-01

314

Wound complications and stitch length  

Microsoft Academic Search

The effect of suturing with a very short stitch on the development of wound complications in midline incisions was investigated. Three hundred sixty-eight patients were analysed. The suture length to wound length ratio and mean stitch length were calculated. Wound infection occurred in 4% (four of 103) of patients sutured with a mean stitch length of less than 4 cm, in

D. Millbourn; L. A. Israelsson

2004-01-01

315

On the general false path problem in timing analysis  

Microsoft Academic Search

The false path problem is often referred to as the problem of detecting the longest sensitizable path (A path which is not a false path is a sensitizable path). The term “false path” is not clearly defined. In this paper, we first give a clear and precise definition of a false path. Then the general false path problem is formulated.

David Hung-Chang Du; S. H. Yen; Subbarao Ghanta

1989-01-01

316

Hierarchical Encoded Path Views for Path Query Processing: An Optimal Model and Its Performance Evaluation  

Microsoft Academic Search

Efficient path computation is essential for applications such as intelligent transportation systems (ITS) and network routing. In ITS navigation systems, many path requests can be submitted over the same, typically huge, transportation network within a small time window. While path precomputation (path view) would provide an efficient path query response, it raises three problems which must be addressed: 1) precomputed

Ning Jing; Yun-wu Huang; Elke A. Rundensteiner

1998-01-01

317

Modifying Fragility and Length Scales of Polymer Glass Formation with Nanoparticles  

NASA Astrophysics Data System (ADS)

We investigate the effects of nanoparticles on glass formation in a model polymer melt by molecular dynamics simulations. The addition of nanoparticles allows us to change the glass transition temperature Tg, the fragility of glass formation, and both static and dynamical length scales in a controlled fashion. We contrast the length scales of static density changes with the length scale over which nanoparticles perturb the dynamics, as well as the length scale of cooperative string-like motion. Using the Adam-Gibbs approach, we show how the changes of fragility can be interpreted as a measure of the scale of cooperative string-like motion. We contrast the behavior along isobaric and isochoric paths to Tg, and find that changes along an isobaric path (most relevant experimentally) are much smaller than those along an isochoric path.

Pazmino, Beatriz A.; Douglas, Jack F.; Starr, Francis W.

2012-02-01

318

Profilometry using two-photon absorption of silicon avalanche photodiode  

NASA Astrophysics Data System (ADS)

Though silicon photodetectors are usually insensitive to near infrared light of the wavelength longer than 1100 nm, they become sensitive to it with high intensity, producing photocurrent in proportion to the square of the intensity. This is due to two-photon absorption (TPA) process. So far, the TPA process in silicon photodetectors has mainly been applied to measuring the waveform of optical short pulses, since it can give the intensity correlation of incident light signals. In this paper, as a new application of the TPA process in photodetectors, we propose a novel profilometry based on Michelson interferometer with optical microwave as a light source and avalanche photodiode as a two-photon absorber. In contrast to the classical heterodyne profilometer that measures the optical path length difference from the phase of the modulated optical signal, the dynamic range of the TPA method is not limited by the bandwidth of a photodetector and attached electronic devices. The TPA method can realize the dynamic range of several millimeters to several ten meters with simple setup. The principle of the TPA based profilometry is experimentally demonstrated using fiber optic Michelson interferometer.

Tanaka, Yusuke; Kurokawa, Takashi

2002-09-01

319

Career Paths of Academic Deans.  

ERIC Educational Resources Information Center

|This paper examines various career paths leading to deanship and considers the implications of the findings for women and minorities who aspire to this position. The paper is part of a larger study of academic deanship conducted by the Center for Academic Leadership at Washington State University between October 1996 and January 1997. Data for…

Wolverton, Mimi; Gonzales, Mary Jo

320

Employer Resource Manual. Project Path.  

ERIC Educational Resources Information Center

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

Kane, Karen R.; Del George, Eve

321

Complexity of Path Forming Games.  

National Technical Information Service (NTIS)

For a number of two player games where players alternately choose the next vertex of a simple or elementary path in a graph, the authors considers the problem to determine whether for a given game instance there is a winning strategy for the first player....

H. L. Bodlaender

1989-01-01

322

Alternative Nuclear Paths To 2050  

Microsoft Academic Search

he circumstances surrounding nuclear power worldwide and the importance that may be given to issues affecting its future development point toward very different alternative paths over the next 50 years. Economic deregulation, lack of competitiveness in some countries, negative public perception and concerns about waste issues suggest that nuclear power might decrease progressively with a potential phase-out of the technology

Ivan Vera; Evelyne Bertel; Geoffrey Stevens

323

Thinking on the Write Path  

ERIC Educational Resources Information Center

The present paper underscores the importance of the cognitive orientation of English as a Foreign Language (EFL) students in their success in writing courses. A few suggestions are made as to how EFL teachers can put their students on the right cognitive path in their writings.

Salmani-Nodoushan, Mohammad Ali

2007-01-01

324

Beam wander experiments: terrestrial path  

Microsoft Academic Search

We report on a set of measurements made in December 2005 by researchers from the University of Central Florida, SPAWAR's Innovative Science and Technology Experiment Facility (ISTEF), Harris Corporation, NASA Kennedy Space Center, and Northrop Grumman. The experiments were conducted on the Shuttle Landing Facility (SLF) at Kennedy Space Center (KSC) over terrestrial paths of 1, 2, and 5 km.

R. L. Phillips; L. C. Andrews; J. Stryjewski; B. Griffis; M. Borbath; D. Galus; G. Burdge; K. Green; C. Kim; D. Stack; C. Harkrider; D. Wayne; D. Hand; J. Kiriazes

2006-01-01

325

Perceived Shrinkage of Motion Paths  

ERIC Educational Resources Information Center

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

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

2009-01-01

326

The path to adaptive microsystems  

Microsoft Academic Search

Scaling trends in microsystems are discussed frequently in the technical community, providing a short-term perspective on the future of integrated microsystems. This paper looks beyond the leading edge of technological development, focusing on new microsystem design paradigms that move far beyond today's systems based on static components. We introduce the concept of Adaptive Microsystems and outline a path to realizing

John C. Zolper; Michael J. Biercuk

2006-01-01

327

Methylmercury determination using a hyphenated high performance liquid chromatography ultraviolet cold vapor multipath atomic absorption spectrometry system  

Microsoft Academic Search

The present work investigates the use of a multipath cell atomic absorption mercury detector for mercury speciation analysis in a hyphenated high performance liquid chromatography assembly. The multipath absorption cell multiplies the optical path while energy losses are compensated by a very intense primary source. Zeeman-effect background correction compensates for non-specific absorption. For the separation step, the mobile phase consisted

Reinaldo C. Campos; Rodrigo A. Gonçalves; Geisamanda P. Brandão; Marlo S. Azevedo; Fabiana Oliveira; Julio Wasserman

2009-01-01

328

Allometry of Paracellular Absorption in Birds  

Microsoft Academic Search

Water-soluble nutrients can be absorbed across the intestinal epithelium by transcellular and paracellular processes. Recent studies suggest that small birds (!180 g) have more extensive paracellular absorption of glucose than nonflying mammals. This may be a feature that compensates for a reduced small intestine size because small birds have smaller mass-corrected intestinal length than do nonflying mammals, but the difference

2008-01-01

329

Polyelectrolyte persistence length: Attractive effect of counterion correlations and fluctuations  

NASA Astrophysics Data System (ADS)

The persistence length of a single, strongly charged, stiff polyelectrolyte chain is investigated theoretically. Path integral formulation is used to obtain the effective electrostatic interaction between the monomers. We find significant deviations from the classical Odijk, Skolnick and Fixman (OSF) result. An induced attraction between monomers is due to thermal fluctuations and correlations between bound counterions. The electrostatic persistence length is found to be smaller than the OSF value and indicates a possible mechanical instability (collapse) for highly charged polyelectrolytes with multivalent counterions. In addition, we calculate the amount of condensed counterions on a slightly bent polyelectrolyte. More counterions are found to be adsorbed as compared to the Manning condensation on a cylinder.

Ariel, G.; Andelman, D.

2003-01-01

330

Possible connection between the optimal path and flow in percolation clusters  

NASA Astrophysics Data System (ADS)

We study the behavior of the optimal path between two sites separated by a distance r on a d -dimensional lattice of linear size L with weight assigned to each site. We focus on the strong disorder limit, i.e., when the weight of a single site dominates the sum of the weights along each path. We calculate the probability distribution P(?opt?r,L) of the optimal path length ?opt , and find for r?L a power-law decay with ?opt , characterized by exponent gopt . We determine the scaling form of P(?opt?r,L) in two- and three-dimensional lattices. To test the conjecture that the optimal paths in strong disorder and flow in percolation clusters belong to the same universality class, we study the tracer path length ?tr of tracers inside percolation through their probability distribution P(?tr?r,L) . We find that, because the optimal path is not constrained to belong to a percolation cluster, the two problems are different. However, by constraining the optimal paths to remain inside the percolation clusters in analogy to tracers in percolation, the two problems exhibit similar scaling properties.

López, Eduardo; Buldyrev, Sergey V.; Braunstein, Lidia A.; Havlin, Shlomo; Stanley, H. Eugene

2005-11-01

331

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

332

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...

333

Colloidal quantum dot photovoltaics: a path forward.  

PubMed

Colloidal quantum dots (CQDs) offer a path toward high-efficiency photovoltaics based on low-cost materials and processes. Spectral tunability via the quantum size effect facilitates absorption of specific wavelengths from across the sun's broad spectrum. CQD materials' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements represent important first steps toward commercially compelling performance. Here we review advances in device architecture and materials science. We diagnose the principal phenomenon-electronic states within the CQD film band gap that limit both current and voltage in devices-that must be cured for CQD PV devices to fulfill their promise. We close with a prescription, expressed as bounds on the density and energy of electronic states within the CQD film band gap, that should allow device efficiencies to rise to those required for the future of the solar energy field. PMID:21967723

Kramer, Illan J; Sargent, Edward H

2011-10-12

334

Coaxial atomizer liquid intact lengths  

Microsoft Academic Search

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

Hasan Eroglu; Norman Chigier; Zoltan Farago

1991-01-01

335

Physarum can compute shortest paths.  

PubMed

Physarum polycephalum is a slime mold that is apparently able to solve shortest path problems. A mathematical model has been proposed by Tero et al. (Journal of Theoretical Biology, 244, 2007, pp. 553-564) to describe the feedback mechanism used by the slime mold to adapt its tubular channels while foraging two food sources s(0) and s(1). We prove that, under this model, the mass of the mold will eventually converge to the shortest s(0)-s(1) path of the network that the mold lies on, independently of the structure of the network or of the initial mass distribution. This matches the experimental observations by Tero et al. and can be seen as an example of a "natural algorithm", that is, an algorithm developed by evolution over millions of years. PMID:22732274

Bonifaci, Vincenzo; Mehlhorn, Kurt; Varma, Girish

2012-06-23

336

NASA: a path dependent organization  

Microsoft Academic Search

Mission agencies like NASA are complex systems, connecting people with science and technology to accomplish the desired tasks. Path dependence can help explain why NASA and other mission agencies often sacrifice long-term capabilities for short-term survival. The National Aeronautics and Space Act of 1958, followed by President Kennedy’s challenge, catapulted NASA to the moon, encouraged human exploration, and sped up

David Bruggeman

2002-01-01

337

Conditional Length of Stay.  

PubMed Central

OBJECTIVE: To develop and test a new outcome measure, Conditional Length of Stay (CLOS), to assess hospital performance when deaths are rare and complication data are not available. DATA SOURCES: The 1991 and 1992 MedisGroups National Comparative Data Base. STUDY DESIGN: We use engineering reliability theory traditionally applied to estimate mechanical failure rates to construct a CLOS measure. Specifically, we use the Hollander-Proschan statistic to test if LOS distributions display an "extended" pattern of decreasing hazards after a transition point, suggesting that "the longer a patient has stayed in the hospital, the longer a patient will likely stay in the hospital" versus an alternative possibility that "the longer a patient has stayed in the hospital, the faster a patient will likely be discharged from the hospital." DATA COLLECTION/EXTRACTION METHODS: Abstracted records from 7,777 pediatric pneumonia cases and 3,413 pediatric appendectomy cases were available for analysis. PRINCIPAL FINDINGS: For both conditions, the Hollander-Proschan statistic strongly displays an "extended" pattern of LOS by day 3 (p<.0001) associated with declining rates of discharge. This extended pattern coincides with increasing patient complication rates. Worse admission severity and chronic disease contribute to lower rates of discharge after day 3. CONCLUSIONS: Patient stays tend to become prolonged after complications. By studying CLOS, one can determine when the rate of hospital discharge begins to diminish--without the need to directly observe complications. Policymakers looking for an objective outcome measure may find that CLOS aids in the analysis of a hospital's management of complicated patients without requiring complication data, thereby facilitating analyses concerning the management of patients whose care has become complicated.

Silber, J H; Rosenbaum, P R; Koziol, L F; Sutaria, N; Marsh, R R; Even-Shoshan, O

1999-01-01

338

Folded-Light-Path Colloidal Quantum Dot Solar Cells  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

339

Folded-light-path colloidal quantum dot solar cells.  

PubMed

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

2013-07-01

340

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

341

Path integral on star graph  

NASA Astrophysics Data System (ADS)

In this paper we study path integral for a single spinless particle on a star graph with N edges, whose vertex is known to be described by U(N) family of boundary conditions. After carefully studying the free particle case, both at the critical and off-critical levels, we propose a new path integral formulation that correctly captures all the scale-invariant subfamily of boundary conditions realized at fixed points of boundary renormalization group flow. Our proposal is based on the folding trick, which maps a scalar-valued wave function on star graph to an N-component vector-valued wave function on half-line. All the parameters of scale-invariant subfamily of boundary conditions are encoded into the momentum independent weight factors, which appear to be associated with the two distinct path classes on half-line that form the cyclic group Z2. We show that, when bulk interactions are edge-independent, these weight factors are generally given by an N-dimensional unitary representation of Z2. Generalization to momentum dependent weight factors and applications to worldline formalism are briefly discussed.

Ohya, Satoshi

2012-06-01

342

Combined interferometric and absorption-spectroscopic technique for determining molecular line strengths: Applications to CO{sub 2}  

SciTech Connect

A diode-laser-based technique has been developed for absolute line strength measurements with high precision and accuracy, combining a spectroscopic determination of the integrated absorbance with an optical measurement of the absorption path length by means of a Michelson interferometer. This method has been applied to several {sup 12}C{sup 16}O{sub 2} vibrorotational transitions belonging to the {nu}{sub 1}+2{nu}{sub 2}{sup 0}+{nu}{sub 3} combination band, in the spectral region around 2 {mu}m. The 1{sigma} overall accuracy in line strength determination ranges between 0.4% and 0.7%, while the experimental reproducibility is estimated to be around 0.1%. To our knowledge, these levels are the highest ever reached before. The pressure-broadening coefficients for the same transitions are also reported.

Castrillo, A.; Gagliardi, G.; Casa, G.; Gianfrani, L. [Dipartimento di Scienze Ambientali, Seconda Universita di Napoli, and INFM-Gruppo Coordinato Napoli 2, Via Vivaldi 43, I-81100 Caserta (Italy)

2003-06-01

343

Application of a tunable-diode-laser absorption diagnostic for CO measurements in an automotive HCCI engine.  

SciTech Connect

An infrared laser absorption technique has been developed to measure in-cylinder concentrations of CO in an optical, automotive HCCI engine. The diagnostic employs a distributed-feedback, tunable diode laser selected to emit light at the R15 line of the first overtone of CO near 2.3 {micro}m. The collimated laser beam makes multiple passes through the cylinder to increase its path length and its sampling volume. High-frequency modulation of the laser output (wavelength modulation spectroscopy) further enhances the signal-to-noise ratio and detection limits of CO. The diagnostic has been tested in the motored and fired engine, exhibiting better than 200-ppm sensitivity for 50-cycle ensemble-average values of CO concentration with 1-ms time resolution. Fired results demonstrate the ability of the diagnostic to quantify CO production during negative valve overlap (NVO) for a range of fueling conditions.

Steeper, Richard R.; Fitzgerald, Russell Paul

2010-08-01

344

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

345

The Absorption of Incident Quanta by Atoms as Defined by the Mass Photoelectric Absorption Coefficient and the Mass Scattering Coefficient  

Microsoft Academic Search

Evidence presented indicates that the absorption of quanta as defined by the mass photoelectric absorption coefficient ??&rgr; and the mass scattering coefficient ??&rgr; of any element may be represented by a simple expression.Tabulated values of the calculated mass absorption coefficients ??&rgr; are given for wave-lengths from 0.01 to 40 angstroms for hydrogen and carbon and from 0.01 to ?K and

John A. Victoreen

1948-01-01

346

Distillation and absorption  

SciTech Connect

Two volumes, focusing on dynamics and control, packing, absorption and other mass transfer processes, synthesis and simulation, trays, and vapor liquid equilibria. These volumes are reference sources for distillation and absorption, equipment manufacture, and pharmaceuticals.

Haselden, G.G.

1988-01-01

347

Water vapor absorption coefficients in the 8-13-micron spectral region - A critical review  

Microsoft Academic Search

Measurements of water vapor absorption coefficients in the thermal IR atmospheric window (8-13 microns) during the past 20 years obtained by a variety of techniques are reviewed for consistency and compared with computed values based on the AFGL spectral data tapes. The methods of data collection considered were atmospheric long path absorption with a CO2 laser or a broadband source

William B. Grant

1990-01-01

348

Multiple scattering in the presence of absorption: a theoretical treatment for quasi one-dimensional systems  

NASA Astrophysics Data System (ADS)

We consider propagation of waves in a disordered medium, extending the treatment of quasi one-dimensional systems, due to Dorokhov and to Mello et al to include absorption. In particular, we obtain within this approach the probability distribution of the reflection matrix for a semi-infinite system, as a function of the ratio of the mean free paths for absorption and scattering.

Bruce, N. A.; Chalker, J. T.

1996-07-01

349

The Absorption Spectrum of UF6, from 2000 to 4200 Å  

Microsoft Academic Search

The absorption spectrum of UF6 between 3400 and 4200 Å, is well-documented, but the region below 3400 Å has not been studied in any detail. We present here a spectrum of UF6 between 2000 and 4200 Å that shows significant structure below 3400 Å. The absorption in this region must be observed at very low pressures and relatively short path

G. L. Depoorter; C. K. Rofer-depoorter

1975-01-01

350

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

Microsoft Academic Search

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

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

2009-01-01

351

Lateral Path Controller Design for Autonomous Airship  

Microsoft Academic Search

According to the path control problem for unmanned autonomous airship, the lateral path mathematic model was introduced based on the scheme of control system and a kind of lateral path design method of autonomous airship is proposed based on fuzzy logic and adaptive sliding mode control (ASMC). The movement model and dynamic model of autonomous airship is derived from considering

Guo Jian-guo; Zhou Jun

2010-01-01

352

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

353

Chip layout optimization using critical path weighting  

Microsoft Academic Search

A chip layout procedure for optimizing the performance of critical timing paths in a synchronous digital circuit is presented. The procedure uses the path analysis data produced by a static timing analysis program to generate weights for critical nets on clock and data paths. These weights are then used to bias automatic placement and routing in the layout program. This

A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kozak; M. Wiesel

1984-01-01

354

Chip layout optimization using critical path weighting  

Microsoft Academic Search

A chip layout procedure for optimizing the performance of critical timing paths in a synchronous digital circuit is presented. The procedure uses the path analysis data produced by a static timing analysis program to generate weights for critical nets on clock and data paths. These weights are then used to bias automatic placement and routing in the layout program. This

A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kazak

1988-01-01

355

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

356

Randomized path coloring on binary trees  

Microsoft Academic Search

Motivated by the problem of WDM routing in all-optical networks, we study the following NP-hard problem. We are given a directed binary tree T and a set R of directed paths on T. We wish to assign colors to paths of R, in such way that no two paths that share a directed arc of T are assigned the same

Vincenzo Auletta; Ioannis Caragiannis; Christos Kaklamanis; Pino Persiano

2002-01-01

357

Removing False Paths from Combinational Modules 1  

Microsoft Academic Search

The existence of false paths complicates the task of accurate tim- ing analysis significantly. A technique to remove false paths from a combinational circuit without degrading its performance h as a prac- tical value since topological timing analysis is then good e nough to estimate the performance of false-path-free circuits accu rately. One can think of the KMS algorithm (1)

Yuji Kukimoto; Robert K. Brayton

358

Variability of calcium absorption  

Microsoft Academic Search

Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately

R. P. Heaney; R. R. Recker; S. M. Hinders

1988-01-01

359

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

360

Preserving Topology Confidentiality in Inter-Domain Path Computation Using a Path-Key-Based Mechanism  

Microsoft Academic Search

Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (TE) Label Switched Paths (LSPs) may be computed by Path Computation Elements (PCEs). Where the TE LSP crosses multiple domains, such as Autonomous Systems (ASes), the path may be computed by multiple PCEs that cooperate, with each responsible for computing a segment of the path. However, in some cases (e.g.,

A. Farrel

361

UV differential optical absorption method for measuring sulfur content in coal  

NASA Astrophysics Data System (ADS)

Determining the sulfur content in coal rapidly and accurately can provide a technical basis for the enterprises and the environmental administration departments. A novel method for measuring the sulfur content in coal based on UV differential optical absorption is presented in this paper. However, compared with the applications in atmosphere monitoring, the UV differential optical absorption spectroscopy (DOAS) for the sulfur content measurement in coal has the problems that the concentration range of SO2 in the flue gas is wider and the optical path-length of the gas cell is shorter. To solve these problems, an improved DOAS algorithm based on a finite impulse response (FIR) filter and a nonlinear compensation technique is proposed. An experimental measurement system based on the modified DOAS is designed and established. The standard SO2 gas and five kinds of standard coals are experimentally tested. Theoretical and experimental results show that the lower detection limit of the system is better than 0.014%, and the repeatability of the measurement system fairly meets the national standard of China. The system has advantages of low maintenance and shorter measurement duration (4 min).

Song, Feihu; Xu, Chuanlong; Wang, Shimin

2012-02-01

362

Development of a cavity ringdown laser absorption spectrometer for detection of trace levels of mercury.  

PubMed

A potential new laser-based air pollution measurement technique, capable of measuring ultralow concentrations of urban air toxins in the field and in real time, is examined. Cavity ringdown laser absorption spectroscopy (CRLAS) holds promise as an air pollution monitor because it is a highly sensitive species detection technique that uses either pulsed or continuous tunable laser sources. The sensitivity results from an extremely long absorption path length and the fact that the quantity measured, the cavity decay time, is unaffected by fluctuations in the laser source. In laboratory experiments, we reach detection limits for mercury of the order of 0.50 parts per trillion. We developed a CRLAS system in our laboratory and measured Hg with the system, investigating issues such as background interference. We report experimental results for mercury detection limits, the dynamic range of the sensor, detection of Hg in an absorbing background of ozone and SO(2), and detection of a mercury-containing compound (HgCl(2) in this case). PMID:18345163

Spuler, S; Linne, M; Sappey, A; Snyder, S

2000-05-20

363

Diffusion Path Theorems for Ternary Diffusion Couples  

NASA Astrophysics Data System (ADS)

A review is given of 17 theorems concerning diffusion paths in ternary diffusion couples published by Kirkaldy and Brown in 1963. An additional 11 theorems are given herein that were taken from work published on diffusion paths after that time. The new theorems are concerned primarily with diffusion paths that result from crossing multiple-phase regions in an interdiffusion zone. The theorems describe a method for classifying microstructural boundaries between the regions and a catalog of diffusion path features that are unique to each type of boundary. In addition, a proposal is given for how to plot diffusion paths in quaternary and higher order systems.

Morral, John E.

2012-10-01

364

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

365

Attention trees and semantic paths  

NASA Astrophysics Data System (ADS)

In the last few decades several techniques for image content extraction, often based on segmentation, have been proposed. It has been suggested that under the assumption of very general image content, segmentation becomes unstable and classification becomes unreliable. According to recent psychological theories, certain image regions attract the attention of human observers more than others and, generally, the image main meaning appears concentrated in those regions. Initially, regions attracting our attention are perceived as a whole and hypotheses on their content are formulated; successively the components of those regions are carefully analyzed and a more precise interpretation is reached. It is interesting to observe that an image decomposition process performed according to these psychological visual attention theories might present advantages with respect to a traditional segmentation approach. In this paper we propose an automatic procedure generating image decomposition based on the detection of visual attention regions. A new clustering algorithm taking advantage of the Delaunay- Voronoi diagrams for achieving the decomposition target is proposed. By applying that algorithm recursively, starting from the whole image, a transformation of the image into a tree of related meaningful regions is obtained (Attention Tree). Successively, a semantic interpretation of the leaf nodes is carried out by using a structure of Neural Networks (Neural Tree) assisted by a knowledge base (Ontology Net). Starting from leaf nodes, paths toward the root node across the Attention Tree are attempted. The task of the path consists in relating the semantics of each child-parent node pair and, consequently, in merging the corresponding image regions. The relationship detected in this way between two tree nodes generates, as a result, the extension of the interpreted image area through each step of the path. The construction of several Attention Trees has been performed and partial results will be shown.

Giusti, Christian; Pieroni, Goffredo G.; Pieroni, Laura

2007-03-01

366

Evaluation of guidewire path reproducibility  

PubMed Central

The number of minimally invasive vascular interventions is increasing. In these interventions, a variety of devices are directed to and placed at the site of intervention. The device used in almost all of these interventions is the guidewire, acting as a monorail for all devices which are delivered to the intervention site. However, even with the guidewire in place, clinicians still experience difficulties during the interventions. As a first step toward understanding these difficulties and facilitating guidewire and device guidance, we have investigated the reproducibility of the final paths of the guidewire in vessel phantom models on different factors: user, materials and geometry. Three vessel phantoms (vessel diameters ?4 mm) were constructed having tortuousity similar to the internal carotid artery from silicon tubing and encased in Sylgard elastomer. Several trained users repeatedly passed two guidewires of different flexibility through the phantoms under pulsatile flow conditions. After the guidewire had been placed, rotational c-arm image sequences were acquired (9 in. II mode, 0.185 mm pixel size), and the phantom and guidewire were reconstructed (5123, 0.288 mm voxel size). The reconstructed volumes were aligned. The centerlines of the guidewire and the phantom vessel were then determined using region-growing techniques. Guidewire paths appear similar across users but not across materials. The average root mean square difference of the repeated placement was 0.17±0.02 mm (plastic-coated guidewire), 0.73±0.55 mm (steel guidewire) and 1.15±0.65 mm (steel versus plastic-coated). For a given guidewire, these results indicate that the guidewire path is relatively reproducible in shape and position.

Schafer, Sebastian; Hoffmann, Kenneth R.; Noel, Peter B.; Ionita, Ciprian N.; Dmochowski, Jacek

2008-01-01

367

Evaluation of guidewire path reproducibility.  

PubMed

The number of minimally invasive vascular interventions is increasing. In these interventions, a variety of devices are directed to and placed at the site of intervention. The device used in almost all of these interventions is the guidewire, acting as a monorail for all devices which are delivered to the intervention site. However, even with the guidewire in place, clinicians still experience difficulties during the interventions. As a first step toward understanding these difficulties and facilitating guidewire and device guidance, we have investigated the reproducibility of the final paths of the guidewire in vessel phantom models on different factors: user, materials and geometry. Three vessel phantoms (vessel diameters approximately 4 mm) were constructed having tortuousity similar to the internal carotid artery from silicon tubing and encased in Sylgard elastomer. Several trained users repeatedly passed two guidewires of different flexibility through the phantoms under pulsatile flow conditions. After the guidewire had been placed, rotational c-arm image sequences were acquired (9 in. II mode, 0.185 mm pixel size), and the phantom and guidewire were reconstructed (512(3), 0.288 mm voxel size). The reconstructed volumes were aligned. The centerlines of the guidewire and the phantom vessel were then determined using region-growing techniques. Guidewire paths appear similar across users but not across materials. The average root mean square difference of the repeated placement was 0.17 +/- 0.02 mm (plastic-coated guidewire), 0.73 +/- 0.55 mm (steel guidewire) and 1.15 +/- 0.65 mm (steel versus plastic-coated). For a given guidewire, these results indicate that the guidewire path is relatively reproducible in shape and position. PMID:18561663

Schafer, Sebastian; Hoffmann, Kenneth R; Noël, Peter B; Ionita, Ciprian N; Dmochowski, Jacek

2008-05-01

368

[Botulinum toxin: the misguided path].  

PubMed

Botulinum toxin is widely used and has become a popular mass phenomenon in aesthetic medicine. Considerable scientific data concerning the biopsychosocial impact of botulinum toxin use have become available. The bidirectional interaction of mimic and emotion, described as the facial feedback hypothesis, is particularly influenced, as is mimicry. Furthermore, botulinum toxin can cause dysfunction of face harmony including false laughing or the "frozen face". As a result, complex psychosocial disturbances can occur and may affect social interaction and cause flattening of affect. Thus one must ask whether in the future botulinum toxin will continue to be employed in aesthetic dermatology or perhaps be regarded as a misguided path. PMID:23636411

Harth, W

2013-06-01

369

Persistence length in polyelectrolyte systems  

NASA Astrophysics Data System (ADS)

Conformation of flexible polyelectrolytes in solution is considered theoretically. The first point is that these polymers cannot be characterized by one persistence length. The persistence length is scale-dependent (starting from ''bare'' persistence length at smallest length scales and up to the Odijk value at scales larger than the Debye radius). Another point is that the chains in real experimental situations (and in simulations) cannot be considered as infinite; also excluded volume interactions (originating from short-scale part of Coulomb repulsion potential) can neither be neglected. These two effects leads to strong deviations from Odijk predictions causing a decrease of the apparent exponent for the dependence of persistence length on ionic strength. We also demonstrate that the apparent exponent obtained with Khokhlov-Khachaturian (1982) and Li-Witten (1995) approaches is about or below 1 for realistic chain lengths.

Semenov, Alexander; Nyrkova, Irina

1998-03-01

370

Path integration: effect of curved path complexity and sensory system on blindfolded walking.  

PubMed

Path integration refers to the ability to integrate continuous information of the direction and distance traveled 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 traveled. 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

2012-07-27

371

Information Flow in Interaction Networks II: Channels, Path Lengths, and Potentials  

PubMed Central

Abstract In our previous publication, a framework for information flow in interaction networks based on random walks with damping was formulated with two fundamental modes: emitting and absorbing. While many other network analysis methods based on random walks or equivalent notions have been developed before and after our earlier work, one can show that they can all be mapped to one of the two modes. In addition to these two fundamental modes, a major strength of our earlier formalism was its accommodation of context-specific directed information flow that yielded plausible and meaningful biological interpretation of protein functions and pathways. However, the directed flow from origins to destinations was induced via a potential function that was heuristic. Here, with a theoretically sound approach called the channel mode, we extend our earlier work for directed information flow. This is achieved by constructing a potential function facilitating a purely probabilistic interpretation of the channel mode. For each network node, the channel mode combines the solutions of emitting and absorbing modes in the same context, producing what we call a channel tensor. The entries of the channel tensor at each node can be interpreted as the amount of flow passing through that node from an origin to a destination. Similarly to our earlier model, the channel mode encompasses damping as a free parameter that controls the locality of information flow. Through examples involving the yeast pheromone response pathway, we illustrate the versatility and stability of our new framework.

Stojmirovic, Aleksandar

2012-01-01

372

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2012 CFR

...BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical...distance between end points of a fixed link must equal or exceed the value set forth in the table...the Table in § 74.636 of this part. A =...

2012-10-01

373

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2011 CFR

...BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical...distance between end points of a fixed link must equal or exceed the value set forth in the table...the Table in § 74.636 of this part. A =...

2011-10-01

374

Mean free-path length theory of predator–prey interactions: Application to juvenile salmon migration  

Microsoft Academic Search

Ecological theory traditionally describes predator–prey interactions in terms of a law of mass action in which the prey mortality rate depends on the density of predators and prey. This simplifying assumption makes population-based models more tractable but ignores potentially important behaviors that characterize predator–prey dynamics. Here, we expand traditional predator–prey models by incorporating directed and random movements of both predators

James J. Anderson; Eliezer Gurarie; Richard W. Zabel

2005-01-01

375

Students' Development of Length Concepts in a Logo-Based Unit on Geometric Paths.  

ERIC Educational Resources Information Center

Describes a study of third-grade students (N=38) that investigates the development of linear measurement concepts. Three levels of strategies were identified: visual guessing, hash marks, and no physical partitioning. Students who connected numeric and spatial representations proved to be the better problem solvers. Contains 22 reference. (DDR)

Clements, Douglas H.; And Others

1997-01-01

376

Comments on Electrostatic Persistence Length  

NASA Astrophysics Data System (ADS)

I have shown that the quadratic dependence of the electrostatic persistence length on the Debye screening length obtained in the classical Odijk-Skolnick-Fixman (OSF) theory is a result of incorrect assumption made about the energetic penalty for chain deformation. By including chain elasticity the linear dependence of the electrostatic persistence length on the Debye screening length is obtained. This result is derived by applying simple scaling analysis of the angle fluctuations and Gaussian variational principle to the system of strongly and weakly charged polymer chains.

Dobrynin, Andrey

2005-03-01

377

Smart random walkers: the cost of knowing the path.  

PubMed

In this work we study the problem of targeting signals in networks using entropy information measurements to quantify the cost of targeting. We introduce a penalization rule that imposes a restriction on the long paths and therefore focuses the signal to the target. By this scheme we go continuously from fully random walkers to walkers biased to the target. We found that the optimal degree of penalization is mainly determined by the topology of the network. By analyzing several examples, we have found that a small amount of penalization reduces considerably the typical walk length, and from this we conclude that a network can be efficiently navigated with restricted information. PMID:23005381

Perotti, Juan I; Billoni, Orlando V

2012-07-19

378

Vowel-related tongue movements in speech: Straight or curved paths? (L)  

PubMed Central

This paper examines tongue movements between the two vowels in sequences of vowel-labial consonant-vowel, addressing the question whether the movement is a straight line or a curved path. Native speakers of Japanese and Italian served as subjects. The linguistic material consisted of words where the bilabial consonant was either long or short. The inclusion of words with different consonant lengths was motivated by earlier findings that the tongue movement is often longer when the consonant is long, which may be due to a more curved movement path. Tongue movements were recorded using a three-transmitter magnetometer system. To assess the movement path, the movement magnitude was calculated in two ways, as a straight line, the Euclidean distance, and as the actual path, obtained by summing the individual Euclidean distances between successive samples from movement onset to offset. The ratio between the path and the Euclidean distance is 1 when the movement is a straight line and greater than 1 when the path is curved. Results show that in virtually all 21 cases examined the ratio was very close to 1 and in most cases 1.2 or less. There was no reliable influence of consonant length on the ratio.

Lofqvist, Anders

2011-01-01

379

Economic analysis of industrial absorption heat pumps  

SciTech Connect

Absorption heat pumps are a viable technology for waste heat recovery in industry. Yet, no US applications exist to date. In sharp contrast, large scale heat pumps are used in Japan, and a few recent installations have been reported in Europe. This paper presents a description of the existing technologies and applications. A comparative economic analysis of an actual application is carried out for Japan and US conditions. From this analysis, criteria and paths are identified for future technology developments that could make widespread use of these heat pumps economically attractive in the US.

Perez-Blanco, H.; Kaplan, S.I.; Huntley, W.R.

1985-01-01

380

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

381

Variability of calcium absorption  

SciTech Connect

Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately 250 mg. Individual fractional absorption values were normalized to permit pooling of the data. The coefficient of variation (CVs) for absorption for the three groups ranged from 10.57 to 12.79% with the size of the CV increasing with interstudy duration. One other published study presenting replicate absorption values was analyzed in a similar fashion and was found to have a CV of absorption of 9.78%. From these data we estimate that when the standard double-isotope method is used to measure Ca absorption there is approximately 10% variability around any given absorption value within an individual human subject and that roughly two-thirds of this represents real biological variability in absorption.

Heaney, R.P.; Recker, R.R.; Hinders, S.M.

1988-02-01

382

Predicting psychiatric length of stay  

Microsoft Academic Search

This study sought to determine to what extent a multivariate model could predict psychiatric inpatient length of stay. Data were collected from psychiatric service discharges at the Jewish Hospital of Cincinnati during 10 months in 1992 and 1993. Descriptive and multivariate analysis were completed using twelve variables to predict length of stay. The results of this investigation indicated a statistically

Holly S. Bezold; Martin MacDowell; Robert Kunkel

1996-01-01

383

Modeling Protein Conformations: Wiegel's Helical Polymers and the Hida-Streit White Noise Path Integral  

NASA Astrophysics Data System (ADS)

A stochastic model for biopolymers is discussed from a path integral approach to the solution of the Fokker-Planck equation. Explicit expressions for winding conformation probabilities are derived. The model incorporates experimentally observed features such as chirality, Brownian motion, the helix-turn-helix motif abundant in polypeptides, and over-winding of biopolymers when stretched up to a critical length.

Bernido, Christopher C.; Carpio-Bernido, M. Victoria; Escobido, Matthew George O.

2008-06-01

384

Screened Nonbonded Interactions in Native Proteins Manipulate Optimal Paths for Robust Residue Communication  

Microsoft Academic Search

A protein structure is represented as a network of residues whereby edges are determined by intramolecular contacts. We introduce inhomogeneity into these networks by assigning each edge a weight that is determined by amino acid pair potentials. Two methodologies are utilized to calculate the average path lengths (APLs) between pairs: to minimize i), the maximum weight in the strong APL,

Ali Rana Atilgan; Deniz Turgut; Canan Atilgan

2007-01-01

385

Algorithms of localization and statistics of dislocations on the path of laser beam propagation  

Microsoft Academic Search

Three algorithms of dislocation localization in the wave front of a laser beam propagating in a turbulent medium are considered in the report. The precision of algorithms is assessed and statistics of dislocations is determined in different cross-sections of the path as a function of atmospheric parameters such as Fried length and the outer scale of turbulence. The preliminary results

Lidia N. Lavrinova; Feodor Y. Kanev; Vladimir P. Lukin

2002-01-01

386

A new roadmap approach to automatic path planning for mobile robot navigation  

Microsoft Academic Search

This paper describes a new road map approach to find a collision-free path for an AGV (automatic guided vehicle), taking into account the smoothness, length and available space restrictions. The proposed approach uses a top view image of a room in which there are some obstacles to be avoided. First of all the obstacles in the image are thickened using

J. M. Ibarra-Zannatha; J. H. Sossa-Azuela; H. Gonzalez-Hernandez

1994-01-01

387

A genetic algorithm for shortest path routing problem and the sizing of populations  

Microsoft Academic Search

This paper presents a genetic algorithmic approach to the shortest path (SP) routing problem. Variable-length chromosomes (strings) and their genes (parameters) have been used for encoding the problem. The crossover operation exchanges partial chromosomes (partial routes) at positionally independent crossing sites and the mutation operation maintains the genetic diversity of the population. The proposed algorithm can cure all the infeasible

Chang Wook Ahn; Rudrapatna S. Ramakrishna

2002-01-01

388

Visibility-Graph-Based Shortest-Path Geographic Routing in Sensor Networks  

Microsoft Academic Search

We study the problem of shortest-path geographic routing in a static sensor network. Existing algorithms often make routing decisions based on node information in local neighborhoods. However, it is shown by Kuhn et al. that such a design constraint results in a highly undesirable lower bound for routing performance: if a best route has length c ,t hen in the

Guang Tan; Marin Bertier; Anne-Marie Kermarrec

2009-01-01

389

Path tracking control of a manipulator with passive joints  

Microsoft Academic Search

A method is proposed of path tracking control of a manipulator with passive joints, i.e. having no actuators. A desired path is geometrically specified in operational space. The position of the manipulator is controlled to follow the desired path. In this method, a path coordinate system based on the desired path is defined in operational space. The path coordinates consist

Hirohiko ARAI; Kazuo TANIE; Susumu TACHI

1991-01-01

390

OSL—optimal single-loop guide paths for AGVS  

Microsoft Academic Search

This study deals with the Automated Guided Vehicle System guide path design problem. We suggest a single closed loop guide path layout configuration as an alternative to conventional but more complex guide path designs. The benefits of using a simple guide path versus more complicated guide paths are discussed. A procedure for designing an optimal single loop guide path for

J. M. A. TANCHOCOf; DAVID SINRIECH

1992-01-01

391

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

PubMed Central

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

Seidl, Tobias; Wehner, Rudiger

2008-01-01

392

Neural basis of the cognitive map: Path integration does not require hippocampus or entorhinal cortex  

PubMed Central

The hippocampus and entorhinal cortex have been linked to both memory functions and to spatial cognition, but it has been unclear how these ideas relate to each other. An important part of spatial cognition is the ability to keep track of a reference location using self-motion cues (sometimes referred to as path integration), and it has been suggested that the hippocampus or entorhinal cortex is essential for this ability. Patients with hippocampal lesions or larger lesions that also included entorhinal cortex were led on paths while blindfolded (up to 15 m in length) and were asked to actively maintain the path in mind. Patients pointed to and estimated their distance from the start location as accurately as controls. A rotation condition confirmed that performance was based on self-motion cues. When demands on long-term memory were increased, patients were impaired. Thus, in humans, the hippocampus and entorhinal cortex are not essential for path integration.

Shrager, Yael; Kirwan, C. Brock; Squire, Larry R.

2008-01-01

393

A comparison of experimental and theoretical values of atmospheric absorption at the longer millimeter wavelengths  

NASA Astrophysics Data System (ADS)

Results of atmospheric absorption measurements made over very long slant paths at frequencies of 15 and 35 GHz are reported. The absorption was determined from a set of measurements using the sun as a source. A total of 58 sets of data were collected at sunrise and sunset during clear sky conditions for a set of elevation angles from near the horizon to 20 deg. The surface absorption coefficient, zenith absorption, and effective height of the absorbing atmosphere were derived from these data. Regressions of both surface absorption coefficient and zenith absorption were performed as a function of surface absolute humidity; the results were compared with theoretical values obtained by several investigators. Zenith absorptions were found to be in good agreement with theory. However, experimental surface absorption coefficients were consistently lower than the calculated values.

Altshuler, Edward E.; Marr, Richard A.

1988-10-01

394

Integrated assignment and path planning  

NASA Astrophysics Data System (ADS)

A surge of interest in unmanned systems has exposed many new and challenging research problems across many fields of engineering and mathematics. These systems have the potential of transforming our society by replacing dangerous and dirty jobs with networks of moving machines. This vision is fundamentally separate from the modern view of robotics in that sophisticated behavior is realizable not by increasing individual vehicle complexity, but instead through collaborative teaming that relies on collective perception, abstraction, decision making, and manipulation. Obvious examples where collective robotics will make an impact include planetary exploration, space structure assembly, remote and undersea mining, hazardous material handling and clean-up, and search and rescue. Nonetheless, the phenomenon driving this technology trend is the increasing reliance of the US military on unmanned vehicles, specifically, aircraft. Only a few years ago, following years of resistance to the use of unmanned systems, the military and civilian leadership in the United States reversed itself and have recently demonstrated surprisingly broad acceptance of increasingly pervasive use of unmanned platforms in defense surveillance, and even attack. However, as rapidly as unmanned systems have gained acceptance, the defense research community has discovered the technical pitfalls that lie ahead, especially for operating collective groups of unmanned platforms. A great deal of talent and energy has been devoted to solving these technical problems, which tend to fall into two categories: resource allocation of vehicles to objectives, and path planning of vehicle trajectories. An extensive amount of research has been conducted in each direction, yet, surprisingly, very little work has considered the integrated problem of assignment and path planning. This dissertation presents a framework for studying integrated assignment and path planning and then moves on to suggest an exact mathematical model and solution techniques. The approach adopted is based upon the very flexible New Product Development model but also blends many features from other approaches. Solution methods using branch and bound and construction heuristics are developed and tested on several example problems, including a military scenario featuring unmanned air vehicles.

Murphey, Robert A.

395

Calcium absorption and achlorhydria  

Microsoft Academic Search

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

Robert R. Recker

1985-01-01

396

Sequential path entanglement for quantum metrology.  

PubMed

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. PMID:23648653

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

2013-01-01

397

Sequential Path Entanglement for Quantum Metrology  

NASA Astrophysics Data System (ADS)

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.

2013-05-01

398

Quantifying Kinetic Paths of Protein Folding  

PubMed Central

We propose a new approach to activated protein folding dynamics via a diffusive path integral framework. The important issues of kinetic paths in this situation can be directly addressed. This leads to the identification of the kinetic paths of the activated folding process, and provides a direct tool and language for the theoretical and experimental community to understand the problem better. The kinetic paths giving the dominant contributions to the long-time folding activation dynamics can be quantitatively determined. These are shown to be the instanton paths. The contributions of these instanton paths to the kinetics lead to the “bell-like” shape folding rate dependence on temperature, which is in good agreement with folding kinetic experiments and simulations. The connections to other approaches as well as the experiments of the protein folding kinetics are discussed.

Wang, Jin; Zhang, Kun; Lu, Hongyang; Wang, Erkang

2005-01-01

399

Semiclassical series from path integrals  

SciTech Connect

We derive the semiclassical series for the partition function in Quantum Statistical Mechanics (QSM) from its path integral representation. Each term of the series is obtained explicitly from the (real) minima of the classical action. The method yields a simple derivation of the exact result for the harmonic oscillator, and an accurate estimate of ground-state energy and specific heat for a single-well quartic anharmonic oscillator. As QSM can be regarded as finite temperature field theory at a point, we make use of the field-theoretic language of Feynman diagrams to illustrate the non-perturbative character of the series: it contains all powers of ({Dirac_h}/2{pi}) and graphs with any number of loops; the usual perturbative series corresponds to a subset of the diagrams of the semiclassical series. We comment on the application of our results to other potentials, to correlation functions and to field theories in higher dimensions.

Carvalho, C. A. A. de; Cavalcanti, R. M. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Cx. Postal 68528, CEP 21945-970, Rio de Janeiro, RJ (Brazil); Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030 (United States)

1999-07-13

400

The path to adaptive microsystems  

NASA Astrophysics Data System (ADS)

Scaling trends in microsystems are discussed frequently in the technical community, providing a short-term perspective on the future of integrated microsystems. This paper looks beyond the leading edge of technological development, focusing on new microsystem design paradigms that move far beyond today's systems based on static components. We introduce the concept of Adaptive Microsystems and outline a path to realizing these systems-on-a-chip. The role of DARPA in advancing future components and systems research is discussed, and specific DARPA efforts enabling and producing adaptive microsystems are presented. In particular, we discuss efforts underway in the DARPA Microsystems Technology Office (MTO) including programs in novel circuit architectures (3DIC), adaptive imaging and sensing (AFPA, VISA, MONTAGE, A-to-I) and reconfigurable RF/Microwave devices (SMART, TFAST, IRFFE).

Zolper, John C.; Biercuk, Michael J.

2006-06-01

401

Slant path atmospheric extinction measurements  

NASA Astrophysics Data System (ADS)

A commercial Fourier transform spectrometer is being used to collect 0.06/cm 2-14-micron slant path atmospheric spectra using the sun as the source of radiation. Using a Lambert plot approach, 10-15 spectra are collected at different air masses. The logarithm of the intensity versus air mass is used to calculate the extinctance for the atmosphere at arbitrary frequencies within the bandwidth. Over the past three years, spectra have been collected on over 120 days at White Sands Missile Range, NM. Up to a factor of ten variation in the atmospheric extinction is observed at many CO2 laser frequencies which correlate with atmospheric water vapor measurements. Variations in the atmospheric extinction for DF frequencies are smaller and do not correlate with the water vapor measurements.

Gutman, W. M.; Hanley, S. T.; Walters, D. L.

1981-01-01

402

ANALYSIS OF CROSSING PATH CRASH COUNTERMEASURE SYSTEMS  

Microsoft Academic Search

This paper summarizes the results of an analysis of promising countermeasure systems for crossing path crashes, and thus provides a foundation for setting research priorities under the United States (U.S.) Department of Transportation's Intelligent Vehicle Initiative. Crossing path crashes involve one moving vehicle cutting across the path of another, which amounted to 1.72 million police-reported crashes in the U.S. based

Wassim G. Najm; Jonathan A. Koopmann; David L. Smith

403

Optimizing Regular Path Expressions Using Graph Schemas  

Microsoft Academic Search

Several languages, such as LOREL and UnQL, support querying of semi-structured data. Others, such as WebSQL and WebLog, query Web sites. All these languages model data as labeled graphs and use regular path expressions to express queries that traverse arbitrary paths in graphs. Naive execution of path expressions is inefficient, however, because it often requires exhaustive graph search. We describe

Mary F. Fernandez; Dan Suciu

1998-01-01

404

Efficient computation of geodesic shortest paths  

Microsoft Academic Search

This paper describes an ecient algorithm for the geodesic shortest path problem, i.e. the problemof nding shortest paths between pairs of points on the surface of a 3-dimensional polyhedron suchthat the path is constrained to lie on the surface of the polyhedron. We use the wavefront methodand show an O(nlog2n) time bound for this problem, when there are O(n) vertices

Sanjiv Kapoor; Hauz Khan

1999-01-01

405

Path planning for a mobile robot  

Microsoft Academic Search

Two problems for path planning of a mobile robot are considered. The first problem is to find a shortest-time, collision-free path for the robot in the presence of stationary obstacles in two dimensions. The second problem is to determine a collision-free path (greedy in time) for a mobile robot in an environment of moving obstacles. The environment is modeled in

Christos Alexopoulos; Paul M. Griffin

1992-01-01

406

Maximum Flux Transition Paths of Conformational Change.  

PubMed

Given two metastable states A and B of a biomolecular system, the problem is to calculate the likely paths of the transition from A to B. Such a calculation is more informative and more manageable if done for a reduced set of collective variables chosen so that paths cluster in collective variable space. The computational task becomes that of computing the "center" of such a cluster. A good way to define the center employs the concept of a committor, whose value at a point in collective variable space is the probability that a trajectory at that point will reach B before A. The committor "foliates" the transition region into a set of isocommittors. The maximum flux transition path is defined as a path that crosses each isocommittor at a point which (locally) has the highest crossing rate of distinct reactive trajectories. This path is based on the same principle as the minimum resistance path of Berkowitz et al (1983), but it has two advantages: (i) the path is invariant with respect to a change of coordinates in collective variable space and (ii) the differential equations that define the path are simpler. It is argued that such a path is nearer to an ideal path than others that have been proposed with the possible exception of the finite-temperature string method path. To make the calculation tractable, three approximations are introduced, yielding a path that is the solution of a nonsingular two-point boundary-value problem. For such a problem, one can construct a simple and robust algorithm. One such algorithm and its performance is discussed. PMID:20890401

Zhao, Ruijun; Shen, Juanfang; Skeel, Robert D

2010-08-10

407

Applications of Visible Light Path Laser Projector  

Microsoft Academic Search

We proposed and developed a method to visualize the light path of a laser with jetting mists along light axis of a laser pointer.\\u000a The estimation accuracy for the position of a laser spot occluded behind an object was improved when the light path of the\\u000a laser was visualized. In this paper, we propose visible light path laser projector (VLLP)

Nobuchika Sakata; Shu Okamoto; Shogo Nishida

2009-01-01

408

Randomized path coloring on binary trees  

Microsoft Academic Search

Motivated by the problem of WDM routing in all-optical networks, we study the following NP-hard problem. We are given a di- rected binary tree T and a set R of directed paths on T.W e wish to assign colors to paths in R, in such a way that no two paths that share ad irected arc ofT are assigned the

Vincenzo Auletta; Ioannis Caragiannis; Christos Kaklamanis; Pino Persiano

2000-01-01

409

Collisionless absorption in sharp-edged plasmas  

SciTech Connect

The absorption of subpicosecond, obliquely incident laser light is studied using a 11/2D particle-in-cell code. Density scale lengths from {ital L}/{lambda}=0.01 to 2 and laser irradiances between {ital I}{lambda}{sup 2}=10{sup 14} and 10{sup 18} W cm{sup {minus}2} {mu}m{sup 2} are considered. Vacuum heating'' (F. Brunel, Phys. Rev. Lett. 59, 52 (1987)) dominates over resonance absorption for scale lengths {ital L}/{lambda}{lt}0.1, and is most efficient when {ital v}{sub osc}/{ital c}{congruent}3.1({ital L}/{lambda}){sup 2}. Absorbed energy is carried mainly by a superhot'' electron population with {ital U}{sub hot}{similar to}({ital I}{lambda}{sup 2}){sup 1/3--1/2}.

Gibbon, P. (Max-Planck-Institut fuer Biophysikalische Chemie, D-3400 Goettingen-Nikolausberg (Germany)); Bell, A.R. (The Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ (United Kingdom))

1992-03-09

410

Path instability of a rising bubble.  

PubMed

We model the problem of path instability of a rising bubble by considering the bubble as a spheroidal body of fixed shape, and we solve numerically the coupled fluid-body problem. Numerical results show that this model exhibits path instability for large enough values of the control parameters. The corresponding characteristics of the zigzag and spiral paths are in good agreement with experimental observations. Analysis of the vorticity field behind the bubble reveals that a wake instability leading to a double threaded wake is the primary cause of the path instability. PMID:11800955

Mougin, Guillaume; Magnaudet, Jacques

2001-12-19

411

Differences in Path Instabilities Between a Bubble Rising in Water and in Aqueous Polymer Solution in a Hele-Shaw Cell in the Transient and Steady States  

Microsoft Academic Search

The buoyancy-driven path instabilities of an air bubble rising in a Hele-Shaw cell filled with pure water are examined as a function of the Eötvös number (Eo) in terms of changes in the shape, trajectory, and peripheral length (L) of the bubble in the transient and steady states. The path instabilities in an aqueous solution of hydroxypropyl methyl cellulose (HPMC)

Midori Yamamoto; Masami Kawaguchi

2011-01-01

412

Length Distributions in Loop Soups  

NASA Astrophysics Data System (ADS)

Statistical lattice ensembles of loops in three or more dimensions typically have phases in which the longest loops fill a finite fraction of the system. In such phases it is natural to ask about the distribution of loop lengths. We show how to calculate moments of these distributions using CPn-1 or RPn-1 and O(n) ? models together with replica techniques. The resulting joint length distribution for macroscopic loops is Poisson-Dirichlet with a parameter ? fixed by the loop fugacity and by symmetries of the ensemble. We also discuss features of the length distribution for shorter loops, and use numerical simulations to test and illustrate our conclusions.

Nahum, Adam; Chalker, J. T.; Serna, P.; Ortuño, M.; Somoza, A. M.

2013-09-01

413

Solar absorption surface panel  

DOEpatents

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

Santala, Teuvo J. (Attleboro, MA)

1978-01-01

414

Pathways of Iron Absorption  

Microsoft Academic Search

ABSTRACTIron is vital for all living organisms but excess iron can be lethal because it facilitates free radical formation. Thus iron absorption is carefully regulated to maintain an equilibrium between absorption and body loss of iron. In countries where meat is a significant part of the diet, most body iron is derived from dietary heme because heme binds few of

Marcel E. Conrad; Jay N. Umbreit

2002-01-01

415

PHOSPHATE ABSORPTION IN EELGRASS  

Microsoft Academic Search

The absorption of phosphate by eelgrass (Zostera marina L. ) was studied using 32P in a partitioned container where leaves were separated from roots and rhizomes. Absorption, which was greatest in the light, occurred through both leaves and roots, and the absorbed phosphorus was transported rapidly to all parts of the plant. It therefore appears that eelgrass can use phosphate

C. Peter McRoy; Robert J. Barsdate

416

Lymphatic Absorption of Drugs.  

National Technical Information Service (NTIS)

A survey of the role of the lymphatics in absorption from the gut indicates that these vessels may serve as an accessory route for direct absorption from the gut of some drugs but not others. Lymph was collected from the abdominal portion of the left thor...

R. R. Levine

1966-01-01

417

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

418

On Indexation and Contract Length.  

National Technical Information Service (NTIS)

This paper investigates the effects of wage indexation on macroeconomic fluctuations in a model which highlights the joint determination of two contract characteristics: contract length and an indexing parameter. Within the framework developed by this ana...

J. A. Gray

1976-01-01

419

Full Length Donor History Questionnaire  

Center for Biologics Evaluation and Research (CBER)

Text VersionPage 1. This document is one component of the donor history questionnaire documents (Version No. ... Full-Length Donor History Questionnaire ... More results from www.fda.gov/downloads/biologicsbloodvaccines/bloodbloodproducts

420

Spectral dynamics of intracavity absorption in a pulsed Cr{sup 2+}:ZnSe laser  

SciTech Connect

The growth dynamics of intracavity absorption is studied during recording line absorption spectra by the method of intracavity laser spectroscopy using a pulsed Cr{sup 2+}:ZnSe laser tunable between 2.1 and 3.1 {mu}m. In the lasing duration range from 0 to 235 {mu}s, an intracavity absorption signal increases linearly with time, providing the effective absorption length of 70km. (laser spectroscopy)

Akimov, V A [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation); Kozlovskii, Vladimir I; Korostelin, Yurii V; Landman, Aleksandr I; Podmar'kov, Yu P; Frolov, M P [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2005-05-31

421

Texture of locomotor path: a replicable characterization of a complex behavioral phenotype.  

PubMed

A database of mouse locomotor path in spatial tests can be used to search in silico for behavioral measures that better discriminate between genotypes and are more replicable across laboratories. In this study, software for the exploration of exploration (SEE) was used to search a large database for a novel behavioral measure that would characterize complex movement paths. The database included mouse open-field behavior assessed in 3 laboratories, 7 inbred strains, several pharmacological treatments and hundreds of animals. The new behavioral measure, "path texture", was characterized using the local curvature of the path (the change of direction per unit distance, in degrees/cm) across several spatial scales, starting from scales smaller than the animal's body length and up to the scale of the arena size. Path texture analysis differs from fractal dimension analysis in that it does not assume self-similarity across scales. Path texture was found to discriminate inbred strains with relatively high broad-sense heritability (43%-71%) and high replicability across laboratories. Even genotypes that had similar path curvatures in some scales usually differed in other scales, and self-similarity across scales was not displayed by all genotypes. Amphetamine decreased the path curvature of C57BL/6 mice in small and medium scales, while having no effect on DBA/2J mice. Diazepam dose-dependently decreased the curvature of C57BL/6 mice across all scales, while 2 anxiogenic drugs, FG-7142 and pentylenetetrazole, increased it. Path texture thus has high potential for behavioral phenotyping and the study of drug effects in the mouse. PMID:16176389

Kafkafi, N; Elmer, G I

2005-10-01

422

Path planning and path tracking control of unmanned ground vehicles (UGVs)  

Microsoft Academic Search

Unmanned ground vehicles (UGVs) will be playing increasingly important role in the future battlefields. How to automatically guide and control UGVs under varying environment conditions represents a challenging issue. This paper presents a novel approach to achieving path planning and path tracking of UGVs under dynamic environments. We apply the topology theory to find the optimal path given any starting

Liguo Weng; D. Y. Song

2005-01-01

423

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

424

Path-Goal Theory of Leadership.  

National Technical Information Service (NTIS)

The paper reviews the path-goal theory of leadership. This theory states that a leader's behavior is important for good performance as a function of its impact on subordinates' perceptions of paths to goals and the attractiveness of the goals. When leader...

R. J. House T. R. Mitchell

1975-01-01

425

Ray path deviation in a nonhemispherical dome  

Microsoft Academic Search

A calculation is presented for meridional rays of the ray path deviation in a conformal dome in which both the shape of the inner and outer surfaces are specified in detail so as to examine under what conditions the ray path deviation might be minimized by independently adjusting the shape of the inner surface. Specific results are given for the

Richard I. Joseph; Michael E. Thomas

2001-01-01

426

The stable paths problem and interdomain routing  

Microsoft Academic Search

Dynamic routing protocols such as RIP and OSPF essentially implement distributed algorithms for solving the shortest paths problem. The border gateway protocol (BGP) is currently the only interdomain routing protocol deployed in the Internet. BGP does not solve a shortest paths problem since any interdomain protocol is required to allow policy-based metrics to override distance-based metrics and enable autonomous systems

Timothy G. Griffin; F. Bruce Shepherd; Gordon T. Wilfong

2002-01-01

427

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

428

Modeling Robot Path Planning with CD  

Microsoft Academic Search

Robotic systems are usually built as independent a gents that collaborate to accomplish a specific task. Analysis of robot path planning consists of route plan- ning and path generation. We will show how to apply the Cell-DEVS formalism and the CD++ toolkit for these tasks. We present a Cell -DEVS model for route planning, which, based on the obstacles, finds

Gabriel A. Wainer

2006-01-01

429

Hausdorff Dimension of Operator Stable Sample Paths  

Microsoft Academic Search

The Hausdorff dimension of the sample paths of a stochastic process with stationary independent operator stable increments is computed. With probability one, every sample path has the same dimension, depending on the real parts of the eigenvalues of the operator stable exponent.

Peter Becker-Kern; Mark M. Meerschaert; Hans-Peter Scheffler

2003-01-01

430

Bounding the error of path loss models  

Microsoft Academic Search

In this paper we analyze the efficacy of basic path loss models at predicting median path loss in urban environments. We attempt to bound the practical error of these models and look at how they may hinder practical wireless applications, and in particular dynamic spectrum access networks. This analysis is made using a large set of measurements from production networks

Caleb Phillips; Douglas Sicker; Dirk Grunwald

2011-01-01

431

Diversion path analysis handbook. Volume I. Methodology  

Microsoft Academic Search

Diversion Path Analysis (DPA) is a procedure for analyzing internal controls of a facility in order to identify vulnerabilities to successful diversion of material by an adversary. The internal covert threat is addressed but the results are also applicable to the external overt threat. The diversion paths are identified. Complexity parameters include records alteration or falsification, multiple removals of sub-threshold

M. D. K. Maltese; K. E. Goodwin; J. C. Schleter

1976-01-01

432

Judgments of path, not heading, guide locomotion.  

PubMed

To steer a course through the world, people are almost entirely dependent on visual information, of which a key component is optic flow. In many models of locomotion, heading is described as the fundamental control variable; however, it has also been shown that fixating points along or near one's future path could be the basis of an efficient control solution. Here, the authors aim to establish how well observers can pinpoint instantaneous heading and path, by measuring their accuracy when looking at these features while traveling along straight and curved paths. The results showed that observers could identify both heading and path accurately (approximately 3 degrees ) when traveling along straight paths, but on curved paths they were more accurate at identifying a point on their future path (approximately 5 degrees ) than indicating their instantaneous heading (approximately 13 degrees ). Furthermore, whereas participants could track changes in the tightness of their path, they were unable to accurately track the rate of change of heading. In light of these results, the authors suggest it is unlikely that heading is primarily used by the visual system to support active steering. PMID:16478328

Wilkie, Richard M; Wann, John P

2006-02-01

433

Reducing power with dynamic critical path information  

Microsoft Academic Search

Recent research has shown that dynamic information regarding instruction criticality can be used to increase microprocessor performance. Critical path information can also be used in processors to achieve a better balance of power and performance. This paper uses the output of a dynamic critical path predictor to decrease the power consumption of key portions of the processor without incurring a

John S. Seng; Eric S. Tune; Dean M. Tullsen

2001-01-01

434

Analysis of probabilistic roadmaps for path planning  

Microsoft Academic Search

We provide an analysis of a path planning method which uses probabilistic roadmaps. This method has proven very successful in practice, but the theoretical understanding of its performance is still limited. Assuming that a path ? exists between two configurations a and b of the robot, we study the dependence of the failure probability to connect a and b, on:

Lydia E. Kavraki; Mihail N. Kolountzakis; Jean-claude Latombe

1998-01-01

435

Path Planning Algorithms for Agricultural Machines  

Microsoft Academic Search

If the field plot shape is not rectangular and if it contains obstacles, the coverage path planning problem is hard to solve for a non-omnidirectional machine. Scientists have developed several algorithms to solve this coverage path planning problem, but all of them have pros and cons. If the machines were omnidirectional and turning times were decreased to insignificant, the problem

T. Oksanen; A. Visala

2007-01-01

436

Path Integrals in Lattice Quantum Chromodynamics  

NASA Astrophysics Data System (ADS)

I discuss the use of path integrals to study strong-interaction physics from first principles. The underlying theory is cast into path integrals which are evaluated numerically using Monte Carlo methods on a space-time lattice. Examples are given in progress made in nuclear physics.

Lee, F. X.

2008-11-01

437

Fatigue failure paths for offshore platform inspection  

Microsoft Academic Search

A closed- form, reliability-based procedure is developed to identify fatigue failure paths of offshore structures and assess the notional probability of system failure through these paths. The procedure utilizes the Miners rule node fatigue failure reliability model developed by Wirsching. Effects of load redistribution following the fatigue failure of a node on the time to failure of remaining unfailed nodes

Demir I. Karsan; Ashok Kumar

1990-01-01

438

The path dependence of deformation texture development  

SciTech Connect

It is demonstrated for the case of three different strain paths, all of which end up with the same, elongated specimen shape, that the texture developed during straining is path dependent. This is true both for experiments on aluminum polycrystals and for simulations using the LApp code.

Takeshita, T.; Kocks, U.F.; Wenk, H.R.

1987-01-01

439

Evaluation of Calcine Disposition Path Forward  

SciTech Connect

This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

Birrer, S.A.; Heiser, M.B.

2003-02-26

440

Evaluation of Calcine Disposition - Path Forward  

SciTech Connect

This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

Steve Birrer

2003-02-01

441

White Noise Path Integrals in Stochastic Neurodynamics  

NASA Astrophysics Data System (ADS)

The white noise path integral approach is used in stochastic modeling of neural activity, where the primary dynamical variables are the relative membrane potentials, while information on transmembrane ionic currents is contained in the drift coefficient. The white noise path integral allows a natural framework and can be evaluated explicitly to yield a closed form for the conditional probability density.

Carpio-Bernido, M. Victoria; Bernido, Christopher C.

2008-06-01

442

Absorption lines in quasar pairs  

Microsoft Academic Search

The comparison of the absorption spectra of close pairs of QSOs makes it possible to study directly the sizes and clustering of absorbing regions. Phenomena of interest are related to Common Absorption (absorption in both spectra at the same redshift), and Associated Absorption (absorption at the redshift of the foreground QSO in the spectrum of the other member of the

P. A. Shaver; J. G. Robertson

1983-01-01

443

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

444

Dynamics of dielectric breakdown paths.  

PubMed

We investigate the dynamics and geometry of dielectric breakdown paths of needle defects of arbitrary residual resistivity in an otherwise homogeneous medium using a time-dependent electrical-circuit model. The circuit model consists of a semi-infinite lattice of capacitors in parallel with resistors that break down to a lower (residual) resistance. The breakdown occurs if the local field across a resistor exceeds a critical value for a breakdown delay time. We consider cases where the initial resistance is infinite or finite and where the residual resistance is finite or zero. We consider the model for the case where the applied field reaches the critical value adiabatically. We find that, as in the quasistatic case, the breakdown grows either one dimensionally or spreads with a fractal dimension (bifurcates) depending on the values of residual resistance and breakdown delay time. Also, we find that the propagation velocity of the needle oscillates spontaneously. We give the phase diagram for bifurcation and oscillations. We derive a simplified recursive map approximation to explain this behavior. PMID:16241371

Boksiner, Jeffrey; Leath, P L

2003-06-27

445

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

446

Long-path monitoring of atmospheric carbon monoxide with a tunable diode laser system.  

PubMed

Long-path measurements of carbon monoxide in the atmosphere are described. The technique of resonance absorption was used in which the wavelength of radiation from a PbS(0.82)MbSe(0.18) semiconductor diode laser was tuned into coincidence with an absorption line of CO in its fundamental band around 4.7 microm. By employing rapid frequency modulation of the laser emission to overcome atmospheric turbulence effects, it was possible to achieve a minimum detectable concentration of 5 parts per billion over a 0.61-km path. Continuous around-the-clock monitoring was also performed and permitted increases in the ambient CO level due to commuter traffic to be observed. PMID:20134990

Ku, R T; Hinkley, E D; Sample, J O

1975-04-01

447

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

448

Long path optical extinction and meteorology in the San Francisco Bay Area  

SciTech Connect

Instrumentation and analysis techniques aimed at establishing the relationships between remotely sensed meteorological and visibility parameters of the atmosphere are discussed. It is shown that long and short term visibility and atmospheric extinction trends are dominated by meteorological parameters. A report is made of new instrumentation and preliminary results using these instruments to remotely sense meteorological parameters along the same light path over which light extinction measurements are made. Those atmospheric parameters affecting visibility are water vapor, NO/sub 2/, ozone, aerosol, wind speed and stability or atmospheric temperature profile with height. All of these parameters can be remotely determined for a given light path by a combination of high resolution spectrographic absorption, low resolution wavelength extinction measurements optical scintillation and stellar refraction. Remotely sensed cross-path wind speeds are presently being determined from optical scintillation techniques and remote sensing of atmospheric mixing depths are being investigated using searchlight techniques or stellar refraction inversions. (JGB)

Porch, W.M.; Galloway, T.R.; Green, T.J.; Waidl, J.O.

1980-08-01

449

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

NASA Astrophysics Data System (ADS)

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

Rothermel, J.; Jones, W. D.

1985-11-01

450

Scale Length of Disk Galaxies  

NASA Astrophysics Data System (ADS)

Disk scale length rd and central surface brightness ?0 for a sample of 29955 bright disk galaxies from the Sloan Digital Sky Survey have been analyzed. Cross correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scale lengths for different types of disk/spiral galaxies and present distributions and typical trends of scale lengths all the SDSS bands with linear relations that indicate the relation that connect scale lengths in one passband to another. We use the volume corrected results in the r-band and revisit the relation between these parameters and the galaxy morphology, and find the average values = 3.8 +/- 2.1 kpc and = 20.2 +/- 0.7 mag arcsec-2. The derived scale lengths presented here are representative for a typical galaxy mass of 1010.8 M?, and the RMS dispersion is larger for more massive galaxies. We analyse the rd-?0 plane and further investigate the Freeman Law and confirm that it indeed defines an upper limit for ?0 in bright disks (rmag < 17.0), and that disks in late type spirals (T >= 6) have fainter central surface brightness. Our results are based on a sample of galaxies in the local universe (z < 0.3) that is two orders of magnitudes larger than any sample previously studied, and deliver statistically significant results that provide a comprehensive test bed for future theoretical studies and numerical simulations of galaxy formation and evolution.

Fathi, Kambiz

2011-12-01

451

Do grammars minimize dependency length?  

PubMed

A well-established principle of language is that there is a preference for closely related words to be close together in the sentence. This can be expressed as a preference for dependency length minimization (DLM). In this study, we explore quantitatively the degree to which natural languages reflect DLM. We extract the dependencies from natural language text and reorder the words in such a way as to minimize dependency length. Comparing the original text with these optimal linearizations (and also with random linearizations) reveals the degree to which natural language minimizes dependency length. Tests on English data show that English shows a strong effect of DLM, with dependency length much closer to optimal than to random; the optimal English grammar also has many specific features in common with English. In German, too, dependency length is significantly less than random, but the effect is much weaker than in English. We conclude by speculating about some possible reasons for this difference between English and German. PMID:21564213

Gildea, Daniel; Temperley, David

2009-10-27

452

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

453

Open-path Emission Factors Derived from DOAS and FTIR Measurements in the Mexico City Metropolitan Area  

Microsoft Academic Search

Mobile sources are responsible for about 50% of VOC (volatile organic compounds) and about 70% of NOx emissions in the Mexico City Metropolitan Area (MCMA). A novel approach has been developed to derive emission factors for mobile sources that are representative of the overall vehicle fleet, using collocated open-path Differential Optical Absorption Spectroscopy (DOAS) and Fourier Transform Infrared (FTIR) spectroscopic

E. Flores; M. Grutter; B. Galle; J. Mellqvist; J. Samuelsson; B. Knighton; B. T. Jobson; R. Volkamer; L. T. Molina; M. J. Molina

2004-01-01

454

Comparison of cloud liquid water paths derived from in situ and microwave radiometer data taken during the SHEBA\\/FIREACE  

Microsoft Academic Search

Mean cloud liquid water path LWP derived from microwave measurements using the standard ARM retrieval technique is nearly twice as large as coincident in situ aircraft data taken over the SHEBA ice camp in the Arctic during FIREACE. Using an algorithm adopted from satellite remote sensing that more completely accounts for the temperature dependence of water absorption and atmospheric gas

Bing Lin; Patrick Minnis; Alice Fan; Judith A. Curry; H. Gerber

2001-01-01

455

Emission source strengths of gasoline-filling processes determined by open-path spectroscopic techniques and inverse modeling  

Microsoft Academic Search

Up to now emission source strengths of diffuse and heterogenous emission of important VOCs are not well known especially from gas stations and gasoline tank farms. To estimate the total emission of these sources non-intrusive measurements were performed by a differential optical absorption spectroscopy (DOAS) system to determine the path- integrated concentrations of exhaust compounds downwind of the source through

Klaus Schaefer; Martina Stockhause; Herbert Hoffmann; Achim Sedlmaier; Stefan M. Emeis

1998-01-01

456

Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS)  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

Chartier, R. T.; Greenslade, M. E.

2012-04-01

457

Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass aerosol extinction differential optical absorption spectrometer (AE-DOAS)  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

Chartier, R. T.; Greenslade, M. E.

2011-10-01

458

Axial eye-length measurement by wavelength-shift interferometry.  

PubMed

A simplified noncontact measuring technique for axial eye length was developed. According to this method, the wavelength shift of a single-mode laser-diode beam that is irradiated onto the eyeball causes a phase shift in the interference fringes of reflections from the retina and the cornea. Then the optical distance between the cornea and the retina is obtained from the phase-shift measurement. High-speed axial eye-length measurements can be performed by using a laser diode on a pulse-modulation drive and signals from the reference light path as an analog-to-digital-conversion trigger. Compared with the technique that uses partially coherent light, this technique is inferior in terms of measurement accuracy but superior in its wide, measurable range of 16-32 mm. The results of measurements of 21 adults showed that 2 standard deviations of measurement was 2 sigma = +/- 0.11 mm. PMID:8350154

Sekine, A; Minegishi, I; Koizumi, H

1993-07-01

459

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

460

Screening length in plasma winds  

NASA Astrophysics Data System (ADS)

We study the screening length Ls 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. 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.

Cáceres, Elena; Natsuume, Makoto; Okamura, Takashi

2006-10-01

461

The Evolution of Energy Absorption Systems for Crashworthy Helicopter Seats  

Microsoft Academic Search

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

Stanley P. Desjardins

2006-01-01

462