Exploiting broad-area surface emitting lasers to manifest the path-length distributions of finite-potential quantum billiards.

PubMed

Yu, Y T; Tuan, P H; Chang, K C; Hsieh, Y H; Huang, K F; Chen, Y F

2016-01-11

Broad-area vertical-cavity surface-emitting lasers (VCSELs) with different cavity sizes are experimentally exploited to manifest the influence of the finite confinement strength on the path-length distribution of quantum billiards. The subthreshold emission spectra of VCSELs are measured to obtain the path-length distributions by using the Fourier transform. It is verified that the number of the resonant peaks in the path-length distribution decreases with decreasing the confinement strength. Theoretical analyses for finite-potential quantum billiards are numerically performed to confirm that the mesoscopic phenomena of quantum billiards with finite confinement strength can be analogously revealed by using broad-area VCSELs.

Ballistic Imaging and Scattering Measurements for Diesel Spray Combustion: Optical Development and Phenomenological Studies

DTIC Science & Technology

2016-04-01

polystyrene spheres in a water suspension. The impact of spatial filtering , temporal filtering , and scattering path length on image resolution are...The impact of spatial filtering , temporal filtering , and scattering path length on image resolution are reported. The technique is demonstrated...cell filled with polystyrene spheres in a water suspension. The impact of spatial filtering , temporal filtering , and scattering path length on image

A complete VLBI delay model for deforming radio telescopes: the Effelsberg case

NASA Astrophysics Data System (ADS)

Artz, T.; Springer, A.; Nothnagel, A.

2014-12-01

Deformations of radio telescopes used in geodetic and astrometric very long baseline interferometry (VLBI) observations belong to the class of systematic error sources which require correction in data analysis. In this paper we present a model for all path length variations in the geometrical optics of radio telescopes which are due to gravitational deformation. The Effelsberg 100 m radio telescope of the Max Planck Institute for Radio Astronomy, Bonn, Germany, has been surveyed by various terrestrial methods. Thus, all necessary information that is needed to model the path length variations is available. Additionally, a ray tracing program has been developed which uses as input the parameters of the measured deformations to produce an independent check of the theoretical model. In this program as well as in the theoretical model, the illumination function plays an important role because it serves as the weighting function for the individual path lengths depending on the distance from the optical axis. For the Effelsberg telescope, the biggest contribution to the total path length variations is the bending of the main beam located along the elevation axis which partly carries the weight of the paraboloid at its vertex. The difference in total path length is almost 100 mm when comparing observations at 90 and at 0 elevation angle. The impact of the path length corrections is validated in a global VLBI analysis. The application of the correction model leads to a change in the vertical position of mm. This is more than the maximum path length, but the effect can be explained by the shape of the correction function.

Separated-orbit bisected energy-recovered linear accelerator

DOEpatents

Douglas, David R.

2015-09-01

A separated-orbit bisected energy-recovered linear accelerator apparatus and method. The accelerator includes a first linac, a second linac, and a plurality of arcs of differing path lengths, including a plurality of up arcs, a plurality of downgoing arcs, and a full energy arc providing a path independent of the up arcs and downgoing arcs. The up arcs have a path length that is substantially a multiple of the RF wavelength and the full energy arc includes a path length that is substantially an odd half-integer multiple of the RF wavelength. Operation of the accelerator includes accelerating the beam utilizing the linacs and up arcs until the beam is at full energy, at full energy executing a full recirculation to the second linac using a path length that is substantially an odd half-integer of the RF wavelength, and then decelerating the beam using the linacs and downgoing arcs.

Low-Coherence light source design for ESPI in-plane displacement measurements

NASA Astrophysics Data System (ADS)

Heikkinen, J. J.; Schajer, G. S.

2018-01-01

The ESPI method for surface deformation measurements requires the use of a light source with high coherence length to accommodate the optical path length differences present in the apparatus. Such high-coherence lasers, however, are typically large, delicate and costly. Laser diodes, on the other hand, are compact, mechanically robust and inexpensive, but unfortunately they have short coherence length. The present work aims to enable the use of a laser diode as an illumination source by equalizing the path lengths within an ESPI interferometer. This is done by using a reflection type diffraction grating to compensate for the path length differences. The high optical power efficiency of such diffraction gratings allows the use of much lower optical power than in previous interferometer designs using transmission gratings. The proposed concept was experimentally investigated by doing in-plane ESPI measurements using a high-coherence single longitudinal mode (SLM) laser, a laser diode and then a laser diode with path length optimization. The results demonstrated the limitations of using an uncompensated laser diode. They then showed the effectiveness of adding a reflection type diffraction grating to equalize the interferometer path lengths. This addition enabled the laser diode to produce high measurement quality across the entire field of view, rivaling although not quite equaling the performance of a high-coherence SLM laser source.

Elevation effects in volcano applications of the COSPEC

USGS Publications Warehouse

Gerlach, T.M.

2003-01-01

Volcano applications commonly involve sizeable departures from the reference pressure and temperature of COSPEC calibration cells. Analysis shows that COSPEC SO2 column abundances and derived mass emission rates are independent of pressure and temperature, and thus unaffected by elevation effects related to deviations from calibration cell reference state. However, path-length concentrations are pressure and temperature dependent. Since COSPEC path-length concentration data assume the reference pressure and temperature of calibration cells, they can lead to large errors when used to calculate SO2 mixing ratios of volcanic plumes. Correction factors for COSPEC path-length concentrations become significant (c.10%) at elevations of about 1 km (e.g. Kilauea volcano) and rise rapidly to c.80% at 6 km (e.g. Cotopaxi volcano). Calculating SO2 mixing ratios for volcanic plumes directly from COSPEC path-length concentrations always gives low results. Corrections can substantially increase mixing ratios; for example, corrections increase SO2 ppm concentrations reported for the Mount St Helens, Colima, and Erebus plumes by 25-50%. Several arguments suggest it would be advantageous to calibrate COSPEC measurements in column abundance units rather than path-length concentration units.

Simultaneous water vapor and dry air optical path length measurements and compensation with the large binocular telescope interferometer

NASA Astrophysics Data System (ADS)

Defrère, D.; Hinz, P.; Downey, E.; Böhm, M.; Danchi, W. C.; Durney, O.; Ertel, S.; Hill, J. M.; Hoffmann, W. F.; Mennesson, B.; Millan-Gabet, R.; Montoya, M.; Pott, J.-U.; Skemer, A.; Spalding, E.; Stone, J.; Vaz, A.

2016-08-01

The Large Binocular Telescope Interferometer uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 microns). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI/MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current performance of the system for dry air seeing compensation, we present simultaneous H-, K-, and N-band observations that illustrate the feasibility of our feedforward approach to stabilize the path length fluctuations seen by the LBTI nuller.

The processing of spatial information in short-term memory: insights from eye tracking the path length effect.

PubMed

Guérard, Katherine; Tremblay, Sébastien; Saint-Aubin, Jean

2009-10-01

Serial memory for spatial locations increases as the distance between successive stimuli locations decreases. This effect, known as the path length effect [Parmentier, F. B. R., Elford, G., & Maybery, M. T. (2005). Transitional information in spatial serial memory: Path characteristics affect recall performance. Journal of Experimental Psychology: Learning, Memory & Cognition, 31, 412-427], was investigated in a systematic manner using eye tracking and interference procedures to explore the mechanisms responsible for the processing of spatial information. In Experiment 1, eye movements were monitored during a spatial serial recall task--in which the participants have to remember the location of spatially and temporally separated dots on the screen. In the experimental conditions, eye movements were suppressed by requiring participants to incessantly move their eyes between irrelevant locations. Ocular suppression abolished the path length effect whether eye movements were prevented during item presentation or during a 7s retention interval. In Experiment 2, articulatory suppression was combined with a spatial serial recall task. Although articulatory suppression impaired performance, it did not alter the path length effect. Our results suggest that rehearsal plays a key role in serial memory for spatial information, though the effect of path length seems to involve other processes located at encoding, such as the time spent fixating each location and perceptual organization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 ofmore » 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.« less

Time optimal paths for high speed maneuvering

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1993-01-01

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 ofmore » 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.« less

47 CFR 101.143 - Minimum path length requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the table...

47 CFR 101.143 - Minimum path length requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the table...

47 CFR 101.143 - Minimum path length requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the table...

47 CFR 101.143 - Minimum path length requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the table...

47 CFR 101.143 - Minimum path length requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the table...

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

NASA Astrophysics Data System (ADS)

Bizheva, Kostadinka K.; Siegel, Andy M.; Boas, David A.

1998-12-01

We used low coherence interferometry to measure Brownian motion within highly scattering random media. A coherence gate was applied to resolve the optical path-length distribution and to separate ballistic from diffusive light. Our experimental analysis provides details on the transition from single scattering to light diffusion and its dependence on the system parameters. We found that the transition to the light diffusion regime occurs at shorter path lengths for media with higher scattering anisotropy or for larger numerical aperture of the focusing optics.

Forward- and reverse-bias tunneling effects in n/+/p silicon solar cells

NASA Technical Reports Server (NTRS)

Garlick, G. F. J.; Kachare, A. H.

1980-01-01

Excess currents due to field-assisted tunneling in both forward and reverse bias directions have been observed in n(+)-p silicon solar cells. These currents arise from the effect of conducting paths produced in the depletion layer by n(+) diffusion and cell processing. Forward-bias data indicate a small potential barrier with height of 0.04 eV at the n(+) end of conducting paths. Under reverse bias, excess tunneling currents involve a potential barrier at the p end of the conducting paths, the longer paths being associated with smaller barrier heights and dominating at the lower temperatures. Low-reverse-bias data give energy levels of 0.11 eV for lower temperatures (253-293 K) and 0.35 eV for higher temperatures (293-380 K). A model is suggested to explain the results.

Two-path plasmonic interferometer with integrated detector

DOEpatents

Dyer, Gregory Conrad; Shaner, Eric A.; Aizin, Gregory

2016-03-29

An electrically tunable terahertz two-path plasmonic interferometer with an integrated detection element can down convert a terahertz field to a rectified DC signal. The integrated detector utilizes a resonant plasmonic homodyne mixing mechanism that measures the component of the plasma waves in-phase with an excitation field that functions as the local oscillator in the mixer. The plasmonic interferometer comprises two independently tuned electrical paths. The plasmonic interferometer enables a spectrometer-on-a-chip where the tuning of electrical path length plays an analogous role to that of physical path length in macroscopic Fourier transform interferometers.

The optimum measurement precision evaluation for blood components using near-infrared spectra on 1000-2500 nm

NASA Astrophysics Data System (ADS)

Zhang, Ziyang; Sun, Di; Han, Tongshuai; Guo, Chao; Liu, Jin

2016-10-01

In the non-invasive blood components measurement using near infrared spectroscopy, the useful signals caused by the concentration variation in the interested components, such as glucose, hemoglobin, albumin etc., are relative weak. Then the signals may be greatly disturbed by a lot of noises in various ways. We improved the signals by using the optimum path-length for the used wavelength to get a maximum variation of transmitted light intensity when the concentration of a component varies. And after the path-length optimization for every wavelength in 1000-2500 nm, we present the detection limits for the components, including glucose, hemoglobin and albumin, when measuring them in a tissue phantom. The evaluated detection limits could be the best reachable precision level since it assumed the measurement uses a high signal-to-noise ratio (SNR) signal and the optimum path-length. From the results, available wavelengths in 1000-2500 nm for the three component measurements can be screened by comparing their detection limit values with their measurement limit requirements. For other blood components measurement, the evaluation their detection limits could also be designed using the method proposed in this paper. Moreover, we use an equation to estimate the absorbance at the optimum path-length for every wavelength in 1000-2500 nm caused by the three components. It could be an easy way to realize the evaluation because adjusting the sample cell's size to the precise path-length value for every wavelength is not necessary. This equation could also be referred to other blood components measurement using the optimum path-length for every used wavelength.

Using refraction in thick glass plates for optical path length modulation in low coherence interferometry.

PubMed

Kröger, Niklas; Schlobohm, Jochen; Pösch, Andreas; Reithmeier, Eduard

2017-09-01

In Michelson interferometer setups the standard way to generate different optical path lengths between a measurement arm and a reference arm relies on expensive high precision linear stages such as piezo actuators. We present an alternative approach based on the refraction of light at optical interfaces using a cheap stepper motor with high gearing ratio to control the rotation of a glass plate. The beam path is examined and a relation between angle of rotation and change in optical path length is devised. As verification, an experimental setup is presented, and reconstruction results from a measurement standard are shown. The reconstructed step height from this setup lies within 1.25% of the expected value.

Multi-chord fiber-coupled interferometer with a long coherence length laser

NASA Astrophysics Data System (ADS)

Merritt, Elizabeth C.; Lynn, Alan G.; Gilmore, Mark A.; Hsu, Scott C.

2012-03-01

This paper describes a 561 nm laser heterodyne interferometer that provides time-resolved measurements of line-integrated plasma electron density within the range of 1015-1018 cm-2. Such plasmas are produced by railguns on the plasma liner experiment, which aims to produce μs-, cm-, and Mbar-scale plasmas through the merging of 30 plasma jets in a spherically convergent geometry. A long coherence length, 320 mW laser allows for a strong, sub-fringe phase-shift signal without the need for closely matched probe and reference path lengths. Thus, only one reference path is required for all eight probe paths, and an individual probe chord can be altered without altering the reference or other probe path lengths. Fiber-optic decoupling of the probe chord optics on the vacuum chamber from the rest of the system allows the probe paths to be easily altered to focus on different spatial regions of the plasma. We demonstrate that sub-fringe resolution capability allows the interferometer to operate down to line-integrated densities of the order of 5 × 1015 cm-2.

Mathematical model for path selection by ants between nest and food source.

PubMed

Bodnar, Marek; Okińczyc, Natalia; Vela-Pérez, M

2017-03-01

Several models have been proposed to describe the behavior of ants when moving from nest to food sources. Most of these studies where based on numerical simulations with no mathematical justification. In this paper, we propose a mechanism for the formation of paths of minimal length between two points by a collection of individuals undergoing reinforced random walks taking into account not only the lengths of the paths but also the angles (connected to the preference of ants to move along straight lines). Our model involves reinforcement (pheromone accumulation), persistence (tendency to preferably follow straight directions in absence of any external effect) and takes into account the bifurcation angles of each edge (represented by a probability of willingness of choosing the path with the smallest angle). We describe analytically the results for 2 ants and different path lengths and numerical simulations for several ants. Copyright © 2016 Elsevier Inc. All rights reserved.

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

NASA Astrophysics Data System (ADS)

Everaers, Ralf

2012-08-01

We show that the front factor appearing in the shear modulus of a phantom network, Gph=(1-2/f)(ρkBT)/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=(ρkBT)/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=(ρkBT)/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.

A vector-based representation of the chemical bond for the substituted torsion of biphenyl

NASA Astrophysics Data System (ADS)

Li, Jiahui; Huang, Weijie; Xu, Tianlv; Kirk, Steven R.; Jenkins, Samantha

2018-06-01

We use a new interpretation of the chemical bond within QTAIM, the bond-path framework set B = {p, q, r} with associated linkages with lengths H∗, H and the familiar bond-path length is used to describe a torsion θ, 0.0° ≤ θ < 22.0° of para-substituted biphenyl, C12H9-x, x = N(CH3)2, NH2, CH3, CHO, CN, NO2. We include consideration of the H--H bonding interactions and find that the lengths H > H∗ that we explain in terms of the most and least preferred directions of charge density accumulation. We also consider the fractional eigenvector-following path with lengths Hf and Hfθmin.

47 CFR 74.644 - Minimum path lengths for fixed links.

Code of Federal Regulations, 2013 CFR

2013-10-01

... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table...

47 CFR 74.644 - Minimum path lengths for fixed links.

Code of Federal Regulations, 2010 CFR

2010-10-01

... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table...

47 CFR 74.644 - Minimum path lengths for fixed links.

Code of Federal Regulations, 2012 CFR

2012-10-01

... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table...

47 CFR 74.644 - Minimum path lengths for fixed links.

Code of Federal Regulations, 2014 CFR

2014-10-01

... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table...

47 CFR 74.644 - Minimum path lengths for fixed links.

Code of Federal Regulations, 2011 CFR

2011-10-01

... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the Table...

Two Upper Bounds for the Weighted Path Length of Binary Trees. Report No. UIUCDCS-R-73-565.

ERIC Educational Resources Information Center

Pradels, Jean Louis

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 indications about the expected time of a search or the length of a code, for example. In this paper, two sharp bounds for the total…

Comparison of Path Length and Ranges of Movement of the Center of Pressure and Reaction Time and Between Paired-Play and Solo-Play of a Virtual Reality Game.

PubMed

Portnoy, Sigal; Hersch, Ayelet; Sofer, Tal; Tresser, Sarit

2017-06-01

To test whether paired-play will induce longer path length and ranges of movement of the center of pressure (COP), which reflects on balance performance and stability, compared to solo-play and to test the difference in the path length and ranges of movement of the COP while playing the virtual reality (VR) game with the dominant hand compared to playing it with the nondominant hand. In this cross-sectional study 20 children (age 6.1 ± 0.7 years old) played an arm movement controlled VR game alone and with a peer while each of them stood on a pressure measuring pad to track the path length and ranges of movement of the COP. The total COP path was significantly higher during the paired-play (median 295.8 cm) compared to the COP path during the solo-play (median 189.2 cm). No significant differences were found in the reaction time and the mediolateral and anterior-posterior COP ranges between solo-play and paired-play. No significant differences were found between the parameters extracted during paired-play with the dominant or nondominant hand. Our findings imply that the paired-play is advantageous compared to solo-play since it induces a greater movement for the child, during which, higher COP velocities are reached that may contribute to improving the balance control of the child. Apart from the positive social benefits of paired-play, this positive effect on the COP path length is a noteworthy added value in the clinical setting when treating children with balance disorder.

Limited-path-length entanglement percolation in quantum complex networks

NASA Astrophysics Data System (ADS)

Cuquet, Martí; Calsamiglia, John

2011-03-01

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.

Quasi-monolithic tunable optical resonator

NASA Technical Reports Server (NTRS)

Arbore, Mark (Inventor); Tapos, Francisc (Inventor)

2003-01-01

An optical resonator has a piezoelectric element attached to a quasi-monolithic structure. The quasi-monolithic structure defines an optical path. Mirrors attached to the structure deflect light along the optical path. The piezoelectric element controllably strains the quasi-monolithic structure to change a length of the optical path by about 1 micron. A first feedback loop coupled to the piezoelectric element provides fine control over the cavity length. The resonator may include a thermally actuated spacer attached to the cavity and a mirror attached to the spacer. The thermally actuated spacer adjusts the cavity length by up to about 20 microns. A second feedback loop coupled to the sensor and heater provides a coarse control over the cavity length. An alternative embodiment provides a quasi-monolithic optical parametric oscillator (OPO). This embodiment includes a non-linear optical element within the resonator cavity along the optical path. Such an OPO configuration is broadly tunable and capable of mode-hop free operation for periods of 24 hours or more.

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

PubMed

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

2009-09-01

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

Excess entropy scaling for the segmental and global dynamics of polyethylene melts.

PubMed

Voyiatzis, Evangelos; Müller-Plathe, Florian; Böhm, Michael C

2014-11-28

The range of validity of the Rosenfeld and Dzugutov excess entropy scaling laws is analyzed for unentangled linear polyethylene chains. We consider two segmental dynamical quantities, i.e. the bond and the torsional relaxation times, and two global ones, i.e. the chain diffusion coefficient and the viscosity. The excess entropy is approximated by either a series expansion of the entropy in terms of the pair correlation function or by an equation of state for polymers developed in the context of the self associating fluid theory. For the whole range of temperatures and chain lengths considered, the two estimates of the excess entropy are linearly correlated. The scaled bond and torsional relaxation times fall into a master curve irrespective of the chain length and the employed scaling scheme. Both quantities depend non-linearly on the excess entropy. For a fixed chain length, the reduced diffusion coefficient and viscosity scale linearly with the excess entropy. An empirical reduction to a chain length-independent master curve is accessible for both dynamic quantities. The Dzugutov scheme predicts an increased value of the scaled diffusion coefficient with increasing chain length which contrasts physical expectations. The origin of this trend can be traced back to the density dependence of the scaling factors. This finding has not been observed previously for Lennard-Jones chain systems (Macromolecules, 2013, 46, 8710-8723). Thus, it limits the applicability of the Dzugutov approach to polymers. In connection with diffusion coefficients and viscosities, the Rosenfeld scaling law appears to be of higher quality than the Dzugutov approach. An empirical excess entropy scaling is also proposed which leads to a chain length-independent correlation. It is expected to be valid for polymers in the Rouse regime.

Microminiature optical waveguide structure and method for fabrication

DOEpatents

Strand, O.T.; Deri, R.J.; Pocha, M.D.

1998-12-08

A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed. Alternatively, the pedestals can be patterned to taper along their lengths on the surface of the substrate. This will cause the waveguides to assume a conical taper after reflowing by heat. 32 figs.

Microminiature optical waveguide structure and method for fabrication

DOEpatents

Strand, Oliver T.; Deri, Robert J.; Pocha, Michael D.

1998-01-01

A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed. Alternatively, the pedestals can be patterned to taper along their lengths on the surface of the substrate. This will cause the waveguides to assume a conical taper after reflowing by heat.

Atmospheric phase characteristics of the ALMA long baseline

NASA Astrophysics Data System (ADS)

Matsushita, Satoki; Asaki, Yoshiharu; Fomalont, Edward B.; Barkats, Denis; Corder, Stuartt A.; Hills, Richard E.; Kawabe, Ryohei; Maud, Luke T.; Morita, Koh-Ichiro; Nikolic, Bojan; Tilanus, Remo P. J.; Vlahakis, Catherine

2016-07-01

Atacama Large Millimeter/submillimeter Array (ALMA) is the world's largest millimeter/ submillimeter (mm / Submm) interferometer. Along with science observations, ALMA has performed several long baseline campaigns in the last 6 years to characterize and optimize its long baseline capabilities. To achieve full long baseline capability of ALMA, it is important to understand the characteristics of atmospheric phase fluctuation at long baselines, since it is believed to be the main cause of mm/submm image degradation. For the first time, we present detailed properties of atmospheric phase fluctuation at mm/submm wavelength from baselines up to 15 km in length. Atmospheric phase fluctuation increases as a function of baseline length with a power-law slope close to 0.6, and many of the data display a shallower slope (02.-03) at baseline length greater than about 15 km. Some of the data, on the other hand, show a single slope up to the maximum baseline length of around 15 km. The phase correction method based on water vapor radiometers (WVRs) works well, especially for cases with precipitable water vapor (PWV) greater than 1 mm, typically yielding a 50% decrease or more in the degree of phase fluctuation. However, signicant amount of atmospheric phase fluctuation still remains after the WVR phase correction: about 200 micron in rms excess path length (rms phase fluctuation in unit of length) even at PWV less than 1 mm. This result suggests the existence of other non-water-vapor sources of phase fluctuation. and emphasizes the need for additional phase correction methods, such as band-to-band and/or fast switching.

Carotid-Femoral Pulse Wave Velocity: Impact of Different Arterial Path Length Measurements

PubMed Central

Sugawara, Jun; Hayashi, Koichiro; Yokoi, Takashi; Tanaka, Hirofumi

2009-01-01

Background Carotid-femoral pulse wave velocity (PWV) is the most established index of arterial stiffness. Yet there is no consensus on the methodology in regard to the arterial path length measurements conducted on the body surface. Currently, it is not known to what extent the differences in the arterial path length measurements affect absolute PWV values. Methods Two hundred fifty apparently healthy adults (127 men and 123 women, 19-79 years) were studied. Carotid-femoral PWV was calculated using (1) the straight distance between carotid and femoral sites (PWVcar–fem), (2) the straight distance between suprasternal notch and femoral site minus carotid arterial length (PWV(ssn–fem)-(ssn–car)), (3) the straight distance between carotid and femoral sites minus carotid arterial length (PWV(car–fem)-(ssn–car)), and (4) the combined distance from carotid site to the umbilicus and from the umbilicus to femoral site minus carotid arterial length (PWV(ssn–umb–fem)-(ssn–car)). Results All the calculated PWV were significantly correlated with each other (r=0.966-0.995). PWV accounting for carotid arterial length were 16-31% lower than PWVcar–fem. PWVcar–fem value of 12 m/sec corresponded to 8.3 m/sec for PWV(ssn–fem)-(ssn–car), 10.0 m/sec for PWV(car–fem)-(ssn–car), and 8.9 m/sec for PWV(ssn–umb–fem)-(ssn–car). Conclusion Different body surface measurements used to estimate arterial path length would produce substantial variations in absolute PWV values. PMID:20396400

A flight investigation with a STOL airplane flying curved, descending instrument approach paths

NASA Technical Reports Server (NTRS)

Benner, M. S.; Mclaughlin, M. D.; Sawyer, R. H.; Vangunst, R.; Ryan, J. L.

1974-01-01

A flight investigation using a De Havilland Twin Otter airplane was conducted to determine the configurations of curved, 6 deg descending approach paths which would provide minimum airspace usage within the requirements for acceptable commercial STOL airplane operations. Path configurations with turns of 90 deg, 135 deg, and 180 deg were studied; the approach airspeed was 75 knots. The length of the segment prior to turn, the turn radius, and the length of the final approach segment were varied. The relationship of the acceptable path configurations to the proposed microwave landing system azimuth coverage requirements was examined.

Open-path spectroscopic methane detection using a broadband monolithic distributed feedback-quantum cascade laser array.

PubMed

Michel, Anna P M; Kapit, Jason; Witinski, Mark F; Blanchard, Romain

2017-04-10

Methane is a powerful greenhouse gas that has both natural and anthropogenic sources. The ability to measure methane using an integrated path length approach such as an open/long-path length sensor would be beneficial in several environments for examining anthropogenic and natural sources, including tundra landscapes, rivers, lakes, landfills, estuaries, fracking sites, pipelines, and agricultural sites. Here a broadband monolithic distributed feedback-quantum cascade laser array was utilized as the source for an open-path methane sensor. Two telescopes were utilized for the launch (laser source) and receiver (detector) in a bistatic configuration for methane sensing across a 50 m path length. Direct-absorption spectroscopy was utilized with intrapulse tuning. Ambient methane levels were detectable, and an instrument precision of 70 ppb with 100 s averaging and 90 ppb with 10 s averaging was achieved. The sensor system was designed to work "off the grid" and utilizes batteries that are rechargeable with solar panels and wind turbines.

Accurate cell counts in live mouse embryos using optical quadrature and differential interference contrast microscopy

NASA Astrophysics Data System (ADS)

Warger, William C., II; Newmark, Judith A.; Zhao, Bing; Warner, Carol M.; DiMarzio, Charles A.

2006-02-01

Present imaging techniques used in in vitro fertilization (IVF) clinics are unable to produce accurate cell counts in developing embryos past the eight-cell stage. We have developed a method that has produced accurate cell counts in live mouse embryos ranging from 13-25 cells by combining Differential Interference Contrast (DIC) and Optical Quadrature Microscopy. Optical Quadrature Microscopy is an interferometric imaging modality that measures the amplitude and phase of the signal beam that travels through the embryo. The phase is transformed into an image of optical path length difference, which is used to determine the maximum optical path length deviation of a single cell. DIC microscopy gives distinct cell boundaries for cells within the focal plane when other cells do not lie in the path to the objective. Fitting an ellipse to the boundary of a single cell in the DIC image and combining it with the maximum optical path length deviation of a single cell creates an ellipsoidal model cell of optical path length deviation. Subtracting the model cell from the Optical Quadrature image will either show the optical path length deviation of the culture medium or reveal another cell underneath. Once all the boundaries are used in the DIC image, the subtracted Optical Quadrature image is analyzed to determine the cell boundaries of the remaining cells. The final cell count is produced when no more cells can be subtracted. We have produced exact cell counts on 5 samples, which have been validated by Epi-Fluorescence images of Hoechst stained nuclei.

Spatio-Temporal Structure, Path Characteristics, and Perceptual Grouping in Immediate Serial Spatial Recall

PubMed Central

De Lillo, Carlo; Kirby, Melissa; Poole, Daniel

2016-01-01

Immediate serial spatial recall measures the ability to retain sequences of locations in short-term memory and is considered the spatial equivalent of digit span. It is tested by requiring participants to reproduce sequences of movements performed by an experimenter or displayed on a monitor. Different organizational factors dramatically affect serial spatial recall but they are often confounded or underspecified. Untangling them is crucial for the characterization of working-memory models and for establishing the contribution of structure and memory capacity to spatial span. We report five experiments assessing the relative role and independence of factors that have been reported in the literature. Experiment 1 disentangled the effects of spatial clustering and path-length by manipulating the distance of items displayed on a touchscreen monitor. Long-path sequences segregated by spatial clusters were compared with short-path sequences not segregated by clusters. Recall was more accurate for sequences segregated by clusters independently from path-length. Experiment 2 featured conditions where temporal pauses were introduced between or within cluster boundaries during the presentation of sequences with the same paths. Thus, the temporal structure of the sequences was either consistent or inconsistent with a hierarchical representation based on segmentation by spatial clusters but the effect of structure could not be confounded with effects of path-characteristics. Pauses at cluster boundaries yielded more accurate recall, as predicted by a hierarchical model. In Experiment 3, the systematic manipulation of sequence structure, path-length, and presence of path-crossings of sequences showed that structure explained most of the variance, followed by the presence/absence of path-crossings, and path-length. Experiments 4 and 5 replicated the results of the previous experiments in immersive virtual reality navigation tasks where the viewpoint of the observer changed dynamically during encoding and recall. This suggested that the effects of structure in spatial span are not dependent on perceptual grouping processes induced by the aerial view of the stimulus array typically afforded by spatial recall tasks. These results demonstrate the independence of coding strategies based on structure from effects of path characteristics and perceptual grouping in immediate serial spatial recall. PMID:27891101

Automatic Control Of Length Of Welding Arc

NASA Technical Reports Server (NTRS)

Iceland, William F.

1991-01-01

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

Spreading paths in partially observed social networks

NASA Astrophysics Data System (ADS)

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-03-01

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

Spreading paths in partially observed social networks.

PubMed

Onnela, Jukka-Pekka; Christakis, Nicholas A

2012-03-01

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

Laser-guided, intersecting discharge channels for the final beam transport in heavy-ion fusion

NASA Astrophysics Data System (ADS)

Niemann, C.; Neff, S.; Tauschwitz, A.; Penache, D.; Birkner, R.; Constantin, C.; Knobloch, R.; Presura, R.; Rosmej, F. B.; Hoffmann, D. H. H.; Yu, S. S.

2003-06-01

Ion-beam transport in space charge neutralizing discharge channels has been proposed for the final focus and chamber transport in a heavy-ion fusion reactor. A driver scenario with two-sided target illumination requires a system of two intersecting discharges to transport beams of the same charge from opposite sides towards the fusion target. In this article we report on experiments on the creation of free-standing, intersecting high-current discharge channels. The discharges are initiated in ammonia gas (NH3) in a metallic chamber by two perpendicular CO2-laser beams, which resonantly heat and subsequently rarefy the gas along the laser paths before the breakdown. These low density channels guide the discharges along the predefined paths and also around the 90° angles without any mechanical guiding structures. In this way stable X-, T-, and L-shaped discharges with currents in excess of 40 kA, at pressures of a few mbar were created with a total length of 110 cm. An 11.4 A MeV 58Ni+12 beam from the UNILAC (Universal Linear Accelerator) linear accelerator was used to probe the line-integrated ion-optical properties of the central channel in a T-shaped discharge.

High power tube solid-state laser with zigzag propagation of pump and laser beam

NASA Astrophysics Data System (ADS)

Savich, Michael

2015-02-01

A novel resonator and pumping design with zigzag propagation of pumping and laser beams permits to design an improved tube Solid State Laser (SSL), solving the problem of short absorption path to produce a high power laser beam (100 - 1000kW). The novel design provides an amplifier module and laser oscillator. The tube-shaped SSL includes a gain element fiber-optically coupled to a pumping source. The fiber optic coupling facilitates light entry at compound Brewster's angle of incidence into the laser gain element and uses internal reflection to follow a "zigzag" path in a generally spiral direction along the length of the tube. Optics are arranged for zigzag propagation of the laser beam, while the cryogenic cooling system is traditional. The novel method of lasing uses advantages of cylindrical geometry to reach the high volume of gain medium with compactness and structural rigidity, attain high pump density and uniformity, and reach a low threshold without excessive increase of the temperature of the crystal. The design minimizes thermal lensing and stress effects, and provides high gain amplification, high power extraction from lasing medium, high pumping and lasing efficiency and a high beam quality.

Refractive indices used by the Haag-Streit Lenstar to calculate axial biometric dimensions.

PubMed

Suheimat, Marwan; Verkicharla, Pavan K; Mallen, Edward A H; Rozema, Jos J; Atchison, David A

2015-01-01

To estimate refractive indices used by the Lenstar biometer to translate measured optical path lengths into geometrical path lengths within the eye. Axial lengths of model eyes were determined using the IOLMaster and Lenstar biometers; comparing those lengths gave an overall eye refractive index estimate for the Lenstar. Using the Lenstar Graphical User Interface, we noticed that boundaries between media could be manipulated and opposite changes in optical path lengths on either side of the boundary could be introduced. Those ratios were combined with the overall eye refractive index to estimate separate refractive indices. Furthermore, Haag-Streit provided us with a template to obtain 'air thicknesses' to compare with geometrical distances. The axial length estimates obtained using the IOLMaster and the Lenstar agreed to within 0.01 mm. Estimates of group refractive indices used in the Lenstar were 1.340, 1.341, 1.415, and 1.354 for cornea, aqueous, lens, and overall eye, respectively. Those refractive indices did not match those of schematic eyes, but were close in the cases of aqueous and lens. Linear equations relating air thicknesses to geometrical thicknesses were consistent with our findings. The Lenstar uses different refractive indices for different ocular media. Some of the refractive indices, such as that for the cornea, are not physiological; therefore, it is likely that the calibrations in the instrument correspond to instrument-specific corrections and are not the real optical path lengths. © 2014 The Authors Ophthalmic & Physiological Optics © 2014 The College of Optometrists.

Method for Veterbi decoding of large constraint length convolutional codes

NASA Technical Reports Server (NTRS)

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

1988-01-01

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

Rationalizing spatial exploration patterns of wild animals and humans through a temporal discounting framework.

PubMed

Namboodiri, Vijay Mohan K; Levy, Joshua M; Mihalas, Stefan; Sims, David W; Hussain Shuler, Marshall G

2016-08-02

Understanding the exploration patterns of foragers in the wild provides fundamental insight into animal behavior. Recent experimental evidence has demonstrated that path lengths (distances between consecutive turns) taken by foragers are well fitted by a power law distribution. Numerous theoretical contributions have posited that "Lévy random walks"-which can produce power law path length distributions-are optimal for memoryless agents searching a sparse reward landscape. It is unclear, however, whether such a strategy is efficient for cognitively complex agents, from wild animals to humans. Here, we developed a model to explain the emergence of apparent power law path length distributions in animals that can learn about their environments. In our model, the agent's goal during search is to build an internal model of the distribution of rewards in space that takes into account the cost of time to reach distant locations (i.e., temporally discounting rewards). For an agent with such a goal, we find that an optimal model of exploration in fact produces hyperbolic path lengths, which are well approximated by power laws. We then provide support for our model by showing that humans in a laboratory spatial exploration task search space systematically and modify their search patterns under a cost of time. In addition, we find that path length distributions in a large dataset obtained from free-ranging marine vertebrates are well described by our hyperbolic model. Thus, we provide a general theoretical framework for understanding spatial exploration patterns of cognitively complex foragers.

Study on the measuring distance for blood glucose infrared spectral measuring by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Li, Xiang

2016-10-01

Blood glucose monitoring is of great importance for controlling diabetes procedure and preventing the complications. At present, the clinical blood glucose concentration measurement is invasive and could be replaced by noninvasive spectroscopy analytical techniques. Among various parameters of optical fiber probe used in spectrum measuring, the measurement distance is the key one. The Monte Carlo technique is a flexible method for simulating light propagation in tissue. The simulation is based on the random walks that photons make as they travel through tissue, which are chosen by statistically sampling the probability distributions for step size and angular deflection per scattering event. The traditional method for determine the optimal distance between transmitting fiber and detector is using Monte Carlo simulation to find out the point where most photons come out. But there is a problem. In the epidermal layer there is no artery, vein or capillary vessel. Thus, when photons propagate and interactive with tissue in epidermal layer, no information is given to the photons. A new criterion is proposed to determine the optimal distance, which is named effective path length in this paper. The path length of each photons travelling in dermis is recorded when running Monte-Carlo simulation, which is the effective path length defined above. The sum of effective path length of every photon at each point is calculated. The detector should be place on the point which has most effective path length. Then the optimal measuring distance between transmitting fiber and detector is determined.

Diffusing-wave spectroscopy in a standard dynamic light scattering setup

NASA Astrophysics Data System (ADS)

Fahimi, Zahra; Aangenendt, Frank J.; Voudouris, Panayiotis; Mattsson, Johan; Wyss, Hans M.

2017-12-01

Diffusing-wave spectroscopy (DWS) extends dynamic light scattering measurements to samples with strong multiple scattering. DWS treats the transport of photons through turbid samples as a diffusion process, thereby making it possible to extract the dynamics of scatterers from measured correlation functions. The analysis of DWS data requires knowledge of the path length distribution of photons traveling through the sample. While for flat sample cells this path length distribution can be readily calculated and expressed in analytical form; no such expression is available for cylindrical sample cells. DWS measurements have therefore typically relied on dedicated setups that use flat sample cells. Here we show how DWS measurements, in particular DWS-based microrheology measurements, can be performed in standard dynamic light scattering setups that use cylindrical sample cells. To do so we perform simple random-walk simulations that yield numerical predictions of the path length distribution as a function of both the transport mean free path and the detection angle. This information is used in experiments to extract the mean-square displacement of tracer particles in the material, as well as the corresponding frequency-dependent viscoelastic response. An important advantage of our approach is that by performing measurements at different detection angles, the average path length through the sample can be varied. For measurements performed on a single sample cell, this gives access to a wider range of length and time scales than obtained in a conventional DWS setup. Such angle-dependent measurements also offer an important consistency check, as for all detection angles the DWS analysis should yield the same tracer dynamics, even though the respective path length distributions are very different. We validate our approach by performing measurements both on aqueous suspensions of tracer particles and on solidlike gelatin samples, for which we find our DWS-based microrheology data to be in good agreement with rheological measurements performed on the same samples.

The Edge-Disjoint Path Problem on Random Graphs by Message-Passing.

PubMed

Altarelli, Fabrizio; Braunstein, Alfredo; Dall'Asta, Luca; De Bacco, Caterina; Franz, Silvio

2015-01-01

We present a message-passing algorithm to solve a series of edge-disjoint path problems on graphs based on the zero-temperature cavity equations. Edge-disjoint paths problems are important in the general context of routing, that can be defined by incorporating under a unique framework both traffic optimization and total path length minimization. The computation of the cavity equations can be performed efficiently by exploiting a mapping of a generalized edge-disjoint path problem on a star graph onto a weighted maximum matching problem. We perform extensive numerical simulations on random graphs of various types to test the performance both in terms of path length minimization and maximization of the number of accommodated paths. In addition, we test the performance on benchmark instances on various graphs by comparison with state-of-the-art algorithms and results found in the literature. Our message-passing algorithm always outperforms the others in terms of the number of accommodated paths when considering non trivial instances (otherwise it gives the same trivial results). Remarkably, the largest improvement in performance with respect to the other methods employed is found in the case of benchmarks with meshes, where the validity hypothesis behind message-passing is expected to worsen. In these cases, even though the exact message-passing equations do not converge, by introducing a reinforcement parameter to force convergence towards a sub optimal solution, we were able to always outperform the other algorithms with a peak of 27% performance improvement in terms of accommodated paths. On random graphs, we numerically observe two separated regimes: one in which all paths can be accommodated and one in which this is not possible. We also investigate the behavior of both the number of paths to be accommodated and their minimum total length.

The Edge-Disjoint Path Problem on Random Graphs by Message-Passing

PubMed Central

2015-01-01

We present a message-passing algorithm to solve a series of edge-disjoint path problems on graphs based on the zero-temperature cavity equations. Edge-disjoint paths problems are important in the general context of routing, that can be defined by incorporating under a unique framework both traffic optimization and total path length minimization. The computation of the cavity equations can be performed efficiently by exploiting a mapping of a generalized edge-disjoint path problem on a star graph onto a weighted maximum matching problem. We perform extensive numerical simulations on random graphs of various types to test the performance both in terms of path length minimization and maximization of the number of accommodated paths. In addition, we test the performance on benchmark instances on various graphs by comparison with state-of-the-art algorithms and results found in the literature. Our message-passing algorithm always outperforms the others in terms of the number of accommodated paths when considering non trivial instances (otherwise it gives the same trivial results). Remarkably, the largest improvement in performance with respect to the other methods employed is found in the case of benchmarks with meshes, where the validity hypothesis behind message-passing is expected to worsen. In these cases, even though the exact message-passing equations do not converge, by introducing a reinforcement parameter to force convergence towards a sub optimal solution, we were able to always outperform the other algorithms with a peak of 27% performance improvement in terms of accommodated paths. On random graphs, we numerically observe two separated regimes: one in which all paths can be accommodated and one in which this is not possible. We also investigate the behavior of both the number of paths to be accommodated and their minimum total length. PMID:26710102

An Efficient Wireless Recharging Mechanism for Achieving Perpetual Lifetime of Wireless Sensor Networks

PubMed Central

Yu, Hongli; Chen, Guilin; Zhao, Shenghui; Chang, Chih-Yung; Chin, Yu-Ting

2016-01-01

Energy recharging has received much attention in recent years. Several recharging mechanisms were proposed for achieving perpetual lifetime of a given Wireless Sensor Network (WSN). However, most of them require a mobile recharger to visit each sensor and then perform the recharging task, which increases the length of the recharging path. Another common weakness of these works is the requirement for the mobile recharger to stop at the location of each sensor. As a result, it is impossible for recharger to move with a constant speed, leading to inefficient movement. To improve the recharging efficiency, this paper takes “recharging while moving” into consideration when constructing the recharging path. We propose a Recharging Path Construction (RPC) mechanism, which enables the mobile recharger to recharge all sensors using a constant speed, aiming to minimize the length of recharging path and improve the recharging efficiency while achieving the requirement of perpetual network lifetime of a given WSN. Performance studies reveal that the proposed RPC outperforms existing proposals in terms of path length and energy utilization index, as well as visiting cycle. PMID:28025567

Why Lévy Foraging does not need to be 'unshackled' from Optimal Foraging Theory. Comment on "Liberating Lévy walk research from the shackles of optimal foraging" by A.M. Reynolds

NASA Astrophysics Data System (ADS)

Humphries, Nicolas E.

2015-09-01

The comprehensive review of Lévy patterns observed in the moves and pauses of a vast array of organisms by Reynolds [1] makes clear a need to attempt to unify phenomena to understand how organism movement may have evolved. However, I would contend that the research on Lévy 'movement patterns' we detect in time series of animal movements has to a large extent been misunderstood. The statistical techniques, such as Maximum Likelihood Estimation, used to detect these patterns look only at the statistical distribution of move step-lengths and not at the actual pattern, or structure, of the movement path. The path structure is lost altogether when move step-lengths are sorted prior to analysis. Likewise, the simulated movement paths, with step-lengths drawn from a truncated power law distribution in order to test characteristics of the path, such as foraging efficiency, in no way match the actual paths, or trajectories, of real animals. These statistical distributions are, therefore, null models of searching or foraging activity. What has proved surprising about these step-length distributions is the extent to which they improve the efficiency of random searches over simple Brownian motion. It has been shown unequivocally that a power law distribution of move step lengths is more efficient, in terms of prey items located per unit distance travelled, than any other distribution of move step-lengths so far tested (up to 3 times better than Brownian), and over a range of prey field densities spanning more than 4 orders of magnitude [2].

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

DOEpatents

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

2005-08-30

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

Multiple-wavelength tunable laser

NASA Technical Reports Server (NTRS)

Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

2010-01-01

A tunable laser includes dispersion optics for separating generated laser pulses into first and second wavelength pulses directed along first and second optical paths. First and second reflective mirrors are disposed in the first and second optical paths, respectively. The laser's output mirror is partially reflective and partially transmissive with respect to the first wavelength and the second wavelength in accordance with provided criteria. A first resonator length is defined between the output mirror and the first mirror, while a second resonator length is defined between the output mirror and the second mirror. The second resonator length is a function of the first resonator length.

A New Look into the Effect of Large Drops on Radiative Transfer Process

NASA Technical Reports Server (NTRS)

Marshak, Alexander

2003-01-01

Recent studies indicate that a cloudy atmosphere absorbs more solar radiation than any current 1D or 3D radiation model can predict. The excess absorption is not large, perhaps 10-15 W/sq m or less, but any such systematic bias is of concern since radiative transfer models are assumed to be sufficiently accurate for remote sensing applications and climate modeling. The most natural explanation would be that models do not capture real 3D cloud structure and, as a consequence, their photon path lengths are too short. However, extensive calculations, using increasingly realistic 3D cloud structures, failed to produce photon paths long enough to explain the excess absorption. Other possible explanations have also been unsuccessful so, at this point, conventional models seem to offer no solution to this puzzle. The weakest link in conventional models is the way a size distribution of cloud particles is mathematically handled. Basically, real particles are replaced with a single average particle. This "ensemble assumption" assumes that all particle sizes are well represented in any given elementary volume. But the concentration of larger particles can be so low that this assumption is significantly violated. We show how a different mathematical route, using the concept of a cumulative distribution, avoids the ensemble assumption. The cumulative distribution has jumps, or steps, corresponding to the rarer sizes. These jumps result in an additional term, a kind of Green's function, in the solution of the radiative transfer equation. Solving the cloud radiative transfer equation with the measured particle distributions, described in a cumulative rather than an ensemble fashion, may lead to increased cloud absorption of the magnitude observed.

Trajectory generation for an on-road autonomous vehicle

NASA Astrophysics Data System (ADS)

Horst, John; Barbera, Anthony

2006-05-01

We describe an algorithm that generates a smooth trajectory (position, velocity, and acceleration at uniformly sampled instants of time) for a car-like vehicle autonomously navigating within the constraints of lanes in a road. The technique models both vehicle paths and lane segments as straight line segments and circular arcs for mathematical simplicity and elegance, which we contrast with cubic spline approaches. We develop the path in an idealized space, warp the path into real space and compute path length, generate a one-dimensional trajectory along the path length that achieves target speeds and positions, and finally, warp, translate, and rotate the one-dimensional trajectory points onto the path in real space. The algorithm moves a vehicle in lane safely and efficiently within speed and acceleration maximums. The algorithm functions in the context of other autonomous driving functions within a carefully designed vehicle control hierarchy.

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

DOEpatents

Douglas, David R.; Neil, George R.

2005-04-26

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

Comparison of transtibial amputee and non-amputee biomechanics during a common turning task.

PubMed

Segal, Ava D; Orendurff, Michael S; Czerniecki, Joseph M; Schoen, Jason; Klute, Glenn K

2011-01-01

The biomechanics of amputee turning gait has been minimally studied, in spite of its integral relationship with the more complex gait required for household or community ambulation. This study compares the biomechanics of unilateral transtibial amputees and non-amputees completing a common turning task. Full body gait analysis was completed for subjects walking at comparable self-selected speeds around a 1m radius circular path. Peak internal and external rotation moments of the hip, knee and ankle, mediolateral ground reaction impulse (ML GRI), peak effective limb length, and stride length were compared across conditions (non-amputee, amputee prosthetic limb, amputee sound limb). Amputees showed decreased internal rotation moments at the prosthetic limb hip and knee compared to non-amputees, perhaps as a protective mechanism to minimize stress on the residual limb. There was also an increase in amputee sound limb hip external rotation moment in early stance compared to non-amputees, which may be a compensation for the decrease in prosthetic limb internal rotation moment during late stance of the prior step. ML GRI was decreased for the amputee inside limb compared to non-amputee, possibly to minimize the body's acceleration in the direction of the turn. Amputees also exhibited a shorter inside limb stride length compared to non-amputees. Both decreased ML GRI and stride length indicate a COM that is more centered over the base of support, which may minimize the risk of falling. Finally, a longer effective limb length was found for the amputee inside limb turning, possibly due to excessive trunk shift. Published by Elsevier B.V.

A two-stage path planning approach for multiple car-like robots based on PH curves and a modified harmony search algorithm

NASA Astrophysics Data System (ADS)

Zeng, Wenhui; Yi, Jin; Rao, Xiao; Zheng, Yun

2017-11-01

In this article, collision-avoidance path planning for multiple car-like robots with variable motion is formulated as a two-stage objective optimization problem minimizing both the total length of all paths and the task's completion time. Accordingly, a new approach based on Pythagorean Hodograph (PH) curves and Modified Harmony Search algorithm is proposed to solve the two-stage path-planning problem subject to kinematic constraints such as velocity, acceleration, and minimum turning radius. First, a method of path planning based on PH curves for a single robot is proposed. Second, a mathematical model of the two-stage path-planning problem for multiple car-like robots with variable motion subject to kinematic constraints is constructed that the first-stage minimizes the total length of all paths and the second-stage minimizes the task's completion time. Finally, a modified harmony search algorithm is applied to solve the two-stage optimization problem. A set of experiments demonstrate the effectiveness of the proposed approach.

Efficient sampling of parsimonious inversion histories with application to genome rearrangement in Yersinia.

PubMed

Miklós, István; Darling, Aaron E

2009-06-22

Inversions are among the most common mutations acting on the order and orientation of genes in a genome, and polynomial-time algorithms exist to obtain a minimal length series of inversions that transform one genome arrangement to another. However, the minimum length series of inversions (the optimal sorting path) is often not unique as many such optimal sorting paths exist. If we assume that all optimal sorting paths are equally likely, then statistical inference on genome arrangement history must account for all such sorting paths and not just a single estimate. No deterministic polynomial algorithm is known to count the number of optimal sorting paths nor sample from the uniform distribution of optimal sorting paths. Here, we propose a stochastic method that uniformly samples the set of all optimal sorting paths. Our method uses a novel formulation of parallel Markov chain Monte Carlo. In practice, our method can quickly estimate the total number of optimal sorting paths. We introduce a variant of our approach in which short inversions are modeled to be more likely, and we show how the method can be used to estimate the distribution of inversion lengths and breakpoint usage in pathogenic Yersinia pestis. The proposed method has been implemented in a program called "MC4Inversion." We draw comparison of MC4Inversion to the sampler implemented in BADGER and a previously described importance sampling (IS) technique. We find that on high-divergence data sets, MC4Inversion finds more optimal sorting paths per second than BADGER and the IS technique and simultaneously avoids bias inherent in the IS technique.

Finding False Paths in Sequential Circuits

NASA Astrophysics Data System (ADS)

Matrosova, A. Yu.; Andreeva, V. V.; Chernyshov, S. V.; Rozhkova, S. V.; Kudin, D. V.

2018-02-01

Method of finding false paths in sequential circuits is developed. In contrast with heuristic approaches currently used abroad, the precise method based on applying operations on Reduced Ordered Binary Decision Diagrams (ROBDDs) extracted from the combinational part of a sequential controlling logic circuit is suggested. The method allows finding false paths when transfer sequence length is not more than the given value and obviates the necessity of investigation of combinational circuit equivalents of the given lengths. The possibilities of using of the developed method for more complicated circuits are discussed.

Physico-chemical properties of binary mixtures of aliphatic and aromatic solvents at 313 K on acoustical data

NASA Astrophysics Data System (ADS)

Dahire, S. L.; Morey, Y. C.; Agrawal, P. S.

2015-12-01

Density (ρ), viscosity (η), and ultrasonic velocity ( U) of binary mixtures of aliphatic solvents like dimethylformamide (DMF) and dimethylsulfoxide (DMSO) with aromatic solvents viz. chlorobenzene (CB), bromobenzene (BB), and nitrobenzene (NB) have been determined at 313 K. These parameters were used to calculate the adiabatic compressibility (β), intermolecular free length ( L f), molar volume ( V m), and acoustic impedance ( Z). From the experimental data excess molar volume ( V m E ), excess intermolecular free length ( L f E )), excess adiabatic compressibility (βE), and excess acoustic impedance ( Z E) have been computed. The excess values were correlated using Redlich-Kister polynomial equation to obtain their coefficients and standard deviations (σ).

Rationalizing spatial exploration patterns of wild animals and humans through a temporal discounting framework

PubMed Central

Namboodiri, Vijay Mohan K.; Levy, Joshua M.; Mihalas, Stefan; Sims, David W.; Hussain Shuler, Marshall G.

2016-01-01

Understanding the exploration patterns of foragers in the wild provides fundamental insight into animal behavior. Recent experimental evidence has demonstrated that path lengths (distances between consecutive turns) taken by foragers are well fitted by a power law distribution. Numerous theoretical contributions have posited that “Lévy random walks”—which can produce power law path length distributions—are optimal for memoryless agents searching a sparse reward landscape. It is unclear, however, whether such a strategy is efficient for cognitively complex agents, from wild animals to humans. Here, we developed a model to explain the emergence of apparent power law path length distributions in animals that can learn about their environments. In our model, the agent’s goal during search is to build an internal model of the distribution of rewards in space that takes into account the cost of time to reach distant locations (i.e., temporally discounting rewards). For an agent with such a goal, we find that an optimal model of exploration in fact produces hyperbolic path lengths, which are well approximated by power laws. We then provide support for our model by showing that humans in a laboratory spatial exploration task search space systematically and modify their search patterns under a cost of time. In addition, we find that path length distributions in a large dataset obtained from free-ranging marine vertebrates are well described by our hyperbolic model. Thus, we provide a general theoretical framework for understanding spatial exploration patterns of cognitively complex foragers. PMID:27385831

The semantic distance task: Quantifying semantic distance with semantic network path length.

PubMed

Kenett, Yoed N; Levi, Effi; Anaki, David; Faust, Miriam

2017-09-01

Semantic distance is a determining factor in cognitive processes, such as semantic priming, operating upon semantic memory. The main computational approach to compute semantic distance is through latent semantic analysis (LSA). However, objections have been raised against this approach, mainly in its failure at predicting semantic priming. We propose a novel approach to computing semantic distance, based on network science methodology. Path length in a semantic network represents the amount of steps needed to traverse from 1 word in the network to the other. We examine whether path length can be used as a measure of semantic distance, by investigating how path length affect performance in a semantic relatedness judgment task and recall from memory. Our results show a differential effect on performance: Up to 4 steps separating between word-pairs, participants exhibit an increase in reaction time (RT) and decrease in the percentage of word-pairs judged as related. From 4 steps onward, participants exhibit a significant decrease in RT and the word-pairs are dominantly judged as unrelated. Furthermore, we show that as path length between word-pairs increases, success in free- and cued-recall decreases. Finally, we demonstrate how our measure outperforms computational methods measuring semantic distance (LSA and positive pointwise mutual information) in predicting participants RT and subjective judgments of semantic strength. Thus, we provide a computational alternative to computing semantic distance. Furthermore, this approach addresses key issues in cognitive theory, namely the breadth of the spreading activation process and the effect of semantic distance on memory retrieval. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The estimation of the propagation delay through the troposphere from microwave radiometer data. [very long base interferometry

NASA Technical Reports Server (NTRS)

Moran, J. M.; Rosen, B. R.

1980-01-01

The uncertainity in propagation delay estimates is due primarily to tropospheric water, the total amount and vertical distribution of which is variable. Because water vapor both delays and attenuates microwave signals, the propagation delay, or wet path length, can be estimated from the microwave brightness temperature near the 22.235 GHz transition of water vapor. The data from a total of 240 radiosonde launches taken simultaneously were analyzed. Estimates of brightness temperature at 19 and 22 GHz and wet path length were made from these data. The wet path length in the zenith direction could be estimated from the surface water vapor density to an accuracy of 5 cm for the summer data and 2 cm for winter data. Using the brightness temperatures, the wet path could be estimated to an accuracy of 0.3 cm. Two dual frequency radiometers were refurbished in order to test these techniques. These radiometers were capable of measuring the difference in the brightness temperature at 30 deg elevation angle and at the zenith to an accuracy of about 1 K. In August 1975, 45 radiosondes were launched over an 11 day period. Brightness temperature measurements were made simultaneously at 19 and 22 GHz with the radiometers. The rms error for the estimation of wet path length from surface meteorological parameters was 3.2 cm, and from the radiometer brightness temperatures, 1.5 cm.

Optimal solution for travelling salesman problem using heuristic shortest path algorithm with imprecise arc length

NASA Astrophysics Data System (ADS)

Bakar, Sumarni Abu; Ibrahim, Milbah

2017-08-01

The shortest path problem is a popular problem in graph theory. It is about finding a path with minimum length between a specified pair of vertices. In any network the weight of each edge is usually represented in a form of crisp real number and subsequently the weight is used in the calculation of shortest path problem using deterministic algorithms. However, due to failure, uncertainty is always encountered in practice whereby the weight of edge of the network is uncertain and imprecise. In this paper, a modified algorithm which utilized heuristic shortest path method and fuzzy approach is proposed for solving a network with imprecise arc length. Here, interval number and triangular fuzzy number in representing arc length of the network are considered. The modified algorithm is then applied to a specific example of the Travelling Salesman Problem (TSP). Total shortest distance obtained from this algorithm is then compared with the total distance obtained from traditional nearest neighbour heuristic algorithm. The result shows that the modified algorithm can provide not only on the sequence of visited cities which shown to be similar with traditional approach but it also provides a good measurement of total shortest distance which is lesser as compared to the total shortest distance calculated using traditional approach. Hence, this research could contribute to the enrichment of methods used in solving TSP.

Multiple-path model of spectral reflectance of a dyed fabric.

PubMed

Rogers, Geoffrey; Dalloz, Nicolas; Fournel, Thierry; Hebert, Mathieu

2017-05-01

Experimental results are presented of the spectral reflectance of a dyed fabric as analyzed by a multiple-path model of reflection. The multiple-path model provides simple analytic expressions for reflection and transmission of turbid media by applying the Beer-Lambert law to each path through the medium and summing over all paths, each path weighted by its probability. The path-length probability is determined by a random-walk analysis. The experimental results presented here show excellent agreement with predictions made by the model.

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

NASA Astrophysics Data System (ADS)

Kulig, Andrzej; DroŻdŻ, Stanisław; Kwapień, Jarosław; OświÈ©cimka, Paweł

2015-03-01

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

Efficient Sampling of Parsimonious Inversion Histories with Application to Genome Rearrangement in Yersinia

PubMed Central

Darling, Aaron E.

2009-01-01

Inversions are among the most common mutations acting on the order and orientation of genes in a genome, and polynomial-time algorithms exist to obtain a minimal length series of inversions that transform one genome arrangement to another. However, the minimum length series of inversions (the optimal sorting path) is often not unique as many such optimal sorting paths exist. If we assume that all optimal sorting paths are equally likely, then statistical inference on genome arrangement history must account for all such sorting paths and not just a single estimate. No deterministic polynomial algorithm is known to count the number of optimal sorting paths nor sample from the uniform distribution of optimal sorting paths. Here, we propose a stochastic method that uniformly samples the set of all optimal sorting paths. Our method uses a novel formulation of parallel Markov chain Monte Carlo. In practice, our method can quickly estimate the total number of optimal sorting paths. We introduce a variant of our approach in which short inversions are modeled to be more likely, and we show how the method can be used to estimate the distribution of inversion lengths and breakpoint usage in pathogenic Yersinia pestis. The proposed method has been implemented in a program called “MC4Inversion.” We draw comparison of MC4Inversion to the sampler implemented in BADGER and a previously described importance sampling (IS) technique. We find that on high-divergence data sets, MC4Inversion finds more optimal sorting paths per second than BADGER and the IS technique and simultaneously avoids bias inherent in the IS technique. PMID:20333186

Study of the De-Icing Properties of the ASDE-3 Rotodome.

DTIC Science & Technology

1982-04-01

Heat Transfer Coefficients ........................... 3 -18 3.2.3 Prediction of De-Icing Capability ...... 3 -23 3.2.4 Calculation of Mean DIA & PATH...kVA 3 -31 N NUL =ti: :6 i ::p :: %:::::28 -R) [ eN 23,100t Averaged for Laminar & Turbulent Regimes. SAssuming a transition from Laminar to. Turbulent...Calculation of Mean Dia .& Path Length for Roof Mean Path Length for Roof: y 4r 4x 9 3.82 ft 3 x 7 1 2(92 3.8221/2 1 = 2(92 - 3.822 = 8.15 ft x 2 16.3 ft 16.3

40 CFR 58.1 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... humidity, solar radiation, ultraviolet radiation, and/or precipitation. Metropolitan Statistical Area (MSA... receiver at opposite ends of the monitoring path; (2) Equal to twice the monitoring path length for a (monostatic) system having a transmitter and receiver at one end of the monitoring path and a mirror or...

40 CFR 58.1 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... humidity, solar radiation, ultraviolet radiation, and/or precipitation. Metropolitan Statistical Area (MSA... receiver at opposite ends of the monitoring path; (2) Equal to twice the monitoring path length for a (monostatic) system having a transmitter and receiver at one end of the monitoring path and a mirror or...

40 CFR 58.1 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... humidity, solar radiation, ultraviolet radiation, and/or precipitation. Metropolitan Statistical Area (MSA... receiver at opposite ends of the monitoring path; (2) Equal to twice the monitoring path length for a (monostatic) system having a transmitter and receiver at one end of the monitoring path and a mirror or...

Nodal distances for rooted phylogenetic trees.

PubMed

Cardona, Gabriel; Llabrés, Mercè; Rosselló, Francesc; Valiente, Gabriel

2010-08-01

Dissimilarity measures for (possibly weighted) phylogenetic trees based on the comparison of their vectors of path lengths between pairs of taxa, have been present in the systematics literature since the early seventies. For rooted phylogenetic trees, however, these vectors can only separate non-weighted binary trees, and therefore these dissimilarity measures are metrics only on this class of rooted phylogenetic trees. In this paper we overcome this problem, by splitting in a suitable way each path length between two taxa into two lengths. We prove that the resulting splitted path lengths matrices single out arbitrary rooted phylogenetic trees with nested taxa and arcs weighted in the set of positive real numbers. This allows the definition of metrics on this general class of rooted phylogenetic trees by comparing these matrices through metrics in spaces M(n)(R) of real-valued n x n matrices. We conclude this paper by establishing some basic facts about the metrics for non-weighted phylogenetic trees defined in this way using L(p) metrics on M(n)(R), with p [epsilon] R(>0).

Optimization of confocal laser induced fluorescence for long focal length applications

NASA Astrophysics Data System (ADS)

Jemiolo, Andrew J.; Henriquez, Miguel F.; Thompson, Derek S.; Scime, Earl E.

2017-10-01

Laser induced fluorescence (LIF) is a non-perturbative diagnostic for measuring ion and neutral particle velocities and temperatures in a plasma. The conventional method for single-photon LIF requires intersecting optical paths for light injection and collection. The multiple vacuum windows needed for such measurements are unavailable in many plasma experiments. Confocal LIF eliminates the need for perpendicular intersecting optical paths by using concentric injection and collection paths through a single window. One of the main challenges with using confocal LIF is achieving high resolution measurements at the longer focal lengths needed for many plasma experiments. We present confocal LIF measurements in HELIX, a helicon plasma experiment at West Virginia University, demonstrating spatial resolution dependence on focal length and spatial filtering. By combining aberration mitigating optics with spatial filtering, our results show high resolution measurements at focal lengths of 0.5 m, long enough to access the interiors of many laboratory plasma experiments. This work was supported by U.S. National Science Foundation Grant No. PHY-1360278.

Microscopic optical path length difference and polarization measurement system for cell analysis

NASA Astrophysics Data System (ADS)

Satake, H.; Ikeda, K.; Kowa, H.; Hoshiba, T.; Watanabe, E.

2018-03-01

In recent years, noninvasive, nonstaining, and nondestructive quantitative cell measurement techniques have become increasingly important in the medical field. These cell measurement techniques enable the quantitative analysis of living cells, and are therefore applied to various cell identification processes, such as those determining the passage number limit during cell culturing in regenerative medicine. To enable cell measurement, we developed a quantitative microscopic phase imaging system based on a Mach-Zehnder interferometer that measures the optical path length difference distribution without phase unwrapping using optical phase locking. The applicability of our phase imaging system was demonstrated by successful identification of breast cancer cells amongst normal cells. However, the cell identification method using this phase imaging system exhibited a false identification rate of approximately 7%. In this study, we implemented a polarimetric imaging system by introducing a polarimetric module to one arm of the Mach-Zehnder interferometer of our conventional phase imaging system. This module was comprised of a quarter wave plate and a rotational polarizer on the illumination side of the sample, and a linear polarizer on the optical detector side. In addition, we developed correction methods for the measurement errors of the optical path length and birefringence phase differences that arose through the influence of elements other than cells, such as the Petri dish. As the Petri dish holding the fluid specimens was transparent, it did not affect the amplitude information; however, the optical path length and birefringence phase differences were affected. Therefore, we proposed correction of the optical path length and birefringence phase for the influence of elements other than cells, as a prerequisite for obtaining highly precise phase and polarimetric images.

Reliability and feasibility of gait initiation centre-of-pressure excursions using a Wii® Balance Board in older adults at risk of falling.

PubMed

Lee, James; Webb, Graham; Shortland, Adam P; Edwards, Rebecca; Wilce, Charlotte; Jones, Gareth D

2018-04-17

Impairments in dynamic balance have a detrimental effect in older adults at risk of falls (OARF). Gait initiation (GI) is a challenging transitional movement. Centre of pressure (COP) excursions using force plates have been used to measure GI performance. The Nintendo Wii Balance Board (WBB) offers an alternative to a standard force plate for the measurement of CoP excursion. To determine the reliability of COP excursions using the WBB, and its feasibility within a 4-week strength and balance intervention (SBI) treating OARF. Ten OARF subjects attending SBI and ten young healthy adults, each performed three GI trials after 10 s of quiet stance from a standardised foot position (shoulder width) before walking forward 3 m to pick up an object. Averaged COP mediolateral (ML) and anteroposterior (AP) excursions (distance) and path-length time (GI-onset to first toe-off) were analysed. WBB ML (0.866) and AP COP excursion (0.895) reliability (ICC 3,1 ) was excellent, and COP path-length reliability was fair (0.517). Compared to OARF, healthy subjects presented with larger COP excursion in both directions and shorter COP path length. OARF subjects meaningfully improved their timed-up-and-go and ML COP excursion between weeks 1-4, while AP COP excursions, path length, and confidence-in-balance remained stable. COP path length and excursion directions probably measure different GI postural control attributes. Limitations in WBB accuracy and precision in transition tasks needs to be established before it can be used clinically to measure postural aspects of GI viably. The WBB could provide valuable clinical evaluation of balance function in OARF.

Caching Joint Shortcut Routing to Improve Quality of Service for Information-Centric Networking.

PubMed

Huang, Baixiang; Liu, Anfeng; Zhang, Chengyuan; Xiong, Naixue; Zeng, Zhiwen; Cai, Zhiping

2018-05-29

Hundreds of thousands of ubiquitous sensing (US) devices have provided an enormous number of data for Information-Centric Networking (ICN), which is an emerging network architecture that has the potential to solve a great variety of issues faced by the traditional network. A Caching Joint Shortcut Routing (CJSR) scheme is proposed in this paper to improve the Quality of service (QoS) for ICN. The CJSR scheme mainly has two innovations which are different from other in-network caching schemes: (1) Two routing shortcuts are set up to reduce the length of routing paths. Because of some inconvenient transmission processes, the routing paths of previous schemes are prolonged, and users can only request data from Data Centers (DCs) until the data have been uploaded from Data Producers (DPs) to DCs. Hence, the first kind of shortcut is built from DPs to users directly. This shortcut could release the burden of whole network and reduce delay. Moreover, in the second shortcut routing method, a Content Router (CR) which could yield shorter length of uploading routing path from DPs to DCs is chosen, and then data packets are uploaded through this chosen CR. In this method, the uploading path shares some segments with the pre-caching path, thus the overall length of routing paths is reduced. (2) The second innovation of the CJSR scheme is that a cooperative pre-caching mechanism is proposed so that QoS could have a further increase. Besides being used in downloading routing, the pre-caching mechanism can also be used when data packets are uploaded towards DCs. Combining uploading and downloading pre-caching, the cooperative pre-caching mechanism exhibits high performance in different situations. Furthermore, to address the scarcity of storage size, an algorithm that could make use of storage from idle CRs is proposed. After comparing the proposed scheme with five existing schemes via simulations, experiments results reveal that the CJSR scheme could reduce the total number of processed interest packets by 54.8%, enhance the cache hits of each CR and reduce the number of total hop counts by 51.6% and cut down the length of routing path for users to obtain their interested data by 28.6⁻85.7% compared with the traditional NDN scheme. Moreover, the length of uploading routing path could be decreased by 8.3⁻33.3%.

Safe Maritime Autonomous Path Planning in a High Sea State

NASA Technical Reports Server (NTRS)

Ono, Masahiro; Quadrelli, Marco; Huntsberger, Terrance L.

2014-01-01

This paper presents a path planning method for sea surface vehicles that prevents capsizing and bow-diving in a high sea-state. A key idea is to use response amplitude operators (RAOs) or, in control terminology, the transfer functions from a sea state to a vessel's motion, in order to find a set of speeds and headings that results in excessive pitch and roll oscillations. This information is translated to arithmetic constraints on the ship's velocity, which are passed to a model predictive control (MPC)-based path planner to find a safe and optimal path that achieves specified goals. An obstacle avoidance capability is also added to the path planner. The proposed method is demonstrated by simulations.

Are Tornadoes Getting Stronger?

NASA Astrophysics Data System (ADS)

Elsner, J.; Jagger, T.

2013-12-01

A cumulative logistic model for tornado damage category is developed and examined. Damage path length and width are significantly correlated to the odds of a tornado receiving the next highest damage category. Given values for the cube root of path length and square root of path width, the model predicts a probability for each category. The length and width coefficients are insensitive to the switch to the Enhanced Fujita (EF) scale and to distance from nearest city although these variables are statistically significant in the model. The width coefficient is sensitive to whether or not the tornado caused at least one fatality. This is likely due to the fact that the dimensions and characteristics of the damage path for such events are always based on ground surveys. The model predicted probabilities across the categories are then multiplied by the center wind speed from the categorical EF scale to obtain an estimate of the highest tornado wind speed on a continuous scale in units of meters per second. The estimated wind speeds correlate at a level of .82 (.46, .95) [95% confidence interval] to wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. More work needs to be done to understand the upward trends in path length and width. The increases lead to an apparent increase in tornado intensity across all EF categories.

1984 Ivanovo tornado outbreak: Determination of actual tornado tracks with satellite data

NASA Astrophysics Data System (ADS)

Chernokulsky, Alexander; Shikhov, Andrey

2018-07-01

The 1984 Ivanovo tornado outbreak is one of the most fatal tornado events in Europe with previously unspecified tornado track characteristics. In this paper, we used Landsat images to discover tornado-induced forest disturbances and restore actual characteristics of tornadoes during the outbreak. We defined boundaries of tornado-induced windthrows by visual comparison of satellite images and specified them with Normalized Difference Infrared Index. We confirmed the occurrence of eight tornadoes during the outbreak and determined their location, path width and length. Other tornadoes occurrence during the outbreak was discussed. Fujita-scale intensity of confirmed tornadoes was estimated based on the related literature corpus including previously omitted sources. In addition, information on tornado path lengths and widths was used to estimate minimal tornado intensity for those tornadoes that passed no settlements. In total, the Ivanovo outbreak includes 8-13 tornadoes with F-scale rating mean ranges from 1.8-2.5 and has adjusted Fujita length around 540 km, which makes the outbreak one the strongest in Europe and places it within the upper quartile of U.S. outbreaks. Characteristics of certain tornadoes within the Ivanovo outbreak are exceptional for Russia. The widest tornado path during the Ivanovo outbreak is 1740 m; the longest is from 81.5-85.9 km. With the example of the Ivanovo outbreak, we showed that existing databases on historical Russian tornadoes tend to overestimate tornado path length (for very long tornadoes) and underestimate maximum tornado path width.

Round-Trip System Available to Measure Path Length Variation in Korea VLBI System for Geodesy

NASA Technical Reports Server (NTRS)

Oh, Hongjong; Kondo, Tetsuro; Lee, Jinoo; Kim, Tuhwan; Kim, Myungho; Kim, Suchul; Park, Jinsik; Ju, Hyunhee

2010-01-01

The construction project of Korea Geodetic VLBI officially started in October 2008. The construction of all systems will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room with an H-maser frequency standard is located in a building separated from the antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with reduction of the effect of path length variations. KVG s round-trip system is designed not only to use either metal or optical fiber cables, but also to measure path length variations directly. We present this unique round trip system for KVG.

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

NASA Astrophysics Data System (ADS)

Gordon, James; Harman, Stephanie

2002-05-01

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

Video-Based Method of Quantifying Performance and Instrument Motion During Simulated Phonosurgery

PubMed Central

Conroy, Ellen; Surender, Ketan; Geng, Zhixian; Chen, Ting; Dailey, Seth; Jiang, Jack

2015-01-01

Objectives/Hypothesis To investigate the use of the Video-Based Phonomicrosurgery Instrument Tracking System to collect instrument position data during simulated phonomicrosurgery and calculate motion metrics using these data. We used this system to determine if novice subject motion metrics improved over 1 week of training. Study Design Prospective cohort study. Methods Ten subjects performed simulated surgical tasks once per day for 5 days. Instrument position data were collected and used to compute motion metrics (path length, depth perception, and motion smoothness). Data were analyzed to determine if motion metrics improved with practice time. Task outcome was also determined each day, and relationships between task outcome and motion metrics were used to evaluate the validity of motion metrics as indicators of surgical performance. Results Significant decreases over time were observed for path length (P <.001), depth perception (P <.001), and task outcome (P <.001). No significant change was observed for motion smoothness. Significant relationships were observed between task outcome and path length (P <.001), depth perception (P <.001), and motion smoothness (P <.001). Conclusions Our system can estimate instrument trajectory and provide quantitative descriptions of surgical performance. It may be useful for evaluating phonomicrosurgery performance. Path length and depth perception may be particularly useful indicators. PMID:24737286

Phase-Shifted Laser Feedback Interferometry

NASA Technical Reports Server (NTRS)

Ovryn, Benjie

1999-01-01

Phase-shifted, laser feedback interferometry is a new diagnostic tool developed at the NASA Lewis Research Center under the Advanced Technology Development (ATD) Program directed by NASA Headquarters Microgravity Research Division. It combines the principles of phase-shifting interferometry (PSI) and laser-feedback interferometry (LFI) to produce an instrument that can quantify both optical path length changes and sample reflectivity variations. In a homogenous medium, the optical path length between two points is the product of the index of refraction and the geometric distance between the two points. LFI differs from other forms of interferometry by using the laser as both the source and the phase detector. In LFI, coherent feedback of the incident light either reflected directly from a surface or reflected after transmission through a region of interest will modulate the output intensity of the laser. The combination of PSI and LFI has produced a robust instrument, based on a low-power helium-neon (HeNe) gas laser, with a high dynamic range that can be used to measure either static or oscillatory changes of the optical path length. Small changes in optical path length are limited by the fraction of a fringe that can be measured; we can measure nonoscillatory changes with a root mean square (rms) error of the wavelength/1000 without averaging.

Far off-resonance laser frequency stabilization using multipass cells in Faraday rotation spectroscopy.

PubMed

Quan, Wei; Li, Yang; Li, Rujie; Shang, Huining; Fang, Zishan; Qin, Jie; Wan, Shuangai

2016-04-01

We propose a far off-resonance laser frequency stabilization method by using multipass cells in Rb Faraday rotation spectroscopy. Based on the detuning equation, if multipass cells with several meters optical path length are used in the conventional Faraday spectroscopy, the detuning of the lock point can be extended much further from the alkali metal resonance. A plate beam splitter was used to generate two different Faraday signals at the same time. The transmitted optical path length was L=50  mm and the reflected optical path length was 2L=100  mm. When the optical path length doubled, the detuning of the lock points moved further away from the atomic resonance. The temperature dependence of the detuning of the lock point was also analyzed. A temperature-insensitive lock point was found near resonance when the cell temperature was between 110°C and 130°C. We achieved an rms fluctuation of 0.9 MHz/23 h at a detuning of 0.5 GHz. A frequency drift of 16 MHz/h at a detuning of -5.6  GHz and 4 MHz/h at a detuning of -5.2  GHz were also obtained for the transmitted and reflected light Faraday signal.

Structural factoring approach for analyzing stochastic networks

NASA Technical Reports Server (NTRS)

Hayhurst, Kelly J.; Shier, Douglas R.

1991-01-01

The problem of finding the distribution of the shortest path length through a stochastic network is investigated. A general algorithm for determining the exact distribution of the shortest path length is developed based on the concept of conditional factoring, in which a directed, stochastic network is decomposed into an equivalent set of smaller, generally less complex subnetworks. Several network constructs are identified and exploited to reduce significantly the computational effort required to solve a network problem relative to complete enumeration. This algorithm can be applied to two important classes of stochastic path problems: determining the critical path distribution for acyclic networks and the exact two-terminal reliability for probabilistic networks. Computational experience with the algorithm was encouraging and allowed the exact solution of networks that have been previously analyzed only by approximation techniques.

Study of intermolecular interactions in binary mixtures of 2'-chloro-4-methoxy-3-nitro benzil in various solvents and at different concentrations by the measurement of acoustic properties.

PubMed

Nithya, G; Thanuja, B; Kanagam, Charles C

2013-01-01

Density (ρ), ultrasonic velocity (u), adiabatic compressibility (β), apparent molar volume (Ø), acoustic impedance (Z), intermolecular free length (L(f)), relative association (RA) of binary mixtures of 2'-chloro-4-methoxy-3-nitro benzil (abbreviated as 2CBe) in ethanol, acetonitrile, chloroform, dioxane and benzene were measured at different concentrations at 298 K. Several useful parameters such as excess density, excess ultrasonic velocity, excess adiabatic compressibility, excess apparent molar volume, excess acoustic impedance and excess intermolecular free length have been calculated. These parameters are used to explain the nature of intermolecular interactions taking place in the binary mixture. The above study is useful in understanding the solute--solvent interactions occurring in different concentrations at room temperature. Copyright © 2012 Elsevier B.V. All rights reserved.

Virtual hybrid test control of sinuous crack

NASA Astrophysics Data System (ADS)

Jailin, Clément; Carpiuc, Andreea; Kazymyrenko, Kyrylo; Poncelet, Martin; Leclerc, Hugo; Hild, François; Roux, Stéphane

2017-05-01

The present study aims at proposing a new generation of experimental protocol for analysing crack propagation in quasi brittle materials. The boundary conditions are controlled in real-time to conform to a predefined crack path. Servo-control is achieved through a full-field measurement technique to determine the pre-set fracture path and a simple predictor model based on linear elastic fracture mechanics to prescribe the boundary conditions on the fly so that the actual crack path follows at best the predefined trajectory. The final goal is to identify, for instance, non-local damage models involving internal lengths. The validation of this novel procedure is performed via a virtual test-case based on an enriched damage model with an internal length scale, a prior chosen sinusoidal crack path and a concrete sample. Notwithstanding the fact that the predictor model selected for monitoring the test is a highly simplified picture of the targeted constitutive law, the proposed protocol exhibits a much improved sensitivity to the sought parameters such as internal lengths as assessed from the comparison with other available experimental tests.

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

NASA Astrophysics Data System (ADS)

Yu, Jia; Gao, Qiang; Zhang, Zhiguo

2014-10-01

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

Roads at risk - traffic detours from debris flows in southern Norway

NASA Astrophysics Data System (ADS)

Meyer, N. K.; Schwanghart, W.; Korup, O.; Nadim, F.

2014-10-01

Globalization and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g., road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load expressed as vehicle kilometers because of debris-flow related road closures. We present two scenarios demonstrating the impact of debris flows on the road network, and quantify the associated path failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and northwestern part of the study area are associated with high link failure risk. Yet options for detours on major routes are manifold, and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying of speedy delivery of services and goods.

Roads at risk: traffic detours from debris flows in southern Norway

NASA Astrophysics Data System (ADS)

Meyer, N. K.; Schwanghart, W.; Korup, O.; Nadim, F.

2015-05-01

Globalisation and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g. road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load, expressed as vehicle kilometres, because of debris-flow-related road closures. We present two scenarios demonstrating the impact of debris flows on the road network and quantify the associated path-failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and north-western part of the study area are associated with high link-failure risk. Yet options for detours on major routes are manifold and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying on speedy delivery of services and goods.

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

NASA Astrophysics Data System (ADS)

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

2011-06-01

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 α -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.

In vivo Length Change Patterns of the Medial and Lateral Collateral Ligaments along the Flexion Path of the Knee

PubMed Central

Hosseini, Ali; Qi, Wei; Tsai, Tsung-Yuan; Liu, Yujie; Rubash, Harry; Li, Guoan

2014-01-01

Purpose The knowledge of the function of the collateral ligaments – i.e., superficial medial collateral ligament (sMCL), deep medial collateral ligament (dMCL) and lateral collateral ligament (LCL) – in the entire range of knee flexion is important for soft tissue balance during total knee arthroplasty. The objective of this study was to investigate the length changes of different portions (anterior, middle and posterior) of the sMCL, dMCL and LCL during in vivo weightbearing flexion from full extension to maximal knee flexion. Methods Using a dual fluoroscopic imaging system eight healthy knees were imaged while performing a lunge from full extension to maximal flexion. The length changes of each portion of the collateral ligaments were measured along the flexion path of the knee. Results All anterior portions of the collateral ligaments were shown to have increasing length with flexion except that of the sMCL which showed a reduction in length at high flexion. The middle portions showed minimal change in lengths except that of the sMCL which showed a consistent reduction in length with flexion. All posterior portions showed reduction in lengths with flexion. Conclusions These data indicated that every portion of the ligaments may play important roles in knee stability at different knee flexion range. The soft tissue releasing during TKA may need to consider the function of the ligament portions along the entire flexion path including maximum flexion. PMID:25239504

Slant Path Low Visibility Atmospheric Conditions.

DTIC Science & Technology

1980-09-01

precipitation rate ; humidity; aerosol concentration; Particle spectrum; local aeiosol inhomogeneities; air * -Q.!ZIBS’IRACT: A slant path for...test path , of a length over which infrared transmissometer measurements can be made that are in a magnitude range permitting accurate measurements under...and therefore do not accurately relate to absolute transmissivity. A path which is too long will result in transmission measurements which are very low

A new method for photon transport in Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Sato, T.; Ogawa, K.

1999-12-01

Monte Carlo methods are used to evaluate data methods such as scatter and attenuation compensation in single photon emission CT (SPECT), treatment planning in radiation therapy, and in many industrial applications. In Monte Carlo simulation, photon transport requires calculating the distance from the location of the emitted photon to the nearest boundary of each uniform attenuating medium along its path of travel, and comparing this distance with the length of its path generated at emission. Here, the authors propose a new method that omits the calculation of the location of the exit point of the photon from each voxel and of the distance between the exit point and the original position. The method only checks the medium of each voxel along the photon's path. If the medium differs from that in the voxel from which the photon was emitted, the authors calculate the location of the entry point in the voxel, and the length of the path is compared with the mean free path length generated by a random number. Simulations using the MCAT phantom show that the ratios of the calculation time were 1.0 for the voxel-based method, and 0.51 for the proposed method with a 256/spl times/256/spl times/256 matrix image, thereby confirming the effectiveness of the algorithm.

Tornado Intensity Estimated from Damage Path Dimensions

PubMed Central

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

2014-01-01

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

Tornado intensity estimated from damage path dimensions.

PubMed

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

2014-01-01

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

A Virtual Water Maze Revisited: Two-Year Changes in Navigation Performance and their Neural Correlates in Healthy Adults

PubMed Central

Daugherty, Ana M.; Raz, Naftali

2016-01-01

Age-related declines in spatial navigation are associated with deficits in procedural and episodic memory and deterioration of their neural substrates. For the lack of longitudinal evidence, the pace and magnitude of these declines and their neural mediators remain unclear. Here we examined virtual navigation in healthy adults (N=213, age 18–77 years) tested twice, two years apart, with complementary indices of navigation performance (path length and complexity) measured over six learning trials at each occasion. Slopes of skill acquisition curves and longitudinal change therein were estimated in structural equation modeling, together with change in regional brain volumes and iron content (R2* relaxometry). Although performance on the first trial did not differ between occasions separated by two years, the slope of path length improvement over trials was shallower and end-of-session performance worse at follow-up. Advanced age, higher pulse pressure, smaller cerebellar and caudate volumes, and greater caudate iron content were associated with longer search paths, i.e. poorer navigation performance. In contrast, path complexity diminished faster over trials at follow-up, albeit less so in older adults. Improvement in path complexity after two years was predicted by lower baseline hippocampal iron content and larger parahippocampal volume. Thus, navigation path length behaves as an index of perceptual-motor skill that is vulnerable to age-related decline, whereas path complexity may reflect cognitive mapping in episodic memory that improves with repeated testing, although not enough to overcome age-related deficits. PMID:27659539

A virtual water maze revisited: Two-year changes in navigation performance and their neural correlates in healthy adults.

PubMed

Daugherty, Ana M; Raz, Naftali

2017-02-01

Age-related declines in spatial navigation are associated with deficits in procedural and episodic memory and deterioration of their neural substrates. For the lack of longitudinal evidence, the pace and magnitude of these declines and their neural mediators remain unclear. Here we examined virtual navigation in healthy adults (N=213, age 18-77 years) tested twice, two years apart, with complementary indices of navigation performance (path length and complexity) measured over six learning trials at each occasion. Slopes of skill acquisition curves and longitudinal change therein were estimated in structural equation modeling, together with change in regional brain volumes and iron content (R2* relaxometry). Although performance on the first trial did not differ between occasions separated by two years, the slope of path length improvement over trials was shallower and end-of-session performance worse at follow-up. Advanced age, higher pulse pressure, smaller cerebellar and caudate volumes, and greater caudate iron content were associated with longer search paths, i.e. poorer navigation performance. In contrast, path complexity diminished faster over trials at follow-up, albeit less so in older adults. Improvement in path complexity after two years was predicted by lower baseline hippocampal iron content and larger parahippocampal volume. Thus, navigation path length behaves as an index of perceptual-motor skill that is vulnerable to age-related decline, whereas path complexity may reflect cognitive mapping in episodic memory that improves with repeated testing, although not enough to overcome age-related deficits. Copyright © 2016 Elsevier Inc. All rights reserved.

Length oscillation mimicking periodic individual deep inspirations during tidal breathing attenuates force recovery and adaptation in airway smooth muscle.

PubMed

Raqeeb, Abdul; Solomon, Dennis; Paré, Peter D; Seow, Chun Y

2010-11-01

Airway smooth muscle (ASM) is able to generate maximal force under static conditions, and this isometric force can be maintained over a large length range due to length adaptation. The increased force at short muscle length could lead to excessive narrowing of the airways. Prolonged exposure of ASM to submaximal stimuli also increases the muscle's ability to generate force in a process called force adaptation. To date, the effects of length and force adaptation have only been demonstrated under static conditions. In the mechanically dynamic environment of the lung, ASM is constantly subjected to periodic stretches by the parenchyma due to tidal breathing and deep inspiration. It is not known whether force recovery due to muscle adaptation to a static environment could occur in a dynamic environment. In this study the effect of length oscillation mimicking tidal breathing and deep inspiration was examined. Force recovery after a length change was attenuated in the presence of length oscillation, except at very short lengths. Force adaptation was abolished by length oscillation. We conclude that in a healthy lung (with intact airway-parenchymal tethering) where airways are not allowed to narrow excessively, large stretches (associated with deep inspiration) may prevent the ability of the muscle to generate maximal force that would occur under static conditions irrespective of changes in mean length; mechanical perturbation on ASM due to tidal breathing and deep inspiration, therefore, is the first line of defense against excessive bronchoconstriction that may result from static length and force adaptation.

Effect of repetitive pecking at working length for glide path preparation using G-file.

PubMed

Ha, Jung-Hong; Jeon, Hyo-Jin; Abed, Rashid El; Chang, Seok-Woo; Kim, Sung-Kyo; Kim, Hyeon-Cheol

2015-05-01

Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. The G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05). The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05). Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level.

Root canal anatomy preservation of WaveOne reciprocating files with or without glide path.

PubMed

Berutti, Elio; Paolino, Davide Salvatore; Chiandussi, Giorgio; Alovisi, Mario; Cantatore, Giuseppe; Castellucci, Arnaldo; Pasqualini, Damiano

2012-01-01

This study evaluated the influence of glide path on canal curvature and axis modification after instrumentation with WaveOne Primary reciprocating files. Thirty ISO 15, 0.02 taper Endo Training Blocks were used. In group 1, glide path was created with PathFile 1, 2, and 3 at working length, whereas in group 2, glide path was not performed. In both groups, canals were shaped with WaveOne Primary reciprocating files at working length. Preinstrumentation and postinstrumentation digital images were superimposed and processed with Matlab r2010b software to analyze the curvature radius ratio (CRr) and the relative axis error (rAe), representing canal curvature modification. Data were analyzed with 1-way balanced analyses of variance at 2 levels (P < .05). Glide path was found to be extremely significant for both CRr parameter (F = 9.59; df = 1; P = .004) and rAe parameter (F = 13.55; df = 1; P = .001). Canal modifications seem to be significantly reduced when previous glide path is performed by using the new WaveOne nickel-titanium single-file system. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Path optimization with limited sensing ability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Sung Ha, E-mail: kang@math.gatech.edu; Kim, Seong Jun, E-mail: skim396@math.gatech.edu; Zhou, Haomin, E-mail: hmzhou@math.gatech.edu

2015-10-15

We propose a computational strategy to find the optimal path for a mobile sensor with limited coverage to traverse a cluttered region. The goal is to find one of the shortest feasible paths to achieve the complete scan of the environment. We pose the problem in the level set framework, and first consider a related question of placing multiple stationary sensors to obtain the full surveillance of the environment. By connecting the stationary locations using the nearest neighbor strategy, we form the initial guess for the path planning problem of the mobile sensor. Then the path is optimized by reducingmore » its length, via solving a system of ordinary differential equations (ODEs), while maintaining the complete scan of the environment. Furthermore, we use intermittent diffusion, which converts the ODEs into stochastic differential equations (SDEs), to find an optimal path whose length is globally minimal. To improve the computation efficiency, we introduce two techniques, one to remove redundant connecting points to reduce the dimension of the system, and the other to deal with the entangled path so the solution can escape the local traps. Numerical examples are shown to illustrate the effectiveness of the proposed method.« less

Slant Path Low Visibility Atmospheric Conditions.

DTIC Science & Technology

1980-09-01

situation. a) An optical propagation slant test path , of a length over which infrared transmissometer measurements can be made that are in a magnitude...transmission measure - ments which are close to 100% and therefore do not accurately relate to absolute transmissivity. A path which is too long will result in...is available for measurement of backscatter cross section along the chosen transmissometer path . 3. Rough Cross Cut of the Works unde Contract in

On the optical path length in refracting media

NASA Astrophysics Data System (ADS)

Hasbun, Javier E.

2018-04-01

The path light follows as it travels through a substance depends on the substance's index of refraction. This path is commonly known as the optical path length (OPL). In geometrical optics, the laws of reflection and refraction are simple examples for understanding the path of light travel from source to detector for constant values of the traveled substances' refraction indices. In more complicated situations, the Euler equation can be quite useful and quite important in optics courses. Here, the well-known Euler differential equation (EDE) is used to obtain the OPL for several index of refraction models. For pedagogical completeness, the OPL is also obtained through a modified Monte Carlo (MC) method, versus which the various results obtained through the EDE are compared. The examples developed should be important in projects involving undergraduate as well as graduate students in an introductory optics course. A simple matlab script (program) is included that can be modified by students who wish to pursue the subject further.

Automatic cell identification and visualization using digital holographic microscopy with head mounted augmented reality devices.

PubMed

O'Connor, Timothy; Rawat, Siddharth; Markman, Adam; Javidi, Bahram

2018-03-01

We propose a compact imaging system that integrates an augmented reality head mounted device with digital holographic microscopy for automated cell identification and visualization. A shearing interferometer is used to produce holograms of biological cells, which are recorded using customized smart glasses containing an external camera. After image acquisition, segmentation is performed to isolate regions of interest containing biological cells in the field-of-view, followed by digital reconstruction of the cells, which is used to generate a three-dimensional (3D) pseudocolor optical path length profile. Morphological features are extracted from the cell's optical path length map, including mean optical path length, coefficient of variation, optical volume, projected area, projected area to optical volume ratio, cell skewness, and cell kurtosis. Classification is performed using the random forest classifier, support vector machines, and K-nearest neighbor, and the results are compared. Finally, the augmented reality device displays the cell's pseudocolor 3D rendering of its optical path length profile, extracted features, and the identified cell's type or class. The proposed system could allow a healthcare worker to quickly visualize cells using augmented reality smart glasses and extract the relevant information for rapid diagnosis. To the best of our knowledge, this is the first report on the integration of digital holographic microscopy with augmented reality devices for automated cell identification and visualization.

High channel density wavelength division multiplexer with defined diffracting means positioning

DOEpatents

Jannson, Tomasz P.; Jannson, Joanna L.; Yeung, Peter C.

1990-01-01

A wavelength division multiplexer/demultiplexer having optical path lengths between a fiber array and a Fourier transform lens, and between a dispersion grating and the lens equal to the focal length of the lens. The optical path lengths reduce losses due to angular acceptance mismatch in the multiplexer. Close orientation of the fiber array about the optical axis and the use of a holographic dispersion grating reduces other losses in the system. Multi-exposure holographic dispersion gratings enable the multiplexer/demultiplexer for extremely broad-band simultaneous transmission and reflection operation. Individual Bragg plane sets recorded in the grating are dedicated to and operate efficiently on discrete wavelength ranges.

Tolman lengths and rigidity constants of multicomponent fluids: Fundamental theory and numerical examples

NASA Astrophysics Data System (ADS)

Aasen, Ailo; Blokhuis, Edgar M.; Wilhelmsen, Øivind

2018-05-01

The curvature dependence of the surface tension can be described by the Tolman length (first-order correction) and the rigidity constants (second-order corrections) through the Helfrich expansion. We present and explain the general theory for this dependence for multicomponent fluids and calculate the Tolman length and rigidity constants for a hexane-heptane mixture by use of square gradient theory. We show that the Tolman length of multicomponent fluids is independent of the choice of dividing surface and present simple formulae that capture the change in the rigidity constants for different choices of dividing surface. For multicomponent fluids, the Tolman length, the rigidity constants, and the accuracy of the Helfrich expansion depend on the choice of path in composition and pressure space along which droplets and bubbles are considered. For the hexane-heptane mixture, we find that the most accurate choice of path is the direction of constant liquid-phase composition. For this path, the Tolman length and rigidity constants are nearly linear in the mole fraction of the liquid phase, and the Helfrich expansion represents the surface tension of hexane-heptane droplets and bubbles within 0.1% down to radii of 3 nm. The presented framework is applicable to a wide range of fluid mixtures and can be used to accurately represent the surface tension of nanoscopic bubbles and droplets.

Knee, Shoulder, and Fundamentals of Arthroscopic Surgery Training: Validation of a Virtual Arthroscopy Simulator.

PubMed

Tofte, Josef N; Westerlind, Brian O; Martin, Kevin D; Guetschow, Brian L; Uribe-Echevarria, Bastián; Rungprai, Chamnanni; Phisitkul, Phinit

2017-03-01

To validate the knee, shoulder, and virtual Fundamentals of Arthroscopic Training (FAST) modules on a virtual arthroscopy simulator via correlations with arthroscopy case experience and postgraduate year. Orthopaedic residents and faculty from one institution performed a standardized sequence of knee, shoulder, and FAST modules to evaluate baseline arthroscopy skills. Total operation time, camera path length, and composite total score (metric derived from multiple simulator measurements) were compared with case experience and postgraduate level. Values reported are Pearson r; alpha = 0.05. 35 orthopaedic residents (6 per postgraduate year), 2 fellows, and 3 faculty members (2 sports, 1 foot and ankle), including 30 male and 5 female residents, were voluntarily enrolled March to June 2015. Knee: training year correlated significantly with year-averaged knee composite score, r = 0.92, P = .004, 95% confidence interval (CI) = 0.84, 0.96; operation time, r = -0.92, P = .004, 95% CI = -0.96, -0.84; and camera path length, r = -0.97, P = .0004, 95% CI = -0.98, -0.93. Knee arthroscopy case experience correlated significantly with composite score, r = 0.58, P = .0008, 95% CI = 0.27, 0.77; operation time, r = -0.54, P = .002, 95% CI = -0.75, -0.22; and camera path length, r = -0.62, P = .0003, 95% CI = -0.8, -0.33. Shoulder: training year correlated strongly with average shoulder composite score, r = 0.90, P = .006, 95% CI = 0.81, 0.95; operation time, r = -0.94, P = .001, 95% CI = -0.97, -0.89; and camera path length, r = -0.89, P = .007, 95% CI = -0.95, -0.80. Shoulder arthroscopy case experience correlated significantly with average composite score, r = 0.52, P = .003, 95% CI = 0.2, 0.74; strongly with operation time, r = -0.62, P = .0002, 95% CI = -0.8, -0.33; and camera path length, r = -0.37, P = .044, 95% CI = -0.64, -0.01, by training year. FAST: training year correlated significantly with 3 combined FAST activity average composite scores, r = 0.81, P = .0279, 95% CI = 0.65, 0.90; operation times, r = -0.86, P = .012, 95% CI = -0.93, -0.74; and camera path lengths, r = -0.85, P = .015, 95% CI = -0.92, -0.72. Total arthroscopy cases performed did not correlate significantly with overall FAST performance. We found significant correlations between both training year and knee and shoulder arthroscopy experience when compared with performance as measured by composite score, camera path length, and operation time during a simulated diagnostic knee and shoulder arthroscopy, respectively. Three FAST activities demonstrated significant correlations with training year but not arthroscopy case experience as measured by composite score, camera path length, and operation time. We attempt to validate an arthroscopy simulator that could be used to supplement arthroscopy skills training for orthopaedic residents. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Validity and reliability of balance assessment software using the Nintendo Wii balance board: usability and validation

PubMed Central

2014-01-01

Background A balance test provides important information such as the standard to judge an individual’s functional recovery or make the prediction of falls. The development of a tool for a balance test that is inexpensive and widely available is needed, especially in clinical settings. The Wii Balance Board (WBB) is designed to test balance, but there is little software used in balance tests, and there are few studies on reliability and validity. Thus, we developed a balance assessment software using the Nintendo Wii Balance Board, investigated its reliability and validity, and compared it with a laboratory-grade force platform. Methods Twenty healthy adults participated in our study. The participants participated in the test for inter-rater reliability, intra-rater reliability, and concurrent validity. The tests were performed with balance assessment software using the Nintendo Wii balance board and a laboratory-grade force platform. Data such as Center of Pressure (COP) path length and COP velocity were acquired from the assessment systems. The inter-rater reliability, the intra-rater reliability, and concurrent validity were analyzed by an intraclass correlation coefficient (ICC) value and a standard error of measurement (SEM). Results The inter-rater reliability (ICC: 0.89-0.79, SEM in path length: 7.14-1.90, SEM in velocity: 0.74-0.07), intra-rater reliability (ICC: 0.92-0.70, SEM in path length: 7.59-2.04, SEM in velocity: 0.80-0.07), and concurrent validity (ICC: 0.87-0.73, SEM in path length: 5.94-0.32, SEM in velocity: 0.62-0.08) were high in terms of COP path length and COP velocity. Conclusion The balance assessment software incorporating the Nintendo Wii balance board was used in our study and was found to be a reliable assessment device. In clinical settings, the device can be remarkably inexpensive, portable, and convenient for the balance assessment. PMID:24912769

Validity and reliability of balance assessment software using the Nintendo Wii balance board: usability and validation.

PubMed

Park, Dae-Sung; Lee, GyuChang

2014-06-10

A balance test provides important information such as the standard to judge an individual's functional recovery or make the prediction of falls. The development of a tool for a balance test that is inexpensive and widely available is needed, especially in clinical settings. The Wii Balance Board (WBB) is designed to test balance, but there is little software used in balance tests, and there are few studies on reliability and validity. Thus, we developed a balance assessment software using the Nintendo Wii Balance Board, investigated its reliability and validity, and compared it with a laboratory-grade force platform. Twenty healthy adults participated in our study. The participants participated in the test for inter-rater reliability, intra-rater reliability, and concurrent validity. The tests were performed with balance assessment software using the Nintendo Wii balance board and a laboratory-grade force platform. Data such as Center of Pressure (COP) path length and COP velocity were acquired from the assessment systems. The inter-rater reliability, the intra-rater reliability, and concurrent validity were analyzed by an intraclass correlation coefficient (ICC) value and a standard error of measurement (SEM). The inter-rater reliability (ICC: 0.89-0.79, SEM in path length: 7.14-1.90, SEM in velocity: 0.74-0.07), intra-rater reliability (ICC: 0.92-0.70, SEM in path length: 7.59-2.04, SEM in velocity: 0.80-0.07), and concurrent validity (ICC: 0.87-0.73, SEM in path length: 5.94-0.32, SEM in velocity: 0.62-0.08) were high in terms of COP path length and COP velocity. The balance assessment software incorporating the Nintendo Wii balance board was used in our study and was found to be a reliable assessment device. In clinical settings, the device can be remarkably inexpensive, portable, and convenient for the balance assessment.

Risk-Hedged Approach for Re-Routing Air Traffic Under Weather Uncertainty

NASA Technical Reports Server (NTRS)

Sadovsky, Alexander V.; Bilimoria, Karl D.

2016-01-01

This presentation corresponds to: our paper explores a new risk-hedged approach for re-routing air traffic around forecast convective weather. In this work, flying through a more likely weather instantiation is considered to pose a higher level of risk. Current operational practice strategically plans re-routes to avoid only the most likely (highest risk) weather instantiation, and then tactically makes any necessary adjustments as the weather evolves. The risk-hedged approach strategically plans re-routes by minimizing the risk-adjusted path length, incorporating multiple possible weather instantiations with associated likelihoods (risks). The resulting model is transparent and is readily analyzed for realism and treated with well-understood shortest-path algorithms. Risk-hedged re-routes are computed for some example weather instantiations. The main result is that in some scenarios, relative to an operational-practice proxy solution, the risk-hedged solution provides the benefits of lower risk as well as shorter path length. In other scenarios, the benefits of the risk-hedged solution are ambiguous, because the solution is characterized by a tradeoff between risk and path length. The risk-hedged solution can be executed in those scenarios where it provides a clear benefit over current operational practice.

Laser Radar Through the Window (LRTW) Coordinate Correction Method

NASA Technical Reports Server (NTRS)

Hadjimichael, Theodore John (Inventor); Ohl, IV, Raymond George (Inventor); Hayden, Joseph Ethan (Inventor); Kubalak, David Albert (Inventor); Eegholm, Bente Hoffmann (Inventor); Telfer, Randal Crawford (Inventor); Coulter, Phillip (Inventor)

2015-01-01

A method for corrections of measurements of points of interests measured by beams of radiation propagating through stratified media including performance of ray-tracing of at least one ray lunched from a metrology instrument in a direction of an apparent point of interest, calculation a path length of the ray through stratified medium, and determination of coordinates of true position of the point interest using the at least one path length and the direction of propagation of the ray.

Measuring excess free energies of self-assembled membrane structures.

PubMed

Norizoe, Yuki; Daoulas, Kostas Ch; Müller, Marcus

2010-01-01

Using computer simulation of a solvent-free, coarse-grained model for amphiphilic membranes, we study the excess free energy of hourglass-shaped connections (i.e., stalks) between two apposed bilayer membranes. In order to calculate the free energy by simulation in the canonical ensemble, we reversibly transfer two apposed bilayers into a configuration with a stalk in three steps. First, we gradually replace the intermolecular interactions by an external, ordering field. The latter is chosen such that the structure of the non-interacting system in this field closely resembles the structure of the original, interacting system in the absence of the external field. The absence of structural changes along this path suggests that it is reversible; a fact which is confirmed by expanded-ensemble simulations. Second, the external, ordering field is changed as to transform the non-interacting system from the apposed bilayer structure to two-bilayers connected by a stalk. The final external field is chosen such that the structure of the non-interacting system resembles the structure of the stalk in the interacting system without a field. On the third branch of the transformation path, we reversibly replace the external, ordering field by non-bonded interactions. Using expanded-ensemble techniques, the free energy change along this reversible path can be obtained with an accuracy of 10(-3)k(B)T per molecule in the n VT-ensemble. Calculating the chemical potential, we obtain the free energy of a stalk in the grandcanonical ensemble, and employing semi-grandcanonical techniques, we calculate the change of the excess free energy upon altering the molecular architecture. This computational strategy can be applied to compute the free energy of self-assembled phases in lipid and copolymer systems, and the excess free energy of defects or interfaces.

A new approach to process control using Instability Index

NASA Astrophysics Data System (ADS)

Weintraub, Jeffrey; Warrick, Scott

2016-03-01

The merits of a robust Statistical Process Control (SPC) methodology have long been established. In response to the numerous SPC rule combinations, processes, and the high cost of containment, the Instability Index (ISTAB) is presented as a tool for managing these complexities. ISTAB focuses limited resources on key issues and provides a window into the stability of manufacturing operations. ISTAB takes advantage of the statistical nature of processes by comparing the observed average run length (OARL) to the expected run length (ARL), resulting in a gap value called the ISTAB index. The ISTAB index has three characteristic behaviors that are indicative of defects in an SPC instance. Case 1: The observed average run length is excessively long relative to expectation. ISTAB > 0 is indicating the possibility that the limits are too wide. Case 2: The observed average run length is consistent with expectation. ISTAB near zero is indicating that the process is stable. Case 3: The observed average run length is inordinately short relative to expectation. ISTAB < 0 is indicating that the limits are too tight, the process is unstable or both. The probability distribution of run length is the basis for establishing an ARL. We demonstrate that the geometric distribution is a good approximation to run length across a wide variety of rule sets. Excessively long run lengths are associated with one kind of defect in an SPC instance; inordinately short run lengths are associated with another. A sampling distribution is introduced as a way to quantify excessively long and inordinately short observed run lengths. This paper provides detailed guidance for action limits on these run lengths. ISTAB as a statistical method of review facilitates automated instability detection. This paper proposes a management system based on ISTAB as an enhancement to more traditional SPC approaches.

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

DOEpatents

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

1984-05-08

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

An improved global dynamic routing strategy for scale-free network with tunable clustering

NASA Astrophysics Data System (ADS)

Sun, Lina; Huang, Ning; Zhang, Yue; Bai, Yannan

2016-08-01

An efficient routing strategy can deliver packets quickly to improve the network capacity. Node congestion and transmission path length are inevitable real-time factors for a good routing strategy. Existing dynamic global routing strategies only consider the congestion of neighbor nodes and the shortest path, which ignores other key nodes’ congestion on the path. With the development of detection methods and techniques, global traffic information is readily available and important for the routing choice. Reasonable use of this information can effectively improve the network routing. So, an improved global dynamic routing strategy is proposed, which considers the congestion of all nodes on the shortest path and incorporates the waiting time of the most congested node into the path. We investigate the effectiveness of the proposed routing for scale-free network with different clustering coefficients. The shortest path routing strategy and the traffic awareness routing strategy only considering the waiting time of neighbor node are analyzed comparatively. Simulation results show that network capacity is greatly enhanced compared with the shortest path; congestion state increase is relatively slow compared with the traffic awareness routing strategy. Clustering coefficient increase will not only reduce the network throughput, but also result in transmission average path length increase for scale-free network with tunable clustering. The proposed routing is favorable to ease network congestion and network routing strategy design.

Iterative blip-summed path integral for quantum dynamics in strongly dissipative environments

NASA Astrophysics Data System (ADS)

Makri, Nancy

2017-04-01

The iterative decomposition of the blip-summed path integral [N. Makri, J. Chem. Phys. 141, 134117 (2014)] is described. The starting point is the expression of the reduced density matrix for a quantum system interacting with a harmonic dissipative bath in the form of a forward-backward path sum, where the effects of the bath enter through the Feynman-Vernon influence functional. The path sum is evaluated iteratively in time by propagating an array that stores blip configurations within the memory interval. Convergence with respect to the number of blips and the memory length yields numerically exact results which are free of statistical error. In situations of strongly dissipative, sluggish baths, the algorithm leads to a dramatic reduction of computational effort in comparison with iterative path integral methods that do not implement the blip decomposition. This gain in efficiency arises from (i) the rapid convergence of the blip series and (ii) circumventing the explicit enumeration of between-blip path segments, whose number grows exponentially with the memory length. Application to an asymmetric dissipative two-level system illustrates the rapid convergence of the algorithm even when the bath memory is extremely long.

Measurement of refractive index of photopolymer for holographic gratings

NASA Astrophysics Data System (ADS)

Watanabe, Eriko; Mizuno, Jun; Fujikawa, Chiemi; Kodate, Kashiko

2007-02-01

We have made attempts to measure directly the small-scale variation of optical path lengths in photopolymer samples. For those with uniform thickness, the measured quantity is supposed to be proportional to the refractive index of the photopolymer. The system is based on a Mach-Zehnder interferometer using phase-locking technique and measures the change in optical path length during the sample is scanned across the optical axis. The spatial resolution is estimated to be 2μm, which is limited by the sample thickness. The path length resolution is estimated to be 6nm, which corresponds to the change in refractive index less than 10 -3 for the sample of 10μm thick. The measurement results showed clearly that the refractive index of photopolymer is not simply proportional to the exposure energy, contrary to the conventional photosensitive materials such as silver halide emulsion and dichromated gelatine. They also revealed the refractive index fluctuation in uniformly exposed photopolymer sample, which explains the milky appearance that sometimes observed in thick samples.

Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings

DOE PAGES

Steiner, M. A.; Bunn, J. R.; Einhorn, J. R.; ...

2017-05-16

This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U–8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factorsmore » such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.« less

The GLC8 - A miniature low cost ring laser gyroscope

NASA Astrophysics Data System (ADS)

Godart, D.-F.; Peghaire, J.-P.

SAGEM is enlarging its family of ring laser gyros (RLG) which already includes a triangular 32-cm path-length gyro and a square 16-cm path-length gyro, in order to meet the increasing demand for low cost, medium accuracy strap-down inertial measurement units for applications such as short- and medium-range tactical missiles as well as aided navigation systems for aircrafts and land vehicles. Based on the experience acquired in the past 13 years in the RLG field, and especially in mirror manufacturing, SAGEM developed the GLC8 which has a square 8-cm path length cavity, central piezoelectric dither. It incorporates two cathodes, a single anode, and is technologically designed to minimize production-costs while optimizing the performance to global device size ratio. This gyro is characterized by a bias and a scale-factor stability respectively better than 0.5 deg/h and 100 ppm (1 sigma), and has an operating lifetime compatible with the most demanding relevant applications and a high robustness to mechanical environments.

High channel density wavelength division multiplexer with defined diffracting means positioning

DOEpatents

Jannson, T.P.; Jannson, J.L.; Yeung, P.C.

1990-05-15

A wavelength division multiplexer/demultiplexer is disclosed having optical path lengths between a fiber array and a Fourier transform lens, and between a dispersion grating and the lens equal to the focal length of the lens. The optical path lengths reduce losses due to angular acceptance mismatch in the multiplexer. Close orientation of the fiber array about the optical axis and the use of a holographic dispersion grating reduces other losses in the system. Multi-exposure holographic dispersion gratings enable the multiplexer/demultiplexer for extremely broad-band simultaneous transmission and reflection operation. Individual Bragg plane sets recorded in the grating are dedicated to and operate efficiently on discrete wavelength ranges. 11 figs.

The Millimeter Sky Transparency Imager (MiSTI)

NASA Astrophysics Data System (ADS)

Tamura, Yoichi; Kawabe, Ryohei; Kohno, Kotaro; Fukuhara, Masayuki; Momose, Munetake; Ezawa, Hajime; Kuboi, Akihito; Sekiguchi, Tomohiko; Kamazaki, Takeshi; Vila-Vilaró, Baltasar; Nakagawa, Yuki; Okada, Norio

2011-04-01

The Millimeter Sky Transparency Imager (MiSTI) is a small millimeter-wave scanning telescope with a 25-cm diameter dish operating at 183 GHz. MiSTI is installed at Atacama, Chile, and it measures emission from atmospheric water vapor and its fluctuations to estimate atmospheric absorption in the millimeter to submillimeter range. MiSTI observes the water vapor distribution at a spatial resolution of 0.°5, and it is sensitive enough to detect an excess path length of lesssim0.05 mm for an integration time of 1 s. By comparing the MiSTI measurements with those by a 220 GHz tipper, we validated that the 183 GHz measurements of MiSTI are correct, down to the level of any residual systematic errors in the 220 GHz measurements. Since 2008, MiSTI has provided real-time (every 1 hr) monitoring of the all-sky opacity distribution and atmospheric transmission curves in the (sub)millimeter through the internet, allowing us to know the (sub)millimeter sky conditions at Atacama.

Path integration in tactile perception of shapes.

PubMed

Moscatelli, Alessandro; Naceri, Abdeldjallil; Ernst, Marc O

2014-11-01

Whenever we move the hand across a surface, tactile signals provide information about the relative velocity between the skin and the surface. If the system were able to integrate the tactile velocity information over time, cutaneous touch may provide an estimate of the relative displacement between the hand and the surface. Here, we asked whether humans are able to form a reliable representation of the motion path from tactile cues only, integrating motion information over time. In order to address this issue, we conducted three experiments using tactile motion and asked participants (1) to estimate the length of a simulated triangle, (2) to reproduce the shape of a simulated triangular path, and (3) to estimate the angle between two-line segments. Participants were able to accurately indicate the length of the path, whereas the perceived direction was affected by a direction bias (inward bias). The response pattern was thus qualitatively similar to the ones reported in classical path integration studies involving locomotion. However, we explain the directional biases as the result of a tactile motion aftereffect. Copyright © 2014 Elsevier B.V. All rights reserved.

WE-EF-303-10: Single- Detector Proton Radiography as a Portal Imaging Equivalent for Proton Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doolan, P; Bentefour, E; Testa, M

2015-06-15

Purpose: In proton therapy, patient alignment is of critical importance due to the sensitivity of the proton range to tissue heterogeneities. Traditionally proton radiography is used for verification of the water-equivalent path length (WEPL), which dictates the depth protons reach. In this work we propose its use for alignment. Additionally, many new proton centers have cone-beam computed tomography in place of beamline X-ray imaging and so proton radiography offers a unique patient alignment verification similar to portal imaging in photon therapy. Method: Proton radiographs of a CIRS head phantom were acquired using the Beam Imaging System (BIS) (IBA, Louvain-la-Neuve) inmore » a horizontal beamline. A scattered beam was produced using a small, dedicated, range modulator (RM) wheel fabricated out of aluminum. The RM wheel was rotated slowly (20 sec/rev) using a stepper motor to compensate for the frame rate of the BIS (120 ms). Dose rate functions (DRFs) over two RM wheel rotations were acquired. Calibration was made with known thicknesses of homogeneous solid water. For each pixel the time width, skewness and kurtosis of the DRFs were computed. The time width was used to compute the object WEPL. In the heterogeneous phantom, the excess skewness and excess kurtosis (i.e. difference from homogeneous cases) were computed and assessed for suitability for patient set up. Results: The technique allowed for the simultaneous production of images that can be used for WEPL verification, showing few internal details, and excess skewness and kurtosis images that can be used for soft tissue alignment. These latter images highlight areas where range mixing has occurred, correlating with phantom heterogeneities. Conclusion: The excess skewness and kurtosis images contain details that are not visible in the WET images. These images, unique to the time-resolved proton radiographic method, could be used for patient set up according to soft tissues.« less

Air Vehicle Path Planning

DTIC Science & Technology

2001-12-13

6-18 6.13. Apollonius Circle for the Case of Two Unequal Power Radars . . . 6-20 6.14. Solution Triangle...Voronoi edge is an Apollonius circle [32, 19]. In this section, we are concerned with the optimality of the Voronoi path for the two radar exposure...Comparison of Cost vs. Path Length for Constrained Trajectories Around and Between Two Radars 6-18 from the two radars is an Apollonius circle

Mass spectrometer with electron source for reducing space charge effects in sample beam

DOEpatents

Houk, Robert S.; Praphairaksit, Narong

2003-10-14

A mass spectrometer includes an ion source which generates a beam including positive ions, a sampling interface which extracts a portion of the beam from the ion source to form a sample beam that travels along a path and has an excess of positive ions over at least part of the path, thereby causing space charge effects to occur in the sample beam due to the excess of positive ions in the sample beam, an electron source which adds electrons to the sample beam to reduce space charge repulsion between the positive ions in the sample beam, thereby reducing the space charge effects in the sample beam and producing a sample beam having reduced space charge effects, and a mass analyzer which analyzes the sample beam having reduced space charge effects.

Computer-implemented remote sensing techniques for measuring coastal productivity and nutrient transport systems

NASA Technical Reports Server (NTRS)

Butera, M. K.

1981-01-01

An automatic technique has been developed to measure marsh plant production by inference from a species classification derived from Landsat MSS data. A separate computer technique has been developed to calculate the transport path length of detritus and nutrients from their point of origin in the marsh to the shoreline from Landsat data. A nutrient availability indicator, the ratio of production to transport path length, was derived for each marsh-identified Landsat cell. The use of a data base compatible with the Landsat format facilitated data handling and computations.

Non-invasive method of determining diastolic intracranial pressure

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Cantrell, Jr., John H. (Inventor); Hargens, Alan R. (Inventor)

2004-01-01

A method is presented for determining diastolic intracranial pressure (ICP) in a patient. A first change in the length of a path across the skull of the patient caused by a known change in ICP is measured and used to determine an elasticity constant for the patient. Next, a second change in the length of the path across the patient's skull occurring between systolic and diastolic portions of the patient's heartbeat is measured. The patient's diastolic ICP is a function of the elasticity constant and the second change.

VHF/UHF technique for the determination of the columnar electron contents of the plasmasphere and of the protonosphere using geostationary satellite transmission: Observations during magnetic storms

NASA Technical Reports Server (NTRS)

Almeida, O. G.

1972-01-01

Measurements of the total electron content of the plasmasphere up to geostationary heights were made using the beacon transmitters aboard the satellite ATS-3. The technique employed is a combination of the phase-path length difference and the Faraday rotation angle methods. Such a combination permits very accurate determination of the integration constant necessary to convert phase-path length difference data into information about the absolute value of the columnar content.

Quantitative impact of small angle forward scatter on whole blood oximetry using a Beer-Lambert absorbance model.

PubMed

LeBlanc, Serge Emile; Atanya, Monica; Burns, Kevin; Munger, Rejean

2011-04-21

It is well known that red blood cell scattering has an impact on whole blood oximetry as well as in vivo retinal oxygen saturation measurements. The goal of this study was to quantify the impact of small angle forward scatter on whole blood oximetry for scattering angles found in retinal oximetry light paths. Transmittance spectra of whole blood were measured in two different experimental setups: one that included small angle scatter in the transmitted signal and one that measured the transmitted signal only, at absorbance path lengths of 25, 50, 100, 250 and 500 µm. Oxygen saturation was determined by multiple linear regression in the 520-600 nm wavelength range and compared between path lengths and experimental setups. Mean calculated oxygen saturation differences between setups were greater than 10% at every absorbance path length. The deviations to the Beer-Lambert absorbance model had different spectral dependences between experimental setups, with the highest deviations found in the 520-540 nm range when scatter was added to the transmitted signal. These results are consistent with other models of forward scatter that predict different spectral dependences of the red blood cell scattering cross-section and haemoglobin extinction coefficients in this wavelength range.

Maternal Prepregnancy Body Mass Index and Gestational Weight Gain on Offspring Overweight in Early Infancy

PubMed Central

Li, Nan; Liu, Enqing; Guo, Jia; Pan, Lei; Li, Baojuan; Wang, Ping; Liu, Jin; Wang, Yue; Liu, Gongshu; Hu, Gang

2013-01-01

Objective The aim of the present study was to evaluate the association of maternal prepregnancy body mass index (BMI) and gestational weight gain (GWG) with anthropometry in the offspring from birth to 12 months old in Tianjin, China. Methods Between 2009 and 2011, health care records of 38,539 pregnant women had been collected, and their children had been measured body weight and length at birth, 3, 6, 9 and 12 months of age. The independent and joint associations of pre-pregnancy BMI and GWG based on the Institute of Medicine (IOM) guidelines with anthropometry in the offspring were examined using General Linear Model and Logistic Regression. Results Prepregnancy BMI and maternal GWG were positively associated with Z-scores for birth weight-for-gestational age, birth length-for-gestational age, and birth weight-for-length. Infants born to mothers with excessive GWG had the greatest changes in Z-scores for weight-for-age from birth to Month 3, and from Month 6 to Month 12, and the greatest changes in Z-scores for length-for-age from birth to months 3 and 12 compared with infants born to mothers with adequate GWG. Excessive GWG was associated with an increased risk of offspring overweight or obesity at 12 months old in all BMI categories except underweight. Conclusions Maternal prepregnancy overweight/obesity and excessive GWG were associated with greater weight gain and length gain of offspring in early infancy. Excessive GWG was associated with increased infancy overweight and obesity risk. PMID:24204979

Fast and accurate estimation of the covariance between pairwise maximum likelihood distances.

PubMed

Gil, Manuel

2014-01-01

Pairwise evolutionary distances are a model-based summary statistic for a set of molecular sequences. They represent the leaf-to-leaf path lengths of the underlying phylogenetic tree. Estimates of pairwise distances with overlapping paths covary because of shared mutation events. It is desirable to take these covariance structure into account to increase precision in any process that compares or combines distances. This paper introduces a fast estimator for the covariance of two pairwise maximum likelihood distances, estimated under general Markov models. The estimator is based on a conjecture (going back to Nei & Jin, 1989) which links the covariance to path lengths. It is proven here under a simple symmetric substitution model. A simulation shows that the estimator outperforms previously published ones in terms of the mean squared error.

Fast and accurate estimation of the covariance between pairwise maximum likelihood distances

PubMed Central

2014-01-01

Pairwise evolutionary distances are a model-based summary statistic for a set of molecular sequences. They represent the leaf-to-leaf path lengths of the underlying phylogenetic tree. Estimates of pairwise distances with overlapping paths covary because of shared mutation events. It is desirable to take these covariance structure into account to increase precision in any process that compares or combines distances. This paper introduces a fast estimator for the covariance of two pairwise maximum likelihood distances, estimated under general Markov models. The estimator is based on a conjecture (going back to Nei & Jin, 1989) which links the covariance to path lengths. It is proven here under a simple symmetric substitution model. A simulation shows that the estimator outperforms previously published ones in terms of the mean squared error. PMID:25279263

Path length differencing and energy conservation of the S[sub N] Boltzmann/Spencer-Lewis equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filippone, W.L.; Monahan, S.P.

It is shown that the S[sub N] Boltzmann/Spencer-Lewis equations conserve energy locally if and only if they satisfy particle balance and diamond differencing is used in path length. In contrast, the spatial differencing schemes have no bearing on the energy balance. Energy is conserved globally if it is conserved locally and the multigroup cross sections are energy conserving. Although the coupled electron-photon cross sections generated by CEPXS conserve particles and charge, they do not precisely conserve energy. It is demonstrated that these cross sections can be adjusted such that particles, charge, and energy are conserved. Finally, since a conventional negativemore » flux fixup destroys energy balance when applied to path legend, a modified fixup scheme that does not is presented.« less

Detection of silver nanoparticles in seawater at ppb levels using UV-visible spectrophotometry with long path cells.

PubMed

Lodeiro, Pablo; Achterberg, Eric P; El-Shahawi, Mohammad S

2017-03-01

Silver nanoparticles (AgNPs) are emerging contaminants that are difficult to detect in natural waters. UV-visible spectrophotometry is a simple technique that allows detection of AgNPs through analysis of their characteristic surface plasmon resonance band. The detection limit for nanoparticles using up to 10cm path length cuvettes with UV-visible spectrophotometry is in the 0.1-10ppm range. This detection limit is insufficiently low to observe AgNPs in natural environments. Here we show how the use of capillary cells with an optical path length up to 200cm, forms an excellent technique for rapid detection and quantification of non-aggregated AgNPs at ppb concentrations in complex natural matrices such as seawater. Copyright © 2016 Elsevier B.V. All rights reserved.

A link-adding strategy for transport efficiency of complex networks

NASA Astrophysics Data System (ADS)

Ma, Jinlong; Han, Weizhan; Guo, Qing; Wang, Zhenyong; Zhang, Shuai

2016-12-01

The transport efficiency is one of the critical parameters to evaluate the performance of a network. In this paper, we propose an improved efficient (IE) strategy to enhance the network transport efficiency of complex networks by adding a fraction of links to an existing network based on the node’s local degree centrality and the shortest path length. Simulation results show that the proposed strategy can bring better traffic capacity and shorter average shortest path length than the low-degree-first (LDF) strategy under the shortest path routing protocol. It is found that the proposed strategy is beneficial to the improvement of overall traffic handling and delivering ability of the network. This study can alleviate the congestion in networks, and is helpful to design and optimize realistic networks.

Path statistics, memory, and coarse-graining of continuous-time random walks on networks

PubMed Central

Kion-Crosby, Willow; Morozov, Alexandre V.

2015-01-01

Continuous-time random walks (CTRWs) on discrete state spaces, ranging from regular lattices to complex networks, are ubiquitous across physics, chemistry, and biology. Models with coarse-grained states (for example, those employed in studies of molecular kinetics) or spatial disorder can give rise to memory and non-exponential distributions of waiting times and first-passage statistics. However, existing methods for analyzing CTRWs on complex energy landscapes do not address these effects. Here we use statistical mechanics of the nonequilibrium path ensemble to characterize first-passage CTRWs on networks with arbitrary connectivity, energy landscape, and waiting time distributions. Our approach can be applied to calculating higher moments (beyond the mean) of path length, time, and action, as well as statistics of any conservative or non-conservative force along a path. For homogeneous networks, we derive exact relations between length and time moments, quantifying the validity of approximating a continuous-time process with its discrete-time projection. For more general models, we obtain recursion relations, reminiscent of transfer matrix and exact enumeration techniques, to efficiently calculate path statistics numerically. We have implemented our algorithm in PathMAN (Path Matrix Algorithm for Networks), a Python script that users can apply to their model of choice. We demonstrate the algorithm on a few representative examples which underscore the importance of non-exponential distributions, memory, and coarse-graining in CTRWs. PMID:26646868

49 CFR 38.29 - Interior circulation, handrails and stanchions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... length with front-door lifts or ramps, vertical stanchions immediately behind the driver shall either... of 22 feet in length, the minimum interior height along the path from the lift to the securement location shall be 68 inches. For vehicles of 22 feet in length or less, the minimum interior height from...

Physiological assessment and path coefficient analysis to improve evaluation of alfalfa autotoxicity.

PubMed

Chon, Sang-Uk; Nelson, C Jerry; Coutts, John H

2003-11-01

Reseeding of alfalfa is affected until autotoxic chemicals break down or are dispersed, often requiring a year or more. Bioassays of seed germination and early seedling growth, on agar medium in petri dishes, were conducted to evaluate autotoxic responses of 20 alfalfa germplasms to water-soluble extracts of alfalfa leaf tissue. Root length, 120 hr after placing imbibed seed on agar, was more sensitive to the autotoxin(s) than was hypocotyl length, germination speed, and final germination percentage. Path coefficient analyses showed variation in root length had 7-17 times more effect than variation in hypocotyl length in determining autotoxic effects on total seedling length. Although variations in seed size and germination rate were negatively associated (P < 0.05) with final root length, the autotoxin had little effect on these factors relative to that on root length. Germplasms in the control differed (P < 0.05) in root length, requiring tolerance to be evaluated as percent of control. Germplasms, as percent of control, differed significantly (P < 0.05) at extract concentrations of 1.0 and 4.0 g l(-1), but the range and LSD were more favorable for selection at 1.0 g l(-1). Root length is appropriate for genetic assessments of tolerance to the autotoxin when expressed as percent of control.

MEAN FREE PATH OF HOT ELECTRONS AND HOLES IN METALS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stuart, R.N.; Wooten, F.; Spicer, W.E.

1963-01-01

The mean free paths and attenuation lengths of hot electrons and holes in metals are calculated by Morte Cario methods. The results are compared with experimental results for electrons in Au,-Ag, Cu, and Pd and holes in Au. (T.F.H.)

HIGH SPEED KERR CELL FRAMING CAMERA

DOEpatents

Goss, W.C.; Gilley, L.F.

1964-01-01

The present invention relates to a high speed camera utilizing a Kerr cell shutter and a novel optical delay system having no moving parts. The camera can selectively photograph at least 6 frames within 9 x 10/sup -8/ seconds during any such time interval of an occurring event. The invention utilizes particularly an optical system which views and transmits 6 images of an event to a multi-channeled optical delay relay system. The delay relay system has optical paths of successively increased length in whole multiples of the first channel optical path length, into which optical paths the 6 images are transmitted. The successively delayed images are accepted from the exit of the delay relay system by an optical image focusing means, which in turn directs the images into a Kerr cell shutter disposed to intercept the image paths. A camera is disposed to simultaneously view and record the 6 images during a single exposure of the Kerr cell shutter. (AEC)

Beam combining and SBS suppression in white noise and pseudo-random modulated amplifiers

NASA Astrophysics Data System (ADS)

Anderson, Brian; Flores, Angel; Holten, Roger; Ehrenreich, Thomas; Dajani, Iyad

2015-03-01

White noise phase modulation (WNS) and pseudo-random binary sequence phase modulation (PRBS) are effective techniques for mitigation of nonlinear effects such as stimulated Brillouin scattering (SBS); thereby paving the way for higher power narrow linewidth fiber amplifiers. However, detailed studies comparing both coherent beam combination and the SBS suppression of these phase modulation schemes have not been reported. In this study an active fiber cutback experiment is performed comparing the enhancement factor of a PRBS and WNS broadened seed as a function of linewidth and fiber length. Furthermore, two WNS and PRBS modulated fiber lasers are coherently combined to measure and compare the fringe visibility and coherence length as a function of optical path length difference. Notably, the discrete frequency comb of PRBS modulation provides a beam combining re-coherence effect where the lasers periodically come back into phase. Significantly, this may reduce path length matching complexity in coherently combined fiber laser systems.

Kinetic simulations of gas breakdown in the dense plasma focus

NASA Astrophysics Data System (ADS)

Bennett, N.; Blasco, M.; Breeding, K.; DiPuccio, V.; Gall, B.; Garcia, M.; Gardner, S.; Gatling, J.; Hagen, E. C.; Luttman, A.; Meehan, B. T.; Molnar, S.; O'Brien, R.; Ormond, E.; Robbins, L.; Savage, M.; Sipe, N.; Welch, D. R.

2017-06-01

The first fully kinetic, collisional, and electromagnetic simulations of the breakdown phase of a MA-scale dense plasma focus are described and shown to agree with measured electrical characteristics, including breakdown time. In the model, avalanche ionization is driven by cathode electron emission, and this results in incomplete gas breakdown along the insulator. This reinforces the importance of the conditioning process that creates a metallic layer on the insulator surface. The simulations, nonetheless, help explain the relationship between the gas pressure, the insulator length, and the coaxial gap width. Previously, researchers noted three breakdown patterns related to pressure. Simulation and analytical results show that at low pressures, long ionization path lengths lead to volumetric breakdown, while high pressures lead to breakdown across the relatively small coaxial electrode gap. In an intermediate pressure regime, ionization path lengths are comparable to the insulator length which promotes ideal breakdown along the insulator surface.

Fast orthogonal transforms and generation of Brownian paths

PubMed Central

Leobacher, Gunther

2012-01-01

We present a number of fast constructions of discrete Brownian paths that can be used as alternatives to principal component analysis and Brownian bridge for stratified Monte Carlo and quasi-Monte Carlo. By fast we mean that a path of length n can be generated in O(nlog(n)) floating point operations. We highlight some of the connections between the different constructions and we provide some numerical examples. PMID:23471545

Automatic Alignment of Displacement-Measuring Interferometer

NASA Technical Reports Server (NTRS)

Halverson, Peter; Regehr, Martin; Spero, Robert; Alvarez-Salazar, Oscar; Loya, Frank; Logan, Jennifer

2006-01-01

A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error. On the basis of the geometrical optics of corner-cube reflectors, the length of the optical path can be shown to be L = L(sub 0)cos theta, where L(sub 0) is the distance between the corner points and theta is the misalignment angle. Therefore, the measurement error is given by DeltaL = L(sub 0)(cos theta - 1). In the usual case in which the misalignment is small, this error can be approximated as DeltaL approximately equal to -L(sub 0)theta sup 2/2. The control system (see figure) is implemented partly in hardware and partly in software. The control system includes three piezoelectric actuators for rapid, fine adjustment of the direction of the laser beam. The voltages applied to the piezoelectric actuators include components designed to scan the beam in a circular pattern so that the beam traces out a narrow cone (60 microradians wide in the initial application) about the direction in which it is nominally aimed. This scan is performed at a frequency (2.5 Hz in the initial application) well below the resonance frequency of any vibration of the interferometer. The laser beam makes a round trip to both corner-cube reflectors and then interferes with the launched beam. The interference is detected on a photodiode. The length of the optical path is measured by a heterodyne technique: A 100- kHz frequency shift between the launched beam and a reference beam imposes, on the detected signal, an interferometric phase shift proportional to the length of the optical path. A phase meter comprising analog filters and specialized digital circuitry converts the phase shift to an indication of displacement, generating a digital signal proportional to the path length.

Asphaltic concrete pavement survey.

DOT National Transportation Integrated Search

1963-04-01

The ever increasing problem of wheel path rutting and excessive desification of asphaltic concrete pavement has been the subject of asphalt technology for quite sometime. It is known that the density of the pavement, which is significant for several ...

Design of the Longitudinal Dispersion Compensation System for the CHARA Array

NASA Astrophysics Data System (ADS)

Berger, D. H.; Bagnuolo, W. G.

2001-05-01

In recent years, the baselines of optical and infrared interferometers have been approaching half of a kilometer in length. With increased spatial layout comes new and challenging problems to solve. One common hurdle occurs when observing objects not perpendicular to the baseline. The result is one beam with added path length that must be added to the non-delayed beam such that identical phase fronts are combined together to produce fringes. For several interferometers without the addition of costly and logistically difficult evacuated delay lines, path length equalization occurs in long buildings through the ambient air medium. This causes a beam which is spectrally dispersed along the optical axis. The undesirable consequence is decreased fringe contrast. A solution is to disperse the uncompensated beam by inserting a block of glass to match the optical path lengths for all wavelengths within the observing waveband. A single glass solution is presented for the CHARA Array. Modeling, design and fabrication methods are also considered. The CHARA Array, a six-telescope O/IR interferometric array operated by Georgia State University on Mt. Wilson, California, was funded by the National Science Foundation, the W.M. Keck Foundation, the David and Lucile Packard Foundation, and Georgia State University. This research is also funded in part by the Michelson Fellowship Program sponsored by Jet Propulsion Laboratory.

The effect of path length and display size on memory for spatial information.

PubMed

Guérard, Katherine; Tremblay, Sébastien

2012-01-01

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

Multiple-Path-Length Optical Absorbance Cell

NASA Technical Reports Server (NTRS)

2001-01-01

An optical absorbance cell that offers a selection of multiple optical path lengths has been developed as part of a portable spectrometric instrument that measures absorption spectra of small samples of water and that costs less than does a conventional, non-portable laboratory spectrometer. The instrument is intended, more specifically, for use in studying colored dissolved organic matter (CDOM) in seawater, especially in coastal regions. Accurate characterization of CDOM is necessary for building bio-optical mathematical models of seawater. The multiple path lengths of the absorption cell afford a wide range of sensitivity needed for measuring the optical absorbances associated with the wide range of concentrations of CDOM observed in nature. The instrument operates in the wavelength range of 370 to 725 nm. The major subsystems of the instrument (see figure) include a color-balanced light source; the absorption cell; a peristaltic pump; a high-precision, low-noise fiber optic spectrometer; and a laptop or other personal computer. A fiber-optic cable transmits light from the source to the absorption cell. Other optical fibers transmit light from the absorption cell to the spectrometer,

Investigating brain community structure abnormalities in bipolar disorder using path length associated community estimation.

PubMed

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

2014-05-01

In this article, we present path length associated community estimation (PLACE), a comprehensive framework for studying node-level community structure. Instead of the well-known Q modularity metric, PLACE utilizes a novel metric, Ψ(PL), which measures the difference between intercommunity versus intracommunity path lengths. We compared community structures in human healthy brain networks generated using these two metrics and argued that Ψ(PL) may have theoretical advantages. PLACE consists of the following: (1) extracting community structure using top-down hierarchical binary trees, where a branch at each bifurcation denotes a collection of nodes that form a community at that level, (2) constructing and assessing mean group community structure, and (3) detecting node-level changes in community between groups. We applied PLACE and investigated the structural brain networks obtained from a sample of 25 euthymic bipolar I subjects versus 25 gender- and age-matched healthy controls. Results showed community structural differences in posterior default mode network regions, with the bipolar group exhibiting left-right decoupling. Copyright © 2013 Wiley Periodicals, Inc.

Fast wavelength tuning techniques for external cavity lasers

DOEpatents

Wysocki, Gerard [Princeton, NJ; Tittel, Frank K [Houston, TX

2011-01-11

An apparatus comprising a laser source configured to emit a light beam along a first path, an optical beam steering component configured to steer the light beam from the first path to a second path at an angle to the first path, and a diffraction grating configured to reflect back at least a portion of the light beam along the second path, wherein the angle determines an external cavity length. Included is an apparatus comprising a laser source configured to emit a light beam along a first path, a beam steering component configured to redirect the light beam to a second path at an angle to the first path, wherein the optical beam steering component is configured to change the angle at a rate of at least about one Kilohertz, and a diffraction grating configured to reflect back at least a portion of the light beam along the second path.

Frost sensor for use in defrost controls for refrigeration

DOEpatents

French, Patrick D.; Butz, James R.; Veatch, Bradley D.; O'Connor, Michael W.

2002-01-01

An apparatus and method for measuring the total thermal resistance to heat flow from the air to the evaporative cooler fins of a refrigeration system. The apparatus is a frost sensor that measures the reduction in heat flow due to the added thermal resistance of ice (reduced conduction) as well as the reduction in heat flow due to the blockage of airflow (reduced convection) from excessive ice formation. The sensor triggers a defrost cycle when needed, instead of on a timed interval. The invention is also a method for control of frost in a system that transfers heat from air to a refrigerant along a thermal path. The method involves measuring the thermal conductivity of the thermal path from the air to the refrigerant, recognizing a reduction in thermal conductivity due to the thermal insulation effect of the frost and due to the loss of airflow from excessive ice formation; and controlling the defrosting of the system.

Deflate decompressor

DOEpatents

Hamlet, Jason R [Albuquerque, NM; Robertson, Perry J [Albuquerque, NM; Pierson, Lyndon G [Albuquerque, NM; Olsberg, Ronald R [Albuquerque, NM

2012-02-28

A deflate decompressor includes at least one decompressor unit, a memory access controller, a feedback path, and an output buffer unit. The memory access controller is coupled to the decompressor unit via a data path and includes a data buffer to receive the data stream and temporarily buffer a first portion the data stream. The memory access controller transfers fixed length data units of the data stream from the data buffer to the decompressor unit with reference to a memory pointer pointing into the memory buffer. The feedback path couples the decompressor unit to the memory access controller to feed back decrement values to the memory access controller for updating the memory pointer. The decrement values each indicate a number of bits unused by the decompressor unit when decoding the fixed length data units. The output buffer unit buffers a second portion of the data stream after decompression.

Precision Control of Thermal Transport in Cryogenic Single-Crystal Silicon Devices

NASA Technical Reports Server (NTRS)

Rostem, K.; Chuss, D. T.; Colazo, F. A.; Crowe, E. J.; Denis, K. L.; Lourie, N. P.; Moseley, S. H.; Stevenson, T. R.; Wollack, E. J.

2014-01-01

We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than, even when the surface is fairly smooth, 510 nm rms, and the peak thermal wavelength is 0.6 microns. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order, the conductance is dominated by ballistic transport and is effectively set by the beam cross-sectional area. We have demonstrated a uniformity of +/-8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

40 CFR 1033.525 - Smoke testing.

Code of Federal Regulations, 2011 CFR

2011-07-01

... measure smoke emissions using a full-flow, open path light extinction smokemeter. A light extinction meter... path length equal to the hydraulic diameter. The light extinction meter must meet the requirements of... apertures (or windows and lenses) and on the axis of the light beam. (8) You may use light extinction meters...

40 CFR 1033.525 - Smoke testing.

Code of Federal Regulations, 2014 CFR

2014-07-01

... measure smoke emissions using a full-flow, open path light extinction smokemeter. A light extinction meter... path length equal to the hydraulic diameter. The light extinction meter must meet the requirements of... apertures (or windows and lenses) and on the axis of the light beam. (8) You may use light extinction meters...

40 CFR 1033.525 - Smoke testing.

Code of Federal Regulations, 2013 CFR

2013-07-01

... measure smoke emissions using a full-flow, open path light extinction smokemeter. A light extinction meter... path length equal to the hydraulic diameter. The light extinction meter must meet the requirements of... apertures (or windows and lenses) and on the axis of the light beam. (8) You may use light extinction meters...

40 CFR 1033.525 - Smoke testing.

Code of Federal Regulations, 2012 CFR

2012-07-01

... measure smoke emissions using a full-flow, open path light extinction smokemeter. A light extinction meter... path length equal to the hydraulic diameter. The light extinction meter must meet the requirements of... apertures (or windows and lenses) and on the axis of the light beam. (8) You may use light extinction meters...

10 CFR 430.2 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... fittings, or the identical water-passage design features that use the same path of water in the highest... the same path of water in the highest-flow mode. (20) With respect to water closets, which have...-foot high output lamps) with recessed double contact bases of nominal overall length of 96 inches; (4...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riza, Nabeel Agha; Perez, Frank

A remote temperature sensing system includes a light source selectively producing light at two different wavelengths and a sensor device having an optical path length that varies as a function of temperature. The sensor receives light emitted by the light source and redirects the light along the optical path length. The system also includes a detector receiving redirected light from the sensor device and generating respective signals indicative of respective intensities of received redirected light corresponding to respective wavelengths of light emitted by the light source. The system also includes a processor processing the signals generated by the detector tomore » calculate a temperature of the device.« less

On the structural properties of small-world networks with range-limited shortcut links

NASA Astrophysics Data System (ADS)

Jia, Tao; Kulkarni, Rahul V.

2013-12-01

We explore a new variant of Small-World Networks (SWNs), in which an additional parameter (r) sets the length scale over which shortcuts are uniformly distributed. When r=0 we have an ordered network, whereas r=1 corresponds to the original Watts-Strogatz SWN model. These limited range SWNs have a similar degree distribution and scaling properties as the original SWN model. We observe the small-world phenomenon for r≪1, indicating that global shortcuts are not necessary for the small-world effect. For limited range SWNs, the average path length changes nonmonotonically with system size, whereas for the original SWN model it increases monotonically. We propose an expression for the average path length for limited range SWNs based on numerical simulations and analytical approximations.

Nativity status/length of stay in the US and excessive gestational weight gain in New York City teens, 2008-2010.

PubMed

Huynh, Mary H; Borrell, Luisa N; Chambers, Earle C

2015-02-01

Nativity status/length of stay in the US has been found to be associated with obesity. However, little work has examined the role of nativity status/length of stay in excessive gestational weight gain (EGWG) in adolescents. This study utilized New York City Department of Health and Mental Hygiene birth certificate data in a cross-sectional analysis of 15,715 singleton births to primiparous teen mothers (12-19 years) between 2008 and 2010. Nativity and length of stay in the United States (US) were obtained from birth certificates. EGWG was calculated using weight at delivery and pre-pregnancy weight. Prevalence ratios were calculated through generalized estimating equations to assess the strength of the association between nativity status/length of US residence and EGWG. For US-born teens, 43 % gained more weight than recommended as compared to 32 % for foreign-born teens who have lived in the US for less than 5 years (FB <5 years). Following adjustment for maternal demographics and other factors, US-born teens (adjusted prevalence ratios (APR) (CI) 1.26 [1.18,1.34]), FB 10+ years (APR (CI) 1.17 [1.07,1.28]), and FB 5-10 years (APR (CI) 1.11 [1.01,1.21]) were more likely to have gained weight excessively as compared to FB <5 years. US-born teens and FB teens that have been in the US longer than 5 years are more likely to gain weight excessively during pregnancy as compared to teens with fewer than 5 years in the US. These results identify a critical period when adolescents are in frequent contact with health care providers and can receive counseling regarding healthy weight gain.

Effect of nosocomial vancomycin-resistant enterococcal bacteremia on mortality, length of stay, and costs.

PubMed

Song, Xiaoyan; Srinivasan, Arjun; Plaut, David; Perl, Trish M

2003-04-01

To determine the impact of vancomycin-resistant enterococcal bacteremia on patient outcomes and costs by assessing mortality, excess length of stay, and charges attributable to it. A population-based, matched, historical cohort study. A 1,025-bed, university-based teaching facility and referral hospital. Two hundred seventy-seven vancomycin-resistant enterococcal bacteremia case-patients and 277 matched control-patients identified between 1993 and 2000. The crude mortality rate was 50.2% and 19.9% for case-patients and control-patients, respectively, yielding a mortality rate of 30.3% attributable to vancomycin-resistant enterococcal bacteremia. The excess length of hospital stay attributable to vancomycin-resistant enterococcal bacteremia was 17 days, of which 12 days were spent in intensive care units. On average, dollars 77,558 in extra charges was attributable to each vancomycin-resistant enterococcal bacteremia. To adjust for severity of illness, 159 pairs of case-patients and control-patients, who had the same severity of illness (All Patient Refined-Diagnosis Related Group complexity level), were further analyzed. When patients were stratified by severity of illness, the crude mortality rate was 50.3% among case-patients compared with 27.7% among control-patients, accounting for an attributable mortality rate of 22.6%. Attributable excess length of stay and charges were 17 days and dollars 81,208, respectively. Vancomycin-resistant enterococcal bacteremia contributes significantly to excess mortality and economic loss, once severity of illness is considered. Efforts to prevent these infections will likely be cost-effective.

Paths with more turns are perceived as longer: misperceptions with map-based and abstracted path stimuli.

PubMed

Brunyé, Tad T; Mahoney, Caroline R; Taylor, Holly A

2015-04-01

When navigating, people tend to overestimate distances when routes contain more turns, termed the route-angularity effect. Three experiments examined the source and generality of this effect. The first two experiments examined whether route-angularity effects occur while viewing maps and might be related to sex differences or sense of direction. The third experiment tested whether the route-angularity effect would occur with stimuli devoid of spatial context, reducing influences of environmental experience and visual complexity. In the three experiments, participants (N=1,552; M=32.2 yr.; 992 men, 560 women) viewed paths plotted on maps (Exps. 1 and 2) or against a blank background (Exp. 3). The depicted paths were always the same overall length, but varied in the number of turns (from 1 to 7) connecting an origin and destination. Participants were asked to estimate the time to traverse each path (Exp. 1) or the length of each path (Exps. 2 and 3). The Santa Barbara Sense of Direction questionnaire was administered to assess whether overall spatial sense of direction would be negatively related to the magnitude of the route-angularity effect. Repeated-measures analyses of variance (ANOVAs) indicated that paths with more turns elicited estimates of greater distance and travel times, whether they were depicted on maps or blank backgrounds. Linear regressions also indicated that these effects were significantly larger in those with a relatively low sense of direction. The results support the route-angularity effect and extend it to paths plotted on map-based stimuli. Furthermore, because the route-angularity effect was shown with paths plotted against blank backgrounds, route-angularity effects are not specific to understanding environments and may arise at the level of visual perception.

Longitudinal Mediation Modeling of Unhealthy Behaviors as Mediators between Workplace Demands/Support and Depressive Symptoms

PubMed Central

Magnusson Hanson, Linda L.; Peristera, Paraskevi; Chungkham, Holendro Singh; Westerlund, Hugo

2016-01-01

Lifestyle has been regarded as a key pathway through which adverse psychosocial working characteristics can give rise to long-term health problems. The purpose of this study was to estimate the indirect/mediated effect of health behaviors in the longitudinal work characteristics-depression relationship. The analyses were based on the Swedish Longitudinal Occupational Survey of Health, including 3706 working participants with repeat survey measures on four occasions (2008, 2010, 2012 and 2014). Psychosocial work characteristics including demands and social support were analyzed in relation to depressive symptoms. Autoregressive longitudinal mediation models using structural equation modeling were used to estimate the intermediate effects of unhealthy behaviors including current smoking, excessive alcohol consumption, unhealthy diet and physical inactivity. Both workplace demands and social support were related to later depressive symptoms. In bivariate models we found no significant paths from workplace demands to health behaviors, but two out of three significant time-specific paths from workplace support to excessive drinking and from excessive drinking to depressive symptoms. Social support was also associated with subsequent unhealthy diet, and one path from unhealthy diet to depressive symptoms was found. However, despite indications of certain longitudinal relationships between psychosocial working conditions and health behaviors as well as between health behaviors and depressive symptoms, no significant intermediate effects were found (p>0.05). We conclude that changes in unhealthy behaviors over a period of two years are unlikely to act as strong intermediaries in the longitudinal relationship between job demands and depressive symptoms and between social support and depressive symptoms. PMID:28036376

Longitudinal Mediation Modeling of Unhealthy Behaviors as Mediators between Workplace Demands/Support and Depressive Symptoms.

PubMed

Magnusson Hanson, Linda L; Peristera, Paraskevi; Chungkham, Holendro Singh; Westerlund, Hugo

2016-01-01

Lifestyle has been regarded as a key pathway through which adverse psychosocial working characteristics can give rise to long-term health problems. The purpose of this study was to estimate the indirect/mediated effect of health behaviors in the longitudinal work characteristics-depression relationship. The analyses were based on the Swedish Longitudinal Occupational Survey of Health, including 3706 working participants with repeat survey measures on four occasions (2008, 2010, 2012 and 2014). Psychosocial work characteristics including demands and social support were analyzed in relation to depressive symptoms. Autoregressive longitudinal mediation models using structural equation modeling were used to estimate the intermediate effects of unhealthy behaviors including current smoking, excessive alcohol consumption, unhealthy diet and physical inactivity. Both workplace demands and social support were related to later depressive symptoms. In bivariate models we found no significant paths from workplace demands to health behaviors, but two out of three significant time-specific paths from workplace support to excessive drinking and from excessive drinking to depressive symptoms. Social support was also associated with subsequent unhealthy diet, and one path from unhealthy diet to depressive symptoms was found. However, despite indications of certain longitudinal relationships between psychosocial working conditions and health behaviors as well as between health behaviors and depressive symptoms, no significant intermediate effects were found (p>0.05). We conclude that changes in unhealthy behaviors over a period of two years are unlikely to act as strong intermediaries in the longitudinal relationship between job demands and depressive symptoms and between social support and depressive symptoms.

Path Length Fluctuations Derived from Site Testing Interferometer Data

NASA Technical Reports Server (NTRS)

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

2010-01-01

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

Cyclic fatigue resistance of R-Pilot, WaveOne Gold Glider, and ProGlider glide path instruments.

PubMed

Keskin, Cangül; İnan, Uğur; Demiral, Murat; Keleş, Ali

2018-02-17

The aim of the present study was to compare the cyclic fatigue resistance of R-Pilot (VDW; Munich, Germany) with ProGlider (Denstply Sirona; Ballaigues, Switzerland) and WaveOne Gold Glider (Denstply Sirona; Ballaigues, Switzerland) glide path instruments. R-Pilot, ProGlider, and WaveOne Gold Glider instruments were collected (n = 15) and tested in a dynamic cyclic fatigue test device, which has an artificial canal with 60° angle of curvature and a 5-mm radius of curvature. All instruments were operated until fracture occurred, and both time to fracture (TF) and the lengths of the fractured fragments were recorded. Mean and standard deviations of TF and fragment length were calculated for each reciprocating system. TF data and fractured fragment length data were subjected to one-way ANOVA and post-hoc Tukey tests (P < 0.05). Also a Weibull analysis was performed on TF data. The cyclic fatigue resistance values of the WaveOne Gold Glider and R-Pilot were significantly higher than those of the ProGlider (P < 0.05), with no significant difference between them (P > 0.05). Weibull analysis revealed that WaveOne Gold Glider showed the highest predicted TF value for 99% survival rate, which was followed by R-Pilot and ProGlider. Regarding the length of the fractured tips, there were no significant differences among the instruments (P > 0.05). The reciprocating WaveOne Gold Glider and R-Pilot instruments had significantly higher cyclic fatigue resistance than rotary ProGlider instruments. This study reported that novel reciprocating glide path instruments exhibited higher cyclic fatigue resistance than rotating glide path instrument.

Changes in the limb kinematics and walking-distance estimation after shank elongation: evidence for a locomotor body schema?

PubMed

Dominici, Nadia; Daprati, Elena; Nico, Daniele; Cappellini, Germana; Ivanenko, Yuri P; Lacquaniti, Francesco

2009-03-01

When walking, step length provides critical information on traveled distance along the ongoing path [corrected] Little is known on the role that knowledge about body dimensions plays within this process. Here we directly addressed this question by evaluating whether changes in body proportions interfere with computation of traveled distance for targets located outside the reaching space. We studied locomotion and distance estimation in an achondroplastic child (ACH, 11 yr) before and after surgical elongation of the shank segments of both lower limbs and in healthy adults walking on stilts, designed to mimic shank-segment elongation. Kinematic analysis of gait revealed that dynamic coupling of the thigh, shank, and foot segments changed substantially as a result of elongation. Step length remained unvaried, in spite of the significant increase in total limb length ( approximately 1.5-fold). These relatively shorter strides resulted from smaller oscillations of the shank segment, as would be predicted by proportional increments in limb size and not by asymmetrical segmental increment as in the present case (length of thighs was not modified). Distance estimation was measured by walking with eyes closed toward a memorized target. Before surgery, the behavior of ACH was comparable to that of typically developing participants. In contrast, following shank elongation, the ACH walked significantly shorter distances when aiming at the same targets. Comparable changes in limb kinematics, stride length, and estimation of traveled distance were found in adults wearing on stilts, suggesting that path integration errors in both cases were related to alterations in the intersegmental coordination of the walking limbs. The results are consistent with a dynamic locomotor body schema used for controlling step length and path estimation, based on inherent relationships between gait parameters and body proportions.

Minimum-fuel, three-dimensional flight paths for jet transports

NASA Technical Reports Server (NTRS)

Neuman, F.; Kreindler, E.

1985-01-01

A number of studies dealing with fuel minimization are concerned with three-dimensional flight. However, only Neuman and Kreindler (1982) consider cases involving commercial jet transports. In the latter study, only the climb-out and descent portions of complete long-range flight paths below 10,000 ft altitude have been investigated. The present investigation is concerned with the computation of minimum-fuel nonturning and turning flight paths for climb-outs from 2000 to 10,000 ft for long-range flights (greater than 50 n mi), and for complete flight paths of lengths between 5 and 50 n mi.

Application of particle swarm optimization in path planning of mobile robot

NASA Astrophysics Data System (ADS)

Wang, Yong; Cai, Feng; Wang, Ying

2017-08-01

In order to realize the optimal path planning of mobile robot in unknown environment, a particle swarm optimization algorithm based on path length as fitness function is proposed. The location of the global optimal particle is determined by the minimum fitness value, and the robot moves along the points of the optimal particles to the target position. The process of moving to the target point is done with MATLAB R2014a. Compared with the standard particle swarm optimization algorithm, the simulation results show that this method can effectively avoid all obstacles and get the optimal path.

Effect of drug Piper nigrum on magnesium chloride at varying concentration and temperature through ultrasonic method: A thermoacoustic study

NASA Astrophysics Data System (ADS)

Nalle, Pallavi B.; Deshmukh, S. S.; Dorik, R. G.; Jadhav, K. M.

2016-12-01

The ultrasonic velocity (U), density (ρ), and viscosity (η) of an ethanolic extract of drug Piper nigrum with MgCl2 (metal ions) have been measured as a function of the number of moles n = (0.7009, 1.4018, 2.1027, 2.8036 and 3.5045) at 303.15, 308.15, 313.15 and 318.15 K temperature. Various thermoacoustic and their excess values such as adiabatic compressibilities (β), intermolecular free lengths (Lf), excess adiabatic compressibility (βE), excess intermolecular free length (?) have been computed using values of ultrasonic velocity (U), density (ρ), and viscosity (η). The excess values of ultrasonic velocity, specific acoustic impedance are positive, whereas isentropic compressibility and intermolecular free lengths are negative over the entire composition range of MgCl2 + P. nigrum which indicates the presence of specific interactions between unlike molecules. Molecular association is reflected by ultrasonic investigation. This may be interpreted due to the of complex formation. The chemical interaction may involve the association due to the solute-solvent and ion-solvent interaction and due to the formation of charge-transfer complexes, which is useful to understand the mechanism of their metabolism in living systems. The results obtained from these studies are helpful for pharmacological applications of drugs, transport of drugs across biological membranes.

Implementation Of Haversine Formula And Best First Search Method In Searching Of Tsunami Evacuation Route

NASA Astrophysics Data System (ADS)

Anisya; Yoga Swara, Ganda

2017-12-01

Padang is one of the cities prone to earthquake disaster with tsunami due to its position at the meeting of two active plates, this is, a source of potentially powerful earthquake and tsunami. Central government and most offices are located in the red zone (vulnerable areas), it will also affect the evacuation of the population during the earthquake and tsunami disaster. In this study, researchers produced a system of search nearest shelter using best-first-search method. This method uses the heuristic function, the amount of cost taken and the estimated value or travel time, path length and population density. To calculate the length of the path, researchers used method of haversine formula. The value obtained from the calculation process is implemented on a web-based system. Some alternative paths and some of the closest shelters will be displayed in the system.

Procedure Enabling Simulation and In-Depth Analysis of Optical Effects in Camera-Based Time-Of Sensors

NASA Astrophysics Data System (ADS)

Baumgart, M.; Druml, N.; Consani, M.

2018-05-01

This paper presents a simulation approach for Time-of-Flight cameras to estimate sensor performance and accuracy, as well as to help understanding experimentally discovered effects. The main scope is the detailed simulation of the optical signals. We use a raytracing-based approach and use the optical path length as the master parameter for depth calculations. The procedure is described in detail with references to our implementation in Zemax OpticStudio and Python. Our simulation approach supports multiple and extended light sources and allows accounting for all effects within the geometrical optics model. Especially multi-object reflection/scattering ray-paths, translucent objects, and aberration effects (e.g. distortion caused by the ToF lens) are supported. The optical path length approach also enables the implementation of different ToF senor types and transient imaging evaluations. The main features are demonstrated on a simple 3D test scene.

Truncation Depth Rule-of-Thumb for Convolutional Codes

NASA Technical Reports Server (NTRS)

Moision, Bruce

2009-01-01

In this innovation, it is shown that a commonly used rule of thumb (that the truncation depth of a convolutional code should be five times the memory length, m, of the code) is accurate only for rate 1/2 codes. In fact, the truncation depth should be 2.5 m/(1 - r), where r is the code rate. The accuracy of this new rule is demonstrated by tabulating the distance properties of a large set of known codes. This new rule was derived by bounding the losses due to truncation as a function of the code rate. With regard to particular codes, a good indicator of the required truncation depth is the path length at which all paths that diverge from a particular path have accumulated the minimum distance of the code. It is shown that the new rule of thumb provides an accurate prediction of this depth for codes of varying rates.

Measurement of thermo-optic properties of Y3Al5O12, Lu3Al5O12, YAIO3, LiYF4, LiLuF4, BaY2F8, KGd(WO4)2, and KY(WO4)2 laser crystals in the 80-300 K temperature range

NASA Astrophysics Data System (ADS)

Aggarwal, R. L.; Ripin, D. J.; Ochoa, J. R.; Fan, T. Y.

2005-11-01

Thermo-optic materials properties of laser host materials have been measured to enable solid-state laser performance modeling. The thermo-optic properties include thermal diffusivity (β), specific heat at constant pressure (Cp), thermal conductivity (κ), coefficient of thermal expansion (α), thermal coefficient of the optical path length (γ) equal to (dO/dT)/L, and thermal coefficient of refractive index (dn/dT) at 1064nm; O denotes the optical path length, which is equal to the product of the refractive index (n) and sample length (L). Thermal diffusivity and specific heat were measured using laser-flash method. Thermal conductivity was deduced using measured values of β, Cp, and the density (ρ ). Thermal expansion was measured using a Michelson laser interferometer. Thermal coefficient of the optical path length was measured at 1064nm, using interference between light reflected from the front and rear facets of the sample. Thermal coefficient of the refractive index was determined, using the measured values of γ, α, and n. β and κ of Y3Al5O12, YAIO3, and LiYF4 were found to decrease, as expected, upon doping with Yb.

Kinetic simulations of gas breakdown in the dense plasma focus

DOE PAGES

Bennett, N.; Blasco, M.; Breeding, K.; ...

2017-06-09

We describe the first fully-kinetic, collisional, and electromagnetic simulations of the breakdown phase of a MA-scale dense plasma focus and are shown to agree with measured electrical characteristics, including breakdown time. In the model, avalanche ionization is driven by cathode electron emission and this results in incomplete gas breakdown along the insulator. This reinforces the importance of the conditioning process that creates a metallic layer on the insulator surface. The simulations, nonetheless, help explain the relationship between the gas pressure, the insulator length, and the coaxial gap width. In the past, researchers noted three breakdown patterns related to pressure. Simulationmore » and analytic results show that at low pressures, long ionization path lengths lead to volumetric breakdown, while high pressures lead to breakdown across the relatively small coaxial electrode gap. In an intermediate pressure regime, ionization path lengths are comparable to the insulator length which promotes ideal breakdown along the insulator surface.« less

Minimal entropy probability paths between genome families.

PubMed

Ahlbrandt, Calvin; Benson, Gary; Casey, William

2004-05-01

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.

Completely automated open-path FT-IR spectrometry.

PubMed

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

2009-01-01

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

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks

PubMed Central

Al-Samman, A. M.; Rahman, T. A.; Azmi, M. H.; Hindia, M. N.; Khan, I.; Hanafi, E.

2016-01-01

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios. PMID:27654703

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks.

PubMed

Al-Samman, A M; Rahman, T A; Azmi, M H; Hindia, M N; Khan, I; Hanafi, E

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios.

High temperature, minimally invasive optical sensing modules

DOEpatents

Riza, Nabeel Agha [Oviedo, FL; Perez, Frank [Tujunga, CA

2008-02-05

A remote temperature sensing system includes a light source selectively producing light at two different wavelengths and a sensor device having an optical path length that varies as a function of temperature. The sensor receives light emitted by the light source and redirects the light along the optical path length. The system also includes a detector receiving redirected light from the sensor device and generating respective signals indicative of respective intensities of received redirected light corresponding to respective wavelengths of light emitted by the light source. The system also includes a processor processing the signals generated by the detector to calculate a temperature of the device.

Passive haptics in a knee arthroscopy simulator: is it valid for core skills training?

PubMed

McCarthy, Avril D; Moody, Louise; Waterworth, Alan R; Bickerstaff, Derek R

2006-01-01

Previous investigation of a cost-effective virtual reality arthroscopic training system, the Sheffield Knee Arthroscopy Training System (SKATS), indicated the desirability of including haptic feedback. A formal task analysis confirmed the importance of knee positioning as a core skill for trainees learning to navigate the knee arthroscopically. The system cost and existing limb interface, which permits knee positioning, would be compromised by the addition of commercial active haptic devices available currently. The validation results obtained when passive haptic feedback (resistance provided by physical structures) is provided indicate that SKATS has construct, predictive and face validity for navigation and triangulation training. When tested using SKATS, experienced surgeons (n = 11) performed significantly faster, located significantly more pathologies, and showed significantly shorter arthroscope path lengths than a less experienced surgeon cohort (n = 12). After SKATS training sessions, novices (n = 3) showed significant improvements in: task completion time, shorter arthroscope path lengths, shorter probe path lengths, and fewer arthroscope tip contacts. Main improvements occurred after the first two practice sessions, indicating rapid familiarization and a training effect. Feedback from questionnaires completed by orthopaedic surgeons indicates that the system has face validity for its remit of basic arthroscopic training.

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

NASA Astrophysics Data System (ADS)

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

2014-07-01

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

Estimation of crosstalk in LED fNIRS by photon propagation Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Iwano, Takayuki; Umeyama, Shinji

2015-12-01

fNIRS (functional near-Infrared spectroscopy) can measure brain activity non-invasively and has advantages such as low cost and portability. While the conventional fNIRS has used laser light, LED light fNIRS is recently becoming common in use. Using LED for fNIRS, equipment can be more inexpensive and more portable. LED light, however, has a wider illumination spectrum than laser light, which may change crosstalk between the calculated concentration change of oxygenated and deoxygenated hemoglobins. The crosstalk is caused by difference in light path length in the head tissues depending on wavelengths used. We conducted Monte Carlo simulations of photon propagation in the tissue layers of head (scalp, skull, CSF, gray matter, and white matter) to estimate the light path length in each layers. Based on the estimated path lengths, the crosstalk in fNIRS using LED light was calculated. Our results showed that LED light more increases the crosstalk than laser light does when certain combinations of wavelengths were adopted. Even in such cases, the crosstalk increased by using LED light can be effectively suppressed by replacing the value of extinction coefficients used in the hemoglobin calculation to their weighted average over illumination spectrum.

Singularity of the time-energy uncertainty in adiabatic perturbation and cycloids on a Bloch sphere

PubMed Central

Oh, Sangchul; Hu, Xuedong; Nori, Franco; Kais, Sabre

2016-01-01

Adiabatic perturbation is shown to be singular from the exact solution of a spin-1/2 particle in a uniformly rotating magnetic field. Due to a non-adiabatic effect, its quantum trajectory on a Bloch sphere is a cycloid traced by a circle rolling along an adiabatic path. As the magnetic field rotates more and more slowly, the time-energy uncertainty, proportional to the length of the quantum trajectory, calculated by the exact solution is entirely different from the one obtained by the adiabatic path traced by the instantaneous eigenstate. However, the non-adiabatic Aharonov- Anandan geometric phase, measured by the area enclosed by the exact path, approaches smoothly the adiabatic Berry phase, proportional to the area enclosed by the adiabatic path. The singular limit of the time-energy uncertainty and the regular limit of the geometric phase are associated with the arc length and arc area of the cycloid on a Bloch sphere, respectively. Prolate and curtate cycloids are also traced by different initial states outside and inside of the rolling circle, respectively. The axis trajectory of the rolling circle, parallel to the adiabatic path, is shown to be an example of transitionless driving. The non-adiabatic resonance is visualized by the number of cycloid arcs. PMID:26916031

Excess current experiment on YBCO tape conductor with metal stabilized layer

NASA Astrophysics Data System (ADS)

Tasaki, Kenji; Yazawa, Takashi; Ono, Michitaka; Kuriyama, Toru

2006-06-01

Excess current experiments were performed using YBCO tape conductors with a metal stabilized layer on the superconducting layer. The purpose of this research is to obtain the stable criteria of energy dissipation when YBCO tape is forced to flow excess current higher than its critical current. This situation should be considered in power applications. In the experiments short-length samples were immersed in liquid nitrogen and several cycles of 50Hz sinusoidal current were supplied to the samples by an induction voltage regulator. The critical current of the samples was about 110 A. With pulse length as long as 60 ms, YBCO tapes were able to be energized up to twelve times as the critical current without electrical or mechanical deformation. Prior to the excess current experiments, temperature dependency of resistance of the sample was measured so that the temperature rise was estimated by the generated resistance. It is found that YBCO tapes with a copper stabilized layer can be transiently heated to over 400K without degradation.

Characteristics and limitations of GPS L1 observations from submerged antennas - Theoretical investigation in snow, ice, and freshwater and practical observations within a freshwater layer

NASA Astrophysics Data System (ADS)

Steiner, Ladina; Meindl, Michael; Geiger, Alain

2018-05-01

Observations from a submerged GNSS antenna underneath a snowpack need to be analyzed to investigate its potential for snowpack characterization. The magnitude of the main interaction processes involved in the GPS L1 signal propagation through different layers of snow, ice, or freshwater is examined theoretically in the present paper. For this purpose, the GPS signal penetration depth, attenuation, reflection, refraction as well as the excess path length are theoretically investigated. Liquid water exerts the largest influence on GPS signal propagation through a snowpack. An experiment is thus set up with a submerged geodetic GPS antenna to investigate the influence of liquid water on the GPS observations. The experimental results correspond well with theory and show that the GPS signal penetrates the liquid water up to three centimeters. The error in the height component due to the signal propagation delay in water can be corrected with a newly derived model. The water level above the submerged antenna could also be estimated.

Integration across Time Determines Path Deviation Discrimination for Moving Objects

PubMed Central

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

2008-01-01

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

Transitioning to a narrow path: the impact of fear of falling in older adults.

PubMed

Dunlap, Pamela; Perera, Subashan; VanSwearingen, Jessie M; Wert, David; Brach, Jennifer S

2012-01-01

Everyday ambulation requires navigation of variable terrain, transitions from wide to narrow pathways, and avoiding obstacles. While the effect of age on the transition to a narrow path has been examined briefly, little is known about the impact of fear of falling on gait during the transition to a narrow path. The purpose was to examine the effect of age and fear of falling on gait during transition to a narrow path. In 31 young, mean age=25.3 years, and 30 older adults, mean age=79.6 years, step length, step time, step width and gait speed were examined during usual and transition to narrow pathway using an instrumented walkway. During the transition to narrow walk condition, fearful older adults compared to young had a wider step width (0.06 m vs 0.04 m) prior to the narrow path and took shorter steps (0.53 m vs 0.72 m; p<0.001). Compared to non-fearful older adults, fearful older adults walked slower and took shorter steps during narrow path walking (gait speed: 1.1m/s vs 0.82 m/s; p=0.01; step length: 0.60 m vs 0.47 m; p=0.03). In young and non-fearful older adults narrow path gait was similar to usual gait. Whereas older adults who were fearful, walked slower (0.82 m/s vs 0.91 m/s; p=0.001) and took shorter steps (0.44 m vs 0.53 m; p=0.004) during narrow path walking compared to usual walking. Changes in gait characteristics with transitioning to a narrow pathway were greater for fear of falling than for age. Copyright © 2011 Elsevier B.V. All rights reserved.

Thermodynamical and excess thermoacoustical study on some monosaccharide (glucose) with enzyme amylase in aqueous media at 298.15 K

NASA Astrophysics Data System (ADS)

Nithiyanantham, S.; Palaniappan, L.

2011-03-01

Ultrasonic velocity (U), density (ρ) and viscosity (η) measurements have been carried out in three ternary mixtures of glucose with amylase in aqueous medium at 298.15 K. The experimental data have been used to calculate some derived parameters such as acoustical impedance (Z), relative association (RA), Rao's constant (R), Wada's constant (W), relaxation time (τ), relaxation amplitude (α/f2), relaxation strength (r), and some excess thermodynamical properties like excess adiabatic compressibility (βE), excess free length (LfE) excess free volume (VfE), excess internal pressure (πiE) and excess acoustical impedance (ZE). The above parameters have been evaluated and discussed in light of molecular interactions in the mixture.

Ultra-High Resolution Ion Mobility Separations Utilizing Traveling Waves in a 13 m Serpentine Path Length Structures for Lossless Ion Manipulations Module

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Ibrahim, Yehia M.; Hamid, Ahmed M.

We report the development and initial evaluation of a 13-m path length Structures for Lossless Manipulations (SLIM) module for achieving high resolution separations using traveling waves (TW) with ion mobility (IM) spectrometry. The TW SLIM module was fabricated using two mirror-image printed circuit boards with appropriately configured RF, DC and TW electrodes and positioned with a 2.75-mm inter-surface gap. Ions were effective confined between the surfaces by RF-generated pseudopotential fields and moved losslessly through a serpentine path including 44 “U” turns using TWs. The ion mobility resolution was characterized at different pressures, gaps between the SLIM surfaces, TW and RFmore » parameters. After initial optimization the SLIM IM-MS module provided about 5-fold higher resolution separations than present commercially available drift tube or traveling wave IM-MS platforms. Peak capacity and peak generation rates achieved were 246 and 370 s-1, respectively, at a TW speed of 148 m/s. The high resolution achieved in the TW SLIM IM-MS enabled e.g., isomeric sugars (Lacto-N-fucopentaose I and Lacto-N-fucopentaose II) to be baseline resolved, and peptides from a albumin tryptic digest much better resolved than with existing commercial IM-MS platforms. The present work also provides a foundation for the development of much higher resolution SLIM devices based upon both considerably longer path lengths and multi-pass designs.« less

Driver retention strategy : the role of a career path

DOT National Transportation Integrated Search

2000-03-01

The voluntary turnover rate among truckload carriers, at 50-100 percent, is excessive when compared to other industries. The turnover rate has been known to exceed 150 percent. It is believed that are several factors are involved in this retention pr...

A depolarization and attenuation experiment using the COMSTAR and CTS satellites

NASA Technical Reports Server (NTRS)

Bostian, C. W.; Kauffman, S. R.; Manus, E. A.; Marshall, R. E.; Overstreet, W. P.; Persinger, R. R.; Stutzman, W. L.; Wiley, P. H.

1978-01-01

An experiment for measuring precipitation attenuation and depolarization on the CTS 11.7 and the COMSTAR 19.04 and 28.56 GHz downlinks is described. Attenuation scaling, effective path length, and the relationship between isolation and attenuation are discussed. Attenuation and effective path data are presented for the months of July, August, and September, 1977.

Low-coherence interferometric sensor system utilizing an integrated optics configuration

NASA Astrophysics Data System (ADS)

Plissi, M. V.; Rogers, A. J.; Brassington, D. J.; Wilson, M. G. F.

1995-08-01

The implementation of a twin Mach-Zehnder reference interferometer in an integrated optics substrate is described. From measurements of the fringe visibilities, an identification of the fringe order is attempted as a way to provide an absolute sensor for any parameter capable of modifying the difference in path length between two interfering optical paths.

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

PubMed

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

2013-05-20

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

Analyzing Water's Optical Absorption

NASA Technical Reports Server (NTRS)

2002-01-01

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

Comparison of Calculations and Measurements of the Off-Axis Radiation Dose (SI) in Liquid Nitrogen as a Function of Radiation Length.

DTIC Science & Technology

1984-12-01

radiation lengths. The off-axis dose in Silicon was calculated using the electron/photon transport code CYLTRAN and measured using thermal luminescent...various path lengths out to 2 radiation lengths. The cff-axis dose in Silicon was calculated using the electron/photon transport code CYLTRAN and measured... using thermal luminescent dosimeters (TLD’s). Calculations were performed on a CDC-7600 computer at Los Alamos National Laboratory and measurements

Longer breastfeeding duration reduces the positive relationships among gestational weight gain, birth weight and childhood anthropometrics.

PubMed

Zhu, Yeyi; Hernandez, Ladia M; Dong, Yongquan; Himes, John H; Hirschfeld, Steven; Forman, Michele R

2015-07-01

The relationship between gestational weight gain (GWG) and childhood growth remains controversial. An examination on whether infant feeding practices mediate this relationship may improve our understanding of it. We investigated whether the relationships among GWG, birth weight and childhood anthropometrics were mediated through infant feeding practices (breastfeeding duration and age at introduction of solid foods) in a cross-sectional multiethnic study of 1387 mothers and their children aged 0-5.9 years in the USA (2011-2012). Child anthropometrics included age-specific and sex-specific z-scores for weight-for-age (WAZ), height/length-for-age (HAZ), weight-for-height/length (WHZ) and body mass index-for-age (BMIZ); and ulnar length, a marker for limb growth. We used structural equation modelling to calculate standardised path coefficients and total, direct and indirect associations of GWG, birth weight and infant feeding practices with child anthropometrics. Maternal GWG had a positive indirect association with all anthropometrics mediated via birth weight, whereas longer breastfeeding duration reduced the positive associations of GWG and birth weight with WAZ, WHZ and BMIZ in non-Hispanics (β=-0.077, -0.064 and -0.106, respectively). Longer breastfeeding duration and introducing solid foods at a later age were positively associated with ulnar length (β=0.023 and 0.030, respectively) but not HAZ, suggesting a distinct association, for the first time, with limb growth. Findings suggest that promoting longer breastfeeding duration among women with excessive GWG who had high birthweight newborns may mitigate the potential for their offspring to develop obesity. In addition, findings reinforce the importance of promoting appropriate GWG and preventing high birth weight, which are positively associated with childhood anthropometrics. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Shortest multiple disconnected path for the analysis of entanglements in two- and three-dimensional polymeric systems

NASA Astrophysics Data System (ADS)

Kröger, Martin

2005-06-01

We present an algorithm which returns a shortest path and related number of entanglements for a given configuration of a polymeric system in 2 or 3 dimensions. Rubinstein and Helfand, and later Everaers et al. introduced a concept to extract primitive paths for dense polymeric melts made of linear chains (a multiple disconnected multibead 'path'), where each primitive path is defined as a path connecting the (space-fixed) ends of a polymer under the constraint of non-interpenetration (excluded volume) between primitive paths of different chains, such that the multiple disconnected path fulfills a minimization criterion. The present algorithm uses geometrical operations and provides a—model independent—efficient approximate solution to this challenging problem. Primitive paths are treated as 'infinitely' thin (we further allow for finite thickness to model excluded volume), and tensionless lines rather than multibead chains, excluded volume is taken into account without a force law. The present implementation allows to construct a shortest multiple disconnected path (SP) for 2D systems (polymeric chain within spherical obstacles) and an optimal SP for 3D systems (collection of polymeric chains). The number of entanglements is then simply obtained from the SP as either the number of interior kinks, or from the average length of a line segment. Further, information about structure and potentially also the dynamics of entanglements is immediately available from the SP. We apply the method to study the 'concentration' dependence of the degree of entanglement in phantom chain systems. Program summaryTitle of program:Z Catalogue number:ADVG Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVG Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Silicon Graphics (Irix), Sun (Solaris), PC (Linux) Operating systems or monitors under which the program has been tested: UNIX, Linux Program language used: USANSI Fortran 77 and Fortran 90 Memory required to execute with typical data: 1 MByte No. of lines in distributed program, including test data, etc.: 10 660 No. of bytes in distributed program, including test data, etc.: 119 551 Distribution formet:tar.gz Nature of physical problem: The problem is to obtain primitive paths substantiating a shortest multiple disconnected path (SP) for a given polymer configuration (chains of particles, with or without additional single particles as obstacles for the 2D case). Primitive paths are here defined as in [M. Rubinstein, E. Helfand, J. Chem. Phys. 82 (1985) 2477; R. Everaers, S.K. Sukumaran, G.S. Grest, C. Svaneborg, A. Sivasubramanian, K. Kremer, Science 303 (2004) 823] as the shortest line (path) respecting 'topological' constraints (from neighboring polymers or point obstacles) between ends of polymers. There is a unique solution for the 2D case. For the 3D case it is unique if we construct a primitive path of a single chain embedded within fixed line obstacles [J.S.B. Mitchell, Geometric shortest paths and network optimization, in: J.-R. Sack, J. Urrutia (Eds.), Handbook of Computational Geometry, Elsevier, Amsterdam, 2000, pp. 633-701]. For a large 3D configuration made of several chains, short is meant to be the Euclidean shortest multiple disconnected path (SP) where primitive paths are constructed for all chains simultaneously. While the latter problem, in general, does not possess a unique solution, the algorithm must return a locally optimal solution, robust against minor displacements of the disconnected path and chain re-labeling. The problem is solved if the number of kinks (or entanglements Z), explicitly deduced from the SP, is quite insensitive to the exact conformation of the SP which allows to estimate Z with a small error. Efficient method of solution: Primitive paths are constructed from the given polymer configuration (a non-shortest multiple disconnected path, including obstacles, if present) by first replacing each polymer contour by a line with a number of 'kinks' (beads, nodes) and 'segments' (edges). To obtain primitive paths, defined to be uncrossable by any other objects (neighboring primitive paths, line or point obstacles), the algorithm minimizes the length of all primitive paths consecutively, until a final minimum Euclidean length of the SP is reached. Fast geometric operations rather than dynamical methods are used to minimize the contour lengths of the primitive paths. Neighbor lists are used to keep track of potentially intersecting segments of other chains. Periodic boundary conditions are employed. A finite small line thickness is used in order to make sure that entanglements are not 'lost' due to finite precision of representation of numbers. Restrictions on the complexity of the problem: For a single chain embedded within fixed line or point obstacles, the algorithm returns the exact SP. For more complex problems, the algorithm returns a locally optimal SP. Except for exotic, probably rare, configurations it turns out that different locally optimal SPs possess quite an identical number of nodes. In general, the problem constructing the SP is known to be NP-hard [J.S.B. Mitchell, Geometric shortest paths and network optimization, in: J.-R. Sack, J. Urrutia (Eds.), Handbook of Computational Geometry, Elsevier, Amsterdam, 2000, pp. 633-701], and we offer a solution which should suffice to analyze physical problems, and gives an estimate about the precision and uniqueness of the result (from a standard deviation by varying the parameter: cyclicswitch). The program is NOT restricted to handle systems for which segment lengths of the SP exceed half the box size. Typical running time: Typical running times are approximately two orders of magnitude shorter compared with the ones needed for a corresponding molecular dynamics approach, and scale mostly linearly with system size. We provide a benchmark table.

Feasible Path Generation Using Bezier Curves for Car-Like Vehicle

NASA Astrophysics Data System (ADS)

Latip, Nor Badariyah Abdul; Omar, Rosli

2017-08-01

When planning a collision-free path for an autonomous vehicle, the main criteria that have to be considered are the shortest distance, lower computation time and completeness, i.e. a path can be found if one exists. Besides that, a feasible path for the autonomous vehicle is also crucial to guarantee that the vehicle can reach the target destination considering its kinematic constraints such as non-holonomic and minimum turning radius. In order to address these constraints, Bezier curves is applied. In this paper, Bezier curves are modeled and simulated using Matlab software and the feasibility of the resulting path is analyzed. Bezier curve is derived from a piece-wise linear pre-planned path. It is found that the Bezier curves has the capability of making the planned path feasible and could be embedded in a path planning algorithm for an autonomous vehicle with kinematic constraints. It is concluded that the length of segments of the pre-planned path have to be greater than a nominal value, derived from the vehicle wheelbase, maximum steering angle and maximum speed to ensure the path for the autonomous car is feasible.

Implications of solar p-mode frequency shifts

NASA Technical Reports Server (NTRS)

Goldreich, Peter; Murray, Norman; Willette, Gregory; Kumar, Pawan

1991-01-01

An expression is derived that relates solar p-mode frequency shifts to changes in the entropy and magnetic field of the sun. The frequency variations result from changes in path length and propagation speed. Path length changes dominate for entropy perturbations, and propagation speed changes dominate for most types of magnetic field peturbations. The p-mode frequencies increased along with solar activity between 1986 and 1989; these frequency shifts exhibited a rapid rise with increasing frequency followed by a precipitous drop. The positive component of the shifts can be accounted for by variations of the mean square magnetic field strength in the vicinity of the photosphere. The magnetic stress perturbation decays above the top of the convection zone on a length scale comparable to the pressure scale height and grows gradually with depth below. The presence of a resonance in the chromospheric cavity means that the transition layer maintains enough coherence to partially reflect acoustic waves even near cycle maximum.

Development of a Differential Optical Absorption Spectroscopy System Using HighLuminance LED for Measurement of NO2

NASA Astrophysics Data System (ADS)

Fukuchi, Tetsuo; Nayuki, Takuya; Mori, Hideto; Goto, Naohiko; Fujii, Takashi; Nemoto, Koshichi

A differential optical absorption spectroscopy (DOAS) system for measurement of atmospheric NO2 was developed. The system uses a battery-operated, high luminance LED and a fiber-coupled spectrometer, and is portable. Laboratory experiments using a gas cell of length 0.22 m with varying NO2 concentrations were performed to evaluate the sensitivity of the DOAS system. The DOAS measurement results are in agreement with NO2 concentrations obtained simultaneously by a FT-IR (Fourier Transform Infrared) system for NO2 concentrations down to 20 ppm. Experiments with an optical path length of 93 m were also performed, and NO2 concentrations down to 0.20 ppm were measured. Since measurement of atmospheric NO2, which is in the order of several tens of ppb, requires optical path lengths of several hundred m, system improvements to improve the signal detection are necessary.

Long Coherence Length 193 nm Laser for High-Resolution Nano-Fabrication

DTIC Science & Technology

2008-06-27

in the non-linear optical up-converter, as well as specifying their interaction lengths, phase -matching angles, coatings, temperatures of operation...when optical path differences between interfering beams become comparable to the temporal coherence length of the source, the fringe contrast diminishes...switched, intracavity frequency doubled Nd:YAG laser drives an optical parametric oscillator (OPO) running at 710 nm. A portion of the 532 nm light

Operation and Maintenance Manual for Draw Off-Holdback (DOHB) Tension Machine

DTIC Science & Technology

1982-12-01

020-31 DENISON 14 D316127 28 HIDRAULIC RRAKE 2 0316127 29 I ESERVOIR 1 0316390 WGC 2 0316128 EFEENCE ORAINS: 1. WGC OG. NO. 031605 OUTLINE & GENERAL...filter Excessive decompression energy rates Improve decompression control Excessive line capacitance (line volume. Reduce line size or lengths

The desert ant odometer: a stride integrator that accounts for stride length and walking speed.

PubMed

Wittlinger, Matthias; Wehner, Rüdiger; Wolf, Harald

2007-01-01

Desert ants, Cataglyphis, use path integration as a major means of navigation. Path integration requires measurement of two parameters, namely, direction and distance of travel. Directional information is provided by a celestial compass, whereas distance measurement is accomplished by a stride integrator, or pedometer. Here we examine the recently demonstrated pedometer function in more detail. By manipulating leg lengths in foraging desert ants we could also change their stride lengths. Ants with elongated legs ('stilts') or shortened legs ('stumps') take larger or shorter strides, respectively, and misgauge travel distance. Travel distance is overestimated by experimental animals walking on stilts, and underestimated by animals walking on stumps - strongly indicative of stride integrator function in distance measurement. High-speed video analysis was used to examine the actual changes in stride length, stride frequency and walking speed caused by the manipulations of leg length. Unexpectedly, quantitative characteristics of walking behaviour remained almost unaffected by imposed changes in leg length, demonstrating remarkable robustness of leg coordination and walking performance. These data further allowed normalisation of homing distances displayed by manipulated animals with regard to scaling and speed effects. The predicted changes in homing distance are in quantitative agreement with the experimental data, further supporting the pedometer hypothesis.

41 CFR 102-74.485 - Is there any limitation on the length of time of a permit?

Code of Federal Regulations, 2010 CFR

2010-07-01

... on the length of time of a permit? 102-74.485 Section 102-74.485 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT REGULATION REAL... limitation on the length of time of a permit? Yes, a permit may not be issued for a period of time in excess...

41 CFR 102-74.485 - Is there any limitation on the length of time of a permit?

Code of Federal Regulations, 2011 CFR

2011-01-01

... on the length of time of a permit? 102-74.485 Section 102-74.485 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT REGULATION REAL... limitation on the length of time of a permit? Yes, a permit may not be issued for a period of time in excess...

Mechanical properties of asthmatic airway smooth muscle.

PubMed

Chin, Leslie Y M; Bossé, Ynuk; Pascoe, Chris; Hackett, Tillie L; Seow, Chun Y; Paré, Peter D

2012-07-01

Airway smooth muscle (ASM) is the major effector of excessive airway narrowing in asthma. Changes in some of the mechanical properties of ASM could contribute to excessive narrowing and have not been systematically studied in human ASM from nonasthmatic and asthmatic subjects. Human ASM strips (eight asthmatic and six nonasthmatic) were studied at in situ length and force was normalised to maximal force induced by electric field stimulation (EFS). Measurements included: passive and active force versus length before and after length adaptation, the force-velocity relationship, maximal shortening and force recovery after length oscillation. Force was converted to stress by dividing by cross-sectional area of muscle. The only functional differences were that the asthmatic tissue was stiffer at longer lengths (p<0.05) and oscillatory strain reduced isometric force in response to EFS by 19% as opposed to 36% in nonasthmatics (p<0.01). The mechanical properties of human ASM from asthmatic and nonasthmatic subjects are comparable except for increased passive stiffness and attenuated decline in force generation after an oscillatory perturbation. These data may relate to reduced bronchodilation induced by a deep inspiration in asthmatic subjects.

Analytic solution of the Spencer-Lewis angular-spatial moments equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filippone, W.L.

A closed-form solution for the angular-spatial moments of the Spencer-Lewis equation is presented that is valid for infinite homogeneous media. From the moments, the electron density distribution as a function of position and path length (energy) is reconstructed for several sample problems involving plane isotropic sources of electrons in aluminium. The results are in excellent agreement with those determined numerically using the streaming ray method. The primary use of the closed form solution will most likely be to generate accurate electron transport benchmark solutions. In principle, the electron density as a function of space, path length, and direction can bemore » determined for planar sources of arbitrary angular distribution.« less

Solenoid and monocusp ion source

DOEpatents

Brainard, John Paul; Burns, Erskine John Thomas; Draper, Charles Hadley

1997-01-01

An ion source which generates hydrogen ions having high atomic purity incorporates a solenoidal permanent magnets to increase the electron path length. In a sealed envelope, electrons emitted from a cathode traverse the magnetic field lines of a solenoid and a monocusp magnet between the cathode and a reflector at the monocusp. As electrons collide with gas, the molecular gas forms a plasma. An anode grazes the outer boundary of the plasma. Molecular ions and high energy electrons remain substantially on the cathode side of the cusp, but as the ions and electrons are scattered to the aperture side of the cusp, additional collisions create atomic ions. The increased electron path length allows for smaller diameters and lower operating pressures.

Solenoid and monocusp ion source

DOEpatents

Brainard, J.P.; Burns, E.J.T.; Draper, C.H.

1997-10-07

An ion source which generates hydrogen ions having high atomic purity incorporates a solenoidal permanent magnets to increase the electron path length. In a sealed envelope, electrons emitted from a cathode traverse the magnetic field lines of a solenoid and a monocusp magnet between the cathode and a reflector at the monocusp. As electrons collide with gas, the molecular gas forms a plasma. An anode grazes the outer boundary of the plasma. Molecular ions and high energy electrons remain substantially on the cathode side of the cusp, but as the ions and electrons are scattered to the aperture side of the cusp, additional collisions create atomic ions. The increased electron path length allows for smaller diameters and lower operating pressures. 6 figs.

Multipass optical device and process for gas and analyte determination

DOEpatents

Bernacki, Bruce E [Kennewick, WA

2011-01-25

A torus multipass optical device and method are described that provide for trace level determination of gases and gas-phase analytes. The torus device includes an optical cavity defined by at least one ring mirror. The mirror delivers optical power in at least a radial and axial direction and propagates light in a multipass optical path of a predefined path length.

Report on Research

DTIC Science & Technology

1989-06-01

Force systems require a resolved information on the optical thorough understanding of the propaga- extinction coefficient. Measurements of tion path , the...Depolarization as Function of Snow Density. Measurement System ). (It correlated well with the ( Multi -scatter scale length information is usable to extinction ...data on the effect of optically thin cirrus clouds on long - path infrared transmit- tance. Future system designers will have access to this new

Novices in surgery are the target group of a virtual reality training laboratory.

PubMed

Hassan, Iyad; Maschuw, Katja; Rothmund, Matthias; Koller, Michael; Gerdes, Berthold

2006-01-01

This study aims to establish which physicians represent the suitable target group of a virtual training laboratory. Novices (48 physicians with fewer than 10 laparoscopic operations) and intermediate trainees (19 physicians who performed 30-50 laparoscopic operations) participated in this study. Each participant performed the basic module 'clip application' at the beginning and after a 1-hour short training course on the LapSim. The course consisted of the tasks coordination, lift and grasp, clip application, cutting with diathermy and fine dissection at increasing difficulty levels. The time taken to complete the tasks, number of errors, and economy of motion parameters (path length and angular path) were analyzed. Following training with the simulator, novices completed the task significantly faster (p = 0.001), demonstrated a greater economy of motion [path length (p = 0.04) and angular path (p = 0.01)]. In contrast, the intermediate trainees showed a reduction of their errors, but without reaching statistical significance. They showed no improvement in economy of motion and completed the task significantly slower (p = 0.03). Novices, in comparison to intermediate trainees, tend to benefit most during their first exposure to a laparoscopy simulator.

Multi-criteria robustness analysis of metro networks

NASA Astrophysics Data System (ADS)

Wang, Xiangrong; Koç, Yakup; Derrible, Sybil; Ahmad, Sk Nasir; Pino, Willem J. A.; Kooij, Robert E.

2017-05-01

Metros (heavy rail transit systems) are integral parts of urban transportation systems. Failures in their operations can have serious impacts on urban mobility, and measuring their robustness is therefore critical. Moreover, as physical networks, metros can be viewed as topological entities, and as such they possess measurable network properties. In this article, by using network science and graph theory, we investigate ten theoretical and four numerical robustness metrics and their performance in quantifying the robustness of 33 metro networks under random failures or targeted attacks. We find that the ten theoretical metrics capture two distinct aspects of robustness of metro networks. First, several metrics place an emphasis on alternative paths. Second, other metrics place an emphasis on the length of the paths. To account for all aspects, we standardize all ten indicators and plot them on radar diagrams to assess the overall robustness for metro networks. Overall, we find that Tokyo and Rome are the most robust networks. Rome benefits from short transferring and Tokyo has a significant number of transfer stations, both in the city center and in the peripheral area of the city, promoting both a higher number of alternative paths and overall relatively short path-lengths.

14 CFR 23.181 - Dynamic stability.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) During the conditions as specified in § 23.175, when the longitudinal control force required to maintain... response of the airplane must not exhibit any dangerous characteristics nor be excessive in relation to the magnitude of the control force released. Any long-period oscillation of flight path, phugoid oscillation...

Hydrocarbon fluid, ejector refrigeration system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kowalski, G.J.; Foster, A.R.

1993-08-31

A refrigeration system is described comprising: a vapor ejector cycle including a working fluid having a property such that entropy of the working fluid when in a saturated vapor state decreases as pressure decreases, the vapor ejector cycle comprising: a condenser located on a common fluid flow path; a diverter located downstream from the condenser for diverting the working fluid into a primary fluid flow path and a secondary fluid flow path parallel to the primary fluid flow path; an evaporator located on the secondary fluid flow path; an expansion device located on the secondary fluid flow path upstream ofmore » the evaporator; a boiler located on the primary fluid flow path parallel to the evaporator for boiling the working fluid, the boiler comprising an axially extending core region having a substantially constant cross sectional area and a porous capillary region surrounding the core region, the core region extending a length sufficient to produce a near sonic velocity saturated vapor; and an ejector having an outlet in fluid communication with the inlet of the condenser and an inlet in fluid communication with the outlet of the evaporator and the outlet of the boiler and in which the flows of the working fluid from the evaporator and the boiler are mixed and the pressure of the working fluid is increased to at least the pressure of the condenser, the ejector inlet, located downstream from the axially extending core region, including a primary nozzle located sufficiently close to the outlet of the boiler to minimize a pressure drop between the boiler and the primary nozzle, the primary nozzle of the ejector including a converging section having an included angle and length preselected to receive the working fluid from the boiler as a near sonic velocity saturated vapor.« less

Serpentine Ultralong Path with Extended Routing (SUPER) High Resolution Traveling Wave Ion Mobility-MS using Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Liulin; Webb, Ian K.; Garimella, Sandilya V. B.

Ion mobility (IM) separations have a broad range of analytical applications, but insufficient resolution limits many applications. Here we report on traveling wave (TW) ion mobility (IM) separations in a Serpentine Ultra-long Path with Extended Routing (SUPER) Structures for Lossless Ion Manipulations (SLIM) module in conjunction with mass spectrometry (MS). The extended routing utilized multiple passes was facilitated by the introduction of a lossless ion switch at the end of the ion path that either directed ions to the MS detector or to another pass through the serpentine separation region, providing theoretically unlimited TWIM path lengths. Ions were confined inmore » the SLIM by rf fields in conjunction with a DC guard bias, enabling essentially lossless TW transmission over greatly extended paths (e.g., ~1094 meters over 81 passes through the 13.5 m serpentine path). In this multi-pass SUPER TWIM provided resolution approximately proportional to the square root of the number of passes (or path length). More than 30-fold higher IM resolution for Agilent tuning mix m/z 622 and 922 ions (~340 vs. ~10) was achieved for 40 passes compared to commercially available drift tube IM and other TWIM-based platforms. An initial evaluation of the isomeric sugars Lacto-N-hexaose and Lacto-N-neohexaose showed the isomeric structures to be baseline resolved, and a new conformational feature for Lacto-N-neohexaose was revealed after 9 passes. The new SLIM SUPER high resolution TWIM platform has broad utility in conjunction with MS and is expected to enable a broad range of previously challenging or intractable separations.« less

49 CFR 38.29 - Interior circulation, handrails and stanchions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... location from the lift or ramp. (b) Handrails and stanchions shall be provided in the entrance to the... length with front-door lifts or ramps, vertical stanchions immediately behind the driver shall either... of 22 feet in length, the minimum interior height along the path from the lift to the securement...

49 CFR 38.29 - Interior circulation, handrails and stanchions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... location from the lift or ramp. (b) Handrails and stanchions shall be provided in the entrance to the... length with front-door lifts or ramps, vertical stanchions immediately behind the driver shall either... of 22 feet in length, the minimum interior height along the path from the lift to the securement...

Congestion patterns of electric vehicles with limited battery capacity.

PubMed

Jing, Wentao; Ramezani, Mohsen; An, Kun; Kim, Inhi

2018-01-01

The path choice behavior of battery electric vehicle (BEV) drivers is influenced by the lack of public charging stations, limited battery capacity, range anxiety and long battery charging time. This paper investigates the congestion/flow pattern captured by stochastic user equilibrium (SUE) traffic assignment problem in transportation networks with BEVs, where the BEV paths are restricted by their battery capacities. The BEV energy consumption is assumed to be a linear function of path length and path travel time, which addresses both path distance limit problem and road congestion effect. A mathematical programming model is proposed for the path-based SUE traffic assignment where the path cost is the sum of the corresponding link costs and a path specific out-of-energy penalty. We then apply the convergent Lagrangian dual method to transform the original problem into a concave maximization problem and develop a customized gradient projection algorithm to solve it. A column generation procedure is incorporated to generate the path set. Finally, two numerical examples are presented to demonstrate the applicability of the proposed model and the solution algorithm.

Cooperative organic mine avoidance path planning

NASA Astrophysics Data System (ADS)

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

2005-06-01

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.

Congestion patterns of electric vehicles with limited battery capacity

PubMed Central

2018-01-01

The path choice behavior of battery electric vehicle (BEV) drivers is influenced by the lack of public charging stations, limited battery capacity, range anxiety and long battery charging time. This paper investigates the congestion/flow pattern captured by stochastic user equilibrium (SUE) traffic assignment problem in transportation networks with BEVs, where the BEV paths are restricted by their battery capacities. The BEV energy consumption is assumed to be a linear function of path length and path travel time, which addresses both path distance limit problem and road congestion effect. A mathematical programming model is proposed for the path-based SUE traffic assignment where the path cost is the sum of the corresponding link costs and a path specific out-of-energy penalty. We then apply the convergent Lagrangian dual method to transform the original problem into a concave maximization problem and develop a customized gradient projection algorithm to solve it. A column generation procedure is incorporated to generate the path set. Finally, two numerical examples are presented to demonstrate the applicability of the proposed model and the solution algorithm. PMID:29543875

Dysfunctional whole brain networks in mild cognitive impairment patients: an fMRI study

NASA Astrophysics Data System (ADS)

Liu, Zhenyu; Bai, Lijun; Dai, Ruwei; Zhong, Chongguang; Xue, Ting; You, Youbo; Tian, Jie

2012-03-01

Mild cognitive impairment (MCI) was recognized as the prodromal stage of Alzheimer's disease (AD). Recent researches have shown that cognitive and memory decline in AD patients is coupled with losses of small-world attributes. However, few studies pay attention to the characteristics of the whole brain networks in MCI patients. In the present study, we investigated the topological properties of the whole brain networks utilizing graph theoretical approaches in 16 MCI patients, compared with 18 age-matched healthy subjects as a control. Both MCI patients and normal controls showed small-world architectures, with large clustering coefficients and short characteristic path lengths. We detected significantly longer characteristic path length in MCI patients compared with normal controls at the low sparsity. The longer characteristic path lengths in MCI indicated disrupted information processing among distant brain regions. Compared with normal controls, MCI patients showed decreased nodal centrality in the brain areas of the angular gyrus, heschl gyrus, hippocampus and superior parietal gyrus, while increased nodal centrality in the calcarine, inferior occipital gyrus and superior frontal gyrus. These changes in nodal centrality suggested a widespread rewiring in MCI patients, which may be an integrated reflection of reorganization of the brain networks accompanied with the cognitive decline. Our findings may be helpful for further understanding the pathological mechanisms of MCI.

High-precision diode-laser-based temperature measurement for air refractive index compensation.

PubMed

Hieta, Tuomas; Merimaa, Mikko; Vainio, Markku; Seppä, Jeremias; Lassila, Antti

2011-11-01

We present a laser-based system to measure the refractive index of air over a long path length. In optical distance measurements, it is essential to know the refractive index of air with high accuracy. Commonly, the refractive index of air is calculated from the properties of the ambient air using either Ciddor or Edlén equations, where the dominant uncertainty component is in most cases the air temperature. The method developed in this work utilizes direct absorption spectroscopy of oxygen to measure the average temperature of air and of water vapor to measure relative humidity. The method allows measurement of temperature and humidity over the same beam path as in optical distance measurement, providing spatially well-matching data. Indoor and outdoor measurements demonstrate the effectiveness of the method. In particular, we demonstrate an effective compensation of the refractive index of air in an interferometric length measurement at a time-variant and spatially nonhomogeneous temperature over a long time period. Further, we were able to demonstrate 7 mK RMS noise over a 67 m path length using a 120 s sample time. To our knowledge, this is the best temperature precision reported for a spectroscopic temperature measurement. © 2011 Optical Society of America

Spatial and temporal analysis center of pressure displacement during adolescence: Clinical implications of developmental changes.

PubMed

Quatman-Yates, Catherine; Bonnette, Scott; Gupta, Resmi; Hugentobler, Jason A; Wade, Shari L; Glauser, Tracy A; Ittenbach, Richard F; Paterno, Mark V; Riley, Michael A

2018-04-01

This study aimed to provide insight into the development of postural control abilities in youth. A total of 276 typically developing adolescents (155 males, 121 females) with a mean age of 13.23 years (range of 7.11-18.80) were recruited for participation. Subjects performed two-minute quiet standing trials in bipedal stance on a force plate. Center of pressure (COP) trajectories were quantified using Sample Entropy (SampEn) in the anterior-posterior direction (SampEn-AP), SampEn in the medial-lateral direction (SampEn-ML), and Path Length (PL) measures. Three separate linear regression analyses were conducted to predict the relationship between age and each of the response variables after adjusting for individuals' physical characteristics. Linear regression models showed an inverse relationship between age and entropy measures after adjusting for body mass index. Results indicated that chronological age was predictive of entropy and path length patterns. Specifically, older adolescents exhibited center of pressure displacement (smaller path length) and less complex, more regular center of pressure displacement patterns (lower SampEn-AP and SampEn-ML values) compared to the younger children. These findings support prior studies suggesting that developmental changes in postural control abilities may continue throughout adolescence and into adulthood. Copyright © 2018 Elsevier B.V. All rights reserved.

Grey matter networks in people at increased familial risk for schizophrenia.

PubMed

Tijms, Betty M; Sprooten, Emma; Job, Dominic; Johnstone, Eve C; Owens, David G C; Willshaw, David; Seriès, Peggy; Lawrie, Stephen M

2015-10-01

Grey matter brain networks are disrupted in schizophrenia, but it is still unclear at which point during the development of the illness these disruptions arise and whether these can be associated with behavioural predictors of schizophrenia. We investigated if single-subject grey matter networks were disrupted in a sample of people at familial risk of schizophrenia. Single-subject grey matter networks were extracted from structural MRI scans of 144 high risk subjects, 32 recent-onset patients and 36 healthy controls. The following network properties were calculated: size, connectivity density, degree, path length, clustering coefficient, betweenness centrality and small world properties. People at risk of schizophrenia showed decreased path length and clustering in mostly prefrontal and temporal areas. Within the high risk sample, the path length of the posterior cingulate cortex and the betweenness centrality of the left inferior frontal operculum explained 81% of the variance in schizotypal cognitions, which was previously shown to be the strongest behavioural predictor of schizophrenia in the study. In contrast, local grey matter volume measurements explained 48% of variance in schizotypy. The present results suggest that single-subject grey matter networks can quantify behaviourally relevant biological alterations in people at increased risk for schizophrenia before disease onset. Copyright © 2015 Elsevier B.V. All rights reserved.

Graph theoretical analysis of EEG functional connectivity during music perception.

PubMed

Wu, Junjie; Zhang, Junsong; Liu, Chu; Liu, Dongwei; Ding, Xiaojun; Zhou, Changle

2012-11-05

The present study evaluated the effect of music on large-scale structure of functional brain networks using graph theoretical concepts. While most studies on music perception used Western music as an acoustic stimulus, Guqin music, representative of Eastern music, was selected for this experiment to increase our knowledge of music perception. Electroencephalography (EEG) was recorded from non-musician volunteers in three conditions: Guqin music, noise and silence backgrounds. Phase coherence was calculated in the alpha band and between all pairs of EEG channels to construct correlation matrices. Each resulting matrix was converted into a weighted graph using a threshold, and two network measures: the clustering coefficient and characteristic path length were calculated. Music perception was found to display a higher level mean phase coherence. Over the whole range of thresholds, the clustering coefficient was larger while listening to music, whereas the path length was smaller. Networks in music background still had a shorter characteristic path length even after the correction for differences in mean synchronization level among background conditions. This topological change indicated a more optimal structure under music perception. Thus, prominent small-world properties are confirmed in functional brain networks. Furthermore, music perception shows an increase of functional connectivity and an enhancement of small-world network organizations. Copyright © 2012 Elsevier B.V. All rights reserved.

Anogenital distance of women in relation to their mother's gynaecological characteristics before or during pregnancy.

PubMed

Mira-Escolano, María-Pilar; Mendiola, Jaime; Mínguez-Alarcón, Lidia; Roca, Manuela; Cutillas-Tolín, Ana; López-Espín, José J; Torres-Cantero, Alberto M

2014-02-01

Animal models suggest that anogenital distance (AGD) at birth reflects androgen concentrations during in-utero development and predicts adult AGD. Several human observational studies show an association between menstrual cycle irregularities and a hyperandrogenic environment and that may result in a potential alteration of the female reproductive tract during in-utero development. This study examined associations between AGD of young women and their mother's gynaecological characteristics before or during pregnancy. This is cross-sectional study of 100 college-age volunteers in southern Spain. Physical and gynaecological examinations were conducted on the young women and they and their mothers completed epidemiological questionnaires on lifestyles and gynaecological history. Linear regression analysis was used to examine the association between AGD measurements (anus-fourchette (AGDAF) and anus-clitoris (AGDAC)) of women and their mother's gynaecological characteristics. Longer AGDAF was associated with the presence of mother's menstrual cycle irregularities before pregnancy (P=0.03). Longer female AGD has been related to excess androgen exposure in utero in toxicological studies. The current findings may be consistent with studies in which an association between menstrual cycle irregularities and an hyperandrogenic environment has been reported, which therefore may result in a potential modification of the female offspring's reproductive tract during in-utero development, including AGD. Rodent models suggest that perineal length at birth reflects male hormone concentrations (androgens) during in-utero development and predicts adult perineal length. Several human studies show a relationship between menstrual cycle irregularities and an excessive androgen environment. We hypothesize that androgen excess may result in a potential alteration of the female reproductive tract during in-utero development. Our aim was to examine associations between perineal length of young women and their mother's gynaecological characteristics before or during pregnancy. This is a study of 100 college-age volunteers in Southern Spain. Physical and gynaecological examinations were conducted on the young women and they and their mothers completed epidemiological questionnaires on lifestyles and gynaecological history. We used multivariate analyses to assess the association between perineal length of women and their mother's gynaecological characteristics. Longer perineal length was associated with the presence of mother's menstrual cycle irregularities before pregnancy. Longer female perineal length has been related to excess androgen exposure in utero in rodent studies. Our findings may be consistent with previous studies in which an association between menstrual cycle irregularities and an excess of androgen has been reported, which therefore may result in a potential modification of the female offspring's reproductive tract during in-utero development, including perineal length. Copyright © 2013 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

Overestimation of Mach number due to probe shadow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gosselin, J. J.; Thakur, S. C.; Tynan, G. R.

2016-07-15

Comparisons of the plasma ion flow speed measurements from Mach probes and laser induced fluorescence were performed in the Controlled Shear Decorrelation Experiment. We show the presence of the probe causes a low density geometric shadow downstream of the probe that affects the current density collected by the probe in collisional plasmas if the ion-neutral mean free path is shorter than the probe shadow length, L{sub g} = w{sup 2} V{sub drift}/D{sub ⊥}, resulting in erroneous Mach numbers. We then present a simple correction term that provides the corrected Mach number from probe data when the sound speed, ion-neutral mean free path,more » and perpendicular diffusion coefficient of the plasma are known. The probe shadow effect must be taken into account whenever the ion-neutral mean free path is on the order of the probe shadow length in linear devices and the open-field line region of fusion devices.« less

Peculiarities of the statistics of spectrally selected fluorescence radiation in laser-pumped dye-doped random media

NASA Astrophysics Data System (ADS)

Yuvchenko, S. A.; Ushakova, E. V.; Pavlova, M. V.; Alonova, M. V.; Zimnyakov, D. A.

2018-04-01

We consider the practical realization of a new optical probe method of the random media which is defined as the reference-free path length interferometry with the intensity moments analysis. A peculiarity in the statistics of the spectrally selected fluorescence radiation in laser-pumped dye-doped random medium is discussed. Previously established correlations between the second- and the third-order moments of the intensity fluctuations in the random interference patterns, the coherence function of the probe radiation, and the path difference probability density for the interfering partial waves in the medium are confirmed. The correlations were verified using the statistical analysis of the spectrally selected fluorescence radiation emitted by a laser-pumped dye-doped random medium. Water solution of Rhodamine 6G was applied as the doping fluorescent agent for the ensembles of the densely packed silica grains, which were pumped by the 532 nm radiation of a solid state laser. The spectrum of the mean path length for a random medium was reconstructed.

Correlations between psychometric schizotypy, scan path length, fixations on the eyes and face recognition.

PubMed

Hills, Peter J; Eaton, Elizabeth; Pake, J Michael

2016-01-01

Psychometric schizotypy in the general population correlates negatively with face recognition accuracy, potentially due to deficits in inhibition, social withdrawal, or eye-movement abnormalities. We report an eye-tracking face recognition study in which participants were required to match one of two faces (target and distractor) to a cue face presented immediately before. All faces could be presented with or without paraphernalia (e.g., hats, glasses, facial hair). Results showed that paraphernalia distracted participants, and that the most distracting condition was when the cue and the distractor face had paraphernalia but the target face did not, while there was no correlation between distractibility and participants' scores on the Schizotypal Personality Questionnaire (SPQ). Schizotypy was negatively correlated with proportion of time fixating on the eyes and positively correlated with not fixating on a feature. It was negatively correlated with scan path length and this variable correlated with face recognition accuracy. These results are interpreted as schizotypal traits being associated with a restricted scan path leading to face recognition deficits.

Propagation characteristics of partially coherent anomalous elliptical hollow Gaussian beam propagating through atmospheric turbulence along a slant path

NASA Astrophysics Data System (ADS)

Tian, Huanhuan; Xu, Yonggen; Yang, Ting; Ma, Zairu; Wang, Shijian; Dan, Youquan

2017-02-01

Based on the extended Huygens-Fresnel principal and the Wigner distribution function, the root mean square (rms) angular width and propagation factor (M2-factor) of partially coherent anomalous elliptical hollow Gaussian (PCAEHG) beam propagating through atmospheric turbulence along a slant path are studied in detail. Analytical formulae of the rms angular width and M2-factor of PCAEHG beam are derived. Our results show that the rms angular width increases with increasing of wavelength and zenith angle and with decreasing of transverse coherence length, beam waist sizes and inner scale. The M2-factor increases with increasing of zenith angle and with decreasing of wavelength, transverse coherence length, beam waist sizes and inner scale. The saturation propagation distances (SPDs) increase as zenith angle increases. The numerical calculations also indicate that the SPDs of rms angular width and M2-factor for uplink slant paths with zenith angle of π/12 are about 0.2 and 20 km, respectively.

Protonospheric columnar electron content determination. I - Analysis.

NASA Technical Reports Server (NTRS)

Almeida, O. G.

1973-01-01

A combination of phase-path length difference and Faraday rotation angle data obtained from geostationary satellite transmissions is used to determine the integration constant necessary to convert phase-path length difference information into absolute values of total slant columnar electron content. The total content thus determined, which is the sum of the ionospheric and protonospheric contents, is measured with uncertainties about one order of magnitude smaller than the value of the protonospheric content. It is thus, in principle, possible to determine the latter by subtracting from the measurement the so-called 'Faraday content.' This idea, proposed by several authors in the past, is critically examined in the present paper. It is impossible to totally eliminate the ionospheric contribution to the measurements; however, it is shown that the degree of elimination depends on the type of distribution of the longitudinal component of the geomagnetic field along the path of observation. Satisfactory minimization of the ionospheric contribution can be accomplished only under certain geometries of observation.

LapSim virtual reality laparoscopic simulator reflects clinical experience in German surgeons.

PubMed

Langelotz, C; Kilian, M; Paul, C; Schwenk, W

2005-11-01

The aim of this study was to analyze the ability of a training module on a virtual laparoscopic simulator to assess surgical experience in laparoscopy. One hundred and fifteen participants at the 120th annual convent of the German surgical society took part in this study. All participants were stratified into two groups, one with laparoscopic experience of less than 50 operations (group 1, n=61) and one with laparoscopic experience of more than 50 laparoscopic operations (group 2, n=54). All subjects completed a laparoscopic training module consisting of five different exercises for navigation, coordination, grasping, cutting and clipping. The time to perform each task was measured, as were the path lengths of the instruments and their respective angles representing the economy of the movements. Results between groups were compared using chi(2) or Mann-Whitney U-test. Group 1 needed more time for completion of the exercises (median 424 s, range 99-1,376 s) than group 2 (median 315 s, range 168-625 s) (P<0.01). Instrument movements were less economic in group 1 with larger angular pathways, e.g. in the cutting exercise (median 352 degrees , range 104-1,628 degrees vs median 204 degrees , range 107-444 degrees , P<0.01), and longer path lengths (each instrument P<0.05). As time for completion of exercises, instrument path lengths and angular paths are indicators of clinical experience, it can be concluded that laparoscopic skills acquired in the operating room transfer into virtual reality. A laparoscopic simulator can serve as an instrument for the assessment of experience in laparoscopic surgery.

2D beam hardening correction for micro-CT of immersed hard tissue

NASA Astrophysics Data System (ADS)

Davis, Graham; Mills, David

2016-10-01

Beam hardening artefacts arise in tomography and microtomography with polychromatic sources. Typically, specimens appear to be less dense in the center of reconstructions because as the path length through the specimen increases, so the X-ray spectrum is shifted towards higher energies due to the preferential absorption of low energy photons. Various approaches have been taken to reduce or correct for these artefacts. Pre-filtering the X-ray beam with a thin metal sheet will reduce soft energy X-rays and thus narrow the spectrum. Correction curves can be applied to the projections prior to reconstruction which transform measured attenuation with polychromatic radiation to predicted attenuation with monochromatic radiation. These correction curves can be manually selected, iteratively derived from reconstructions (this generally works where density is assumed to be constant) or derived from a priori information about the X-ray spectrum and specimen composition. For hard tissue specimens, the latter approach works well if the composition is reasonably homogeneous. In the case of an immersed or embedded specimen (e.g., tooth or bone) the relative proportions of mineral and "organic" (including medium and plastic container) species varies considerably for different ray paths and simple beam hardening correction does not give accurate results. By performing an initial reconstruction, the total path length through the container can be determined. By modelling the X-ray properties of the specimen, a 2D correction transform can then be created such that the predicted monochromatic attenuation can be derived as a function of both the measured polychromatic attenuation and the container path length.

Determinants of daily path length in black and gold howler monkeys (Alouatta caraya) in northeastern Argentina.

PubMed

Raño, Mariana; Kowalewski, Martin M; Cerezo, Alexis M; Garber, Paul A

2016-08-01

Models used to explain the social organization of primates suggest that variation in daily path length (DPL) is a response to variation in resource distribution and the intensity of intragroup feeding competition. However, daily path length may be affected by a number of other factors including the availability and distribution of nutritionally complementary food items, temperature which can influence activity budget, patterns of subgrouping, and the frequency and function of intergroup encounters. In this 6-month study (total 495 hr of quantitative data), we examined daily path lengths in two neighboring groups of black and gold howler monkeys (Alouatta caraya) inhabiting a semi-deciduous gallery forest in San Cayetano (27° 30'S, 58° 41'W), in the northwest province of Corrientes, Argentina. Both study groups were of similar size and composition. We identified relationships across groups between time spent feeding on fruits, leaves, and flowers, the number of trees visited, group spread, frequency of intergroup encounters, mean daily temperature, and DPL. Our results suggest that variation in food availability had a significant impact on howler ranging behavior by increasing DPL under conditions of high immature and mature fruit availability, and by decreasing DPL with increased availability and increased time invested in feeding on mature leaves. These results do not support the contention that a reduction in food availability or an increase in within-group feeding competition increased DPL in black and gold howler monkeys. DPL in black and gold howlers is influenced by several interrelated factors. In this regard we suggest that models of socio-ecology and ecological constraints need to reconsider how factors such as individual nutritional requirements, social tolerance and group cohesion, and the spatial and temporal availability of preferred and nearby food resources influence primate ranging behavior. Am. J. Primatol. 78:825-837, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

The assessment of postural control and the influence of a secondary task in people with anterior cruciate ligament reconstructed knees using a Nintendo Wii Balance Board.

PubMed

Howells, Brooke E; Clark, Ross A; Ardern, Clare L; Bryant, Adam L; Feller, Julian A; Whitehead, Timothy S; Webster, Kate E

2013-09-01

Postural control impairments may persist following anterior cruciate ligament (ACL) reconstruction. The effect of a secondary task on postural control has, however, not been determined. The purpose of this case-control study was to compare postural control in patients following ACL reconstruction with healthy individuals with and without a secondary task. 45 patients (30 men and 15 women) participated at least 6 months following primary ACL reconstruction surgery. Participants were individually matched by age, gender and sports activity to healthy controls. Postural control was measured using a Nintendo Wii Balance Board and customised software during static single-leg stance and with the addition of a secondary task. The secondary task required participants to match the movement of an oscillating marker by adducting and abducting their arm. Centre of pressure (CoP) path length in both medial-lateral and anterior-posterior directions, and CoP total path length. When compared with the control group, the anterior-posterior path length significantly increased in the ACL reconstruction patients' operated (12.3%, p=0.02) and non-operated limbs (12.8%, p=0.02) for the single-task condition, and the non-operated limb (11.5%, p=0.006) for the secondary task condition. The addition of a secondary task significantly increased CoP path lengths in all measures (p<0.001), although the magnitude of the increase was similar in both the ACL reconstruction and control groups. ACL reconstruction patients showed a reduced ability in both limbs to control the movement of the body in the anterior-posterior direction. The secondary task affected postural control by comparable amounts in patients after ACL reconstruction and healthy controls. Devices for the objective measurement of postural control, such as the one used in this study, may help clinicians to more accurately identify patients with deficits who may benefit from targeted neuromuscular training programs.

Excess Volumes and Excess Isentropic Compressibilities of Binary Liquid Mixtures of Trichloroethylene with Esters at 303.15 K

NASA Astrophysics Data System (ADS)

Ramanaiah, S.; Rao, C. Narasimha; Nagaraja, P.; Venkateswarlu, P.

2015-11-01

Exces volumes, VE, and excess isentropic compressibilities, κSE, have been reported as a function of composition for binary liquid mixtures of trichloroethylene with ethyl acetate, n-propyl acetate, and n-butyl acetate at 303.15 K. Isentropic compressibilities are calculated using measured sound speeds and density data for pure components and for binary mixtures. Excess volumes and excess isentropic compressibilities are found to be negative for the three systems studied over the entire composition range at 303.15 K, whereas these values become more negative with an increase of carbon chain length. The results are discussed in terms of intermolecular interactions between unlike molecules.

Long open-path instrument for simultaneously monitoring of methane, CO2 and water vapor

NASA Astrophysics Data System (ADS)

Simeonov, Valentin; Parlange, Marc

2013-04-01

A new, long open-path instrument for monitoring of path-averaged methane, CO2 and water vapor concentrations will be presented. The instrument is built on the monostatic scheme (transceiver -distant retroreflector). A VCSEL with a central wavelength of 1654 nm is used as a light source. The receiver is built around a 20 cm Newtonian telescope. The design optical path length is 2000 m but can be further extended. To avoid distortions in the shape of the spectral lines caused by atmospheric turbulences they are scanned within 1 µs. The expected concentration resolution for the above mentioned path length is of the order of 2 ppb for methane, 100 ppb for CO2 and 100 ppm for water vapor. The instrument is developed at the Swiss Federal Institute of Technology - Lausanne (EPFL) Switzerland and will be used within the GAW+ CH program for long-term monitoring of background methane and CO2 concentrations in the Swiss Alps. The initial calibration validation tests at EPFL were completed in December 2012 and the instrument will be installed at the beginning of 2013 at the High Altitude Research Station Jungfraujoch (HARSJ). The HARSJ is located at 3580 m ASL and is one of the 24 global GAW stations. One of the goals of the project is to compare path-averaged to the ongoing point measurements of methane in order to identify possible influence of the station. Future deployments of a copy of the instrument include the Canadian arctic and Siberian wetlands. The instrument can be used for ground truthing of satellite observation as well.

Mounting Debt

ERIC Educational Resources Information Center

Fullerton, Jon

2004-01-01

The long economic boom enabled school districts nationwide to fund expensive reforms and hefty pay raises. Now, however, they are finding it nearly impossible to cut costs and balance their budgets. The specific path to financial distress is unique in each case. Any number of factors, from excessively generous concessions at the bargaining table…

Time of day: A vital determinant in diet-induced cardiometabolic syndrome development

USDA-ARS?s Scientific Manuscript database

Excess caloric intake is strongly associated with the development of obesity, type 2 diabetes mellitus, and cardiovascular disease (CVD). Research efforts have focused attention primarily on the quality (i.e., nutritional content) and/or quantity of calories as potential causes for diet-induced path...

On the Distribution of Free Path Lengthsfor the Periodic Lorentz Gas

NASA Astrophysics Data System (ADS)

Bourgain, Jean; Golse, François; Wennberg, Bernt

Consider the domain and let the free path length be defined as The distribution of values of is studied in the limit as for all . It is shown that the value is critical for this problem: in other words, the limiting behavior of depends only on whether γ is larger or smaller than .

Vertical Scales of Turbulence at the Mount Wilson Observatory

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.; Lowe, Stephen T.; Bester, Manfred; Danchi, William C.; Townes, Charles H.

1995-01-01

The vertical scales of turbulence at the Mount Wilson Observatory are inferred from data from the University of California at Berkeley Infrared Spatial Interferometer (ISI), by modeling path length fluctuations observed in the interferometric paths to celestial objects and those in instrumental ground-based paths. The correlations between the stellar and ground-based path length fluctuations and the temporal statistics of those fluctuations are modeled on various timescales to constrain the vertical scales. A Kolmogorov-Taylor turbulence model with a finite outer scale was used to simulate ISI data. The simulation also included the white instrumental noise of the interferometer, aperture-filtering effects, and the data analysis algorithms. The simulations suggest that the path delay fluctuations observed in the 1992-1993 ISI data are largely consistent with being generated by refractivity fluctuations at two characteristic vertical scales: one extending to a height of 45 m above the ground, with a wind speed of about 1 m/ s, and another at a much higher altitude, with a wind speed of about 10 m/ s. The height of the lower layer is of the order of the dimensions of trees and other structures near the interferometer, which suggests that these objects, including elements of the interferometer, may play a role in generating the lower layer of turbulence. The modeling indicates that the high- attitude component contributes primarily to short-period (less than 10 s) fluctuations, while the lower component dominates the long-period (up to a few minutes) fluctuations. The lower component turbulent height, along with outer scales of the order of 10 m, suggest that the baseline dependence of long-term interferometric, atmospheric fluctuations should weaken for baselines greater than a few tens of meters. Simulations further show that there is the potential for improving the seeing or astrometric accuracy by about 30%-50% on average, if the path length fluctuations in the lower component are directly calibrated. Statistical and systematic effects induce an error of about 15 m in the estimate of the lower component turbulent altitude.

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

ERIC Educational Resources Information Center

Hwang, Hyekyung; Steinhauer, Karsten

2011-01-01

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…

Apparatus and method for compensating for electron beam emittance in synchronizing light sources

DOEpatents

Neil, George R.

1996-01-01

A focused optical beam is used to change the path length of the core electrons in electron light sources thereby boosting their efficiency of conversion of electron beam energy to light. Both coherent light in the free electron laser and incoherent light in the synchrotron is boosted by this technique. By changing the path length of the core electrons by the proper amount, the core electrons are caused to stay in phase with the electrons in the outer distribution of the electron beam. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron.

Apparatus and method for compensating for electron beam emittance in synchronizing light sources

DOEpatents

Neil, G.R.

1996-07-30

A focused optical beam is used to change the path length of the core electrons in electron light sources thereby boosting their efficiency of conversion of electron beam energy to light. Both coherent light in the free electron laser and incoherent light in the synchrotron is boosted by this technique. By changing the path length of the core electrons by the proper amount, the core electrons are caused to stay in phase with the electrons in the outer distribution of the electron beam. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron. 4 figs.

Radiative transport equation for the Mittag-Leffler path length distribution

NASA Astrophysics Data System (ADS)

Liemert, André; Kienle, Alwin

2017-05-01

In this paper, we consider the radiative transport equation for infinitely extended scattering media that are characterized by the Mittag-Leffler path length distribution p (ℓ ) =-∂ℓEα(-σtℓα ) , which is a generalization of the usually assumed Lambert-Beer law p (ℓ ) =σtexp(-σtℓ ) . In this context, we derive the infinite-space Green's function of the underlying fractional transport equation for the spherically symmetric medium as well as for the one-dimensional string. Moreover, simple analytical solutions are presented for the prediction of the radiation field in the single-scattering approximation. The resulting equations are compared with Monte Carlo simulations in the steady-state and time domain showing, within the stochastic nature of the simulations, an excellent agreement.

Interferometer with Continuously Varying Path Length Measured in Wavelengths to the Reference Mirror

NASA Technical Reports Server (NTRS)

Ohara, Tetsuo (Inventor)

2016-01-01

An interferometer in which the path length of the reference beam, measured in wavelengths, is continuously changing in sinusoidal fashion and the interference signal created by combining the measurement beam and the reference beam is processed in real time to obtain the physical distance along the measurement beam between the measured surface and a spatial reference frame such as the beam splitter. The processing involves analyzing the Fourier series of the intensity signal at one or more optical detectors in real time and using the time-domain multi-frequency harmonic signals to extract the phase information independently at each pixel position of one or more optical detectors and converting the phase information to distance information.

Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser

NASA Astrophysics Data System (ADS)

Davis, N. M.; Hodgkinson, J.; Francis, D.; Tatam, R. P.

2016-04-01

Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration.

Femto-second synchronisation with a waveguide interferometer

NASA Astrophysics Data System (ADS)

Dexter, A. C.; Smith, S. J.; Woolley, B. J.; Grudiev, A.

2018-03-01

CERN's compact linear collider CLIC requires crab cavities on opposing linacs to rotate bunches of particles into alignment at the interaction point (IP). These cavities are located approximately 25 metres either side of the IP. The luminosity target requires synchronisation of their RF phases to better than 5 fs r.m.s. This is to be achieved by powering both cavities from one high power RF source, splitting the power and delivering it along two waveguide paths that are controlled to be identical in length to within a micrometre. The waveguide will be operated as an interferometer. A high power phase shifter for adjusting path lengths has been successfully developed and operated in an interferometer. The synchronisation target has been achieved in a low power prototype system.

Robot path planning using a genetic algorithm

NASA Technical Reports Server (NTRS)

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

1988-01-01

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

Path planning for persistent surveillance applications using fixed-wing unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Keller, James F.

This thesis addresses coordinated path planning for fixed-wing Unmanned Aerial Vehicles (UAVs) engaged in persistent surveillance missions. While uniquely suited to this mission, fixed wing vehicles have maneuver constraints that can limit their performance in this role. Current technology vehicles are capable of long duration flight with a minimal acoustic footprint while carrying an array of cameras and sensors. Both military tactical and civilian safety applications can benefit from this technology. We make three main contributions: C1 A sequential path planner that generates a C 2 flight plan to persistently acquire a covering set of data over a user designated area of interest. The planner features the following innovations: • A path length abstraction that embeds kino-dynamic motion constraints to estimate feasible path length. • A Traveling Salesman-type planner to generate a covering set route based on the path length abstraction. • A smooth path generator that provides C 2 routes that satisfy user specified curvature constraints. C2 A set of algorithms to coordinate multiple UAVs, including mission commencement from arbitrary locations to the start of a coordinated mission and de-confliction of paths to avoid collisions with other vehicles and fixed obstacles. C3 A numerically robust toolbox of spline-based algorithms tailored for vehicle routing validated through flight test experiments on multiple platforms. A variety of tests and platforms are discussed. The algorithms presented are based on a technical approach with approximately equal emphasis on analysis, computation, dynamic simulation, and flight test experimentation. Our planner (C1) directly takes into account vehicle maneuverability and agility constraints that could otherwise render simple solutions infeasible. This is especially important when surveillance objectives elevate the importance of optimized paths. Researchers have developed a diverse range of solutions for persistent surveillance applications but few directly address dynamic maneuver constraints. The key feature of C1 is a two stage sequential solution that discretizes the problem so that graph search techniques can be combined with parametric polynomial curve generation. A method to abstract the kino-dynamics of the aerial platforms is then presented so that a graph search solution can be adapted for this application. An A* Traveling Salesman Problem (TSP) algorithm is developed to search the discretized space using the abstract distance metric to acquire more data or avoid obstacles. Results of the graph search are then transcribed into smooth paths based on vehicle maneuver constraints. A complete solution for a single vehicle periodic tour of the area is developed using the results of the graph search algorithm. To execute the mission, we present a simultaneous arrival algorithm (C2) to coordinate execution by multiple vehicles to satisfy data refresh requirements and to ensure there are no collisions at any of the path intersections. We present a toolbox of spline-based algorithms (C3) to streamline the development of C2 continuous paths with numerical stability. These tools are applied to an aerial persistent surveillance application to illustrate their utility. Comparisons with other parametric polynomial approaches are highlighted to underscore the benefits of the B-spline framework. Performance limits with respect to feasibility constraints are documented.

Distributed multiple path routing in complex networks

NASA Astrophysics Data System (ADS)

Chen, Guang; Wang, San-Xiu; Wu, Ling-Wei; Mei, Pan; Yang, Xu-Hua; Wen, Guang-Hui

2016-12-01

Routing in complex transmission networks is an important problem that has garnered extensive research interest in the recent years. In this paper, we propose a novel routing strategy called the distributed multiple path (DMP) routing strategy. For each of the O-D node pairs in a given network, the DMP routing strategy computes and stores multiple short-length paths that overlap less with each other in advance. And during the transmission stage, it rapidly selects an actual routing path which provides low transmission cost from the pre-computed paths for each transmission task, according to the real-time network transmission status information. Computer simulation results obtained for the lattice, ER random, and scale-free networks indicate that the strategy can significantly improve the anti-congestion ability of transmission networks, as well as provide favorable routing robustness against partial network failures.

CORRECTING FOR INTERPLANETARY SCATTERING IN VELOCITY DISPERSION ANALYSIS OF SOLAR ENERGETIC PARTICLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laitinen, T.; Dalla, S.; Huttunen-Heikinmaa, K.

2015-06-10

To understand the origin of Solar Energetic Particles (SEPs), we must study their injection time relative to other solar eruption manifestations. Traditionally the injection time is determined using the Velocity Dispersion Analysis (VDA) where a linear fit of the observed event onset times at 1 AU to the inverse velocities of SEPs is used to derive the injection time and path length of the first-arriving particles. VDA does not, however, take into account that the particles that produce a statistically observable onset at 1 AU have scattered in the interplanetary space. We use Monte Carlo test particle simulations of energeticmore » protons to study the effect of particle scattering on the observable SEP event onset above pre-event background, and consequently on VDA results. We find that the VDA results are sensitive to the properties of the pre-event and event particle spectra as well as SEP injection and scattering parameters. In particular, a VDA-obtained path length that is close to the nominal Parker spiral length does not imply that the VDA injection time is correct. We study the delay to the observed onset caused by scattering of the particles and derive a simple estimate for the delay time by using the rate of intensity increase at the SEP onset as a parameter. We apply the correction to a magnetically well-connected SEP event of 2000 June 10, and show it to improve both the path length and injection time estimates, while also increasing the error limits to better reflect the inherent uncertainties of VDA.« less

Use of a bite registration vinyl polysiloxane material to identify denture flange overextension and/or excessive border thickness in removable prosthodontics.

PubMed

Haeberle, C Brent; Abreu, Amara; Metzler, Kurt

2015-01-01

Vinyl polysiloxane (VPS) has multiple applications in prosthodontics. This article describes how a bite registration fast-set VPS material was used to identify length overextension and/or excessive border thickness of denture flanges. In addition, the advantages of VPS over conventional materials are presented.

Path planning and execution monitoring for a planetary rover

NASA Technical Reports Server (NTRS)

Gat, Erann; Slack, Marc G.; Miller, David P.; Firby, R. James

1990-01-01

A path planner and an execution monitoring planner that will enable the rover to navigate to its various destinations safely and correctly while detecting and avoiding hazards are described. An overview of the complete architecture is given. Implementation and testbeds are described. The robot can detect unforseen obstacles and take appropriate action. This includes having the rover back away from the hazard and mark the area as untraversable in the in the rover's internal map. The experiments have consisted of paths roughly 20 m in length. The architecture works with a large variety of rover configurations with different kinematic constraints.

Codification of scan path parameters and development of perimeter scan strategies for 3D bowl-shaped laser forming

NASA Astrophysics Data System (ADS)

Tavakoli, A.; Naeini, H. Moslemi; Roohi, Amir H.; Gollo, M. Hoseinpour; Shahabad, Sh. Imani

2018-01-01

In the 3D laser forming process, developing an appropriate laser scan pattern for producing specimens with high quality and uniformity is critical. This study presents certain principles for developing scan paths. Seven scan path parameters are considered, including: (1) combined linear or curved path; (2) type of combined linear path; (3) order of scan sequences; (4) the position of the start point in each scan; (5) continuous or discontinuous scan path; (6) direction of scan path; and (7) angular arrangement of combined linear scan paths. Regarding these path parameters, ten combined linear scan patterns are presented. Numerical simulations show continuous hexagonal, scan pattern, scanning from outer to inner path, is the optimized. In addition, it is observed the position of the start point and the angular arrangement of scan paths is the most effective path parameters. Also, further experimentations show four sequences due to creat symmetric condition enhance the height of the bowl-shaped products and uniformity. Finally, the optimized hexagonal pattern was compared with the similar circular one. In the hexagonal scan path, distortion value and standard deviation rather to edge height of formed specimen is very low, and the edge height despite of decreasing length of scan path increases significantly compared to the circular scan path. As a result, four-sequence hexagonal scan pattern is proposed as the optimized perimeter scan path to produce bowl-shaped product.

Prey vulnerability to peacock cichlids and largemouth bass based on predator gape and prey body depth

USGS Publications Warehouse

Hill, Jeffrey E.; Nico, Leo G.; Cichra, Charles E.; Gilbert, Carter R.

2005-01-01

The interaction of prey fish body depth and predator gape size may produce prey assemblages dominated by invulnerable prey and excessive prey-to-predator biomass ratios. Peacock cichlids (Cichla ocellaris) were stocked into southeast Florida canals to consume excess prey fish biomass, particularly spotted tilapia (Tilapia mariae). The ecomorphologically similar largemouth bass (Micropterus salmoides) was already present in the canals. We present relations of length-specific gape size for peacock cichlids and largemouth bass. Both predators have broadly overlapping gape size, but largemouth bass ?126 mm total length have slightly larger gape sizes than peacock cichlids of the same length. Also, we experimentally tested the predictions of maximum prey size for peacock cichlids and determined that a simple method of measuring gape size used for largemouth bass also is appropriate for peacock cichlids. Lastly, we determined relations of body depth and length of prey species to investigate relative vulnerability. Using a simple predator-prey model and length frequencies of predators and bluegill (Lepomis macrochirus), redear sunfish (Lepomis microlophus), and spotted tilapia prey, we documented that much of the prey biomass in southeast Florida canals is unavailable for largemouth bass and peacock cichlid predation.

Area, length and thickness conservation: Dogma or reality?

NASA Astrophysics Data System (ADS)

Moretti, Isabelle; Callot, Jean Paul

2012-08-01

The basic assumption of quantitative structural geology is the preservation of material during deformation. However the hypothesis of volume conservation alone does not help to predict past or future geometries and so this assumption is usually translated into bed length in 2D (or area in 3D) and thickness conservation. When subsurface data are missing, geologists may extrapolate surface data to depth using the kink-band approach. These extrapolations, preserving both thicknesses and dips, lead to geometries which are restorable but often erroneous, due to both disharmonic deformation and internal deformation of layers. First, the Bolivian Sub-Andean Zone case is presented to highlight the evolution of the concepts on which balancing is based, and the important role played by a decoupling level in enhancing disharmony. Second, analogue models are analyzed to test the validity of the balancing techniques. Chamberlin's excess area approach is shown to be on average valid. However, neither the length nor the thicknesses are preserved. We propose that in real cases, the length preservation hypothesis during shortening could also be a wrong assumption. If the data are good enough to image the decollement level, the Chamberlin excess area method could be used to compute the bed length changes.

Mixed quantum-classical studies of energy partitioning in unimolecular chemical reactions

NASA Astrophysics Data System (ADS)

Bladow, Landon Lowell

A mixed quantum-classical reaction path Hamiltonian method is utilized to study the dynamics of unimolecular reactions. The method treats motion along the reaction path classically and treats the transverse vibrations quantum mechanically. The theory leads to equations that predict the disposai of the exit-channel potential energy to product translation and vibration. In addition, vibrational state distributions are obtained for the product normal modes. Vibrational excitation results from the curvature of the minimum energy reaction path. The method is applied to six unimolecular reactions: HF elimination from fluoroethane, 1,1-difluoroethane, 1,1-difluoroethene, and trifluoromethane; and HCl elimination from chloroethane and acetyl chloride. The minimum energy paths were calculated at either the MP2 or B3LYP level of theory. In all cases, the majority of the vibrational excitation of the products occurs in the HX fragment. The results are compared to experimental data and other theoretical results, where available. The best agreement between the experimental and calculated HX vibrational distributions is found for the halogenated ethanes, and the experimental deduction that the majority of the HX vibrational excitation arises from the potential energy release is supported. It is believed that the excess energy provided in experiments contributes to the poorer agreement between experiment and theory observed for HF elimination from 1,1-difluoroethene and trifluoromethane. An attempt is described to incorporate a treatment of the excess energy into the present method. However, the sign of the curvature coupling elements is then found to affect the dynamics. Overall, the method appears to be an efficient dynamical tool for modeling the disposal of the exit-channel potential energy in unimolecular reactions.

Simultaneous retrieval of atmospheric CO2 and light path modification from space-based spectroscopic observations of greenhouse gases: methodology and application to GOSAT measurements over TCCON sites.

PubMed

Oshchepkov, Sergey; Bril, Andrey; Yokota, Tatsuya; Yoshida, Yukio; Blumenstock, Thomas; Deutscher, Nicholas M; Dohe, Susanne; Macatangay, Ronald; Morino, Isamu; Notholt, Justus; Rettinger, Markus; Petri, Christof; Schneider, Matthias; Sussman, Ralf; Uchino, Osamu; Velazco, Voltaire; Wunch, Debra; Belikov, Dmitry

2013-02-20

This paper presents an improved photon path length probability density function method that permits simultaneous retrievals of column-average greenhouse gas mole fractions and light path modifications through the atmosphere when processing high-resolution radiance spectra acquired from space. We primarily describe the methodology and retrieval setup and then apply them to the processing of spectra measured by the Greenhouse gases Observing SATellite (GOSAT). We have demonstrated substantial improvements of the data processing with simultaneous carbon dioxide and light path retrievals and reasonable agreement of the satellite-based retrievals against ground-based Fourier transform spectrometer measurements provided by the Total Carbon Column Observing Network (TCCON).

Logarithmic Sobolev Inequalities on Path Spaces Over Riemannian Manifolds

NASA Astrophysics Data System (ADS)

Hsu, Elton P.

Let Wo(M) be the space of paths of unit time length on a connected, complete Riemannian manifold M such that γ(0) =o, a fixed point on M, and ν the Wiener measure on Wo(M) (the law of Brownian motion on M starting at o).If the Ricci curvature is bounded by c, then the following logarithmic Sobolev inequality holds:

Improved gaseous leak detector

DOEpatents

Juravic, F.E. Jr.

1983-10-06

In a short path length mass-spectrometer type of helium leak detector wherein the helium trace gas is ionized, accelerated and deflected onto a particle counter, an arrangement is provided for converting the detector to neon leak detection. The magnetic field of the deflection system is lowered so as to bring the nonlinear fringe area of the magnetic field across the ion path, thereby increasing the amount of deflection of the heavier neon ions.

Gaseous leak detector

DOEpatents

Juravic, Jr., Frank E.

1988-01-01

In a short path length mass-spectrometer type of helium leak detector wherein the helium trace gas is ionized, accelerated and deflected onto a particle counter, an arrangement is provided for converting the detector to neon leak detection. The magnetic field of the deflection system is lowered so as to bring the non linear fringe area of the magnetic field across the ion path, thereby increasing the amount of deflection of the heavier neon ions.

Network Design for Reliability and Resilience to Attack

DTIC Science & Technology

2014-03-01

attacker can destroy n arcs in the network SPNI Shortest-Path Network-Interdiction problem TSP Traveling Salesman Problem UB upper bound UKR Ukraine...elimination from the traveling salesman problem (TSP). Literature calls a walk that does not contain a cycle a path [19]. The objective function in...arc lengths as random variables with known probability distributions. The m-median problem seeks to design a network with minimum average travel cost

Integrating cell on chip—Novel waveguide platform employing ultra-long optical paths

NASA Astrophysics Data System (ADS)

Fohrmann, Lena Simone; Sommer, Gerrit; Pitruzzello, Giampaolo; Krauss, Thomas F.; Petrov, Alexander Yu.; Eich, Manfred

2017-09-01

Optical waveguides are the most fundamental building blocks of integrated optical circuits. They are extremely well understood, yet there is still room for surprises. Here, we introduce a novel 2D waveguide platform which affords a strong interaction of the evanescent tail of a guided optical wave with an external medium while only employing a very small geometrical footprint. The key feature of the platform is its ability to integrate the ultra-long path lengths by combining low propagation losses in a silicon slab with multiple reflections of the guided wave from photonic crystal (PhC) mirrors. With a reflectivity of 99.1% of our tailored PhC-mirrors, we achieve interaction paths of 25 cm within an area of less than 10 mm2. This corresponds to 0.17 dB/cm effective propagation which is much lower than the state-of-the-art loss of approximately 1 dB/cm of single mode silicon channel waveguides. In contrast to conventional waveguides, our 2D-approach leads to a decay of the guided wave power only inversely proportional to the optical path length. This entirely different characteristic is the major advantage of the 2D integrating cell waveguide platform over the conventional channel waveguide concepts that obey the Beer-Lambert law.

An in vitro comparison of root canal transportation by reciproc file with and without glide path.

PubMed

Nazarimoghadam, Kiumars; Daryaeian, Mohammad; Ramazani, Nahid

2014-09-01

The aim of ideal canal preparation is to prevent iatrogenic aberrations such as transportation. The aim of this study was to evaluate the root canal transportation by Reciproc file with and without glide path. Thirty acrylic-resin blocks with a curvature of 60° and size#10 (2% taper) were assigned into two groups (n= 15). In group 1, the glide path was performed using stainless steel k-files size#10 and 15 at working length In group 2, canals were prepared with Reciproc file system at working length. By using digital imaging software (AutoCAD 2008), the pre-instrumentation and post-instrumentation digital images were superimposed over, taking the landmarks as reference points. Then the radius of the internal and external curve of the specimens was calculated at three α, β and γ points (1mm to apex as α, 3mm to apex as β, and 5mm to apex as γ). The data were statically analyzed using the independent T-test and Mann-Whitney U test by SPSS version 16. Glide path was found significant for only external curve in the apical third of the canal; that is, 5mm to apex (P=0.005). But in the other third, canal modification was not significant (P> 0.008). Canal transportation in the apical third of the canal seems to be significantly reduced when glide path is performed using reciprocating files.

An In Vitro Comparison of Root Canal Transportation by Reciproc File With and Without Glide Path

PubMed Central

Nazarimoghadam, Kiumars; Daryaeian, Mohammad; Ramazani, Nahid

2014-01-01

Objective: The aim of ideal canal preparation is to prevent iatrogenic aberrations such as transportation. The aim of this study was to evaluate the root canal transportation by Reciproc file with and without glide path. Materials and Methods: Thirty acrylic-resin blocks with a curvature of 60° and size#10 (2% taper) were assigned into two groups (n= 15). In group 1, the glide path was performed using stainless steel k-files size#10 and 15 at working length In group 2, canals were prepared with Reciproc file system at working length. By using digital imaging software (AutoCAD 2008), the pre-instrumentation and post-instrumentation digital images were superimposed over, taking the landmarks as reference points. Then the radius of the internal and external curve of the specimens was calculated at three α, β and γ points (1mm to apex as α, 3mm to apex as β, and 5mm to apex as γ). The data were statically analyzed using the independent T-test and Mann-Whitney U test by SPSS version 16. Results: Glide path was found significant for only external curve in the apical third of the canal; that is, 5mm to apex (P=0.005). But in the other third, canal modification was not significant (P> 0.008). Conclusion: Canal transportation in the apical third of the canal seems to be significantly reduced when glide path is performed using reciprocating files. PMID:25628682

Analysis and elimination of a bias in targeted molecular dynamics simulations of conformational transitions: application to calmodulin.

PubMed

Ovchinnikov, Victor; Karplus, Martin

2012-07-26

The popular targeted molecular dynamics (TMD) method for generating transition paths in complex biomolecular systems is revisited. In a typical TMD transition path, the large-scale changes occur early and the small-scale changes tend to occur later. As a result, the order of events in the computed paths depends on the direction in which the simulations are performed. To identify the origin of this bias, and to propose a method in which the bias is absent, variants of TMD in the restraint formulation are introduced and applied to the complex open ↔ closed transition in the protein calmodulin. Due to the global best-fit rotation that is typically part of the TMD method, the simulated system is guided implicitly along the lowest-frequency normal modes, until the large spatial scales associated with these modes are near the target conformation. The remaining portion of the transition is described progressively by higher-frequency modes, which correspond to smaller-scale rearrangements. A straightforward modification of TMD that avoids the global best-fit rotation is the locally restrained TMD (LRTMD) method, in which the biasing potential is constructed from a number of TMD potentials, each acting on a small connected portion of the protein sequence. With a uniform distribution of these elements, transition paths that lack the length-scale bias are obtained. Trajectories generated by steered MD in dihedral angle space (DSMD), a method that avoids best-fit rotations altogether, also lack the length-scale bias. To examine the importance of the paths generated by TMD, LRTMD, and DSMD in the actual transition, we use the finite-temperature string method to compute the free energy profile associated with a transition tube around a path generated by each algorithm. The free energy barriers associated with the paths are comparable, suggesting that transitions can occur along each route with similar probabilities. This result indicates that a broad ensemble of paths needs to be calculated to obtain a full description of conformational changes in biomolecules. The breadth of the contributing ensemble suggests that energetic barriers for conformational transitions in proteins are offset by entropic contributions that arise from a large number of possible paths.

Optical mapping of prefrontal brain connectivity and activation during emotion anticipation.

PubMed

Wang, Meng-Yun; Lu, Feng-Mei; Hu, Zhishan; Zhang, Juan; Yuan, Zhen

2018-09-17

Accumulated neuroimaging evidence shows that the dorsal lateral prefrontal cortex (dlPFC) is activated during emotion anticipation. The aim of this work is to examine the brain connectivity and activation differences in dlPFC between the positive, neutral and negative emotion anticipation by using functional near-infrared spectroscopy (fNIRS). The hemodynamic responses were first assessed for all subjects during the performance of various emotion anticipation tasks. And then small-world analysis was performed, in which the small-world network indicators including the clustering coefficient, average path length, average node degree, and measure of small-world index were calculated for the functional brain networks associated with the positive, neutral and negative emotion anticipation, respectively. We discovered that compared to negative and neutral emotion anticipation, the positive one exhibited enhanced brain activation in the left dlPFC. Although the functional brain networks for the three emotion anticipation cases manifested the small-world properties regarding the clustering coefficient, average path length, average node degree, and measure of small-world index, the positive one showed significantly higher clustering coefficient and shorter average path length than those from the neutral and negative cases. Consequently, the small-world network indicators and brain activation in dlPPC were able to distinguish well between the positive, neutral and negative emotion anticipation. Copyright © 2018 Elsevier B.V. All rights reserved.

Construct validity and expert benchmarking of the haptic virtual reality dental simulator.

PubMed

Suebnukarn, Siriwan; Chaisombat, Monthalee; Kongpunwijit, Thanapohn; Rhienmora, Phattanapon

2014-10-01

The aim of this study was to demonstrate construct validation of the haptic virtual reality (VR) dental simulator and to define expert benchmarking criteria for skills assessment. Thirty-four self-selected participants (fourteen novices, fourteen intermediates, and six experts in endodontics) at one dental school performed ten repetitions of three mode tasks of endodontic cavity preparation: easy (mandibular premolar with one canal), medium (maxillary premolar with two canals), and hard (mandibular molar with three canals). The virtual instrument's path length was registered by the simulator. The outcomes were assessed by an expert. The error scores in easy and medium modes accurately distinguished the experts from novices and intermediates at the onset of training, when there was a significant difference between groups (ANOVA, p<0.05). The trend was consistent until trial 5. From trial 6 on, the three groups achieved similar scores. No significant difference was found between groups at the end of training. Error score analysis was not able to distinguish any group at the hard level of training. Instrument path length showed a difference in performance according to groups at the onset of training (ANOVA, p<0.05). This study established construct validity for the haptic VR dental simulator by demonstrating its discriminant capabilities between that of experts and non-experts. The experts' error scores and path length were used to define benchmarking criteria for optimal performance.

Alpha-spectrometry and fractal analysis of surface micro-images for characterisation of porous materials used in manufacture of targets for laser plasma experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aushev, A A; Barinov, S P; Vasin, M G

2015-06-30

We present the results of employing the alpha-spectrometry method to determine the characteristics of porous materials used in targets for laser plasma experiments. It is shown that the energy spectrum of alpha-particles, after their passage through porous samples, allows one to determine the distribution of their path length in the foam skeleton. We describe the procedure of deriving such a distribution, excluding both the distribution broadening due to statistical nature of the alpha-particle interaction with an atomic structure (straggling) and hardware effects. The fractal analysis of micro-images is applied to the same porous surface samples that have been studied bymore » alpha-spectrometry. The fractal dimension and size distribution of the number of the foam skeleton grains are obtained. Using the data obtained, a distribution of the total foam skeleton thickness along a chosen direction is constructed. It roughly coincides with the path length distribution of alpha-particles within a range of larger path lengths. It is concluded that the combined use of the alpha-spectrometry method and fractal analysis of images will make it possible to determine the size distribution of foam skeleton grains (or pores). The results can be used as initial data in theoretical studies on propagation of the laser and X-ray radiation in specific porous samples. (laser plasma)« less

The Optimal Capital Stock and Consumption Evolution for Non Zero Consumers Growth Rate in the Framework of Ramsey Model on Finite Horizon

NASA Astrophysics Data System (ADS)

Bonchiş, N.; Balint, Şt.

2010-09-01

In this paper the Ramsey optimal growth of the capital stock and consumption on finite horizon is analyzed when the growth rate of consumers is strictly positive. The main purpose is to establish the dependence of the optimal capital stock and consumption evolution on the growth rate of consumers. The analysis reveals: for any initial value k0≥0 there exists a unique optimal evolution path of length N+1 for the capital stock; if k0 is strictly positive then all the elements of the optimal capital stock evolution path are strictly positives except the last one which is zero; the optimal capital stock evolution of length N+1 starting from k0≥0 satisfies the Euler equation; the value function VN is strictly increasing, strictly concave and continuous on R+. The family of functions {VN-T}T = 0…N-1 satisfies the Bellman equation and it is the unique solution of this equation which is both continuous and satisfies the transversality condition. The Mangasarian Lemma is also satisfied. For N tending to infinity the optimal evolution path of length N of the capital stock tends to those on the infinite time horizon. For any k0>0 the value function in k0 decreases when the consumers growth rate increases.

Deconstructing Jaco: genetic heritage of an Afrikaner.

PubMed

Greeff, J M

2007-09-01

It is often assumed that Afrikaners stem from a small number of Dutch immigrants. As a result they should be genetically homogeneous, show founder effects and be rather inbred. By disentangling my own South African pedigree, that is on average 12 generations deep, I try to quantify the genetic heritage of an Afrikaner. As much as 6% of my genes have been contributed by slaves from Africa, Madagascar and India, and a woman from China. This figure compares well to other genetic and genealogical estimates. Seventy three percent of my lineages coalesce into common founders, and I am related in excess of 10 times to 20 founder ancestors (30 times to Willem Schalk van der Merwe). Significant founder effects are thus possible. The overrepresentation of certain founder ancestors is in part explained by the fact that they had more children. This is remarkable given that they lived more than 300 years (or 12 generations) ago. DECONSTRUCT, a new program for pedigree analysis, identified 125 common ancestors in my pedigree. However, these common ancestors are so distant from myself, paths of between 16 and 25 steps in length, that my inbreeding coefficient is not unusually high (f approximately 0.0019).

System and Method for Measuring the Transfer Function of a Guided Wave Device

NASA Technical Reports Server (NTRS)

Froggatt, Mark E. (Inventor); Erdogan, Turan (Inventor)

2002-01-01

A method/system are provided for measuring the NxN scalar transfer function elements for an N-port guided wave device. Optical energy of a selected wavelength is generated at a source and directed along N reference optical paths having N reference path lengths. Each reference optical path terminates in one of N detectors such that N reference signals are produced at the N detectors. The reference signals are indicative of amplitude, phase and frequency of the optical energy carried along the N reference optical paths. The optical energy from the source is also directed to the N-ports of the guided wave device and then on to each of the N detectors such that N measurement optical paths are defined between the source and each of the N detectors. A portion of the optical energy is modified in terms of at least one of the amplitude and phase to produce N modified signals at each of the N detectors. At each of the N detectors, each of the N modified signals is combined with a corresponding one of the N reference signals to produce corresponding N combined signals at each of the N detectors. A total of N(sup 2) measurement signals are generated by the N detectors. Each of the N(sup 2) measurement signals is sampled at a wave number increment (Delta)k so that N(sup 2) sampled signals are produced. The NxN transfer function elements are generated using the N(sup 2) sampled signals. Reference and measurement path length constraints are defined such that the N combined signals at each of the N detectors are spatially separated from one another in the time domain.

29 CFR 1915.112 - Ropes, chains and slings.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., defective welds, deformation and increase in length or stretch. (3) Employers must note interlink wear, not accompanied by stretch in excess of 5 percent, and remove the chain from service when maximum allowable wear... shall be removed from service when, due to stretch, the increase in length of a measured section exceeds...

29 CFR 1915.112 - Ropes, chains and slings.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., defective welds, deformation and increase in length or stretch. (3) Employers must note interlink wear, not accompanied by stretch in excess of 5 percent, and remove the chain from service when maximum allowable wear... shall be removed from service when, due to stretch, the increase in length of a measured section exceeds...

29 CFR 1915.112 - Ropes, chains and slings.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., defective welds, deformation and increase in length or stretch. (3) Employers must note interlink wear, not accompanied by stretch in excess of 5 percent, and remove the chain from service when maximum allowable wear... shall be removed from service when, due to stretch, the increase in length of a measured section exceeds...

Pulse stretcher

DOEpatents

Horton, J.A.

1994-05-03

Apparatus for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse is disclosed. The apparatus uses a White cell having a plurality of optical delay paths of successively increasing number of passes between the field mirror and the objective mirrors. A pulse from a laser travels through a multi-leg reflective path between a beam splitter and a totally reflective mirror to the laser output. The laser pulse is also simultaneously injected through the beam splitter to the input mirrors of the optical delay paths. The pulses from the output mirrors of the optical delay paths go simultaneously to the laser output and to the input mirrors of the longer optical delay paths. The beam splitter is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output. 6 figures.

Tectonic tests of proposed polar wander paths for Mars and the moon

NASA Technical Reports Server (NTRS)

Grimm, R. E.; Solomon, S. C.

1986-01-01

A comparison of the lithospheric stress field predicted for rapid global reorientations against observed tectonic features is used to test the polar wander paths proposed for Mars by Schultz and Lutz-Garihan (1981). A calculation of the reorientation stresses leads to the suggestion that the formation of normal faults or graben in broad regions around the former rotation poles should be the minimum tectonic signature of a reorientation that generates lithospheric stresses in excess of the extensional strength of near-surface material. It is concluded that polar wander of the magnitude and timing envisioned by Schultz and Lutz-Garihan did not occur.

The Effect of a Short-Term and Long-Term Whole-Body Vibration in Healthy Men upon the Postural Stability

PubMed Central

Piecha, Magdalena; Juras, Grzegorz; Król, Piotr; Sobota, Grzegorz; Polak, Anna; Bacik, Bogdan

2014-01-01

The study aimed to establish the short-term and long-term effects of whole-body vibration on postural stability. The sample consisted of 28 male subjects randomly allocated to four comparative groups, three of which exercised on a vibration platform with parameters set individually for the groups. The stabilographic signal was recorded before the test commenced, after a single session of whole-body vibration, immediately after the last set of exercises of the 4-week whole-body vibration training, and one week after the training ended. The subjects were exposed to vibrations 3 times a week for 4 weeks. Long-term vibration training significantly shortened the rambling and trembling paths in the frontal plane. The path lengths were significantly reduced in the frontal plane one week after the training end date. Most changes in the values of the center of pressure (COP) path lengths in the sagittal and frontal plane were statistically insignificant. We concluded that long-term vibration training improves the postural stability of young healthy individuals in the frontal plane. PMID:24520362

Design of visible and IR infrared dual-band common-path telescope system

NASA Astrophysics Data System (ADS)

Guo, YuLin; Yu, Xun; Tao, Yu; Jiang, Xu

2018-01-01

The use of visible and IR infrared dual-band combination can effectively improve the performance of photoelectric detection system,TV and IR system were designed with the common path by the common reflection optical system.A TV/IR infrared common-caliber and common-path system is designed,which can realize the Remote and all-day information.For the 640×512 cooled focal plane array,an infrared middle wave system was presented with a focal length of 600mm F number of 4 field of view(FOV) of 0.38°×0.43°, the system uses optical passive thermal design, has o compact structure and can meet 100% cold shield efficiency,meanwhile it meets the design requirements of lightweight and athermalization. For the 1920×1080 pixels CCD,a visible (TV) system ,which had 500mm focal length, 4F number,was completed.The final optical design along with their modulation transfer function is presented,showing excellent imaging performance in dual-band at the temperature range between -40° and 60°.

Correlations and path analysis among agronomic and technological traits of upland cotton.

PubMed

Farias, F J C; Carvalho, L P; Silva Filho, J L; Teodoro, P E

2016-08-12

To date, path analysis has been used with the aim of breeding different cultures. However, for cotton, there have been few studies using this analysis, and all of these have used fiber productivity as the primary dependent variable. Therefore, the aim of the present study was to identify agronomic and technological properties that can be used as criteria for direct and indirect phenotypes in selecting cotton genotypes with better fibers. We evaluated 16 upland cotton genotypes in eight trials conducted during the harvest 2008/2009 in the State of Mato Grosso, using a randomized block design with four replicates. The evaluated traits were: plant height, average boll weight, percentage of fiber, cotton seed yield, fiber length, uniformity of fiber, short fiber index, fiber strength, elongation, maturity of the fibers, micronaire, reflectance, and the degree of yellowing. Phenotypic correlations between the traits and cotton fiber yield (main dependent variable) were unfolded in direct and indirect effects through path analysis. Fiber strength, uniformity of fiber, and reflectance were found to influence fiber length, and therefore, these traits are recommended for both direct and indirect selection of cotton genotypes.

Path length entropy analysis of diastolic heart sounds.

PubMed

Griffel, Benjamin; Zia, Mohammad K; Fridman, Vladamir; Saponieri, Cesare; Semmlow, John L

2013-09-01

Early detection of coronary artery disease (CAD) using the acoustic approach, a noninvasive and cost-effective method, would greatly improve the outcome of CAD patients. To detect CAD, we analyze diastolic sounds for possible CAD murmurs. We observed diastolic sounds to exhibit 1/f structure and developed a new method, path length entropy (PLE) and a scaled version (SPLE), to characterize this structure to improve CAD detection. We compare SPLE results to Hurst exponent, Sample entropy and Multiscale entropy for distinguishing between normal and CAD patients. SPLE achieved a sensitivity-specificity of 80%-81%, the best of the tested methods. However, PLE and SPLE are not sufficient to prove nonlinearity, and evaluation using surrogate data suggests that our cardiovascular sound recordings do not contain significant nonlinear properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

Method and source for producing a high concentration of positively charged molecular hydrogen or deuterium ions

DOEpatents

Ehlers, Kenneth W.; Leung, Ka-Ngo

1988-01-01

A high concentration of positive molecular ions of hydrogen or deuterium gas is extracted from a positive ion source having a short path length of extracted ions, relative to the mean free path of the gas molecules, to minimize the production of other ion species by collision between the positive ions and gas molecules. The ion source has arrays of permanent magnets to produce a multi-cusp magnetic field in regions remote from the plasma grid and the electron emitters, for largely confining the plasma to the space therebetween. The ion source has a chamber which is short in length, relative to its transverse dimensions, and the electron emitters are at an even shorter distance from the plasma grid, which contains one or more extraction apertures.

Attosecond-resolution Hong-Ou-Mandel interferometry.

PubMed

Lyons, Ashley; Knee, George C; Bolduc, Eliot; Roger, Thomas; Leach, Jonathan; Gauger, Erik M; Faccio, Daniele

2018-05-01

When two indistinguishable photons are each incident on separate input ports of a beamsplitter, they "bunch" deterministically, exiting via the same port as a direct consequence of their bosonic nature. This two-photon interference effect has long-held the potential for application in precision measurement of time delays, such as those induced by transparent specimens with unknown thickness profiles. However, the technique has never achieved resolutions significantly better than the few-femtosecond (micrometer) scale other than in a common-path geometry that severely limits applications. We develop the precision of Hong-Ou-Mandel interferometry toward the ultimate limits dictated by statistical estimation theory, achieving few-attosecond (or nanometer path length) scale resolutions in a dual-arm geometry, thus providing access to length scales pertinent to cell biology and monoatomic layer two-dimensional materials.

Quantum snake walk on graphs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosmanis, Ansis

2011-02-15

I introduce a continuous-time quantum walk on graphs called the quantum snake walk, the basis states of which are fixed-length paths (snakes) in the underlying graph. First, I analyze the quantum snake walk on the line, and I show that, even though most states stay localized throughout the evolution, there are specific states that most likely move on the line as wave packets with momentum inversely proportional to the length of the snake. Next, I discuss how an algorithm based on the quantum snake walk might potentially be able to solve an extended version of the glued trees problem, whichmore » asks to find a path connecting both roots of the glued trees graph. To the best of my knowledge, no efficient quantum algorithm solving this problem is known yet.« less

Path Length Entropy Analysis of Diastolic Heart Sounds

PubMed Central

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

2013-01-01

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

Preoperative fasting: knowledge and perceptions.

PubMed

Baril, Patrice; Portman, Harriet

2007-10-01

Preoperative patient fasting is an essential element of the patient preparation process, but patients may be fasting for excessive lengths of time. Investigators at one facility used semi-structured interviews to explore the knowledge and beliefs of patients, nurses, and anesthesia care providers regarding the practice of preoperative patient fasting. Findings indicate that some patients had excessive fasting times, and practitioners had erroneous perceptions about patient knowledge regarding the rationale for fasting and compliance with instructions. Clinicians expressed concern about the effects of excessive fasting but were reluctant to relax the policy.

Dynamic path planning for autonomous driving on various roads with avoidance of static and moving obstacles

NASA Astrophysics Data System (ADS)

Hu, Xuemin; Chen, Long; Tang, Bo; Cao, Dongpu; He, Haibo

2018-02-01

This paper presents a real-time dynamic path planning method for autonomous driving that avoids both static and moving obstacles. The proposed path planning method determines not only an optimal path, but also the appropriate acceleration and speed for a vehicle. In this method, we first construct a center line from a set of predefined waypoints, which are usually obtained from a lane-level map. A series of path candidates are generated by the arc length and offset to the center line in the s - ρ coordinate system. Then, all of these candidates are converted into Cartesian coordinates. The optimal path is selected considering the total cost of static safety, comfortability, and dynamic safety; meanwhile, the appropriate acceleration and speed for the optimal path are also identified. Various types of roads, including single-lane roads and multi-lane roads with static and moving obstacles, are designed to test the proposed method. The simulation results demonstrate the effectiveness of the proposed method, and indicate its wide practical application to autonomous driving.

UAV path planning using artificial potential field method updated by optimal control theory

NASA Astrophysics Data System (ADS)

Chen, Yong-bo; Luo, Guan-chen; Mei, Yue-song; Yu, Jian-qiao; Su, Xiao-long

2016-04-01

The unmanned aerial vehicle (UAV) path planning problem is an important assignment in the UAV mission planning. Based on the artificial potential field (APF) UAV path planning method, it is reconstructed into the constrained optimisation problem by introducing an additional control force. The constrained optimisation problem is translated into the unconstrained optimisation problem with the help of slack variables in this paper. The functional optimisation method is applied to reform this problem into an optimal control problem. The whole transformation process is deduced in detail, based on a discrete UAV dynamic model. Then, the path planning problem is solved with the help of the optimal control method. The path following process based on the six degrees of freedom simulation model of the quadrotor helicopters is introduced to verify the practicability of this method. Finally, the simulation results show that the improved method is more effective in planning path. In the planning space, the length of the calculated path is shorter and smoother than that using traditional APF method. In addition, the improved method can solve the dead point problem effectively.

Traveling salesman problem with a center.

PubMed

Lipowski, Adam; Lipowska, Dorota

2005-06-01

We study a traveling salesman problem where the path is optimized with a cost function that includes its length L as well as a certain measure C of its distance from the geometrical center of the graph. Using simulated annealing (SA) we show that such a problem has a transition point that separates two phases differing in the scaling behavior of L and C, in efficiency of SA, and in the shape of minimal paths.

3D seismic analysis of the gas hydrate system and the fluid migration paths in part of the Niger Delta Basin, Nigeria

NASA Astrophysics Data System (ADS)

Akinsanpe, Olumuyiwa T.; Adepelumi, Adekunle A.; Benjamin, Uzochukwu K.; Falebita, Dele E.

2017-12-01

Comprehensive qualitative and semi-quantitative seismic analysis was carried out on 3-dimensional seismic data acquired in the deepwater compressional and shale diapiric zone of the Niger Delta Basin using an advanced seismic imaging tool. The main aim of this work is to obtain an understanding of the forming mechanism of the gas hydrate system, and the fluid migration paths associated with this part of the basin. The results showed the presence of pockmarks on the seafloor and bottom simulating reflectors (BSRs) in the field, indicating the active fluid flux and existence of gas hydrate system in the area. In the area of approximately 195 km2 occupying nearly 24% of the entire study field, three major zones with continuous or discontinuous BSRs of 3 to 7 km in length which are in the northeastern, southern and eastern part of the field respectively were delineated. The BSR is interpreted to be the transition between the free gas zone and the gas hydrate zone. The geologic structures including faults (strike-slip and normal faults), chimneys and diapirs were deduced to be the main conduits for gas migration. It is concluded that the biogenic gases generated in the basin were possibly transported via faults and chimneys by advection processes and subsequently accumulated under low temperature and high pressure conditions in the free gas zone below the BSR forming gas hydrate. A plausible explanation for the presence of the ubiquitous pockmarks of different diameters and sizes in the area is the transportation of the excessive gas to the seafloor through these mapped geologic structures.

Effect of canal length and curvature on working length alteration with WaveOne reciprocating files.

PubMed

Berutti, Elio; Chiandussi, Giorgio; Paolino, Davide Salvatore; Scotti, Nicola; Cantatore, Giuseppe; Castellucci, Arnaldo; Pasqualini, Damiano

2011-12-01

This study evaluated the working length (WL) modification after instrumentation with WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) reciprocating files and the incidence of overinstrumentation in relation to the initial WL. Thirty-two root canals of permanent teeth were used. The angles of curvature of the canals were calculated on digital radiographs. The initial WL with K-files was transferred to the matched WaveOne Primary reciprocating files. After glide paths were established with PathFile (Dentsply Maillefer, Ballaigues, Switzerland), canals were shaped with WaveOne Primary referring to the initial WL. The difference between the postinstrumentation canal length and the initial canal length was analyzed by using a fiberoptic inspection microscope. Data were analyzed with a balanced 2-way factorial analysis of variance (P < .05). Referring to the initial WL, 24 of 32 WaveOne Primary files projected beyond the experimental apical foramen (minimum-maximum, 0.14-0.76 mm). A significant decrease in the canal length after instrumentation (95% confidence interval ranging from -0.34 mm to -0.26 mm) was detected. The canal curvature significantly influenced the WL variation (F(1) = 30.65, P < .001). The interaction between the initial canal length and the canal curvature was statistically significant (F(2) = 4.38, P = .014). Checking the WL before preparation of the apical third of the root canal is recommended when using the new WaveOne NiTi single-file system. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Active feedforward noise control and signal tracking of headsets: Electroacoustic analysis and system implementation.

PubMed

Bai, Mingsian R; Pan, Weichi; Chen, Hungyu

2018-03-01

Active noise control (ANC) of headsets is revisited in this paper. An in-depth electroacoustic analysis of the combined loudspeaker-cavity headset system is conducted on the basis of electro-mechano-acoustical analogous circuits. Model matching of the primary path and the secondary path leads to a feedforward control architecture. The ideal controller sheds some light on the key parameters that affect the noise reduction performance. Filtered-X least-mean-squares algorithm is employed to implement the feedforward controller on a digital signal processor. Since the relative delay of the primary path and the secondary path is crucial to the noise reduction performance, multirate signal processing with polyphase implementation is utilized to minimize the effective analog-digital conversion delay in the secondary path. Ad hoc decimation and interpolation filters are designed in order not to introduce excessive phase delays at the cutoff. Real-time experiments are undertaken to validate the implemented ANC system. Listening tests are also conducted to compare the fixed controller and the adaptive controller in terms of noise reduction and signal tracking performance for three noise types. The results have demonstrated that the fixed feedforward controller achieved satisfactory noise reduction performance and signal tracking quality.

Effect of Glide Path Creating on Cyclic Fatigue Resistance of Reciproc and Reciproc Blue Nickel-titanium Files: A Laboratory Study.

PubMed

Özyürek, Taha; Uslu, Gülşah; Yılmaz, Koray; Gündoğar, Mustafa

2018-06-01

The purpose of this article was to compare the cyclic fatigue resistance of Reciproc and Reciproc Blue files (VDW GmbH, Munich, Germany) that were used to prepare root canals of mandibular molar teeth with or without a glide path. Sixty Reciproc R25 and 60 Reciproc Blue R25 files were used. The Reciproc and Reciproc Blue groups were divided into 3 subgroups (ie, as received condition, used without a glide path, and used with a glide path). All the instruments were rotated in a stainless steel artificial canal with an inner diameter of 1.5 mm, a 60° angle of curvature, and a radius of curvature of 5 mm until fracture occurred. The number of cycle to fracture was calculated, and the length of the fractured segments was measured. The Kruskal-Wallis test was performed to statistically analyze the data using SPSS 21.0 software (IBM Corp, Armonk, NY) at a 5% significance level. The cyclic fatigue resistance of as received condition Reciproc Blue files was found to be higher than as received condition Reciproc files (P < .05). Reciproc Blue files used for root canal preparation showed higher cyclic fatigue resistance than Reciproc files used for root canal preparation (P < .05). There was no statistically significant difference between Reciproc and Reciproc Blue files used with a glide path and without a glide path (P > .05). There was no statistically significant difference in the mean length of the fractured fragments of the instruments (P > .05). Within the limitations of this in vitro study, it was concluded that creating a glide path using ProGlider files had no effect on the cyclic fatigue resistance of RPC and RPC Blue files. Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Statistical analysis of measured free-space laser signal intensity over a 2.33 km optical path.

PubMed

Tunick, Arnold

2007-10-17

Experimental research is conducted to determine the characteristic behavior of high frequency laser signal intensity data collected over a 2.33 km optical path. Results focus mainly on calculated power spectra and frequency distributions. In addition, a model is developed to calculate optical turbulence intensity (C(n)/2) as a function of receiving and transmitting aperture diameter, log-amplitude variance, and path length. Initial comparisons of calculated to measured C(n)/2 data are favorable. It is anticipated that this kind of signal data analysis will benefit laser communication systems development and testing at the U.S. Army Research Laboratory (ARL) and elsewhere.

Path-integral theory of an axially confined worm-like chain

NASA Astrophysics Data System (ADS)

Smith, D. A.

2001-06-01

A path-integral formulation is developed for the thermodynamic properties of a worm-like chain moving on a surface and laterally confined by a harmonic potential. The free energy of the chain is calculated as a function of its length and boundary conditions at each end. Distribution functions for chain displacements can be constructed by utilizing the Markov property as a function of displacement φ(s) and its derivative dφ(s)/ds along the path. These quantities are also calculated in the presence of pinning sites which impose fixed positive or negative displacements, foreshadowing their application to a model for the regulation of striated muscle.

Effective pathway of charge transfer in DNA duplex

NASA Astrophysics Data System (ADS)

Kim, Seongjin; Yi, Juyeon; Hwang, Sun-Yong

2009-03-01

We examine the most efficient route for charge propagation in DNA duplex. We find a direct path along one strand and a detour using the complementary strand compete with each other. Charge tends to take the path along the strand whose energy levels are close to its energy, and yet there exists a crossover length Nc so that for a transfer over a distance shorter than Nc the direct path is always advantageous. We obtain the analytic results for the behavior together with various decay types such as a constant decay, an exponential decay, and a crossover between them, whose validity is confirmed by the numerical calculation.

Remote atmospheric probing by ground to ground line of sight optical methods

NASA Technical Reports Server (NTRS)

Lawrence, R. S.

1969-01-01

The optical effects arising from refractive-index variations in the clear air are qualitatively described, and the possibilities are discussed of using those effects for remotely sensing the physical properties of the atmosphere. The effects include scintillations, path length fluctuations, spreading of a laser beam, deflection of the beam, and depolarization. The physical properties that may be measured include the average temperature along the path, the vertical temperature gradient, and the distribution along the path of the strength of turbulence and the transverse wind velocity. Line-of-sight laser beam methods are clearly effective in measuring the average properties, but less effective in measuring distributions along the path. Fundamental limitations to the resolution are pointed out and experiments are recommended to investigate the practicality of the methods.

Multiscale simulations of patchy particle systems combining Molecular Dynamics, Path Sampling and Green's Function Reaction Dynamics

NASA Astrophysics Data System (ADS)

Bolhuis, Peter

Important reaction-diffusion processes, such as biochemical networks in living cells, or self-assembling soft matter, span many orders in length and time scales. In these systems, the reactants' spatial dynamics at mesoscopic length and time scales of microns and seconds is coupled to the reactions between the molecules at microscopic length and time scales of nanometers and milliseconds. This wide range of length and time scales makes these systems notoriously difficult to simulate. While mean-field rate equations cannot describe such processes, the mesoscopic Green's Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. The recently developed multiscale Molecular Dynamics Green's Function Reaction Dynamics (MD-GFRD) approach combines GFRD for simulating the system at the mesocopic scale where particles are far apart, with microscopic Molecular (or Brownian) Dynamics, for simulating the system at the microscopic scale where reactants are in close proximity. The association and dissociation of particles are treated with rare event path sampling techniques. I will illustrate the efficiency of this method for patchy particle systems. Replacing the microscopic regime with a Markov State Model avoids the microscopic regime completely. The MSM is then pre-computed using advanced path-sampling techniques such as multistate transition interface sampling. I illustrate this approach on patchy particle systems that show multiple modes of binding. MD-GFRD is generic, and can be used to efficiently simulate reaction-diffusion systems at the particle level, including the orientational dynamics, opening up the possibility for large-scale simulations of e.g. protein signaling networks.

[Bioelectric brain activity in patients with neurotic disorders].

PubMed

Golubev, V L; Korabel'nikova, E A; Kudriavtseva, E P

2006-01-01

Seventy-three patients with neurotic disorders, aged 14-35 years, and 33 healthy controls have been examined using electroencephalographic method with spectral analysis of EEG, which has been conducted on the Brain Surfing system by the algorithm of direct Fourier transformation. The patients had changes of brain electric activity manifesting as insufficiency of thalamo-cortical synchronizing systems that caused an excessive activating effect of reticular formation on the cortex realized through extrathalamic reticular cortical and septo-hippocampal activation paths. Determinative in electrophysiological brain organization was the theta-rhythm, a marker of excessive emotional and autonomic activation, which directly correlated with an extent of personality accentuation and severity of neurotic state.

Vehicle path-planning in three dimensions using optics analogs for optimizing visibility and energy cost

NASA Technical Reports Server (NTRS)

Rowe, Neil C.; Lewis, David H.

1989-01-01

Path planning is an important issue for space robotics. Finding safe and energy-efficient paths in the presence of obstacles and other constraints can be complex although important. High-level (large-scale) path planning for robotic vehicles was investigated in three-dimensional space with obstacles, accounting for: (1) energy costs proportional to path length; (2) turn costs where paths change trajectory abruptly; and (3) safety costs for the danger associated with traversing a particular path due to visibility or invisibility from a fixed set of observers. Paths optimal with respect to these cost factors are found. Autonomous or semi-autonomous vehicles were considered operating either in a space environment around satellites and space platforms, or aircraft, spacecraft, or smart missiles operating just above lunar and planetary surfaces. One class of applications concerns minimizing detection, as for example determining the best way to make complex modifications to a satellite without being observed by hostile sensors; another example is verifying there are no paths (holes) through a space defense system. Another class of applications concerns maximizing detection, as finding a good trajectory between mountain ranges of a planet while staying reasonably close to the surface, or finding paths for a flight between two locations that maximize the average number of triangulation points available at any time along the path.

Length adaptation of airway smooth muscle.

PubMed

Bossé, Ynuk; Sobieszek, Apolinary; Paré, Peter D; Seow, Chun Y

2008-01-01

Many types of smooth muscle, including airway smooth muscle (ASM), are capable of generating maximal force over a large length range due to length adaptation, which is a relatively rapid process in which smooth muscle regains contractility after experiencing a force decrease induced by length fluctuation. Although the underlying mechanism is unclear, it is believed that structural malleability of smooth muscle cells is essential for the adaptation to occur. The process is triggered by strain on the cell cytoskeleton that results in a series of yet undefined biochemical and biophysical events leading to restructuring of the cytoskeleton and contractile apparatus and consequently optimization of the overlap between the myosin and actin filaments. Although length adaptability is an intrinsic property of smooth muscle, maladaptation of ASM could result in excessive constriction of the airways and the inability of deep inspirations to dilate them. In this article, we describe the phenomenon of length adaptation in ASM and some possible underlying mechanisms that involve the myosin filament assembly and disassembly. We discuss a possible role of maladaptation of ASM in the pathogenesis of asthma. We believe that length adaptation in ASM is mediated by specific proteins and their posttranslational regulations involving covalent modifications, such as phosphorylation. The discovery of these molecules and the processes that regulate their activity will greatly enhance our understanding of the basic mechanisms of ASM contraction and will suggest molecular targets to alleviate asthma exacerbation related to excessive constriction of the airways.

Transmission experiment of elastic waves with short wavelengths through a highly porous sand soil during water injection

NASA Astrophysics Data System (ADS)

Nakayama, M.; Kawakata, H.; Hirano, S.; Doi, I.; Takahashi, N.

2016-12-01

Transmitted waves at high frequencies attenuate strongly through highly porous media such as shallow ground, although the waves enable us to investigate physical properties of the media with high-spatial resolutions. Nakayama et al. (2015, AGU) tried to investigate the spatio-temporal variations in physical properties of a highly porous sand soil during water injection in laboratory. Accelerometers installed in the sand soil received only the signals of no higher than 0.5 kHz, although they used rectangular waveforms as input signals. The wavelength corresponding to 0.5 kHz is about 400 mm because the measured wave velocity is about 200 m/s. The wavelength is comparable to the path lengths of the transmitted waves, so that it cannot be discussed how the temporal variations in physical properties depend on the paths. In this study, we try to transmit waves with wavelengths much shorter than a sand soil and path lengths through a highly porous sand soil. We make a sand soil (750 mm long, 300 mm wide, and 300 mm high) with porosity about 40%. We install a shaker as a wave source at a deep part in the sand soil. In addition, we install accelerometers, pore pressure gauges, and electrodes at different depths. We inject tap water into the sand soil from the bottom, and record transmitted waves together with pore pressure and electrode voltage until the sand soil becomes saturated. Note that we adopt sweep signals (0.1-10 kHz) as the source so that the shaker can generate high frequency waves more strongly than rectangular signals. Accelerometers receive the signals at least up to 5 kHz during the experiment (Figure 1). The wavelength corresponding to 5 kHz is about 40 mm. In conclusion, we succeed in detecting transmitted waves propagating through the highly porous sand soil whose path lengths are about ten times their wave lengths. Acknowledgment: We are grateful to Takayoshi Kishida for supporting the experiment. This work is supported by JSPS KAKENHI Grant Numbers JP15H02996 and 26750135.

Use of Nintendo Wii Balance Board for posturographic analysis of Multiple Sclerosis patients with minimal balance impairment.

PubMed

Severini, Giacomo; Straudi, Sofia; Pavarelli, Claudia; Da Roit, Marco; Martinuzzi, Carlotta; Di Marco Pizzongolo, Laura; Basaglia, Nino

2017-03-11

The Wii Balance Board (WBB) has been proposed as an inexpensive alternative to laboratory-grade Force Plates (FP) for the instrumented assessment of balance. Previous studies have reported a good validity and reliability of the WBB for estimating the path length of the Center of Pressure. Here we extend this analysis to 18 balance related features extracted from healthy subjects (HS) and individuals affected by Multiple Sclerosis (MS) with minimal balance impairment. Eighteen MS patients with minimal balance impairment (Berg Balance Scale 53.3 ± 3.1) and 18 age-matched HS were recruited in this study. All subjects underwent instrumented balance tests on the FP and WBB consisting of quiet standing with the eyes open and closed. Linear correlation analysis and Bland-Altman plots were used to assess relations between path lengths estimated using the WBB and the FP. 18 features were extracted from the instrumented balance tests. Statistical analysis was used to assess significant differences between the features estimated using the WBB and the FP and between HS and MS. The Spearman correlation coefficient was used to evaluate the validity and the Intraclass Correlation Coefficient was used to assess the reliability of WBB measures with respect to the FP. Classifiers based on Support Vector Machines trained on the FP and WBB features were used to assess the ability of both devices to discriminate between HS and MS. We found a significant linear relation between the path lengths calculated from the WBB and the FP indicating an overestimation of these parameters in the WBB. We observed significant differences in the path lengths between FP and WBB in most conditions. However, significant differences were not found for the majority of the other features. We observed the same significant differences between the HS and MS populations across the two measurement systems. Validity and reliability were moderate-to-high for all the analyzed features. Both the FP and WBB trained classifier showed similar classification performance (>80%) when discriminating between HS and MS. Our results support the observation that the WBB, although not suitable for obtaining absolute measures, could be successfully used in comparative analysis of different populations.

46 CFR 42.20-65 - Sheer.

Code of Federal Regulations, 2010 CFR

2010-10-01

... freeboard deck shall not be taken into account. (7) Where an enclosed poop or forecastle is of standard... allowances may be granted for excess sheer forward. (4) Where sheer credit is given for a poop or forecastle... at the end ordinate. L′=mean enclosed length of poop or forecastle up to a maximum length of 0.5L. L...

Tree-centered spot firing - a technique for prescribed burning beneath standing trees.

Treesearch

C. Phillip Weatherspoon; George A. Almond; Carl N. Skinner

1989-01-01

Prescribed burning beneath standing trees normally requires efforts to protect residual trees from excessive fire damage. Damage to both crowns and boles is strongly influenced by flame length, a fire characteristic functionally related to fireline intensity (Albini 1976). In a good prescribed burn, therefore, the prescription specifies desired or maximum flame lengths...

Network analysis reveals disrupted functional brain circuitry in drug-naive social anxiety disorder.

PubMed

Yang, Xun; Liu, Jin; Meng, Yajing; Xia, Mingrui; Cui, Zaixu; Wu, Xi; Hu, Xinyu; Zhang, Wei; Gong, Gaolang; Gong, Qiyong; Sweeney, John A; He, Yong

2017-12-07

Social anxiety disorder (SAD) is a common and disabling condition characterized by excessive fear and avoidance of public scrutiny. Psychoradiology studies have suggested that the emotional and behavior deficits in SAD are associated with abnormalities in regional brain function and functional connectivity. However, little is known about whether intrinsic functional brain networks in patients with SAD are topologically disrupted. Here, we collected resting-state fMRI data from 33 drug-naive patients with SAD and 32 healthy controls (HC), constructed functional networks with 34 predefined regions based on previous meta-analytic research with task-based fMRI in SAD, and performed network-based statistic and graph-theory analyses. The network-based statistic analysis revealed a single connected abnormal circuitry including the frontolimbic circuit (termed the "fear circuit", including the dorsolateral prefrontal cortex, ventral medial prefrontal cortex and insula) and posterior cingulate/occipital areas supporting perceptual processing. In this single altered network, patients with SAD had higher functional connectivity than HC. At the global level, graph-theory analysis revealed that the patients exhibited a lower normalized characteristic path length than HC, which suggests a disorder-related shift of network topology toward randomized configurations. SAD-related deficits in nodal degree, efficiency and participation coefficient were detected in the parahippocampal gyrus, posterior cingulate cortex, dorsolateral prefrontal cortex, insula and the calcarine sulcus. Aspects of abnormal connectivity were associated with anxiety symptoms. These findings highlight the aberrant topological organization of functional brain network organization in SAD, which provides insights into the neural mechanisms underlying excessive fear and avoidance of social interactions in patients with debilitating social anxiety. Copyright © 2017. Published by Elsevier Inc.

Ultra-low-loss tapered optical fibers with minimal lengths

NASA Astrophysics Data System (ADS)

Nagai, Ryutaro; Aoki, Takao

2014-11-01

We design and fabricate ultra-low-loss tapered optical fibers (TOFs) with minimal lengths. We first optimize variations of the torch scan length using the flame-brush method for fabricating TOFs with taper angles that satisfy the adiabaticity criteria. We accordingly fabricate TOFs with optimal shapes and compare their transmission to TOFs with a constant taper angle and TOFs with an exponential shape. The highest transmission measured for TOFs with an optimal shape is in excess of 99.7 % with a total TOF length of only 23 mm, whereas TOFs with a constant taper angle of 2 mrad reach 99.6 % transmission for a 63 mm TOF length.

Comparison of classical reaction paths and tunneling paths studied with the semiclassical instanton theory.

PubMed

Meisner, Jan; Markmeyer, Max N; Bohner, Matthias U; Kästner, Johannes

2017-08-30

Atom tunneling in the hydrogen atom transfer reaction of the 2,4,6-tri-tert-butylphenyl radical to 3,5-di-tert-butylneophyl, which has a short but strongly curved reaction path, was investigated using instanton theory. We found the tunneling path to deviate qualitatively from the classical intrinsic reaction coordinate, the steepest-descent path in mass-weighted Cartesian coordinates. To perform that comparison, we implemented a new variant of the predictor-corrector algorithm for the calculation of the intrinsic reaction coordinate. We used the reaction force analysis method as a means to decompose the reaction barrier into structural and electronic components. Due to the narrow energy barrier, atom tunneling is important in the abovementioned reaction, even above room temperature. Our calculated rate constants between 350 K and 100 K agree well with experimental values. We found a H/D kinetic isotope effect of almost 10 6 at 100 K. Tunneling dominates the protium transfer below 400 K and the deuterium transfer below 300 K. We compared the lengths of the tunneling path and the classical path for the hydrogen atom transfer in the reaction HCl + Cl and quantified the corner cutting in this reaction. At low temperature, the tunneling path is about 40% shorter than the classical path.

Prediction of enhanced solvent-induced enantioselectivity for a ring opening with a bifurcating reaction path

DOE PAGES

Carpenter, Barry K.; Harvey, Jeremy N.; Glowacki, David R.

2014-12-11

Classical molecular dynamics simulations are reported for the deazetisation and ring opening of meso-2,3-difluoro-2,3-dimethyldiazocyclopropane in three solvents: CHCl 3, CHFClBr and CH 3CH(OH)CF 3 (TFIPA). In this study, the achiral reactant leads to enantiomeric allene products, and the question addressed in the study is whether either of the chiral, enantiomerically pure solvents can induce significant enantiomeric excess in the products. The direct dynamics calculations use an empirical valence bond potential for the solute, with empirical parameters optimised against M06-2X/cc-pVTZ density functional results. The results reveal that the exothermic N 2 loss and ring opening promote transient strong solvent–solute interactions withinmore » the first ~100 fs of the reaction. Because of the bifurcating reaction path, these interactions occur at time when the “decision” about which enantiomer of the product to form has yet to be made (at least for many of the trajectories). Hence, it is possible in principle that the solvent could exert a larger-than-normal influence on the course of the reaction. In fact, the results reveal no such effect for CHFClBr but do predict that TFIPA should induce 15.2 ± 2.1% enantiomeric excess. This is roughly an order of magnitude larger than solvent-induced enantiomeric excesses found experimentally in reactions where the conversion of reactant(s) to enantiomeric products occur over separate transition states.« less

Raman scattering in a whispering mode optical waveguide

DOEpatents

Kurnit, Norman A.

1982-01-01

A device and method for Raman scattering in a whispering mode optical waveguide. Both a helical ribbon and cylinder are disclosed which incorporate an additional curvature .rho. p for confining the beam to increase intensity. A Raman scattering medium is disposed in the optical path of the beam as it propagates along the waveguide. Raman scattering is enhanced by the high intensities of the beam and long interaction path lengths which are achieved in a small volume.

Pipeline Processing with an Iterative, Context-Based Detection Model

DTIC Science & Technology

2016-01-22

25: Teleseismic paths from earthquakes in Myanmar to three North American arrays. The path length to ILAR (the nearest array) is about 8950...kilometers. ................................. 57 Figure 26: Waveforms of Myanmar calibration event (left) and target event (right), recorded at ILAR...one Myanmar event (2007 5/16 8:56:16.0, Mw 6.3; 20.47°N 100.69°E) as a calibration for a second event occurring nearly 4 years later (2011 3/24 13:55

Optical pumping in a whispering-mode optical waveguide

DOEpatents

Kurnit, N.A.

1981-08-11

A device and method for optical pumping in a whispering mode optical waveguide are described. Both a helical ribbon and cylinder are disclosed which incorporate an additional curvature for confining the beam to increase intensity. An optical pumping medium is disposed in the optical path of the beam as it propagates along the waveguide. Optical pumping is enhanced by the high intensities of the beam and long interaction path lengths which are achieved in a small volume.

The Challenge of Characterizing Branching in Molecular Species.

DTIC Science & Technology

1986-07-16

representing respectively paths of lengths two and three. Strictly speaking, a septuple rather than a pair should have been used to account for all the paths...same counts, are of fundmental importance in the study of isospectral graphs. These facts were exploited by the latter workers to establish a 1-1...case of the Hosoya index, Z(G), a composition principle was given [38] from which it was apparent that Z(G) depends on certain subgraphs of C for

Steiner trees and spanning trees in six-pin soap films

NASA Astrophysics Data System (ADS)

Dutta, Prasun; Khastgir, S. Pratik; Roy, Anushree

2010-02-01

The problem of finding minimum (local as well as absolute) path lengths joining given points (or terminals) on a plane is known as the Steiner problem. The Steiner problem arises in finding the minimum total road length joining several towns and cities. We study the Steiner tree problem using six-pin soap films. Experimentally, we observe spanning trees as well as Steiner trees partly by varying the pin diameter. We propose a possibly exact expression for the length of a spanning tree or a Steiner tree, which fails mysteriously in certain cases.

Fast exploration of an optimal path on the multidimensional free energy surface

PubMed Central

Chen, Changjun

2017-01-01

In a reaction, determination of an optimal path with a high reaction rate (or a low free energy barrier) is important for the study of the reaction mechanism. This is a complicated problem that involves lots of degrees of freedom. For simple models, one can build an initial path in the collective variable space by the interpolation method first and then update the whole path constantly in the optimization. However, such interpolation method could be risky in the high dimensional space for large molecules. On the path, steric clashes between neighboring atoms could cause extremely high energy barriers and thus fail the optimization. Moreover, performing simulations for all the snapshots on the path is also time-consuming. In this paper, we build and optimize the path by a growing method on the free energy surface. The method grows a path from the reactant and extends its length in the collective variable space step by step. The growing direction is determined by both the free energy gradient at the end of the path and the direction vector pointing at the product. With fewer snapshots on the path, this strategy can let the path avoid the high energy states in the growing process and save the precious simulation time at each iteration step. Applications show that the presented method is efficient enough to produce optimal paths on either the two-dimensional or the twelve-dimensional free energy surfaces of different small molecules. PMID:28542475

A comparative study of inelastic scattering models at energy levels ranging from 0.5 keV to 10 keV

NASA Astrophysics Data System (ADS)

Hu, Chia-Yu; Lin, Chun-Hung

2017-03-01

Six models, including a single-scattering model, four hybrid models, and one dielectric function model, were evaluated using Monte Carlo simulations for aluminum and copper at incident beam energies ranging from 0.5 keV to 10 keV. The inelastic mean free path, mean energy loss per unit path length, and backscattering coefficients obtained by these models are compared and discussed to understand the merits of the various models. ANOVA (analysis of variance) statistical models were used to quantify the effects of inelastic cross section and energy loss models on the basis of the simulated results deviation from the experimental data for the inelastic mean free path, the mean energy loss per unit path length, and the backscattering coefficient, as well as their correlations. This work in this study is believed to be the first application of ANOVA models towards evaluating inelastic electron beam scattering models. This approach is an improvement over the traditional approach which involves only visual estimation of the difference between the experimental data and simulated results. The data suggests that the optimization of the effective electron number per atom, binding energy, and cut-off energy of an inelastic model for different materials at different beam energies is more important than the selection of inelastic models for Monte Carlo electron scattering simulation. During the simulations, parameters in the equations should be tuned according to different materials for different beam energies rather than merely employing default parameters for an arbitrary material. Energy loss models and cross-section formulas are not the main factors influencing energy loss. Comparison of the deviation of the simulated results from the experimental data shows a significant correlation (p < 0.05) between the backscattering coefficient and energy loss per unit path length. The inclusion of backscattering electrons generated by both primary and secondary electrons for backscattering coefficient simulation is recommended for elements with high atomic numbers. In hybrid models, introducing the inner shell ionization model improves the accuracy of simulated results.

Effects of urban sprawl and vehicle miles traveled on traffic fatalities.

PubMed

Yeo, Jiho; Park, Sungjin; Jang, Kitae

2015-01-01

Previous research suggests that urban sprawl increases auto-dependency and that excessive auto use increases the risk of traffic fatalities. This indirect effect of urban sprawl on traffic fatalities is compared to non-vehicle miles traveled (VMT)-related direct effect of sprawl on fatalities. We conducted a path analysis to examine the causal linkages among urban sprawl, VMT, traffic fatalities, income, and fuel cost. The path diagram includes 2 major linkages: the direct relationship between urban sprawl and traffic fatalities and the indirect effect on fatalities through increased VMT in sprawling urban areas. To measure the relative strength of these causal linkages, path coefficients are estimated using data collected nationally from 147 urbanized areas in the United States. Through both direct and indirect paths, urban sprawl is associated with greater numbers of traffic fatalities, but the direct effect of sprawl on fatalities is more influential than the indirect effect. Enhancing traffic safety can be achieved by impeding urban sprawl and encouraging compact development. On the other hand, policy tools reducing VMT may be less effective than anticipated for traffic safety.

A Statistical Simulation Approach to Safe Life Fatigue Analysis of Redundant Metallic Components

NASA Technical Reports Server (NTRS)

Matthews, William T.; Neal, Donald M.

1997-01-01

This paper introduces a dual active load path fail-safe fatigue design concept analyzed by Monte Carlo simulation. The concept utilizes the inherent fatigue life differences between selected pairs of components for an active dual path system, enhanced by a stress level bias in one component. The design is applied to a baseline design; a safe life fatigue problem studied in an American Helicopter Society (AHS) round robin. The dual active path design is compared with a two-element standby fail-safe system and the baseline design for life at specified reliability levels and weight. The sensitivity of life estimates for both the baseline and fail-safe designs was examined by considering normal and Weibull distribution laws and coefficient of variation levels. Results showed that the biased dual path system lifetimes, for both the first element failure and residual life, were much greater than for standby systems. The sensitivity of the residual life-weight relationship was not excessive at reliability levels up to R = 0.9999 and the weight penalty was small. The sensitivity of life estimates increases dramatically at higher reliability levels.

Properties of a new small-world network with spatially biased random shortcuts

NASA Astrophysics Data System (ADS)

Matsuzawa, Ryo; Tanimoto, Jun; Fukuda, Eriko

2017-11-01

This paper introduces a small-world (SW) network with a power-law distance distribution that differs from conventional models in that it uses completely random shortcuts. By incorporating spatial constraints, we analyze the divergence of the proposed model from conventional models in terms of fundamental network properties such as clustering coefficient, average path length, and degree distribution. We find that when the spatial constraint more strongly prohibits a long shortcut, the clustering coefficient is improved and the average path length increases. We also analyze the spatial prisoner's dilemma (SPD) games played on our new SW network in order to understand its dynamical characteristics. Depending on the basis graph, i.e., whether it is a one-dimensional ring or a two-dimensional lattice, and the parameter controlling the prohibition of long-distance shortcuts, the emergent results can vastly differ.

Beam splitter and method for generating equal optical path length beams

DOEpatents

Qian, Shinan; Takacs, Peter

2003-08-26

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

A Model of Adding Relations in Multi-levels to a Formal Organization Structure with Two Subordinates

NASA Astrophysics Data System (ADS)

Sawada, Kiyoshi; Amano, Kazuyuki

2009-10-01

This paper proposes a model of adding relations in multi-levels to a formal organization structure with two subordinates such that the communication of information between every member in the organization becomes the most efficient. When edges between every pair of nodes with the same depth in L (L = 1, 2, …, H) levels are added to a complete binary tree of height H, an optimal set of depths {N1, N2, …, NL} (H⩾N1>N2> …>NL⩾1) is obtained by maximizing the total shortening path length which is the sum of shortening lengths of shortest paths between every pair of all nodes in the complete binary tree. It is shown that {N1, N2, …, NL}* = {H, H-1, …, H-L+1}.

The predictive power of local properties of financial networks

NASA Astrophysics Data System (ADS)

Caraiani, Petre

2017-01-01

The literature on analyzing the dynamics of financial networks has focused so far on the predictive power of global measures of networks like entropy or index cohesive force. In this paper, I show that the local network properties have similar predictive power. I focus on key network measures like average path length, average degree or cluster coefficient, and also consider the diameter and the s-metric. Using Granger causality tests, I show that some of these measures have statistically significant prediction power with respect to the dynamics of aggregate stock market. Average path length is most robust relative to the frequency of data used or specification (index or growth rate). Most measures are found to have predictive power only for monthly frequency. Further evidences that support this view are provided through a simple regression model.

Improving the resolution for Lamb wave testing via a smoothed Capon algorithm

NASA Astrophysics Data System (ADS)

Cao, Xuwei; Zeng, Liang; Lin, Jing; Hua, Jiadong

2018-04-01

Lamb wave testing is promising for damage detection and evaluation in large-area structures. The dispersion of Lamb waves is often unavoidable, restricting testing resolution and making the signal hard to interpret. A smoothed Capon algorithm is proposed in this paper to estimate the accurate path length of each wave packet. In the algorithm, frequency domain whitening is firstly used to obtain the transfer function in the bandwidth of the excitation pulse. Subsequently, wavenumber domain smoothing is employed to reduce the correlation between wave packets. Finally, the path lengths are determined by distance domain searching based on the Capon algorithm. Simulations are applied to optimize the number of smoothing times. Experiments are performed on an aluminum plate consisting of two simulated defects. The results demonstrate that spatial resolution is improved significantly by the proposed algorithm.

Light absorption cell combining variable path and length pump

DOEpatents

Prather, William S.

1993-01-01

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.

Eccentric connectivity index of chemical trees

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haoer, R. S., E-mail: raadsehen@gmail.com; Department of Mathematics, Faculty of Computer Sciences and Mathematics, University Of Kufa, Najaf; Atan, K. A., E-mail: kamel@upm.edu.my

Let G = (V, E) be a simple connected molecular graph. In such a simple molecular graph, vertices and edges are depicted atoms and chemical bonds respectively, we refer to the sets of vertices by V (G) and edges by E (G). If d(u, v) be distance between two vertices u, v ∈ V(G) and can be defined as the length of a shortest path joining them. Then, the eccentricity connectivity index (ECI) of a molecular graph G is ξ(G) = ∑{sub v∈V(G)} d(v) ec(v), where d(v) is degree of a vertex v ∈ V(G). ec(v) is the length ofmore » a greatest path linking to another vertex of v. In this study, we focus the general formula for the eccentricity connectivity index (ECI) of some chemical trees as alkenes.« less

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Spectroscopic detection of biological NO with a quantum cascade laser

NASA Technical Reports Server (NTRS)

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

Graph Metrics of Structural Brain Networks in Individuals with Schizophrenia and Healthy Controls: Group Differences, Relationships with Intelligence, and Genetics.

PubMed

Yeo, Ronald A; Ryman, Sephira G; van den Heuvel, Martijn P; de Reus, Marcel A; Jung, Rex E; Pommy, Jessica; Mayer, Andrew R; Ehrlich, Stefan; Schulz, S Charles; Morrow, Eric M; Manoach, Dara; Ho, Beng-Choon; Sponheim, Scott R; Calhoun, Vince D

2016-02-01

One of the most prominent features of schizophrenia is relatively lower general cognitive ability (GCA). An emerging approach to understanding the roots of variation in GCA relies on network properties of the brain. In this multi-center study, we determined global characteristics of brain networks using graph theory and related these to GCA in healthy controls and individuals with schizophrenia. Participants (N=116 controls, 80 patients with schizophrenia) were recruited from four sites. GCA was represented by the first principal component of a large battery of neurocognitive tests. Graph metrics were derived from diffusion-weighted imaging. The global metrics of longer characteristic path length and reduced overall connectivity predicted lower GCA across groups, and group differences were noted for both variables. Measures of clustering, efficiency, and modularity did not differ across groups or predict GCA. Follow-up analyses investigated three topological types of connectivity--connections among high degree "rich club" nodes, "feeder" connections to these rich club nodes, and "local" connections not involving the rich club. Rich club and local connectivity predicted performance across groups. In a subsample (N=101 controls, 56 patients), a genetic measure reflecting mutation load, based on rare copy number deletions, was associated with longer characteristic path length. Results highlight the importance of characteristic path lengths and rich club connectivity for GCA and provide no evidence for group differences in the relationships between graph metrics and GCA.

Estimating Brownian motion dispersal rate, longevity and population density from spatially explicit mark-recapture data on tropical butterflies.

PubMed

Tufto, Jarle; Lande, Russell; Ringsby, Thor-Harald; Engen, Steinar; Saether, Bernt-Erik; Walla, Thomas R; DeVries, Philip J

2012-07-01

1. We develop a Bayesian method for analysing mark-recapture data in continuous habitat using a model in which individuals movement paths are Brownian motions, life spans are exponentially distributed and capture events occur at given instants in time if individuals are within a certain attractive distance of the traps. 2. The joint posterior distribution of the dispersal rate, longevity, trap attraction distances and a number of latent variables representing the unobserved movement paths and time of death of all individuals is computed using Gibbs sampling. 3. An estimate of absolute local population density is obtained simply by dividing the Poisson counts of individuals captured at given points in time by the estimated total attraction area of all traps. Our approach for estimating population density in continuous habitat avoids the need to define an arbitrary effective trapping area that characterized previous mark-recapture methods in continuous habitat. 4. We applied our method to estimate spatial demography parameters in nine species of neotropical butterflies. Path analysis of interspecific variation in demographic parameters and mean wing length revealed a simple network of strong causation. Larger wing length increases dispersal rate, which in turn increases trap attraction distance. However, higher dispersal rate also decreases longevity, thus explaining the surprising observation of a negative correlation between wing length and longevity. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Radio-anatomical Study of the Greater Palatine Canal and the Pterygopalatine Fossa in a Lebanese Population: A Consideration for Maxillary Nerve Block

PubMed Central

Aoun, Georges; Nasseh, Ibrahim; Sokhn, Sayde

2016-01-01

Aim: The aim of this study was to describe the morphology of the component, greater palatine canal-pterygopalatine fossa (GPC-PPF), in a Lebanese population using cone-beam computed tomography (CBCT) technology. Materials and Methods: CBCT images of 79 Lebanese adult patients (38 females and 41 males) were included in this study, and a total of 158 cases were evaluated bilaterally. The length and path of the GPCs-PPFs were determined, and the data obtained analyzed statistically. Results: In the sagittal plane, of all the GPCs-PPFs assessed, the average length was 35.02 mm on the right and 35.01 mm on the left. The most common anatomic path consisted in the presence of a curvature resulting in an internal narrowing whose average diameter was 2.4 mm on the right and 2.45 mm on the left. The mean diameter of the upper opening was 5.85 mm on the right and 5.82 mm on the left. As for the lower opening corresponding to the greater palatine foramen, the right and left average diameters were 6.39 mm and 6.42 mm, respectively. Conclusion: Within the limits of this study, we concluded that throughout the Lebanese population, the GPC-PPF path is variable with a predominance of curved one (77.21% [122/158] in both the right and left sides); however, the GPC-PPF length does not significantly vary according to gender and side. PMID:27833777

The conical pendulum: the tethered aeroplane

NASA Astrophysics Data System (ADS)

Mazza, Anthony P.; Metcalf, William E.; Cinson, Anthony D.; Lynch, John J.

2007-01-01

The introductory physics lab curriculum usually has one experiment on uniform circular motion (UCM). Physics departments typically have several variable-speed rotators in storage that, if they work, no longer work well. Replacing these rotators with new ones is costly, especially when they are only used once a year. This article describes how an inexpensive (ap10) tethered aeroplane, powered by a small electric motor, can be used to study UCM. The aeroplane is easy to see and entertaining to watch. For a given string length and air speed, a tethered aeroplane quickly finds a stable, horizontal, circular orbit. Using a digital video (DV) camcorder, VideoPoint Capture, QuickTime player, metre sticks and a stopwatch, data on the aeroplane's motion were obtained. The length of the string was varied from 120 to 340 cm while the air speed ranged from 200 to 480 cm s-1. For each string length and air speed, the period of the orbit and the diameter of the path were carefully measured. Theoretical values of path radii were then calculated using Newton's second law. The agreement between experiment and theory was usually better than 2%.

Bell's twin rockets non-inertial length enigma resolved by real geometry

NASA Astrophysics Data System (ADS)

Coleman, Brian

A priori uniformity and monotonicity of the 'non-inertial length' expansion of a uniformly co-accelerating medium, uniquely yield an unfamiliar 'hemicoid' real-values metric surface ϒ in R3 . ϒ (τ, l) hosts congruent helicoidally distributed fixed-l 'hemix world-lines' tracing medium increments' clock times τ and crossed by fixed- τ medium helices of parameterized length λ sharing comoving 'non-inertial frames'. Radar intervals and expansion factor ∂λ / ∂l = √ (1 +v2 /c2) conform to requirements established in Coleman, Results in Physics,6, 2016-Minkowski spacetime does not apply to a homogeneously accelerating medium. Co-directional radar paths on ϒ mapped from home frame chart diagonals crossing hyperbolic world-lines, surf 'horizon' increment hemices, whereas counter-directional radar paths tend to 'overlap' horizon medium helices. They also traverse each medium expansion helix at respectively identical angles and geodesic curvatures, independently of differing rocket emission times. Surface ϒ 's real metric is: ds2 = dτ2 + dλ2 +[ 2 tanhτ . (tanhτ - 1 / coshτ) / √ (1 +tanh2 τ) ] dτ . dλ .

Glow discharge based device for solving mazes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubinov, Alexander E., E-mail: dubinov-ae@yandex.ru; Mironenko, Maxim S.; Selemir, Victor D.

2014-09-15

A glow discharge based device for solving mazes has been designed and tested. The device consists of a gas discharge chamber and maze-transformer of radial-azimuth type. It allows changing of the maze pattern in a short period of time (within several minutes). The device has been tested with low pressure air. Once switched on, a glow discharge has been shown to find the shortest way through the maze from the very first attempt, even if there is a section with potential barrier for electrons on the way. It has been found that ionization waves (striations) can be excited in themore » maze along the length of the plasma channel. The dependancy of discharge voltage on the length of the optimal path through the maze has been measured. A reduction in discharge voltage with one or two potential barriers present has been found and explained. The dependency of the magnitude of discharge ignition voltage on the length of the optimal path through the maze has been measured. The reduction of the ignition voltage with the presence of one or two potential barriers has been observed and explained.« less

Energy Harvesting A Nano-Scale Based Magnetothermal-Electric Element

DTIC Science & Technology

2015-05-21

induction ,  H  is  the...field   and   L   is   the   length   of   the  magnetic   circuit .   As   the   area,   path   length   and   applied...subsequently   annealed   to   850   C,   for   1   hour,   in   a   tube   furnace   under   a  

Energy Harvesting A Nano-Scale Based Magneto-Thermal-Electric Element

DTIC Science & Technology

2015-05-21

induction ,  H  is...magnetic   field   and   L   is   the   length   of   the  magnetic   circuit .   As   the   area,   path   length   and...sample   was   subsequently   annealed   to   850   C,   for   1   hour,   in   a   tube   furnace   under  

Time-bin entangled photon pairs from spontaneous parametric down-conversion pumped by a cw multi-mode diode laser.

PubMed

Kwon, Osung; Park, Kwang-Kyoon; Ra, Young-Sik; Kim, Yong-Su; Kim, Yoon-Ho

2013-10-21

Generation of time-bin entangled photon pairs requires the use of the Franson interferometer which consists of two spatially separated unbalanced Mach-Zehnder interferometers through which the signal and idler photons from spontaneous parametric down-conversion (SPDC) are made to transmit individually. There have been two SPDC pumping regimes where the scheme works: the narrowband regime and the double-pulse regime. In the narrowband regime, the SPDC process is pumped by a narrowband cw laser with the coherence length much longer than the path length difference of the Franson interferometer. In the double-pulse regime, the longitudinal separation between the pulse pair is made equal to the path length difference of the Franson interferometer. In this paper, we propose another regime by which the generation of time-bin entanglement is possible and demonstrate the scheme experimentally. In our scheme, differently from the previous approaches, the SPDC process is pumped by a cw multi-mode (i.e., short coherence length) laser and makes use of the coherence revival property of such a laser. The high-visibility two-photon Franson interference demonstrates clearly that high-quality time-bin entanglement source can be developed using inexpensive cw multi-mode diode lasers for various quantum communication applications.

The Characteristics and Causes of Push-off During Screw Rotor Manufacture, and its Compensation by Multi-axis Machine Path Calculations

NASA Astrophysics Data System (ADS)

Wang, X.; Holmes, C. S.

2015-08-01

When grinding helical components, errors occur at the beginning and end of the contact path between the component and grinding wheel. This is due to the forces on the component changing as the grinding wheel comes into and out-of full contact with the component. In addition, shaft bending may add depth changes which vary along the length. This may result in an interrupted contact line and increased noise from the rotors. Using on-board scanning, software has been developed to calculate a compensated grinding path, which includes the adjustments of head angle, work rotation and infeed. This grinding path compensates not only lead errors, but also reduces the profile errors as well. The program has been tested in rotor production and the results are shown.

On the formation of granulites

USGS Publications Warehouse

Bohlen, S.R.

1991-01-01

The tectonic settings for the formation and evolution of regional granulite terranes and the lowermost continental crust can be deduced from pressure-temperature-time (P-T-time) paths and constrained by petrological and geophysical considerations. P-T conditions deduced for regional granulites require transient, average geothermal gradients of greater than 35??C km-1, implying minimum heat flow in excess of 100 mW m-2. Such high heat flow is probably caused by magmatic heating. Tectonic settings wherein such conditions are found include convergent plate margins, continental rifts, hot spots and at the margins of large, deep-seated batholiths. Cooling paths can be constrained by solid-solid and devolatilization equilibria and geophysical modelling. -from Author

Twist-writhe partitioning in a coarse-grained DNA minicircle model

NASA Astrophysics Data System (ADS)

Sayar, Mehmet; Avşaroǧlu, Barış; Kabakçıoǧlu, Alkan

2010-04-01

Here we present a systematic study of supercoil formation in DNA minicircles under varying linking number by using molecular-dynamics simulations of a two-bead coarse-grained model. Our model is designed with the purpose of simulating long chains without sacrificing the characteristic structural properties of the DNA molecule, such as its helicity, backbone directionality, and the presence of major and minor grooves. The model parameters are extracted directly from full-atomistic simulations of DNA oligomers via Boltzmann inversion; therefore, our results can be interpreted as an extrapolation of those simulations to presently inaccessible chain lengths and simulation times. Using this model, we measure the twist/writhe partitioning in DNA minicircles, in particular its dependence on the chain length and excess linking number. We observe an asymmetric supercoiling transition consistent with experiments. Our results suggest that the fraction of the linking number absorbed as twist and writhe is nontrivially dependent on chain length and excess linking number. Beyond the supercoiling transition, chains of the order of one persistence length carry equal amounts of twist and writhe. For longer chains, an increasing fraction of the linking number is absorbed by the writhe.

Prioritizing quality improvement in general surgery.

PubMed

Schilling, Peter L; Dimick, Justin B; Birkmeyer, John D

2008-11-01

Despite growing interest in quality improvement, uncertainty remains about which procedures offer the most room for improvement in general surgery. In this context, we sought to describe the relative contribution of different procedures to overall morbidity, mortality, and excess length of stay in general surgery. Using data from the American College of Surgeons' National Surgery Quality Improvement Program (ACS-NSQIP), we identified all patients undergoing a general surgery procedure in 2005 and 2006 (n=129,233). Patients were placed in 36 distinct procedure groups based on Current Procedural Terminology codes. We first examined procedure groups according to their relative contribution to overall morbidity and mortality. We then assessed procedure groups according to their contribution to overall excess length of stay. Ten procedure groups alone accounted for 62% of complications and 54% of excess hospital days. Colectomy accounted for the greatest share of adverse events, followed by small intestine resection, inpatient cholecystectomy, and ventral hernia repair. In contrast, several common procedures contributed little to overall morbidity and mortality. For example, outpatient cholecystectomy, breast procedures, thyroidectomy, parathyroidectomy, and outpatient inguinal hernia repair together accounted for 34% of procedures, but only 6% of complications (and only 4% of major complications). These same procedures accounted for < 1% of excess hospital days. A relatively small number of procedures account for a disproportionate share of the morbidity, mortality, and excess hospital days in general surgery. Focusing quality improvement efforts on these procedures may be an effective strategy for improving patient care and reducing cost.

Gain degradation and amplitude scintillation due to tropospheric turbulence

NASA Technical Reports Server (NTRS)

Theobold, D. M.; Hodge, D. B.

1978-01-01

It is shown that a simple physical model is adequate for the prediction of the long term statistics of both the reduced signal levels and increased peak-to-peak fluctuations. The model is based on conventional atmospheric turbulence theory and incorporates both amplitude and angle of arrival fluctuations. This model predicts the average variance of signals observed under clear air conditions at low elevation angles on earth-space paths at 2, 7.3, 20 and 30 GHz. Design curves based on this model for gain degradation, realizable gain, amplitude fluctuation as a function of antenna aperture size, frequency, and either terrestrial path length or earth-space path elevation angle are presented.

A note on subtrees rooted along the primary path of a binary tree

USGS Publications Warehouse

Troutman, B.M.; Karlinger, M.R.

1993-01-01

Let Fn denote the set of rooted binary plane trees with n external nodes, for given T???Fn let ui(T) be the altitude i node along the primary path of T, and let ??i(T) denote the number of external nodes in the induced subtree rooted at ui(T). We set ??i(T) = 0 if i is greater than the length of the primary path of T. We prove limn?????? ???i???x/n En{??i}/???i

An optically passive method that doubles the rate of 2-Ghz timing fiducials

NASA Astrophysics Data System (ADS)

Boni, R.; Kendrick, J.; Sorce, C.

2017-08-01

Solid-state optical comb-pulse generators provide a convenient and accurate method to include timing fiducials in a streak camera image for time base correction. Commercially available vertical-cavity surface-emitting lasers (VCSEL's) emitting in the visible currently in use can be modulated up to 2 GHz. An optically passive method is presented to interleave a time-delayed path of the 2-GHz comb with itself, producing a 4-GHz comb. This technique can be applied to VCSEL's with higher modulation rates. A fiber-delivered, randomly polarized 2-GHz VCSEL comb is polarization split into s-polarization and p-polarization paths. One path is time delayed relative to the other by twice the 2-GHz rate with +/-1-ps accuracy; the two paths then recombine at the fiber-coupled output. High throughput (>=90%) is achieved by carefully using polarization beam-splitting cubes, a total internal reflection beam-path-steering prism, and antireflection coatings. The glass path-length delay block and turning prism are optically contacted together. The beam polarizer cubes that split and recombine the paths are precision aligned and permanently cemented into place. We expect the palm-sized, inline fiber-coupled, comb-rate-doubling device to maintain its internal alignment indefinitely.

Design of a feedback-feedforward steering controller for accurate path tracking and stability at the limits of handling

NASA Astrophysics Data System (ADS)

Kapania, Nitin R.; Gerdes, J. Christian

2015-12-01

This paper presents a feedback-feedforward steering controller that simultaneously maintains vehicle stability at the limits of handling while minimising lateral path tracking deviation. The design begins by considering the performance of a baseline controller with a lookahead feedback scheme and a feedforward algorithm based on a nonlinear vehicle handling diagram. While this initial design exhibits desirable stability properties at the limits of handling, the steady-state path deviation increases significantly at highway speeds. Results from both linear and nonlinear analyses indicate that lateral path tracking deviations are minimised when vehicle sideslip is held tangent to the desired path at all times. Analytical results show that directly incorporating this sideslip tangency condition into the steering feedback dramatically improves lateral path tracking, but at the expense of poor closed-loop stability margins. However, incorporating the desired sideslip behaviour into the feedforward loop creates a robust steering controller capable of accurate path tracking and oversteer correction at the physical limits of tyre friction. Experimental data collected from an Audi TTS test vehicle driving at the handling limits on a full length race circuit demonstrates the improved performance of the final controller design.

Uterine Polyps

MedlinePlus

... Signs and symptoms of uterine polyps include: Irregular menstrual bleeding — for example, having frequent, unpredictable periods of variable length and heaviness Bleeding between menstrual periods Excessively heavy menstrual periods Vaginal bleeding after ...

Effect of non-classical current paths in networks of 1-dimensional wires

NASA Astrophysics Data System (ADS)

Echternach, P. M.; Mikhalchuk, A. G.; Bozler, H. M.; Gershenson, M. E.; Bogdanov, A. L.; Nilsson, B.

1996-04-01

At low temperatures, the quantum corrections to the resistance due to weak localization and electron-electron interaction are affected by the shape and topology of samples. We observed these effects in the resistance of 2D percolation networks made from 1D wires and in a series of long 1D wires with regularly spaced side branches. Branches outside the classical current path strongly reduce the quantum corrections to the resistance and these reductions become a measure of the quantum lengths.

Polarization Considerations for the Laser Interferometer Space Antenna

NASA Technical Reports Server (NTRS)

Waluschka, Eugene; Pedersen, Tracy R.; McNamara, Paul

2005-01-01

A polarization ray trace model of the Laser Interferometer Space Antenna s (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required, very long path length, picometer level dynamic interferometry. The computational steps are described. This should eliminate any ambiguities associated with polarization ray tracing of interferometers and provide a basis for determining the computer model s limitations and serve as a clearly defined starting point for future work.

Near-Millimeter Wave Technology Base Study: Volume I. Propagation and Target/Background Characteristics

DTIC Science & Technology

1979-11-01

diameter test cell used for laser propagation measurements is Path length-84 m to 2.0 km available and has been designed for circulating aerosols or...36- and 110-GHz and found an attenuation ratio of comparison measurements along a 4-km path with rain rate measured near the receiver end. a *02 They...time. Tipping-bucket systems . gauges are reliable, but become increasingly in- accurate at high rates . Flow gauges which The direct field measurement

Single reflector interference spectrometer and drive system therefor

NASA Technical Reports Server (NTRS)

Schindler, R. A. (Inventor)

1974-01-01

In a Fourier interference spectrometer of the doublepass retroreflector type, a single mirror is employed in the path of both split beams of an incoming ray to cause them to double back through separate retroreflectors. Changes in optical path length are achieved by linear displacement of both retroreflectors using a motor driven lead screw on one for large, low frequency changes, a moving-coil actuator on the other for smaller, mid-frequency changes and a piezoelectric actuator on one of these two for small, high frequency changes.

Non-Normal Projectile Penetration in Soil and Rock: User’s Guide for Computer Code PENC02D.

DTIC Science & Technology

1982-09-01

the path traveled , with projec- tile orientation shown every FREQI projectile lengths. In this run, FREQI was input as 2.5. The horizontal lines...must be a closed surface in the direction of travel ; the bluntness of the nose requires a near 90-deg element for closure. Sheet 3 shows the beginning...plots for this problem. Sheets 1 and 2 automatically verify the projectile shape and path traveled . Sheets 3, 4, and 5 show the axial deceleration

MAS Bulletin. GY-90 Fiber Optic Gyro

DTIC Science & Technology

1989-07-20

487 GY.9O Fiber Optic Gyro Background. Elettronica San Giorgio ELSAG S.p.A., Genoa, Italy, has developed a fiber optic gyro (FOG) for use on short...to the length of ELSAG S.p.A., Naval Systems Division, Via G. Puccini, 2-16154 the optical path and an extremely long optical path can be Genoa, Italy...Telephone 39 10/60011, Fax 39 10/607329, Telex achieved in a small size by using a many-turn coil of optical fiber. 270660/213847 ELSAG 1. There are

Aero-Optical Wavefront Propagation and Refractive Fluid Interfaces in Large-Reynolds-Number Compressible Turbulent Flows

DTIC Science & Technology

2005-12-31

are utilized with the eikonal equation of geometrical optics to propagate computationally the optical wavefronts in the near field. As long as the...aero-optical interactions. In terms of the refractive index field n and the optical path length (OPL), the eikonal equation is: |∇ (OPL)| = n , (9) (e.g...ray n(`, t) d` . (10) The OPL integral corresponds to inverting the eikonal equation 9. The physical distance along the beam propagation path for

Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karles Fellowship

DTIC Science & Technology

2015-11-30

water (DI H2O) as the reference solution, two concentrations of NaCl mixtures (0.6 Molar, and 1.0 Molar saturated NaCl), and three electroless solutions...by diffusion) to the bulk surface in net excess; that oxygen ions/radicals are being consumed from the bulk by an electrolysis path way; or that the

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

NASA Astrophysics Data System (ADS)

Shimamura, Atsushi; Moritsu, Toshiyuki; Someya, Harushi

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.

Folded path LWIR system for SWAP constrained platforms

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

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

PubMed

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

2008-08-19

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.

Spatially and temporally resolved diagnostics of dense sprays using gated, femtosecond, digital holography

NASA Astrophysics Data System (ADS)

Trolinger, James D.; Dioumaev, Andrei K.; Ziaee, Ali; Minniti, Marco; Dunn-Rankin, Derek

2017-08-01

This paper describes research that demonstrated gated, femtosecond, digital holography, enabling 3D microscopic viewing inside dense, almost opaque sprays, and providing a new and powerful diagnostics capability for viewing fuel atomization processes never seen before. The method works by exploiting the extremely short coherence and pulse length (approximately 30 micrometers in this implementation) provided by a femtosecond laser combined with digital holography to eliminate multiple and wide angle scattered light from particles surrounding the injection region, which normally obscures the image of interest. Photons that follow a path that differs in length by more than 30 micrometers from a straight path through the field to the sensor do not contribute to the holographic recording of photons that travel in a near straight path (ballistic and "snake" photons). To further enhance the method, off-axis digital holography was incorporated to enhance signal to noise ratio and image processing capability in reconstructed images by separating the conjugate images, which overlap and interfere in conventional in-line holography. This also enables digital holographic interferometry. Fundamental relationships and limitations were also examined. The project is a continuing collaboration between MetroLaser and the University of California, Irvine.

How Informative are the Vertical Buoyancy and the Prone Gliding Tests to Assess Young Swimmers’ Hydrostatic and Hydrodynamic Profiles?

PubMed Central

Barbosa, Tiago M.; Costa, Mário J.; Morais, Jorge E; Moreira, Marc; Silva, António J.; Marinho, Daniel A.

2012-01-01

The aim of this research was to develop a path-flow analysis model to highlight the relationships between buoyancy and prone gliding tests and some selected anthropometrical and biomechanical variables. Thirty-eight young male swimmers (12.97 ± 1.05 years old) with several competitive levels were evaluated. It were assessed the body mass, height, fat mass, body surface area, vertical buoyancy, prone gliding after wall push-off, stroke length, stroke frequency and velocity after a maximal 25 [m] swim. The confirmatory model included the body mass, height, fat mass, prone gliding test, stroke length, stroke frequency and velocity. All theoretical paths were verified except for the vertical buoyancy test that did not present any relationship with anthropometrical and biomechanical variables nor with the prone gliding test. The good-of-fit from the confirmatory path-flow model, assessed with the standardized root mean square residuals (SRMR), is considered as being close to the cut-off value, but even so not suitable of the theory (SRMR = 0.11). As a conclusion, vertical buoyancy and prone gliding tests are not the best techniques to assess the swimmer’s hydrostatic and hydrodynamic profile, respectively. PMID:23486528

Magnet design for the splitter/combiner regions of CBETA, the Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crittendon, J. A.; Burke, D. C.; Fuentes, Y. L.P.

2017-01-06

The Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator (CBETA) will provide a 150-MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV. Here we describe magnet designs for the splitter and combiner regions which serve to match the on-axis linac beam to the off-axis beams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams.more » The path lengths of the four beamlines in each of the splitter and combiner regions are designed to be adapted to 1-, 2-, 3-, and 4-pass staged operations. Design specifi- cations and modeling for the 24 dipole and 32 quadrupole electromagnets in each region are presented. The CBETA project will serve as the first demonstration of multi-pass energy recovery using superconducting RF cavities with FFAG cell optics for the return loop.« less

Paving the Way Towards Reactive Planar Spanner Construction in Wireless Networks

NASA Astrophysics Data System (ADS)

Frey, Hannes; Rührup, Stefan

A spanner is a subgraph of a given graph that supports the original graph's shortest path lengths up to a constant factor. Planar spanners and their distributed construction are of particular interest for geographic routing, which is an efficient localized routing scheme for wireless ad hoc and sensor networks. Planarity of the network graph is a key criterion for guaranteed delivery, while the spanner property supports efficiency in terms of path length. We consider the problem of reactive local spanner construction, where a node's local topology is determined on demand. Known message-efficient reactive planarization algorithms do not preserve the spanner property, while reactive spanner constructions with a low message overhead have not been described so far. We introduce the concept of direct planarization which may be an enabler of efficient reactive spanner construction. Given an edge, nodes check for all incident intersecting edges a certain geometric criterion and withdraw the edge if this criterion is not satisfied. We use this concept to derive a generic reactive topology control mechanism and consider two geometric criteria. Simulation results show that direct planarization increases the performance of localized geographic routing by providing shorter paths than existing reactive approaches.

Nuclear Matter Properties with the Re-evaluated Coefficients of Liquid Drop Model

NASA Astrophysics Data System (ADS)

Chowdhury, P. Roy; Basu, D. N.

2006-06-01

The coefficients of the volume, surface, Coulomb, asymmetry and pairing energy terms of the semiempirical liquid drop model mass formula have been determined by furnishing best fit to the observed mass excesses. Slightly different sets of the weighting parameters for liquid drop model mass formula have been obtained from minimizations of \\chi 2 and mean square deviation. The most recent experimental and estimated mass excesses from Audi-Wapstra-Thibault atomic mass table have been used for the least square fitting procedure. Equation of state, nuclear incompressibility, nuclear mean free path and the most stable nuclei for corresponding atomic numbers, all are in good agreement with the experimental results.

Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency

NASA Technical Reports Server (NTRS)

Flock, W. L.

1981-01-01

When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.

Growth and differentiation of mammalian embryonic tissues exposed to hypergravity in vivo and in vitro

NASA Technical Reports Server (NTRS)

Duke, J.; Janer, L.; Moore, J.

1985-01-01

Decreased cartilage areas in embryonic limbs developing under excess g in vitro, is reported, as well as delayed skeletal development in embryos and fetuses exposed to excess g in utero. 12.5-day mouse limb buds were cultured at 2.6 g, and fixed at two days and six days of culture. In vivo experiments used alizarin-stained 18-day fetuses exposed to 2.3 g. In all studies, cartilage areas were determined using a digitized tablet. Form factor analysis determined that the main effect of in vitro centrifugation was a reduction in length of the limb elements, probably due to the precocious chondrogenesis seen in the upper regions of centrifuged limbs. Similar reductions in length of ossified areas was seen in the in utero studies.

Investigating the source of anomalous PKP travel-times on south-Sandwich to Alaska paths

NASA Astrophysics Data System (ADS)

Frost, D. A.; Romanowicz, B. A.

2017-12-01

Inner core anisotropy was proposed thirty years ago to explain differences in travel times of inner core phases (PKIKP) on polar and equatorial paths (Morelli et al., 1986). Over time, models of inner core anisotropy have become very complex, with evidence for depth dependence, hemispherical variations, and other localised features. Some models propose the strength of anisotropy to be in excess of 4% in the western hemisphere of the inner core. This is difficult to reconcile with predictions from mineral physics and dynamical models of inner core growth. The strong anisotropy is confined to anomalous paths between earthquakes in the south Sandwich Islands and stations in Alaska. In contrast, the strength of inner core anisotropy obtained from measurements of PKPPKP travel times on polar paths does not exceed 1-2% (Bréger et al., 2000; Frost and Romanowicz, 2017). We re-examine the trends of PKIKP travel times on polar paths, in order to reconcile the different measurements and to determine whether discrepancies can be explained by structure in the mantle, the outer core, or localized strong anisotropy in the inner core. For this, we combine existing and new measurements, taking advantage of recent deployments of broadband arrays in Alaska and Antarctica.

[Remote system of natural gas leakage based on multi-wavelength characteristics spectrum analysis].

PubMed

Li, Jing; Lu, Xu-Tao; Yang, Ze-Hui

2014-05-01

In order to be able to quickly, to a wide range of natural gas pipeline leakage monitoring, the remote detection system for concentration of methane gas was designed based on static Fourier transform interferometer. The system used infrared light, which the center wavelength was calibrated to absorption peaks of methane molecules, to irradiated tested area, and then got the interference fringes by converging collimation system and interference module. Finally, the system calculated the concentration-path-length product in tested area by multi-wavelength characteristics spectrum analysis algorithm, furthermore the inversion of the corresponding concentration of methane. By HITRAN spectrum database, Selected wavelength position of 1. 65 microm as the main characteristic absorption peaks, thereby using 1. 65 pm DFB laser as the light source. In order to improve the detection accuracy and stability without increasing the hardware configuration of the system, solved absorbance ratio by the auxiliary wave-length, and then get concentration-path-length product of measured gas by the method of the calculation proportion of multi-wavelength characteristics. The measurement error from external disturbance is caused by this innovative approach, and it is more similar to a differential measurement. It will eliminate errors in the process of solving the ratio of multi-wavelength characteristics, and can improve accuracy and stability of the system. The infrared absorption spectrum of methane is constant, the ratio of absorbance of any two wavelengths by methane is also constant. The error coefficients produced by the system is the same when it received the same external interference, so the measured noise of the system can be effectively reduced by the ratio method. Experimental tested standards methane gas tank with leaking rate constant. Using the tested data of PN1000 type portable methane detector as the standard data, and were compared to the tested data of the system, while tested distance of the system were 100, 200 and 500 m. Experimental results show that the methane concentration detected value was stable after a certain time leakage, the concentration-path-length product value of the system was stable. For detection distance of 100 m, the detection error of the concentration-path-length product was less than 1. 0%. With increasing distance from tested area, the detection error is increased correspondingly. When the distance was 500 m, the detection error was less than 4. 5%. In short, the detected error of the system is less than 5. 0% after the gas leakage stable, to meet the requirements of the field of natural gas leakage remote sensing.

Excess thermodynamics of mixtures involving xenon and light linear alkanes by computer simulation.

PubMed

Carvalho, A J Palace; Ramalho, J P Prates; Martins, Luís F G

2007-06-14

Excess molar enthalpies and excess molar volumes as a function of composition for liquid mixtures of xenon + ethane (at 161.40 K), xenon + propane (at 161.40 K) and xenon + n-butane (at 182.34 K) have been obtained by Monte Carlo computer simulations and compared with available experimental data. Simulation conditions were chosen to closely match those of the corresponding experimental results. The TraPPE-UA force field was selected among other force fields to model all the alkanes studied, whereas the one-center Lennard-Jones potential from Bohn et al. was used for xenon. The calculated H(m)(E) and V(m)(E) for all systems are negative, increasing in magnitude as the alkane chain length increases. The results for these systems were compared with experimental data and with other theoretical calculations using the SAFT approach. An excellent agreement between simulation and experimental results was found for xenon + ethane system, whereas for the remaining two systems, some deviations that become progressively more significant as the alkane chain length increases were observed.

The ability of Reciproc instruments to reach full working length without glide path preparation: a clinical retrospective study.

PubMed

Bartols, Andreas; Robra, Bernt-Peter; Walther, Winfried

2017-01-01

Reciproc instruments are the only contemporary root canal instruments where glide path preparation is no longer strictly demanded by the manufacturer. As the complete preparation of root canals is associated with success in endodontic treatment we wanted to assess the ability and find predictors for Reciproc instruments to reach full working length (RFWL) in root canals of maxillary molars in primary root canal treatment (1°RCTx) and retreatment (2°RCTx) cases. This retrospective study evaluated 255 endodontic treatment cases of maxillary molars. 180 were 1°RCTx and 75 2°RCTx. All root canals were prepared with Reciproc instruments. The groups were compared and in a binary logistic regression model predictors for RFWL were evaluated. A total of 926 root canals were treated with Reciproc without glide path preparation. This was possible in 885 canals (95.6%). In 1°RCTx cases 625 of 649 (96.3%) canals were RFWL and in 2°RCTx cases 260 of 277 (93.9%). In second and third mesiobuccal canals (MB2/3) 90 out of 101 (89.1%) were RFWL with Reciproc in 1°RCTx and in the 2°RCTx treatment group 49 out of 51 cases (96.1%). In mesio-buccal (MB1) canals "2°RCTx" was identified as negative predictor for RFWL (OR 0.24 (CI [0.08-0.77])). In MB2/3 canals full working length was reached less often (OR 0.04 (CI [0.01-0.31])) if the tooth was constricted and more often if MB2/3 and MB1 canals were convergent (OR 4.60 (CI [1.07-19.61])). Using Reciproc instruments, the vast majority of root canals in primary treatment and retreatment cases can be prepared without glide path preparation.

Investigating scintillometer source areas

NASA Astrophysics Data System (ADS)

Perelet, A. O.; Ward, H. C.; Pardyjak, E.

2017-12-01

Scintillometry is an indirect ground-based method for measuring line-averaged surface heat and moisture fluxes on length scales of 0.5 - 10 km. These length scales are relevant to urban and other complex areas where setting up traditional instrumentation like eddy covariance is logistically difficult. In order to take full advantage of scintillometry, a better understanding of the flux source area is needed. The source area for a scintillometer is typically calculated as a convolution of point sources along the path. A weighting function is then applied along the path to compensate for a total signal contribution that is biased towards the center of the beam path, and decreasing near the beam ends. While this method of calculating the source area provides an estimate of the contribution of the total flux along the beam, there are still questions regarding the physical meaning of the weighted source area. These questions are addressed using data from an idealized experiment near the Salt Lake City International Airport in northern Utah, U.S.A. The site is a flat agricultural area consisting of two different land uses. This simple heterogeneity in the land use facilitates hypothesis testing related to source areas. Measurements were made with a two wavelength scintillometer system spanning 740 m along with three standard open-path infrared gas analyzer-based eddy-covariance stations along the beam path. This configuration allows for direct observations of fluxes along the beam and comparisons to the scintillometer average. The scintillometer system employed measures the refractive index structure parameter of air for two wavelengths of electromagnetic radiation, 880 μm and 1.86 cm to simultaneously estimate path-averaged heat and moisture fluxes, respectively. Meteorological structure parameters (CT2, Cq2, and CTq) as well as surface fluxes are compared for various amounts of source area overlap between eddy covariance and scintillometry. Additionally, surface properties from LANDSAT 7 & 8 are used to help understand source area composition for different times throughout the experiment.

Correction factors to convert microdosimetry measurements in silicon to tissue in 12C ion therapy

NASA Astrophysics Data System (ADS)

Bolst, David; Guatelli, Susanna; Tran, Linh T.; Chartier, Lachlan; Lerch, Michael L. F.; Matsufuji, Naruhiro; Rosenfeld, Anatoly B.

2017-03-01

Silicon microdosimetry is a promising technology for heavy ion therapy (HIT) quality assurance, because of its sub-mm spatial resolution and capability to determine radiation effects at a cellular level in a mixed radiation field. A drawback of silicon is not being tissue-equivalent, thus the need to convert the detector response obtained in silicon to tissue. This paper presents a method for converting silicon microdosimetric spectra to tissue for a therapeutic 12C beam, based on Monte Carlo simulations. The energy deposition spectra in a 10 μm sized silicon cylindrical sensitive volume (SV) were found to be equivalent to those measured in a tissue SV, with the same shape, but with dimensions scaled by a factor κ equal to 0.57 and 0.54 for muscle and water, respectively. A low energy correction factor was determined to account for the enhanced response in silicon at low energy depositions, produced by electrons. The concept of the mean path length < {{l}\\text{Path}}> to calculate the lineal energy was introduced as an alternative to the mean chord length < l> because it was found that adopting Cauchy’s formula for the < l> was not appropriate for the radiation field typical of HIT as it is very directional. < {{l}\\text{Path}}> can be determined based on the peak of the lineal energy distribution produced by the incident carbon beam. Furthermore it was demonstrated that the thickness of the SV along the direction of the incident 12C ion beam can be adopted as < {{l}\\text{Path}}> . The tissue equivalence conversion method and < {{l}\\text{Path}}> were adopted to determine the RBE10, calculated using a modified microdosimetric kinetic model, applied to the microdosimetric spectra resulting from the simulation study. Comparison of the RBE10 along the Bragg peak to experimental TEPC measurements at HIMAC, NIRS, showed good agreement. Such agreement demonstrates the validity of the developed tissue equivalence correction factors and of the determination of < {{l}\\text{Path}}> .

Coupling between absorption and scattering in disordered colloids

NASA Astrophysics Data System (ADS)

Stephenson, Anna; Hwang, Victoria; Park, Jin-Gyu; Manoharan, Vinothan N.

We aim to understand how scattering and absorption are coupled in disordered colloidal suspensions containing absorbing molecules (dyes). When the absorption length is shorter than the transport length, absorption dominates, and absorption and scattering can be seen as two additive effects. However, when the transport length is shorter than the absorption length, the scattering and absorption become coupled, as multiple scattering increases the path length of the light in the sample, leading to a higher probability of absorption. To quantify this synergistic effect, we measure the diffuse reflectance spectra of colloidal samples of varying dye concentrations, thicknesses, and particle concentrations, and we calculate the transport length and absorption length from our measurements, using a radiative transfer model. At particle concentrations so high that the particles form disordered packings, we find a minimum in the transport length. We show that selecting a dye where the absorption peak matches the location of the minimum in the transport length allows for enhanced absorption. Kraft-Heinz Corporation, NSF GRFP 2015200426.

Sensor assembly

DOEpatents

Bennett, Thomas E.; Nelson, Drew V.

2004-04-13

A ribbon-like sensor assembly is described wherein a length of an optical fiber embedded within a similar lengths of a prepreg tow. The fiber is ""sandwiched"" by two layers of the prepreg tow which are merged to form a single consolidated ribbon. The consolidated ribbon achieving a generally uniform distribution of composite filaments near the embedded fiber such that excess resin does not ""pool"" around the periphery of the embedded fiber.

Critical transition in the constrained traveling salesman problem.

PubMed

Andrecut, M; Ali, M K

2001-04-01

We investigate the finite size scaling of the mean optimal tour length as a function of density of obstacles in a constrained variant of the traveling salesman problem (TSP). The computational experience pointed out a critical transition (at rho(c) approximately 85%) in the dependence between the excess of the mean optimal tour length over the Held-Karp lower bound and the density of obstacles.

Determining average path length and average trapping time on generalized dual dendrimer

NASA Astrophysics Data System (ADS)

Li, Ling; Guan, Jihong

2015-03-01

Dendrimer has wide number of important applications in various fields. In some cases during transport or diffusion process, it transforms into its dual structure named Husimi cactus. In this paper, we study the structure properties and trapping problem on a family of generalized dual dendrimer with arbitrary coordination numbers. We first calculate exactly the average path length (APL) of the networks. The APL increases logarithmically with the network size, indicating that the networks exhibit a small-world effect. Then we determine the average trapping time (ATT) of the trapping process in two cases, i.e., the trap placed on a central node and the trap is uniformly distributed in all the nodes of the network. In both case, we obtain explicit solutions of ATT and show how they vary with the networks size. Besides, we also discuss the influence of the coordination number on trapping efficiency.

Error Budgeting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinyard, Natalia Sergeevna; Perry, Theodore Sonne; Usov, Igor Olegovich

2017-10-04

We calculate opacity from k (hn)=-ln[T(hv)]/pL, where T(hv) is the transmission for photon energy hv, p is sample density, and L is path length through the sample. The density and path length are measured together by Rutherford backscatter. Δk =more » $$\\partial k$$\\ $$\\partial T$$ ΔT + $$\\partial k$$\\ $$\\partial (pL)$$. We can re-write this in terms of fractional error as Δk/k = Δ1n(T)/T + Δ(pL)/(pL). Transmission itself is calculated from T=(U-E)/(V-E)=B/B0, where B is transmitted backlighter (BL) signal and B 0 is unattenuated backlighter signal. Then ΔT/T=Δln(T)=ΔB/B+ΔB 0/B 0, and consequently Δk/k = 1/T (ΔB/B + ΔB$$_0$$/B$$_0$$ + Δ(pL)/(pL). Transmission is measured in the range of 0.2« less

Slow light enhanced gas sensing in photonic crystals

NASA Astrophysics Data System (ADS)

Kraeh, Christian; Martinez-Hurtado, J. L.; Popescu, Alexandru; Hedler, Harry; Finley, Jonathan J.

2018-02-01

Infrared spectroscopy allows for highly selective and highly sensitive detection of gas species and concentrations. Conventional gas spectrometers are generally large and unsuitable for on-chip applications. Long absorption path lengths are usually required and impose a challenge for miniaturization. In this work, a gas spectrometer is developed consisting of a microtube photonic crystal structure. This structure of millimetric form factors minimizes the required absorption path length due to slow light effects. The microtube photonic crystal allows for strong transmission in the mid-infrared and, due to its large void space fraction, a strong interaction between light and gas molecules. As a result, enhanced absorption of light increases the gas sensitivity of the device. Slow light enhanced gas absorption by a factor of 5.8 in is experimentally demonstrated at 5400 nm. We anticipate small form factor gas sensors on silicon to be a starting point for on-chip gas sensing architectures.

Light absorption cell combining variable path and length pump

DOEpatents

Prather, W.S.

1993-12-07

A device is described for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid there between and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data. 2 figures.

Optimizing concentration of shifter additive for plastic scintillators of different size

NASA Astrophysics Data System (ADS)

Adadurov, A. F.; Zhmurin, P. N.; Lebedev, V. N.; Titskaya, V. D.

2009-02-01

This paper concerns the influence of wavelength shifting (secondary) luminescent additive (LA 2) on the light yield of polystyrene-based plastic scintillator (PS) taking self-absorption into account. Calculations of light yield dependence on concentration of 1.4-bis(2-(5-phenyloxazolyl)-benzene (POPOP) as LA 2 were made for various path lengths of photons in PS. It is shown that there is an optimal POPOP concentration ( Copt), which provides a maximum light yield for a given path length. This optimal concentration is determined by the competition of luminescence and self-reflection processes. Copt values were calculated for PS of different dimensions. For small PS, Copt≈0.02%, which agree with a common (standard) value of POPOP concentration. For higher PS dimensions, the optimal POPOP concentration is decreased (to Copt≈0.006% for 320×30×2 cm sample), reducing the light yield from PS by almost 35%.

Calibration Method of an Ultrasonic System for Temperature Measurement

PubMed Central

Zhou, Chao; Wang, Yueke; Qiao, Chunjie; Dai, Weihua

2016-01-01

System calibration is fundamental to the overall accuracy of the ultrasonic temperature measurement, and it is basically involved in accurately measuring the path length and the system latency of the ultrasonic system. This paper proposes a method of high accuracy system calibration. By estimating the time delay between the transmitted signal and the received signal at several different temperatures, the calibration equations are constructed, and the calibrated results are determined with the use of the least squares algorithm. The formulas are deduced for calculating the calibration uncertainties, and the possible influential factors are analyzed. The experimental results in distilled water show that the calibrated path length and system latency can achieve uncertainties of 0.058 mm and 0.038 μs, respectively, and the temperature accuracy is significantly improved by using the calibrated results. The temperature error remains within ±0.04°C consistently, and the percentage error is less than 0.15%. PMID:27788252

Measurement of width and pressure in a propagating hydraulic fracture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.R.

Measurements of width and pressure in a propagating hydraulic fracture have been made in tests conducted at the U.S. DOE's Nevada test site. This was accomplished by creating an ''instrumented fracture'' at a tunnel complex (at a depth of 1,400 ft (425 m)) where realistic insitu conditions prevail, particularly with respect to stress and geologic features such as natural fractures and material anisotropy. Analyses of these data show that the pressure drop along the fracture length is much larger than predicted by viscous theory, which currently is used in models. This apparently is caused by the tortuosity of the fracturemore » path, multiple fracture strands, roughness, and sharp turns (corners) in the flow path resulting from natural fractures and rock property variations. It suggests that fracture design models need to be updated to include a more realistic friction factor so that fracture lengths are not overestimated.« less

Measurement of width and pressure in a propagating hydraulic fracture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.R.

Measurements of width and pressure in a propagating hydraulic fracture have been made in tests conducted at DOE's Nevada Test Site. This was accomplished by creating an instrumented fracture at a tunnel complex (at a depth of 1400 ft) where realistic in situ conditions prevail, particularly with respect to stress and geologic features such as natural fractures and material anisotropy. Analyses of these data show that the pressure drop along the fracture length is much larger than predicted by viscous theory and currently in use in models today. This is apparently due to the tortuosity of the fracture path, multiplemore » fracture strands, roughness and sharp turns (corners) in the flow path due to natural fractures and rock property variations. It suggests that fracture design models need to be updated to include a more realistic friction factor so that fracture lengths are not overestimated.« less

Measurement of width and pressure in a propagating hydraulic fracture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.R.

Measurements of width and pressure in a propagating hydraulic fracture have been made in tests conducted at DOE's Nevada Test Site. This was accomplished by creating an ''instrumented fracture'' at a tunnel complex (at a depth of 1400 ft) where realistic in-situ conditions prevail, particularly with respect to stress and geologic features such as natural fractures and material anisotropy. Analyses of these data show that the pressure drop along the fracture length is much larger than predicted by viscous theory and currently in use in models today. This is apparently due to the tortuosity of the fracture path, multiple fracturemore » strands, roughness and sharp turns (corners) in the flow path due to natural fractures and rock property variations. It suggests that fracture design models need to be updated to include a more realistic friction factor so that fracture lengths are not overestimated.« less

New measurements of the 6190-A band of methane

NASA Technical Reports Server (NTRS)

Mickelson, M. E.; Larson, L. E.; Schubert, A.

1991-01-01

The present paper reports new laboratory measurements that were made of the absorption coefficient of the visible methane band at 6190 A. Data were obtained using a tunable dye laser system operating with a line width of 0.067/cm. Spectra were recorded at approximately 1-A intervals with the beam coupled to a 22-m base length White-type absorption cell adjusted for an optical path of 1584 km and filled to a density of 0.884 amagats. Errors in pressure, temperature, and path length amounted to an uncertainty in the abundance of no more than 0.4 percent. Fourteen data sets were recorded and coadded. The final signal-averaged methane data were divided by a similar set of signal-averaged empty cell scans to remove the transmittance of the White cell and system optics. The results are compared with previous low-resolution measurements in the spectral region from 6000 to 6400 A.

Altering length and velocity feedback during a neuro-musculoskeletal simulation of normal gait contributes to hemiparetic gait characteristics.

PubMed

Jansen, Karen; De Groote, Friedl; Aerts, Wouter; De Schutter, Joris; Duysens, Jacques; Jonkers, Ilse

2014-04-30

Spasticity is an important complication after stroke, especially in the anti-gravity muscles, i.e. lower limb extensors. However the contribution of hyperexcitable muscle spindle reflex loops to gait impairments after stroke is often disputed. In this study a neuro-musculoskeletal model was developed to investigate the contribution of an increased length and velocity feedback and altered reflex modulation patterns to hemiparetic gait deficits. A musculoskeletal model was extended with a muscle spindle model providing real-time length and velocity feedback of gastrocnemius, soleus, vasti and rectus femoris during a forward dynamic simulation (neural control model). By using a healthy subject's base muscle excitations, in combination with increased feedback gains and altered reflex modulation patterns, the effect on kinematics was simulated. A foot-ground contact model was added to account for the interaction effect between the changed kinematics and the ground. The qualitative effect i.e. the directional effect and the specific gait phases where the effect is present, on the joint kinematics was then compared with hemiparetic gait deviations reported in the literature. Our results show that increased feedback in combination with altered reflex modulation patterns of soleus, vasti and rectus femoris muscle can contribute to excessive ankle plantarflexion/inadequate dorsiflexion, knee hyperextension/inadequate flexion and increased hip extension/inadequate flexion during dedicated gait cycle phases. Increased feedback of gastrocnemius can also contribute to excessive plantarflexion/inadequate dorsiflexion, however in combination with excessive knee and hip flexion. Increased length/velocity feedback can therefore contribute to two types of gait deviations, which are both in accordance with previously reported gait deviations in hemiparetic patients. Furthermore altered modulation patterns, in particular the reduced suppression of the muscle spindle feedback during swing, can contribute largely to an increased plantarflexion and knee extension during the swing phase and consequently to hampered toe clearance. Our results support the idea that hyperexcitability of length and velocity feedback pathways, especially in combination with altered reflex modulation patterns, can contribute to deviations in hemiparetic gait. Surprisingly, our results showed only subtle temporal differences between length and velocity feedback. Therefore, we cannot attribute the effects seen in kinematics to one specific type of feedback.

A Numerical Model of Exchange Chromatography Through 3D Lattice Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salloum, Maher; Robinson, David B.

Rapid progress in the development of additive manufacturing technologies is opening new opportunities to fabricate structures that control mass transport in three dimensions across a broad range of length scales. We describe a structure that can be fabricated by newly available commercial 3D printers. It contains an array of regular three-dimensional flow paths that are in intimate contact with a solid phase, and thoroughly shuffle material among the paths. We implement a chemically reacting flow model to study its behavior as an exchange chromatography column, and compare it to an array of one-dimensional flow paths that resemble more traditional honeycombmore » monoliths. A reaction front moves through the columns and then elutes. Here, the front is sharper at all flow rates for the structure with three-dimensional flow paths, and this structure is more robust to channel width defects than the one-dimensional array.« less

A Numerical Model of Exchange Chromatography Through 3D Lattice Structures

DOE PAGES

Salloum, Maher; Robinson, David B.

2018-01-30

Rapid progress in the development of additive manufacturing technologies is opening new opportunities to fabricate structures that control mass transport in three dimensions across a broad range of length scales. We describe a structure that can be fabricated by newly available commercial 3D printers. It contains an array of regular three-dimensional flow paths that are in intimate contact with a solid phase, and thoroughly shuffle material among the paths. We implement a chemically reacting flow model to study its behavior as an exchange chromatography column, and compare it to an array of one-dimensional flow paths that resemble more traditional honeycombmore » monoliths. A reaction front moves through the columns and then elutes. Here, the front is sharper at all flow rates for the structure with three-dimensional flow paths, and this structure is more robust to channel width defects than the one-dimensional array.« less

Retrievals of atmospheric columnar carbon dioxide and methane from GOSAT observations with photon path-length probability density function (PPDF) method

NASA Astrophysics Data System (ADS)

Bril, A.; Oshchepkov, S.; Yokota, T.; Yoshida, Y.; Morino, I.; Uchino, O.; Belikov, D. A.; Maksyutov, S. S.

2014-12-01

We retrieved the column-averaged dry air mole fraction of atmospheric carbon dioxide (XCO2) and methane (XCH4) from the radiance spectra measured by Greenhouse gases Observing SATellite (GOSAT) for 48 months of the satellite operation from June 2009. Recent version of the Photon path-length Probability Density Function (PPDF)-based algorithm was used to estimate XCO2 and optical path modifications in terms of PPDF parameters. We also present results of numerical simulations for over-land observations and "sharp edge" tests for sun-glint mode to discuss the algorithm accuracy under conditions of strong optical path modification. For the methane abundance retrieved from 1.67-µm-absorption band we applied optical path correction based on PPDF parameters from 1.6-µm carbon dioxide (CO2) absorption band. Similarly to CO2-proxy technique, this correction assumes identical light path modifications in 1.67-µm and 1.6-µm bands. However, proxy approach needs pre-defined XCO2 values to compute XCH4, whilst the PPDF-based approach does not use prior assumptions on CO2 concentrations.Post-processing data correction for XCO2 and XCH4 over land observations was performed using regression matrix based on multivariate analysis of variance (MANOVA). The MANOVA statistics was applied to the GOSAT retrievals using reference collocated measurements of Total Carbon Column Observing Network (TCCON). The regression matrix was constructed using the parameters that were found to correlate with GOSAT-TCCON discrepancies: PPDF parameters α and ρ, that are mainly responsible for shortening and lengthening of the optical path due to atmospheric light scattering; solar and satellite zenith angles; surface pressure; surface albedo in three GOSAT short wave infrared (SWIR) bands. Application of the post-correction generally improves statistical characteristics of the GOSAT-TCCON correlation diagrams for individual stations as well as for aggregated data.In addition to the analysis of the observations over 12 TCCON stations we estimated temporal and spatial trends (interannual XCO2 and XCH4 variations, seasonal cycles, latitudinal gradients) and compared them with modeled results as well as with similar estimates from other GOSAT retrievals.

A Low Mass Translation Mechanism for Planetary FTIR Spectrometry using an Ultrasonic Piezo Linear Motor

NASA Technical Reports Server (NTRS)

Heverly, Matthew; Dougherty, Sean; Toon, Geoffrey; Soto, Alejandro; Blavier, Jean-Francois

2004-01-01

One of the key components of a Fourier Transform Infrared Spectrometer (FTIR) is the linear translation stage used to vary the optical path length between the two arms of the interferometer. This translation mechanism must produce extremely constant velocity motion across its entire range of travel to allow the instrument to attain high signal-to-noise ratio and spectral resolving power. A new spectrometer is being developed at the Jet Propulsion Laboratory under NASA s Planetary Instrument Definition and Development Program (PIDDP). The goal of this project is to build upon existing spaceborne FTIR spectrometer technology to produce a new instrument prototype that has drastically superior spectral resolution and substantially lower mass, making it feasible for planetary exploration. In order to achieve these goals, Alliance Spacesystems, Inc. (ASI) has developed a linear translation mechanism using a novel ultrasonic piezo linear motor in conjunction with a fully kinematic, fault tolerant linear rail system. The piezo motor provides extremely smooth motion, is inherently redundant, and is capable of producing unlimited travel. The kinematic rail uses spherical Vespel(R). rollers and bushings, which eliminates the need for wet lubrication, while providing a fault tolerant platform for smooth linear motion that will not bind under misalignment or structural deformation. This system can produce velocities from 10 - 100 mm/s with less than 1% velocity error over the entire 100-mm length of travel for a total mechanism mass of less than 850 grams. This system has performed over half a million strokes under vacuum without excessive wear or degradation in performance. This paper covers the design, development, and testing of this linear translation mechanism as part of the Planetary Atmosphere Occultation Spectrometer (PAOS) instrument prototype development program.

[The key role of public health medical resident education for future public health challenges].

PubMed

Costantino, Claudio; Cinquetti, Sandro; Garavelli, Elena; Marcantoni, Claudio; Murru, Claudia; Pieroni, Giovanni; Privitera, Gaetano; Ricciardi, Walter; Soncini, Francesco; Tedesco, Dario; Triassi, Maria; Vitale, Francesco; Campanella, Francesca

2014-01-01

The Italian Committee of medical residents in Hygiene, Preventive Medicine and Public Health is a member of the Italian Society of Hygiene, Preventive Medicine and Public Health with the aim of developing a network among Italian resident in public health and promoting the educational path improvement through comparisons and debates between postgraduate medical schools. In this perspective, during last years account has been taken of some essential topics concerning education of public health medical residents, which represent future health-care and public health experts. Cross-sectional researches were conducted among Italian public health medical residents (PHMRs) through self-administered and web-based questionnaires. Each questionnaire was previously validated by pilot studies conducted during the 46th National Conference of the Italian Society of Hygiene, Preventive Medicine and Public Health. Seventy percent of Italian PHMRs considered the actual length of Public Health postgraduate medical school excessively long, with regard to predetermined educational goals. Confirming this statement, 90% of respondents were inclined to a reduction from 5 to 4 years of postgraduate medical school length, established by Law Decree 104/2013. Seventy seven percent of surveyed PHMRs stand up for a rearrangement on a national setting of the access contest to postgraduate medical schools. Moreover 1/3 of Italian schools performed less than 75%of learning and qualifying activities specified in Ministerial Decree of August 2005. In particular, data analysis showed considerable differences among Italian postgraduate schools. Finally, in 2015 only four Italian Universities (Napoli Federico II, Palermo, Pavia, Roma Tor Vergata) provide for the Second Level Master qualify for the functions of occupational doctor. This offer makes available 60 positions against a request of over 200 future Public Health medical doctors who have shown interest in the Master. In Italy, after the introduction of Ministerial Decree 285/2005, the educational course of PHMRs was significantly improved. The standardization of learning and qualifying activities allowed for the first time the attendance at medical directions or Local Health Units. Nevertheless, the excessive lenght of postgradute schools and the differences about training among Italian Universities are critical and actual issue. Moreover, the remarkable interest shown by PHMRs in the Master could suggest a poor job replacement prospect for young medical specialist in Hygiene, Preventive Medicine and Public Health.

Drying process optimization for an API solvate using heat transfer model of an agitated filter dryer.

PubMed

Nere, Nandkishor K; Allen, Kimberley C; Marek, James C; Bordawekar, Shailendra V

2012-10-01

Drying an early stage active pharmaceutical ingredient candidate required excessively long cycle times in a pilot plant agitated filter dryer. The key to faster drying is to ensure sufficient heat transfer and minimize mass transfer limitations. Designing the right mixing protocol is of utmost importance to achieve efficient heat transfer. To this order, a composite model was developed for the removal of bound solvent that incorporates models for heat transfer and desolvation kinetics. The proposed heat transfer model differs from previously reported models in two respects: it accounts for the effects of a gas gap between the vessel wall and solids on the overall heat transfer coefficient, and headspace pressure on the mean free path length of the inert gas and thereby on the heat transfer between the vessel wall and the first layer of solids. A computational methodology was developed incorporating the effects of mixing and headspace pressure to simulate the drying profile using a modified model framework within the Dynochem software. A dryer operational protocol was designed based on the desolvation kinetics, thermal stability studies of wet and dry cake, and the understanding gained through model simulations, resulting in a multifold reduction in drying time. Copyright © 2012 Wiley-Liss, Inc.

[Structure and function of Fenshuijiang Reservoir ecosystem based on the analysis with Ecopath model].

PubMed

Wu, Zhen; Jia, Pei-Qiao; Hu, Zhong-Jun; Chen, Li-Qiao; Gu, Zhi-Min; Liu, Qi-Gen

2012-03-01

Based on the 2008-2009 survey data of fishery resources and eco-environment of Fenshuijiang Reservoir, a mass balance model for the Reservoir ecosystem was constructed by Ecopath with Ecosim software. The model was composed of 14 functional groups, including silver carp, bighead carp, Hemibarbus maculates, Cutler alburnus, Microlepis and other fishes, Oligochaeta, aquatic insect, zooplankton, phytoplankton, and organic detritus, etc. , being able to better simulate Fenshuijiang Reservoir ecosystem. In this ecosystem, there were five trophic levels (TLs), and the nutrient flow mainly occurred in the first three TLs. Grazing and detritus food chains were the main energy flows in the ecosystem, but the food web was simpler and susceptible to be disturbed by outer environment. The transfer efficiency at lower TLs was relatively low, indicating that the ecosystem had a lower capability in energy utilization, and the excessive stock of nutrients in the ecosystem could lead to eutrophication. The lower connectance index, system omnivory index, Finn' s cycled index, and Finn's mean path length demonstrated that the ecosystem was unstable, while the high ecosystem property indices such as Pp/R and Pp/B showed that the ecosystem was immature and highly productive. It was suggested that Fenshuijiang Reservoir was still a developing new reservoir ecosystem, with a very short history and comparatively high primary productivity.

Rod Photopigment Kinetics After Photodisruption of the Retinal Pigment Epithelium

PubMed Central

Masella, Benjamin D.; Hunter, Jennifer J.; Williams, David R.

2014-01-01

Purpose. Advances in retinal imaging have led to the discovery of long-lasting retinal changes caused by light exposures below published safety limits, including disruption of the RPE. To investigate the functional consequences of RPE disruption, we combined adaptive optics ophthalmoscopy with retinal densitometry. Methods. A modified adaptive optics scanning light ophthalmoscope (AOSLO) measured the apparent density and regeneration rate of rhodopsin in two macaques before and after four different 568-nm retinal radiant exposures (RREs; 400–3200 J/cm2). Optical coherence tomography (OCT) was used to measure the optical path length through the photoreceptor outer segments before and after RPE disruption. Results. All tested RREs caused visible RPE disruption. Apparent rhodopsin density was significantly reduced following 1600 (P = 0.01) and 3200 J/cm2 (P = 0.007) exposures. No significant change in apparent density was observed in response to 800 J/cm2. Surprisingly, exposure to 400 J/cm2 showed a significant increase in apparent density (P = 0.047). Rhodopsin recovery rate was not significantly affected by these RREs. Optical coherence tomography measurements showed a significant decrease in the optical path length through the photoreceptor outer segments for RREs above 800 J/cm2 (P < 0.001). Conclusions. At higher RREs, optical path length through the outer segments was reduced. However, the rate of photopigment regeneration was unchanged. While some ambiguity remains as to the correlation between measured reflectivity and absolute rhodopsin density; at the lowest RREs, RPE disruption appears not to be accompanied by a loss of apparent rhodopsin density, which would have been indicative of functional loss. PMID:25316724

Long-range and depth-selective imaging of macroscopic targets using low-coherence and wide-field interferometry (Conference Presentation)

NASA Astrophysics Data System (ADS)

Woo, Sungsoo; Kang, Sungsam; Yoon, Changhyeong; Choi, Wonshik

2016-03-01

With the advancement of 3D display technology, 3D imaging of macroscopic objects has drawn much attention as they provide the contents to display. The most widely used imaging methods include a depth camera, which measures time of flight for the depth discrimination, and various structured illumination techniques. However, these existing methods have poor depth resolution, which makes imaging complicated structures a difficult task. In order to resolve this issue, we propose an imaging system based upon low-coherence interferometry and off-axis digital holographic imaging. By using light source with coherence length of 200 micro, we achieved the depth resolution of 100 micro. In order to map the macroscopic objects with this high axial resolution, we installed a pair of prisms in the reference beam path for the long-range scanning of the optical path length. Specifically, one prism was fixed in position, and the other prism was mounted on a translation stage and translated in parallel to the first prism. Due to the multiple internal reflections between the two prisms, the overall path length was elongated by a factor of 50. In this way, we could cover a depth range more than 1 meter. In addition, we employed multiple speckle illuminations and incoherent averaging of the acquired holographic images for reducing the specular reflections from the target surface. Using this newly developed system, we performed imaging targets with multiple different layers and demonstrated imaging targets hidden behind the scattering layers. The method was also applied to imaging targets located around the corner.

The influence of different training schedules on the learning of psychomotor skills for endoscopic surgery.

PubMed

Verdaasdonk, E G G; Stassen, L P S; van Wijk, R P J; Dankelman, J

2007-02-01

Psychomotor skills for endoscopic surgery can be trained with virtual reality simulators. Distributed training is more effective than massed training, but it is unclear whether distributed training over several days is more effective than distributed training within 1 day. This study aimed to determine which of these two options is the most effective for training endoscopic psychomotor skills. Students with no endoscopic experience were randomly assigned either to distributed training on 3 consecutive days (group A, n = 10) or distributed training within 1 day (group B, n = 10). For this study the SIMENDO virtual reality simulator for endoscopic skills was used. The training involved 12 repetitions of three different exercises (drop balls, needle manipulation, 30 degree endoscope) in differently distributed training schedules. All the participants performed a posttraining test (posttest) for the trained tasks 7 days after the training. The parameters measured were time, nontarget environment collisions, and instrument path length. There were no significant differences between the groups in the first training session for all the parameters. In the posttest, group A (training over several days) performed 18.7% faster than group B (training on 1 day) (p = 0.013). The collision and path length scores for group A did not differ significantly from the scores for group B. The distributed group trained over several days was faster, with the same number of errors and the same instrument path length used. Psychomotor skill training for endoscopic surgery distributed over several days is superior to training on 1 day.

Cortical brain connectivity evaluated by graph theory in dementia: a correlation study between functional and structural data.

PubMed

Vecchio, Fabrizio; Miraglia, Francesca; Curcio, Giuseppe; Altavilla, Riccardo; Scrascia, Federica; Giambattistelli, Federica; Quattrocchi, Carlo Cosimo; Bramanti, Placido; Vernieri, Fabrizio; Rossini, Paolo Maria

2015-01-01

A relatively new approach to brain function in neuroscience is the "functional connectivity", namely the synchrony in time of activity in anatomically-distinct but functionally-collaborating brain regions. On the other hand, diffusion tensor imaging (DTI) is a recently developed magnetic resonance imaging (MRI)-based technique with the capability to detect brain structural connection with fractional anisotropy (FA) identification. FA decrease has been observed in the corpus callosum of subjects with Alzheimer's disease (AD) and mild cognitive impairment (MCI, an AD prodromal stage). Corpus callosum splenium DTI abnormalities are thought to be associated with functional disconnections among cortical areas. This study aimed to investigate possible correlations between structural damage, measured by MRI-DTI, and functional abnormalities of brain integration, measured by characteristic path length detected in resting state EEG source activity (40 participants: 9 healthy controls, 10 MCI, 10 mild AD, 11 moderate AD). For each subject, undirected and weighted brain network was built to evaluate graph core measures. eLORETA lagged linear connectivity values were used as weight of the edges of the network. Results showed that callosal FA reduction is associated to a loss of brain interhemispheric functional connectivity characterized by increased delta and decreased alpha path length. These findings suggest that "global" (average network shortest path length representing an index of how efficient is the information transfer between two parts of the network) functional measure can reflect the reduction of fiber connecting the two hemispheres as revealed by DTI analysis and also anticipate in time this structural loss.

Effects of chronic centrifugation on mice

NASA Technical Reports Server (NTRS)

Janer, L.; Duke, J.

1984-01-01

Previous studies have shown that exposure to excess gravity in vitro alters the developmental sequence in embryonic mouse limbs and palates (Duke, Janer and Campbell, 1984; Duke, 1983). The effects of excess gravity on in vivo mammalian development was investigated using a small animal centrifuge. Four-week old female mice exposed to excess gravities of 1.8-3.5 G for eight weeks weighed significantly less than controls. Mice were mated after five weeks of adaptation to excess G, and sacrificed either at gestational day 12 or 18. There were fewer pregnancies in the centrifuged group (4/36) than in controls (9/31), and crown rump lengths (CRL) of embryos developing in the centrifuge were less than CRLs of 1-G embryos. These results show that although immersed in amniotic fluid, embryos are responsive to Delta-G.

Study of molecular interactions in binary mixtures of 2-chloro-4'methoxy benzoin with various solvents through ultrasonic speed measurements

NASA Astrophysics Data System (ADS)

Thanuja, B.; Kanakam, C.; Nithya, G.

2013-12-01

Density ( ρ) and ultrasonic velocity ( U), for binary mixtures of 2-chloro-4'-methoxy benzoin with ethanol, chloroform, acetonitrile, benzene and 1,4-dioxane of different compositions have been measured at 298 K and explanation of solute solvent interactions and effect of polarity of the solvent on type of interactions are presented in this paper. From the above data, adiabatic compressibility ( β), intermolecular free length ( L f ) and relative association ( R A ) have been calculated. Other useful parameters such as excess density, excess velocity, excess intermolecular freelength and excess adiabatic compressibility have also been calculated. These parameters have been used to study the nature and extent of intermolecular interactions between component molecules in present binary mixtures.

Data assimilation using a GPU accelerated path integral Monte Carlo approach

NASA Astrophysics Data System (ADS)

Quinn, John C.; Abarbanel, Henry D. I.

2011-09-01

The answers to data assimilation questions can be expressed as path integrals over all possible state and parameter histories. We show how these path integrals can be evaluated numerically using a Markov Chain Monte Carlo method designed to run in parallel on a graphics processing unit (GPU). We demonstrate the application of the method to an example with a transmembrane voltage time series of a simulated neuron as an input, and using a Hodgkin-Huxley neuron model. By taking advantage of GPU computing, we gain a parallel speedup factor of up to about 300, compared to an equivalent serial computation on a CPU, with performance increasing as the length of the observation time used for data assimilation increases.

Graphs and Enhancing Maple Multiplication.

ERIC Educational Resources Information Center

Cecil, David R.; Wang, Rongdong

2002-01-01

Description of a technique in Maple programming language that automatically prints all paths of any desired length along with the name of each vertex, proceeding in order from the beginning vertex to the ending vertex for a given graph. (Author/MM)

The effect of suspended sediment and color on ultraviolet spectrophotometric nitrate sensors

USGS Publications Warehouse

Snazelle, Teri T.

2016-03-08

Four commercially available ultraviolet nitrate spectrophotometric sensors were evaluated by the U.S. Geological Survey Hydrologic Instrumentation Facility (HIF) to determine the effects of suspended sediment concentration (SSC) and colored dissolved organic matter (CDOM) on sensor accuracy. The evaluated sensors were: the Hach NITRATAX plus sc (5-millimeters (mm) path length), Hach NITRATAX plus sc (2 mm), S::CAN Spectro::lyser (5 mm), and the Satlantic SUNA V2 (5 mm). A National Institute of Standards and Technology-traceable nitrate-free sediment standard was purchased and used to create the turbid environment, and an easily made filtered tea solution was used for the CDOM test. All four sensors performed well in the test that evaluated the effect of suspended sediment on accuracy. The Hach 5 mm, Hach 2 mm, and the SUNA V2 met their respective manufacturer accuracy specifications up to concentrations of 4,500 milligrams per liter (mg/L) SSC. The S::CAN failed to meet its accuracy specifications when the SSC concentrations exceeded 4,000 mg/L. Test results from the effect of CDOM on accuracy indicated a significant skewing of data from all four sensors and showed an artificial elevation of measured nitrate to varying amounts. Of the four sensors tested, the Satlantic SUNA V2’s accuracy was affected the least in the CDOM test. The nitrate concentration measured by the SUNA V2 was approximately 24 percent higher than the actual concentration when estimated total organic carbon values exceeded 44 mg/L. Measured nitrate concentration falsely increased 49 percent when measured by the Hach 5 mm, and 75 percent when measured by the Hach 2 mm. The S::CAN’s reported nitrate concentration increased 96 percent. Path length plays an important role in the sensor’s ability to compensate measurements for matrix interferences, but does not solely determine how well a sensor can handle all interferences. The sensor’s proprietary algorithms also play a key role in matrix interference compensation. The sensors’ ability to compensate for CDOM varied significantly during the tests, even among the three with 5-mm path lengths. Results of this evaluation suggest that the proprietary algorithms of the nitrate analyzers are more effective compensating for suspended sediment, and less effective compensating for CDOM (color) when sensor path length remains constant.

Effects of AEA Cell-Bypass-Switch Closure on Charged EOS-Aqua NiH2 Cell

NASA Technical Reports Server (NTRS)

Keys, Denney; Rao, Gopalakrishna M.; Sullivan, David; Wannemacher, Harry

2001-01-01

The nominal performance of AEA CBPD under simulated EOS-Aqua/Aura flight hardware configuration has been demonstrated. There is no evidence of cell rupture or excessive heat production during or after CBPD switch activation under simulated high cell impedance (open-circuit cell failure mode). Inadvertent CBPD switch activation with a charged cell (low impedance path) intermittently closes and opens up the switch, therefore the device may or may not provide protection against future open-circuit cell failure. Further testing with switches F01 and F02 may provide clarification. The formation of a continuous low impedance path (a homogeneous low melting point alloy), has been confirmed - which is the expected mode of operation.

Developing a phenomenological model of the proton trajectory within a heterogeneous medium required for proton imaging.

PubMed

Fekete, Charles-Antoine Collins; Doolan, Paul; Dias, Marta F; Beaulieu, Luc; Seco, Joao

2015-07-07

To develop an accurate phenomenological model of the cubic spline path estimate of the proton path, accounting for the initial proton energy and water equivalent thickness (WET) traversed. Monte Carlo (MC) simulations were used to calculate the path of protons crossing various WET (10-30 cm) of different material (LN300, water and CB2-50% CaCO3) for a range of initial energies (180-330 MeV). For each MC trajectory, cubic spline trajectories (CST) were constructed based on the entrance and exit information of the protons and compared with the MC using the root mean square (RMS) metric. The CST path is dependent on the direction vector magnitudes (|P0,1|). First, |P0,1| is set to the proton path length (with factor Λ(Norm)(0,1) = 1.0). Then, two optimal factor Λ(0,1) are introduced in |P0,1|. The factors are varied to minimize the RMS difference with MC paths for every configuration. A set of Λ(opt)(0,1) factors, function of WET/water equivalent path length (WEPL), that minimizes the RMS are presented. MTF analysis is then performed on proton radiographs of a line-pair phantom reconstructed using the CST trajectories. Λ(opt)(0,1) was fitted to the WET/WEPL ratio using a quadratic function (Y = A + BX(2) where A = 1.01,0.99, B = 0.43,-  0.46 respectively for Λ(opt)(0), Λ(opt)(1)). The RMS deviation calculated along the path, between the CST and the MC, increases with the WET. The increase is larger when using Λ(Norm)(0,1) than Λ(opt)(0,1) (difference of 5.0% with WET/WEPL = 0.66). For 230/330 MeV protons, the MTF10% was found to increase by 40/16% respectively for a thin phantom (15 cm) when using the Λ(opt)(0,1) model compared to the Λ(Norm)(0,1) model. Calculation times for Λ(opt)(0,1) are scaled down compared to MLP and RMS deviation are similar within standard deviation.B ased on the results of this study, using CST with the Λ(opt)(0,1) factors reduces the RMS deviation and increases the spatial resolution when reconstructing proton trajectories.

Effect of wet tropospheric path delays on estimation of geodetic baselines in the Gulf of California using the Global Positioning System

NASA Technical Reports Server (NTRS)

Tralli, David M.; Dixon, Timothy H.; Stephens, Scott A.

1988-01-01

Surface Meteorological (SM) and Water Vapor Radiometer (WVR) measurements are used to provide an independent means of calibrating the GPS signal for the wet tropospheric path delay in a study of geodetic baseline measurements in the Gulf of California using GPS in which high tropospheric water vapor content yielded wet path delays in excess of 20 cm at zenith. Residual wet delays at zenith are estimated as constants and as first-order exponentially correlated stochastic processes. Calibration with WVR data is found to yield the best repeatabilities, with improved results possible if combined carrier phase and pseudorange data are used. Although SM measurements can introduce significant errors in baseline solutions if used with a simple atmospheric model and estimation of residual zenith delays as constants, SM calibration and stochastic estimation for residual zenith wet delays may be adequate for precise estimation of GPS baselines. For dry locations, WVRs may not be required to accurately model tropospheric effects on GPS baselines.

Assessment of Masonry Buildings Subjected to Landslide-Induced Settlements: From Load Path Method to Evolutionary Optimization Method

NASA Astrophysics Data System (ADS)

Palmisano, Fabrizio; Elia, Angelo

2017-10-01

One of the main difficulties, when dealing with landslide structural vulnerability, is the diagnosis of the causes of crack patterns. This is also due to the excessive complexity of models based on classical structural mechanics that makes them inappropriate especially when there is the necessity to perform a rapid vulnerability assessment at the territorial scale. This is why, a new approach, based on a ‘simple model’ (i.e. the Load Path Method, LPM), has been proposed by Palmisano and Elia for the interpretation of the behaviour of masonry buildings subjected to landslide-induced settlements. However, the LPM is very useful for rapidly finding the 'most plausible solution' instead of the exact solution. To find the solution, optimization algorithms are necessary. In this scenario, this article aims to show how the Bidirectional Evolutionary Structural Optimization method by Huang and Xie, can be very useful to optimize the strut-and-tie models obtained by using the Load Path Method.

Solar corona electron density distribution

NASA Astrophysics Data System (ADS)

Esposito, P. B.; Edenhofer, P.; Lueneburg, E.

1980-07-01

The paper discusses the three and one-half months of single-frequency time delay data which were acquired from the Helios 2 spacecraft around the time of its solar occultation. The excess time delay due to integrated effect of free electrons along the signal's ray path could be separated and modeled following the determination of the spacecraft trajectory. An average solar corona and equatorial electron density profile during solar minimum were deduced from the time delay measurements acquired within 5-60 solar radii of the sun. As a point of reference at 10 solar radii from the sun, an average electron density was 4500 el/cu cm. However, an asymmetry was found in the electron density as the ray path moved from the west to east solar limb. This may be related to the fact that during entry into occultation the heliographic latitude of the ray path was about 6 deg, while during exit it was 7 deg. The Helios density model is compared with similar models deduced from different experimental techniques.

Visualizing sound emission of elephant vocalizations: evidence for two rumble production types.

PubMed

Stoeger, Angela S; Heilmann, Gunnar; Zeppelzauer, Matthias; Ganswindt, André; Hensman, Sean; Charlton, Benjamin D

2012-01-01

Recent comparative data reveal that formant frequencies are cues to body size in animals, due to a close relationship between formant frequency spacing, vocal tract length and overall body size. Accordingly, intriguing morphological adaptations to elongate the vocal tract in order to lower formants occur in several species, with the size exaggeration hypothesis being proposed to justify most of these observations. While the elephant trunk is strongly implicated to account for the low formants of elephant rumbles, it is unknown whether elephants emit these vocalizations exclusively through the trunk, or whether the mouth is also involved in rumble production. In this study we used a sound visualization method (an acoustic camera) to record rumbles of five captive African elephants during spatial separation and subsequent bonding situations. Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences: a nasally- and an orally-emitted rumble. Interestingly, nasal rumbles predominated during contact calling, whereas oral rumbles were mainly produced in bonding situations. In addition, nasal and oral rumbles varied considerably in their acoustic structure. In particular, the values of the first two formants reflected the estimated lengths of the vocal paths, corresponding to a vocal tract length of around 2 meters for nasal, and around 0.7 meters for oral rumbles. These results suggest that African elephants may be switching vocal paths to actively vary vocal tract length (with considerable variation in formants) according to context, and call for further research investigating the function of formant modulation in elephant vocalizations. Furthermore, by confirming the use of the elephant trunk in long distance rumble production, our findings provide an explanation for the extremely low formants in these calls, and may also indicate that formant lowering functions to increase call propagation distances in this species'.

Visualizing Sound Emission of Elephant Vocalizations: Evidence for Two Rumble Production Types

PubMed Central

Stoeger, Angela S.; Heilmann, Gunnar; Zeppelzauer, Matthias; Ganswindt, André; Hensman, Sean; Charlton, Benjamin D.

2012-01-01

Recent comparative data reveal that formant frequencies are cues to body size in animals, due to a close relationship between formant frequency spacing, vocal tract length and overall body size. Accordingly, intriguing morphological adaptations to elongate the vocal tract in order to lower formants occur in several species, with the size exaggeration hypothesis being proposed to justify most of these observations. While the elephant trunk is strongly implicated to account for the low formants of elephant rumbles, it is unknown whether elephants emit these vocalizations exclusively through the trunk, or whether the mouth is also involved in rumble production. In this study we used a sound visualization method (an acoustic camera) to record rumbles of five captive African elephants during spatial separation and subsequent bonding situations. Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences: a nasally- and an orally-emitted rumble. Interestingly, nasal rumbles predominated during contact calling, whereas oral rumbles were mainly produced in bonding situations. In addition, nasal and oral rumbles varied considerably in their acoustic structure. In particular, the values of the first two formants reflected the estimated lengths of the vocal paths, corresponding to a vocal tract length of around 2 meters for nasal, and around 0.7 meters for oral rumbles. These results suggest that African elephants may be switching vocal paths to actively vary vocal tract length (with considerable variation in formants) according to context, and call for further research investigating the function of formant modulation in elephant vocalizations. Furthermore, by confirming the use of the elephant trunk in long distance rumble production, our findings provide an explanation for the extremely low formants in these calls, and may also indicate that formant lowering functions to increase call propagation distances in this species'. PMID:23155427

Image-rotating, 4-mirror, ring optical parametric oscillator

DOEpatents

Smith, Arlee V.; Armstrong, Darrell J.

2004-08-10

A device for optical parametric amplification utilizing four mirrors oriented in a nonplanar configuration where the optical plane formed by two of the mirrors is orthogonal to the optical plane formed by the other two mirrors and with the ratio of lengths of the laser beam paths approximately constant regardless of the scale of the device. With a cavity length of less than approximately 110 mm, a conversion efficiency of greater than 45% can be achieved.

Assessment of the transport routes of oversized and excessive loads in relation to the passage through roundabout

NASA Astrophysics Data System (ADS)

Petru, Jan; Dolezel, Jiri; Krivda, Vladislav

2017-09-01

In the past the excessive and oversized loads were realized on selected routes on roads that were adapted to ensure smooth passage of transport. Over the years, keeping the passages was abandoned and currently there are no earmarked routes which would be adapted for such type of transportation. The routes of excessive and oversized loads are currently planned to ensure passage of the vehicle through the critical points on the roads. Critical points are level and fly-over crossings of roads, bridges, toll gates, traffic signs and electrical and other lines. The article deals with the probability assessment of selected critical points of the route of the excessive load on the roads of 1st class, in relation to ensuring the passage through the roundabout. The bases for assessing the passage of the vehicle with excessive load through a roundabout are long-term results of video analyses of monitoring the movement of transports on similar intersections and determination of the theoretical probability model of vehicle movement at selected junctions. On the basis of a virtual simulation of the vehicle movement at crossroads and using MonteCarlo simulation method vehicles’ paths are analysed and the probability of exit of the vehicle outside the crossroad in given junctions is quantified.

Method and Apparatus for Reducing the Vulnerability of Latches to Single Event Upsets

NASA Technical Reports Server (NTRS)

Shuler, Robert L., Jr. (Inventor)

2002-01-01

A delay circuit includes a first network having an input and an output node, a second network having an input and an output, the input of the second network being coupled to the output node of the first network. The first network and the second network are configured such that: a glitch at the input to the first network having a length of approximately one-half of a standard glitch time or less does not cause the voltage at the output of the second network to cross a threshold, a glitch at the input to the first network having a length of between approximately one-half and two standard glitch times causes the voltage at the output of the second network to cross the threshold for less than the length of the glitch, and a glitch at the input to the first network having a length of greater than approximately two standard glitch times causes the voltage at the output of the second network to cross the threshold for approximately the time of the glitch. The method reduces the vulnerability of a latch to single event upsets. The latch includes a gate having an input and an output and a feedback path from the output to the input of the gate. The method includes inserting a delay into the feedback path and providing a delay in the gate.

Method and Apparatus for Reducing the Vulnerability of Latches to Single Event Upsets

NASA Technical Reports Server (NTRS)

Shuler, Robert L., Jr. (Inventor)

2002-01-01

A delay circuit includes a first network having an input and an output node, a second network having an input and an output, the input of the second network being coupled to the output node of the first network. The first network and the second network are configured such that: a glitch at the input to the first network having a length of approximately one-half of a standard glitch time or less does not cause tile voltage at the output of the second network to cross a threshold, a glitch at the input to the first network having a length of between approximately one-half and two standard glitch times causes the voltage at the output of the second network to cross the threshold for less than the length of the glitch, and a glitch at the input to the first network having a length of greater than approximately two standard glitch times causes the voltage at the output of the second network to cross the threshold for approximately the time of the glitch. A method reduces the vulnerability of a latch to single event upsets. The latch includes a gate having an input and an output and a feedback path from the output to the input of the gate. The method includes inserting a delay into the feedback path and providing a delay in the gate.

Enhanced characteristics of blue InGaN /GaN light-emitting diodes by using selective activation to modulate the lateral current spreading length

NASA Astrophysics Data System (ADS)

Lin, Ray-Ming; Lu, Yuan-Chieh; Chou, Yi-Lun; Chen, Guo-Hsing; Lin, Yung-Hsiang; Wu, Meng-Chyi

2008-06-01

We have studied the characteristics of blue InGaN /GaN multiquantum-well light-emitting diodes (LEDs) after reducing the length of the lateral current path through the transparent layer through formation of a peripheral high-resistance current-blocking region in the Mg-doped GaN layer. To study the mechanism of selective activation in the Mg-doped GaN layer, we deposited titanium (Ti), gold (Au), Ti /Au, silver, and copper individually onto the Mg-doped GaN layer and investigated their effects on the hole concentration in the p-GaN layer. The Mg-doped GaN layer capped with Ti effectively depressed the hole concentration in the p-GaN layer by over one order of magnitude relative to that of the as-grown layer. This may suggest that high resistive regions are formed by diffusion of Ti and depth of high resistive region from the p-GaN surface depends on the capped Ti film thickness. Selective activation of the Mg-doped GaN layer could be used to modulate the length of the lateral current path. Furthermore, the external quantum efficiency of the LEDs was improved significantly after reducing the lateral current spreading length. In our best result, the external quantum efficiency was 52.3% higher (at 100mA) than that of the as-grown blue LEDs.

Musical motor feedback (MMF) in walking hemiparetic stroke patients: randomized trials of gait improvement.

PubMed

Schauer, Michael; Mauritz, Karl-Heinz

2003-11-01

To demonstrate the effect of rhythmical auditory stimulation in a musical context for gait therapy in hemiparetic stroke patients, when the stimulation is played back measure by measure initiated by the patient's heel-strikes (musical motor feedback). Does this type of musical feedback improve walking more than a less specific gait therapy? The randomized controlled trial considered 23 registered stroke patients. Two groups were created by randomization: the control group received 15 sessions of conventional gait therapy and the test group received 15 therapy sessions with musical motor feedback. Inpatient rehabilitation hospital. Median post-stroke interval was 44 days and the patients were able to walk without technical aids with a speed of approximately 0.71 m/s. Gait velocity, step duration, gait symmetry, stride length and foot rollover path length (heel-on-toe-off distance). The test group showed more mean improvement than the control group: stride length increased by 18% versus 0%, symmetry deviation decreased by 58% versus 20%, walking speed increased by 27% versus 4% and rollover path length increased by 28% versus 11%. Musical motor feedback improves the stroke patient's walk in selected parameters more than conventional gait therapy. A fixed memory in the patient's mind about the song and its timing may stimulate the improvement of gait even without the presence of an external pacemaker.

Mechanotransduction, asthma, and airway smooth muscle

PubMed Central

Fabry, Ben; Fredberg, Jeffrey J.

2008-01-01

Excessive force generation by airway smooth muscle is the main culprit in excessive airway narrowing during an asthma attack. The maximum force the airway smooth muscle can generate is exquisitely sensitive to muscle length fluctuations during breathing, and is governed by complex mechanotransduction events that can best be studied by a hybrid approach in which the airway wall is modeled in silico so as to set a dynamic muscle load comparable to that experienced in vivo. PMID:18836522

Gestational Weight Gain and Offspring Longitudinal Growth in Early Life.

PubMed

Diesel, Jill C; Eckhardt, Cara L; Day, Nancy L; Brooks, Maria M; Arslanian, Silva A; Bodnar, Lisa M

2015-01-01

Excessive gestational weight gain (GWG) increases the risk of childhood obesity, but little is known about its association with infant growth patterns. The aim of this study was to examine the association between GWG and infant growth patterns. Pregnant women (n = 743) self-reported GWG at delivery, which we classified as inadequate, adequate or excessive based on the current guidelines. Offspring weight-for-age z-score (WAZ), length-for-age z-score (LAZ (with height-for-age (HAZ) in place of length at 36 months)) and body mass index z-score (BMIZ) were calculated at birth, 8, 18 and 36 months using the 2006 World Health Organization growth standards. Linear mixed models estimated the change in z-score from birth to 36 months by GWG. The mean (SD) WAZ was -0.22 (1.20) at birth. Overall, WAZ and BMIZ increased from birth to, approximately, 24 months and decreased from 24 to 36 months, while LAZ/HAZ decreased from birth through 36 months. Excessive GWG was associated with higher offspring WAZ and BMIZ at birth, 8 and 36 months, and higher HAZ at 36 months, compared with adequate GWG. Compared with the same referent, inadequate GWG was associated with smaller WAZ and BMIZ at birth and 8 months. Excessive GWG may predispose infants to obesogenic growth patterns, while inadequate GWG may not have a lasting impact on infant growth.

Gestational weight gain and offspring longitudinal growth in early life

PubMed Central

Diesel, Jill C.; Eckhardt, Cara L.; Day, Nancy L.; Brooks, Maria M.; Arslanian, Silva A.; Bodnar, Lisa M.

2015-01-01

Background Excessive gestational weight gain (GWG) increases the risk of childhood obesity, but little is known about its association with infant growth patterns. Aim To examine the GWG-infant growth association. Methods Pregnant women (n=743) self-reported GWG at delivery, which we classified as inadequate, adequate, or excessive based on current guidelines. Offspring weight-for-age z-scores (WAZ), length-for-age z-scores (LAZ (with height-for-age (HAZ) in place of length at 36 months)), and body mass index z-scores (BMIZ) were calculated at birth, 8, 18, and 36 months using the 2006 WHO growth standards. Linear mixed models estimated the change in z-scores from birth to 36 months by GWG. Results The mean (SD) WAZ was −0.22 (1.20) at birth. Overall, WAZ and BMIZ increased from birth to approximately 24 months and decreased from 24 to 36 months, while LAZ/HAZ decreased from birth through 36 months. Excessive GWG was associated with higher offspring WAZ and BMIZ at birth, 8, and 36 months, and higher HAZ at 36 months, compared with adequate GWG. Compared with the same referent, inadequate GWG was associated with smaller WAZ and BMIZ at birth and 8 months. Conclusion Excessive GWG may predispose infants to obesogenic growth patterns while inadequate GWG may not have a lasting impact on infant growth. PMID:26279171

Postural Control Characteristics during Single Leg Standing of Individuals with a History of Ankle Sprain: Measurements Obtained Using a Gravicorder and Head and Foot Accelerometry.

PubMed

Abe, Yota; Sugaya, Tomoaki; Sakamoto, Masaaki

2014-03-01

[Purpose] This study aimed to validate the postural control characteristics of individuals with a history of ankle sprain during single leg standing by using a gravicorder and head and foot accelerometry. [Subjects] Twenty subjects with and 23 subjects without a history of ankle sprain (sprain and control groups, respectively) participated. [Methods] The anteroposterior, mediolateral, and total path lengths, as well as root mean square (RMS) of each length, were calculated using the gravicorder. The anteroposterior, mediolateral, and resultant acceleration of the head and foot were measured using accelerometers and were evaluated as the ratio of the acceleration of the head to the foot. [Results] There was no significant difference between the two groups in path length or RMS acceleration of the head and foot. However, the ratios of the mediolateral and resultant components were significantly higher in the sprain group than in the control group. [Conclusion] Our findings suggest that individuals with a history of ankle sprain have a higher head-to-foot acceleration ratio and different postural control characteristics than those of control subjects.

Displacement measurement with over-determined interferometer

NASA Astrophysics Data System (ADS)

Lazar, Josef; Holá, Miroslava; Hrabina, Jan; Buchta, Zdeněk.; Číp, Ondřej; Oulehla, Jindřich

2012-01-01

We present a concept combining traditional displacement incremental interferometry with a tracking refractometer following the fluctuations of the refractive index of air. This concept is represented by an interferometric system of three Michelson-type interferometers where two are arranged in a counter-measuring configuration and the third one is set to measure the changes of the fixed length, here the measuring range of the overall displacement. In this configuration the two counter-measuring interferometers have identical beam paths with proportional parts of the overall one. The fixed interferometer with its geometrical length of the measuring beam linked to a mechanical reference made of a high thermal-stability material (Zerodur) operates as a tracking refractometer monitoring the atmospheric refractive index directly in the beam path of the displacement measuring interferometers. This principle has been demonstrated experimentally through a set of measurements in a temperature controlled environment under slowly changing refractive index of air in comparison with its indirect measurement through Edlen formula. With locking of the laser optical frequency to fixed value of the overall optical length the concept can operate as an interferometric system with compensation of the fluctuations of the refractive index of air.

Site-directed protein recombination as a shortest-path problem.

PubMed

Endelman, Jeffrey B; Silberg, Jonathan J; Wang, Zhen-Gang; Arnold, Frances H

2004-07-01

Protein function can be tuned using laboratory evolution, in which one rapidly searches through a library of proteins for the properties of interest. In site-directed recombination, n crossovers are chosen in an alignment of p parents to define a set of p(n + 1) peptide fragments. These fragments are then assembled combinatorially to create a library of p(n+1) proteins. We have developed a computational algorithm to enrich these libraries in folded proteins while maintaining an appropriate level of diversity for evolution. For a given set of parents, our algorithm selects crossovers that minimize the average energy of the library, subject to constraints on the length of each fragment. This problem is equivalent to finding the shortest path between nodes in a network, for which the global minimum can be found efficiently. Our algorithm has a running time of O(N(3)p(2) + N(2)n) for a protein of length N. Adjusting the constraints on fragment length generates a set of optimized libraries with varying degrees of diversity. By comparing these optima for different sets of parents, we rapidly determine which parents yield the lowest energy libraries.

Slotting Fins of Heat Exchangers to Provide Thermal Breaks

NASA Technical Reports Server (NTRS)

Scull, Timothy D.

2003-01-01

Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.

Cavity ring-down spectroscopy in the liquid phase

NASA Astrophysics Data System (ADS)

Xu, Shucheng; Sha, Guohe; Xie, Jinchun

2002-02-01

A new application for cavity ring-down spectroscopic (CRDS) technique using a pulsed polarized light source has been developed in the absorption measurement of liquids for "colorless" organic compounds using both a single sample cell and double sample cells inserted in an optical cavity at Brewster angle. At present an experimental capability of measuring absorption coefficients as small as 2-5×10-7 cm-1 has been demonstrated by measurement of the absorption baselines. The first spectra for CRDS in the liquid phase, the C-H stretching fifth vibrational overtones of benzene in the pure liquid and hexane solution are obtained. The optical absorption length for liquids in both a single sample cell and double sample cells of 1 cm length is up to 900 cm due to multipass of light within an optical cavity. Compared to the thermal lens and optoacoustic spectroscopic techniques, the sensitivity for CRDS mainly depends on the optical absorption path of the sample (single passing path of the sample times multipass times), is not determined by the laser power and the length of the sample cell. The absolute absorption coefficient and band intensity for the sample are determined directly by the spectroscopy.

Structural optimization of the path length control mirror for ring laser gyro

NASA Astrophysics Data System (ADS)

Ma, Yanghua; Quan, Bingxin; Han, Zonghu; Wang, Jiliang

2017-02-01

The path length control mirror (PLCM) is essential for high precision ring laser gyro (RLG). In this paper the influence of the structural parameters of the PLCM on its length compensating efficiency (LCE) and the anti-transversedeformation capability(ATDC) is numerically investigated, with the aid of the finite element software ANSYS. The result shows that the inner and outer diameters as well as the thickness of the deformation slot of the PLCM have significant influences on both its LCE and ATDC, while the position of the deformation slot of the PLCM has little impact on its LCE and mainly affect its ATDC. According to the simulation, two types of PLCMs with the same parameters all but the position of deformation slot are fabricated and experimentally demonstrated, with the result showing great agreement with the simulation. That is to say, for a given overall dimension constraint, the dynamic stability of the RLG resonator can be dramatically enhanced by a proper design of the PLCM, without almost any negative impact on its LCE. This will be of great value for the optimization of the PLCM for RLG, especially for miniature RLG.

Sunrise effects on VLF signals propagating over a long north-south path

NASA Astrophysics Data System (ADS)

Clilverd, Mark A.; Thomson, Neil R.; Rodger, Craig J.

1999-07-01

We present a detailed study of the times of amplitude minima observed on the 12-Mm path from NAA (24 kHz, 1 MW, Cutler, Maine) to Faraday, Antarctica, during the period 1990-1995. (NAA is a naval transmitter call sign.) This study represents the first account of the effect of the sunrise terminator when it is parallel to a propagation path at some times of the year. Since the NAA-Faraday path is within 3° of the north-south meridian, parallel orientation happens close to the equinoxes, while the maximum angle of incidence occurs during the solstices. During the solstices the terminator takes a significant length of time to cross the entire propagation path, so modal conversion effects are observed over a range of hours. During the equinoxes, however, the leading edge of the night-day transition region crosses the whole propagation path within 20 min. The interpretation of the timing of minima is consistent with modal conversion taking place as the sunrise terminator crosses the NAA-Faraday transmission path at specific, consistent locations. The timing of minima is remarkably consistent from year to year. Long wave propagation modeling is used to show that the location of nightside minima at an altitude of 45-75 km in the subionospheric waveguide represents the location of the sunrise terminator on the great circle path when dayside minima occur.

Undersea Laser Communications Field Test at the Naval Undersea Warfare Center (NUWC)

DTIC Science & Technology

2016-08-30

and blue wavelength scenario suggests links in excess of 400 meters are achievable with small, low-power, narrow-beam lasercom terminals. The field...of 7.6 meters , which corresponded to between 8–12 beam extinction lengths. The PMT demonstration included real-time electronics to perform...communications link was demonstrated over 4.8 meters (5 beam extinction lengths) with an APD receiver. Communications and characterization data were

Alternations in burial and exhumation along the Selimiye (Kayabükü) shear zone in the Menderes Massif from detailed garnet pressure-temperature paths

NASA Astrophysics Data System (ADS)

Kelly, E. D.; Atakturk, K. R.; Catlos, E. J.; Lizzadro-McPherson, D. J.; Cemen, I.; Lovera, O. M.

2015-12-01

Pressure-temperature (P-T) paths derived from garnet chemical zoning and supported by thermal modeling record alternating burial and exhumation during Main Menderes Metamorphism in western Turkey. We studied six rocks along the Selimiye (Kayabükü) shear zone, three from the footwall (Çine nappe) and three from the hanging wall (Selimiye nappe). The shear zone bounds the southern Menderes Massif metamorphic core complex and has been suggested to record compression followed by extension. The rocks are lower-amphibolite facies garnet-bearing metapelites with nearly identical mineral suites. Retrograde overprinting hinders classical thermobarometry; to overcome this, preserved chemical zoning in garnet combined with a G-minimization approach was used to construct detailed P-T paths (e.g., 50 points in some paths). During continuous temperature increase, the Çine nappe paths show increasing, decreasing, and then increasing pressure (an N-shaped path) ending at 7-8 kbar and ~565-590 °C. The Selimiye nappe paths show a single increase in P-T ending at ~7.3 kbar and ~580 °C. Similar bulk-rock compositions in all samples and the separation by the shear zone suggest that garnets grew during distinct events in each nappe. The timing of garnet growth, and thus the P-T paths, is currently undetermined, as monazite inclusions in garnet appear secondary and complicated by excess common Pb. The Çine nappe N-shaped path describes alternations in burial and exhumation, possibly due to thrust motion along the shear zone. To demonstrate the physical plausibility of the P-T paths, a 2-D finite difference solution to the diffusion-advection equation was applied. The results of the thermal modeling suggest that thrusting, denudation, and renewed thrusting would produce similar changes in P-T to the N-shaped path. Thus, the Çine nappe N-shaped P-T path appears to record a gap in thrust motion along the Selimiye (Kayabükü) shear zone prior to ultimate unroofing of the massif.

Measuring phonon mean free path distributions by probing quasiballistic phonon transport in grating nanostructures

DOE PAGES

Zeng, Lingping; Collins, Kimberlee C.; Hu, Yongjie; ...

2015-11-27

Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domainmore » thermoreflectance measurements and simultaneously act as wiregrid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. Furthermore, this table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials.« less

Generation of RGB-D data for SLAM using robotic framework V-REP

NASA Astrophysics Data System (ADS)

Gritsenko, Pavel S.; Gritsenko, Igor S.; Seidakhmet, Askar Zh.; Abduraimov, Azizbek E.

2017-09-01

In this article, we will present a methodology to debug RGB-D SLAM systems as well as to generate testing data. We have created a model of a laboratory with an area of 250 m2 (25 × 10) with set of objects of different type. V-REP Microsoft Kinect sensor simulation model was used as a basis for robot vision system. Motion path of the sensor model has multiple loops. We have written a program in V-Rep native language Lua to record data array from the Microsoft Kinect sensor model. The array includes both RGB and Depth streams with full resolution (640 × 480) for every 10 cm of the path. The simulated path has absolute accuracy, since it is a simulation, and is represented by an array of transformation matrices (4 × 4). The length of the data array is 1000 steps or 100 m. The path simulates frequently occurring cases in SLAM, including loops. It is worth noting that the path was modeled for a mobile robot and it is represented by a 2D path parallel to the floor at a height of 40 cm.

Algebraic Approaches for Scalable End-to-End Monitoring and Diagnosis

NASA Astrophysics Data System (ADS)

Zhao, Yao; Chen, Yan

The rigidity of the Internet architecture led to flourish in the research of end-to-end based systems. In this chapter, we describe a linear algebra-based end-to-end monitoring and diagnosis system. We first propose a tomography-based overlay monitoring system (TOM). Given n end hosts, TOM selectively monitors a basis set of O(nlogn) paths out of all n(n - 1) end-to-end paths. Any end-to-end path can be written as a unique linear combination of paths in the basis set. Consequently, by monitoring loss rates for the paths in the basis set, TOM infers loss rates for all end-to-end paths. Furthermore, leveraging on the scalable measurements from the TOM system, we propose the Least-biased End-to-End Network Diagnosis (in short, LEND) system. We define a minimal identifiable link sequence (MILS) as a link sequence of minimal length whose properties can be uniquely identified from end-to-end measurements. LEND applies an algebraic approach to find out the MILSes and infers the properties of the MILSes efficiently. This also means LEND system achieves the finest diagnosis granularity under the least biased statistical assumptions.

Some design considerations for a synthetic aperture optical telescope array

NASA Astrophysics Data System (ADS)

Scott, P. W.

1984-01-01

Several design considerations inherent in the configuration of phased array transmission of multiwavelength laser beams are discussed. Attention is focused on the U.S.A.F. phased array (PHASAR) demonstration project, where problems have been encountered in dividing the beam(s), controlling the optical path differences between subapertures, and expanding individual beams.A piston-driven path length adjustment mechanism has been selected, along with an active control system and proven components for stability maintenance. The necessity of developing broadband, high reflectivity low phase shift coatings for the system mirrors is stressed.

ALMA Long Baseline Campaigns: Phase Characteristics of Atmosphere at Long Baselines in the Millimeter and Submillimeter Wavelengths

NASA Astrophysics Data System (ADS)

Matsushita, Satoki; Asaki, Yoshiharu; Fomalont, Edward B.; Morita, Koh-Ichiro; Barkats, Denis; Hills, Richard E.; Kawabe, Ryohei; Maud, Luke T.; Nikolic, Bojan; Tilanus, Remo P. J.; Vlahakis, Catherine; Whyborn, Nicholas D.

2017-03-01

We present millimeter- and submillimeter-wave phase characteristics measured between 2012 and 2014 of Atacama Large Millimeter/submillimeter Array long baseline campaigns. This paper presents the first detailed investigation of the characteristics of phase fluctuation and phase correction methods obtained with baseline lengths up to ˜15 km. The basic phase fluctuation characteristics can be expressed with the spatial structure function (SSF). Most of the SSFs show that the phase fluctuation increases as a function of baseline length, with a power-law slope of ˜0.6. In many cases, we find that the slope becomes shallower (average of ˜0.2-0.3) at baseline lengths longer than ˜1 km, namely showing a turn-over in SSF. These power law slopes do not change with the amount of precipitable water vapor (PWV), but the fitted constants have a weak correlation with PWV, so that the phase fluctuation at a baseline length of 10 km also increases as a function of PWV. The phase correction method using water vapor radiometers (WVRs) works well, especially for the cases where PWV > 1 {mm}, which reduces the degree of phase fluctuations by a factor of two in many cases. However, phase fluctuations still remain after the WVR phase correction, suggesting the existence of other turbulent constituent that cause the phase fluctuation. This is supported by occasional SSFs that do not exhibit any turn-over; these are only seen when the PWV is low (i.e., when the WVR phase correction works less effectively) or after WVR phase correction. This means that the phase fluctuation caused by this turbulent constituent is inherently smaller than that caused by water vapor. Since in these rare cases there is no turn-over in the SSF up to the maximum baseline length of ˜15 km, this turbulent constituent must have scale height of 10 km or more, and thus cannot be water vapor, whose scale height is around 1 km. Based on the characteristics, this large scale height turbulent constituent is likely to be water ice or a dry component. Excess path length fluctuation after the WVR phase correction at a baseline length of 10 km is large (≳ 200 μ {{m}}), which is significant for high frequency (> 450 {GHz} or < 700 μ {{m}}) observations. These results suggest the need for an additional phase correction method to reduce the degree of phase fluctuation, such as fast switching, in addition to the WVR phase correction. We simulated the fast switching phase correction method using observations of single quasars, and the result suggests that it works well, with shorter cycle times linearly improving the coherence.

ESO and Fokker Space Sign Contract about VLTI Delay Line

NASA Astrophysics Data System (ADS)

1998-03-01

The European Southern Observatory is building the world's largest optical telescope, the Very Large Telescope (VLT) , at the ESO Paranal Observatory in Chile. The VLT consists of four 8.2-m unit telescopes and several smaller, moveable Auxiliary Telescopes. When coupled as the giant VLT Interferometer (VLTI) , they will together provide the sharpest images ever obtained by any optical telescope. It will in principle be able to see an astronaut on the surface of the Moon, 400,000 km away. The VLTI Delay Lines Fokker Space (Leiden, The Netherlands) has been awarded a contract for the delivery of the Delay Line of the VLTI. This is a mechanical-optical system that will compensate the optical path differences of the light beams from the individual telescopes. Such a system is necessary to ensure that the light from all telescopes arrive in the same phase at the focal point of the interferometer. Otherwise, the very sharp interferometric images cannot be obtained. ESO PR Photo 08/98 [JPEG, 102k] Schematic representation of the VLTI Delay Line, showing the retro-reflector on its moving base. For more details, please consult the technical explanation below. This highly accurate system will be developed in close co-operation with the Dutch institute TNO-TPD (Netherlands Organization for Applied Scientific Research - Institute of Applied Physics) . The most innovative feature of the Delay Line is the new control strategy, a two-stage control system, based on linear motor technology, combined with high accuracy piezo-electric control elements. This enables the system to position the so-called cat's eye reflector system with an accuracy of only a few nanometers (millionth of a millimetre (nm)) over a stroke length of 60 metres. Within radio astronomy, interferometric techniques have been applied by Dutch astronomers since many years. They will now be able to contribute with their extensive knowledge of such systems to the next generation of astronomical interferometric instruments within the present collaboration. About Fokker Space Fokker Space is the largest company in the Dutch space industry. It is based in Leiden, has 481 employees and an operating income of 220 million Netherlands Guilders in 1996. Fokker Space is mainly active in the field of solar arrays, launcher structures, thermal products, instruments and simulators. It also plays a key role in the development of robotics and is responsible as a prime contractor for the European Robotics Arm (ERA) to be used on the International Space Station. Fokker Space is well embedded in the Dutch aerospace infrastructure, thanks to close relations with the Dutch Space Agency (NIVR) , the National Aerospace Laboratory (NLR) , the Delft University of Technology and other Dutch space industries and institutes like TNO-TPD (Netherlands Organization for Applied Scientific Research - Institute of Applied Physics) . Fokker Space has also entered into strategic partnerships in Europe, Russia and North America. These facts, combined with the long lasting relation with the European Space Agency ESA and with the Dutch Government imply that Fokker Space has secured a solid base for continuation of its business far into the next millennium. Some technical details about the VLTI Delay Line The VLT Delay Line forms an essential part of the VLT Interferometer (VLTI) . It represents the current limit of high technology in this field and includes many innovative features. Some of the technical details are given below. In order to enable a useful combination of the light beams from the individual telescopes of the VLT (that is, to produce interferometric fringes at the focal point), the optical path length differences must be corrected by the Delay Line system. These differences are caused by: * the static geometric path length difference between the telescopes in a certain configuration; * the diurnal motion of the astronomical source during observation due to Earth's rotation; and * the rapid path length variations due to atmospheric disturbances and/or mechanical vibrations along the optical path length. The VLTI Delay Line system consists of a retro-reflector mounted on a moving base. The optical design of this `Cat's Eye' is of the Ritchey-Chretien type that reflects the light very effectively. For this particular application, the `Cat's Eye' is not a corner cube with 3 perpendicular mirrors as is the case in the reflectors on cars and bicycles; it is in fact a telescope with a mirror at the focus that sends a light beam back in a direction parallel to the one it came from. The moving base enables the Cat's Eye to travel along a 60 metres long rail track, thereby providing optical path difference corrections of up to 120 metres, as required for the VLT telescope configurations at Paranal. The necessary, rapid path length corrections are performed by a fine positioning loop in which a piezo crystal (mounted on the backside of the Variable Curvature Mirror M3) is used to correct the fast optical path variations as measured by a Fringe Sensing Unit (FSU). The latter provides a signal to the Delay Line system via a fast link to the Delay Line Local Control Unit. An optical datalink to the Cat's Eye on the carriage ensures the transfer of data to the Piezo controller. The carriage is driven by a Linear Induction Motor. The coils for the motor are mounted on the floor of the Delay Line Long Support Bench and the magnets are mounted on the bottom of the carriage. The metrology system (to measure the carriage position) consists of a laser-interferometer whose beam follows the same path as the light beams from the telescopes via the Cat's Eye. The main design parameters are shown here: Optical Path range above 120 m Optical Path resolution better than 20 nm Optical Path stability better than 14 nm over any 0.01 sec (in the visible spectral range) better than 50 nm over any 0.05 sec (in Near-IR spectral range) better than 225 nm over any 0.3 sec (in Thermal-IR spectral range) Absolute position repeatability 50 micron (over full length - 60 metres) 1 micron (over observation length - 3 metres) Maximum velocity: 0.5 m/sec Maximum velocity errors 1 micron/sec Maximum power dissipation 15 Watts Note: [1] This Press Release is issued jointly by ESO and Fokker Space on the occasion of the signature of the contract for the VLTI Delay System which takes place at Fokker Space in Leiden (The Netherlands) today. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Exact and Heuristic Minimization of the Average Path Length in Decision Diagrams

DTIC Science & Technology

2005-01-01

34$&%’ (*) &+#-,./&%1023 ’+/4%! 5637& 158+#&9 1 SHINOBU NAGAYAMA∗ , ALAN ...reviewers for constructive comments. REFERENCES [1] Ashar , P. and Malik, S. (1995). Fast functional simulation using branching programs, ICCAD’95, 408–412. [2

Pulse stretcher

DOEpatents

Horton, James A.

1994-01-01

Apparatus (20) for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse. The apparatus (20) uses a White cell (10) having a plurality of optical delay paths (18a-18d) of successively increasing number of passes between the field mirror (13) and the objective mirrors (11 and 12). A pulse (26) from a laser (27) travels through a multi-leg reflective path (28) between a beam splitter (21) and a totally reflective mirror (24) to the laser output (37). The laser pulse (26) is also simultaneously injected through the beam splitter (21) to the input mirrors (14a-14d) of the optical delay paths (18a-18d). The pulses from the output mirrors (16a-16d) of the optical delay paths (18a-18d) go simultaneously to the laser output (37) and to the input mirrors ( 14b-14d) of the longer optical delay paths. The beam splitter (21) is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output (37).

Can cycling safety be improved by opening all unidirectional cycle paths for cycle traffic in both directions? A theoretical examination of available literature and data.

PubMed

Methorst, Rob; Schepers, Paul; Kamminga, Jaap; Zeegers, Theo; Fishman, Elliot

2017-08-01

Many studies have found bicycle-motor vehicle crashes to be more likely on bidirectional cycle paths than on unidirectional cycle paths because drivers do not expect cyclists riding at the right side of the road. In this paper we discuss the hypothesis that opening all unidirectional cycle paths for cycle traffic in both directions prevent this lack of expectancy and accordingly improves cycling safety. A new national standard requires careful consideration because a reversal is difficult once cyclists are used to their new freedom of route choice. We therefore explored the hypothesis using available data, research, and theories. The results show that of the length of cycle paths along distributor roads in the Netherlands, 72% is bidirectional. If drivers would become used to cyclists riding at the left side of the road, this result raises the question of why bidirectional cycle paths in the Netherlands still have a poor safety record compared to unidirectional cycle paths. Moreover, our exploration suggested that bidirectional cycle paths have additional safety problems. It increases the complexity of unsignalized intersections because drivers have to scan more directions in a short period of time. Moreover, there are some indications that the likelihood of frontal crashes between cyclists increases. We reject the hypothesis that opening all unidirectional cycle paths for cycle traffic in both directions will improve cycle safety. We recommend more attention for mitigating measures given the widespread application of bidirectional cycle paths in the Netherlands. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-temperature multipass cell for infrared spectroscopy of heated gases and vapors.

PubMed

Bartlome, R; Baer, M; Sigrist, M W

2007-01-01

In absorption spectroscopy, infrared spectra of heated gases or condensed samples in the vapor phase are usually recorded with a single pass heated gas cell. This device exhibits two orders of magnitude lower sensitivity than the high-temperature multipass cell presented in this article. Our device is a novel type of compact long path absorption cell that can withstand aggressive chemicals in addition to temperatures up to 723 K. The construction of the cell and its technical features are described in detail, paying special attention to the mechanisms that compensate for thermal expansion and that allow the user to vary the optical path length under any thermal or vacuum condition. The cell may be used with a laser source or implemented within a Fourier transform infrared spectrometer. Its design is compatible with optical arrangements using astigmatic mirrors or spherical mirrors in a Herriott configuration. Here we implement a homebuilt Herriott-type cell with a total optical path length of up to 35 m. In order to demonstrate the feasibility of the cell, methane and water vapor absorption lines showing dissimilar temperature effects on line intensity were recorded with the help of a mid-infrared laser source tunable between 3 and 4 microm. Emphasis is put on lines that are too weak to be recorded with a single pass cell.

New assignments in the 2 μm transparency window of the 12CH4 Octad band system

NASA Astrophysics Data System (ADS)

Daumont, L.; Nikitin, A. V.; Thomas, X.; Régalia, L.; Von der Heyden, P.; Tyuterev, Vl. G.; Rey, M.; Boudon, V.; Wenger, Ch.; Loëte, M.; Brown, L. R.

2013-02-01

This paper reports new assignments of rovibrational transitions of 12CH4 bands in the range 4600-4887 cm-1 which is usually referred to as a part of the 2 μm methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603 m absorption path length and pressures of 1, 7 and 34 hPa for samples of natural abundance CH4 provided new measurements of 12CH4 lines. Older spectra for 13CH4 (90% purity) from JPL with 73 m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to the Octad system of 12CH4. The new spectra allowed us to assign 1014 new line positions and to measure 1095 line intensities in the cold bands of the Octad. These new line positions and intensities were added to the global fit of Hamiltonian and dipole moment parameters of the Ground State, Dyad, Pentad and Octad systems. This leads to a noticeable improvement of the theoretical description in this methane transparency window and a better global prediction of the methane spectrum.

AC signal characterization for optimization of a CMOS single-electron pump

NASA Astrophysics Data System (ADS)

Murray, Roy; Perron, Justin K.; Stewart, M. D., Jr.; Zimmerman, Neil M.

2018-02-01

Pumping single electrons at a set rate is being widely pursued as an electrical current standard. Semiconductor charge pumps have been pursued in a variety of modes, including single gate ratchet, a variety of 2-gate ratchet pumps, and 2-gate turnstiles. Whether pumping with one or two AC signals, lower error rates can result from better knowledge of the properties of the AC signal at the device. In this work, we operated a CMOS single-electron pump with a 2-gate ratchet style measurement and used the results to characterize and optimize our two AC signals. Fitting this data at various frequencies revealed both a difference in signal path length and attenuation between our two AC lines. Using this data, we corrected for the difference in signal path length and attenuation by applying an offset in both the phase and the amplitude at the signal generator. Operating the device as a turnstile while using the optimized parameters determined from the 2-gate ratchet measurement led to much flatter, more robust charge pumping plateaus. This method was useful in tuning our device up for optimal charge pumping, and may prove useful to the semiconductor quantum dot community to determine signal attenuation and path differences at the device.

Control devices and steering strategies in pathway surgery.

PubMed

Fan, Chunman; Jelínek, Filip; Dodou, Dimitra; Breedveld, Paul

2015-02-01

For pathway surgery, that is, minimally invasive procedures carried out transluminally or through instrument-created pathways, handheld maneuverable instruments are being developed. As the accompanying control interfaces of such instruments have not been optimized for intuitive manipulation, we investigated the effect of control mode (1DoF or 2DoF), and control device (joystick or handgrip) on human performance in a navigation task. The experiments were conducted using the Endo-PaC (Endoscopic-Path Controller), a simulator that emulates the shaft and handle of a maneuverable instrument, combined with custom-developed software animating pathway surgical scenarios. Participants were asked to guide a virtual instrument without collisions toward a target located at the end of a virtual curved tunnel. The performance was assessed in terms of task completion time, path length traveled by the virtual instrument, motion smoothness, collision metrics, subjective workload, and personal preference. The results indicate that 2DoF control leads to faster task completion and fewer collisions with the tunnel wall combined with a strong subjective preference compared with 1DoF control. Handgrip control appeared to be more intuitive to master than joystick control. However, the participants experienced greater physical demand and had longer path lengths with handgrip than joystick control. Copyright © 2015 Elsevier Inc. All rights reserved.

Measurement of Debye length in laser-produced plasma.

NASA Technical Reports Server (NTRS)

Ehler, W.

1973-01-01

The Debye length of an expanded plasma created by placing an evacuated chamber with an entrance slit in the path of a freely expanding laser produced plasma was measured, using the slab geometry. An independent measurement of electron density together with the observed value for the Debye length also provided a means for evaluating the plasma electron temperature. This temperature has applications in ascertaining plasma conductivity and magnetic field necessary for confinement of the laser produced plasma. Also, the temperature obtained would be useful in analyzing electron-ion recombination rates in the expanded plasma and the dynamics of the cooling process of the plasma expansion.

Ultrasonic studies of intermolecular interactions in binary mixtures of 4-methoxy benzoin with various solvents: Excess molar functions of ultrasonic parameters at different concentrations and in different solvents.

PubMed

Thanuja, B; Nithya, G; Kanagam, Charles C

2012-11-01

Density (ρ), ultrasonic velocity (U), for the binary mixtures of 4-methoxy benzoin (4MB) with ethanol, chloroform, acetonitrile, benzene, and di-oxane were measured at 298K. The solute-solvent interactions and the effect of the polarity of the solvent on the type of intermolecular interactions are discussed here. From the above data, adiabatic compressibility (β), intermolecular free length (L(f)), acoustic impedance (Z), apparent molar volume (Ø), relative association (RA) have been calculated. Other useful parameters such as excess density, excess velocity and excess adiabatic compressibility have also been calculated. These parameters were used to study the nature and extent of intermolecular interactions between component molecules in the binary mixtures. Copyright © 2012 Elsevier B.V. All rights reserved.

Mechanical behavior and failure phenomenon of an in situ-toughened silicon nitride

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Choi, Sung R.; Freedman, Marc R.; Jenkins, Michael G.

1990-01-01

The Weibull modulus, fracture toughness and crack growth resistance of an in-situ toughened, silicon nitride material used to manufacture a turbine combustor were determined from room temperature to 1371 C. The material exhibited an elongated grain structure that resulted in improved fracture toughness, nonlinear crack growth resistance, and good elevated temperature strength. However, low temperature strength was limited by grains of excessive length (30 to 100 microns). These excessively long grains were surrounded by regions rich in sintering additives.

Optical fibers for the distribution of frequency and timing references

NASA Technical Reports Server (NTRS)

Lutes, G. F.

1981-01-01

An optical fiber communications link was installed for the purpose of evaluating the applicability of optical fiber technology to the distribution of frequency and timing reference signals. It incorporated a 1.5km length of optical fiber cable containing two multimode optical fibers. The two fibers were welded together at one end of the cable to attain a path length of 3km. Preliminary measurements made on this link, including Allan variance and power spectral density of phase noise are reported.

Optoelectronic System Measures Distances to Multiple Targets

NASA Technical Reports Server (NTRS)

Liebe, Carl Christian; Abramovici, Alexander; Bartman, Randall; Chapsky, Jacob; Schmalz, John; Coste, Keith; Litty, Edward; Lam, Raymond; Jerebets, Sergei

2007-01-01

An optoelectronic metrology apparatus now at the laboratory-prototype stage of development is intended to repeatedly determine distances of as much as several hundred meters, at submillimeter accuracy, to multiple targets in rapid succession. The underlying concept of optoelectronic apparatuses that can measure distances to targets is not new; such apparatuses are commonly used in general surveying and machining. However, until now such apparatuses have been, variously, constrained to (1) a single target or (2) multiple targets with a low update rate and a requirement for some a priori knowledge of target geometry. When fully developed, the present apparatus would enable measurement of distances to more than 50 targets at an update rate greater than 10 Hz, without a requirement for a priori knowledge of target geometry. The apparatus (see figure) includes a laser ranging unit (LRU) that includes an electronic camera (photo receiver), the field of view of which contains all relevant targets. Each target, mounted at a fiducial position on an object of interest, consists of a small lens at the output end of an optical fiber that extends from the object of interest back to the LRU. For each target and its optical fiber, there is a dedicated laser that is used to illuminate the target via the optical fiber. The targets are illuminated, one at a time, with laser light that is modulated at a frequency of 10.01 MHz. The modulated laser light is emitted by the target, from where it returns to the camera (photodetector), where it is detected. Both the outgoing and incoming 10.01-MHz laser signals are mixed with a 10-MHz local-oscillator to obtain beat notes at 10 kHz, and the difference between the phases of the beat notes is measured by a phase meter. This phase difference serves as a measure of the total length of the path traveled by light going out through the optical fiber and returning to the camera (photodetector) through free space. Because the portion of the path length inside the optical fiber is not ordinarily known and can change with temperature, it is also necessary to measure the phase difference associated with this portion and subtract it from the aforementioned overall phase difference to obtain the phase difference proportional to only the free-space path length, which is the distance that one seeks to measure. Therefore, the apparatus includes a photodiode and a circulator that enable measurement of the phase difference associated with propagation from the LRU inside the fiber to the target, reflection from the fiber end, and propagation back inside the fiber to the LRU. Because this phase difference represents twice the optical path length of the fiber, this phase difference is divided in two before subtraction from the aforementioned total-path-length phase difference. Radiation-induced changes in the photodetectors in this apparatus can affect the measurements. To enable calibration for the purpose of compensation for these changes, the apparatus includes an additional target at a known short distance, located inside the camera. If the measured distance to this target changes, then the change is applied to the other targets.

On the nature of the excess heat capacity of mixing

NASA Astrophysics Data System (ADS)

Benisek, Artur; Dachs, Edgar

2011-03-01

The excess vibrational entropy (Δ S {vib/ex}) of several silicate solid solutions are found to be linearly correlated with the differences in end-member volumes (Δ V i ) and end-member bulk moduli (Δκ i ). If a substitution produces both, larger and elastically stiffer polyhedra, then the substituted ion will find itself in a strong enlarged structure. The frequency of its vibration is decreased because of the increase in bond lengths. Lowering of frequencies produces larger heat capacities, which give rise to positive excess vibrational entropies. If a substitution produces larger but elastically softer polyhedra, then increase and decrease of mean bond lengths may be similar in magnitude and their effect on the vibrational entropy tends to be compensated. The empirical relationship between Δ S {vib/ex}, Δ V i and Δκ i , as described by Δ S {vib/ex} = (Δ V i + mΔκ i ) f, was calibrated on six silicate solid solutions (analbite-sanidine, pyrope-grossular, forsterite-fayalite, analbite-anorthite, anorthite-sanidine, CaTs-diopside) yielding m = 0.0246 and f = 2.926. It allows the prediction of Δ S {vib/ex} behaviour of a solid solution based on its volume and bulk moduli end-member data.

Nitrogen transport and transformations in a coastal plain watershed: Influence of geomorphology on flow paths and residence times

USGS Publications Warehouse

Tesoriero, Anthony J.; Spruill, Timothy B.; Mew, H.E.; Farrell, Kathleen M.; Harden, Stephen L.

2005-01-01

Nitrogen transport and groundwater-surface water interactions were examined in a coastal plain watershed in the southeastern United States. Groundwater age dates, calculated using chlorofluorocarbon and tritium concentrations, along with concentrations of nitrogen species and other redox-active constituents, were used to evaluate the fate and transport of nitrate. Nitrate is stable only in recently recharged (<10 years) water found in the upper few meters of saturated thickness in the upland portion of a surficial aquifer. Groundwater with a residence time between 10 and 30 years typically has low nitrate and elevated excess N2 concentrations, indications that denitrification has reduced nitrate concentrations. Groundwater older than 30 years also has low nitrate concentrations but contains little or no excess N2, suggesting that this water did not contain elevated concentrations of nitrate along its flow path. Nitrate transport to streams varies between first- and third-order streams. Hydrologic, lithologic, and chemical data suggest that the surficial aquifer is the dominant source of flow and nitrate to a first-order stream. Iron-reducing conditions occur in groundwater samples from the bed and banks of the first-order stream, suggesting that direct groundwater discharge is denitrified prior to entering the stream. However, nitrogen from the surficial aquifer is transported directly to the stream via a tile drain that bypasses these reduced zones. In the alluvial valley of a third-order stream the erosion of a confining layer creates a much thicker unconfined alluvial aquifer with larger zones of nitrate stability. Age dating and chemical information (SiO 2, Na/K ratios) suggest that water in the alluvial aquifer is derived from short flow paths through the riparian zone and/or from adjacent streams during high-discharge periods. Copyright 2005 by the American Geophysical Union.

Cyclic fatigue resistances of several nickel-titanium glide path rotary and reciprocating instruments at body temperature.

PubMed

Yılmaz, K; Uslu, G; Gündoğar, M; Özyürek, T; Grande, N M; Plotino, G

2018-01-31

To compare the cyclic fatigue resistance of the One G, ProGlider, HyFlex EDM and R-Pilot glide path NiTi files at body temperature. Twenty One G (size 14, .03 taper), 20 ProGlider (size 16, .02 taper), 20 HyFlex EDM (size 10, .05 taper) and 20 R-Pilot (size 12.5, .04 taper) instruments were operated in rotation at 300 rpm (One G, ProGlider and HyFlex) or in reciprocation (R-Pilot) at 35 °C in artificial canals that were manufactured by reproducing the size and taper of the instrument until fracture occurred. The time to fracture was recorded in seconds using a digital chronometer, and the length of the fractured fragments was registered. Mean data were analysed statistically using the Kruskal-Wallis test and post hoc Tukey tests via SPSS 21.0 software. The statistical significance level was set at 5%. The cyclic fatigue resistance of the R-Pilot files was significantly greater than the other instruments, and the One G was significantly lower (P < 0.05). There was no difference between the HyFlex EDM and the ProGlider (P > 0.05). No significant difference (P > 0.05) was evident in the mean length of the fractured fragments of the various instruments. The cyclic fatigue resistance of the R-Pilot reciprocating glide path file was significantly greater than that of the rotary HyFlex EDM, ProGlider and One G glide path files. © 2018 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Effective use of congestion in complex networks

NASA Astrophysics Data System (ADS)

Echagüe, Juan; Cholvi, Vicent; Kowalski, Dariusz R.

2018-03-01

In this paper, we introduce a congestion-aware routing protocol that selects the paths according to the congestion of nodes in the network. The aim is twofold: on one hand, and in order to prevent the networks from collapsing, it provides a good tolerance to nodes' overloads; on the other hand, and in order to guarantee efficient communication, it also incentivize the routes to follow short paths. We analyze the performance of our proposed routing strategy by means of a series of experiments carried out by using simulations. We show that it provides a tolerance to collapse close to the optimal value. Furthermore, the average length of the paths behaves optimally up to the certain value of packet generation rate ρ and it grows in a linear fashion with the increase of ρ.

Novel Diffusivity Measurement Technique

NASA Technical Reports Server (NTRS)

Rashidnia, Nasser

2001-01-01

A common-path interferometer (CPI) system was developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. This system uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Hence, the molecular diffusion coefficient of liquids can be determined using the physical relations between changes in the optical path length and the liquid phase properties. The data obtained with this interferometer were compared with similar results from other techniques and demonstrated that the instrument is superior in measuring the diffusivity of miscible liquids while keeping the system very compact and robust. CPI can also be used for studies in interface dynamics and other diffusion-dominated-process applications.

Accuracy enhanced distance measurement system using double-sideband modulated frequency scanning interferometry

NASA Astrophysics Data System (ADS)

Chen, Xilun; Wang, Xiangchuan; Pan, Shilong

2017-03-01

An implementation of a distance measurement system using double-sideband with suppressed carrier modulation (DSB-SC) frequency scanning interferometry is proposed to reduce the variations in the optical path and improve the measurement accuracy. In this proposed system, the electro-optic DSB-SC is used to create dual-swept signals with opposite scanning directions. For each swept signal, the relative distance between the reference arm and the measuring arm is determined by the beat frequency of signals from two arms. By multiplying both beat signals, measurement errors caused by variations in the optical path can be greatly reduced. As an experimental demonstration, a vibration was introduced in the optical path length. The experimental results show that the variations can be suppressed for over 19.9 dB.

Aberration-free intraocular lenses - What does this really mean?

PubMed

Langenbucher, Achim; Schröder, Simon; Cayless, Alan; Eppig, Timo

2017-09-01

So-called aberration-free intraocular lenses (IOLs) are well established in modern cataract surgery. Usually, they are designed to perfectly refract a collimated light beam onto the focal point. We show how much aberration can be expected with such an IOL in a convergent light beam such as that found anterior to the human cornea. Additionally, the aberration in a collimated beam is estimated for an IOL that has no aberrations in the convergent beam. The convergent beam is modelled as the pencil of rays corresponding to the spherical wavefront resulting from a typical corneal power of 43m -1 . The IOLs are modelled as infinitely thin phase plates with 20m -1 optical power placed 5mm behind the cornea. Their aberrations are reported in terms of optical path length difference and longitudinal spherical aberration (LSA) of the marginal rays, as well as nominal spherical aberration (SA) calculated based on a Zernike representation of the wavefront-error at the corneal plane within a 6mm aperture. The IOL designed to have no aberrations in a collimated light beam has an optical path length difference of -1.8μm, and LSA of 0.15m -1 in the convergent beam of a typical eye. The corresponding nominal SA is 0.065μm. The IOL designed to have no aberrations in a convergent light beam has an optical path length difference of 1.8μm, and LSA of -0.15m -1 in the collimated beam. An IOL designed to have no aberrations in a collimated light beam will increase the SA of a patient's eye after implantation. Copyright © 2017. Published by Elsevier GmbH.

The relationship between hippocampal volume and static postural sway: results from the GAIT study.

PubMed

Beauchet, Olivier; Barden, John; Liu-Ambrose, Teresa; Chester, Victoria L; Szturm, Tony; Allali, Gilles

2016-02-01

The role of the hippocampus in postural control, in particular in maintaining upright stance, has not been fully examined in normal aging. This study aims to examine the association of postural sway with hippocampal volume while maintaining upright stance in healthy older individuals. Seventy healthy individuals (mean age 69.7 ± 3.4 years; 41.4 % women) were recruited in this study based on cross-sectional design. Hippocampal volume (quantified from a three-dimensional T1-weighted MRI using semi-automated software), three center of pressure (COP) motion parameters (sway area, path length of anterior-posterior (AP) and medial-lateral (ML) displacement) while maintaining upright stance (eyes open and closed), and the relative difference between open and closed eye conditions were used as outcome measures. Age, sex, body mass index, lower limb proprioception, distance vision, 15-item geriatric depression scale score, total cranial volume, and white matter abnormalities were used as covariates. The sway area decreased from open to closed eye condition but this variation was non-significant (P = 0.244), whereas path length of AP and ML displacement increased significantly (P < 0.003). Increase in sway area from open to closed eyes was associated with greater hippocampal volume (β -18.21; P = 0.044), and a trend for an association of increase in path length of AP displacement (P = 0.075 for open eyes and P = 0.071 for closed eyes) with greater hippocampal volume was reported. The hippocampus is involved in upright postural control in normal aging, such that an increase in sway area of COP motion from open to closed eyes is associated with greater hippocampal volume in healthy older adults.

Brain Network Architecture and Global Intelligence in Children with Focal Epilepsy.

PubMed

Paldino, M J; Golriz, F; Chapieski, M L; Zhang, W; Chu, Z D

2017-02-01

The biologic basis for intelligence rests to a large degree on the capacity for efficient integration of information across the cerebral network. We aimed to measure the relationship between network architecture and intelligence in the pediatric, epileptic brain. Patients were retrospectively identified with the following: 1) focal epilepsy; 2) brain MR imaging at 3T, including resting-state functional MR imaging; and 3) full-scale intelligence quotient measured by a pediatric neuropsychologist. The cerebral cortex was parcellated into approximately 700 gray matter network "nodes." The strength of a connection between 2 nodes was defined by the correlation between their blood oxygen level-dependent time-series. We calculated the following topologic properties: clustering coefficient, transitivity, modularity, path length, and global efficiency. A machine learning algorithm was used to measure the independent contribution of each metric to the intelligence quotient after adjusting for all other metrics. Thirty patients met the criteria (4-18 years of age); 20 patients required anesthesia during MR imaging. After we accounted for age and sex, clustering coefficient and path length were independently associated with full-scale intelligence quotient. Neither motion parameters nor general anesthesia was an important variable with regard to accurate intelligence quotient prediction by the machine learning algorithm. A longer history of epilepsy was associated with shorter path lengths ( P = .008), consistent with reorganization of the network on the basis of seizures. Considering only patients receiving anesthesia during machine learning did not alter the patterns of network architecture contributing to global intelligence. These findings support the physiologic relevance of imaging-based metrics of network architecture in the pathologic, developing brain. © 2017 by American Journal of Neuroradiology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Battum, LJ van; Heukelom, S

Purpose This study investigates the origin of lateral optical density (OD) variation for Gafchromic film (EBT and EBT2) scanned in transmission mode with Epson flatbed scanners (1680 Expression Pro and 10000XL). Effects investigated are: cross talk, optical path length and polarization. Methods Cross talk has been examined with triangular shaped light-transmission sheets with OD ranging from 0 to opaque. Optical path length has been studied with absorptive and reflective OD-filters (OD range 0.2 to 2.0). Dependency on light-polarization on the scanner read out has been investigated using linear polarizer sheets. All experiments have been performed at centre scanner position (normmore » point) and at several lateral scan positions, without and with (un)irradiated EBT-film. Dose values used ranged between 0.2 to 9 Gy, yielding an OD-range between 0.25 to 1.1. Results The lateral OD variation is dose dependent and increases up to 14% at most lateral position for dose up to 9 Gy. Cross talk effect contributes to 0.5% in clinical used OD ranges but equals 2% for extreme high dose gradients. Film induced optical path length will effect the lateral OD variation up to 3% at most lateral points. Light polarization is inherent present in these scanners due to multiple reflection on mirrors. In addition film induced polarization is the most important effect generating the observed lateral OD variation. Both Gafchromic film base and sensitive layer have polarizing capabilities; for the sensitive layer its influence is dose dependent. Conclusions Lateral OD variation origins from optical physics (i.e. polarization and reflection) related to scanner and film construction. Cross talk can be ignored in film dosimetry for clinical used dose values and gradients. Therefore it is recommended to determine the lateral OD variation per film type and scanner.« less

Scanning Laser Infrared Molecular Spectrometer (SLIMS)

NASA Technical Reports Server (NTRS)

Scott, David C.; Rickey, Kelly; Ksendzov, Alexander; George, Warren P.; Aljabri, Abdullah S.; Steinkraus, Joel M.

2012-01-01

This prototype innovation is a novel design that achieves very long, effective laser path lengths that are able to yield ppb (parts per billion) and sub-ppb measurements of trace gases. SLIMS can also accommodate multiple laser channels covering a wide range of wavelengths, resulting in detection of more chemicals of interest. The mechanical design of the mirror cell allows for the large effective path length within a small footprint. The same design provides a robust structure that lends itself to being immune to some of the alignment challenges that similar cells face. By taking a hollow cylinder and by cutting an elliptically or spherically curved surface into its inner wall, the basic geometry of a reflecting ring is created. If the curved, inner surface is diamond-turned and highly polished, a surface that is very highly reflective can be formed. The surface finish can be further improved by adding a thin chrome or gold film over the surface. This creates a high-quality, curved, mirrored surface. A laser beam, which can be injected from a small bore hole in the wall of the cylinder, will be able to make many low-loss bounces around the ring, creating a large optical path length. The reflecting ring operates on the same principle as the Herriott cell. The difference exists in the mirror that doesn't have to be optically aligned, and which has a relatively large, internal surface area that lends itself to either open air or evacuated spectroscopic measurements. This solid, spherical ring mirror removes the possibility of mirror misalignment caused by thermal expansion or vibrations, because there is only a single, solid reflecting surface. Benefits of the reflecting ring come into play when size constraints reduce the size of the system, especially for space missions in which mass is at a premium.

The influence of NDT-Bobath and PNF methods on the field support and total path length measure foot pressure (COP) in patients after stroke.

PubMed

Krukowska, Jolanta; Bugajski, Marcin; Sienkiewicz, Monika; Czernicki, Jan

In stroke patients, the NDT - (Bobath - Neurodevelopmental Treatment) and PNF (Proprioceptive Neuromuscular Facilitation) methods are used to achieve the main objective of rehabilitation, which aims at the restoration of maximum patient independence in the shortest possible period of time (especially the balance of the body). The aim of the study is to evaluate the effect of the NDT-Bobath and PNF methods on the field support and total path length measure foot pressure (COP) in patients after stroke. The study included 72 patients aged from 20 to 69 years after ischemic stroke with Hemiparesis. The patients were divided into 4 groups by a simple randomization. The criteria for this division were: the body side (right or left) affected by paresis and the applied rehabilitation methods. All the patients were applied the recommended kinesitherapeutic method (randomized), 35 therapy sessions, every day for a period of six weeks. Before initiation of therapy and after 6 weeks was measured the total area of the support and path length (COP (Center Of Pressure) measure foot pressure) using stabilometer platform - alpha. The results were statistically analyzed. After treatment studied traits decreased in all groups. The greatest improvement was obtained in groups with NDT-Bobath therapy. NDT-Bobath method for improving the balance of the body is a more effective method of treatment in comparison with of the PNF method. In stroke patients, the effectiveness of NDT-Bobath method does not depend on hand paresis. Copyright © 2016 Polish Neurological Society. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

How do protozoa respond to intense magnetic fields?

NASA Astrophysics Data System (ADS)

Guevorkian, Karine

2005-03-01

Most microorganisms such as Paramecium Caudatum, swim in helical paths in nature. In the absence of any external stimuli (e.g. obstacles, electric field, heat, etc.) the axes of these helical paths, which define the trajectories, are straight lines and are distributed in random directions. Our experiments reveal that these trajectories can be manipulated by applying intense DC magnetic fields of the order of several Tesla. Swimming paramecia, for example, align their trajectories with magnetic fields in excess of about 7 Tesla in fraction of a second. We will describe this phenomenon in fields up to 25 T. We will address whether this effect is an active or passive response to the magnetic torque exerted on the diamagnetically anisotropic structures in Paramecium. In addition we will present results for other species as they are obtained.

Excess Length of Stay Attributable to Clostridium difficile Infection (CDI) in the Acute Care Setting: A Multistate Model.

PubMed

Stevens, Vanessa W; Khader, Karim; Nelson, Richard E; Jones, Makoto; Rubin, Michael A; Brown, Kevin A; Evans, Martin E; Greene, Tom; Slade, Eric; Samore, Matthew H

2015-09-01

Standard estimates of the impact of Clostridium difficile infections (CDI) on inpatient lengths of stay (LOS) may overstate inpatient care costs attributable to CDI. In this study, we used multistate modeling (MSM) of CDI timing to reduce bias in estimates of excess LOS. A retrospective cohort study of all hospitalizations at any of 120 acute care facilities within the US Department of Veterans Affairs (VA) between 2005 and 2012 was conducted. We estimated the excess LOS attributable to CDI using an MSM to address time-dependent bias. Bootstrapping was used to generate 95% confidence intervals (CI). These estimates were compared to unadjusted differences in mean LOS for hospitalizations with and without CDI. During the study period, there were 3.96 million hospitalizations and 43,540 CDIs. A comparison of unadjusted means suggested an excess LOS of 14.0 days (19.4 vs 5.4 days). In contrast, the MSM estimated an attributable LOS of only 2.27 days (95% CI, 2.14-2.40). The excess LOS for mild-to-moderate CDI was 0.75 days (95% CI, 0.59-0.89), and for severe CDI, it was 4.11 days (95% CI, 3.90-4.32). Substantial variation across the Veteran Integrated Services Networks (VISN) was observed. CDI significantly contributes to LOS, but the magnitude of its estimated impact is smaller when methods are used that account for the time-varying nature of infection. The greatest impact on LOS occurred among patients with severe CDI. Significant geographic variability was observed. MSM is a useful tool for obtaining more accurate estimates of the inpatient care costs of CDI.

Path description of coordinate-space amplitudes

NASA Astrophysics Data System (ADS)

Erdoǧan, Ozan; Sterman, George

2017-06-01

We develop a coordinate version of light-cone-ordered perturbation theory, for general time-ordered products of fields, by carrying out integrals over one light-cone coordinate for each interaction vertex. The resulting expressions depend on the lengths of paths, measured in the same light-cone coordinate. Each path is associated with a denominator equal to a "light-cone deficit," analogous to the "energy deficits" of momentum-space time- or light-cone-ordered perturbation theory. In effect, the role played by intermediate states in momentum space is played by paths between external fields in coordinate space. We derive a class of identities satisfied by coordinate diagrams, from which their imaginary parts can be derived. Using scalar QED as an example, we show how the eikonal approximation arises naturally when the external points in a Green function approach the light cone, and we give applications to products of Wilson lines. Although much of our discussion is directed at massless fields in four dimensions, we extend the formalism to massive fields and dimensional regularization.

Distribution of activity at the solar active longitudes between 1979 - 2011 in the northern hemisphere

NASA Astrophysics Data System (ADS)

Gyenge, N.; Baranyi, T.; Ludmány, A.

The solar active longitudes were studied in the northern hemisphere in cycles 22 and 23 by using data of DPD sunspot catalogue. The active longitudes are not fixed in the Carrington system, they have a well recognizable migration path between the descending phase of cycle 21 (from about 1984) and ascending phase of cycle 23 (until about 1996), out of this interval the migration path is ambiguous. The longitudinal distribution on both sides of the path has been computed and averaged for the length of the path. The so-called flip-flop phenomenon, when the activity temporarily gets to the opposite longitude, can also be recognized. The widths of the active domains are fairly narrow in the increasing and decaying phases of cycle 22, their half widths are about 20°-30° for both the main and secondary active belts but it is more flat and stretched around the maximum with a half width of about 60°.

Optimal Paths in Gliding Flight

NASA Astrophysics Data System (ADS)

Wolek, Artur

Underwater gliders are robust and long endurance ocean sampling platforms that are increasingly being deployed in coastal regions. This new environment is characterized by shallow waters and significant currents that can challenge the mobility of these efficient (but traditionally slow moving) vehicles. This dissertation aims to improve the performance of shallow water underwater gliders through path planning. The path planning problem is formulated for a dynamic particle (or "kinematic car") model. The objective is to identify the path which satisfies specified boundary conditions and minimizes a particular cost. Several cost functions are considered. The problem is addressed using optimal control theory. The length scales of interest for path planning are within a few turn radii. First, an approach is developed for planning minimum-time paths, for a fixed speed glider, that are sub-optimal but are guaranteed to be feasible in the presence of unknown time-varying currents. Next the minimum-time problem for a glider with speed controls, that may vary between the stall speed and the maximum speed, is solved. Last, optimal paths that minimize change in depth (equivalently, maximize range) are investigated. Recognizing that path planning alone cannot overcome all of the challenges associated with significant currents and shallow waters, the design of a novel underwater glider with improved capabilities is explored. A glider with a pneumatic buoyancy engine (allowing large, rapid buoyancy changes) and a cylindrical moving mass mechanism (generating large pitch and roll moments) is designed, manufactured, and tested to demonstrate potential improvements in speed and maneuverability.

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

NASA Technical Reports Server (NTRS)

Davis, J. L.; Herring, T. A.; Shapiro, I. I.; Rogers, A. E. E.; Elgered, G.

1985-01-01

Analysis of very long baseline interferometry data indicates that systematic errors in prior estimates of baseline length, of order 5 cm for approximately 8000-km baselines, were due primarily to mismodeling of the electrical path length of the troposphere and mesosphere ('atmospheric delay'). Here observational evidence for the existence of such errors in the previously used models for the atmospheric delay is discussed, and a new 'mapping' function for the elevation angle dependence of this delay is developed. The delay predicted by this new mapping function differs from ray trace results by less than approximately 5 mm, at all elevations down to 5 deg elevation, and introduces errors into the estimates of baseline length of less than about 1 cm, for the multistation intercontinental experiment analyzed here.

Spectroscopic method for determination of the absorption coefficient in brain tissue

NASA Astrophysics Data System (ADS)

Johansson, Johannes D.

2010-09-01

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, μa. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(μa)+d ln(Is)ln(μa), 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.

A critical transition in leaf evolution facilitated the Cretaceous angiosperm revolution.

PubMed

de Boer, Hugo Jan; Eppinga, Maarten B; Wassen, Martin J; Dekker, Stefan C

2012-01-01

The revolutionary rise of broad-leaved (flowering) angiosperm plant species during the Cretaceous initiated a global ecological transformation towards modern biodiversity. Still, the mechanisms involved in this angiosperm radiation remain enigmatic. Here we show that the period of rapid angiosperm evolution initiated after the leaf interior (post venous) transport path length for water was reduced beyond the leaf interior transport path length for CO2 at a critical leaf vein density of 2.5-5 mm mm(-2). Data and our modelling approaches indicate that surpassing this critical vein density was a pivotal moment in leaf evolution that enabled evolving angiosperms to profit from developing leaves with more and smaller stomata in terms of higher carbon returns from equal water loss. Surpassing the critical vein density may therefore have facilitated evolving angiosperms to develop leaves with higher gas exchange capacities required to adapt to the Cretaceous CO2 decline and outcompete previously dominant coniferous species in the upper canopy.

Theoretical and experimental investigation of near-infrared light propagation in a model of the adult head.

PubMed

Okada, E; Firbank, M; Schweiger, M; Arridge, S R; Cope, M; Delpy, D T

1997-01-01

Near-infrared light propagation in various models of the adult head is analyzed by both time-of-flight measurements and mathematical prediction. The models consist of three- or four-layered slabs, the latter incorporating a clear cerebrospinal fluid (CSF) layer. The most sophisticated model also incorporates slots that imitate sulci on the brain surface. For each model, the experimentally measured mean optical path length as a function of source-detector spacing agrees well with predictions from either a Monte Carlo model or a finite-element method based on diffusion theory or a hybrid radiosity-diffusion theory. Light propagation in the adult head is shown to be highly affected by the presence of the clear CSF layer, and both the optical path length and the spatial sensitivity profile of the models with a CSF layer are quite different from those without the CSF layer. However, the geometry of the sulci and the boundary between the gray and the white matter have little effect on the detected light distribution.

Collapse of Corroded Pipelines under Combined Tension and External Pressure

PubMed Central

Ye, Hao; Yan, Sunting; Jin, Zhijiang

2016-01-01

In this work, collapse of corroded pipeline under combined external pressure and tension is investigated through numerical method. Axially uniform corrosion with symmetric imperfections is firstly considered. After verifying with existing experimental results, the finite element model is used to study the effect of tension on collapse pressure. An extensive parametric study is carried out using Python script and FORTRAN subroutine to investigate the influence of geometric parameters on the collapse behavior under combined loads. The results are used to develop an empirical equation for estimating the collapse pressure under tension. In addition, the effects of loading path, initial imperfection length, yielding anisotropy and corrosion defect length on the collapse behavior are also investigated. It is found that tension has a significant influence on collapse pressure of corroded pipelines. Loading path and anisotropic yielding are also important factors affecting the collapse behavior. For pipelines with relatively long corrosion defect, axially uniform corrosion models could be used to estimate the collapse pressure. PMID:27111544

Geometrical-optics approximation of forward scattering by gradient-index spheres.

PubMed

Li, Xiangzhen; Han, Xiang'e; Li, Renxian; Jiang, Huifen

2007-08-01

By means of geometrical optics we present an approximation method for acceleration of the computation of the scattering intensity distribution within a forward angular range (0-60 degrees ) for gradient-index spheres illuminated by a plane wave. The incident angle of reflected light is determined by the scattering angle, thus improving the approximation accuracy. The scattering angle and the optical path length are numerically integrated by a general-purpose integrator. With some special index models, the scattering angle and the optical path length can be expressed by a unique function and the calculation is faster. This method is proved effective for transparent particles with size parameters greater than 50. It fails to give good approximation results at scattering angles whose refractive rays are in the backward direction. For different index models, the geometrical-optics approximation is effective only for forward angles, typically those less than 60 degrees or when the refractive-index difference of a particle is less than a certain value.

Essentially Entropic Lattice Boltzmann Model

NASA Astrophysics Data System (ADS)

Atif, Mohammad; Kolluru, Praveen Kumar; Thantanapally, Chakradhar; Ansumali, Santosh

2017-12-01

The entropic lattice Boltzmann model (ELBM), a discrete space-time kinetic theory for hydrodynamics, ensures nonlinear stability via the discrete time version of the second law of thermodynamics (the H theorem). Compliance with the H theorem is numerically enforced in this methodology and involves a search for the maximal discrete path length corresponding to the zero dissipation state by iteratively solving a nonlinear equation. We demonstrate that an exact solution for the path length can be obtained by assuming a natural criterion of negative entropy change, thereby reducing the problem to solving an inequality. This inequality is solved by creating a new framework for construction of Padé approximants via quadrature on appropriate convex function. This exact solution also resolves the issue of indeterminacy in case of nonexistence of the entropic involution step. Since our formulation is devoid of complex mathematical library functions, the computational cost is drastically reduced. To illustrate this, we have simulated a model setup of flow over the NACA-0012 airfoil at a Reynolds number of 2.88 ×106.

Apparatus and method for performing two-frequency interferometry

DOEpatents

Johnston, Roger G.

1990-01-01

The present apparatus includes a two-frequency, Zeeman-effect laser and matched, doubly refracting crystals in the construction of an accurate interferometer. Unlike other interferometric devices, the subject invention exhibits excellent phase stability owing to the use of single piece means for producing parallel interferometer arms, making the interferometer relatively insensitive to thermal and mechanical instabilities. Interferometers respond to differences in optical path length between their two arms. Unlike many interferometric techniques, which require the measurement of the location of interference fringes in a brightly illuminated background, the present invention permits the determination of the optical path length difference by measuring the phase of an electronic sine wave. The present apparatus is demonstrated as a differential thermooptic spectrometer for measuring differential optical absorption simply and accurately which is but one of many applications therefor. The relative intensities of the heating beams along each arm of the interferometer can be easily adjusted by observing a zero phase difference with identical samples when this condition is obtained.

Photo ion spectrometer

DOEpatents

Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

1989-01-01

A method and apparatus for extracting for quantitative analysis ions of selected atomic components of a sample. A lens system is configured to provide a slowly diminishing field region for a volume containing the selected atomic components, enabling accurate energy analysis of ions generated in the slowly diminishing field region. The lens system also enables focusing on a sample of a charged particle beam, such as an ion beam, along a path length perpendicular to the sample and extraction of the charged particles along a path length also perpendicular to the sample. Improvement of signal to noise ratio is achieved by laser excitation of ions to selected autoionization states before carrying out quantitative analysis. Accurate energy analysis of energetic charged particles is assured by using a preselected resistive thick film configuration disposed on an insulator substrate for generating predetermined electric field boundary conditions to achieve for analysis the required electric field potential. The spectrometer also is applicable in the fields of SIMS, ISS and electron spectroscopy.