3D highly oriented nanoparticulate and microparticulate array ofmetal oxide materials

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

Vayssieres, Lionel; Guo, Jinghua; Nordgren, Joseph

2006-09-15

Advanced nano and micro particulate thin films of 3d transition and post-transition metal oxides consisting of nanorods and microrods with parallel and perpendicular orientation with respect to the substrate normal, have been successfully grown onto various substrates by heteronucleation, without template and/or surfactant, from the aqueous condensation of solution of metal salts or metal complexes (aqueous chemical growth). Three-dimensional arrays of iron oxide nanorods and zinc oxide nanorods with parallel and perpendicular orientation are presented as well as the oxygen K-edge polarization dependent x-ray absorption spectroscopy (XAS) study of anisotropic perpendicularly oriented microrod array of ZnO performed at synchrotron radiationmore » source facility.« less

Seismic anisotropy of northeastern Algeria from shear-wave splitting analysis

NASA Astrophysics Data System (ADS)

Radi, Zohir; Yelles-Chaouche, Abdelkrim; Bokelmann, Götz

2015-11-01

There are few studies of internal deformation under northern Africa; here we present such a study. We analyze teleseismic shear-wave splitting for northeast Algeria, to improve our knowledge of lithospheric and asthenospheric deformation mechanisms in this region. We study waveform data generated by tens of teleseismic events recorded at five recently installed broadband (BB) stations in Algeria. These stations cover an area 2° across, extending from the Tellian geological units in the North to the Saharan Atlas units in the South. Analysis of SKS-wave splitting results insignificant spatial variations in fast polarization orientation, over a scale length of at most 100 km. The seismic anisotropy shows three clear spatial patterns. A general ENE-WSW orientation is observed under the stations in the north. This polarization orientation follows the direction of the Tell Atlas mountain chain, which is perpendicular to the convergence direction between Africa and Eurasia. Delay times vary significantly across the region, between 0.6 and 2.0 s. At several stations there is an indication of a WNW-ESE polarization orientation, which is apparently related to a later geodynamic evolutionary phase in this region. A third pattern of seismic anisotropy emerges in the South, with an orientation of roughly N-S. We discuss these observations in light of geodynamic models and present-day geodetic motion.

Experimental and modelling study of the effect of airflow orientation with respect to strip electrode on ozone production of surface dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Mikeš, J.; Pekárek, S.; Soukup, I.

2016-11-01

This study examines the effect of airflow orientation with respect to the strip active electrode on concentration of ozone and nitrogen dioxide produced in a planar generator based on the surface dielectric barrier discharge. The orientation of the airflow was tested in parallel and perpendicular with respect to the strips. It was found that in the investigated range of average discharge power, the ozone concentration increases approximately by 25% when airflow was oriented in parallel with respect to the strips in comparison with perpendicular orientation of the airflow. Similarly the increase of nitrogen dioxide concentration was observed for parallel orientation of the airflow with respect to the strips in comparison with the perpendicular orientation of the airflow. Within the range of wavelengths from 250 to 1100 nm, the changes of intensities of spectral lines associated with airflow orientation have been observed. A 3D numerical model describing ion trajectories and airflow patterns have also been developed.

Ripple formation on atomically flat cleaved Si surface with roughness of 0.038 nm rms by low-energy Ar{sup 1+} ion bombardment

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

Pahlovy, Shahjada A.; Mahmud, S. F.; Yanagimoto, K.

The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar{sup +} ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar{sup +} ion beam at ion-incidence angles of 0 deg., 60 deg., 70 deg., and 80 deg. The results confirm the successful ripple formation at ion-incidence angles of 60 deg. - 80 deg. and that the wavelength of the ripples increases with the increase ofmore » the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60 deg., where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent {alpha}, and compared the evolution of scaling regimes with Cuerno's one-dimensional simulation results.« less

Microcrack closure in rocks under stress - Direct observation

NASA Technical Reports Server (NTRS)

Batzle, M. L.; Simmons, G.; Siegfried, R. W.

1980-01-01

Direct observations of the closure of microcracks in rocks under increasing stress are reported. Uniaxial stresses up to 300 bars were applied to untreated and previously heated samples of Westerly granite and Frederick diabase by a small hydraulic press which fit entirely within a scanning electron microscope. Crack closure characteristics are found to depend on crack orientation, with cracks perpendicular to the applied stress closing and those parallel tending to open, as well as crack aspect ratio, crack intersection properties, stress concentrations and surface roughness. Uniaxial and hydrostatic stress measurements are found to be strongly dependent on fracture content as observed by SEM, and the observed hysteresis in strain measurements in the first stress cycles is also related to microscopic processes

Tidal disruption of inclined or eccentric binaries by massive black holes

NASA Astrophysics Data System (ADS)

Brown, Harriet; Kobayashi, Shiho; Rossi, Elena M.; Sari, Re'em

2018-07-01

Binary stars that are on close orbits around massive black holes (MBHs) such as Sgr A* in the centre of the Milky Way are liable to undergo tidal disruption and eject a hypervelocity star. We study the interaction between such an MBH and circular binaries for general binary orientations and penetration depths (i.e. binaries penetrate into the tidal radius around the BH). We show that for very deep penetrators, almost all binaries are disrupted when the binary rotation axis is roughly oriented towards the BH or it is in the opposite direction. The surviving chance becomes significant when the angle between the binary rotation axis and the BH direction is between 0.15π and 0.85π. The surviving chance is as high as ˜20 per cent when the binary rotation axis is perpendicular to the BH direction. However, for shallow penetrators, the highest disruption chance is found in such a perpendicular case, especially in the prograde case. This is because the dynamics of shallow penetrators is more sensitive to the relative orientation of the binary and orbital angular momenta. We provide numerical fits to the disruption probability and energy gain at the BH encounter as a function of the penetration depth. The latter can be simply rescaled in terms of binary masses, their initial separation, and the binary-to-BH mass ratio to evaluate the ejection velocity of a binary members in various systems. We also investigate the disruption of coplanar, eccentric binaries by an MBH. It is shown that for highly eccentric binaries retrograde orbits have a significantly increased disruption probability and ejection velocities compared to the circular binaries.

Tidal Disruption of Inclined or Eccentric Binaries by Massive Black Holes

NASA Astrophysics Data System (ADS)

Brown, Harriet; Kobayashi, Shiho; Rossi, Elena M.; Sari, Re'em

2018-04-01

Binary stars that are on close orbits around massive black holes (MBH) such as Sgr A* in the centre of the Milky Way are liable to undergo tidal disruption and eject a hypervelocity star. We study the interaction between such a MBH and circular binaries for general binary orientations and penetration depths (i.e. binaries penetrate into the tidal radius around the BH). We show that for very deep penetrators, almost all binaries are disrupted when the binary rotation axis is roughly oriented toward the BH or it is in the opposite direction. The surviving chance becomes significant when the angle between the binary rotation axis and the BH direction is between 0.15π and 0.85π. The surviving chance is as high as ˜20% when the binary rotation axis is perpendicular to the BH direction. However, for shallow penetrators, the highest disruption chance is found in such a perpendicular case, especially in the prograde case. This is because the dynamics of shallow penetrators is more sensitive to the relative orientation of the binary and orbital angular momenta. We provide numerical fits to the disruption probability and energy gain at the the BH encounter as a function of the penetration depth. The latter can be simply rescaled in terms of binary masses, their initial separation and the binary-to-BH mass ratio to evaluate the ejection velocity of a binary members in various systems. We also investigate the disruption of coplanar, eccentric binaries by a MBH. It is shown that for highly eccentric binaries retrograde orbits have a significantly increased disruption probability and ejection velocities compared to the circular binaries.

Correlation of bond strength with surface roughness using a new roughness measurement technique.

PubMed

Winkler, M M; Moore, B K

1994-07-01

The correlation between shear bond strength and surface roughness was investigated using new surface measurement methods. Bonding agents and associated resin composites were applied to set amalgam after mechanically roughening its surface. Surface treatments were noe (as set against glass), 80 grit, and 600 grit abrasive paper. Surface roughness (R(a) as measured parallel and perpendicular (+) to the direction of the polishing scratches and true profile length were measured. A knife-edge was applied (rate = 2.54 mm/min) at the bonding agent/amalgam interface of each sample until failure. Coefficients of determination for mean bond strength vs either roughness (R(a), of profile length were significantly higher for measurements in parallel directions than for those measurements in (+) directions. The shear bond strength to set amalgam for a PENTA-containing adhesives system (L.D. Caulk Division) was not significantly different from that of a PENTA-free adhesive (3M Dental Products Division), even though PENTA has been reported to increase bond strength to nonprecious metals. The shear bond strength of resin composite to amalgam is correlated to surface roughness when it is measured parallel to the polishing scratches. This correlation is significantly lower when surface roughness is measured in the typical manner, perpendicular to the polishing scratches.

Plagioclase-dominated Seismic Anisotropy in the Basin and Range Lower Crust

NASA Astrophysics Data System (ADS)

Bernard, R. E.; Behr, W. M.

2017-12-01

Observations of seismic anisotropy have the ability to provide important information on deformation and structures within the lithosphere. While the mechanisms controlling seismic anisotropy in the upper mantle are fairly well understood (i.e., olivine "lattice preferred orientation" or LPO), less is known about the minerals and structures controlling regional lower crustal anisotropy. We use lower crustal xenoliths from young cinder cones in the eastern Mojave/western Basin and Range to investigate mineral LPOs and their effect on seismic anisotropy. Lower crustal gabbros were collected from two areas roughly 80 km apart — the Cima and Deadman Lake Volcanic Fields. Lower crustal fabrics measured using EBSD are dominated by LPOs in plagioclase associated with both plastic deformation and magmatic flow. In all fabric types, plagioclase LPOs produce seismic fast axes oriented perpendicular to the foliation plane. This is in contrast to mantle peridotite xenoliths from the same locations, which preserve olivine LPOs with fast axes aligned parallel to the foliation plane. The orthogonal orientations of mantle and lower crustal fast axes relative to foliation implies that even where fabric development in both layers is coeval and kinematically compatible, their measured anisotropies can be perpendicular to each other, therefore appearing anti-correlated when measured seismically. Furthermore, our observation of plagioclase-dominated LPO and negligible concentrations of mica is at odds with the common assumption that lower crustal anisotropy is dominated by micaceous minerals, whose slow axes reliably align parallel to lineation or flow. In contrast, our data show that for plagioclase, fast axes align perpendicular to flow and the slow axes are variably aligned within the foliation plane. Therefore, for a crustal section dominated by plagioclase LPO with assumed horizontal foliation, there would be a vertical rather than a horizontal axis of symmetry, resulting in a lack of azimuthal anisotropy and minimal shear wave splitting for vertically propagating waves. Crustal seismic studies in this type of setting may only be able to identify crustal flow planes, but not flow directions. These findings may be generally applicable to regions of significant mafic volcanism and lower crustal magmatic underplating.

Fibre Optic Connections And Method For Using Same

DOEpatents

Chan, Benson; Cohen, Mitchell S.; Fortier, Paul F.; Freitag, Ladd W.; Hall, Richard R.; Johnson, Glen W.; Lin, How Tzu; Sherman, John H.

2004-03-30

A package is described that couples a twelve channel wide fiber optic cable to a twelve channel Vertical Cavity Surface Emitting Laser (VCSEL) transmitter and a multiple channel Perpendicularly Aligned Integrated Die (PAID) receiver. The package allows for reduction in the height of the assembly package by vertically orienting certain dies parallel to the fiber optic cable and horizontally orienting certain other dies. The assembly allows the vertically oriented optoelectronic dies to be perpendicularly attached to the horizontally oriented laminate via a flexible circuit.

Subgap in the Surface Bound States Spectrum of Superfluid (3) 3 He-B with Rough Surface

NASA Astrophysics Data System (ADS)

Nagato, Y.; Higashitani, S.; Nagai, K.

2018-03-01

The subgap structure in the surface bound states spectrum of superfluid ^3He-B with rough surface is discussed. The subgap is formed by the level repulsion between the surface bound state and the continuum states in the course of multiple scattering by the surface roughness. We show that the level repulsion is originated from the nature of the wave function of the surface bound state that is now recognized as Majorana fermion. We study the superfluid ^3He-B with a rough surface and in a magnetic field perpendicular to the surface using the quasi-classical Green function together with a random S-matrix model. We calculate the self-consistent order parameters, the spin polarization density and the surface density of states. It is shown that the subgap is found also in a magnetic field perpendicular to the surface. The magnetic field dependence of the transverse acoustic impedance is also discussed.

Spontaneous adsorption on a hydrophobic surface governed by hydrogen bonding.

PubMed

Dang, Fuquan; Hasegawa, Takeshi; Biju, Vasudevanpillai; Ishikawa, Mitsuru; Kaji, Noritada; Yasui, Takao; Baba, Yoshinobu

2009-08-18

Spontaneous adsorption from solution onto solid surface is a common phenomenon in nature, but the force that governs adsorption is still a matter of considerable debate. (1, 2) We found that surfactants and cellulose adsorb from solution onto a poly(methyl methacrylate) (PMMA) surface in an ordered and cooperative way governed by hydrogen bonding. The glucose rings of n-dodecyl-beta-D-maltoside (DDM) and hydroxyethylcellulose (HEC) stand perpendicular to the surface, H-bond to the surface COOMe groups with their C=O and Me-O bonds parallel to the surface, and form a tight monolayer. The non-H-bonded COOMe groups orient their C=O bonds perpendicular to the surface. In contrast, the glucose rings of hydrophobically modified hydroxyethylcellulose (HMHEC) lie flat with the side chains perpendicular to the surface and H-bond to the perpendicular-oriented C=O groups. The non-H-bonded COOMe groups orient their C=O bonds parallel but Me-O bonds near-perpendicular to the surface for stabilizing HMHEC. The current work provides a detailed picture of how surface-active molecules interact with a solid surface and self-assemble into greatly different architectures.

Influence of topographically patterned angled guidelines on directed self-assembly of block copolymers

NASA Astrophysics Data System (ADS)

Rebello, Nathan; Sethuraman, Vaidyanathan; Blachut, Gregory; Ellison, Christopher J.; Willson, C. Grant; Ganesan, Venkat

2017-11-01

Single chain in mean-field Monte Carlo simulations were employed to study the self-assembly of block copolymers (BCP) in thin films that use trapezoidal guidelines to direct the orientation and alignment of lamellar patterns. The present study explored the influence of sidewall interactions and geometry of the trapezoidal guidelines on the self-assembly of perpendicularly oriented lamellar morphologies. When both the sidewall and the top surface exhibit preferential interactions to the same block of the BCP, trapezoidal guidelines with intermediate taper angles were found to result in less defective perpendicularly orientated morphologies. Similarly, when the sidewall and top surface are preferential to distinct blocks of the BCP, intermediate tapering angles were found to be optimal in promoting defect free structures. Such results are rationalized based on the energetics arising in the formation of perpendicularly oriented lamella on patterned substrates.

ALMA Dust Polarization Observations of Two Young Edge-on Protostellar Disks

NASA Astrophysics Data System (ADS)

Lee, Chin-Fei; Li, Zhi-Yun; Ching, Tao-Chung; Lai, Shih-Ping; Yang, Haifeng

2018-02-01

Polarized emission is detected in two young nearly edge-on protostellar disks in 343 GHz continuum at ∼50 au (∼0.″12) resolution with Atacama Large Millimeter/submillimeter Array. One disk is in HH 212 (Class 0) and the other in the HH 111 (early Class I) protostellar system. The polarization fraction is ∼1%. The disk in HH 212 has a radius of ∼60 au. The emission is mainly detected from the nearside of the disk. The polarization orientations are almost perpendicular to the disk major axis, consistent with either self-scattering or emission by grains aligned with a poloidal field around the outer edge of the disk because of the optical depth effect and temperature gradient; the presence of a poloidal field would facilitate the launching of a disk wind, for which there is already tentative evidence in the same source. The disk of HH 111 VLA 1 has a larger radius of ∼220 au and is thus more resolved. The polarization orientations are almost perpendicular to the disk major axis in the nearside, but more along the major axis in the farside, forming roughly half of an elliptical pattern there. It appears that toroidal and poloidal magnetic field may explain the polarization on the near and far sides of the disk, respectively. However, it is also possible that the polarization is due to self-scattering. In addition, alignment of dust grains by radiation flux may play a role in the farside. Our observations reveal a diversity of disk polarization patterns that should be taken into account in future modeling efforts.

Thermal conductivity anisotropy of metasedimentary and igneous rocks

NASA Astrophysics Data System (ADS)

Davis, Michael G.; Chapman, David S.; van Wagoner, Thomas M.; Armstrong, Phillip A.

2007-05-01

Thermal conductivity anisotropy was determined for three sets of metasedimentary and igneous rocks from central Utah, USA. Most conductivity measurements were made in transient mode with a half-space, line source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding. One orientation of the probe yields thermal conductivity parallel to bedding (kpar) directly, the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity (kperp) is calculated. Some direct measurements of kpar and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady state mode. Anisotropy is defined as kpar/kperp. Precambrian argillites from Big Cottonwood Canyon have anisotropy values from 0.8 to 2.1 with corresponding conductivity perpendicular to bedding of 2.0 to 6.2 W m-1 K-1. Anisotropy values for Price Canyon sedimentary samples are less than 1.2 with a mean of 1.04 although thermal conductivity perpendicular to bedding for the samples varied from 1.3 to 5.0 W m-1 K-1. The granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2.2 to 3.2 W m-1 K-1 and a mean of 2.68 W m-1 K-1. The results confirm the observation by Deming [1994] that anisotropy is negligible for rocks having kperp greater than 4.0 W m-1 K-1 and generally increases for low conductivity metamorphic and clay-rich rocks. There is little evidence, however, for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for low thermal conductivity rocks.

A Randomized Double-Blinded Trial on the Effects of Ultrasound Transducer Orientation on Teaching and Learning Ultrasound-Guided Regional Anesthesia.

PubMed

Lam, Nicholas C K; Baker, Elizabeth B; Fishburn, Steven J; Hammer, Angie R; Petersen, Timothy R; Mariano, Edward R

2016-07-01

Learning ultrasound-guided regional anesthesia skills, especially needle/ beam alignment, can be especially difficulty for trainees, who can often become frustrated. We hypothesized that teaching novices to orient the transducer and needle perpendicular to their shoulders will improve performance on a standardized task, compared to holding the transducer and needle parallel to the shoulders. This study compared the effects of transducer orientation on trainees' ability to complete a standardized ultrasound-guided nerve block simulation. The time to task completion and percentage of the attempt time without adequate needle visualization were measured. Participants were right-handed healthy adults with no previous ultrasound experience and were randomly assigned to training in either transducer and needle alignment in a coronal plane, parallel to the shoulders (parallel group) or transducer and needle alignment in a sagittal plane, perpendicular to the shoulders (perpendicular group). Participants used ultrasound to direct a needle to 3 targets in a standardized gelatin phantom and repeated this task 3 times. Their efforts were timed and evaluated by an assessor, who was blinded to group assignment. Data were analyzed on 28 participants. The perpendicular group was able to complete the task more quickly (P < .001) and with a smaller proportion of time lost to inadequate needle visualization (P < .001). Ultrasound-guided regional anesthesia trainees complete a standardized task more quickly and efficiently when instructed to hold the transducer and needle in an orientation perpendicular to their shoulders.

Surface engineering with functional random copolymers for nanolithographic applications

NASA Astrophysics Data System (ADS)

Sparnacci, Katia; Antonioli, Diego; Gianotti, Valentina; Lupi, Federico Ferrarese; Giammaria, Tommaso Jacopo; Seguini, Gabriele; Perego, Michele; Laus, Michele

2016-05-01

Hydroxyl-terminated P(S-r-MMA) random copolymers with molecular weight ranging from 1.7 to 69 kg/mol and a styrene unit fraction of 61% were grafted onto a silicon oxide surface and subsequently used to study the orientation of domains with respect to the substrate, in cylinder-forming PS-b-PMMA block copolymer thin films. When the thickness (H) of the grafted layer is greater than 5-6 nm, a perpendicular orientation is always observed because of the efficient decoupling of the BCP film from the polar SiO2 surface. Conversely, if H is less than 5 nm, the critical thickness of the grafted layer, which allows the neutralization of the substrate and promotion of the perpendicular orientation of the nanodomains in the BCP film, is found to depend on the Mn of the RCP. In particular, when Mn = 1700, a 2.0 nm thick grafted layer is sufficient to promote the perpendicular orientation of the PMMA cylinders in the PS-b-PMMA BCP film.

Micropore extrusion-induced alignment transition from perpendicular to parallel of cylindrical domains in block copolymers.

PubMed

Qu, Ting; Zhao, Yongbin; Li, Zongbo; Wang, Pingping; Cao, Shubo; Xu, Yawei; Li, Yayuan; Chen, Aihua

2016-02-14

The orientation transition from perpendicular to parallel alignment of PEO cylindrical domains of PEO-b-PMA(Az) films has been demonstrated by extruding the block copolymer (BCP) solutions through a micropore of a plastic gastight syringe. The parallelized orientation of PEO domains induced by this micropore extrusion can be recovered to perpendicular alignment via ultrasonication of the extruded BCP solutions and subsequent annealing. A plausible mechanism is proposed in this study. The BCP films can be used as templates to prepare nanowire arrays with controlled layers, which has enormous potential application in the field of integrated circuits.

Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

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

Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impededmore » hydrogen diffusion across the banded pearlite.« less

Effects of microstructure banding on hydrogen assisted fatigue crack growth in X65 pipeline steels

DOE PAGES

Ronevich, Joseph A.; Somerday, Brian P.; San Marchi, Chris W.

2015-09-10

Banded ferrite-pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded pearlite. The ferrite-pearlite microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded pearlite compared to cracks oriented parallel to the bands. Thus the reduction of hydrogen assisted fatigue crack growth across the banded pearlite is attributed to a combination of crack-tip branching and impededmore » hydrogen diffusion across the banded pearlite.« less

Phosphorene-directed self-assembly of asymmetric PS-b-PMMA block copolymer for perpendicularly-oriented sub-10 nm PS nanopore arrays

NASA Astrophysics Data System (ADS)

Zhang, Ziming; Zheng, Lu; Khurram, Muhammad; Yan, Qingfeng

2017-10-01

Few-layer black phosphorus, also known as phosphorene, is a new two-dimensional material which is of enormous interest for applications, mainly in electronics and optoelectronics. Herein, we for the first time employ phosphorene for directing the self-assembly of asymmetric polystyrene-block-polymethylmethacrylate (PS-b-PMMA) block copolymer (BCP) thin film to form the perpendicular orientation of sub-10 nm PS nanopore arrays in a hexagonal fashion normal to the interface. We experimentally demonstrate that none of the PS and PMMA blocks exhibit preferential affinity to the phosphorene-modified surface. Furthermore, the perpendicularly-oriented PS nanostructures almost stay unchanged with the variation of number of layers of few-layer phosphorene nanoflakes between 15-30 layers. Differing from the neutral polymer brushes which are widely used for chemical modification of the silicon substrate, phosphorene provides a novel physical way to control the interfacial interactions between the asymmetric PS-b-PMMA BCP thin film and the silicon substrate. Based on our results, it is possible to build a new scheme for producing sub-10 nm PS nanopore arrays oriented perpendicularly to the few-layer phosphorene nanoflakes. Furthermore, the nanostructural microdomains could serve as a promising nanolithography template for surface patterning of phosphorene nanoflakes.

Evaluating quantitative 3-D image analysis as a design tool for low enriched uranium fuel compacts for the transient reactor test facility: A preliminary study

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

Kane, J. J.; van Rooyen, I. J.; Craft, A. E.

In this study, 3-D image analysis when combined with a non-destructive examination technique such as X-ray computed tomography (CT) provides a highly quantitative tool for the investigation of a material’s structure. In this investigation 3-D image analysis and X-ray CT were combined to analyze the microstructure of a preliminary subsized fuel compact for the Transient Reactor Test Facility’s low enriched uranium conversion program to assess the feasibility of the combined techniques for use in the optimization of the fuel compact fabrication process. The quantitative image analysis focused on determining the size and spatial distribution of the surrogate fuel particles andmore » the size, shape, and orientation of voids within the compact. Additionally, the maximum effect of microstructural features on heat transfer through the carbonaceous matrix of the preliminary compact was estimated. The surrogate fuel particles occupied 0.8% of the compact by volume with a log-normal distribution of particle sizes with a mean diameter of 39 μm and a standard deviation of 16 μm. Roughly 39% of the particles had a diameter greater than the specified maximum particle size of 44 μm suggesting that the particles agglomerate during fabrication. The local volume fraction of particles also varies significantly within the compact although uniformities appear to be evenly dispersed throughout the analysed volume. The voids produced during fabrication were on average plate-like in nature with their major axis oriented perpendicular to the compaction direction of the compact. Finally, the microstructure, mainly the large preferentially oriented voids, may cause a small degree of anisotropy in the thermal diffusivity within the compact. α∥/α⊥, the ratio of thermal diffusivities parallel to and perpendicular to the compaction direction are expected to be no less than 0.95 with an upper bound of 1.« less

Evaluating quantitative 3-D image analysis as a design tool for low enriched uranium fuel compacts for the transient reactor test facility: A preliminary study

DOE PAGES

Kane, J. J.; van Rooyen, I. J.; Craft, A. E.; ...

2016-02-05

In this study, 3-D image analysis when combined with a non-destructive examination technique such as X-ray computed tomography (CT) provides a highly quantitative tool for the investigation of a material’s structure. In this investigation 3-D image analysis and X-ray CT were combined to analyze the microstructure of a preliminary subsized fuel compact for the Transient Reactor Test Facility’s low enriched uranium conversion program to assess the feasibility of the combined techniques for use in the optimization of the fuel compact fabrication process. The quantitative image analysis focused on determining the size and spatial distribution of the surrogate fuel particles andmore » the size, shape, and orientation of voids within the compact. Additionally, the maximum effect of microstructural features on heat transfer through the carbonaceous matrix of the preliminary compact was estimated. The surrogate fuel particles occupied 0.8% of the compact by volume with a log-normal distribution of particle sizes with a mean diameter of 39 μm and a standard deviation of 16 μm. Roughly 39% of the particles had a diameter greater than the specified maximum particle size of 44 μm suggesting that the particles agglomerate during fabrication. The local volume fraction of particles also varies significantly within the compact although uniformities appear to be evenly dispersed throughout the analysed volume. The voids produced during fabrication were on average plate-like in nature with their major axis oriented perpendicular to the compaction direction of the compact. Finally, the microstructure, mainly the large preferentially oriented voids, may cause a small degree of anisotropy in the thermal diffusivity within the compact. α∥/α⊥, the ratio of thermal diffusivities parallel to and perpendicular to the compaction direction are expected to be no less than 0.95 with an upper bound of 1.« less

Research of Surface Roughness Anisotropy

NASA Astrophysics Data System (ADS)

Bulaha, N.; Rudzitis, J.; Lungevics, J.; Linins, O.; Krizbergs, J.

2017-04-01

The authors of the paper have investigated surfaces with irregular roughness for the purpose of determination of roughness spacing parameters perpendicularly to machining traces - RSm1 and parallel to them - RSm2, as well as checking the relationship between the surface anisotropy coefficient c and surface aspect ratio Str from the standard LVS EN ISO 25178-2. Surface roughness measurement experiments with 11 surfaces show that measuring equipment values of mean spacing of profile irregularities in the longitudinal direction are not reliable due to the divergence of surface mean plane and roughness profile mean line. After the additional calculations it was stated that parameter Str can be used for determination of parameter RSm2 and roughness anisotropy evaluation for grinded, polished, friction surfaces and other surfaces with similar characteristics.

Porus electrode comprising a bonded stack of pieces of corrugated metal foil

NASA Technical Reports Server (NTRS)

Mccallum, J. (Inventor)

1973-01-01

An electrode suitable for use in an electrochemical cell is described. The electrode is composed of a porous conductive support with a bonded stack of pieces of thin corrugated nickel foil where the corrugations are oriented approximately perpendicular to the sides of the electrode and form an array of passages through the electrode. Active material such as cadmium hydroxide or nickel hydroxide is uniformly distributed within the passages. The support may comprise also a piece of thin flat nickel foil between adjacent pieces of the corrugated foil, forming a barrier between the passages formed on each side of it. Typically the corrugations in the odd corrugated layers are oriented at a small angle from the perpendicular in one direction and the corrugations in the even corrugated layers are oriented at a small angle from the perpendicular in the opposite direction.

Reduction of Line Edge Roughness of Polystyrene-block-Poly(methyl methacrylate) Copolymer Nanopatterns By Introducing Hydrogen Bonding at the Junction Point of Two Block Chains.

PubMed

Lee, Kyu Seong; Lee, Jaeyong; Kwak, Jongheon; Moon, Hong Chul; Kim, Jin Kon

2017-09-20

To apply well-defined block copolymer nanopatterns to next-generation lithography or high-density storage devices, small line edge roughness (LER) of nanopatterns should be realized. Although polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) has been widely used to fabricate nanopatterns because of easy perpendicular orientation of the block copolymer nanodomains and effective removal of PMMA block by dry etching, the fabricated nanopatterns show poorer line edge roughness (LER) due to relatively small Flory-Huggins interaction parameter (χ) between PS and PMMA chains. Here, we synthesized PS-b-PMMA with urea (U) and N-(4-aminomethyl-benzyl)-4-hydroxymethyl-benzamide (BA) moieties at junction of PS and PMMA chains (PS-U-BA-PMMA) to improve the LER. The U-BA moieties serves as favorable interaction (hydrogen bonding) sites. The LER of PS line patterns obtained from PS-U-BA-PMMA was reduced ∼25% compared with that obtained from neat PS-b-PMMA without BA and U moieties. This is attributed to narrower interfacial width induced by hydrogen bonding between two blocks, which is confirmed by small-angle X-ray scattering. This result implies that the introduction of hydrogen bonding into block copolymer interfaces offers an opportunity to fabricate well-defined nanopatterns with improved LER by block copolymer self-assembly, which could be a promising alternative to next-generation extreme ultraviolet lithography.

Thermal Conductivity Anisotropy of Metasedimentary and Igneous Rocks

NASA Astrophysics Data System (ADS)

Davis, M. G.; Chapman, D. S.; van Wagoner, T. M.; Armstrong, P. A.

2005-12-01

Thermal conductivity anisotropy was determined for two sets of rocks: a series of sandstones, mudstones, and limey shales of Cretaceous age from Price Canyon, Utah, and metasedimentary argillites and quartzites of Precambrian age from the Big Cottonwood Formation in north central Utah. Additional anisotropy measurements were made on granitic rocks from two Tertiary plutons in Little Cottonwood Canyon, north central Utah. Most conductivity measurements were made in transient mode with a half-space, line-source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding. One orientation of the probe yields thermal conductivity parallel to bedding (kmax) directly, the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity (kperp) is calculated. Some direct measurements of kmax and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady-state mode. Anisotropy is defined as kmax/kperp. The Precambrian argillites from Big Cottonwood Canyon have anisotropy values from 0.8 to 2.1 with corresponding conductivity perpendicular to bedding of 2.0 to 6.2 W m-1 K-1. Anisotropy values for the Price Canyon samples are less than 1.2 with a mean of 1.04 although thermal conductivity perpendicular to bedding for the samples varied from 1.3 to 5.0 W m-1 K-1. The granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2.2 to 3.2 W m-1 K-1 and a mean of 2.68 W m-1 K-1. The results confirm the observation by Deming (1994) that anisotropy is negligible for rocks having kperp greater than 4.0 W m-1 K-1 and generally increases for low conductivity metamorphic and clay-rich rocks. There is little evidence, however, for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for low thermal conductivity rocks.

Perpendicular Orientation Control without Interfacial Treatment of RAFT-Synthesized High-χ Block Copolymer Thin Films with Sub-10 nm Features Prepared via Thermal Annealing.

PubMed

Nakatani, Ryuichi; Takano, Hiroki; Chandra, Alvin; Yoshimura, Yasunari; Wang, Lei; Suzuki, Yoshinori; Tanaka, Yuki; Maeda, Rina; Kihara, Naoko; Minegishi, Shinya; Miyagi, Ken; Kasahara, Yuusuke; Sato, Hironobu; Seino, Yuriko; Azuma, Tsukasa; Yokoyama, Hideaki; Ober, Christopher K; Hayakawa, Teruaki

2017-09-20

In this study, a series of perpendicular lamellae-forming poly(polyhedral oligomeric silsesquioxane methacrylate-block-2,2,2-trifluoroethyl methacrylate)s (PMAPOSS-b-PTFEMAs) was developed based on the bottom-up concept of creating a simple yet effective material by tailoring the chemical properties and molecular composition of the material. The use of silicon (Si)-containing hybrid high-χ block copolymers (BCPs) provides easy access to sub-10 nm feature sizes. However, as the surface free energies (SFEs) of Si-containing polymers are typically vastly lower than organic polymers, this tends to result in the selective segregation of the inorganic block onto the air interface and increased difficulty in controlling the BCP orientation in thin films. Therefore, by balancing the SFEs between the organic and inorganic blocks through the use of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) on the organic block, a polymer with an SFE similar to Si-containing polymers, orientation control of the BCP domains in thin films becomes much simpler. Herein, perpendicularly oriented BCP thin films with a χ eff value of 0.45 were fabricated using simple spin-coating and thermal annealing processes under ambient conditions. The thin films displayed a minimum domain size of L 0 = 11 nm, as observed via atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, directed self-assembly (DSA) of the BCP on a topographically prepatterned substrate using the grapho-epitaxy method was used to successfully obtain perpendicularly oriented lamellae with a half pitch size of ca. 8 nm.

Effect of Transducer Orientation on Errors in Ultrasound Image-Based Measurements of Human Medial Gastrocnemius Muscle Fascicle Length and Pennation

PubMed Central

Gandevia, Simon C.; Herbert, Robert D.

2016-01-01

Ultrasound imaging is often used to measure muscle fascicle lengths and pennation angles in human muscles in vivo. Theoretically the most accurate measurements are made when the transducer is oriented so that the image plane aligns with muscle fascicles and, for measurements of pennation, when the image plane also intersects the aponeuroses perpendicularly. However this orientation is difficult to achieve and usually there is some degree of misalignment. Here, we used simulated ultrasound images based on three-dimensional models of the human medial gastrocnemius, derived from magnetic resonance and diffusion tensor images, to describe the relationship between transducer orientation and measurement errors. With the transducer oriented perpendicular to the surface of the leg, the error in measurement of fascicle lengths was about 0.4 mm per degree of misalignment of the ultrasound image with the muscle fascicles. If the transducer is then tipped by 20°, the error increases to 1.1 mm per degree of misalignment. For a given degree of misalignment of muscle fascicles with the image plane, the smallest absolute error in fascicle length measurements occurs when the transducer is held perpendicular to the surface of the leg. Misalignment of the transducer with the fascicles may cause fascicle length measurements to be underestimated or overestimated. Contrary to widely held beliefs, it is shown that pennation angles are always overestimated if the image is not perpendicular to the aponeurosis, even when the image is perfectly aligned with the fascicles. An analytical explanation is provided for this finding. PMID:27294280

Effect of Transducer Orientation on Errors in Ultrasound Image-Based Measurements of Human Medial Gastrocnemius Muscle Fascicle Length and Pennation.

PubMed

Bolsterlee, Bart; Gandevia, Simon C; Herbert, Robert D

2016-01-01

Ultrasound imaging is often used to measure muscle fascicle lengths and pennation angles in human muscles in vivo. Theoretically the most accurate measurements are made when the transducer is oriented so that the image plane aligns with muscle fascicles and, for measurements of pennation, when the image plane also intersects the aponeuroses perpendicularly. However this orientation is difficult to achieve and usually there is some degree of misalignment. Here, we used simulated ultrasound images based on three-dimensional models of the human medial gastrocnemius, derived from magnetic resonance and diffusion tensor images, to describe the relationship between transducer orientation and measurement errors. With the transducer oriented perpendicular to the surface of the leg, the error in measurement of fascicle lengths was about 0.4 mm per degree of misalignment of the ultrasound image with the muscle fascicles. If the transducer is then tipped by 20°, the error increases to 1.1 mm per degree of misalignment. For a given degree of misalignment of muscle fascicles with the image plane, the smallest absolute error in fascicle length measurements occurs when the transducer is held perpendicular to the surface of the leg. Misalignment of the transducer with the fascicles may cause fascicle length measurements to be underestimated or overestimated. Contrary to widely held beliefs, it is shown that pennation angles are always overestimated if the image is not perpendicular to the aponeurosis, even when the image is perfectly aligned with the fascicles. An analytical explanation is provided for this finding.

Crystal orientation of PEO confined within the nanorod templated by AAO nanochannels.

PubMed

Liu, Chien-Liang; Chen, Hsin-Lung

2018-06-18

The orientation of poly(ethylene oxide) (PEO) crystallites developed in the nanochannels of anodic aluminum oxide (AAO) membrane has been investigated. PEO was filled homogeneously into the nanochannels in the melt state, and the crystallization confined within the PEO nanorod thus formed was allowed to take place subsequently at different temperatures. The effects of PEO molecular weight (MPEO), crystallization temperature (Tc) and AAO channel diameter (DAAO) on the crystal orientation attained in the nanorod were revealed by 2-D wide angle X-ray scattering (WAXS) patterns. In the nanochannels with DAAO = 23 nm, the crystallites formed from PEO with the lowest MPEO (= 3400 g mol-1) were found to adopt a predominantly perpendicular orientation with the crystalline stems aligning normal to the channel axis irrespective of Tc (ranging from -40 to 20 °C). Increasing MPEO or decreasing Tc tended to induce the development of the tilt orientation characterized by the tilt of the (120) plane by 45° from the channel axis. In the case of the highest MPEO (= 95 000 g mol-1) studied, both perpendicular and tilt orientations coexisted irrespective of Tc. Coexistent orientation was always observed in the channels with a larger diameter (DAAO = 89 nm) irrespective of MPEO and Tc. Compared with the previous results of the crystal orientation attained in nanotubes templated by the preferential wetting of the channel walls by PEO, the window of the perpendicular crystal orientation in the nanorod was much narrower due to its weaker confinement effect imposed on the crystal growth than that set by the nanotube.

Highly controlled orientation of CaBi4Ti4O15 using a strong magnetic field

NASA Astrophysics Data System (ADS)

Suzuki, Tohru S.; Kimura, Masahiko; Shiratsuyu, Kosuke; Ando, Akira; Sakka, Yoshio; Sakabe, Yukio

2006-09-01

The texture of feeble magnetic ceramics can be controlled by a strong magnetic field. When the magnetic susceptibility of the c axis is smaller than that of the other axes, the c axis aligns perpendicular to the magnetic field; however, the direction is randomly oriented on the plane perpendicular to the magnetic field. The authors demonstrate in this letter that a highly controlled texture in bismuth titanate, which has a c-axis susceptibility smaller than the other axes, can be achieved using a two-step magnetic field procedure. This highly controlled orientation is effective for improving the electromechanical coupling coefficient.

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

Chen, Wei; Boehlert, C. J.

The tensile properties of extruded Ti 6Al 4V xB alloys (wt.%) were evaluated in an orientation perpendicular to the extrusion direction at room-temperature and 455 C. The extrusion process preferentially oriented the basal plane of -Ti perpendicular to the extrusion axis. This strong - phase texture resulted in tensile anisotropy. The tensile strength in the transverse orientation was lower than that in the longitudinal orientation, but it remained greater than that for the ascast Ti 6Al 4V. The TiB phasewas aligned in the extrusion direction and increased B content was found to weaken the -phase texture, causing a weakening ofmore » tensile anisotropy. Debonding was not observed during the tensile tests in the transverse orientation, indicating a strong interface bond exists between the TiB phase and the two-phase ( + ) Ti 6Al 4V matrix.« less

Shingle assembly

DOEpatents

Dinwoodie, Thomas L.

2007-02-20

A barrier, such as a PV module, is secured to a base by a support to create a shingle assembly with a venting region defined between the barrier and base for temperature regulation. The first edge of one base may be interengageable with the second edge of an adjacent base to be capable of resisting first and second disengaging forces oriented perpendicular to the edges and along planes oriented parallel to and perpendicular to the base. A deflector may be used to help reduce wind uplift forces.

Fe-Al alloy single-crystal thin film preparation for basic magnetic measurements

NASA Astrophysics Data System (ADS)

Abe, Tatsuya; Kawai, Tetsuroh; Futamoto, Masaaki; Ohtake, Mitsuru; Inaba, Nobuyuki

2018-04-01

Fe100-xAlx (x = 0, 4, 10, 20, 30 at. %) alloy films of 40 nm thickness are prepared on MgO(001) single-crystal substrates by varying substrate temperature from room temperature to 600 °C. Single-crystal films of (001) orientation with bcc-based disordered A2 structure are obtained for the Al content range of x = 0 - 20 at. %. An ordered phase of DO3 structure is observed in Fe70Al30 films prepared at temperatures higher than 200 °C, whereas (001) oriented single-crystal films of A2 structure are obtained when prepared at room temperature. The film surface profile does not depend much on the film composition, while the surface roughness increases with increasing substrate temperature. Island-like crystals are observed for films prepared at 600°C for all compositions. Difference in lattice spacing measured parallel and perpendicular to the substrate is noted for the single-crystal thin films and it increases with increasing Al content. The lattice strain in single-crystal film is caused possibly to accommodate the lattice mismatch with the MgO substrate. The (001)-oriented single-crystal films with A2 structure show four-fold symmetries in in-plane magnetic anisotropy with the easy magnetization axis A2[100] and the hard magnetization axis A2[110], whereas the films with DO3 ordered structure show almost isotropic magnetic properties.

Application of Borehole Geophysical Methods for Assessing Agro-Chemical Flow Paths in Fractured Bedrock Underlying the Black Brook Watershed, Northwestern New Brunswick

NASA Astrophysics Data System (ADS)

Desroches, A.; Butler, K.

2009-05-01

The upper Saint John River valley represents an economically important agricultural region that suffers from high nitrate levels in the groundwater as a result of fertilizer use. This study focuses on the fractured bedrock aquifer beneath the Black Brook Watershed, near Saint-Andre (Grand Falls), New Brunswick, where prediction of nitrate migration is limited by a lack of knowledge of the bedrock fracture characteristics. Bedrock consists of a fine-grained, siliciclastic unit of the Grog Brook Group gradationally overlain by a carbonate unit assigned to the Matapédia Group. Groundwater flow through the fractured bedrock is expected to be primarily influenced by the distribution and orientation of fractures in these rock units. This study demonstrates the effectiveness of the select suite of borehole-geophysical tools used to identify and describe the fractured bedrock characteristics, and assists in understanding the migration pathways of agrochemical leachate from farm fields. Fracture datasets were acquired from five new vertical boreholes that ranged from 50 to 140 metres in depth, and from three outcrop locations along the new Trans-Canada Highway, approximately two kilometres away. The borehole-geophysical methods used included natural gamma ray (GR), single point resistance (SPR), spontaneous potential (SP), slim-hole optical borehole televiewer (OBI) and acoustic borehole televiewer (ABI). The ABI and OBI tools delivered high-resolution oriented images of the borehole walls, and enabled visualization of fractures in situ, and provided accurate information on the location, orientation, and aperture. The GR, SPR and SP logs identified changes in lithology, bed thickness and conductive fracture zones. Detailed inspection of the borehole televiewer images identified 390 fractures. Equal-area stereographic and rose diagrams of fracture planes have been used to identify three discrete fracture sets: 1) steeply dipping fractures that strike 068o/248o, with fracture subsets dipping roughly 70o to 80o towards the N-NW and S-SE; 2) steeply dipping fractures that strike towards 156o/336o, with fracture subsets dipping roughly 70o to 80o towards the NE and SW; and 3) primary set of moderately dipping fractures that strike 074o/254o and dip roughly 30o to 40o towards the SE. The strike of the steeply dipping fracture sets are oriented roughly perpendicular to each other, reflecting two distinct fracture generation events. The low-angle fractures are most common and correspond to openings along bedding planes that dip roughly 38o towards 164o. This is a result of penetrating only one limb of a fold; presumably a similar set of bedding-plane openings occur along the adjacent limb of the fold, with resultant fracture dips towards the northwest. Fractures exposed in outcrops along the Trans-Canada Highway exhibit a similar orientation distribution to that observed in the boreholes. However, as expected, these exposures show a greater proportion of fractures with dips between 80o and 90o, compared to the vertical boreholes. A Terzaghi fracture probability correction was applied to the boreholes in order to account for this bias. The combined fracture datasets provide valuable information towards understanding groundwater flow and migration pathways of fertilizer leachate into the bedrock aquifer, and will lead to the development of more complex hydrogeological models.

Orientation of ripples induced by ultrafast laser pulses on copper in different liquids

NASA Astrophysics Data System (ADS)

Maragkaki, Stella; Elkalash, Abdallah; Gurevich, Evgeny L.

2017-12-01

Formation of laser-induced periodic surface structures (LIPSS or ripples) was studied on a metallic surface of polished copper using irradiation with multiple femtosecond laser pulses in different environmental conditions (air, water, ethanol and methanol). Uniform LIPSS have been achieved by controlling the peak fluence and the overlapping rate. Ripples in both orientations, perpendicular and parallel to laser polarization, were observed in all liquids simultaneously. The orientation of these ripples in the center of the ablated line was changing with the incident light intensity. For low intensities the orientation of the ripples is perpendicular to the laser polarization, whereas for high intensities it turns parallel to it without considerable changes in the period. Multi-directional LIPSS formation was also observed for moderate peak fluence in liquid environments.

3D Printed, Microgroove Pattern-Driven Generation of Oriented Ligamentous Architectures.

PubMed

Park, Chan Ho; Kim, Kyoung-Hwa; Lee, Yong-Moo; Giannobile, William V; Seol, Yang-Jo

2017-09-08

Specific orientations of regenerated ligaments are crucially required for mechanoresponsive properties and various biomechanical adaptations, which are the key interplay to support mineralized tissues. Although various 2D platforms or 3D printing systems can guide cellular activities or aligned organizations, it remains a challenge to develop ligament-guided, 3D architectures with the angular controllability for parallel, oblique or perpendicular orientations of cells required for biomechanical support of organs. Here, we show the use of scaffold design by additive manufacturing for specific topographies or angulated microgroove patterns to control cell orientations such as parallel (0°), oblique (45°) and perpendicular (90°) angulations. These results demonstrate that ligament cells displayed highly predictable and controllable orientations along microgroove patterns on 3D biopolymeric scaffolds. Our findings demonstrate that 3D printed topographical approaches can regulate spatiotemporal cell organizations that offer strong potential for adaptation to complex tissue defects to regenerate ligament-bone complexes.

Cross-bedding related anisotropy and its interplay with various boundary conditions in the formation and orientation of joints in an aeolian sandstone

NASA Astrophysics Data System (ADS)

Deng, Shang; Cilona, Antonino; Morrow, Carolyn; Mapeli, Cesar; Liu, Chun; Lockner, David; Prasad, Manika; Aydin, Atilla

2015-08-01

Previous research revealed that the cross-bedding related anisotropy in Jurassic aeolian Aztec Sandstone cropping out in the Valley of Fire State Park, Nevada, affects the orientation of compaction bands, also known as anti-cracks or closing mode structures. We hypothesize that cross-bedding should have a similar influence on the orientation of the opening mode joints within the same rock at the same location. To test this hypothesis, we investigated the relationship between the orientation of cross-beds and the orientation of different categories of joint sets including cross-bed package confined joints and joint zones in the Aztec Sandstone. The field data show that the cross-bed package confined joints occur at high-angle to bedding and trend roughly parallel to the dip direction of the cross-beds. In comparison, the roughly N-S trending joint zones appear not to be influenced by the cross-beds in any significant way but frequently truncate against the dune boundaries. To characterize the anisotropy due to cross-bedding in the Aztec Sandstone, we measured the P-wave velocities parallel and perpendicular to bedding from 11 samples and determined an average P-wave anisotropy to be slightly larger than 13%. From these results, a model based on the generalized Hooke's law for anisotropic materials is used to analyze deformation of cross-bedded sandstone as a transversely isotropic material. In the analysis, the dip angle of cross-beds is assumed to be constant and the strike orientation varying from 0° to 359° in the east (x), north (y), and up (z) coordinate system. We find qualitative agreement between most of the model results and the observed field relations between cross-beds and the corresponding joint sets. The results also suggest that uniaxial extension (εzz > εxx = εyy = 0) and axisymmetric extension (εxx = εyy < εzz and εxx = εyy > εzz) would amplify the influence of cross-bedding associated anisotropy on the joint orientation whereas a triaxial extension (εxx > εyy > εzz) would mitigate this influence. We suggest that the potential implication of different categories of joint sets (i.e., cross-bed package confined joints and joint zones) forming in response to the variation of the boundary conditions (axisymmetric extension and triaxial extension, respectively) and the interplay with the rock anisotropy is significant. These results have important implications for fluid flow through aeolian sandstones in reservoirs and aquifers.

Feasibilty of a Multi-bit Cell Perpendicular Magnetic Tunnel Junction Device

NASA Astrophysics Data System (ADS)

Kim, Chang Soo

The ultimate objective of this research project was to explore the feasibility of making a multi-bit cell perpendicular magnetic tunnel junction (PMTJ) device to increase the storage density of spin-transfer-torque random access memory (STT-RAM). As a first step toward demonstrating a multi-bit cell device, this dissertation contributed a systematic and detailed study of developing a single cell PMTJ device using L10 FePt films. In the beginning of this research, 13 up-and-coming non-volatile memory (NVM) technologies were investigated and evaluated to see whether one of them might outperform NAND flash memories and even HDDs on a cost-per-TB basis in 2020. This evaluation showed that STT-RAM appears to potentially offer superior power efficiency, among other advantages. It is predicted that STTRAM's density could make it a promising candidate for replacing NAND flash memories and possibly HDDs if STTRAM could be improved to store multiple bits per cell. Ta/Mg0 under-layers were used first in order to develop (001) L1 0 ordering of FePt at a low temperature of below 400 °C. It was found that the tradeoff between surface roughness and (001) L10 ordering of FePt makes it difficult to achieve low surface roughness and good perpendicular magnetic properties simultaneously when Ta/Mg0 under-layers are used. It was, therefore, decided to investigate MgO/CrRu under-layers to simultaneously achieve smooth films with good ordering below 400°C. A well ordered 4 nm L10 FePt film with RMS surface roughness close to 0.4 nm, perpendicular coercivity of about 5 kOe, and perpendicular squareness near 1 was obtained at a deposition temperature of 390 °C on a thermally oxidized Si substrate when MgO/CrRu under-layers are used. A PMTJ device was developed by depositing a thin MgO tunnel barrier layer and a top L10 FePt film and then being postannealed at 450 °C for 30 minutes. It was found that the sputtering power needs to be minimized during the thin MgO tunnel barrier deposition because the high sputtering power can degrade perpendicular magnetic anisotropy of the bottom L1 0 FePt film and also increase RMS film surface roughness of the MgO tunnel barrier layer. From a lithographically unpatterned PMTJ sample, MR ratio and RA were measured at room temperature by the CIPT method and found to be 138% and 6.4 kOmicrom2, respectively. A completed PMTJ test pattern with a junction size of 80x40 microm2 was fabricated and showed a measured MR ratio and RA product of 108% and 4~6 kOmicrom 2, respectively. These values agree relatively well with the corresponding values of 138% and 6.4 kOmicrom2 obtained from the unpatterned PMTJ sample measured by a current-in-plane tunneling (CIPT) method.

Anisotropy in Third-Order Nonlinear Optical Susceptibility of a Squarylium Dye in a Nematic Liquid Crystal

NASA Astrophysics Data System (ADS)

Jin, Zhao-Hui; Li, Zhong-Yu; Kasatani, Kazuo; Okamoto, Hiroaki

2006-03-01

A squarylium dye is dissolved in 4-cyano-4'-pentylbiphenyl (5CB) and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB layers exhibit high anisotropy. The third-order nonlinear optical responses and susceptibilities χ(3)e of squarylium dye in 5CB are measured with light polarizations parallel and perpendicular to the orientational direction by the resonant femtosecond degenerate four-wave mixing (DFWM) technique. Temporal profiles of the DFWM signal of the oriented squarylium dye-5CB layers with light polarizations parallel and perpendicular to the orientational direction are measured with a time resolution of 0.3 ps (FWHM), and are found to consist of two components, i.e., the coherent instantaneous nonlinear response and slow response due to the formation of excited molecules. A high anisotropic ratio of χ(3)e, 10.8±1.2, is observed for the oriented layers.

Unidirectionally oriented nanocracks on metal surfaces irradiated by low-fluence femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Shimizu, Masahiro; Hashida, Masaki; Miyasaka, Yasuhiro; Tokita, Shigeki; Sakabe, Shuji

2013-10-01

We have investigated the origin of nanostructures formed on metals by low-fluence femtosecond laser pulses. Nanoscale cracks oriented perpendicular to the incident laser polarization are induced on tungsten, molybdenum, and copper targets. The number density of the cracks increases with the number of pulses, but crack length plateaus. Electromagnetic field simulation by the finite-difference time-domain method indicates that electric field is locally enhanced along the direction perpendicular to the incident laser polarization around a nanoscale hole on the metal surface. Crack formation originates from the hole.

Induction logging device with a pair of mutually perpendicular bucking coils

DOEpatents

Koelle, Alfred R.; Landt, Jeremy A.

1981-01-01

An instrument is disclosed for mapping vertical conductive fractures in a resistive bedrock, magnetically inducing eddy currents by a pair of vertically oriented, mutually perpendicular, coplanar coils. The eddy currents drive magnetic fields which are picked up by a second, similar pair of coils.

Roughness of Ti Substrates for Control of the Preferred Orientation of TiO 2 Nanotube Arrays as a New Orientation Factor

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

Seong, Won Mo; Kim, Dong Hoe; Park, Ik Jae

2015-06-11

We report the surface roughness of a Ti substrate as a critical factor for controlling the degree of the preferred orientation of anatase TiO2 nanotube arrays (NTAs) which are synthesized by anodization and a subsequent annealing process. The degree of the preferred orientation to the (004) plane of the anatase crystal structure has a strong dependency on the root-mean-square roughness (Sq) of the initial Ti substrate when the roughness-controlled substrates are anodized in an ethylene glycol-based electrolyte containing ~2 wt % of water. Highly preferred oriented NTAs were obtained from low-Sq (<10 nm) substrates, which were accompanied by uniform poremore » distribution and low concentration of hydroxyl ions in as-anodized amorphous NTAs. The mechanism of the preferred oriented crystallization of nanometer-scaled tube walls is explained considering the microscopic geometrical uniformity of the oxide barrier and nanopores at the early stage of anodization, which affected the local electric field and thus the insertion of the hydroxyl group into the amorphous TiO2 tube walls.« less

Anomalous Swelling in Wet-Spin Films of Divalent Calf-Thymus DNA

NASA Astrophysics Data System (ADS)

Marlowe, R. L.; Lee, S. A.; Rupprecht, A.

2004-03-01

The dimension of wet-spun oriented films of Ca- and MgDNA in the direction perpendicular to the helical axis has been measured using optical microscopy as a function of relative humidity (RH). Earlier work on monovalent DNA films found that the perpendicular dimension increases monotonically with RH. In contrast, both Ca - and MgDNA films display a 15% shrinkage in the perpendicular direction at about 93% RH and expand at higher values of RH.

The coil orientation dependency of the electric field induced by TMS for M1 and other brain areas.

PubMed

Janssen, Arno M; Oostendorp, Thom F; Stegeman, Dick F

2015-05-17

The effectiveness of transcranial magnetic stimulation (TMS) depends highly on the coil orientation relative to the subject's head. This implies that the direction of the induced electric field has a large effect on the efficiency of TMS. To improve future protocols, knowledge about the relationship between the coil orientation and the direction of the induced electric field on the one hand, and the head and brain anatomy on the other hand, seems crucial. Therefore, the induced electric field in the cortex as a function of the coil orientation has been examined in this study. The effect of changing the coil orientation on the induced electric field was evaluated for fourteen cortical targets. We used a finite element model to calculate the induced electric fields for thirty-six coil orientations (10 degrees resolution) per target location. The effects on the electric field due to coil rotation, in combination with target site anatomy, have been quantified. The results confirm that the electric field perpendicular to the anterior sulcal wall of the central sulcus is highly susceptible to coil orientation changes and has to be maximized for an optimal stimulation effect of the motor cortex. In order to obtain maximum stimulation effect in areas other than the motor cortex, the electric field perpendicular to the cortical surface in those areas has to be maximized as well. Small orientation changes (10 degrees) do not alter the induced electric field drastically. The results suggest that for all cortical targets, maximizing the strength of the electric field perpendicular to the targeted cortical surface area (and inward directed) optimizes the effect of TMS. Orienting the TMS coil based on anatomical information (anatomical magnetic resonance imaging data) about the targeted brain area can improve future results. The standard coil orientations, used in cognitive and clinical neuroscience, induce (near) optimal electric fields in the subject-specific head model in most cases.

Setting Directions: Anisotropy in Hierarchically Organized Porous Silica

PubMed Central

2017-01-01

Structural hierarchy, porosity, and isotropy/anisotropy are highly relevant factors for mechanical properties and thereby the functionality of porous materials. However, even though anisotropic and hierarchically organized, porous materials are well known in nature, such as bone or wood, producing the synthetic counterparts in the laboratory is difficult. We report for the first time a straightforward combination of sol–gel processing and shear-induced alignment to create hierarchical silica monoliths exhibiting anisotropy on the levels of both, meso- and macropores. The resulting material consists of an anisotropic macroporous network of struts comprising 2D hexagonally organized cylindrical mesopores. While the anisotropy of the mesopores is an inherent feature of the pores formed by liquid crystal templating, the anisotropy of the macropores is induced by shearing of the network. Scanning electron microscopy and small-angle X-ray scattering show that the majority of network forming struts is oriented towards the shearing direction; a quantitative analysis of scattering data confirms that roughly 40% of the strut volume exhibits a preferred orientation. The anisotropy of the material’s macroporosity is also reflected in its mechanical properties; i.e., the Young’s modulus differs by nearly a factor of 2 between the directions of shear application and perpendicular to it. Unexpectedly, the adsorption-induced strain of the material exhibits little to no anisotropy. PMID:28989232

Method for adhering a coating to a substrate structure

DOEpatents

Taxacher, Glenn Curtis; Crespo, Andres Garcia; Roberts, III, Herbert Chidsey

2015-02-17

A method for adhering a coating to a substrate structure comprises selecting a substrate structure having an outer surface oriented substantially parallel to a direction of radial stress, modifying the outer surface to provide a textured region having steps to adhere a coating thereto, and applying a coating to extend over at least a portion of the textured region, wherein the steps are oriented substantially perpendicular to the direction of radial stress to resist deformation of the coating relative to the substrate structure. A rotating component comprises a substrate structure having an outer surface oriented substantially parallel to a direction of radial stress. The outer surface defines a textured region having steps to adhere a coating thereto, and a coating extends over at least a portion of the textured region. The steps are oriented substantially perpendicular to the direction of radial stress to resist creep.

Effects of Cutout Orientations on Natural Frequencies and Mode Shapes of Curved Rectangular Composite Panels.

DTIC Science & Technology

1986-12-01

line perpendicular to the midsurface to remain straight and perpendicular under deformation is the equivalent to ignoring the shear strains in planes...perpendicular to the -. nidsurface, or vxz=vyz=0 , where z is the direction normal to the midsurface in Figure 1. In addition, the normals are 4...integration, but are functions of x and y only, the coordinates in the plane of the laminate midsurface E43. 13 S.* e .. .’. . . o ’ . J

Alignment between Protostellar Outflows and Filamentary Structure

NASA Astrophysics Data System (ADS)

Stephens, Ian W.; Dunham, Michael M.; Myers, Philip C.; Pokhrel, Riwaj; Sadavoy, Sarah I.; Vorobyov, Eduard I.; Tobin, John J.; Pineda, Jaime E.; Offner, Stella S. R.; Lee, Katherine I.; Kristensen, Lars E.; Jørgensen, Jes K.; Goodman, Alyssa A.; Bourke, Tyler L.; Arce, Héctor G.; Plunkett, Adele L.

2017-09-01

We present new Submillimeter Array (SMA) observations of CO(2-1) outflows toward young, embedded protostars in the Perseus molecular cloud as part of the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. For 57 Perseus protostars, we characterize the orientation of the outflow angles and compare them with the orientation of the local filaments as derived from Herschel observations. We find that the relative angles between outflows and filaments are inconsistent with purely parallel or purely perpendicular distributions. Instead, the observed distribution of outflow-filament angles are more consistent with either randomly aligned angles or a mix of projected parallel and perpendicular angles. A mix of parallel and perpendicular angles requires perpendicular alignment to be more common by a factor of ˜3. Our results show that the observed distributions probably hold regardless of the protostar’s multiplicity, age, or the host core’s opacity. These observations indicate that the angular momentum axis of a protostar may be independent of the large-scale structure. We discuss the significance of independent protostellar rotation axes in the general picture of filament-based star formation.

Containment of groundwater contamination plumes: minimizing drawdown by aligning capture wells parallel to regional flow

NASA Astrophysics Data System (ADS)

Christ, John A.; Goltz, Mark N.

2004-01-01

Pump-and-treat systems that are installed to contain contaminated groundwater migration typically involve placement of extraction wells perpendicular to the regional groundwater flow direction at the down gradient edge of a contaminant plume. These wells capture contaminated water for above ground treatment and disposal, thereby preventing further migration of contaminated water down gradient. In this work, examining two-, three-, and four-well systems, we compare well configurations that are parallel and perpendicular to the regional groundwater flow direction. We show that orienting extraction wells co-linearly, parallel to regional flow, results in (1) a larger area of aquifer influenced by the wells at a given total well flow rate, (2) a center and ultimate capture zone width equal to the perpendicular configuration, and (3) more flexibility with regard to minimizing drawdown. Although not suited for some scenarios, we found orienting extraction wells parallel to regional flow along a plume centerline, when compared to a perpendicular configuration, reduces drawdown by up to 7% and minimizes the fraction of uncontaminated water captured.

An improved two-dimensional depth-integrated flow equation for rough-walled fractures

NASA Astrophysics Data System (ADS)

Mallikamas, Wasin; Rajaram, Harihar

2010-08-01

We present the development of an improved 2-D flow equation for rough-walled fractures. Our improved equation accounts for the influence of midsurface tortuosity and the fact that the aperture normal to the midsurface is in general smaller than the vertical aperture. It thus improves upon the well-known Reynolds equation that is widely used for modeling flow in fractures. Unlike the Reynolds equation, our approach begins from the lubrication approximation applied in an inclined local coordinate system tangential to the fracture midsurface. The local flow equation thus obtained is rigorously transformed to an arbitrary global Cartesian coordinate system, invoking the concepts of covariant and contravariant transformations for vectors defined on surfaces. Unlike previously proposed improvements to the Reynolds equation, our improved flow equation accounts for tortuosity both along and perpendicular to a flow path. Our approach also leads to a well-defined anisotropic local transmissivity tensor relating the representations of the flux and head gradient vectors in a global Cartesian coordinate system. We show that the principal components of the transmissivity tensor and the orientation of its principal axes depend on the directional local midsurface slopes. In rough-walled fractures, the orientations of the principal axes of the local transmissivity tensor will vary from point to point. The local transmissivity tensor also incorporates the influence of the local normal aperture, which is uniquely defined at each point in the fracture. Our improved flow equation is a rigorous statement of mass conservation in any global Cartesian coordinate system. We present three examples of simple geometries to compare our flow equation to analytical solutions obtained using the exact Stokes equations: an inclined parallel plate, and circumferential and axial flows in an incomplete annulus. The effective transmissivities predicted by our flow equation agree very well with values obtained using the exact Stokes equations in all these cases. We discuss potential limitations of our depth-integrated equation, which include the neglect of convergence/divergence and the inaccuracies implicit in any depth-averaging process near sharp corners where the wall and midsurface curvatures are large.

Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) Heusler alloy and NiAl spacer

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

Chen, Jiamin; Hono, K., E-mail: kazuhiro.hono@nims.go.jp; Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-2-1, Sengen, Tsukuba 305-0047

2015-05-07

We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (112{sup ¯}0) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation,more » which made it a good candidate for CPP-GMR device.« less

Investigation of roughing machining simulation by using visual basic programming in NX CAM system

NASA Astrophysics Data System (ADS)

Hafiz Mohamad, Mohamad; Nafis Osman Zahid, Muhammed

2018-03-01

This paper outlines a simulation study to investigate the characteristic of roughing machining simulation in 4th axis milling processes by utilizing visual basic programming in NX CAM systems. The selection and optimization of cutting orientation in rough milling operation is critical in 4th axis machining. The main purpose of roughing operation is to approximately shape the machined parts into finished form by removing the bulk of material from workpieces. In this paper, the simulations are executed by manipulating a set of different cutting orientation to generate estimated volume removed from the machine parts. The cutting orientation with high volume removal is denoted as an optimum value and chosen to execute a roughing operation. In order to run the simulation, customized software is developed to assist the routines. Operations build-up instructions in NX CAM interface are translated into programming codes via advanced tool available in the Visual Basic Studio. The codes is customized and equipped with decision making tools to run and control the simulations. It permits the integration with any independent program files to execute specific operations. This paper aims to discuss about the simulation program and identifies optimum cutting orientations for roughing processes. The output of this study will broaden up the simulation routines performed in NX CAM systems.

On the tungsten single crystal coatings achieved by chemical vapor transportation deposition

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

Shi, J.Q.; Shen, Y.B.; Yao, S.Y.

2016-12-15

The tungsten single crystal has many excellent properties, namely a high melting point, high anti-creeping strength. Chemical vapor transportation deposition (CVTD) is a possible approach to achieve large-sized W single crystals for high-temperature application such as the cathode of a thermionic energy converter. In this work, CVTD W coatings were deposited on the monocrystalline molybdenum substrate (a tube with < 111 > axial crystalline orientation) using WCl{sub 6} as a transport medium. The microstructures of the coatings were investigated by a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The as-deposited coatings are hexagonal prisms—rough surfaces perpendicular to with alternating hill-like bulges and pits at the side edges of the prisms, and flat surfaces perpendicular to < 112 > with arc-shaped terraces at the side faces. This can be explained by two-dimensional nucleation -mediated lateral growth model. Some parts of the coatings contain hillocks of an exotic morphology (noted as “abnormal growth”). The authors hypothesize that the abnormal growth is likely caused by the defects of the Mo substrate, which facilitate W nucleation sites, cause orientation difference, and may even form boundaries in the coatings. A dislocation density of 10{sup 6} to 10{sup 7} (counts/cm{sup 2}) was revealed by an etch-pit method and synchrotron X-ray diffraction. As the depositing temperature rises, the dislocation density decreases, and no sub-boundaries are found on samples deposited over 1300 °C, as a result of atom diffusion and dislocation climbing. - Highlights: •The varied growth rate causes the different morphologies of different planes. •The W coating is a single crystal when only single hillocks appear. •The (110) plane tends to have the lowest dislocation density. •The dislocation density tends to decrease as the temperature increases.« less

Navy Prototype Optical Interferometer Imaging of Line Emission Regions of Beta Lyrae Using Differential Phase Referencing

DTIC Science & Technology

2009-02-01

is polarized by a structure perpendicular to this direction. Another result that confirms this geometry is a radio nebula along p.a. 156◦ ± 4...2000) detected a jetlike nebular structure oriented along p.a. = 156◦.5 ± 4◦. This nebula is perpendicular, within uncertainties, to the orbit

Estimation of gloss from rough surface parameters

NASA Astrophysics Data System (ADS)

Simonsen, Ingve; Larsen, Åge G.; Andreassen, Erik; Ommundsen, Espen; Nord-Varhaug, Katrin

2005-12-01

Gloss is a quantity used in the optical industry to quantify and categorize materials according to how well they scatter light specularly. With the aid of phase perturbation theory, we derive an approximate expression for this quantity for a one-dimensional randomly rough surface. It is demonstrated that gloss depends in an exponential way on two dimensionless quantities that are associated with the surface randomness: the root-mean-square roughness times the perpendicular momentum transfer for the specular direction, and a correlation function dependent factor times a lateral momentum variable associated with the collection angle. Rigorous Monte Carlo simulations are used to access the quality of this approximation, and good agreement is observed over large regions of parameter space.

Characterization of rf-SSET in both in-plane and perpendicular magnetic fields

NASA Astrophysics Data System (ADS)

Tang, Chunyang; Yang, Zhen; Yuan, Mingyun; Rimberg, A. J.; Savage, D. E.; Eriksson, M. A.; Rimberg Team; Eriksson Collaboration

2013-03-01

Previous success in coupling an aluminum radio-frequency superconducting single electron transistor (rf-SSET) to quantum dots (QDs) has demonstrated use of the rf-SSET as an ultra-sensitive and fast charge sensor. Since a magnetic field is usually necessary for quantum dot qubit manipulation, it is important to understand the effect of magnetic fields, either in-plane or perpendicular, on the performance of any charge sensor near the QDs. Here we report characterization of rf-SSETs in both in-plane and perpendicular magnetic fields. The rf-SSET works well in an in-plane fields up to 1 Tesla at a temperature of 30 mK. At 0.3K, in a perpendicular field generated by a stripline located 700 nm away, the rf-SSET charge sensitivity even shows improvement for up to 2.1 mA current through the stripline (corresponding roughly to a field of 6 Gauss). This work was supported by NSA, LPS and ARO

Effect of crystal orientation on conductivity and electron mobility in single-crystal alumina

NASA Technical Reports Server (NTRS)

Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

1992-01-01

The electrical conductivity of high-purity, single-crystal alumina is determined parallel to and perpendicular to the c-axis. The mean conductivity of four samples of each orientation is a factor 3.3 higher parallel to the c-axis than perpendicular to it. The conductivity as a function of temperature is attributed to extrinsic electron conduction at temperatures from 400 to 900 C, and intrinsic semiconduction at temperatures from 900 to 1300 C. In the high-temperature regime, the slope on all eight specimens is 4.7 +/- 0.1 eV. Hence, the thermal bandgap at O K is 9.4 +/- 0.2 eV.

Oxidation behavior of grain boundary engineered alloy 690 in supercritical water environment

NASA Astrophysics Data System (ADS)

Xu, P.; Zhao, L. Y.; Sridharan, K.; Allen, T. R.

2012-03-01

Nickel-base alloy is an important structural material that is known for its exceptional high temperature oxidation resistance. Oxidation in this alloy at high temperatures occurs to a greater extent along the grain boundaries. Grain boundary engineering (GBE) was applied to modify the grain boundary characteristics of this alloy to affect its oxidation resistance. Specimens with both low level and high level cold works showed a high fraction of special grain boundaries, and were tested for supercritical water oxidation resistance at 500 °C and 24 MPa. Both GBE and as-received samples exhibited mass gain followed by mass loss during 10 weeks of exposure, but the normalized mass change was small and less than 0.12 mg/cm2. GBE samples showed better oxide layer retention compared to the as-received sample. XRD results indicate that nickel oxide, chromium oxide, and spinel oxide were the three main types of oxides that form on as-received and GBE alloy 690. Three distinct regions were identified on the oxidized surface: a flat region with oxide flakes aligning relatively parallel to the surface, a rough region with polygon-type oxide particles randomly distributed on the surface, and a region with aggregated oxide flakes perpendicular to the surface. The flat region of oxidation consisted of (1 1 1) orientated oxide spinel flakes formed on (1 1 1) oriented alloy 690 grains. The flat oxide region was thinner and showed better oxide adhesion compared to the rough region. Chromium oxidation was found only at random grain boundaries, leading to formation of thick Cr2O3 layer on the surface and chromium depletion underneath. None of this oxidation was found at low angle or special boundaries. The chromium oxidation was attributed to fast chromium diffusion through random boundaries and mechanically deformed regions such as scratches left after polishing. It is envisioned that the oxidation behavior of alloy 690 in supercritical water can be tailored by microstructure engineering that involves changes in grain orientation and grain boundary character distribution.

A multi-directional and multi-scale roughness filter to detect lineament segments on digital elevation models - analyzing spatial objects in R

NASA Astrophysics Data System (ADS)

Baumann, Sebastian; Robl, Jörg; Wendt, Lorenz; Willingshofer, Ernst; Hilberg, Sylke

2016-04-01

Automated lineament analysis on remotely sensed data requires two general process steps: The identification of neighboring pixels showing high contrast and the conversion of these domains into lines. The target output is the lineaments' position, extent and orientation. We developed a lineament extraction tool programmed in R using digital elevation models as input data to generate morphological lineaments defined as follows: A morphological lineament represents a zone of high relief roughness, whose length significantly exceeds the width. As relief roughness any deviation from a flat plane, defined by a roughness threshold, is considered. In our novel approach a multi-directional and multi-scale roughness filter uses moving windows of different neighborhood sizes to identify threshold limited rough domains on digital elevation models. Surface roughness is calculated as the vertical elevation difference between the center cell and the different orientated straight lines connecting two edge cells of a neighborhood, divided by the horizontal distance of the edge cells. Thus multiple roughness values depending on the neighborhood sizes and orientations of the edge connecting lines are generated for each cell and their maximum and minimum values are extracted. Thereby negative signs of the roughness parameter represent concave relief structures as valleys, positive signs convex relief structures as ridges. A threshold defines domains of high relief roughness. These domains are thinned to a representative point pattern by a 3x3 neighborhood filter, highlighting maximum and minimum roughness peaks, and representing the center points of lineament segments. The orientation and extent of the lineament segments are calculated within the roughness domains, generating a straight line segment in the direction of least roughness differences. We tested our algorithm on digital elevation models of multiple sources and scales and compared the results visually with shaded relief map of these digital elevation models. The lineament segments trace the relief structure to a great extent and the calculated roughness parameter represents the physical geometry of the digital elevation model. Modifying the threshold for the surface roughness value highlights different distinct relief structures. Also the neighborhood size at which lineament segments are detected correspond with the width of the surface structure and may be a useful additional parameter for further analysis. The discrimination of concave and convex relief structures perfectly matches with valleys and ridges of the surface.

Alignment between Protostellar Outflows and Filamentary Structure

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

Stephens, Ian W.; Dunham, Michael M.; Myers, Philip C.

2017-09-01

We present new Submillimeter Array (SMA) observations of CO(2–1) outflows toward young, embedded protostars in the Perseus molecular cloud as part of the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. For 57 Perseus protostars, we characterize the orientation of the outflow angles and compare them with the orientation of the local filaments as derived from Herschel observations. We find that the relative angles between outflows and filaments are inconsistent with purely parallel or purely perpendicular distributions. Instead, the observed distribution of outflow-filament angles are more consistent with either randomly aligned angles or a mixmore » of projected parallel and perpendicular angles. A mix of parallel and perpendicular angles requires perpendicular alignment to be more common by a factor of ∼3. Our results show that the observed distributions probably hold regardless of the protostar’s multiplicity, age, or the host core’s opacity. These observations indicate that the angular momentum axis of a protostar may be independent of the large-scale structure. We discuss the significance of independent protostellar rotation axes in the general picture of filament-based star formation.« less

Small, highly oriented Ru grains in intermediate layer realized through suppressing relaxation of low-angle grain boundaries for perpendicular recording media

NASA Astrophysics Data System (ADS)

Itagaki, Norikazu; Saito, Shin; Takahashi, Migaku

2009-04-01

Through analyzing the growth mechanism of the Ru layer in a nonmagnetic intermediate layer (NMIL) for perpendicular magnetic recording media, a concept for the NMIL is proposed in order to realize a recording layer of small, highly c-plane oriented grains with no intergranular exchange coupling. It was found that (1) fast Fourier transform analysis of plan-view transmission electron microscopy lattice images of Ru layers revealed that hexagonal close packed Ru grains in a c-plane oriented film readily coalesce with each other due to the disappearance of low-angle tilt boundaries. (2) A promising candidate for a NMIL consists of three individual epitaxially grown functional layers: a large-grain seed layer with a highly oriented sheet texture, a first interlayer of small grains, and a second interlayer of nonmagnetic grains isolated by a segregated oxide. (3) The Ru-SiO2/Ru/Mg NMIL based on the proposed concept exhibited small (diameter: 4.8 nm) Ru grains while retaining a narrow orientation distribution of 4.1°.

Immersion transmission ellipsometry (ITE) for the determination of orientation gradients in photoalignment layers

NASA Astrophysics Data System (ADS)

Jung, C. C.; Stumpe, J.

2014-09-01

The capability of the method of immersion transmission ellipsometry (ITE) (Jung et al. Int Patent WO, 2004/109260) to not only determine three-dimensional refractive indices in anisotropic thin films (which was already possible in the past), but even their gradients along the z-direction (perpendicular to the film plane) is investigated in this paper. It is shown that the determination of orientation gradients in deep-sub-μm films becomes possible by applying ITE in combination with reflection ellipsometry. The technique is supplemented by atomic force microscopy for measuring the film thickness. For a photo-oriented thin film, no gradient was found, as expected. For a photo-oriented film, which was subsequently annealed in a nematic liquid crystalline phase, an order was found similar to the one applied in vertically aligned nematic displays, with a tilt angle varying along the z-direction. For fresh films, gradients were only detected for the refractive index perpendicular to the film plane, as expected.

Orientation-specific responses to sustained uniaxial stretching in focal adhesion growth and turnover

PubMed Central

Chen, Yun; Pasapera, Ana M.; Koretsky, Alan P.; Waterman, Clare M.

2013-01-01

Cells are mechanosensitive to extracellular matrix (ECM) deformation, which can be caused by muscle contraction or changes in hydrostatic pressure. Focal adhesions (FAs) mediate the linkage between the cell and the ECM and initiate mechanically stimulated signaling events. We developed a stretching apparatus in which cells grown on fibronectin-coated elastic substrates can be stretched and imaged live to study how FAs dynamically respond to ECM deformation. Human bone osteosarcoma epithelial cell line U2OS was transfected with GFP-paxillin as an FA marker and subjected to sustained uniaxial stretching. Two responses at different timescales were observed: rapid FA growth within seconds after stretching, and delayed FA disassembly and loss of cell polarity that occurred over tens of minutes. Rapid FA growth occurred in all cells; however, delayed responses to stretch occurred in an orientation-specific manner, specifically in cells with their long axes perpendicular to the stretching direction, but not in cells with their long axes parallel to stretch. Pharmacological treatments demonstrated that FA kinase (FAK) promotes but Src inhibits rapid FA growth, whereas FAK, Src, and calpain 2 all contribute to delayed FA disassembly and loss of polarity in cells perpendicular to stretching. Immunostaining for phospho-FAK after stretching revealed that FAK activation was maximal at 5 s after stretching, specifically in FAs oriented perpendicular to stretch. We hypothesize that orientation-specific activation of strain/stress-sensitive proteins in FAs upstream to FAK and Src promote orientation-specific responses in FA growth and disassembly that mediate polarity rearrangement in response to sustained stretch. PMID:23754369

Choice of Grating Orientation for Evaluation of Peripheral Vision

PubMed Central

Venkataraman, Abinaya Priya; Winter, Simon; Rosén, Robert; Lundström, Linda

2016-01-01

ABSTRACT Purpose Peripheral resolution acuity depends on the orientation of the stimuli. However, it is uncertain if such a meridional effect also exists for peripheral detection tasks because they are affected by optical errors. Knowledge of the quantitative differences in acuity for different grating orientations is crucial for choosing the appropriate stimuli for evaluations of peripheral resolution and detection tasks. We assessed resolution and detection thresholds for different grating orientations in the peripheral visual field. Methods Resolution and detection thresholds were evaluated for gratings of four different orientations in eight different visual field meridians in the 20-deg visual field in white light. Detection measurements in monochromatic light (543 nm; bandwidth, 10 nm) were also performed to evaluate the effects of chromatic aberration on the meridional effect. A combination of trial lenses and adaptive optics system was used to correct the monochromatic lower- and higher-order aberrations. Results For both resolution and detection tasks, gratings parallel to the visual field meridian had better threshold compared with the perpendicular gratings, whereas the two oblique gratings had similar thresholds. The parallel and perpendicular grating acuity differences for resolution and detection tasks were 0.16 logMAR and 0.11 logMAD, respectively. Elimination of chromatic errors did not affect the meridional preference in detection acuity. Conclusions Similar to peripheral resolution, detection also shows a meridional effect that appears to have a neural origin. The threshold difference seen for parallel and perpendicular gratings suggests the use of two oblique gratings as stimuli in alternative forced-choice procedures for peripheral vision evaluation to reduce measurement variation. PMID:26889822

Choice of Grating Orientation for Evaluation of Peripheral Vision.

PubMed

Venkataraman, Abinaya Priya; Winter, Simon; Rosén, Robert; Lundström, Linda

2016-06-01

Peripheral resolution acuity depends on the orientation of the stimuli. However, it is uncertain if such a meridional effect also exists for peripheral detection tasks because they are affected by optical errors. Knowledge of the quantitative differences in acuity for different grating orientations is crucial for choosing the appropriate stimuli for evaluations of peripheral resolution and detection tasks. We assessed resolution and detection thresholds for different grating orientations in the peripheral visual field. Resolution and detection thresholds were evaluated for gratings of four different orientations in eight different visual field meridians in the 20-deg visual field in white light. Detection measurements in monochromatic light (543 nm; bandwidth, 10 nm) were also performed to evaluate the effects of chromatic aberration on the meridional effect. A combination of trial lenses and adaptive optics system was used to correct the monochromatic lower- and higher-order aberrations. For both resolution and detection tasks, gratings parallel to the visual field meridian had better threshold compared with the perpendicular gratings, whereas the two oblique gratings had similar thresholds. The parallel and perpendicular grating acuity differences for resolution and detection tasks were 0.16 logMAR and 0.11 logMAD, respectively. Elimination of chromatic errors did not affect the meridional preference in detection acuity. Similar to peripheral resolution, detection also shows a meridional effect that appears to have a neural origin. The threshold difference seen for parallel and perpendicular gratings suggests the use of two oblique gratings as stimuli in alternative forced-choice procedures for peripheral vision evaluation to reduce measurement variation.

Direct Observation on Spin-Coating Process of PS- b -P2VP Thin Films

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

Ogawa, Hiroki; Takenaka, Mikihito; Miyazaki, Tsukasa

We studied the structural development of symmetric poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymers during spin-coating using in situ grazing incidence small angle X-ray scattering (GISAXS) measurements. During the spin-coating process, after the formation of the micelles in dilute solution, the selective solvent induced two kinds of the morphological transition. Firstly, the disordered spherical micelles were transformed into a BCC lattice of spheres of which the (110) plane was oriented perpendicularly to the substrate surface. Secondly, further evaporation induced a transition from spheres on the BCC lattice into cylindrical structures. The orientation of the cylinders perpendicular to the substrate surface was induced bymore » solvent convection perpendicular to the substrate, which occurs during rapid solvent evaporation. After this transition, vitrification of PS and P2VP prevented any further transition from cylinders to the more thermodynamically stable lamellar structures, as are generally observed as the bulk equilibrium state.« less

The effective magnetoelectric coefficients of polycrystalline Cr2O3 annealed in perpendicular electric and magnetic fields

NASA Astrophysics Data System (ADS)

Liu, Y. Y.; Xie, S. H.; Jin, G.; Li, J. Y.

2009-04-01

Magnetoelectric annealing is necessary to remove antiferromagnetic domains and induce macroscopic magnetoelectric effect in polycrystalline magnetoelectric materials, and in this paper, we study the effective magnetoelectric properties of perpendicularly annealed polycrystalline Cr2O3 using effective medium approximation. The effect of temperatures, grain aspect ratios, and two different types of orientation distribution function have been analyzed, and unusual material symmetry is observed when the orientation distribution function only depends on Euler angle ψ. Optimal grain aspect ratio and texture coefficient are also identified. The approach can be applied to analyze the microstructural field distribution and macroscopic properties of a wide range of magnetoelectric polycrystals.

Reorientations, relaxations, metastabilities, and multidomains of skyrmion lattices

NASA Astrophysics Data System (ADS)

Bannenberg, L. J.; Qian, F.; Dalgliesh, R. M.; Martin, N.; Chaboussant, G.; Schmidt, M.; Schlagel, D. L.; Lograsso, T. A.; Wilhelm, H.; Pappas, C.

2017-11-01

Magnetic skyrmions are nanosized topologically protected spin textures with particlelike properties. They can form lattices perpendicular to the magnetic field, and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small-angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu2OSeO3 and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history of the sample, which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Furthermore, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field.

Friction Anisotropy with Respect to Topographic Orientation

PubMed Central

Yu, Chengjiao; Wang, Q. Jane

2012-01-01

Friction characteristics with respect to surface topographic orientation were investigated using surfaces of different materials and fabricated with grooves of different scales. Scratching friction tests were conducted using a nano-indentation-scratching system with the tip motion parallel or perpendicular to the groove orientation. Similar friction anisotropy trends were observed for all the surfaces studied, which are (1) under a light load and for surfaces with narrow grooves, the tip motion parallel to the grooves offers higher friction coefficients than does that perpendicular to them, (2) otherwise, equal or lower friction coefficients are found under this motion. The influences of groove size relative to the diameter of the mating tip (as a representative asperity), surface contact stiffness, contact area, and the characteristic stiction length are discussed. The appearance of this friction anisotropy is independent of material; however, the boundary and the point of trend transition depend on material properties. PMID:23248751

Temperature dependences of the electric polarization and wave number of incommensurate structures in multiferroics

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

Pikin, S. A., E-mail: pikin@ns.crys.ras.ru

2016-05-15

It is shown that the electric polarization and wave number of incommensurate modulations, proportional to each other, increase according to the Landau law in spin multiferroic cycloids near the Néel temperature. In this case, the constant magnetization component (including the one for a conical spiral) is oriented perpendicular to the spin incommensurability wave vector. A similar temperature behavior should manifest itself for spin helicoids, the axes of which are oriented parallel to the polarization vector but their spin rotation planes are oriented perpendicular to the antiferromagnetic order plane. When the directions of axes of the magnetization helicoid and polarization vectormore » coincide, the latter is quadratic with respect to magnetization and linearly depends on temperature, whereas the incommensurate-modulation wave number barely depends on temperature. Structural distortions of unit cells for multiferroics of different types determine their axial behavior.« less

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

Bannenberg, L. J.; Qian, F.; Dalgliesh, R. M.

Magnetic skyrmions are nanosized topologically protected spin textures with particlelike properties. They can form lattices perpendicular to the magnetic field, and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small-angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu 2OSeO 3 and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history ofmore » the sample, which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Moreover, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field.« less

The formation flare loops by magnetic reconnection and chromospheric ablation

NASA Technical Reports Server (NTRS)

Forbes, T. G.; Malherbe, J. M.; Priest, E. R.

1989-01-01

Noncoplanar compressible reconnection theory is combined here with simple scaling arguments for ablation and radiative cooling to predict average properties of hot and cool flare loops as a function of the coronal vector magnetic field. For a coronal field strength of 100 G, the temperature of the hot flare loops decreases from 1.2 x 10 to the 7th K to 4.0 x 10 to the 6th K as the component of the coronal magnetic field perpendicular to the plane of the loops increases from 0 percent to 86 percent of the total field. When the perpendicular component exceeds 86 percent of the total field or when the altitude of the reconnection site exceeds 10 to the 6th km, flare loops no longer occur. Shock-enhanced radiative cooling triggers the formation of cool H-alpha flare loops with predicted densities of roughly 10 to the 13th/cu cm, and a small gap of roughly 1000 km is predicted to exist between the footpoints of the cool flare loops and the inner edges of the flare ribbons.

Imaging Borrelly

USGS Publications Warehouse

Soderblom, L.A.; Boice, D.C.; Britt, D.T.; Brown, R.H.; Buratti, B.J.; Kirk, R.L.; Lee, M.; Nelson, R.M.; Oberst, J.; Sandel, B.R.; Stern, S.A.; Thomas, N.; Yelle, R.V.

2004-01-01

The nucleus, coma, and dust jets of short-period Comet 19P/Borrelly were imaged from the Deep Space 1 spacecraft during its close flyby in September 2001. A prominent jet dominated the near-nucleus coma and emanated roughly normal to the long axis of nucleus from a broad central cavity. We show it to have remained fixed in position for more than 34 hr, much longer than the 26-hr rotation period. This confirms earlier suggestions that it is co-aligned with the rotation axis. From a combination of fitting the nucleus light curve from approach images and the nucleus' orientation from stereo images at encounter, we conclude that the sense of rotation is right-handed around the main jet vector. The inferred rotation pole is approximately perpendicular to the long axis of the nucleus, consistent with a simple rotational state. Lacking an existing IAU comet-specific convention but applying a convention provisionally adopted for asteroids, we label this the north pole. This places the sub-solar latitude at ???60?? N at the time of the perihelion with the north pole in constant sunlight and thus receiving maximum average insolation. ?? 2003 Elsevier Inc. All rights reserved.

Effect of nanostructures orientation on electroosmotic flow in a microfluidic channel

NASA Astrophysics Data System (ADS)

Eng Lim, An; Lim, Chun Yee; Cheong Lam, Yee; Taboryski, Rafael; Rui Wang, Shu

2017-06-01

Electroosmotic flow (EOF) is an electric-field-induced fluid flow that has numerous micro-/nanofluidic applications, ranging from pumping to chemical and biomedical analyses. Nanoscale networks/structures are often integrated in microchannels for a broad range of applications, such as electrophoretic separation of biomolecules, high reaction efficiency catalytic microreactors, and enhancement of heat transfer and sensing. Their introduction has been known to reduce EOF. Hitherto, a proper study on the effect of nanostructures orientation on EOF in a microfluidic channel is yet to be carried out. In this investigation, we present a novel fabrication method for nanostructure designs that possess maximum orientation difference, i.e. parallel versus perpendicular indented nanolines, to examine the effect of nanostructures orientation on EOF. It consists of four phases: fabrication of silicon master, creation of mold insert via electroplating, injection molding with cyclic olefin copolymer, and thermal bonding and integration of practical inlet/outlet ports. The effect of nanostructures orientation on EOF was studied experimentally by current monitoring method. The experimental results show that nanolines which are perpendicular to the microchannel reduce the EOF velocity significantly (approximately 20%). This flow velocity reduction is due to the distortion of local electric field by the perpendicular nanolines at the nanostructured surface as demonstrated by finite element simulation. In contrast, nanolines which are parallel to the microchannel have no effect on EOF, as it can be deduced that the parallel nanolines do not distort the local electric field. The outcomes of this investigation contribute to the precise control of EOF in lab-on-chip devices, and fundamental understanding of EOF in devices which utilize nanostructured surfaces for chemical and biological analyses.

Roughness-induced generation of crossflow vortices in three-dimensional boundary layers

NASA Technical Reports Server (NTRS)

Choudhari, Meelan

1993-01-01

The receptivity theory of Goldstein and Ruban is extended within the nonasymptotic (quasi-parallel) framework of Zavol'skii et al to predict the roughness-induced generation of stationary and nonstationary instability waves in three-dimensional, incompressible boundary layers. The influence of acoustic-wave orientation, as well as that of different types of roughness geometries, including isolated roughness elements, periodic arrays, and two-dimensional lattices of compact roughness shapes, as well as random, but spatially homogeneous roughness distributions, is examined. The parametric study for the Falkner-Skan-Cooke family of boundary layers supports our earlier conjecture that the initial amplitudes of roughness-induced stationary vortices are likely to be significantly larger than the amplitudes of similarly induced nonstationary vortices in the presence of acoustic disturbances in the free stream. Maximum unsteady receptivity occurs when the acoustic velocity fluctuation is aligned with the wavenumber vector of the unsteady vortex mode. On the other hand, roughness arrays that are oriented somewhere close to the group velocity direction are likely to produce higher instability amplitudes. Limitations of the nonasymptotic theory are discussed, and future work is suggested.

Generalizing roughness: experiments with flow-oriented roughness

NASA Astrophysics Data System (ADS)

Trevisani, Sebastiano

2015-04-01

Surface texture analysis applied to High Resolution Digital Terrain Models (HRDTMs) improves the capability to characterize fine-scale morphology and permits the derivation of useful morphometric indexes. An important indicator to be taken into account in surface texture analysis is surface roughness, which can have a discriminant role in the detection of different geomorphic processes and factors. The evaluation of surface roughness is generally performed considering it as an isotropic surface parameter (e.g., Cavalli, 2008; Grohmann, 2011). However, surface texture has often an anisotropic character, which means that surface roughness could change according to the considered direction. In some applications, for example involving surface flow processes, the anisotropy of roughness should be taken into account (e.g., Trevisani, 2012; Smith, 2014). Accordingly, we test the application of a flow-oriented directional measure of roughness, computed considering surface gravity-driven flow. For the calculation of flow-oriented roughness we use both classical variogram-based roughness (e.g., Herzfeld,1996; Atkinson, 2000) as well as an ad-hoc developed robust modification of variogram (i.e. MAD, Trevisani, 2014). The presented approach, based on a D8 algorithm, shows the potential impact of considering directionality in the calculation of roughness indexes. The use of flow-oriented roughness could improve the definition of effective proxies of impedance to flow. Preliminary results on the integration of directional roughness operators with morphometric-based models, are promising and can be extended to more complex approaches. Atkinson, P.M., Lewis, P., 2000. Geostatistical classification for remote sensing: an introduction. Computers & Geosciences 26, 361-371. Cavalli, M. & Marchi, L. 2008, "Characterization of the surface morphology of an alpine alluvial fan using airborne LiDAR", Natural Hazards and Earth System Science, vol. 8, no. 2, pp. 323-333. Grohmann, C.H., Smith, M.J., Riccomini, C., 2011. Multiscale Analysis of Topographic Surface Roughness in the Midland Valley, Scotland. IEEE Transactions on Geoscience and Remote Sensing 49, 1220-1213. Herzfeld, U.C., Higginson, C.A., 1996. Automated geostatistical seafloor classification - Principles, parameters, feature vectors, and discrimination criteria. Computers and Geosciences, 22 (1), pp. 35-52. Smith, M.W. 2014, "Roughness in the Earth Sciences", Earth-Science Reviews, vol. 136, pp. 202-225. Trevisani, S., Cavalli, M. & Marchi, L. 2012, "Surface texture analysis of a high-resolution DTM: Interpreting an alpine basin", Geomorphology, vol. 161-162, pp. 26-39. Trevisani S., Rocca M., 2014. Geomorphometric analysis of fine-scale morphology for extensive areas: a new surface-texture operator. Geophysical Research Abstracts, Vol. 16, EGU2014-5612, 2014. EGU General Assembly 2014.

Effect of Aerogel Anisotropy in Superfluid 3He-A

NASA Astrophysics Data System (ADS)

Zimmerman, A. M.; Li, J. I. A.; Pollanen, J.; Collett, C. A.; Gannon, W. J.; Halperin, W. P.

2014-03-01

Two theories have been advanced to describe the effects of anisotropic impurity introduced by stretched silica aerogel on the orientation of the orbital angular momentum l& circ; in superfluid 3He-A. These theories disagree on whether the anisotropy will orient l& circ; perpendicular[2] or parallel[3] to the strain axis. In order to examine this question we have produced and characterized a homogeneous aerogel sample with uniaxial anisotropy introduced during growth, corresponding to stretching of the aerogel. These samples have been shown to stabilize two new chiral states;[4] the higher temperature state being the subject of the present study. Using pulsed NMR we have performed experiments on 3He-A imbibed in this sample in two orientations: strain parallel and perpendicular to the applied magnetic field. From the NMR frequency shifts as a function of tip angle and temperature, we find that the angular momentum l& circ; is oriented along the strain axis, providing evidence for the theory advanced by Sauls. This work was supported by the National Science Foundation, DMR-1103625.

Atomistic Modeling of Thermal Conductivity of Epoxy Nanotube Composites

NASA Astrophysics Data System (ADS)

Fasanella, Nicholas A.; Sundararaghavan, Veera

2016-05-01

The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for epoxy/single wall carbon nanotube (SWNT) nanocomposites. An epoxy network of DGEBA-DDS was built using the `dendrimer' growth approach, and conductivity was computed by taking into account long-range Coulombic forces via a k-space approach. Thermal conductivity was calculated in the direction perpendicular to, and along the SWNT axis for functionalized and pristine SWNT/epoxy nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. The thermal conductivity of the long, pristine SWNT/epoxy system is equivalent to that of an isolated SWNT along its axis, but there was a 27% reduction perpendicular to the nanotube axis. The functionalized, long SWNT/epoxy system had a very large increase in thermal conductivity along the nanotube axis (~700%), as well as the directions perpendicular to the nanotube (64%). The discontinuous nanotubes displayed an increased thermal conductivity along the SWNT axis compared to neat epoxy (103-115% for the pristine SWNT/epoxy, and 91-103% for functionalized SWNT/epoxy system). The functionalized system also showed a 42% improvement perpendicular to the nanotube, while the pristine SWNT/epoxy system had no improvement over epoxy. The thermal conductivity tensor is averaged over all possible orientations to see the effects of randomly orientated nanotubes, and allow for experimental comparison. Excellent agreement is seen for the discontinuous, pristine SWNT/epoxy nanocomposite. These simulations demonstrate there exists a threshold of the SWNT length where the best improvement for a composite system with randomly oriented nanotubes would transition from pristine SWNTs to functionalized SWNTs.

The dynamics and control of large flexible space structures, 3. Part A: Shape and orientation control of a platform in orbit using point actuators

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Reddy, A. S. S. R.; Krishna, R.; James, P. K.

1980-01-01

The dynamics, attitude, and shape control of a large thin flexible square platform in orbit are studied. Attitude and shape control are assumed to result from actuators placed perpendicular to the main surface and one edge and their effect on the rigid body and elastic modes is modelled to first order. The equations of motion are linearized about three different nominal orientations: (1) the platform following the local vertical with its major surface perpendicular to the orbital plane; (2) the platform following the local horizontal with its major surface normal to the local vertical; and (3) the platform following the local vertical with its major surface perpendicular to the orbit normal. The stability of the uncontrolled system is investigated analytically. Once controllability is established for a set of actuator locations, control law development is based on decoupling, pole placement, and linear optimal control theory. Frequencies and elastic modal shape functions are obtained using a finite element computer algorithm, two different approximate analytical methods, and the results of the three methods compared.

Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

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

Pan, A.; Dias, A.; Gomez-Aranzadi, M.

2014-05-07

The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observedmore » with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.« less

The quasiperpendicular environment of large magnetic pulses in Earth's quasiparallel foreshock - ISEE 1 and 2 observations

NASA Technical Reports Server (NTRS)

Greenstadt, E. W.; Moses, S. L.; Coroniti, F. V.; Farris, M. H.; Russell, C. T.

1993-01-01

ULF waves in Earth's foreshock cause the instantaneous angle theta-B(n) between the upstream magnetic field and the shock normal to deviate from its average value. Close to the quasi-parallel (Q-parallel) shock, the transverse components of the waves become so large that the orientation of the field to the normal becomes quasi-perpendicular (Q-perpendicular) during applicable phases of each wave cycle. Large upstream pulses of B were observed completely enclosed in excursions of Theta-B(n) into the Q-perpendicular range. A recent numerical simulation included Theta-B(n) among the parameters examined in Q-parallel runs, and described a similar coincidence as intrinsic to a stage in development of the reformation process of such shocks. Thus, the natural environment of the Q-perpendicular section of Earth's bow shock seems to include an identifiable class of enlarged magnetic pulses for which local Q-perpendicular geometry is a necessary association.

Joint properties of a tool machining process to guarantee fluid-proof abilities

NASA Astrophysics Data System (ADS)

Bataille, C.; Deltombe, R.; Jourani, A.; Bigerelle, M.

2017-12-01

This study addressed the impact of rod surface topography in contact with reciprocating seals. Rods were tooled with and without centreless grinding. All rods tooled with centreless grinding were fluid-proof, in contrast to rods tooled without centreless grinding that either had leaks or were fluid-proof. A method was developed to analyse the machining signature, and the software Mesrug™ was used in order to discriminate roughness parameters that can be used to characterize the sealing functionality. According to this surface roughness analysis, a fluid-proof rod tooled without centreless grinding presents aperiodic large plateaus, and the relevant roughness parameter for characterizing the sealing functionality is the density of summits S DS. Increasing the density of summits counteracts leakage, which may be because motif decomposition integrates three topographical components: circularity (perpendicular long-wave roughness), longitudinal waviness, and roughness thanks to the Wolf pruning algorithm. A 3D analytical contact model was applied to analyse the contact area of each type of sample with the seal surface. This model provides a leakage probability, and the results were consistent with the interpretation of the topographical analysis.

Influence law of structural characteristics on the surface roughness of a magnetorheological-finished KDP crystal.

PubMed

Chen, Shaoshan; Li, Shengyi; Hu, Hao; Li, Qi; Tie, Guipeng

2014-11-01

A new nonaqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing potassium dihydrogen phosphate (KDP) crystal due to its low hardness, high brittleness, temperature sensitivity, and water solubility. This paper researches the influence of structural characteristics on the surface roughness of MRF-finished KDP crystal. The material removal by dissolution is uniform layer by layer when the polishing parameters are stable. The angle between the direction of the polishing wheel's linear velocity and the initial turning lines will affect the surface roughness. If the direction is perpendicular to the initial turning lines, the polishing can remove the lines. If the direction is parallel to the initial turning lines, the polishing can achieve better surface roughness. The structural characteristic of KDP crystal is related to its internal chemical bonds due to its anisotropy. During the MRF finishing process, surface roughness will be improved if the structural characteristics of the KDP crystal are the same on both sides of the wheel. The processing results of (001) plane crystal show we can get the best surface roughness (RMS of 0.809 nm) if the directions of cutting and MRF polishing are along the (110) direction.

[Problems of using a thermocouple for measurements of skin temperature rise during the exposure to millimeter waves].

PubMed

Alekseev, S I; Ziskin, M S; Fesenko, E E

2011-01-01

The possibility of using thermocouples for the artifact-free measurements of skin temperature during millimeter wave exposure was studied. The distributions of the specific absorption rate (SAR) in the human skin were calculated for different orientations of the thermocouple relative to the E-field of exposure. It was shown that, at the parallel orientation of a thermocouple relative to the E-field, SAR significantly increased at the tip of the thermocouple. This can result in an overheating of the thermocouple. At the perpendicular orientation of a thermocouple, the distortions of the SAR were insignificant. The data obtained confirm that the skin temperature can be measured with a thermocouple during exposure under the condition that the thermocouple is located perpendicular to the E-vector of the electromagnetic field. For the accurate determination of SAR from the rate of the initial temperature rise, it is necessary to fit the temperature kinetics measured with the thermocouple to the solution of the bio-heat transfer equation.

Reorientations, relaxations, metastabilities, and multidomains of skyrmion lattices

DOE PAGES

Bannenberg, L. J.; Qian, F.; Dalgliesh, R. M.; ...

2017-11-13

Magnetic skyrmions are nanosized topologically protected spin textures with particlelike properties. They can form lattices perpendicular to the magnetic field, and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small-angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu 2OSeO 3 and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history ofmore » the sample, which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Moreover, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field.« less

Laser Peening and Shot Peening Effects on Fatigue Life and Surface Roughness of Friction Stir Welded 7075-T7351 Aluminum

NASA Technical Reports Server (NTRS)

Hatamleh, Omar; Lyons, Jed; Forman, Royce

2006-01-01

The effects of laser peening, shot peening, and a combination of both on the fatigue life of Friction Stir Welds (FSW) was investigated. The fatigue samples consisted of dog bone specimens and the loading was applied in a direction perpendicular to the weld direction. Several laser peening conditions with different intensities, durations, and peening order were tested to obtain the optimum peening parameters. The surface roughness resulting from various peening techniques was assessed and characterized. The results indicate a significant increase in fatigue life using laser peening compared to shot peened versus their native welded specimens.

Feasibility study on the use of liquid crystal/dye cells for digital signage

NASA Astrophysics Data System (ADS)

Itaya, Shunsuke; Azumi, Nada Dianah B. M.; Ohta, Masamichi; Ozawa, Shintaro; Fujieda, Ichiro

2016-03-01

Elongated dye molecules orient themselves with surrounding liquid crystal molecules. We propose to incorporate such a guest-host cell in a screen of a projection display. This configuration might be applied for digital signage to be installed on building walls. Dual-mode operation is realized by the bias applied to the cell. In display-mode, the dye molecules are oriented in parallel to the substrate of the cell. When excited by ultra-violet light, photoluminescence (PL) is generated. Because it is mostly perpendicular to the long axis of the molecule, it exits the cell efficiently. In powerharvesting mode, they are oriented vertically. The PL generated by ambient light is directed to edge surfaces where solar cells are mounted. In experiment, we fabricated a cell with commonly-available materials (coumarin 6 and a nematic liquid crystal). Anti-parallel alignment condition was adopted. We recorded PL spectra from the cell for the two excitation conditions. First, the center of the cell was irradiated by a 1.69mW blue laser beam. Second, the whole cell was uniformly exposed to the light from a fluorescent lamp at illuminance of 800lx. From the measured spectra for these cases, the contrast of luminance is calculated to be 3.2 ×105 . This factor is improved to 5 7.5×105 by attaching a polarizer sheet on the cell surface. The optical power reaching its edge surfaces is measured and it roughly agrees with the prediction by a simple model neglecting self-absorption. Development of phosphor materials with a large Stokes shift is desired to boost performance of the proposed system.

Rinne test: does the tuning fork position affect the sound amplitude at the ear?

PubMed

Butskiy, Oleksandr; Ng, Denny; Hodgson, Murray; Nunez, Desmond A

2016-03-24

Guidelines and text-book descriptions of the Rinne test advise orienting the tuning fork tines in parallel with the longitudinal axis of the external auditory canal (EAC), presumably to maximise the amplitude of the air conducted sound signal at the ear. Whether the orientation of the tuning fork tines affects the amplitude of the sound signal at the ear in clinical practice has not been previously reported. The present study had two goals: determine if (1) there is clinician variability in tuning fork placement when presenting the air-conduction stimulus during the Rinne test; (2) the orientation of the tuning fork tines, parallel versus perpendicular to the EAC, affects the sound amplitude at the ear. To assess the variability in performing the Rinne test, the Canadian Society of Otolaryngology - Head and Neck Surgery members were surveyed. The amplitudes of the sound delivered to the tympanic membrane with the activated tuning fork tines held in parallel, and perpendicular to, the longitudinal axis of the EAC were measured using a Knowles Electronics Mannequin for Acoustic Research (KEMAR) with the microphone of a sound level meter inserted in the pinna insert. 47.4 and 44.8% of 116 survey responders reported placing the fork parallel and perpendicular to the EAC respectively. The sound intensity (sound-pressure level) recorded at the tympanic membrane with the 512 Hz tuning fork tines in parallel with as opposed to perpendicular to the EAC was louder by 2.5 dB (95% CI: 1.35, 3.65 dB; p < 0.0001) for the fundamental frequency (512 Hz), and by 4.94 dB (95% CI: 3.10, 6.78 dB; p < 0.0001) and 3.70 dB (95% CI: 1.62, 5.78 dB; p = .001) for the two harmonic (non-fundamental) frequencies (1 and 3.15 kHz), respectively. The 256 Hz tuning fork in parallel with the EAC as opposed to perpendicular to was louder by 0.83 dB (95% CI: -0.26, 1.93 dB; p = 0.14) for the fundamental frequency (256 Hz), and by 4.28 dB (95% CI: 2.65, 5.90 dB; p < 0.001) and 1.93 dB (95% CI: 0.26, 3.61 dB; p = .02) for the two harmonic frequencies (500 and 4 kHz) respectively. Clinicians vary in their orientation of the tuning fork tines in relation to the EAC when performing the Rinne test. Placement of the tuning fork tines in parallel as opposed to perpendicular to the EAC results in a higher sound amplitude at the level of the tympanic membrane.

Proton beam deflection in MRI fields: Implications for MRI-guided proton therapy.

PubMed

Oborn, B M; Dowdell, S; Metcalfe, P E; Crozier, S; Mohan, R; Keall, P J

2015-05-01

This paper investigates, via magnetic modeling and Monte Carlo simulation, the ability to deliver proton beams to the treatment zone inside a split-bore MRI-guided proton therapy system. Field maps from a split-bore 1 T MRI-Linac system are used as input to geant4 Monte Carlo simulations which model the trajectory of proton beams during their paths to the isocenter of the treatment area. Both inline (along the MRI bore) and perpendicular (through the split-bore gap) orientations are simulated. Monoenergetic parallel and diverging beams of energy 90, 195, and 300 MeV starting from 1.5 and 5 m above isocenter are modeled. A phase space file detailing a 2D calibration pattern is used to set the particle starting positions, and their spatial location as they cross isocenter is recorded. No beam scattering, collimation, or modulation of the proton beams is modeled. In the inline orientation, the radial symmetry of the solenoidal style fringe field acts to rotate the protons around the beam's central axis. For protons starting at 1.5 m from isocenter, this rotation is 19° (90 MeV) and 9.8° (300 MeV). A minor focusing toward the beam's central axis is also seen, but only significant, i.e., 2 mm shift at 150 mm off-axis, for 90 MeV protons. For the perpendicular orientation, the main MRI field and near fringe field act as the strongest to deflect the protons in a consistent direction. When starting from 1.5 m above isocenter shifts of 135 mm (90 MeV) and 65 mm (300 MeV) were observed. Further to this, off-axis protons are slightly deflected toward or away from the central axis in the direction perpendicular to the main deflection direction. This leads to a distortion of the phase space pattern, not just a shift. This distortion increases from zero at the central axis to 10 mm (90 MeV) and 5 mm (300 MeV) for a proton 150 mm off-axis. In both orientations, there is a small but subtle difference in the deflection and distortion pattern between protons fired parallel to the beam axis and those fired from a point source. This is indicative of the 3D spatially variant nature of the MRI fringe field. For the first time, accurate magnetic and Monte Carlo modeling have been used to assess the transport of generic proton beams toward a 1 T split-bore MRI. Significant rotation is observed in the inline orientation, while more complex deflection and distortion are seen in the perpendicular orientation. The results of this study suggest that due to the complexity and energy-dependent nature of the magnetic deflection and distortion, the pencil beam scanning method will be the only choice for delivering a therapeutic proton beam inside a potential MRI-guided proton therapy system in either the inline or perpendicular orientation. Further to this, significant correction strategies will be required to account for the MRI fringe fields.

Preliminary observations of the effect of solutal convection on crystal morphology

NASA Technical Reports Server (NTRS)

Broom, M. Beth H.; Witherow, William K.; Snyder, Robert S.; Carter, Daniel C.

1988-01-01

Studies to examine the effect of solutal convection on crystal morphology using sucrose as a model system were initiated. Aspect ratios, defined as the width of the 100-plane-oriented face over the width of the 001-plane-oriented face, were determined for oriented crystals which were grown with either the 001-oriented or the 100-oriented face perpendicular to the convective flow. The dependence of the crystal morphology on orientation is much greater for crystals grown with one face occluded than for crystals grown suspended in solution. Many factors appear to interact in a complex fashion to influence crystal morphology.

Solvothermal Vapor Annealing of Lamellar Poly(styrene)-block-poly(d,l-lactide) Block Copolymer Thin Films for Directed Self-Assembly Application.

PubMed

Cummins, Cian; Mokarian-Tabari, Parvaneh; Andreazza, Pascal; Sinturel, Christophe; Morris, Michael A

2016-03-01

Solvothermal vapor annealing (STVA) was employed to induce microphase separation in a lamellar forming block copolymer (BCP) thin film containing a readily degradable block. Directed self-assembly of poly(styrene)-block-poly(d,l-lactide) (PS-b-PLA) BCP films using topographically patterned silicon nitride was demonstrated with alignment over macroscopic areas. Interestingly, we observed lamellar patterns aligned parallel as well as perpendicular (perpendicular microdomains to substrate in both cases) to the topography of the graphoepitaxial guiding patterns. PS-b-PLA BCP microphase separated with a high degree of order in an atmosphere of tetrahydrofuran (THF) at an elevated vapor pressure (at approximately 40-60 °C). Grazing incidence small-angle X-ray scattering (GISAXS) measurements of PS-b-PLA films reveal the through-film uniformity of perpendicular microdomains after STVA. Perpendicular lamellar orientation was observed on both hydrophilic and relatively hydrophobic surfaces with a domain spacing (L0) of ∼32.5 nm. The rapid removal of the PLA microdomains is demonstrated using a mild basic solution for the development of a well-defined PS mask template. GISAXS data reveal the through-film uniformity is retained following wet etching. The experimental results in this article demonstrate highly oriented PS-b-PLA microdomains after a short annealing period and facile PLA removal to form porous on-chip etch masks for nanolithography application.

SU-E-T-133: Dosimetric Impact of Scan Orientation Relative to Target Motion During Spot Scanning Proton Therapy

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

Stoker, J; Summers, P; Li, X

2014-06-01

Purpose: This study seeks to evaluate the dosimetric effects of intra-fraction motion during spot scanning proton beam therapy as a function of beam-scan orientation and target motion amplitude. Method: Multiple 4DCT scans were collected of a dynamic anthropomorphic phantom mimicking respiration amplitudes of 0 (static), 0.5, 1.0, and 1.5 cm. A spot-scanning treatment plan was developed on the maximum intensity projection image set, using an inverse-planning approach. Dynamic phantom motion was continuous throughout treatment plan delivery.The target nodule was designed to accommodate film and thermoluminescent dosimeters (TLD). Film and TLDs were uniquely labeled by location within the target. The phantommore » was localized on the treatment table using the clinically available orthogonal kV on-board imaging device. Film inserts provided data for dose uniformity; TLDs provided a 3% precision estimate of absolute dose. An inhouse script was developed to modify the delivery order of the beam spots, to orient the scanning direction parallel or perpendicular to target motion.TLD detector characterization and analysis was performed by the Imaging and Radiation Oncology Core group (IROC)-Houston. Film inserts, exhibiting a spatial resolution of 1mm, were analyzed to determine dose homogeneity within the radiation target. Results: Parallel scanning and target motions exhibited reduced target dose heterogeneity, relative to perpendicular scanning orientation. The average percent deviation in absolute dose for the motion deliveries relative to the static delivery was 4.9±1.1% for parallel scanning, and 11.7±3.5% (p<<0.05) for perpendicularly oriented scanning. Individual delivery dose deviations were not necessarily correlated to amplitude of motion for either scan orientation. Conclusions: Results demonstrate a quantifiable difference in dose heterogeneity as a function of scan orientation, more so than target amplitude. Comparison to the analyzed planar dose of a single field hint that multiple-field delivery alters intra-fraction beam-target motion synchronization and may mitigate heterogeneity, though further study is warranted.« less

Stress rotation along pre-Cenozoic basement structures

NASA Astrophysics Data System (ADS)

Reiter, K.; Heidbach, O.; Henk, A.

2017-12-01

The in-situ stress state of the Earth's crust is under investigation since decades for both, scientific and economic purposes. Several methods have been established to indicate the contemporary orientation of the maximum compressive horizontal stress (SHmax). It is assumed that the same forces that drive plate motion are the first order stress sources and one could presume that SHmax is always parallel to plate motion, which is the case for some regions. However, deviations from this general trend occur in many regions. Therefore, second and third order sources of stress have been identified that potentially cause regional and local stress rotation with respect to the long wave-length trend imposed by plate tectonic forces. One group of such subordinate stress sources are lateral heterogeneities based on structures, petrothermal or petrophysical properties. The World Stress Map (WSM) project compiles systematically data records of the present day SHmax orientation. The increasing amount of stress orientation data allows to investigate areas with consistent stress rotation, divergent to the regional stress pattern. In our work we analyse the stress pattern variability and its causes beneath Germany. In the Molasse Basin in the Alpine foreland the SHmax orientation is perpendicular to the Alpine front as a consequence of gravitational potential energy of the orogen. SHmax is oriented in N-S direction in the central Alpine foreland and within the North German Basin. Between both, within the Mid-German Crystalline High, SHmax is divergent oriented in SE-NW direction. Neither gravitational potential energy nor petrothermal effects can be indicated as stress source. But when comparing the stress pattern with the Variscan basement structures it is obvious that SHmax is perpendicular oriented to this Palaeozoic basement structures. Therefore, petrophysical heterogeneities can be expected as reason for the observed stress rotation. Two assumptions can be made for the Mid-German Crystalline High based on this presumption. 1. The magnitude of SHmax and the minimum horizontal stress (Shmin) in the region is close by, allowing local stress rotation. 2. The stiffness contrast perpendicular to the strike of the Variscan basement structures is large enough as stress source to cause significant rotation of the stress pattern.

Experimental investigation of the effect of the laser beam polarization state on the quality of steel sheet cutting

NASA Astrophysics Data System (ADS)

Golyshev, A. A.; Orishich, A. M.; Shulyatyev, V. B.

2017-10-01

The paper presents the results of experimental investigation of the effect of the beam polarization on the quality of the oxygen-assisted laser cutting of steel by a CO2-laser. Under consideration is the effect of the laser cutting parameters by the beam with the linear polarization on the cut surface roughness. It is founded that the minimal roughness is reached when the electric field vector is perpendicular to the cutting speed vector. It is concluded that the absorbed power distribution imposes the essential influence on the surface quality, and that the radiation heating of side walls is important to have lower roughness. Obtained results enabled to present probable reasons of the worse surface quality of the metals cut by a fiber laser than the ones cut by a CO2-laser.

Roughness influence on human blood drop spreading and splashing

NASA Astrophysics Data System (ADS)

Smith, Fiona; Buntsma, Naomi; Brutin, David

2017-11-01

The impact behaviour of complex fluid droplets is a topic that has been extensively studied but with much debate. The Bloodstain Pattern Analysis (BPA) community is encountering this scientific problem with daily practical cases since they use bloodstains as evidence in crime scene reconstruction. We aim to provide fundamental explanations in the study of blood drip stains by investigating the influence of surface roughness and wettability on the splashing limit of droplets of blood, a non-Newtonian colloidal fluid. Droplets of blood impacting perpendicularly different surfaces at different velocities were recorded. The recordings were analysed as well as the surfaces characteristics in order to find an empirical solution since we found that roughness plays a major role in the threshold of the splashing/non-splashing behaviour of blood compared to the wettability. Moreover it appears that roughness alters the deformation of the drip stains. These observations are key in characterising features of drip stains with the impacting conditions, which would answer some forensic issues.

Linear dichroism of DNA: Characterization of the orientation distribution function caused by hydrodynamic shear

DOE PAGES

Sutherland, John C.

2017-04-15

Linear dichroism provides information on the orientation of chromophores part of, or bound to, an orientable molecule such as DNA. For molecular alignment induced by hydrodynamic shear, the principal axes orthogonal to the direction of alignment are not equivalent. Thus, the magnitude of the flow-induced change in absorption for light polarized parallel to the direction of flow can be more than a factor of two greater than the corresponding change for light polarized perpendicular to both that direction and the shear axis. The ratio of the two flow-induced changes in absorption, the dichroic increment ratio, is characterized using the orthogonalmore » orientation model, which assumes that each absorbing unit is aligned parallel to one of the principal axes of the apparatus. The absorption of the alienable molecules is characterized by components parallel and perpendicular to the orientable axis of the molecule. The dichroic increment ratio indicates that for the alignment of DNA in rectangular flow cells, average alignment is not uniaxial, but for higher shear, as produced in a Couette cell, it can be. The results from the simple model are identical to tensor models for typical experimental configuration. Approaches for measuring the dichroic increment ratio with modern dichrometers are further discussed.« less

Quantitative analysis of optical properties of flowing blood using a photon-cell interactive Monte Carlo code: effects of red blood cells' orientation on light scattering.

PubMed

Sakota, Daisuke; Takatani, Setsuo

2012-05-01

Optical properties of flowing blood were analyzed using a photon-cell interactive Monte Carlo (pciMC) model with the physical properties of the flowing red blood cells (RBCs) such as cell size, shape, refractive index, distribution, and orientation as the parameters. The scattering of light by flowing blood at the He-Ne laser wavelength of 632.8 nm was significantly affected by the shear rate. The light was scattered more in the direction of flow as the flow rate increased. Therefore, the light intensity transmitted forward in the direction perpendicular to flow axis decreased. The pciMC model can duplicate the changes in the photon propagation due to moving RBCs with various orientations. The resulting RBC's orientation that best simulated the experimental results was with their long axis perpendicular to the direction of blood flow. Moreover, the scattering probability was dependent on the orientation of the RBCs. Finally, the pciMC code was used to predict the hematocrit of flowing blood with accuracy of approximately 1.0 HCT%. The photon-cell interactive Monte Carlo (pciMC) model can provide optical properties of flowing blood and will facilitate the development of the non-invasive monitoring of blood in extra corporeal circulatory systems.

Linear dichroism of DNA: Characterization of the orientation distribution function caused by hydrodynamic shear

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

Sutherland, John C.

Linear dichroism provides information on the orientation of chromophores part of, or bound to, an orientable molecule such as DNA. For molecular alignment induced by hydrodynamic shear, the principal axes orthogonal to the direction of alignment are not equivalent. Thus, the magnitude of the flow-induced change in absorption for light polarized parallel to the direction of flow can be more than a factor of two greater than the corresponding change for light polarized perpendicular to both that direction and the shear axis. The ratio of the two flow-induced changes in absorption, the dichroic increment ratio, is characterized using the orthogonalmore » orientation model, which assumes that each absorbing unit is aligned parallel to one of the principal axes of the apparatus. The absorption of the alienable molecules is characterized by components parallel and perpendicular to the orientable axis of the molecule. The dichroic increment ratio indicates that for the alignment of DNA in rectangular flow cells, average alignment is not uniaxial, but for higher shear, as produced in a Couette cell, it can be. The results from the simple model are identical to tensor models for typical experimental configuration. Approaches for measuring the dichroic increment ratio with modern dichrometers are further discussed.« less

Linear dichroism of DNA: Characterization of the orientation distribution function caused by hydrodynamic shear.

PubMed

Sutherland, John C

2017-04-15

Linear dichroism provides information on the orientation of chromophores part of, or bound to, an orientable molecule such as DNA. For molecular alignment induced by hydrodynamic shear, the principal axes orthogonal to the direction of alignment are not equivalent. Thus, the magnitude of the flow-induced change in absorption for light polarized parallel to the direction of flow can be more than a factor of two greater than the corresponding change for light polarized perpendicular to both that direction and the shear axis. The ratio of the two flow-induced changes in absorption, the dichroic increment ratio, is characterized using the orthogonal orientation model, which assumes that each absorbing unit is aligned parallel to one of the principal axes of the apparatus. The absorption of the alienable molecules is characterized by components parallel and perpendicular to the orientable axis of the molecule. The dichroic increment ratio indicates that for the alignment of DNA in rectangular flow cells, average alignment is not uniaxial, but for higher shear, as produced in a Couette cell, it can be. The results from the simple model are identical to tensor models for typical experimental configurations. Approaches for measuring the dichroic increment ratio with modern dichrometers are discussed. Copyright © 2017. Published by Elsevier Inc.

The orientation of iron–sulphur clusters in membrane multilayers prepared from aerobically-grown Escherichia coli K12 and a cytochrome-deficient mutant

PubMed Central

Blum, Haywood; Poole, Robert K.; Ohnishi, Tomoko

1980-01-01

1. Membrane particles prepared from ultrasonically-disrupted, aerobically-grown Escherichia coli were centrifuged on to a plastic film that was supported perpendicular to the centrifugal field to yield oriented membrane multilayers. In such preparations, there is a high degree of orientation of the planes of the membranes such that they lie parallel to each other and to the supporting film. 2. When dithionite- or succinate-reduced multilayers are rotated in the magnetic field of an e.p.r. spectrometer, about an axis lying in the membrane plane, angular-dependent signals from an iron–sulphur cluster at gx=1.92, gy=1.93 and gz=2.02 are seen. The g=1.93 signal has maximal amplitude when the plane of the multilayer is perpendicular to the magnetic field. Conversely, the g=2.02 signal is maximal when the plane of the multilayer is parallel with the magnetic field. 3. Computer simulations of the experimental data show that the cluster lies in the cytoplasmic membrane with the gy axis perpendicular to the membrane plane and with the gx and gz axes lying in the membrane plane. 4. In partially-oxidized multilayers, a signal resembling the mitochondrial high-potential iron–sulphur protein (Hipip) is seen whose gz=2.02 axis may be deduced as lying perpendicular to the membrane plane. 5. Appropriate choice of sample temperature and receiver gain reveals two further signals in partially-reduced multilayers: a g=2.09 signal arises from a cluster with its gz axis in the membrane plane, whereas a g=2.04 signal is from a cluster with the gz axis lying along the membrane normal. 6. Membrane particles from a glucose-grown, haem-deficient mutant contain dramatically-lowered levels of cytochromes and exhibit, in addition to the iron–sulphur clusters seen in the parental strain, a major signal at g=1.90. 7. Only the latter may be demonstrated to be oriented in multilayer preparations from the mutant. 8. Comparisons are drawn between the orientations of the iron–sulphur proteins in the cytoplasmic membrane of E. coli and those in mitochondrial membranes. The effects of diminished cytochrome content on the properties of the iron–sulphur proteins are discussed. PMID:6258566

Magnetic Remanence and Anisotropy of Magnetic Susceptibility of Dikes From Super-Fast Spread Crust Exposed At Pito Deep Rift

NASA Astrophysics Data System (ADS)

Horst, A.; Varga, R. J.; Gee, J. S.; Karson, J. A.

2006-12-01

The tectonic window at the Pito Deep Rift exposes super-fast spread (>140mm/yr) oceanic crust created at the East Pacific Rise (EPR). Observations and investigations of well-exposed cross sections into modern ocean crust, such as Pito Deep, provide essential insights into ridge crest dynamics. Paleomagnetic analysis provides a quantitative means for assessing both magnitude and style of structural rotations of oceanic crust. The Pito Cruise 2005 collected 69 fully oriented samples [67 dikes, 2 gabbros] during several ALVIN and JASON II dives. These samples were all oriented in situ using the Geocompass. Along the escarpment of Pito Deep, dike orientations have consistant NE strikes and SE dips. These dikes are all formed roughly 3 million years ago at the EPR located to the west of their present position. We determined magnetic remanence for a subset of 34 oriented blocks. A majority of dikes in this subset have normal polarity and many are clockwise rotated from expected orientations. To assess possible orientation errors during collection, we sampled multiple dikes from relatively small areas. On ALVIN dive 4081, for example, we collected 14 samples from a well-exposed, subparallel series of dikes. These dikes provide stable and consistently oriented remanence directions suggesting that errors in the collection process are small. Remanence data collected to date verify tectonic models that suggest clockwise rotation of the Easter microplate, consistent with current models. In addition to magnetic remanence, we determined the anisotropy of magnetic susceptibility (AMS) of the 34 dike samples. AMS studies have proven their utility in a wide range of geological studies and have been shown to determine flow direction within dikes in a variety of settings. In most Pito Deep samples, two of three AMS eigenvectors lie close to dike plane orientations. Kmin generally lies perpendicular to dike planes while, in most samples, Kmax is shallow indicating dominantly subhorizontal magma flow. Steep Kmax in a few samples indicates vertical flow directions suggestive of primary flow or of gravitational back-flow during the waning stages of dike injection. Primarily horizontal magma flow in dikes might indicate injection of magma from a centralized magma chamber toward a plate segment boundary.

Determination of crack depth in aluminum using eddy currents and GMR sensors

NASA Astrophysics Data System (ADS)

Lopes Ribeiro, A.; Pasadas, D.; Ramos, H. G.; Rocha, T.

2015-03-01

In this paper we use eddy currents to determine the depth of linear cracks in aluminum plates. A constant field probe is used to generate the spatially uniform excitation field and a single axis giant magneto-resistor (GMR) sensor is used to measure the eddy currents magnetic field. Different depths were machined in one aluminum plate with 4 mm of thickness. By scanning those cracks the magnetic field components parallel and perpendicular to the crack's line were measured when the eddy currents were launched perpendicularly to the crack's line. To characterize one crack in a plate of a given thickness and material, the experimental procedure was defined. The plate surface is scanned to detect and locate one crack. The acquired data enables the determination of the crack's length and orientation. A second scanning is performed with the excitation current perpendicular to the crack and the GMR sensing axis perpendicular and parallel to the crack's line.

Strain history of ice shells of the Galilean satellites from radar detection of crystal orientation fabric

NASA Astrophysics Data System (ADS)

Barr, Amy C.; Stillman, David E.

2011-03-01

Orbital radar sounding has been suggested as a means of determining the subsurface thermal and physical structure of the outer ice I shells of the Galilean satellites. At radar frequencies, the dielectric permittivity of single- and polycrystalline water ice I is anisotropic. Crystal orientation fabric (COF), which is indicative of strain history, can be unambiguously detected by comparing the received power of dual co-polarization (linear polarization parallel and perpendicular to the orbit) radar data. Regions with crystal orientations dictated by the local strain field (“fabric”) form in terrestrial ice masses where accumulated strain and temperature are high, similar to conditions expected in a convecting outer ice I shell on Europa, Ganymede, or Callisto. We use simulations of solid-state ice shell convection to show that crystal orientation fabric can form in the warm convecting sublayer of the ice shells for plausible grain sizes. Changes in received power from parallel and perpendicular polarizations in the ice shells due to fabric could be detected if multi-polarization data is collected. With proper instrument design, radar sounding could be used to shed light on the strain history of the satellites' ice shells in addition to their present day internal structures.

Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite

PubMed Central

Checa, Antonio G.; Bonarski, Jan T.; Willinger, Marc G.; Faryna, Marek; Berent, Katarzyna; Kania, Bogusz; González-Segura, Alicia; Pina, Carlos M.; Pospiech, Jan; Morawiec, Adam

2013-01-01

The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research. PMID:23804442

Onion epidermis as a new model to study the control of growth anisotropy in higher plants.

PubMed

Suslov, Dmitry; Verbelen, Jean-Pierre; Vissenberg, Kris

2009-01-01

To elucidate the role of cellulose microfibrils in the control of growth anisotropy, a link between their net orientation, in vitro cell wall extensibility, and anisotropic cell expansion was studied during development of the adaxial epidermis of onion (Allium cepa) bulb scales using polarization confocal microscopy, creep tests, and light microscopy. During growth the net cellulose alignment across the whole thickness of the outer epidermal wall changed from transverse through random to longitudinal and back to transverse relative to the bulb axis. Cell wall extension in vitro was always higher transverse than parallel to the net cellulose alignment. The direction of growth anisotropy was perpendicular to the net microfibril orientation and changed during development from longitudinal to transverse to the bulb axis. The correlation between the degree of growth anisotropy and the net cellulose alignment was poor. Thus the net cellulose microfibril orientation across the whole thickness of the outer periclinal epidermis wall defines the direction but not the degree of growth anisotropy. Strips isolated from the epidermis in the directions perpendicular and transverse to a net cellulose orientation can be used as an extensiometric model to prove a protein involvement in the control of growth anisotropy.

Exchange coupled CoPd/TbCo magneto-optic storage films

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

Gambino, R.J.; Ruf, R.R.; Rishi, R.

1989-09-01

Films of CoPd with weak perpendicular anisotropy are shown to exchange couple to square loop TbCo films on both the Tb and Co sides of compensation. The exchange is sensitive to reactive impurities at the interface and is broken under conditions that produce as little as one monolayer of paramagnetic compound. Even when the coupling at the interface is strong, the authors show that only a limited thickness of the CoPd layer is spin oriented perpendicular.

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

Luo, Sijun, E-mail: sluo1@tulane.edu; Riggs, Brian C.; Shipman, Joshua T.

Direct integration of proton conductor films on Pt-coated substrates opens the way to film-based proton transport devices. Columnar SrZr{sub 0.95}Y{sub 0.05}O{sub 3−δ} (SZY) films with dense microstructure were deposited on Pt-coated MgO(100) substrates at 830 °C by pulsed laser deposition. The optimal window of ambient O{sub 2} pressure for good crystallinity of SZY films is from 400 to 600 mTorr. The ambient O{sub 2} compresses the plasma plume of SZY and increases the deposition rate. The 10 nm thick Ti adhesion layer on MgO(100) greatly affects the orientation of the sputtered Pt layers. Pt deposited directly on MgO shows a highly (111)-preferredmore » orientation and leads to preferentially oriented SZY films while the addition of a Ti adhesion layer makes Pt show a less preferential orientation that leads to randomly oriented SZY films. The RMS surface roughness of preferentially oriented SZY films is larger than that of randomly oriented SZY films deposited under the same ambient O{sub 2} pressure. As the O{sub 2} pressure increased, the RMS surface roughness of preferentially oriented SZY films increased, reaching 45.7 nm (2.61% of film thickness) at 600 mTorr. This study revealed the ambient O{sub 2} pressure and orientation dependent surface roughness of SZY films grown on Pt-coated MgO substrates, which provides the potential to control the surface microstructure of SZY films for electrochemical applications in film-based hydrogen devices.« less

Effects of Fiber Orientation on the Frictional Properties and Damage of Regenerative Articular Cartilage Surfaces

PubMed Central

Accardi, Mario Alberto; McCullen, Seth D.; Callanan, Anthony; Chung, Sangwon; Cann, Philippa M.

2013-01-01

Articular cartilage provides a low-friction, wear-resistant surface for diarthrodial joints. Due to overloading and overuse, articular cartilage is known to undergo significant wear and degeneration potentially resulting in osteoarthritis (OA). Regenerative medicine strategies offer a promising solution for the treatment of articular cartilage defects and potentially localized early OA. Such strategies rely on the development of materials to restore some aspects of cartilage. In this study, microfibrous poly(ɛ-caprolactone) scaffolds of varying fiber orientations (random and aligned) were cultured with bovine chondrocytes for 4 weeks in vitro, and the mechanical and frictional properties were evaluated. Mechanical properties were quantified using unconfined compression and tensile testing techniques. Frictional properties were investigated at physiological compressive strains occurring in native articular cartilage. Scaffolds were sheared along the fiber direction, perpendicular to the fiber direction and in random orientation. The evolution of damage as a result of shear was evaluated via white light interferometry and scanning electron microscopy. As expected, the fiber orientation strongly affected the tensile properties as well as the compressive modulus of the scaffolds. Fiber orientation did not significantly affect the equilibrium frictional coefficient, but it was, however, a key factor in dictating the evolution of surface damage on the surface. Scaffolds shear tested perpendicular to the fiber orientation displayed the highest surface damage. Our results suggest that the fiber orientation of the scaffold implanted in the joint could strongly affect its resistance to damage due to shear. Scaffold fiber orientation should thus be carefully considered when using microfibrous scaffolds. PMID:23688110

Gravitational effects on the weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding of 304 stainless steel and Al-4 wt% Cu alloy.

PubMed

Kang, Namhyun; Singh, Jogender; Kulkarni, Anil K

2004-11-01

Effects of gravitational acceleration were investigated on the weld pool shape and microstructural evolution for 304 stainless steel and Al-4wt% Cu alloy. Effects of welding heat source were investigated by using laser beam welding (LBW) and gas tungsten arc welding (GTAW). As the gravitational level was increased from low gravity (LG approximately 1.2 g) to high gravity (HG approximately 1.8 g) using a NASA KC-135 aircraft, the weld pool shape for 304 stainless steel was influenced considerably during GTAW. However, insignificant change in the microstructure and solute distribution was observed at gravitational levels between LG and HG. The GTAW on Al-4 wt% Cu alloy was used to investigate the effect of gravitational orientation on the weld solidification behavior. Gravitational orientation was manipulated by varying the welding direction with respect to gravity vector; that is, by welding upward opposing gravity ( ||-U) and downward with gravity ( ||-D) on a vertical weld piece and welding perpendicular to gravity (perpendicular) on a horizontal weld piece. Under the same welding conditions, a larger primary dendrite spacing in the ||-U weld was observed near the weld pool surface and the fusion boundary than in the case of perpendicular or ||-D welds. The ||-D weld exhibited different solidification morphology and abnormal S shape of solidification rate curve during its growth. For 304 stainless steel GTAW, significant effects of gravitational orientation were observed on the weld pool shape that was associated with weld surface morphology and convection flow. However, the weld pool shape for LBW was mostly constant with respect to the gravitational orientation.

Nutrient and dust enrichment in Danish wind erosion sediments for different tillage directions

NASA Astrophysics Data System (ADS)

Mohammadian Behbahani, Ali; Fister, Wolfgang; Heckrath, Goswin; Kuhn, Nikolaus J.

2015-04-01

More than 80% of the soil types in Denmark have a sandy texture. Denmark is also subject to strong offshore and onshore winds, therefore, Danish soils are considered especially vulnerable to wind erosion. Where conventional tillage operations are applied on poorly aggregated soils, tillage ridges are more or less the only roughness element that can be used to protect soils against wind erosion until crop plants are large enough to provide sufficient breaks. Since wind erosion is a selective process, it can be assumed that increasing erosion rates are associated with increasing loss of dust sized particles and nutrients. However, selective erosion is strongly affected by the orientation and respective trapping efficiency of tillage ridges and furrows. The main objective of this study, therefore, was to determine the effect of tillage direction on nutrient mobilization by wind erosion from agricultural land in Denmark. In order to assess the relationship between the enrichment ratio of specific particle sizes and the amount of eroded nutrients, three soils with loamy sand texture, but varying amounts of sand-sized particles, were selected. In addition, a soil with slightly less sand, but much higher organic matter content was chosen. The soils were tested with three different soil surface scenarios (flat surface, parallel tillage, perpendicular tillage) in a wind tunnel simulation. The parallel tillage operation experienced the greatest erosion rates, independent of soil type. Particles with D50 between 100-155 µm showed the greatest risk of erosion. However, due to a greater loss of dust sized particles from perpendicularly tilled surfaces, this wind-surface arrangement showed a significant increase in nutrient enrichment ratio compared to parallel tillage and flat surfaces. The main reason for this phenomenon is most probably the trapping of larger particles in the perpendicular furrows. This indicates that the highest rate of soil protection does not necessarily coincide with lowest soil nutrient losses and dust emissions. For the evaluation of protection measures on these soil types in Denmark it is, therefore, important to differentiate between their effectivity to reduce total soil erosion amount, dust emission, and nutrient loss.

The relationship between magnetic anisotropy, rock-strength anisotropy and vein emplacement in gold-bearing metabasalts of Gadag (South India)

NASA Astrophysics Data System (ADS)

Vishnu, C. S.; Lahiri, Sivaji; Mamtani, Manish A.

2018-01-01

In this study the importance of rock strength and its anisotropy in controlling vein emplacement is evaluated by integrating anisotropy of magnetic susceptibility (AMS) with rock mechanics data from massive (visibly isotropic) metabasalts of Gadag region (Dharwar Craton, South India). Orientation of magnetic foliation (MF) is first recognized from AMS. Subsequently, rock mechanics tests viz. ultrasonic P-wave velocity (Vp), uniaxial compressive strength (UCS) and point load strength (Is(50)) are done in cores extracted parallel and perpendicular to MF. Vp is found to be higher in direction parallel to MF than perpendicular to it. In contrast rock strength (UCS and Is(50)) is greater in direction perpendicular to MF, than parallel to it. This proves that rocks from the gold mineralized belt of Gadag have rock strength anisotropy. Orientation of MF in Gadag region is NW-SE, which is also the mean orientation of quartz veins. Previous studies indicate that emplacement of veins in the region took place during regional D3 (NW-SE shortening). Based on the present study, it is concluded that vein emplacement took place in NW-SE orientation because the rocks have strength anisotropy and are weaker in this direction (orientation of MF), which dilated to accommodate fluid flow. In addition, vein intensities are measured along three traverses and found to be variable. It is argued that since mineralization is favoured when the system gets saturated with fluid, variation in fluid flow could not have been responsible for variation in vein intensities in the study area. Since the rock strength of the different blocks investigated here is not uniform, it is envisaged that variation in rock strength played an important role in controlling the vein intensities. It is concluded that rock strength variation controlled strain partitioning and channelized fluid flow thus influencing vein emplacement and mineralization and formation of lodes.

Studies of SERS efficiency of gold coated porous silicon formed on rough silicon backside

NASA Astrophysics Data System (ADS)

Dridi, H.; Haji, L.; Moadhen, A.

2017-12-01

Starting from a rough backside of silicon wafer, we have formed a porous layer by electrochemical anodization and then coated by a thin film of gold. The morphological characteristics of the porous silicon and in turn the metal film are governed by the anodization process and also by the starting surface. So, in order to investigate the Plasmonic aspect of such rough surface which combines roughness inherent to the porous nature and that due to rough starting surface, we have used a dye target molecule to study its SERS signal using a porous silicon layer obtained on the rough backside surface. The use of unusual backside of silicon wafer could be, beside the others, an interesting way to made SERS effective substrate thanks to reproducible rough porous gold on porous layer from this starting face. The morphological results correspond to the silicon rough surface as a function of the crystallographic orientation showed the presence of two different substrate structure. The optical reflectivity results obtained of gold deposited on oxidized porous silicon showed a dependence of its Localized Surface Plasmon band frequency of the deposit time. SERS results, obtained for a dye target molecule (Rhodamine 6G), show a higher intensities in the case of the 〈110〉 orientation, which characterized by the higher roughness surface. Voici "the most relevant and important aspects of our work".

Disorder-to-order transitions induced by alkyne/azide click chemistry in diblock copolymer thin films.

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

Wei, X.; Gu, W.; Chen, W.

2012-01-01

We investigated thin film morphologies of binary blends of alkyne-functionalized diblock copolymer poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) and Rhodamine B azide, where the thermal alkyne/azide click reaction between the two components induced a disorder-to-order transition (DOT) of the copolymer. By controlling the composition of the neat copolymers and the mole ratio between the alkyne and azide groups, different microphase separated morphologies were achieved. At higher azide loading ratios, a perpendicular orientation of the microdomains was observed with wide accessible film thickness window. As less azide was incorporated, the microdomains have a stronger tendency to be parallel to the substrate, andmore » the film thickness window for perpendicular orientation also became narrower.« less

Perpendicular magnetic anisotropy and spin reorientation transition in L1{sub 0} FePt films

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

Ahn, Jae Young; Lee, Nyun Jong; Kim, Tae Hee

2011-04-01

We investigated the thickness and composition dependence of perpendicular magnetic anisotropy (PMA) in L1{sub 0} Fe{sub 1-x}Pt{sub x} (x = 0.4, 0.5, and 0.55) films. The FePt films with different thicknesses of 35 and 70 A were grown at the substrate temperature T{sub s} = 300 deg. C by molecular beam epitaxy coevaporation technique. A (001)-oriented epitaxial L1{sub 0} FePt film was grown on the thin (001)-oriented fcc Pt layer, while a poorly crystallized FePt film was formed on the (111)-textured Pt layer. Our results showed that, at a fixed thickness of 70 A, the PMA of FePt alloy filmsmore » is enhanced as Pt content increases from 40% to 55%.« less

Effects of stress fiber contractility on uniaxial stretch guiding mitosis orientation and stress fiber alignment.

PubMed

Zhao, Lei; Sang, Chen; Yang, Chun; Zhuang, Fengyuan

2011-09-02

It has been documented that mitosis orientation (MO) is guided by stress fibers (SFs), which are perpendicular to exogenous cyclic uniaxial stretch. However, the effect of mechanical forces on MO and the mechanism of stretch-induced SFs reorientation are not well elucidated to date. In the present study, we used murine 3T3 fibroblasts as a model, to investigate the effects of uniaxial stretch on SFO and MO utilizing custom-made stretch device. We found that cyclic uniaxial stretch induced both SFs and mitosis directions orienting perpendicularly to the stretch direction. The F-actin and myosin II blockages, which resulted in disoriented SFs and mitosis directions under uniaxial stretch, suggested a high correlation between SFO and MO. Y27632 (10 μM), ML7 (50 μM, or 75 μM), and blebbistatin (50 μM, or 75 μM) treatments resulted in SFO parallel to the principle stretch direction. Upon stimulating and inhibiting the phosphorylation of myosin light chain (p-MLC), we observed a monotonic proportion of SFO to the level of p-MLC. These results suggested that the level of cell contraction is crucial to the response of SFs, either perpendicular or parallel, to the external stretch. Showing the possible role of cell contractility in tuning SFO under external stretch, our experimental data are valuable to understand the predominant factor controlling SFO response to exogenous uniaxial stretch, and thus helpful for improving mechanical models. Copyright © 2011 Elsevier Ltd. All rights reserved.

Effects of Build Orientation on Surface Morphology and Bone Cell Activity of Additively Manufactured Ti6Al4V Specimens.

PubMed

Weißmann, Volker; Drescher, Philipp; Seitz, Hermann; Hansmann, Harald; Bader, Rainer; Seyfarth, Anika; Klinder, Annett; Jonitz-Heincke, Anika

2018-05-29

Additive manufacturing of lightweight or functional structures by selective laser beam (SLM) or electron beam melting (EBM) is widespread, especially in the field of medical applications. SLM and EBM processes were applied to prepare Ti6Al4V test specimens with different surface orientations (0°, 45° and 90°). Roughness measurements of the surfaces were conducted and cell behavior on these surfaces was analyzed. Hence, human osteoblasts were seeded on test specimens to determine cell viability (metabolic activity, live-dead staining) and gene expression of collagen type 1 (Col1A1), matrix metalloprotease (MMP) 1 and its natural inhibitor, TIMP1, after 3 and 7 days. The surface orientation of specimens during the manufacturing process significantly influenced the roughness. Surface roughness showed significant impact on cellular viability, whereas differences between the time points day 3 and 7 were not found. Collagen type 1 mRNA synthesis rates in human osteoblasts were enhanced with increasing roughness. Both manufacturing techniques further influenced the induction of bone formation process in the cell culture. Moreover, the relationship between osteoblastic collagen type 1 mRNA synthesis rates and specimen orientation during the building process could be characterized by functional formulas. These findings are useful in the designing of biomedical applications and medical devices.

Procedure for estimating fracture energy from fracture surface roughness

DOEpatents

Williford, Ralph E.

1989-01-01

The fracture energy of a material is determined by first measuring the length of a profile of a section through a fractured surface of the material taken on a plane perpendicular to the mean plane of that surface, then determining the fractal dimensionality of the surface. From this, the yield strength of the material, and the Young's Modulus of that material, the fracture energy is calculated.

Structural Analysis of Hand Drawn Bumblebee Bombus terrestris Silk.

PubMed

Woodhead, Andrea L; Sutherland, Tara D; Church, Jeffrey S

2016-07-20

Bombus terrestris, commonly known as the buff-tailed bumblebee, is native to Europe, parts of Africa and Asia. It is commercially bred for use as a pollinator of greenhouse crops. Larvae pupate within a silken cocoon that they construct from proteins produced in modified salivary glands. The amino acid composition and protein structure of hand drawn B. terrestris, silk fibres was investigated through the use of micro-Raman spectroscopy. Spectra were obtained from single fibres drawn from the larvae salivary gland at a rate of 0.14 cm/s. Raman spectroscopy enabled the identification of poly(alanine), poly(alanine-glycine), phenylalanine, tryptophan, and methionine, which is consistent with the results of amino acid analysis. The dominant protein conformation was found to be coiled coil (73%) while the β-sheet content of 10% is, as expected, lower than those reported for hornets and ants. Polarized Raman spectra revealed that the coiled coils were highly aligned along the fibre axis while the β-sheet and random coil components had their peptide carbonyl groups roughly perpendicular to the fibre axis. The protein orientation distribution is compared to those of other natural and recombinant silks. A structural model for the B. terrestris silk fibre is proposed based on these results.

Ultrasmooth, Polydopamine Modified Surfaces for Block Copolymer Nanopatterning on Inert and Flexible Substrates

NASA Astrophysics Data System (ADS)

Katsumata, Reika; Cho, Joon Hee; Zhou, Sunshine; Kim, Chae Bin; Dulaney, Austin; Janes, Dustin; Ellison, Christopher

Nature has engineered universal, catechol-containing adhesives that can be synthetically mimicked in the form of polydopamine (PDA). We exploited PDA to enable block copolymer (BCP) nanopatterning on a variety of soft material surfaces in a way that can potentially be applied to flexible electrical devices. Applying BCP nanopatterning to soft substrates is challenging because soft substrates are often chemically inert and possess incompatible low surface energies. In this study, we exploited PDA to enable the formation of BCP nanopatterns on a variety of surfaces such as Teflon, poly(ethylene terephthalate) (PET), and Kapton. While previous studies produced a PDA coating layer too rough for BCP nanopatterning, we succeeded in fabricating conformal and ultra-smooth surfaces of PDA by engineering the PDA coating process and post-sonication procedure. This chemically functionalized, biomimetic thin film (3 nm thick) served as a reactive platform for subsequently grafting a surface treatment to perpendicularly orient a lamellae-forming BCP layer. Furthermore, we demonstrated that a perfectly nanopatterned PDA-PET substrate can be bent without distorting or damaging the nanopattern in conditions that far exceeds typical bending curvatures in roll-to-roll manufacturing.

Synthetic-Aperture Silhouette Imaging (SASI)

NASA Astrophysics Data System (ADS)

Paxman, R.

2016-09-01

The problem of ground-based fine-resolution imaging of geosynchronous satellites continues to be an important unsolved space-surveillance problem. We are investigating a passive-illumination approach that is radically different from amplitude, intensity, or heterodyne interferometry approaches. The approach, called Synthetic-Aperture Silhouette Imaging (SASI), produces a fine-resolution image of the satellite silhouette. When plane-wave radiation emanating from a bright star is occluded by a GEO satellite, then the light is diffracted and a moving diffraction pattern (shadow) is cast on the surface of the earth. With prior knowledge of the satellite orbit and star location, the track of the moving shadow can be predicted with high precision. A linear array of inexpensive hobby telescopes can be deployed roughly perpendicular to the shadow track to collect a time history of the star intensity as the shadow passes by. A phase-retrieval algorithm, using the strong constraint that the occlusion of the satellite is a binary-valued silhouette, allows us to retrieve the missing phase and reconstruct a fine-resolution image of the silhouette. Silhouettes are highly informative, providing diagnostic information about deployment of antennas and solar panels, enabling satellite pose estimation, and revealing the presence and orientation of neighboring satellites in rendezvous and proximity operations.

The use of Rz roughness parameter for evaluation of materials behavior to cavitation erosion

NASA Astrophysics Data System (ADS)

Bordeasu, I.; Popoviciu, M. O.; Ghera, C.; Micu, L. M.; Pirvulescu, L. D.; Bena, T.

2018-01-01

It is well known that the cavitation eroded surfaces have a porous appearance with a pronounced roughness. The cause is the pitting resulted from the impact with the micro jets as well as the shock waves both determined by the implosion of cavitation bubbles. The height and the shape of roughness is undoubtedly an expression of the resistance of the surface to the cavitation stresses. The paper put into evidence the possibility of using the roughness parameter Rz for estimating the material resistance to cavitation phenomena. For this purpose, the mean depth erosion penetration (MDE-parameter, recommended by the ASTM G32-2010 Standard) was compared with the roughness of three different materials (an annealed bronze, the same bronze subjected to quenching and an annealed alloyed steel), both measured at four cavitation erosion exposure (30, 75, 120 and 165 minutes). The roughness measurements were made in 18 different zones, disposed after two perpendicular diameters, along a measuring lengths of 4 mm. The results confirm the possibility of using the parameter Rz for estimating the cavitation erosion resistance of a material. The differences between the measured values of Rz and those of the characteristic parameter MDE are of the same order of magnitude as those obtained for MDE determination, using more samples of the same material.

Quantitative three-dimensional ice roughness from scanning electron microscopy

NASA Astrophysics Data System (ADS)

Butterfield, Nicholas; Rowe, Penny M.; Stewart, Emily; Roesel, David; Neshyba, Steven

2017-03-01

We present a method for inferring surface morphology of ice from scanning electron microscope images. We first develop a novel functional form for the backscattered electron intensity as a function of ice facet orientation; this form is parameterized using smooth ice facets of known orientation. Three-dimensional representations of rough surfaces are retrieved at approximately micrometer resolution using Gauss-Newton inversion within a Bayesian framework. Statistical analysis of the resulting data sets permits characterization of ice surface roughness with a much higher statistical confidence than previously possible. A survey of results in the range -39°C to -29°C shows that characteristics of the roughness (e.g., Weibull parameters) are sensitive not only to the degree of roughening but also to the symmetry of the roughening. These results suggest that roughening characteristics obtained by remote sensing and in situ measurements of atmospheric ice clouds can potentially provide more facet-specific information than has previously been appreciated.

Intrinsic suppression of turbulence in linear plasma devices

NASA Astrophysics Data System (ADS)

Leddy, J.; Dudson, B.

2017-12-01

Plasma turbulence is the dominant transport mechanism for heat and particles in magnetised plasmas in linear devices and tokamaks, so the study of turbulence is important in limiting and controlling this transport. Linear devices provide an axial magnetic field that serves to confine a plasma in cylindrical geometry as it travels along the magnetic field from the source to the strike point. Due to perpendicular transport, the plasma density and temperature have a roughly Gaussian radial profile with gradients that drive instabilities, such as resistive drift-waves and Kelvin-Helmholtz. If unstable, these instabilities cause perturbations to grow resulting in saturated turbulence, increasing the cross-field transport of heat and particles. When the plasma emerges from the source, there is a time, {τ }\\parallel , that describes the lifetime of the plasma based on parallel velocity and length of the device. As the plasma moves down the device, it also moves azimuthally according to E × B and diamagnetic velocities. There is a balance point in these parallel and perpendicular times that sets the stabilisation threshold. We simulate plasmas with a variety of parallel lengths and magnetic fields to vary the parallel and perpendicular lifetimes, respectively, and find that there is a clear correlation between the saturated RMS density perturbation level and the balance between these lifetimes. The threshold of marginal stability is seen to exist where {τ }\\parallel ≈ 11{τ }\\perp . This is also associated with the product {τ }\\parallel {γ }* , where {γ }* is the drift-wave linear growth rate, indicating that the instability must exist for roughly 100 times the growth time for the instability to enter the nonlinear growth phase. We explore the root of this correlation and the implications for linear device design.

3D-shape recognition and size measurement of irregular rough particles using multi-views interferometric out-of-focus imaging.

PubMed

Ouldarbi, L; Talbi, M; Coëtmellec, S; Lebrun, D; Gréhan, G; Perret, G; Brunel, M

2016-11-10

We realize simplified-tomography experiments on irregular rough particles using interferometric out-of-focus imaging. Using two angles of view, we determine the global 3D-shape, the dimensions, and the 3D-orientation of irregular rough particles whose morphologies belong to families such as sticks, plates, and crosses.

Out of control: attentional selection for orientation is thwarted by properties of the underlying neural mechanisms.

PubMed

Du, Feng; Abrams, Richard A

2012-09-01

To avoid sensory overload, people are able to selectively attend to a particular color or direction of motion while ignoring irrelevant stimuli that differ from the desired one. We show here for the first time that it is also possible to selectively attend to a specific line orientation-but with an important caveat: orientations that are perpendicular to the target orientation cannot be suppressed. This effect reflects properties of the neural mechanisms selective for orientation and reveals the extent to which contingent capture is constrained not only by one's top-down goals but also by feature preferences of visual neurons. Copyright © 2012 Elsevier B.V. All rights reserved.

Thermally induced chain orientation for improved thermal conductivity of P(VDF-TrFE) thin films

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

Zhao, Junnan; Tan, Aaron C.; Green, Peter F.

2017-01-01

A large increase in thermal conductivityκwas observed in a P(VDF-TrFE) thin film annealed above melting temperature due to extensive ordering of polymer backbone chains perpendicular to the substrate after recrystallization from the melt. This finding may lay out a straightforward method to improve the thin filmκof semicrystalline polymers whose chain orientation is sensitive to thermal annealing.

Tuning the electrical and optical anisotropy of a monolayer black phosphorus magnetic superlattice

NASA Astrophysics Data System (ADS)

Li, X. J.; Yu, J. H.; Luo, K.; Wu, Z. H.; Yang, W.

2018-04-01

We investigate theoretically the effects of modulated periodic perpendicular magnetic fields on the electronic states and optical absorption spectrum in monolayer black phosphorus (phosphorene). We demonstrate that different phosphorene magnetic superlattice (PMS) orientations can give rise to distinct energy spectra, i.e. tuning the intrinsic electronic anisotropy. Rashba spin-orbit coupling (RSOC) develops a spin-splitting energy dispersion in this phosphorene magnetic superlattice. Anisotropic momentum-dependent carrier distributions along/perpendicular to the magnetic strips are demonstrated. The manipulations of these exotic electronic properties by tuning superlattice geometry, magnetic field and the RSOC term are addressed systematically. Accordingly, we find bright-to-dark transitions in the ground-state electron-hole pair transition rate spectrum and the PMS orientation-dependent anisotropic optical absorption spectrum. This feature offers us a practical way of modulating the electronic anisotropy in phosphorene by magnetic superlattice configurations and detecting this modulation capability by using an optical technique.

Theoretical and Experimental Triple Differential Cross Sections for Electron Impact Ionization of SF6

NASA Astrophysics Data System (ADS)

Chaluvadi, Hari; Nixon, Kate; Murray, Andrew; Ning, Chuangang; Colgan, James; Madison, Don

2014-10-01

Experimental and theoretical Triply Differential Cross Sections (TDCS) will be presented for electron-impact ionization of sulfur hexafluoride (SF6) for the molecular orbital 1t1g. M3DW (molecular 3-body distorted wave) results will be compared with experiment for coplanar geometry and for perpendicular plane geometry (a plane which is perpendicular to the incident beam direction). In both cases, the final state electron energies and observation angles are symmetric and the final state electron energies range from 5 eV to 40 eV. It will be shown that there is a large difference between using the OAMO (orientation averaged molecular orbital) approximation and the proper average over all orientations and also that the proper averaged results are in much better agreement with experiment. Work supported by NSF under Grant Number PHY-1068237. Computational work was performed with Institutional resources made available through Los Alamos National Laboratory.

An experimental study of tip shape effects on the flutter of aft-swept, flat-plate wings

NASA Technical Reports Server (NTRS)

Dansberry, Bryan E.; Rivera, Jose A., Jr.; Farmer, Moses G.

1990-01-01

The effects of tip chord orientation on wing flutter are investigated experimentally using six cantilever-mounted, flat-plate wing models. Experimentally determined flutter characteristics of the six models are presented covering both the subsonic and transonic Mach number ranges. While all models have a 60 degree leading edge sweep, a 40.97 degree trailing edge sweep, and a root chord of 34.75 inches, they are subdivided into two series characterized by a higher aspect ratio and a lower aspect ratio. Each series is made up of three models with tip chord orientations which are parallel to the free-stream flow, perpendicular to the model mid-chord line, and perpendicular to the free-stream flow. Although planform characteristics within each series of models are held constant, structural characteristics such as mode shapes and natural frequencies are allowed to vary.

The direction of stretch-induced cell and stress fiber orientation depends on collagen matrix stress.

PubMed

Tondon, Abhishek; Kaunas, Roland

2014-01-01

Cell structure depends on both matrix strain and stiffness, but their interactive effects are poorly understood. We investigated the interactive roles of matrix properties and stretching patterns on cell structure by uniaxially stretching U2OS cells expressing GFP-actin on silicone rubber sheets supporting either a surface-adsorbed coating or thick hydrogel of type-I collagen. Cells and their actin stress fibers oriented perpendicular to the direction of cyclic stretch on collagen-coated sheets, but oriented parallel to the stretch direction on collagen gels. There was significant alignment parallel to the direction of a steady increase in stretch for cells on collagen gels, while cells on collagen-coated sheets did not align in any direction. The extent of alignment was dependent on both strain rate and duration. Stretch-induced alignment on collagen gels was blocked by the myosin light-chain kinase inhibitor ML7, but not by the Rho-kinase inhibitor Y27632. We propose that active orientation of the actin cytoskeleton perpendicular and parallel to direction of stretch on stiff and soft substrates, respectively, are responses that tend to maintain intracellular tension at an optimal level. Further, our results indicate that cells can align along directions of matrix stress without collagen fibril alignment, indicating that matrix stress can directly regulate cell morphology.

Phase Transition Control for High Performance Ruddlesden-Popper Perovskite Solar Cells.

PubMed

Zhang, Xu; Munir, Rahim; Xu, Zhuo; Liu, Yucheng; Tsai, Hsinhan; Nie, Wanyi; Li, Jianbo; Niu, Tianqi; Smilgies, Detlef-M; Kanatzidis, Mercouri G; Mohite, Aditya D; Zhao, Kui; Amassian, Aram; Liu, Shengzhong Frank

2018-05-01

Ruddlesden-Popper reduced-dimensional hybrid perovskite (RDP) semiconductors have attracted significant attention recently due to their promising stability and excellent optoelectronic properties. Here, the RDP crystallization mechanism in real time from liquid precursors to the solid film is investigated, and how the phase transition kinetics influences phase purity, quantum well orientation, and photovoltaic performance is revealed. An important template-induced nucleation and growth of the desired (BA) 2 (MA) 3 Pb 4 I 13 phase, which is achieved only via direct crystallization without formation of intermediate phases, is observed. As such, the thermodynamically preferred perpendicular crystal orientation and high phase purity are obtained. At low temperature, the formation of intermediate phases, including PbI 2 crystals and solvate complexes, slows down intercalation of ions and increases nucleation barrier, leading to formation of multiple RDP phases and orientation randomness. These insights enable to obtain high quality (BA) 2 (MA) 3 Pb 4 I 13 films with preferentially perpendicular quantum well orientation, high phase purity, smooth film surface, and improved optoelectronic properties. The resulting devices exhibit high power conversion efficiency of 12.17%. This work should help guide the perovskite community to better control Ruddlesden-Popper perovskite structure and further improve optoelectronic and solar cell devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films on glass substrates with perpendicular magnetic anisotropy

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

An, Hongyu; Sannomiya, Takumi; Muraishi, Shinji

2015-03-15

To obtain strong perpendicular magnetic anisotropy (PMA) based on L1{sub 0} structure for magnetic storage devices, costly single crystalline substrates are generally required to achieve (001) texture. Recently, various studies also have focused on depositing different kinds of seed layers on glass or other amorphous substrates to promote (001) preferred orientation of L1{sub 0} CoPt and FePt. TiN is a very promising seed layer material because of its cubic crystalline structure (similar to MgO) and excellent diffusion barring property even at high temperatures. In the present work, highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films have been successfully deposited on glassmore » substrates. After annealing at 700 °C, the film exhibits PMA, and a strong (001) peak is detected from the x-ray diffraction profiles, indicating the ordering transformation of CoPt layers from fcc (A1) to L1{sub 0} structure. It also is found that alternate deposition of cubic TiN and CoPt effectively improves the crystallinity and (001) preferred orientation of CoPt layers. This effect is verified by the substantial enhancement of (001) reflection and PMA with increasing the period number of the multilayer films.« less

Domain wall pinning on strain relaxation defects (stacking faults) in nanoscale FePd (001)/MgO thin films

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

Hsiao, C. H.; Ouyang, Chuenhou, E-mail: wei0208@gmail.com, E-mail: houyang@mx.nthu.edu.tw; Yao, Y. D.

FePd (001) films, prepared by an electron beam deposition system on MgO(100), exhibit a perpendicular magnetic anisotropy (1.7 × 10{sup 7 }erg/cc) with a high order parameter (0.92). The relation between stacking faults induced by the strain relaxation, which act as strong domain wall pinning sites, and the perpendicular coercivity of (001) oriented L1{sub 0} FePd films prepared at different temperatures have been investigated. Perpendicular coercivity can be apparently enhanced by raising the stacking fault densities, which can be elevated by climbing dissociation of total dislocation. The increased stacking fault densities (1.22 nm{sup −2}) with large perpendicular coercivity (6000 Oe) are obtained for samples preparedmore » at 650 °C. This present work shows through controlling stacking fault density in FePd film, the coercivity can be manipulated, which can be applied in future magnetic devices.« less

Induction logging device

DOEpatents

Koelle, A.R.; Landt, J.A.

An instrument is disclosed for mapping vertical conductive fractures in a resistive bedrock, magnetically inducing eddy currents by a pair of vertically oriented, mutually perpendicular, coplanar coils. The eddy currents drive magnetic fields which are picked up by a second, similar pair of coils.

Nanohashtag structures based on carbon nanotubes and molecular linkers

NASA Astrophysics Data System (ADS)

Frye, Connor W.; Rybolt, Thomas R.

2018-03-01

Molecular mechanics was used to study the noncovalent interactions between single-walled carbon nanotubes and molecular linkers. Groups of nanotubes have the tendency to form tight, parallel bundles (||||). Molecular linkers were introduced into our models to stabilize nanostructures with carbon nanotubes held in perpendicular orientations. Molecular mechanics makes it possible to estimate the strength of noncovalent interactions holding these structures together and to calculate the overall binding energy of the structures. A set of linkers were designed and built around a 1,3,5,7-cyclooctatetraene tether with two corannulene containing pincers that extend in opposite directions from the central cyclooctatetraene portion. Each pincer consists of a pairs of "arms." These molecular linkers were modified so that the "hand" portions of each pair of "arms" could close together to grab and hold two carbon nanotubes in a perpendicular arrangement. To illustrate the possibility of more complicated and open perpendicular CNTs structures, our primary goal was to create a model of a nanohashtag (#) CNT conformation that is more stable than any parallel CNT arrangements with bound linker molecules forming clumps of CNTs and linkers in non-hashtag arrangements. This goal was achieved using a molecular linker (C280H96) that utilizes van der Waals interactions to two perpendicular oriented CNTs. Hydrogen bonding was then added between linker molecules to augment the stability of the hashtag structure. In the hashtag structure with hydrogen bonding, four (5,5) CNTs of length 4.46 nm (18 rings) and four linkers (C276H92N8O8) stabilized the hashtag so that the average binding energy per pincer was 118 kcal/mol.

Effect of Coulomb friction on orientational correlation and velocity distribution functions in a sheared dilute granular gas.

PubMed

Gayen, Bishakhdatta; Alam, Meheboob

2011-08-01

From particle simulations of a sheared frictional granular gas, we show that the Coulomb friction can have dramatic effects on orientational correlation as well as on both the translational and angular velocity distribution functions even in the Boltzmann (dilute) limit. The dependence of orientational correlation on friction coefficient (μ) is found to be nonmonotonic, and the Coulomb friction plays a dual role of enhancing or diminishing the orientational correlation, depending on the value of the tangential restitution coefficient (which characterizes the roughness of particles). From the sticking limit (i.e., with no sliding contact) of rough particles, decreasing the Coulomb friction is found to reduce the density and spatial velocity correlations which, together with diminished orientational correlation for small enough μ, are responsible for the transition from non-gaussian to gaussian distribution functions in the double limit of small friction (μ→0) and nearly elastic particles (e→1). This double limit in fact corresponds to perfectly smooth particles, and hence the maxwellian (gaussian) is indeed a solution of the Boltzmann equation for a frictional granular gas in the limit of elastic collisions and zero Coulomb friction at any roughness. The high-velocity tails of both distribution functions seem to follow stretched exponentials even in the presence of Coulomb friction, and the related velocity exponents deviate strongly from a gaussian with increasing friction.

On the Flow Physics of Effectively Controlled Open Cavity Flows

DTIC Science & Technology

2013-05-01

Receptivity Feedback Source 6 be more effective at reducing the surface pressure fluctuations. Zhuang et al. (2006) used leading edge microjets to alter...cavity. In a precursor to the current study, Ukeiley et al. (2008) used both microjets and spanwise-aligned slots to control the cavity flow and reduce...orientations. Two- and three-component data were acquired for laser sheet orientations aligned with the flow and perpendicular to it, respectively. A

The effects of heat treatment on physical properties and surface roughness of red-bud maple (Acer trautvetteri Medw.) wood.

PubMed

Korkut, Derya Sevim; Guller, Bilgin

2008-05-01

Heat treatment is often used to improve the dimensional stability of wood. In this study, the effects of heat treatment on physical properties and surface roughness of red-bud maple (Acer trautvetteri Medw.) wood were examined. Samples obtained from Düzce Forest Enterprises, Turkey, were subjected to heat treatment at varying temperatures and durations. The physical properties of heat-treated samples were compared against controls in order to determine their; oven-dry density, air-dry density, and swelling properties. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements, using the stylus method, were made in the direction perpendicular to the fiber. Three main roughness parameters; mean arithmetic deviation of profile (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax) obtained from the surface of wood, were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Significant differences were determined (p>0.05) between surface roughness parameters (Ra, Rz, Rmax) at three different temperatures and three periods of heat treatment. The results showed that the values of density, swelling and surface roughness decreased with increasing temperature treatment and treatment times. Red-bud maple wood could be utilized successfully by applying proper heat treatment techniques without any losses in investigated parameters. This is vital in areas, such as window frames, where working stability and surface smoothness are important factors.

Bed structure and bedload transport: Sediment grain reorientation in response to high and low flows in an experimental flume

NASA Astrophysics Data System (ADS)

Gurer, M.; Sullivan, S.; Masteller, C.

2016-12-01

Bedload is a regime of sediment transport that occurs when particles roll, hop, or bounce downstream. This mode of transport represents an important portion of the sediment load in a gravel river. Despite numerous studies focused on bedload transport, it still remains difficult to predict accurately due to the complex arrangement of riverbed particles. The formation of gravel clusters, stones being imbricated, or streamlined, and other interlocked arrangements, as well as grains armoring the bed, all tend to stabilize gravel channels and decrease bed mobility. Typically, the development of bed structure usually occurs as sediment moves downstream. However, it is unclear that gravel bed structure can be developed during weaker flows that do not generate significant sediment transport. We examine how individual sediment grains reorient themselves during low flow conditions, in the absence of sediment transport, and during high flow conditions, as bedload transport occurs. We then perform flume experiments where we expose a gravel bed to varying durations of low flow and raise the water level, simulating a flood and transporting sediment. We also compare the long-axis orientations of grains before and after each low flow period and transport. We find that sediment grains reorient themselves differently during low and high flows. During low flow, grains appear to reorient themselves with the long-axes towards cross-stream direction, or perpendicular to the flow, with longer duration flows resulting in more pronounced cross-stream orientation. During high flow, grains orient themselves with their long-axes facing downstream or parallel to the flow, similar to imbricated grains observed in the sedimentary record. Further, when transport occurs, we find that median grain orientation is strongly correlated with bedload transport rates (R^2 = 0.98). We also observe that median grain orientations more perpendicular to downstream flow result in reduced transport rates. This new result suggests that the low flow reorientation of grains perpendicular to downstream flow drives observed differences in bedload transport during high flows. We conclude that low flow periods are important for the creation of bed structure and the stabilization of gravel river channels.

Perpendicular magnetic anisotropy in amorphous NdxCo1 -x thin films studied by x-ray magnetic circular dichroism

NASA Astrophysics Data System (ADS)

Cid, R.; Alameda, J. M.; Valvidares, S. M.; Cezar, J. C.; Bencok, P.; Brookes, N. B.; Díaz, J.

2017-06-01

The origin of perpendicular magnetic anisotropy (PMA) in amorphous NdxCo1 -x thin films is investigated using x-ray magnetic circular dichroism (XMCD) spectroscopy at the Co L2 ,3 and Nd M4 ,5 edges. The magnetic orbital and spin moments of the 3 d cobalt and 4 f neodymium electrons were measured as a function of the magnetic field orientation, neodymium concentration, and temperature. In all the studied samples, the magnetic anisotropy of the neodymium subnetwork is always oriented perpendicular to the plane, whereas the anisotropy of the orbital moment of cobalt is in the basal plane. The ratio Lz/Sz of the neodymium 4 f orbitals changes with the sample orientation angle, being higher and closer to the atomic expected value at normal orientation and smaller at grazing angles. This result is well explained by assuming that the 4 f orbital is distorted by the effect of an anisotropic crystal field when it is magnetized along its hard axis, clearly indicating that the 4 f states are not rotationally invariant. The magnetic anisotropy energy associated to the neodymium subnetwork should be proportional to this distortion, which we demonstrate is accessible by applying the XMCD sum rules for the spin and intensity at the Nd M4 ,5 edges. The analysis unveils a significant portion of neodymium atoms magnetically uncoupled to cobalt, i.e., paramagnetic, confirming the inhomogeneity of the films and the presence of a highly disordered neodymium rich phase already detected by extended x-ray-absorption fine structure (EXAFS) spectroscopy. The presence of these inhomogeneities is inherent to the evaporation preparation method when the chosen concentration in the alloy is far from its eutectic concentrations. An interesting consequence of the particular way in which cobalt and neodymium segregates in this system is the enhancement of the cobalt spin moment which reaches 1.95 μB in the sample with the largest segregation.

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment

PubMed Central

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

Summary Background Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. Aim The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Materials and methods Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. Results No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. Conclusions When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs. PMID:24611090

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment.

PubMed

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs.

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

Kakinohana, Y; Toita, T; Kasuya, G

Purpose: To compare the dosimetric properties of radiochromic films with different orientation. Methods: A sheet of EBT3 film was cut into eight pieces with the following sizes: 15×15 cm2 (one piece), 5x15 cm{sup 2} (two) and 4×5 cm{sup 2} (five). A set of two EBT3 sheets was used at each dose level. Two sets were used changing the delivered doses (1 and 2 Gy). The 5×15 cm{sup 2} pieces were rotated by 90 degrees in relation to each other, such that one had landscape orientation and the other had portrait orientation. All 5×15 cm2 pieces were irradiated with their longmore » side aligned with the x-axis of the radiation field. The 15×15 cm{sup 2} pieces were irradiated rotated at 90 degrees to each other. Five pieces, (a total of ten from two sheets) were used to obtain a calibration curve. The irradiated films were scanned using an Epson ES-2200 scanner and were analyzed using ImageJ software. In this study, no correction was applied for the nonuniform scanner signal that is evident in the direction of the scanner lamp. Each film piece was scanned both in portrait and landscape orientations. Dosimetric comparisons of the beam profiles were made in terms of the film orientations (portrait and landscape) and scanner bed directions (perpendicular and parallel to the scanner movement). Results: In general, portrait orientation exhibited higher noise than landscape and was adversely affected to a great extent by the nonuniformity in the direction of the scanner lamp. A significant difference in the measured field widths between the perpendicular and parallel directions was found for both orientations. Conclusion: Without correction for the nonuniform scanner signal in the direction of the scanner lamp, a landscape orientation is preferable. A more detailed investigation is planned to evaluate quantitatively the effect of orientation on the dosimetric properties of a film.« less

Comparing position and orientation accuracy of different electromagnetic sensors for tracking during interventions.

PubMed

Nijkamp, Jasper; Schermers, Bram; Schmitz, Sander; de Jonge, Sofieke; Kuhlmann, Koert; van der Heijden, Ferdinand; Sonke, Jan-Jakob; Ruers, Theo

2016-08-01

To compare the position and orientation accuracy between using one 6-degree of freedom (DOF) electromagnetic (EM) sensor, or the position information of three 5DOF sensors within the scope of tumor tracking. The position accuracy of Northern Digital Inc Aurora 5DOF and 6DOF sensors was determined for a table-top field generator (TTFG) up to a distance of 52 cm. For each sensor 716 positions were measured for 10 s at 15 Hz. Orientation accuracy was determined for each of the orthogonal axis at the TTFG distances of 17, 27, 37 and 47 cm. For the 6DOF sensors, orientation was determined for sensors in-line with the orientation axis, and perpendicular. 5DOF orientation accuracy was determined for a theoretical 4 cm tumor. An optical tracking system was used as reference. Position RMSE and jitter were comparable between the sensors and increasing with distance. Jitter was within 0.1 cm SD within 45 cm distance to the TTFG. Position RMSE was approximately 0.1 cm up to 32 cm distance, increasing to 0.4 cm at 52 cm distance. Orientation accuracy of the 6DOF sensor was within 1[Formula: see text], except when the sensor was in-line with the rotation axis perpendicular to the TTFG plane (4[Formula: see text] errors at 47 cm). Orientation accuracy using 5DOF positions was within 1[Formula: see text] up to 37 cm and 2[Formula: see text] at 47 cm. The position and orientation accuracy of a 6DOF sensor was comparable with a sensor configuration consisting of three 5DOF sensors. To achieve tracking accuracy within 1 mm and 1[Formula: see text], the distance to the TTFG should be limited to approximately 30 cm.

Effect of metallic silver nanoparticles on the alignment and relaxation behaviour of liquid crystalline material in smectic C* phase

NASA Astrophysics Data System (ADS)

Vimal, Tripti; Kumar Gupta, Swadesh; Katiyar, Rohit; Srivastava, Atul; Czerwinski, Michal; Krup, Katarzyna; Kumar, Sandeep; Manohar, Rajiv

2017-09-01

The influence of silver nanoparticles dispersed in a Ferroelectric Liquid Crystal (FLC) on the properties of the resultant composite system has been investigated by thermal, electro-optical, and dielectric methods. We show that the concentration of thiol capped silver nanoparticles is a critical factor in governing the alignment of nanoparticles (NPs) in the host FLC. The orientation of NPs in composite samples affects the ordering of the LC (Liquid Crystal) phase and consequently changes the various phase transition temperatures of the host LC. Formation of self-assembled 2D (two dimensional) arrays of nanoparticles is observed for high concentration of dopant in the LC, oriented perpendicular to the direction of rubbing. We propose that the molecular interaction between the thiol capped NPs and LC molecules is the key factor behind such an arrangement of NPs. Orientation of NPs has affected the relaxation behaviour and various other material parameters, significantly. A noteworthy change in DC conductivity articulates our proposed idea of the formation of 2D array of NPs perpendicular to the direction of rubbing. This comprehensive study endorses the importance of dopant concentration in modifying the properties of the host LC material.

Microtubule and cellulose microfibril orientation during plant cell and organ growth.

PubMed

Chan, J

2012-07-01

In this review, I ask the question of what is the relationship between growth and the orientations of microtubules and cellulose microfibrils in plant cells. This should be a relatively simple question to answer considering that text books commonly describe microtubules and cellulose microfibrils as hoops that drive expansion perpendicular to their orientation. However, recent live imaging techniques, which allow microtubules and cellulose synthase dynamics to be imaged simultaneously with cell elongation, show that cells can elongate with nonperpendicular microtubule arrays. In this review, I look at the significance of these different microtubule arrangements for growth and cell wall architecture and how these resultant walls differ from those derived from perpendicular arrays. I also discuss how these divergent arrays in stems may be important for coordinating growth between the different cell layers. This role reveals some general features of microtubule alignment that can be used to predict the growth status of organs. In conclusion, nonperpendicular arrays demonstrate alternative ways of cell elongation that do not require hooped arrays of microtubules and cellulose microfibrils. Such nonperpendicular arrays may be required for optimal growth and strengthening of tissues. © 2011 The Author Journal of Microscopy © 2011 Royal Microscopical Society.

A geometric model for initial orientation errors in pigeon navigation.

PubMed

Postlethwaite, Claire M; Walker, Michael M

2011-01-21

All mobile animals respond to gradients in signals in their environment, such as light, sound, odours and magnetic and electric fields, but it remains controversial how they might use these signals to navigate over long distances. The Earth's surface is essentially two-dimensional, so two stimuli are needed to act as coordinates for navigation. However, no environmental fields are known to be simple enough to act as perpendicular coordinates on a two-dimensional grid. Here, we propose a model for navigation in which we assume that an animal has a simplified 'cognitive map' in which environmental stimuli act as perpendicular coordinates. We then investigate how systematic deviation of the contour lines of the environmental signals from a simple orthogonal arrangement can cause errors in position determination and lead to systematic patterns of directional errors in initial homing directions taken by pigeons. The model reproduces patterns of initial orientation errors seen in previously collected data from homing pigeons, predicts that errors should increase with distance from the loft, and provides a basis for efforts to identify further sources of orientation errors made by homing pigeons. Copyright © 2010 Elsevier Ltd. All rights reserved.

The persistence of the gravity signal in flax roots

NASA Astrophysics Data System (ADS)

Hasenstein, Karl H.

Although the presentation time of gravitropism has been studied, no data exist as to how long a reorientation stimulus affects the gravitropic response of a root. We tested the duration of gravitropic curvature in roots of Linum usitatissimum after reversing a one hour, 90 degree gravistimulus by increasing time intervals in vertical orientation before clinorotating the roots and acquiring infrared digital images. Clinorotation was performed either parallel or perpendicular to the gravity vector. Under either condition the gravistimulus affected curvature during clinorotation only between two to three minutes. Maximal curvature after one minute of vertical reorientation was 15 degrees within one hour. After three minutes in vertical orientation the observed curvature was not statistically different from vertically growing roots. In both orientations, maximum curvature occurred after 1hr. Perpendicular (horizontal) clinorotation showed decreasing curvature with increasing reorientation time. Parallel (vertical) clinorotation resulted in greater variability to the reorientation time. These data indicate that the gravity stimulus operates essentially memory free and that clinorotation affects the gravity response. Therefore all aspects of clinorotation need to be studied before an assessment of clinostats for the simulation of microgravity is possible and a time limit for memory effects of mechanostimulation can be determined.

Frequency dependence of magnetic ac loss in a Roebel cable made of YBCO on a Ni-W substrate

NASA Astrophysics Data System (ADS)

Lakshmi, L. S.; Staines, M. P.; Badcock, R. A.; Long, N. J.; Majoros, M.; Collings, E. W.; Sumption, M. D.

2010-08-01

We have investigated the frequency dependent contributions to the magnetic ac loss in a 10 strand Roebel cable with 2 mm wide non-insulated strands and a transposition length of 90 mm. This cable is made from 40 mm wide YBCO coated conductor tape manufactured by AMSC and stabilized by electroplating 25 µm thick copper on either side prior to the mechanical punching of the cable strands. The measurements were carried out in both perpendicular and parallel field orientation, at frequencies in the range of 30-200 Hz. While the loss in the perpendicular orientation is predominantly hysteretic in nature, we observe some frequency dependence of the loss when the cable approaches full flux penetration at high field amplitudes. The magnitude is consistent with eddy current losses in the copper stabilization layer. This supports the fact that the inter-strand coupling loss is not significant in this frequency range. In the parallel field orientation, the hysteresis loss in the Ni-W alloy substrate dominates, but we see an unusually strong frequency dependent contribution to the loss which we attribute to intra-strand current loops.

Shear enhanced compaction-solution bands in quartz-rich calcarenites of the Cotiella Massif (Spanish Pyrennes)

NASA Astrophysics Data System (ADS)

Tavani, Stefano; Granado, Pablo; Cantanero, Irene; Balsamo, Fabrizio; Corradetti, Amerigo; Muñoz, Josep

2017-04-01

In this contribution we describe deformation bands developed due to the interplay between shearing and mechanical and chemical compaction in Paleocene quartz-rich calcarenites. The studied structures are located in the footwall of the Cotiella Thrust (Spanish Pyrennes) and form anastomosed, mm-thick tabular bands, composed of high concentration of quartz grains. The bands strike perpendicular to the local transport direction of the regional thrust sheet, thus indicating a tectonic origin, and are organized in three sets. One set is perpendicular to the shallow-dipping bedding surface, while the other two are roughly perpendicular to each other and form an angle of 45°, in opposite directions, with the bedding. No macroscopic evidence of shearing is found along these bands. Optical microscope and SEM investigations on both undeformed and deformed rocks indicate that the high concentration of quartz within the deformation bands was caused by the localized pressure-enhanced dissolution of calcite grains, which determined the enrichment of the less soluble quartz grains. Quartz grains fracturing, fragmentation and crushing was observed along in all deformation bands, whereas cataclasis and shear occurs only along oblique oblique-to-bedding sets. All these features indicate that studied deformation bands are hybrid structures most likely developed during layer-parallel shortening. In detail, bedding perpendicular and bedding oblique structures can be interpreted as pure compaction and shear-enhanced compaction bands, respectively.

Growth of Highly c-axis Oriented and/or Epitaxial Single-Domain b-axis Oriented La5Ca9Cu24O41 Thin Films by Pulsed Laser Deposition

DTIC Science & Technology

2016-04-01

project attempted to grow La5Ca9Cu24O41 (LCCO) films on important substrates with the high- thermal -conductivity direction parallel or perpendicular...to the surface of the substrate, counting success as demonstration of b-axis or c-axis oriented LCCO films along with measurement of bulk thermal ...deposition, LCCO, La5Ca9Cu24O41, thermal conductivity, epitaxy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 24

On the orientation of stripes in fish skin patterning.

PubMed

Míguez, David G; Muñuzuri, Alberto P

2006-11-20

This paper is focused on the study of the stripes orientation in the fish skin patterns. Based on microscopic observations of the pigment cells behavior at the embryonic stage, the key aspects of the pigmentation process are implemented in an experimental reaction-diffusion system. The experiment consists of a photosensitive Turing pattern of stripes growing directionally in one direction with controlled velocity. Different growth velocities of the system rearrange the stripes in the same three possible orientations observed in the skin of the colored fishes: parallel, oblique, and perpendicular. Our results suggest that the spreading velocity of the pigment cells in the fish dermis selects the orientation in the patterning processes.

Episodic Rifting Events Within the Tjörnes Fracture Zone, an Onshore-Offshore Ridge-Transform in N-Iceland

NASA Astrophysics Data System (ADS)

Brandsdottir, B.; Magnusdottir, S.; Karson, J. A.; Detrick, R. S.; Driscoll, N. W.

2015-12-01

The multi-branched plate boundary across Iceland is made up of divergent and oblique rifts, and transform zones, characterized by entwined extensional and transform tectonics. The Tjörnes Fracture Zone (TFZ), located on the coast and offshore Northern Iceland, is a complex transform linking the northern rift zone (NVZ) on land with the Kolbeinsey Ridge offshore. Extension across TFZ is partitioned across three N-S trending rift basins; Eyjafjarðaráll, Skjálfandadjúp (SB) and Öxarfjörður and three WNW-NW oriented seismic lineaments; the Grímsey Oblique Rift, Húsavík-Flatey Faults (HFFs) and Dalvík Lineament. We compile the tectonic framework of the TFZ ridge-transform from aerial photos, satellite images, multibeam bathymetry and high-resolution seismic reflection data (Chirp). The rift basins are made up of normal faults with vertical displacements of up to 50-60 m, and post-glacial sediments of variable thickness. The SB comprises N5°W obliquely trending, eastward dipping normal faults as well as N10°E striking, westward dipping faults oriented roughly perpendicular to the N104°E spreading direction, indicative of early stages of rifting. Correlation of Chirp reflection data and tephrachronology from a sediment core within SB reveal major rifting episodes between 10-12.1 kyrs BP activating the whole basin, followed by smaller-scale fault movements throughout Holocene. Onshore faults have the same orientations as those mapped offshore and provide a basis for the interpretation of the kinematics of the faults throughout the region. These include transform parallel right-lateral, strike-slip faults separating domains dominated by spreading parallel left-lateral bookshelf faults. Shearing is most prominent along the HFFs, a system of right-lateral strike-slip faults with vertical displacement up to 15 m. Vertical fault movements reflect increased tectonic activity during early postglacial time coinciding with isostatic rebound enhancing volcanism within Iceland.

Pulmonary Microwave Ablation Near the Heart: Antenna Positioning Can Mitigate Cardiac Complications in a Porcine Model

PubMed Central

Nocerino, Elisabetta; Mason, Peter J.; Schwahn, Denise J.; Hetzel, Scott; Turnquist, Alyssa M.; Lee, Fred T.; Brace, Christopher L.

2017-01-01

Purpose To determine how close to the heart pulmonary microwave ablation can be performed without causing cardiac tissue injury or significant arrhythmia. Materials and Methods The study was performed with approval from the institutional animal care and use committee. Computed tomographic fluoroscopically guided microwave ablation of the lung was performed in 12 swine. Antennas were randomized to either parallel (180° ± 20°) or perpendicular (90° ± 20°) orientation relative to the heart surface and to distances of 0–10 mm from the heart. Ablations were performed at 65 W for 5 minutes or until a significant arrhythmia (asystole, heart block, bradycardia, supraventricular or ventricular tachycardia) developed. Heart tissue was evaluated with vital staining and histologic examination. Data were analyzed with mixed effects logistic regression, receiver operating characteristic curves, and the Fisher exact test. Results Thirty-four pulmonary microwave ablations were performed with the antenna a median distance of 4 mm from the heart in both perpendicular (n = 17) and parallel (n = 17) orientation. Significant arrhythmias developed during six (18%) ablations. Cardiac tissue injury occurred with 17 ablations (50%). Risk of arrhythmia and tissue injury decreased with increasing antenna distance from the heart with both antenna orientations. No cardiac complication occurred with a distance of greater than or equal to 4.4 mm from the heart. The ablation zone extended to the pleural surface adjacent to the heart in 71% of parallel and 17% of perpendicular ablations performed 5–10 mm from the heart. Conclusion Microwave lung ablations performed more than or equal to 5 mm from the heart were associated with a low risk of cardiac complications. © RSNA, 2016 PMID:27732159

Cross-Shear in Metal-on-Polyethylene Articulation of Orthopaedic Implants and its Relationship to Wear

PubMed Central

Schwenke, T.; Wimmer, M. A.

2013-01-01

Wear of polyethylene (UHMWPE) is dependent on cross-shear. The aim of the present study was: 1) to develop a theoretical description of cross-shear, 2) to experimentally determine the relationship between cross-shear motion and UHMWPE wear using a wheel-on-flat apparatus, and 3) to calculate the work it takes to remove a unit volume of wear for the use in advanced computational models of wear. The theoretical description of cross-shear has been based on the previously reported finding that cross-shear is maximal when movement occurs perpendicular to fibril orientation. Here, cross-shear is described with a double-sinusoidal function that uses the angle between fibril orientation and velocity vector as input, and maximum cross-shear occurs at 90° and 270°. In the experimental part of the study, friction and wear of polyethylene were plotted against increasing sliding velocity vector angles, i.e. increasing cross-shear. It was found that wear intensified with increasing cross-shear, and wear depth could be predicted well using the double-sinusoidal function for cross-shear (r2=0.983). The friction data were then used to calculate the work to remove a unit particle by integrating the frictional force over the directional sliding distance. Using the wear volumes, determined for both longitudinal and perpendicular motion directions, the work to remove a unit volume of material was qy= 8.473 × 108 J/mm3 and qx= 1.321 × 108 J/mm3, respectively. Hence, 6.4 times more work was necessary to remove a unit wear volume in the direction of principal motion (i.e. along the molecular fibril orientation) than 90° perpendicular to it. In the future, these findings will be implemented in computational models to assess wear. PMID:23794761

Seismic anisotropy and mantle creep in young orogens

USGS Publications Warehouse

Meissner, R.; Mooney, W.D.; Artemieva, I.

2002-01-01

Seismic anisotropy provides evidence for the physical state and tectonic evolution of the lithosphere. We discuss the origin of anisotropy at various depths, and relate it to tectonic stress, geotherms and rheology. The anisotropy of the uppermost mantle is controlled by the orthorhombic mineral olivine, and may result from ductile deformation, dynamic recrystallization or annealing. Anisotropy beneath young orogens has been measured for the seismic phase Pn that propagates in the uppermost mantle. This anisotropy is interpreted as being caused by deformation during the most recent thermotectonic event, and thus provides information on the process of mountain building. Whereas tectonic stress and many structural features in the upper crust are usually orientated perpendicular to the structural axis of mountain belts, Pn anisotropy is aligned parallel to the structural axis. We interpret this to indicate mountain-parallel ductile (i.e. creeping) deformation in the uppermost mantle that is a consequence of mountain-perpendicular compressive stresses. The preferred orientation of the fast axes of some anisotropic minerals, such as olivine, is known to be in the creep direction, a consequence of the anisotropy of strength and viscosity of orientated minerals. In order to explain the anisotropy of the mantle beneath young orogens we extend the concept of crustal 'escape' (or 'extrusion') tectonics to the uppermost mantle. We present rheological model calculations to support this hypothesis. Mountain-perpendicular horizontal stress (determined in the upper crust) and mountain-parallel seismic anisotropy (in the uppermost mantle) require a zone of ductile decoupling in the middle or lower crust of young mountain belts. Examples for stress and mountain-parallel Pn anisotropy are given for Tibet, the Alpine chains, and young mountain ranges in the Americas. Finally, we suggest a simple model for initiating mountain parallel creep.

Structural Analysis of Hand Drawn Bumblebee Bombus terrestris Silk

PubMed Central

Woodhead, Andrea L.; Sutherland, Tara D.; Church, Jeffrey S.

2016-01-01

Bombus terrestris, commonly known as the buff-tailed bumblebee, is native to Europe, parts of Africa and Asia. It is commercially bred for use as a pollinator of greenhouse crops. Larvae pupate within a silken cocoon that they construct from proteins produced in modified salivary glands. The amino acid composition and protein structure of hand drawn B. terrestris, silk fibres was investigated through the use of micro-Raman spectroscopy. Spectra were obtained from single fibres drawn from the larvae salivary gland at a rate of 0.14 cm/s. Raman spectroscopy enabled the identification of poly(alanine), poly(alanine-glycine), phenylalanine, tryptophan, and methionine, which is consistent with the results of amino acid analysis. The dominant protein conformation was found to be coiled coil (73%) while the β-sheet content of 10% is, as expected, lower than those reported for hornets and ants. Polarized Raman spectra revealed that the coiled coils were highly aligned along the fibre axis while the β-sheet and random coil components had their peptide carbonyl groups roughly perpendicular to the fibre axis. The protein orientation distribution is compared to those of other natural and recombinant silks. A structural model for the B. terrestris silk fibre is proposed based on these results. PMID:27447623

Multilayer Relaxation and Surface Energies of Metallic Surfaces

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Rodriguez, Agustin M.; Ferrante, John

1994-01-01

The perpendicular and parallel multilayer relaxations of fcc (210) surfaces are studied using equivalent crystal theory (ECT). A comparison with experimental and theoretical results is made for AI(210). The effect of uncertainties in the input parameters on the magnitudes and ordering of surface relaxations for this semiempirical method is estimated. A new measure of surface roughness is proposed. Predictions for the multilayer relaxations and surface energies of the (210) face of Cu and Ni are also included.

An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

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

Masters, A.; Dougherty, M. K.; Sulaiman, A. H.

A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn’s bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at amore » quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream–downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ∼100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures.« less

Nuclear resonance tomography with a toroid cavity detector

DOEpatents

Woelk, K.; Rathke, J.W.; Klingler, R.J.

1996-11-12

A toroid cavity detection system is described for determining the spectral properties and distance from a fixed point for a sample using Nuclear Magnetic Resonance. The detection system consists of a toroid with a central conductor oriented along the main axis of the toroidal cylinder and perpendicular to a static uniform magnetic field oriented along the main axis of the toroid. An rf signal is input to the central conductor to produce a magnetic field perpendicular to the central axis of the toroid and whose field strength varies as the inverse of the radius of the toroid. The toroid cavity detection system can be used to encapsulate a sample, or the detection system can be perforated to allow a sample to flow into the detection device or to place the samples in specified sample tubes. The central conductor can also be coated to determine the spectral property of the coating and the coating thickness. The sample is then subjected to the respective magnetic fields and the responses measured to determine the desired properties. 4 figs.

Nuclear resonance tomography with a toroid cavity detector

DOEpatents

Woelk, Klaus; Rathke, Jerome W.; Klingler, Robert J.

1996-01-01

A toroid cavity detection system for determining the spectral properties and distance from a fixed point for a sample using Nuclear Magnetic Resonance. The detection system consists of a toroid with a central conductor oriented along the main axis of the toroidal cylinder and perpendicular to a static uniform magnetic field oriented along the main axis of the toroid. An rf signal is inputted to the central conductor to produce a magnetic field perpendicular to the central axis of the toroid and whose field strength varies as the inverse of the radius of the toroid. The toroid cavity detection system can be used to encapsulate a sample, or the detection system can be perforated to allow a sample to flow into the detection device or to place the samples in specified sample tubes. The central conductor can also be coated to determine the spectral property of the coating and the coating thickness. The sample is then subjected to the respective magnetic fields and the responses measured to determine the desired properties.

Human Aquaporin 4 Gating Dynamics under Perpendicularly-Oriented Electric-Field Impulses: A Molecular Dynamics Study

PubMed Central

Marracino, Paolo; Liberti, Micaela; Trapani, Erika; Burnham, Christian J.; Avena, Massimiliano; Garate, José-Antonio; Apollonio, Francesca; English, Niall J.

2016-01-01

Human aquaporin 4 has been studied using molecular dynamics (MD) simulations in the absence and presence of pulses of external static electric fields. The pulses were 10 ns in duration and 0.012–0.065 V/Å in intensity acting along both directions perpendicular to the pores. Water permeability and the dipolar response of all residues of interest (including the selectivity filter) within the pores have been studied. Results showed decreased levels of water osmotic permeability within aquaporin channels during orthogonally-oriented field impulses, although care must be taken with regard to statistical certainty. This can be explained observing enhanced “dipolar flipping” of certain key residues, especially serine 211, histidine 201, arginine 216, histidine 95 and cysteine 178. These residues are placed at the extracellular end of the pore (serine 211, histidine 201, and arginine 216) and at the cytoplasm end (histidine 95 and cysteine 178), with the key role in gating mechanism, hence influencing water permeability. PMID:27428954

Formation and characterization of perpendicular mode Si ripples by glancing angle O{sub 2}{sup +} sputtering at room temperature

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

Mollick, S. A.; Ghose, D.

Off-normal low energy ion beam sputtering of solid surfaces often leads to morphological instabilities resulting in the spontaneous formation of ripple structures in nanometer length scales. In the case of Si surfaces at ambient temperature, ripple formation is found to take place normally at lower incident angles with the wave vector parallel to the ion beam direction. The absence of ripple pattern on Si surface at larger angles is due to the dominance of ion beam polishing effect. We have shown that a gentle chemical roughening of the starting surface morphology can initiate ripple pattern under grazing incidence ion beammore » sputtering (theta>64 deg. with respect to the surface normal), where the ripple wave vector is perpendicular to the ion beam direction. The characteristics of the perpendicular mode ripples are studied as a function of pristine surface roughness (2-30 nm) and projectile fluence (5x10{sup 16}-1.5x10{sup 18} O atoms cm{sup -2}). The quality of the morphological structure is assessed from the analysis of ion induced topological defects.« less

CeCo5 thin films with perpendicular anisotropy grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Sharma, S.; Hildebrandt, E.; Major, M.; Komissinskiy, P.; Radulov, I.; Alff, L.

2018-04-01

Buffer-free, highly textured (0 0 1) oriented CeCo5 thin films showing perpendicular magnetic anisotropy were synthesized on (0 0 1) Al2O3 substrates by molecular beam epitaxy. Ce exists in a mixture of Ce3+ and Ce4+ valence states as shown by X-ray photoelectron spectroscopy. The first anisotropy constant, K1, as measured by torque magnetometry was 0.82 MJ/m3 (8.2 ×106erg /cm3) . A maximum coercivity of 5.16 kOe with a negative temperature coefficient of -0.304%K-1 and a magnetization of 527.30 emu/cm3 was measured perpendicular to the film plane at 5 K. In addition, a large anisotropy of the magnetic moment of 15.5% was observed. These magnetic parameters make CeCo5 a potential candidate material for spintronic and magnetic recording applications.

The role of symmetry-breaking-induced interface anisotropy in [Fe/Pt]{sub n} multilayer films

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

Li Zhenghua; Center for Geo-environment Science, Faculty of Engineering and Resource Science, Akita University, Tegatagakuen-machi 1-1, Akita 010-8502; Xie Hailong

2011-04-01

The FePt films were deposited with [Fe/Pt]{sub n} multilayer structure on preheated Corning 1737F glass substrate using pure Fe and Pt target in a CMS-18 sputtering system. The dependence of FePt's texture and magnetic properties on the multilayer structure was investigated. The XRD patterns indicate that (111) texture is dominant for all [Fe/Pt]{sub n} (n = 8, 16, 20, 32) multilayer films. However, the measured M-H loops show that the perpendicular anisotropy is greatly enhanced in samples with n = 16, 20, and 32. The origin of the increased perpendicular anisotropy of [Fe/Pt]{sub n} multilayer films is related to themore » contributions of the interfaces, which will be analyzed using the micromagnetic models, with careful discussions of the crystalline and interface anisotropies. Finally, it is confirmed that the Fe/Pt interfaces favor the perpendicular orientation in the multilayer structure.« less

Structural investigation of Mimosa pudica Linn fibre

NASA Astrophysics Data System (ADS)

Patra, S. R.; Pattojoshi, P.; Tiwari, T. N.; Mallick, B.

2017-04-01

Sensitive plant ( Mimosa pudica Linn.) fibre is a natural fibre with electrically conductive property. Because of its electro-active sensing nature, it has been found very interesting among physicists, chemists, biologists, material scientists and technologists. So far as our knowledge is concerned; there is no report on the X-ray structure of M. pudica fibre using diffraction technique. In the present report, the M. pudica fibre has been extracted from the stem of the herb by sinking the stem in 10% NaOH solution for one week. The diffraction pattern of the fibre is found out to be cellulose-I. The effect of the fibre structure and its orientation due to different mounting have been investigated using X-ray diffraction technique. The I max of cellulose-I has been observed along (002) and (10\\overline{1)} for the perpendicular and parallel mounting of the native-fibre, respectively. Full width at half maxima of the diffraction profile turns out to be decreased with fibre orientation. Dimension of crystallite size D hkl estimated in the perpendicular mounting D_{hkl}^{ \\bot } is more as compared to that of the parallel mounting D_{hkl}^{{^{allel } }}. The smallest crystallite sizes observed in both parallel and perpendicular mounting are 18.78 and 30.78 Å respectively. It is expected that the present study may help to analyse the X-ray diffraction of fibre materials in general and natural fibres in particular.

Vacuum chamber for containing particle beams

DOEpatents

Harvey, A.

1985-11-26

A vacuum chamber for containing a charged particle beam in a rapidly changing magnetic environment comprises a ceramic pipe with conducting strips oriented along the longitudinal axis of the pipe and with circumferential conducting bands oriented perpendicular to the longitudinal axis but joined with a single longitudinal electrical connection. When both strips and bands are on the outside of the ceramic pipe, insulated from each other, a high-resistance conductive layer such as nickel can be coated on the inside of the pipe.

Parallel heater system for subsurface formations

DOEpatents

Harris, Christopher Kelvin [Houston, TX; Karanikas, John Michael [Houston, TX; Nguyen, Scott Vinh [Houston, TX

2011-10-25

A heating system for a subsurface formation is disclosed. The system includes a plurality of substantially horizontally oriented or inclined heater sections located in a hydrocarbon containing layer in the formation. At least a portion of two of the heater sections are substantially parallel to each other. The ends of at least two of the heater sections in the layer are electrically coupled to a substantially horizontal, or inclined, electrical conductor oriented substantially perpendicular to the ends of the at least two heater sections.

Analysis of multi lobe journal bearings with surface roughness using finite difference method

NASA Astrophysics Data System (ADS)

PhaniRaja Kumar, K.; Bhaskar, SUdaya; Manzoor Hussain, M.

2018-04-01

Multi lobe journal bearings are used for high operating speeds and high loads in machines. In this paper symmetrical multi lobe journal bearings are analyzed to find out the effect of surface roughnessduring non linear loading. Using the fourth order RungeKutta method, time transient analysis was performed to calculate and plot the journal centre trajectories. Flow factor method is used to evaluate the roughness and the finite difference method (FDM) is used to predict the pressure distribution over the bearing surface. The Transient analysis is done on the multi lobe journal bearings for threedifferent surface roughness orientations. Longitudinal surface roughness is more effective when compared with isotopic and traverse surface roughness.

Different Relative Orientation of Static and Alternative Magnetic Fields and Cress Roots Direction of Growth Changes Their Gravitropic Reaction

NASA Astrophysics Data System (ADS)

Sheykina, Nadiia; Bogatina, Nina

The following variants of roots location relatively to static and alternative components of magnetic field were studied. At first variant the static magnetic field was directed parallel to the gravitation vector, the alternative magnetic field was directed perpendicular to static one; roots were directed perpendicular to both two fields’ components and gravitation vector. At the variant the negative gravitropysm for cress roots was observed. At second variant the static magnetic field was directed parallel to the gravitation vector, the alternative magnetic field was directed perpendicular to static one; roots were directed parallel to alternative magnetic field. At third variant the alternative magnetic field was directed parallel to the gravitation vector, the static magnetic field was directed perpendicular to the gravitation vector, roots were directed perpendicular to both two fields components and gravitation vector; At forth variant the alternative magnetic field was directed parallel to the gravitation vector, the static magnetic field was directed perpendicular to the gravitation vector, roots were directed parallel to static magnetic field. In all cases studied the alternative magnetic field frequency was equal to Ca ions cyclotron frequency. In 2, 3 and 4 variants gravitropism was positive. But the gravitropic reaction speeds were different. In second and forth variants the gravitropic reaction speed in error limits coincided with the gravitropic reaction speed under Earth’s conditions. At third variant the gravitropic reaction speed was slowed essentially.

Dependence of Magnetic Properties of Co/Pt Multilayers on Deposition Temperature of Pt Buffer Layers

NASA Astrophysics Data System (ADS)

Shiomi, Shigeru; Nishimura, Tomotaka; Kobayashi, Tadashi; Masuda, Morio

1993-04-01

A 15-nm-thick Pt buffer layer was deposited on a glass slide at temperature Ts(Ptbuf) ranging from 30 to 300°C by e-gun evaporation. Following the cooling in vacuum to ambient temperature, Co and Pt layers have been alternately deposited on it. Very large perpendicular anisotropy and coercivity have been obtained at Ts(Ptbuf) higher than 200°C. The (111) preferred orientation of the Co/Pt multilayer as well as the Pt buffer layer became more pronounced with elevating Ts(Ptbuf), to which the enhancement of perpendicular anisotropy with elevating Ts(Ptbuf) might be ascribable.

Two-axis magnetic field sensor

NASA Technical Reports Server (NTRS)

Smith, Carl H. (Inventor); Nordman, Catherine A. (Inventor); Jander, Albrecht (Inventor); Qian, Zhenghong (Inventor)

2006-01-01

A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

Micromagnetic simulations of anisotropies in coupled and uncoupled ferromagnetic nanowire systems.

PubMed

Blachowicz, T; Ehrmann, A

2013-01-01

The influence of a variation of spatial relative orientations onto the coupling dynamics and subsequent magnetic anisotropies was modeled in ferromagnetic nanowires. The wires were analyzed in the most elementary configurations, thus, arranged in pairs perpendicular to each other, leading to one-dimensional (linear) and zero-dimensional (point-like) coupling. Different distances within each elementary pair of wires and between the pairs give rise to varying interactions between parallel and perpendicular wires, respectively. Simulated coercivities show an exchange of easy and hard axes for systems with different couplings. Additionally, two of the systems exhibit a unique switching behavior which can be utilized for developing new functionalities.

An optical microscopy study of the swelling of wet-spun films of CsDNA as a function of hydration and CsCl concentration

NASA Astrophysics Data System (ADS)

Schwenker, Megan; Marlowe, Robert; Lee, Scott; Rupprecht, Allan

2005-03-01

Highly oriented, wet-spun films of DNA expand in the direction perpendicular to the helical axis as the hydration of the film is increased. CsDNA films with a high CsCl content show an unexpected shrinkage at a relative humidity of 92%. Our most recent experiments have been to measure the perpendicular dimension of CsDNA as a function of both hydration and concentration of CsCl. Our preliminary results show that no shrinkage is observed at low contents of CsCl, showing that the CsCl plays an integral role in the shrinkage phenomenon.

Polarization-dependent DANES study on vertically-aligned ZnO nanorods

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

Sun, Chengjun; Park, Chang-In; Jin, Zhenlan

2016-05-01

The local structural and local density of states of vertically-aligned ZnO nanorods were examined by using a polarization-dependent diffraction anomalous near edge structure (DANES) measurements from c-oriented ZnO nanorods at the Zn K edge with the incident x-ray electric field parallel and perpendicular to the x-ray momentum transfer direction. Orientation-dependent local structures determined by DANES were comparable with polarization-dependent EXAFS results. Unlike other techniques, polarization-dependent DANES can uniquely describe the orientation-dependent local structural properties and the local density of states of a selected element in selected-phased crystals of compounds or mixed-phased structures.

Nanostructured carbon films with oriented graphitic planes

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

Teo, E. H. T.; Kalish, R.; Kulik, J.

2011-03-21

Nanostructured carbon films with oriented graphitic planes can be deposited by applying energetic carbon bombardment. The present work shows the possibility of structuring graphitic planes perpendicular to the substrate in following two distinct ways: (i) applying sufficiently large carbon energies for deposition at room temperature (E>10 keV), (ii) utilizing much lower energies for deposition at elevated substrate temperatures (T>200 deg. C). High resolution transmission electron microscopy is used to probe the graphitic planes. The alignment achieved at elevated temperatures does not depend on the deposition angle. The data provides insight into the mechanisms leading to the growth of oriented graphiticmore » planes under different conditions.« less

Two-stage magnetic orientation of uric acid crystals as gout initiators

NASA Astrophysics Data System (ADS)

Takeuchi, Y.; Miyashita, Y.; Mizukawa, Y.; Iwasaka, M.

2014-01-01

The present study focuses on the magnetic behavior of uric acid crystals, which are responsible for gout. Under a sub-Tesla (T)-level magnetic field, rotational motion of the crystals, which were caused by diamagnetic torque, was observed. We used horizontal magnetic fields with a maximum magnitude of 500 mT generated by an electromagnet to observe the magnetic orientation of the uric acid microcrystals by a microscope. The uric acid crystals showed a perpendicular magnetic field orientation with a minimum threshold of 130 mT. We speculate that the distinct diamagnetic anisotropy in the uric acid crystals resulted in their rotational responses.

The Effect of Crystallite Size and Texture on the Strength of MgGeO3 Post-Perovskite

NASA Astrophysics Data System (ADS)

Miyagi, Lowell

2011-06-01

In-situ radial synchrotron x-ray diffraction is used to measure lattice strain and lattice preferred orientation (texture) in MgGeO3 post-perovskite synthesized and deformed in the diamond anvil cell up to 135 GPa. Lattice strains are used to calculate differential stress supported by the sample and can provide a lower bounds estimate on yield strength. MgGeO3 post-perovskite synthesized from the enstatite phase exhibits a weak transformation texture of (100) planes at high angles to the direction of compression. In a sample with larger crystallites, pressure increase and deformation results in (001) lattice planes orienting nearly perpendicular to compression, consistent with dominant (001) slip. In another sample with smaller crystallites it is difficult to induce texture change, and differential stress is higher than in the sample with larger crystallites. When MgGeO3 post-perovskite is synthesized from the perovskite phase a different transformation texture of (001) planes at high angles to compression is observed. This sample is able to support large differential stress as the direction perpendicular to the (001) plane is a plastically hard orientation for MgGeO3 post-perovskite. This work was supported by the Carnegie DOE Alliance Center and a Bateman fellowship at Yale University.

Characterization of Interactions between Curcumin and Different Types of Lipid Bilayers by Molecular Dynamics Simulation.

PubMed

Lyu, Yuan; Xiang, Ning; Mondal, Jagannath; Zhu, Xiao; Narsimhan, Ganesan

2018-03-01

Curcumin (CUR) is a natural food ingredient with known ability to target microbial cell membrane. In this study, the interactions of CUR with different types of model lipid bilayers (POPE, POPG, POPC, DOPC, and DPPE), mixtures of model lipid bilayers (POPE/POPG), and biological membrane mimics (Escherichia coli and yeast) were investigated by all-atom explicit solvent molecular dynamics (MD) simulation. CUR readily inserts into different types of model lipid bilayer systems in the liquid crystalline state, staying in the lipid tails region near the interface of lipid head and lipid tail. Parallel orientation to the membrane surface is found to be more probable than perpendicular for CUR, as indicated by the tilt angle distribution. This orientation preference is less significant as the fraction of POPE is increased in the system, likely due to the better water solvation of perpendicular orientation in the POPE bilayer. In E. coli and yeast bilayers, tilt angle distributions were similar to that for POPE/POPG mixed bilayer, with water hydration number around CUR for the former being higher. Insertion of CUR resulted in membrane thinning. The results from these simulations provide insights into the possible differences in membrane disrupting activity of CUR against different types of microorganisms.

Precursor Wave Emission Enhanced by Weibel Instability in Relativistic Shocks

NASA Astrophysics Data System (ADS)

Iwamoto, Masanori; Amano, Takanobu; Hoshino, Masahiro; Matsumoto, Yosuke

2018-05-01

We investigated the precursor wave emission efficiency in magnetized purely perpendicular relativistic shocks in pair plasmas. We extended our previous study to include the dependence of upstream magnetic field orientations. We performed two-dimensional particle-in-cell simulations and focused on two magnetic field orientations: the magnetic field in the simulation plane (i.e., in-plane configuration) and that perpendicular to the simulation plane (i.e., out-of-plane configuration). Our simulations in the in-plane configuration demonstrated that not only extraordinary but also ordinary mode waves are excited. We quantified the emission efficiency as a function of the magnetization parameter σ e and found that the large-amplitude precursor waves are emitted for a wide range of σ e . We found that especially at low σ e , the magnetic field generated by Weibel instability amplifies the ordinary mode wave power. The amplitude is large enough to perturb the upstream plasma, and transverse density filaments are generated as in the case of the out-of-plane configuration investigated in the previous study. We confirmed that our previous conclusion holds regardless of upstream magnetic field orientations with respect to the two-dimensional simulation plane. We discuss the precursor wave emission in three dimensions and the feasibility of wakefield acceleration in relativistic shocks based on our results.

Dielectric modelling of cell division for budding and fission yeast

NASA Astrophysics Data System (ADS)

Asami, Koji; Sekine, Katsuhisa

2007-02-01

The frequency dependence of complex permittivity or the dielectric spectrum of a system including a cell in cell division has been simulated by a numerical technique based on the three-dimensional finite difference method. Two different types of cell division characteristic of budding and fission yeast were examined. The yeast cells are both regarded as a body of rotation, and thus have anisotropic polarization, i.e. the effective permittivity of the cell depends on the orientation of the cell to the direction of an applied electric field. In the perpendicular orientation, where the rotational axis of the cell is perpendicular to the electric field direction, the dielectric spectra for both yeast cells included one dielectric relaxation and its intensity depended on the cell volume. In the parallel orientation, on the other hand, two dielectric relaxations appeared with bud growth for budding yeast and with septum formation for fission yeast. The low-frequency relaxation was shifted to a lower frequency region by narrowing the neck between the bud and the mother cell for budding yeast and by increasing the degree of septum formation for fission yeast. After cell separation, the low-frequency relaxation disappeared. The simulations well interpreted the oscillation of the relative permittivity of culture broth found for synchronous cell growth of budding yeast.

Molecular dynamics simulations of collagen adsorption onto grooved rutile surface: the effects of groove width.

PubMed

Chen, Mingjun; Zheng, Ting; Wu, Chunya; Xing, Cheng

2014-09-01

The early adsorption stages of collagen onto nano-grooved rutile surface without hydroxylation were studied using molecular dynamics and steered MD simulations. On the basis of plane rutile (110), two kinds of models have been adopted: single groove and parallel grooves along [1-11] crystal orientation with various width dimensions. Initially, collagens were parallel or perpendicular to the groove orientation, respectively, in order to investigate the influence of groove width on collagen adsorption. The simulation result suggests that surface grooves could exert a strong effect on collagen adsorption: when collagen was parallel to the groove direction, adsorption was favored if the groove width matched well with the dimension of collagen. However, adsorption strength may decrease as the groove width expanded. As for the condition of collagen perpendicular to the groove orientation, collagen was difficult to bend and insert into grooves in the free adsorption procedure. But the steered MD simulation results reveal that more energy was consumed for collagen to insert into narrower grooves which may be interpreted as strong barrier for adsorption. We believe that adsorption will be favored if appropriate dimension match between dimension of collagen and the groove width was approached. Copyright © 2014 Elsevier B.V. All rights reserved.

The Map in Our Head Is Not Oriented North: Evidence from a Real-World Environment.

PubMed

Brunyé, Tad T; Burte, Heather; Houck, Lindsay A; Taylor, Holly A

2015-01-01

Like most physical maps, recent research has suggested that cognitive maps of familiar environments may have a north-up orientation. We demonstrate that north orientation is not a necessary feature of cognitive maps and instead may arise due to coincidental alignment between cardinal directions and the built and natural environment. Experiment 1 demonstrated that pedestrians have difficulty pointing north while navigating a familiar real-world environment with roads, buildings, and green spaces oriented oblique to cardinal axes. Instead, north estimates tended to be parallel or perpendicular to roads. In Experiment 2, participants did not demonstrate privileged memory access when oriented toward north while making relative direction judgments. Instead, retrieval was fastest and most accurate when orientations were aligned with roads. In sum, cognitive maps are not always oriented north. Rather, in some real-world environments they can be oriented with respect to environment-specific features, serving as convenient reference systems for organizing and using spatial memory.

Electrodeposition of ZnO nanorod arrays on ZnO substrate with tunable orientation and optical properties.

PubMed

Jehl, Z; Rousset, J; Donsanti, F; Renou, G; Naghavi, N; Lincot, D

2010-10-01

The electrodeposition of ZnO nanorods on ZnO:Al films with different orientations is reported. The influence of the total charge exchanged during electrodeposition on the nanorod's geometry (length, diameter, aspect ratio and surface density) and the optical transmission properties of the nanorod arrays is studied on a [0001]-oriented ZnO:Al substrate. The nanorods are highly vertically oriented along the c axis, following the lattice matching with the substrate. The growth on a [1010] and [1120] ZnO:Al-oriented substrate with c axis parallel to the substrate leads to a systematic deviation angle of 55 degrees from the perpendicular direction. This finding has been explained by the occurrence of a minority orientation with the [1011] planes parallel to the surface, with a preferential growth on corresponding [0001] termination. Substrate crystalline orientation is thereby found to be a major parameter in finely tuning the orientation of the nanorod array. This new approach allows us to optimize the light scattering properties of the films.

Impact of a high magnetic field on the orientation of gravitactic unicellular organisms--a critical consideration about the application of magnetic fields to mimic functional weightlessness.

PubMed

Hemmersbach, Ruth; Simon, Anja; Waßer, Kai; Hauslage, Jens; Christianen, Peter C M; Albers, Peter W; Lebert, Michael; Richter, Peter; Alt, Wolfgang; Anken, Ralf

2014-03-01

The gravity-dependent behavior of Paramecium biaurelia and Euglena gracilis have previously been studied on ground and in real microgravity. To validate whether high magnetic field exposure indeed provides a ground-based facility to mimic functional weightlessness, as has been suggested earlier, both cell types were observed during exposure in a strong homogeneous magnetic field (up to 30 T) and a strong magnetic field gradient. While swimming, Paramecium cells were aligned along the magnetic field lines; orientation of Euglena was perpendicular, demonstrating that the magnetic field determines the orientation and thus prevents the organisms from the random swimming known to occur in real microgravity. Exposing Astasia longa, a flagellate that is closely related to Euglena but lacks chloroplasts and the photoreceptor, as well as the chloroplast-free mutant E. gracilis 1F, to a high magnetic field revealed no reorientation to the perpendicular direction as in the case of wild-type E. gracilis, indicating the existence of an anisotropic structure (chloroplasts) that determines the direction of passive orientation. Immobilized Euglena and Paramecium cells could not be levitated even in the highest available magnetic field gradient as sedimentation persisted with little impact of the field on the sedimentation velocities. We conclude that magnetic fields are not suited as a microgravity simulation for gravitactic unicellular organisms due to the strong effect of the magnetic field itself, which masks the effects known from experiments in real microgravity.

Anisotropic evaluation of synthetic surgical meshes.

PubMed

Saberski, E R; Orenstein, S B; Novitsky, Y W

2011-02-01

The material properties of meshes used in hernia repair contribute to the overall mechanical behavior of the repair. The anisotropic potential of synthetic meshes, representing a difference in material properties (e.g., elasticity) in different material axes, is not well defined to date. Haphazard orientation of anisotropic mesh material can contribute to inconsistent surgical outcomes. We aimed to characterize and compare anisotropic properties of commonly used synthetic meshes. Six different polypropylene (Trelex(®), ProLite™, Ultrapro™), polyester (Parietex™), and PTFE-based (Dualmesh(®), Infinit) synthetic meshes were selected. Longitudinal and transverse axes were defined for each mesh, and samples were cut in each axis orientation. Samples underwent uniaxial tensile testing, from which the elastic modulus (E) in each axis was determined. The degree of anisotropy (λ) was calculated as a logarithmic expression of the ratio between the elastic modulus in each axis. Five of six meshes displayed significant anisotropic behavior. Ultrapro™ and Infinit exhibited approximately 12- and 20-fold differences between perpendicular axes, respectively. Trelex(®), ProLite™, and Parietex™ were 2.3-2.4 times. Dualmesh(®) was the least anisotropic mesh, without marked difference between the axes. Anisotropy of synthetic meshes has been underappreciated. In this study, we found striking differences between elastic properties of perpendicular axes for most commonly used synthetic meshes. Indiscriminate orientation of anisotropic mesh may adversely affect hernia repairs. Proper labeling of all implants by manufacturers should be mandatory. Understanding the specific anisotropic behavior of synthetic meshes should allow surgeons to employ rational implant orientation to maximize outcomes of hernia repair.

Model-independent analysis of the orientation of fluorescent probes with restricted mobility in muscle fibers.

PubMed Central

Dale, R E; Hopkins, S C; an der Heide, U A; Marszałek, T; Irving, M; Goldman, Y E

1999-01-01

The orientation of proteins in ordered biological samples can be investigated using steady-state polarized fluorescence from probes conjugated to the protein. A general limitation of this approach is that the probes typically exhibit rapid orientational motion ("wobble") with respect to the protein backbone. Here we present a method for characterizing the extent of this wobble and for removing its effects from the available information about the static orientational distribution of the probes. The analysis depends on four assumptions: 1) the probe wobble is fast compared with the nanosecond time scale of its excited-state decay; 2) the orientational distributions of the absorption and emission transition dipole moments are cylindrically symmetrical about a common axis c fixed in the protein; 3) protein motions are negligible during the excited-state decay; 4) the distribution of c is cylindrically symmetrical about the director of the experimental sample. In a muscle fiber, the director is the fiber axis, F. All of the information on the orientational order of the probe that is available from measurements of linearly polarized fluorescence is contained in five independent polarized fluorescence intensities measured with excitation and emission polarizers parallel or perpendicular to F and with the propagation axis of the detected fluorescence parallel or perpendicular to that of the excitation. The analysis then yields the average second-rank and fourth-rank order parameters ( and ) of the angular distribution of c relative to F, and and , the average second-rank order parameters of the angular distribution for wobble of the absorption and emission transition dipole moments relative to c. The method can also be applied to other cylindrically ordered systems such as oriented lipid bilayer membranes and to processes slower than fluorescence that may be observed using longer-lived optically excited states. PMID:10049341

An Explanation for Bends of 1-Dimensional Nanorods

NASA Astrophysics Data System (ADS)

Mukaida, Masashi; Ichinose, Ataru; Mele, Paolo; Mtsumoto, Kaname; Horii, Shigeru; Yoshida, Yutaka

Growth of artificial pinning centers (APCs) in YBa2Cu3O7-J (YBCO) films are discussed. The APCs used in this research are BaZrO3 and BaSnO3 nanorods which are reported by Mele et al. TEM images show these nanorods graduallybend accordinglywith approachingtoasurfaceof films. This featureshowedagrowth patternlikeafirework. Weexplainthe featureofthe nanorodsas follows;Atanearlygrowth stage, filmsgrowinalayerbylayergrowth mode. The surface of the films is flat and very smooth. After the early growth stage, the film surface gradually becomes rough, indicating the film grows in a Stranski-Krastanov growth mode. This roughness was caused by a spiral growth of films with manysteps. At the step of YBCO films, nanorod materials such as BaZrO3 are supplied from one direction. Then, the center of nanorods sifts to the same direction of the step flow. Then, the nanorods bend to the edge of the grains in the films. As a grain in spiral growth had a convex surface, nanorods bent to the direction perpendicular to the grain surface. Finally, nanorods in rough grains form firework structures.

Surface recrystallization of polyethylene extended-chain crystals.

PubMed

Wunderlich, B; Melillo, L

1966-12-09

Rough fracture surfaces of extended-chain polyethylene crystals become unstable at temperatures below the bulk melting point. There is no way for the extended chains, which are up to 20,000 methylene units long, to change position without collapse. As a result, the rough surfaces smooth out on heating by covering themselves with oriented folded-chain lamellae.

The relation between the column density structures and the magnetic field orientation in the Vela C molecular complex

NASA Astrophysics Data System (ADS)

Soler, J. D.; Ade, P. A. R.; Angilè, F. E.; Ashton, P.; Benton, S. J.; Devlin, M. J.; Dober, B.; Fissel, L. M.; Fukui, Y.; Galitzki, N.; Gandilo, N. N.; Hennebelle, P.; Klein, J.; Li, Z.-Y.; Korotkov, A. L.; Martin, P. G.; Matthews, T. G.; Moncelsi, L.; Netterfield, C. B.; Novak, G.; Pascale, E.; Poidevin, F.; Santos, F. P.; Savini, G.; Scott, D.; Shariff, J. A.; Thomas, N. E.; Tucker, C. E.; Tucker, G. S.; Ward-Thompson, D.

2017-07-01

We statistically evaluated the relative orientation between gas column density structures, inferred from Herschel submillimetre observations, and the magnetic field projected on the plane of sky, inferred from polarized thermal emission of Galactic dust observed by the Balloon-borne Large-Aperture Submillimetre Telescope for Polarimetry (BLASTPol) at 250, 350, and 500 μm, towards the Vela C molecular complex. First, we find very good agreement between the polarization orientations in the three wavelength-bands, suggesting that, at the considered common angular resolution of 3.´0 that corresponds to a physical scale of approximately 0.61 pc, the inferred magnetic field orientation is not significantly affected by temperature or dust grain alignment effects. Second, we find that the relative orientation between gas column density structures and the magnetic field changes progressively with increasing gas column density, from mostly parallel or having no preferred orientation at low column densities to mostly perpendicular at the highest column densities. This observation is in agreement with previous studies by the Planck collaboration towards more nearby molecular clouds. Finally, we find a correspondencebetween (a) the trends in relative orientation between the column density structures and the projected magnetic field; and (b) the shape of the column density probability distribution functions (PDFs). In the sub-regions of Vela C dominated by one clear filamentary structure, or "ridges", where the high-column density tails of the PDFs are flatter, we find a sharp transition from preferentially parallel or having no preferred relative orientation at low column densities to preferentially perpendicular at highest column densities. In the sub-regions of Vela C dominated by several filamentary structures with multiple orientations, or "nests", where the maximum values of the column density are smaller than in the ridge-like sub-regions and the high-column density tails of the PDFs are steeper, such a transition is also present, but it is clearly less sharp than in the ridge-like sub-regions. Both of these results suggest that the magnetic field is dynamically important for the formation of density structures in this region.

TH-CD-BRA-07: MRI-Linac Dosimetry: Parameters That Change in a Magnetic Field

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

O’Brien, D. J.; Sawakuchi, G. O.

Purpose: In MRI-linac integrated systems, the presence of the magnetic (B-)field has a large impact of the dose-distribution and the dose-responses of detectors; yet established protocols and previous experience may lead to assumptions about the commissioning process that are no longer valid. This study quantifies parameters that change when performing dosimetry with an MRI-linac including beam quality specifiers and the effective-point-of-measurement (EPOM) of ionization chambers. Methods: We used the Geant4 Monte Carlo code for this work with physics parameters that pass the Fano cavity test to within 0.1% for the simulated conditions with and without a 1.5 T B-field. Amore » point source model with the energy distribution of an MRI-linac beam was used with and without the B-field to calculate the beam quality specifiers %dd(10)× and TPR{sup 20}{sub 10}, the variation of chamber response with orientation and the how the B-field affects the EPOM of ionization chambers by comparing depth-dose curves calculated in water to those generated by a model PTW30013 Farmer chamber. Results: The %dd(10)× changes by over 2% in the presence of the B-field while the TPR{sup 20}{sub 10} is unaffected. Ionization chamber dose-response is known to depend on the orientation w.r.t. the B-field, but two alternative perpendicular orientations (anti-parallel to each other) also differ in dose-response by over 1%. The B-field shifts the EPOM downstream (closer to the chamber center) but it is also shifted laterally by 0.27 times the chamber’s cavity radius. Conclusion: The EPOM is affected by the B-field and it even shifts laterally. The relationship between %dd(10)× and the Spencer-Attix stopping powers is also changed. Care must be taken when using chambers perpendicular to the field as the dose-response changes depending on which perpendicular orientation is used. All of these effects must be considered when performing dosimetry in B-fields and should be accounted for in future dosimetry protocols. This project was partially funded by Elekta Ltd.« less

Ion acceleration by multiple reflections at Martian bow shock

NASA Astrophysics Data System (ADS)

Yamauchi, M.; Futaana, Y.; Fedorov, A.; Frahm, R. A.; Dubinin, E.; Lundin, R.; Sauvaud, J.-A.; Winningham, J. D.; Barabash, S.; Holmström, M.

2012-02-01

The ion mass analyzer (IMA) on board Mars Express revealed bundled structures of ions in the energy domain within a distance of a proton gyroradius from the Martian bow shock. Seven prominent traversals during 2005 were examined when the energy-bunched structure was observed together with pick-up ions of exospheric origin, the latter of which is used to determine the local magnetic field orientation from its circular trajectory in velocity space. These seven traversals include different bow shock configurations: (a) quasi-perpendicular shock with its specular direction of the solar wind more perpendicular to the magnetic field (QT), (b) quasi-perpendicular shock with its specular reflection direction of the solar wind more along the magnetic field (FS), and (c) quasi-parallel (QL) shock. In all seven cases, the velocity components of the energy-bunched structure are consistent with multiple specular reflections of the solar wind at the bow shock up to at least two reflections. The accelerated solar wind ions after two specular reflections have large parallel components with respect to the magnetic field for both QL cases whereas the field-aligned speed is much smaller than the perpendicular speed for all QT cases.

Dune growth under multidirectional wind regimes

NASA Astrophysics Data System (ADS)

Gadal, C.; Rozier, O.; Claudin, P.; Courrech Du Pont, S.; Narteau, C.

2017-12-01

Under unidirectional wind regimes, flat sand beds become unstable to produce periodic linear dunes, commonly called transverse dunes because their main ridges are oriented perpendicular to the air flow. In areas of low sediment availability, the same interactions between flow, transport and topography produce barchan dunes, isolated sand-pile migrating over long distances with a characteristic crescentic shape. For the last fifteen years, barchan dunes and the instability at the origin of transverse dunes have been the subject of numerous studies that have identified a set of characteristic length and time scales with respect to the physical properties of both grains and fluid. This is not the case for dunes developing under multidirectional wind regimes. Under these conditions, dune orientation is measured with respect to the direction of the resultant sand flux. Depending on the wind regime, dunes do not always line up perpendicularly to the resultant sand flux, but can also be at an oblique angle or even parallel to it. These oblique and longitudinal dunes are ubiquitous in all deserts on Earth and planetary bodies because of the seasonal variability of wind orientation. They are however poorly constrained by observations and there is still no complete theoretical framework providing a description of their orientation and initial wavelength. Here, we extend the linear stability analysis of a flat sand of bed done in two dimensions for a unidirectional flow to three dimensions and multidirectional flow regimes. We are able to recover transitions from transverse to oblique or longitudinal dune patterns according to changes in wind regimes. We besides give a prediction for the initial dune wavelength. Our results compare well to previous theory of dune orientation and to field, experimental and numerical data.

Indentation damage and mechanical properties of human enamel and dentin.

PubMed

Xu, H H; Smith, D T; Jahanmir, S; Romberg, E; Kelly, J R; Thompson, V P; Rekow, E D

1998-03-01

Understanding the mechanical properties of human teeth is important to clinical tooth preparation and to the development of "tooth-like" restorative materials. Previous studies have focused on the macroscopic fracture behavior of enamel and dentin. In the present study, we performed indentation studies to understand the microfracture and deformation and the microcrack-microstructure interactions of teeth. It was hypothesized that crack propagation would be influenced by enamel rods and the dentino-enamel junction (DEJ), and the mechanical properties would be influenced by enamel rod orientation and tooth-to-tooth variation. Twenty-eight human third molars were used for the measurement of hardness, fracture toughness, elastic modulus, and energy absorbed during indentation. We examined the effect of enamel rod orientation by propagating cracks in the occlusal surface, and in the axial section in directions parallel and perpendicular to the occlusal surface. The results showed that the cracks in the enamel axial section were significantly longer in the direction perpendicular to the occlusal surface than parallel. The cracks propagating toward the DEJ were always arrested and unable to penetrate dentin. The fracture toughness of enamel was not single-valued but varied by a factor of three as a function of enamel rod orientation. The elastic modulus of enamel showed a significant difference between the occlusal surface and the axial section. It is concluded that the cracks strongly interact with the DEJ and the enamel rods, and that the mechanical properties of teeth are functions of microstructural orientations; hence, single values of properties (e.g., a single toughness value or a single modulus value) should not be used without information on microstructural orientation.

Protein denaturants at aqueous-hydrophobic interfaces: self-consistent correlation between induced interfacial fluctuations and denaturant stability at the interface.

PubMed

Cui, Di; Ou, Shu-Ching; Patel, Sandeep

2015-01-08

The notion of direct interaction between denaturing cosolvent and protein residues has been proposed in dialogue relevant to molecular mechanisms of protein denaturation. Here we consider the correlation between free energetic stability and induced fluctuations of an aqueous-hydrophobic interface between a model hydrophobically associating protein, HFBII, and two common protein denaturants, guanidinium cation (Gdm(+)) and urea. We compute potentials of mean force along an order parameter that brings the solute molecule close to the known hydrophobic region of the protein. We assess potentials of mean force for different relative orientations between the protein and denaturant molecule. We find that in both cases of guanidinium cation and urea relative orientations of the denaturant molecule that are parallel to the local protein-water interface exhibit greater stability compared to edge-on or perpendicular orientations. This behavior has been observed for guanidinium/methylguanidinium cations at the liquid-vapor interface of water, and thus the present results further corroborate earlier findings. Further analysis of the induced fluctuations of the aqueous-hydrophobic interface upon approach of the denaturant molecule indicates that the parallel orientation, displaying a greater stability at the interface, also induces larger fluctuations of the interface compared to the perpendicular orientations. The correlation of interfacial stability and induced interface fluctuation is a recurring theme for interface-stable solutes at hydrophobic interfaces. Moreover, observed correlations between interface stability and induced fluctuations recapitulate connections to local hydration structure and patterns around solutes as evidenced by experiment (Cooper et al., J. Phys. Chem. A 2014, 118, 5657.) and high-level ab initio/DFT calculations (Baer et al., Faraday Discuss 2013, 160, 89).

Protein Denaturants at Aqueous–Hydrophobic Interfaces: Self-Consistent Correlation between Induced Interfacial Fluctuations and Denaturant Stability at the Interface

PubMed Central

2015-01-01

The notion of direct interaction between denaturing cosolvent and protein residues has been proposed in dialogue relevant to molecular mechanisms of protein denaturation. Here we consider the correlation between free energetic stability and induced fluctuations of an aqueous–hydrophobic interface between a model hydrophobically associating protein, HFBII, and two common protein denaturants, guanidinium cation (Gdm+) and urea. We compute potentials of mean force along an order parameter that brings the solute molecule close to the known hydrophobic region of the protein. We assess potentials of mean force for different relative orientations between the protein and denaturant molecule. We find that in both cases of guanidinium cation and urea relative orientations of the denaturant molecule that are parallel to the local protein–water interface exhibit greater stability compared to edge-on or perpendicular orientations. This behavior has been observed for guanidinium/methylguanidinium cations at the liquid–vapor interface of water, and thus the present results further corroborate earlier findings. Further analysis of the induced fluctuations of the aqueous–hydrophobic interface upon approach of the denaturant molecule indicates that the parallel orientation, displaying a greater stability at the interface, also induces larger fluctuations of the interface compared to the perpendicular orientations. The correlation of interfacial stability and induced interface fluctuation is a recurring theme for interface-stable solutes at hydrophobic interfaces. Moreover, observed correlations between interface stability and induced fluctuations recapitulate connections to local hydration structure and patterns around solutes as evidenced by experiment (Cooper et al., J. Phys. Chem. A2014, 118, 5657.) and high-level ab initio/DFT calculations (Baer et al., Faraday Discuss2013, 160, 89). PMID:25536388

Microscopic vertical orientation of nano-interspaced graphene architectures in deposit films as electrodes for enhanced supercapacitor performance

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

Jang, Gyoung Gug; Song, Bo; Li, Liyi

This paper reported a novel two-step process to fabricate high-performance supercapacitor films that contain microscale domains of nano-interspaced, re-stacked graphene sheets oriented perpendicular to the surface of current collector substrate, i.e., carbon fiber paper. In the two-step process, we first used ligand molecules to modify the surface of graphene oxide (GO) sheets and manipulate the interspacing between the re-stacked GO sheets. The ligand-modified GOs, i.e., m-GOs, were then reduced to obtain more conductive graphene (m-rGO), where X-ray diffraction measurement results indicated well-controlled interlayer spacing between the restacked m-rGO sheets up to 1 nm. The typical lateral dimension of the restackedmore » m-rGO sheets were ~40 µm. Then, electrical field was introduced during m-rGO slurry deposition process to induce the vertical orientation of the m-rGO sheets/stacks in the film deposit. The direct current electrical field induced the orientation of the domains of m-rGO stacks along the direction perpendicular to the surface of deposit film, i.e., direction of electric field. Also, the applied electric field increased the interlayer spacing further, which should enhance the diffusion and accessibility of electrolyte ions. As compared with the traditionally deposited “control” films, the field-processed film deposits that contain oriented structure of graphene sheets/stacks have shown up to ~1.6 times higher values in capacitance (430 F/g at 0.5 A/g) and ~67% reduction in equivalent series resistance. Finally, the approach of using electric field to tailor the microscopic architecture of graphene-based deposit films is effective to fabricate film electrodes for high performance supercapacitors.« less

Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes.

PubMed

Wang, Yong-Lei; Golets, Mikhail; Li, Bin; Sarman, Sten; Laaksonen, Aatto

2017-02-08

Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P 6,6,6,14 ][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P 6,6,6,14 ] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P 6,6,6,14 ] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P 6,6,6,14 ][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P 6,6,6,14 ] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm 2 ), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P 6,6,6,14 ] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.

Microscopic vertical orientation of nano-interspaced graphene architectures in deposit films as electrodes for enhanced supercapacitor performance

DOE PAGES

Jang, Gyoung Gug; Song, Bo; Li, Liyi; ...

2016-12-14

This paper reported a novel two-step process to fabricate high-performance supercapacitor films that contain microscale domains of nano-interspaced, re-stacked graphene sheets oriented perpendicular to the surface of current collector substrate, i.e., carbon fiber paper. In the two-step process, we first used ligand molecules to modify the surface of graphene oxide (GO) sheets and manipulate the interspacing between the re-stacked GO sheets. The ligand-modified GOs, i.e., m-GOs, were then reduced to obtain more conductive graphene (m-rGO), where X-ray diffraction measurement results indicated well-controlled interlayer spacing between the restacked m-rGO sheets up to 1 nm. The typical lateral dimension of the restackedmore » m-rGO sheets were ~40 µm. Then, electrical field was introduced during m-rGO slurry deposition process to induce the vertical orientation of the m-rGO sheets/stacks in the film deposit. The direct current electrical field induced the orientation of the domains of m-rGO stacks along the direction perpendicular to the surface of deposit film, i.e., direction of electric field. Also, the applied electric field increased the interlayer spacing further, which should enhance the diffusion and accessibility of electrolyte ions. As compared with the traditionally deposited “control” films, the field-processed film deposits that contain oriented structure of graphene sheets/stacks have shown up to ~1.6 times higher values in capacitance (430 F/g at 0.5 A/g) and ~67% reduction in equivalent series resistance. Finally, the approach of using electric field to tailor the microscopic architecture of graphene-based deposit films is effective to fabricate film electrodes for high performance supercapacitors.« less

Parallel and Perpendicular Alignment of Anisotropic Particles in Free Liquid Microjets and Emerging Microdroplets.

PubMed

Schlenk, Mathias; Hofmann, Eddie; Seibt, Susanne; Rosenfeldt, Sabine; Schrack, Lukas; Drechsler, Markus; Rothkirch, Andre; Ohm, Wiebke; Breu, Josef; Gekle, Stephan; Förster, Stephan

2018-04-24

Liquid microjets play a key role in fiber spinning, inkjet printing, and coating processes. In all of these applications, the liquid jets carry dispersed particles whose spatial and orientational distributions within the jet critically influence the properties of the fabricated structures. Despite its importance, there is currently no knowledge about the orientational distribution of particles within microjets and droplets. Here, we demonstrate a microfluidic device that allows to determine the local particle distribution and orientation by X-ray scattering. Using this methodology, we discovered unexpected changes in the particle orientation upon exiting the nozzle to form a free jet, and upon jet break-up into droplets, causing an unusual biaxial particle orientation. We show how flow and aspect ratio determine the flow orientation of anisotropic particles. Furthermore, we demonstrate that the observed phenomena are a general characteristic of anisotropic particles. Our findings greatly enhance our understanding of particle orientation in free jets and droplets and provide a rationale for controlling particle alignment in liquid jet-based fabrication methodologies.

Image BOSS: a biomedical object storage system

NASA Astrophysics Data System (ADS)

Stacy, Mahlon C.; Augustine, Kurt E.; Robb, Richard A.

1997-05-01

Researchers using biomedical images have data management needs which are oriented perpendicular to clinical PACS. The image BOSS system is designed to permit researchers to organize and select images based on research topic, image metadata, and a thumbnail of the image. Image information is captured from existing images in a Unix based filesystem, stored in an object oriented database, and presented to the user in a familiar laboratory notebook metaphor. In addition, the ImageBOSS is designed to provide an extensible infrastructure for future content-based queries directly on the images.

Airborne observed solar elevation and row direction effects on the near-IR/red ratio of cotton

NASA Technical Reports Server (NTRS)

Millard, J. P.; Jackson, R. D.; Goettelman, R. C.; Leroy, M. J. (Principal Investigator)

1981-01-01

An airborne multispectral scanner was used to obtain data over two adjacent cotton fields having rows perpendicular to one another, at three times of day (different solar elevations), and on two dates (different plant size). The near IR/red ratios were displayed in image form, so that within-field variations and differences between fields could be easily assessed. The ratio varied with changing Sun elevation for north-south oriented rows, but no variation was detected for east-west oriented rows.

Structural control of ultra-fine CoPt nanodot arrays via electrodeposition process

NASA Astrophysics Data System (ADS)

Wodarz, Siggi; Hasegawa, Takashi; Ishio, Shunji; Homma, Takayuki

2017-05-01

CoPt nanodot arrays were fabricated by combining electrodeposition and electron beam lithography (EBL) for the use of bit-patterned media (BPM). To achieve precise control of deposition uniformity and coercivity of the CoPt nanodot arrays, their crystal structure and magnetic properties were controlled by controlling the diffusion state of metal ions from the initial deposition stage with the application of bath agitation. Following bath agitation, the composition gradient of the CoPt alloy with thickness was mitigated to have a near-ideal alloy composition of Co:Pt =80:20, which induces epitaxial-like growth from Ru substrate, thus resulting in the improvement of the crystal orientation of the hcp (002) structure from its initial deposition stages. Furthermore, the cross-sectional transmission electron microscope (TEM) analysis of the nanodots deposited with bath agitation showed CoPt growth along its c-axis oriented in the perpendicular direction, having uniform lattice fringes on the hcp (002) plane from the Ru underlayer interface, which is a significant factor to induce perpendicular magnetic anisotropy. Magnetic characterization of the CoPt nanodot arrays showed increase in the perpendicular coercivity and squareness of the hysteresis loops from 2.0 kOe and 0.64 (without agitation) to 4.0 kOe and 0.87 with bath agitation. Based on the detailed characterization of nanodot arrays, the precise crystal structure control of the nanodot arrays with ultra-high recording density by electrochemical process was successfully demonstrated.

Three-Point Bending Fracture Behavior of Single Oriented Crossed-Lamellar Structure in Scapharca broughtonii Shell

PubMed Central

Ji, Hong-Mei; Zhang, Wen-Qian; Wang, Xu; Li, Xiao-Wu

2015-01-01

The three-point bending strength and fracture behavior of single oriented crossed-lamellar structure in Scapharca broughtonii shell were investigated. The samples for bending tests were prepared with two different orientations perpendicular and parallel to the radial ribs of the shell, which corresponds to the tiled and stacked directions of the first-order lamellae, respectively. The bending strength in the tiled direction is approximately 60% higher than that in the stacked direction, primarily because the regularly staggered arrangement of the second-order lamellae in the tiled direction can effectively hinder the crack propagation, whereas the cracks can easily propagate along the interfaces between lamellae in the stacked direction. PMID:28793557

Heteroepitaxial growth of Pt and Au thin films on MgO single crystals by bias-assisted sputtering

DOE PAGES

Tolstova, Yulia; Omelchenko, Stefan T.; Shing, Amanda M.; ...

2016-03-17

The crystallographic orientation of a metal affects its surface energy and structure, and has profound implications for surface chemical reactions and interface engineering, which are important in areas ranging from optoelectronic device fabrication to catalysis. However, it can be very difficult and expensive to manufacture, orient, and cut single crystal metals along different crystallographic orientations, especially in the case of precious metals. One approach is to grow thin metal films epitaxially on dielectric substrates. In this work, we report on growth of Pt and Au films on MgO single crystal substrates of (100) and (110) surface orientation for use asmore » epitaxial templates for thin film photovoltaic devices. We develop bias-assisted sputtering for deposition of oriented Pt and Au films with sub-nanometer roughness. We show that biasing the substrate decreases the substrate temperature necessary to achieve epitaxial orientation, with temperature reduction from 600 to 350 °C for Au, and from 750 to 550 °C for Pt, without use of transition metal seed layers. Additionally, this temperature can be further reduced by reducing the growth rate. Biased deposition with varying substrate bias power and working pressure also enables control of the film morphology and surface roughness.« less

Dynamics of an integral membrane peptide: a deuterium NMR relaxation study of gramicidin.

PubMed Central

Prosser, R S; Davis, J H

1994-01-01

Solid state deuterium (2H) NMR inversion-recovery and Jeener-Broekaert relaxation experiments were performed on oriented multilamellar dispersions consisting of 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine and 2H exchange-labeled gramicidin D, at a lipid to protein molar ratio (L/P) of 15:1, in order to study the dynamics of the channel conformation of the peptide in a liquid crystalline phase. Our dynamic model for the whole body motions of the peptide includes diffusion of the peptide around its helix axis and a wobbling diffusion around a second axis perpendicular to the local bilayer normal in a simple Maier-Saupe mean field potential. This anisotropic diffusion is characterized by the correlation times, tau R parallel and tau R perpendicular. Aligning the bilayer normal perpendicular to the magnetic field and graphing the relaxation rate, 1/T1Z, as a function of (1-S2N-2H), where S2N-2H represents the orientational order parameter, wer were able to estimate the correlation time, tau R parallel, for rotational diffusion. Although in the quadrupolar splitting, which varies as (3 cos2 theta D-1), has in general two possible solutions to theta D in the range 0 < or = theta D < or = 90 degrees, the 1/T1Z vs. (1-S2N-2H) curve can be used to determine a single value of theta D in this range. Thus, the 1/T1Z vs. (1-S2N-2H) profile can be used both to define the axial diffusion rate and to remove potential structural ambiguities in the splittings. The T1Z anisotropy permits us to solve for the two correlation times (tau R parallel = 6.8 x 10(-9) s and tau R perpendicular = 6 x 10(-6) s). The simulated parameters were corroborated by a Jeener-Broekaert experiment where the bilayer normal was parallel to the principal magnetic field. At this orientation the ratio, J2(2 omega 0)/J1(omega 0) was obtained in order to estimate the strength of the restoring potential in a model-independent fashion. This measurement yields the rms angle, 1/2 (= 16 +/- 2 degrees at 34 degrees C), formed by the peptide helix axis and the average bilayer normal. PMID:7520294

70. VIEW OF UNIT 2 THROUGH ACCESS DOOR, LOOKING DOWN ...

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

70. VIEW OF UNIT 2 THROUGH ACCESS DOOR, LOOKING DOWN AT MAIN SHAFT. NOTE WELDER'S SIGNATURE IN SHADOWS IN UPPER LEFT CORNER AND PHOTOGRAPHER'S STROBE POWER CABLE IN LOWER RIGHT CORNER. ORIENTATION OF CAMERA IS FACING LEFT BANK, PERPENDICULAR TO RIVER FLOW - Swan Falls Dam, Snake River, Kuna, Ada County, ID

Positional short-range order in the nematic phase of n BABAs

NASA Astrophysics Data System (ADS)

Usha Deniz, K.; Pepy, G.; Parette, G.; Keller, P.

1991-10-01

The positional short-range order, SRO ⊥, perpendicular to the nematic director n̂ has been studied in the fibre-type nematics, nBABAs, by neutron diffraction. SRO ⊥ is found to be dependent on other types of nematic short-range order but not on the orientational long-range order.

Forest dynamics in a forest-tundra ecotone, Medicine Bow Mountains, Wyoming

Treesearch

Christopher J. Earle

1993-01-01

The alpine timberline in much of western North America is characterized by a structurally complex transition from subalpine forest to alpine tundra, the forest-tundra ecotone. Trees within the ecotone are typically arrayed across the landscape within clumps or "ribbon forests," elongated strips oriented perpendicular to the prevailing winds. This study...

49 CFR 572.184 - Shoulder assembly.

Code of Federal Regulations, 2010 CFR

2010-10-01

... within ±2 degrees and the midsagittal plane of the thorax is positioned perpendicular to the direction of the plane of motion of the impactor at contact with the shoulder. The arms are oriented forward at 50... about the midsaggital plane with the distance between the innermost point on the opposite ankle at 100...

Cross-stream migration of active particles

NASA Astrophysics Data System (ADS)

Uspal, William; Katuri, Jaideep; Simmchen, Juliane; Miguel-Lopez, Albert; Sanchez, Samuel

For natural microswimmers, the interplay of swimming activity and external flow can promote robust directed motion, e.g. propulsion against (upstream rheotaxis) or perpendicular to the direction of flow. These effects are generally attributed to their complex body shapes and flagellar beat patterns. Here, using catalytic Janus particles as a model system, we report on a strong directional response that naturally emerges for spherical active particles in a channel flow. The particles align their propulsion axis to be perpendicular to both the direction of flow and the normal vector of a nearby bounding surface. We develop a deterministic theoretical model that captures this spontaneous transverse orientational order. We show how the directional response emerges from the interplay of external shear flow and swimmer/surface interactions (e.g., hydrodynamic interactions) that originate in swimming activity. Finally, adding the effect of thermal noise, we obtain probability distributions for the swimmer orientation that show good agreement with the experimental probability distributions. Our findings show that the qualitative response of microswimmers to flow is sensitive to the detailed interaction between individual microswimmers and bounding surfaces.

Orientation dependent cyclic stability of the elastocaloric effect in textured Ni-Mn-Ga alloys

NASA Astrophysics Data System (ADS)

Wei, Longsha; Zhang, Xuexi; Liu, Jian; Geng, Lin

2018-05-01

High-performance elastocaloric materials require a large reversible elastocaloric effect and long life cyclic stability. Here, we fabricated textured polycrystalline Ni50.4Mn27.3Ga22.3 alloys by cost-effective casting method to create a <001> texture. A strong correlation between the cyclic stability and the crystal orientation was demonstrated. A large reversible adiabatic temperature change ΔT ˜6 K was obtained when the external stress was applied parallel to <001> direction. However, the ΔT decreased rapidly after 50 cycles, showing an unstable elastocaloric effect (eCE). On the other hand, when the external stress was applied perpendicular to <001>, the adiabatic ΔT was smaller ˜4 K, but was stable over 100 cycles. This significantly enhanced eCE stability was related to the high yield strength, low transformation strain and much higher crack initiation-propagation resistances perpendicular to <001> direction. This study provides a feasible strategy for optimizing the eCE property by creation of the texture structure in polycrystalline Ni-Mn-Ga and Ni-Mn-X (X= In, Sn, Sb) alloys.

Direct measurements of mean Reynolds stress and ripple roughness in the presence of energetic forcing by surface waves

USGS Publications Warehouse

Scully, Malcolm; Trowbridge, John; Sherwood, Christopher R.; Jones, Katie R.; Traykovski, Peter A.

2018-01-01

Direct covariance observations of the mean flow Reynolds stress and sonar images of the seafloor collected on a wave‐exposed inner continental shelf demonstrate that the drag exerted by the seabed on the overlying flow is consistent with boundary layer models for wave‐current interaction, provided that the orientation and anisotropy of the bed roughness are appropriately quantified. Large spatial and temporal variations in drag result from nonequilibrium ripple dynamics, ripple anisotropy, and the orientation of the ripples relative to the current. At a location in coarse sand characterized by large two‐dimensional orbital ripples, the observed drag shows a strong dependence on the relative orientation of the mean current to the ripple crests. At a contrasting location in fine sand, where more isotropic sub‐orbital ripples are observed, the sensitivity of the current to the orientation of the ripples is reduced. Further, at the coarse site under conditions when the currents are parallel to the ripple crests and the wave orbital diameter is smaller than the wavelength of the relic orbital ripples, the flow becomes hydraulically smooth. This transition is not observed at the fine site, where the observed wave orbital diameter is always greater than the wavelength of the observed sub‐orbital ripples. Paradoxically, the dominant along‐shelf flows often experience lower drag at the coarse site than at the fine site, despite the larger ripples, highlighting the complex dynamics controlling drag in wave‐exposed environments with heterogeneous roughness.

Direct Measurements of Mean Reynolds Stress and Ripple Roughness in the Presence of Energetic Forcing by Surface Waves

NASA Astrophysics Data System (ADS)

Scully, Malcolm E.; Trowbridge, John H.; Sherwood, Christopher R.; Jones, Katie R.; Traykovski, Peter

2018-04-01

Direct covariance observations of the mean flow Reynolds stress and sonar images of the seafloor collected on a wave-exposed inner continental shelf demonstrate that the drag exerted by the seabed on the overlying flow is consistent with boundary layer models for wave-current interaction, provided that the orientation and anisotropy of the bed roughness are appropriately quantified. Large spatial and temporal variations in drag result from nonequilibrium ripple dynamics, ripple anisotropy, and the orientation of the ripples relative to the current. At a location in coarse sand characterized by large two-dimensional orbital ripples, the observed drag shows a strong dependence on the relative orientation of the mean current to the ripple crests. At a contrasting location in fine sand, where more isotropic sub-orbital ripples are observed, the sensitivity of the current to the orientation of the ripples is reduced. Further, at the coarse site under conditions when the currents are parallel to the ripple crests and the wave orbital diameter is smaller than the wavelength of the relic orbital ripples, the flow becomes hydraulically smooth. This transition is not observed at the fine site, where the observed wave orbital diameter is always greater than the wavelength of the observed sub-orbital ripples. Paradoxically, the dominant along-shelf flows often experience lower drag at the coarse site than at the fine site, despite the larger ripples, highlighting the complex dynamics controlling drag in wave-exposed environments with heterogeneous roughness.

Spin Hall driven domain wall motion in magnetic bilayers coupled by a magnetic oxide interlayer

NASA Astrophysics Data System (ADS)

Liu, Yang; Furuta, Masaki; Zhu, Jian-Gang Jimmy

2018-05-01

mCell, previously proposed by our group, is a four-terminal magnetoresistive device with isolated write- and read-paths for all-spin logic and memory applications. A mCell requires an electric-insulating magnetic layer to couple the spin Hall driven write-path to the magnetic free layer of the read-path. Both paths are magnetic layers with perpendicular anisotropy and their perpendicularly oriented magnetization needs to be maintained with this insertion layer. We have developed a magnetic oxide (FeOx) insertion layer to serve for these purposes. We show that the FeOx insertion layer provides sufficient magnetic coupling between adjacent perpendicular magnetic layers. Resistance measurement shows that this magnetic oxide layer can act as an electric-insulating layer. In addition, spin Hall driven domain wall motion in magnetic bi-layers coupled by the FeOx insertion layer is significantly enhanced compared to that in magnetic single layer; it also requires low voltage threshold that poses possibility for power-efficient device applications.

Tunable magnetic properties by interfacial manipulation of L1(0)-FePt perpendicular ultrathin film with island-like structures.

PubMed

Feng, C; Wang, S G; Yang, M Y; Zhang, E; Zhan, Q; Jiang, Y; Li, B H; Yu, G H

2012-02-01

Based on interfacial manipulation of the MgO single crystal substrate and non-magnetic AIN compound, a L1(0)-FePt perpendicular ultrathin film with the structure of MgO/FePt-AIN/Ta was designed, prepared, and investigated. The film is comprised of L1(0)-FePt "magnetic islands," which exhibits a perpendicular magnetic anisotropy (PMA), tunable coercivity (Hc), and interparticle exchange coupling (IEC). The MgO substrate promotes PMA of the film because of interfacial control of the FePt lattice orientation. The AIN compound is doped to increase the difference of surface energy between FePt layer and MgO substrate and to suppress the growth of FePt grains, which takes control of island growth mode of FePt atoms. The AIN compound also acts as isolator of L1(0)-FePt islands to pin the sites of FePt domains, resulting in the tunability of Hc and IEC of the films.

Thermally-induced transition of lamellae orientation in block-copolymer films on ‘neutral’ nanoparticle-coated substrates

DOE PAGES

Yager, Kevin G.; Forrey, Christopher; Singh, Gurpreet; ...

2015-06-01

Block-copolymer orientation in thin films is controlled by the complex balance between interfacial free energies, including the inter-block segregation strength, the surface tensions of the blocks, and the relative substrate interactions. While block-copolymer lamellae orient horizontally when there is any preferential affinity of one block for the substrate, we recently described how nanoparticle-roughened substrates can be used to modify substrate interactions. We demonstrate how such ‘neutral’ substrates can be combined with control of annealing temperature to generate vertical lamellae orientations throughout a sample, at all thicknesses. We observe an orientational transition from vertical to horizontal lamellae upon heating, as confirmedmore » using a combination of atomic force microscopy (AFM), neutron reflectometry (NR) and rotational small-angle neutron scattering (RSANS). Using molecular dynamics (MD) simulations, we identify substrate-localized distortions to the lamellar morphology as the physical basis of the novel behavior. In particular, under strong segregation conditions, bending of horizontal lamellae induce a large energetic cost. At higher temperatures, the energetic cost of conformal deformations of lamellae over the rough substrate is reduced, returning lamellae to the typical horizontal orientation. Thus, we find that both surface interactions and temperature play a crucial role in dictating block-copolymer lamellae orientation. As a result, our combined experimental and simulation findings suggest that controlling substrate roughness should provide a useful and robust platform for controlling block-copolymer orientation in applications of these materials.« less

Controlling Heat Transport and Flow Structures in Thermal Turbulence Using Ratchet Surfaces

NASA Astrophysics Data System (ADS)

Jiang, Hechuan; Zhu, Xiaojue; Mathai, Varghese; Verzicco, Roberto; Lohse, Detlef; Sun, Chao

2018-01-01

In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchetlike roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the large scale circulation roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through a quantitative analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. The current work has important implications for passive and active flow control in engineering, biofluid dynamics, and geophysical flows.

Structure evolution of zinc oxide thin films deposited by unbalance DC magnetron sputtering

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

Aryanto, Didik, E-mail: didi027@lipi.go.id; Materials Research Group, Physics Department, Universitas Negeri Semarang, Gunungpati, Semarang 50229 Jawa Tengah; Marwoto, Putut

Zinc oxide (ZnO) thin films are deposited on corning glass substrates using unbalanced DC magnetron sputtering. The effect of growth temperature on surface morphology and crystallographic orientation of ZnO thin film is studied using atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The surface morphology and crystallographic orientation of ZnO thin film are transformed against the increasing of growth temperature. The mean grain size of film and the surface roughness are inversely and directly proportional towards the growth temperature from room temperature to 300 °C, respectively. The smaller grain size and finer roughness of ZnO thin film are obtainedmore » at growth temperature of 400 °C. The result of AFM analysis is in good agreement with the result of XRD analysis. ZnO thin films deposited in a series of growth temperatures have hexagonal wurtzite polycrystalline structures and they exhibit transformations in the crystallographic orientation. The results in this study reveal that the growth temperature strongly influences the surface morphology and crystallographic orientation of ZnO thin film.« less

Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties.

PubMed

Dhar, Prodyut; Kumar, Amit; Katiyar, Vimal

2016-07-20

This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low magnetic fields, with potential applications in the manufacturing of three-dimensional composites with microstructural features comparable to biological materials for high-performance engineering applications.

Structural Evolution of Martin Crater Thaumasia Planum, Mars

NASA Astrophysics Data System (ADS)

Dolan, Daniel J.

A detailed structural map of the central uplift of Martin Crater in western Thaumasia Planum, Mars, reveals highly folded and fractured geology throughout the 15-km diameter uplift. The stratigraphy in the central uplift of the crater has been rotated to near vertical dip and imaged by high-definition cameras aboard the Mars Reconnaissance Orbiter (MRO). These unique factors allow individual geologic beds in Martin Crater to be studied and located across the length of the uplift. Bedding in Martin Crater primarily strikes SSE-NNW and dips near vertically. Many units are separated by a highly complex series of linear faults, creating megablocks of uplifted material. Faulting is dominantly left-slip in surface expression and strikes SW-NE, roughly perpendicular to bedding, and major fold axes plunge toward the SW. Coupled with infrared imagery of the ejecta blanket, which shows an "exclusion zone" northeast of the crater, these structural indicators provide strong support for a low-angle impactor (approximately 10-20°) originating from the northeast. Acoustic fluidization is the prevailing theoretical model put forth to explain complex crater uplift. The theory predicts that uplifted megablocks in craters are small, discrete, separated and highly randomized in orientation. However, megablocks in Martin Crater are tightly interlocked and often continuous in lithology across several kilometers. Thus, the model of acoustic fluidization, as it is currently formulated, does not appear to be supported by the structural evidence found in Martin Crater.

Atomic alignment effect on reactivity and on product alignment in the energy-transfer reaction of oriented Ar (3P2, 4s [3/2]2, M(J) = 2) + Kr (4p6, 1S0) → Ar (3p6, 1S0) + Kr (5p [3/2]2).

PubMed

Ohoyama, H

2015-03-12

Steric effect for the formation of Kr (5p [3/2]₂) in the energy transfer reaction of Ar (³P₂, 4s [3/2]₂) + Kr has been studied by using an oriented Ar (³P₂, 4s [3/2]₂, M(J) = 2) beam at a collision energy of ∼0.09 eV. The emission intensity of Kr (5p [3/2]₂) is ca. 2 times enhanced when the angular momentum (J(Ar)) of Ar (³P₂) is aligned perpendicular to the relative velocity vector (v(R)). In addition, the Kr (5p [3/2]₂) emission is highly polarized parallel to v(R) (I(∥)/I(⊥) ∼ 1.2) when JAr is aligned perpendicular to v(R). The observed polarization moments indicate that the alignment of the unpaired Ar (3p) orbital of Ar (³P₂) to v(R), (Σ (|L′| = 0), Π (|L′| = 1)), dominates the energy transfer probability (σ(Π)(∥): σ(Σ)(∥): σ(Π)(⊥): σ(Σ)(⊥) = 0.49:1.33:0.55:1.23) and also the alignment of the Kr (5p) orbital of Kr (5p [3/2]₂) to v(R): the Σ-configuration of the Ar (3p) orbital leads to the parallel alignment (Σ-configuration) of the Kr(5p) orbital to v(R), conversely, the Π-configuration of Ar (3p) orbital leads to the perpendicular alignment (Π-configuration) of the Kr(5p) orbital. In addition, the selectivity of the alignment of the Kr (5p) orbital turns out to vary from perpendicular to parallel as the collision energy increases after a threshold down to 0.03 eV.

Guidance of dorsal root ganglion neurites and Schwann cells by isolated Schwann cell topography on poly(dimethyl siloxane) conduits and films

NASA Astrophysics Data System (ADS)

Richardson, J. A.; Rementer, C. W.; Bruder, Jan M.; Hoffman-Kim, D.

2011-08-01

Biomimetic replicas of cellular topography have been utilized to direct neurite outgrowth. Here, we cultured postnatal rat dorsal root ganglion (DRG) explants in the presence of Schwann cell (SC) topography to determine the influence of SC topography on neurite outgrowth. Four distinct poly(dimethyl siloxane) conduits were fabricated within which DRG explants were cultured. To determine the contribution of SC topographical features to neurite guidance, the extent of neurite outgrowth into unpatterned conduits, conduits with randomly oriented SC replicas, and conduits with SC replicas parallel or perpendicular to the conduit long axis was measured. Neurite directionality and outgrowth from DRG were also quantified on two-dimensional SC replicas with orientations corresponding to the four conduit conditions. Additionally, live SC migration and neurite extension from DRG on SC replicas were examined as a first step toward quantification of the interactions between live SC and navigating neurites on SC replicas. DRG neurite outgrowth and morphology within conduits and on two-dimensional SC replicas were directed by the underlying SC topographical features. Maximal neurite outgrowth and alignment to the underlying features were observed into parallel conduits and on parallel two-dimensional substrates, whereas the least extent of outgrowth was observed into perpendicular conduits and on perpendicular two-dimensional replica conditions. Additionally, neurites on perpendicular conditions turned to extend along the direction of underlying SC topography. Neurite outgrowth exceeded SC migration in the direction of the underlying anisotropic SC replica after two days in culture. This finding confirms the critical role that SC have in guiding neurite outgrowth and suggests that the mechanism of neurite alignment to SC replicas depends on direct contact with cellular topography. These results suggest that SC topographical replicas may be used to direct and optimize neurite alignment, and emphasize the importance of SC features in neurite guidance.

Strong-field approximation for ionization of a diatomic molecule by a strong laser field. II. The role of electron rescattering off the molecular centers

NASA Astrophysics Data System (ADS)

Busuladžić, M.; Gazibegović-Busuladžić, A.; Milošević, D. B.; Becker, W.

2008-09-01

The strong-field approximation for ionization of diatomic molecules by a strong laser field [D. B. Milošević, Phys. Rev. A 74, 063404 (2006)] is generalized to include rescattering of the ionized electron wave packet off the molecular centers (the electron’s parent ion or the second atom). There are four rescattering contributions to the ionization rate, which are responsible for the high-energy plateau in the electron spectra and which interfere in a complicated manner. The spectra are even more complicated due to the different symmetry properties of the atomic orbitals of which a particular molecular orbital consists. Nevertheless, a comparatively simple condition emerges for the destructive interference of all these contributions, which yields a curve in the (Epf,θ) plane. Here θ is the electron emission angle and Epf is the electron kinetic energy. The resulting suppression of the rescattering plateau can be strong and affect a large area of the (Epf,θ) plane, depending on the orientation of the molecule. We illustrate this using the examples of the 3σg molecular orbital of N2 and the 1πg molecular orbital of O2 for various orientations of these molecules with respect to the laser polarization axis. For N2 , for perpendicular orientation and the equilibrium internuclear distance R0 , we find that the minima of the ionization rate form the curve Epfcos2θ=π2/(2R02) in the (Epf,θ) plane. For O2 the rescattering plateau is absent for perpendicular orientation.

Changes in myosin S1 orientation and force induced by a temperature increase.

PubMed

Griffiths, Peter J; Bagni, Maria A; Colombini, Barbara; Amenitsch, Heinz; Bernstorff, Sigrid; Ashley, Christopher C; Cecchi, Giovanni; Ameritsch, Heinz

2002-04-16

Force generation in myosin-based motile systems is thought to result from an angular displacement of the myosin subfragment 1 (S1) tail domain with respect to the actin filament axis. In muscle, raised temperature increases the force generated by S1, implying a greater change in tail domain angular displacement. We used time-resolved x-ray diffraction to investigate the structural corollary of this force increase by measuring M3 meridional reflection intensity during sinusoidal length oscillations. This technique allows definition of S1 orientation with respect to the myofilament axis. M3 intensity changes were approximately sinusoid at low temperatures but became increasingly distorted as temperature was elevated, with the formation of a double intensity peak at maximum shortening. This increased distortion could be accounted for by assuming a shift in orientation of the tail domain of actin-bound S1 toward the orientation at which M3 intensity is maximal, which is consistent with a tail domain rotation model of force generation in which the tail approaches a more perpendicular projection from the thin filament axis at higher temperatures. In power stroke simulations, the angle between S1 tail mean position during oscillations and the position at maximum intensity decreased by 4.7 degrees, corresponding to a mean tail displacement toward the perpendicular of 0.73 nm for a temperature-induced force increase of 0.28 P(0) from 4 to 22 degrees C. Our findings suggest that at least 62% of crossbridge compliance is associated with the tail domain.

Impact of a High Magnetic Field on the Orientation of Gravitactic Unicellular Organisms—A Critical Consideration about the Application of Magnetic Fields to Mimic Functional Weightlessness

PubMed Central

Simon, Anja; Waßer, Kai; Hauslage, Jens; Christianen, Peter C.M.; Albers, Peter W.; Lebert, Michael; Richter, Peter; Alt, Wolfgang; Anken, Ralf

2014-01-01

Abstract The gravity-dependent behavior of Paramecium biaurelia and Euglena gracilis have previously been studied on ground and in real microgravity. To validate whether high magnetic field exposure indeed provides a ground-based facility to mimic functional weightlessness, as has been suggested earlier, both cell types were observed during exposure in a strong homogeneous magnetic field (up to 30 T) and a strong magnetic field gradient. While swimming, Paramecium cells were aligned along the magnetic field lines; orientation of Euglena was perpendicular, demonstrating that the magnetic field determines the orientation and thus prevents the organisms from the random swimming known to occur in real microgravity. Exposing Astasia longa, a flagellate that is closely related to Euglena but lacks chloroplasts and the photoreceptor, as well as the chloroplast-free mutant E. gracilis 1F, to a high magnetic field revealed no reorientation to the perpendicular direction as in the case of wild-type E. gracilis, indicating the existence of an anisotropic structure (chloroplasts) that determines the direction of passive orientation. Immobilized Euglena and Paramecium cells could not be levitated even in the highest available magnetic field gradient as sedimentation persisted with little impact of the field on the sedimentation velocities. We conclude that magnetic fields are not suited as a microgravity simulation for gravitactic unicellular organisms due to the strong effect of the magnetic field itself, which masks the effects known from experiments in real microgravity. Key Words: Levitation—Microgravity—Gravitaxis—Gravikinesis—Gravity. Astrobiology 14, 205–215. PMID:24621307

The Sunda-Banda Arc Transition: New Insights From Marine Wide-Angle Seismic Data

NASA Astrophysics Data System (ADS)

Planert, L.; Shulgin, A.; Kopp, H.; Mueller, C.; Flueh, E.; Lueschen, E.; Engels, M.; Dayuf Jusuf, M.

2007-12-01

End of 2006, RV SONNE cruise SO190 SINDBAD (Seismic and Geoacoustic Investigations along the Sunda- Banda Arc Transition) went south of the Indonesian archipelago to acquire various geophysical datasets between 112 °E and 122 °E. The main goal of the project is to investigate the modifications of the lower plate (variability in the plate roughness, transition from oceanic to continental lower plate) and their effects on the tectonics of the upper plate (development of an outer high and forearc basin, accretionary and erosive processes). The tectonic style changes in neighboring margin segments from an oceanic plate-island arc subduction along the eastern Sunda margin to a continental plate-island arc collision along the Banda margin. Moreover, the character of the incoming oceanic plate varies from the rough topography in the area where the Roo Rise is subducting off eastern Java, to the smooth oceanic seafloor of the Argo- Abyssal Plain subducting off Bali, Lombok, and Sumbawa. In order to cover the entire variations of the lower plate, seven seismic refraction profiles were conducted along four major north-south oriented corridors of the margin, at 113 °E, 116 °E, 119 °E, and 121 °E, as well as three profiles running perpendicular to the major corridors. A total of 239 ocean bottom hydrophone and seismometer deployments were successfully recovered. Shooting was conducted along 1020 nm of seismic profiles using a G-gun cluster of 64 l. Here, we present velocity models obtained by applying a tomographic approach which jointly inverts for refracted and reflected phases. Additional geometry and velocity information for the uppermost layers, obtained by prestack depth migration of multichannel seismic reflection data (see poster of Mueller et al. in this session), is incorporated into our models and held fixed during the iterations. geomar.de/index.php?id=sindbad

Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering

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

Barhoumi, A., E-mail: amira-barhoumi@yahoo.fr; Guermazi, S.; Leroy, G.

2014-05-28

Al-doped ZnO thin films (AZO) have been deposited on amorphous glass substrates by DC sputtering at different substrate temperatures T{sub s}. X-Ray diffraction results reveal that AZO thin films have a hexagonal wurtzite structure with (002) preferred orientation. (002) peaks indicate that the crystalline structure of the films is oriented with c-axis perpendicular to the substrate. Three-dimensional (3D) atomic force microscopy images of AZO thin films deposited on glass substrate at 200 °C, 300 °C, and 400 °C, respectively, shows the improvement of the crystallinity and the homogeneity of AZO thin films with T{sub s} which is in agreement with the noise measurements.more » The noise was characterized between 1 Hz and 100 kHz and we have obtained 1/f spectra. The noise is very sensitive to the crystal structure especially to the orientation of the crystallites which is perpendicular to the substrate and to the grain boundaries which generate a high current flow and a sharp increase in noise. Through time, R{sub sh} and [αμ]{sub eff} increase with the modification of the crystallinity of AZO thin films. Study of noise aging shows that the noise is more sensitive than resistivity for all AZO thin films.« less

Fin field effect transistor directionality impacts printing of implantation shapes

NASA Astrophysics Data System (ADS)

Wang, Xiren; Granik, Yuri

2018-01-01

In modern integrated circuit (IC) fabrication processes, the photoresist receives considerable illumination energy that is reflected by underlying topography during optical lithography of implantation layers. Bottom antireflective coating (BARC) is helpful to mitigate the reflection. Often, however, BARC is not used, because its removal is technically challenging, in addition to its relatively high economic cost. Furthermore, the advanced technology nodes, such as 14/10-nm nodes, have introduced fin field effect transistor (FinFET), which makes reflection from nonuniform silicon substrates exceptionally complicated. Therefore, modeling reflection from topography becomes obligatory to accurately predict printing of implantation shapes. Typically, FinFET is always fixed in one direction in realistic designs. However, the same implantation rectangle may be oriented in either horizontal or vertical direction. Then, there are two types of relations between the critical dimension (CD) and FinFET, namely a parallel-to and a perpendicular-to relation. We examine the fin directionality impact on CD. We found that this impact may be considerable in some cases. We use our in-house rigorous optical topography simulator to reveal underlining physical reasons. One of the major causes of the CD differences is that in the parallel orientation, the solid sidewalls of the fins conduct considerable light reflections unlike for the perpendicular orientation. This finding can aid the compact modeling in optical proximity correction of implantation masks.

Depth-Dependent Anisotropies of Amides and Sugar in Perpendicular and Parallel Sections of Articular Cartilage by Fourier Transform Infrared Imaging (FTIRI)

PubMed Central

Xia, Yang; Mittelstaedt, Daniel; Ramakrishnan, Nagarajan; Szarko, Matthew; Bidthanapally, Aruna

2010-01-01

Full thickness blocks of canine humeral cartilage were microtomed into both perpendicular sections and a series of 100 parallel sections, each 6 μm thick. Fourier Transform Infrared Imaging (FTIRI) was used to image each tissue section eleven times under different infrared polarizations (from 0° to 180° polarization states in 20° increments and with an additional 90° polarization), at a spatial resolution of 6.25 μm and a wavenumber step of 8 cm−1. With increasing depth from the articular surface, amide anisotropies increased in the perpendicular sections and decreased in the parallel sections. Both types of tissue sectioning identified a 90° difference between amide I and amide II in the superficial zone of cartilage. The fibrillar distribution in the parallel sections from the superficial zone was shown to not be random. Sugar had the greatest anisotropy in the upper part of the radial zone in the perpendicular sections. The depth-dependent anisotropic data were fitted with a theoretical equation that contained three signature parameters, which illustrate the arcade structure of collagens with the aid of a fibril model. Infrared imaging of both perpendicular and parallel sections provides the possibility of determining the three-dimensional macromolecular structures in articular cartilage. Being sensitive to the orientation of the macromolecular structure in healthy articular cartilage aids the prospect of detecting the early onset of the tissue degradation that may lead to pathological conditions such as osteoarthritis. PMID:21274999

Demonstrating the Effects of Processing on the Structure and Physical Properties of Plastic Using Disposable PETE Cups

ERIC Educational Resources Information Center

Erk, Kendra A.; Rhein, Morgan; Krafcik, Matthew J.; Ydstie, Sophie

2015-01-01

An educational activity is described in which the structure and physical properties of disposable plastic cups were directly related to the method of processing. The mechanical properties of specimens cut from the walls of poly(ethylene terephthalate) (PETE) cups, oriented parallel and perpendicular to the thermoforming direction, were measured in…

Synthesis of new oligothiophene derivatives and their intercalation compounds: Orientation effects

USGS Publications Warehouse

Ibrahim, M.A.; Lee, B.-G.; Park, N.-G.; Pugh, J.R.; Eberl, D.D.; Frank, A.J.

1999-01-01

The orientation dependence of intercalated oligothiophene derivatives in vermiculite and metal disulfides MS2 (M = Mo, Ti and Zr) on the pendant group on the thiophene ring and the host material was studied by X-ray diffraction (XRD) and solid state nuclear magnetic resonance spectroscopy. Amino and nitro derivatives of bi-, ter- and quarter-thiophenes were synthesized for the first time. The amino-oligothiophenes were intercalated into vermiculite by an exchange reaction with previously intercalated octadecylammonium vermiculite and into MS2 by the intercalation-exfoliation technique. Analysis of the XRD data indicates that a monolayer of amino-oligothiophene orients perpendicularly to the silicate surface in vermiculite and lies flat in the van der Waals gap of MS2.

Magnetically induced orientation of mesochannels in mesoporous silica films at 30 tesla.

PubMed

Yamauchi, Yusuke; Sawada, Makoto; Komatsu, Masaki; Sugiyama, Atsushi; Osaka, Tetsuya; Hirota, Noriyuki; Sakka, Yoshio; Kuroda, Kazuyuki

2007-12-03

We demonstrate the magnetically induced orientation of mesochannels in mesoporous silica films prepared with low-molecular-weight surfactants under an extremely high magnetic field of 30 T. This process is principally applicable to any type of surfactant that has magnetic anisotropy because such a high magnetic field provides sufficient magnetic energy for smooth magnetic orientation. Hexadecyltrimethylammonium bromide (CTAB) and polyoxyethylene-10-cetyl ether (Brij 56) were used as cationic and nonionic surfactants, respectively. According to XRD and cross-sectional TEM, mesochannels aligned perpendicular to the substrates were observed in films prepared with low-molecular-weight surfactants, although the effect was incomplete. The evolution of these types of films should lead to future applications such as highly sensitive chemical sensors and selective separation.

Crystallographic texture in pulsed laser deposited hydroxyapatite bioceramic coatings

PubMed Central

Kim, Hyunbin; Camata, Renato P.; Lee, Sukbin; Rohrer, Gregory S.; Rollett, Anthony D.; Vohra, Yogesh K.

2008-01-01

The orientation texture of pulsed laser deposited hydroxyapatite coatings was studied by X-ray diffraction techniques. Increasing the laser energy density of the KrF excimer laser used in the deposition process from 5 to 7 J/cm2 increases the tendency for the c-axes of the hydroxyapatite grains to be aligned perpendicular to the substrate. This preferred orientation is most pronounced when the incidence direction of the plume is normal to the substrate. Orientation texture of the hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Anisotropic stresses, transport of hydroxyl groups and dehydroxylation effects during deposition all seem to play important roles in the texture development. PMID:18563207

Ion Acceleration by Multiple Reflections at Martian Bow Shock

NASA Astrophysics Data System (ADS)

Yamauchi, M.; Futaana, Y.; Fedorov, A.; Frahm, R. A.; Dubinin, E.; Lundin, R.; Sauvaud, J.-A.; Winningham, J. D.; Barabash, S.; Holmström, H.

2012-04-01

The ion mass analyzer (IMA) on board Mars Express revealed bundled structures of ions in the energy domain within a distance of a proton gyroradius from the Martian bow shock. Seven prominent traversals during 2005 were examined when the energy-bunched structure was observed together with pick-up ions of exospheric origin, the latter of which is used to determine the local magnetic field orientation from its circular trajectory in velocity space. These seven traversals include different bow shock configurations: (a) quasi-perpendicular shock with its specular direction of the solar wind more perpendicular to the magnetic field (QT), (b) quasi-perpendicular shock with its specular reflection direction of the solar wind more along the magnetic field (FS), and (c) quasi-parallel (QL) shock. In all seven cases, the velocity components of the energy-bunched structure are consistent with multiple specular reflections of the solar wind at the bow shock up to at least two reflections. The accelerated solar wind ions after two specular reflections have large parallel components with respect to the magnetic field for the QL shock whereas the field-aligned speed is much smaller than the perpendicular speed for the QT shock. The reflected ions escape into the solar wind when and only when the reflection is in the field-aligned direction.

Spiraling contaminant electrons increase doses to surfaces outside the photon beam of an MRI-linac with a perpendicular magnetic field

NASA Astrophysics Data System (ADS)

Hackett, S. L.; van Asselen, B.; Wolthaus, J. W. H.; Bluemink, J. J.; Ishakoglu, K.; Kok, J.; Lagendijk, J. J. W.; Raaymakers, B. W.

2018-05-01

The transverse magnetic field of an MRI-linac sweeps contaminant electrons away from the radiation beam. Films oriented perpendicular to the magnetic field and 5 cm from the radiation beam edge show a projection of the divergent beam, indicating that contaminant electrons spiral along magnetic field lines and deposit dose on surfaces outside the primary beam perpendicular to the magnetic field. These spiraling contaminant electrons (SCE) could increase skin doses to protruding regions of the patient along the cranio-caudal axis. This study investigated doses from SCE for an MRI-linac comprising a 7 MV linac and a 1.5 T MRI scanner. Surface doses to films perpendicular to the magnetic field and 5 cm from the radiation beam edge showed increased dose within the projection of the primary beam, whereas films parallel to the magnetic field and 5 cm from the beam edge showed no region of increased dose. However, the dose from contaminant electrons is absorbed within a few millimeters. For large fields, the SCE dose is within the same order of magnitude as doses from scattered and leakage photons. Doses for both SCE and scattered photons decrease rapidly with decreasing beam size and increasing distance from the beam edge.

Structural modeling of carbonaceous mesophase amphotropic mixtures under uniaxial extensional flow.

PubMed

Golmohammadi, Mojdeh; Rey, Alejandro D

2010-07-21

The extended Maier-Saupe model for binary mixtures of model carbonaceous mesophases (uniaxial discotic nematogens) under externally imposed flow, formulated in previous studies [M. Golmohammadi and A. D. Rey, Liquid Crystals 36, 75 (2009); M. Golmohammadi and A. D. Rey, Entropy 10, 183 (2008)], is used to characterize the effect of uniaxial extensional flow and concentration on phase behavior and structure of these mesogenic blends. The generic thermorheological phase diagram of the single-phase binary mixture, given in terms of temperature (T) and Deborah (De) number, shows the existence of four T-De transition lines that define regions that correspond to the following quadrupolar tensor order parameter structures: (i) oblate (perpendicular, parallel), (ii) prolate (perpendicular, parallel), (iii) scalene O(perpendicular, parallel), and (iv) scalene P(perpendicular, parallel), where the symbols (perpendicular, parallel) indicate alignment of the tensor order ellipsoid with respect to the extension axis. It is found that with increasing T the dominant component of the mixture exhibits weak deviations from the well-known pure species response to uniaxial extensional flow (uniaxial perpendicular nematic-->biaxial nematic-->uniaxial parallel paranematic). In contrast, the slaved component shows a strong deviation from the pure species response. This deviation is dictated by the asymmetric viscoelastic coupling effects emanating from the dominant component. Changes in conformation (oblate <==> prolate) and orientation (perpendicular <==> parallel) are effected through changes in pairs of eigenvalues of the quadrupolar tensor order parameter. The complexity of the structural sensitivity to temperature and extensional flow is a reflection of the dual lyotropic/thermotropic nature (amphotropic nature) of the mixture and their cooperation/competition. The analysis demonstrates that the simple structures (biaxial nematic and uniaxial paranematic) observed in pure discotic mesogens under uniaxial extensional flow are significantly enriched by the interaction of the lyotropic/thermotropic competition with the binary molecular architectures and with the quadrupolar nature of the flow.

Influence of Under-layer Morphology on Structural and Magnetic Properties of Sputtered Co81Pd19 Films

NASA Astrophysics Data System (ADS)

Ponchaiya, Pairin; Rattanasakulthong, Watcharee

2017-09-01

Sputtered Co81Pd19 films with thickness of about 60 nm were deposited on various under-layers (Co, Ni, Cr and Al) and on glass substrate. Structural, morphological and magnetic properties of Co81Pd19 films were investigated. All of prepared Co81Pd19 film showed CoPd-FCC phase in (111) direction on CoO-FCC (111), NiO-FCC (200), Cr-BCC (200) and (201) and AlO-FCC (200) phases of Co, Ni, Cr and Al under-layer, respectively. AFM images revealed that the film on Cr under-layers and glass substrate exhibited the maximum roughness with the highest grain size and the minimum roughness with the continuous grain size, respectively. Both parallel and perpendicular maximum coercive field were found in the film on glass under-layer and the film on Co-under-layer film showed the highest saturation magnetization from both in-plane and out-of-plane measurements. These results confirmed that the structural and magnetic properties of sputtered Co81Pd19 films were affected by under-layer surface roughness and morphology by the virtue of particle size and distribution on the under-layer film surface.

Research on the Rapid and Accurate Positioning and Orientation Approach for Land Missile-Launching Vehicle

PubMed Central

Li, Kui; Wang, Lei; Lv, Yanhong; Gao, Pengyu; Song, Tianxiao

2015-01-01

Getting a land vehicle’s accurate position, azimuth and attitude rapidly is significant for vehicle based weapons’ combat effectiveness. In this paper, a new approach to acquire vehicle’s accurate position and orientation is proposed. It uses biaxial optical detection platform (BODP) to aim at and lock in no less than three pre-set cooperative targets, whose accurate positions are measured beforehand. Then, it calculates the vehicle’s accurate position, azimuth and attitudes by the rough position and orientation provided by vehicle based navigation systems and no less than three couples of azimuth and pitch angles measured by BODP. The proposed approach does not depend on Global Navigation Satellite System (GNSS), thus it is autonomous and difficult to interfere. Meanwhile, it only needs a rough position and orientation as algorithm’s iterative initial value, consequently, it does not have high performance requirement for Inertial Navigation System (INS), odometer and other vehicle based navigation systems, even in high precise applications. This paper described the system’s working procedure, presented theoretical deviation of the algorithm, and then verified its effectiveness through simulation and vehicle experiments. The simulation and experimental results indicate that the proposed approach can achieve positioning and orientation accuracy of 0.2 m and 20″ respectively in less than 3 min. PMID:26492249

Research on the rapid and accurate positioning and orientation approach for land missile-launching vehicle.

PubMed

Li, Kui; Wang, Lei; Lv, Yanhong; Gao, Pengyu; Song, Tianxiao

2015-10-20

Getting a land vehicle's accurate position, azimuth and attitude rapidly is significant for vehicle based weapons' combat effectiveness. In this paper, a new approach to acquire vehicle's accurate position and orientation is proposed. It uses biaxial optical detection platform (BODP) to aim at and lock in no less than three pre-set cooperative targets, whose accurate positions are measured beforehand. Then, it calculates the vehicle's accurate position, azimuth and attitudes by the rough position and orientation provided by vehicle based navigation systems and no less than three couples of azimuth and pitch angles measured by BODP. The proposed approach does not depend on Global Navigation Satellite System (GNSS), thus it is autonomous and difficult to interfere. Meanwhile, it only needs a rough position and orientation as algorithm's iterative initial value, consequently, it does not have high performance requirement for Inertial Navigation System (INS), odometer and other vehicle based navigation systems, even in high precise applications. This paper described the system's working procedure, presented theoretical deviation of the algorithm, and then verified its effectiveness through simulation and vehicle experiments. The simulation and experimental results indicate that the proposed approach can achieve positioning and orientation accuracy of 0.2 m and 20″ respectively in less than 3 min.

The role of local stress perturbation on the simultaneous opening of orthogonal fractures

NASA Astrophysics Data System (ADS)

Boersma, Quinten; Hardebol, Nico; Barnhoorn, Auke; Bertotti, Giovanni; Drury, Martyn

2016-04-01

Orthogonal fracture networks (ladder-like networks) are arrangements that are commonly observed in outcrop studies. They form a particularly dense and well connected network which can play an important role in the effective permeability of tight hydrocarbon or geothermal reservoirs. One issue is the extent to which both the long systematic and smaller cross fractures can be simultaneously critically stressed under a given stress condition. Fractures in an orthogonal network form by opening mode-I displacements in which the main component is separation of the two fracture walls. This opening is driven by effective tensile stresses as the smallest principle stress acting perpendicular to the fracture wall, which accords with linear elastic fracture mechanics. What has been well recognized in previous field and modelling studies is how both the systematic fractures and perpendicular cross fractures require the minimum principle stress to act perpendicular to the fracture wall. Thus, these networks either require a rotation of the regional stress field or local perturbations in stress field. Using a mechanical finite element modelling software, a geological case of layer perpendicular systematic mode I opening fractures is generated. New in our study is that we not only address tensile stresses at the boundary, but also address models using pore fluid pressure. The local stress in between systematic fractures is then assessed in order to derive the probability and orientation of micro crack propagation using the theory of sub critical crack growth and Griffith's theory. Under effective tensile conditions, the results indicate that in between critically spaced systematic fractures, local effective tensile stresses flip. Therefore the orientation of the least principle stress will rotate 90°, hence an orthogonal fracture is more likely to form. Our new findings for models with pore fluid pressures instead of boundary tension show that the magnitude of effective tension in between systematic fractures is reduced but does not remove the occurring stress flip. However, putting effective tension on the boundaries will give overestimates in the reduction of the local effective tensile stress perpendicular to the larger systematic fractures and therefore the magnitude of the stress flip. In conclusion, both model approaches indicate that orthogonal fractures can form while experiencing one regional stress regime. This also means that under these specific loading and locally perturbed stress conditions both sets of orthogonal fractures stay open and can provide a pathway for fluid circulation.

Surface roughness and packaging tightness affect calcium lactate crystallization on Cheddar cheese.

PubMed

Rajbhandari, P; Kindstedt, P S

2014-01-01

Calcium lactate crystals that sometimes form on Cheddar cheese surfaces are a significant expense to manufacturers. Researchers have identified several postmanufacture conditions such as storage temperature and packaging tightness that contribute to crystal formation. Anecdotal reports suggest that physical characteristics at the cheese surface, such as roughness, cracks, and irregularities, may also affect crystallization. The aim of this study was to evaluate the combined effects of surface roughness and packaging tightness on crystal formation in smoked Cheddar cheese. Four 20-mm-thick cross-section slices were cut perpendicular to the long axis of a retail block (~300g) of smoked Cheddar cheese using a wire cutting device. One cut surface of each slice was lightly etched with a cheese grater to create a rough, grooved surface; the opposite cut surface was left undisturbed (smooth). The 4 slices were vacuum packaged at 1, 10, 50, and 90kPa (very tight, moderately tight, loose, very loose, respectively) and stored at 1°C. Digital images were taken at 1, 4, and 8 wk following the first appearance of crystals. The area occupied by crystals and number of discrete crystal regions (DCR) were quantified by image analysis. The experiment was conducted in triplicate. Effects of storage time, packaging tightness, surface roughness, and their interactions were evaluated by repeated-measures ANOVA. Surface roughness, packaging tightness, storage time, and their 2-way interactions significantly affected crystal area and DCR number. Extremely heavy crystallization occurred on both rough and smooth surfaces when slices were packaged loosely or very loosely and on rough surfaces with moderately tight packaging. In contrast, the combination of rough surface plus very tight packaging resulted in dramatic decreases in crystal area and DCR number. The combination of smooth surface plus very tight packaging virtually eliminated crystal formation, presumably by eliminating available sites for nucleation. Cut-and-wrap operations may significantly influence the crystallization behavior of Cheddar cheeses that are saturated with respect to calcium lactate and thus predisposed to form crystals. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Drift-Alfven wave mediated particle transport in an elongated density depression

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

Vincena, Stephen; Gekelman, Walter

Cross-field particle transport due to drift-Alfven waves is measured in an elongated density depression within an otherwise uniform, magnetized helium plasma column. The depression is formed by drawing an electron current to a biased copper plate with cross-field dimensions of 28x0.24 ion sound-gyroradii {rho}{sub s}=c{sub s}/{omega}{sub ci}. The process of density depletion and replenishment via particle flux repeats in a quasiperiodic fashion for the duration of the current collection. The mode structure of the wave density fluctuations in the plane perpendicular to the background magnetic field is revealed using a two-probe correlation technique. The particle flux as a function ofmore » frequency is measured using a linear array of Langmuir probes and the only significant transport occurs for waves with frequencies between 15%-25% of the ion cyclotron frequency (measured in the laboratory frame) and with perpendicular wavelengths k{sub perpendicular}{rho}{sub s}{approx}0.7. The frequency-integrated particle flux is in rough agreement with observed increases in density in the center of the depletion as a function of time. The experiments are carried out in the Large Plasma Device (LAPD) [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the Basic Plasma Science Facility located at the University of California, Los Angeles.« less

Fractures in outcrops in the vicinity of drill hole USW G-4. Yucca Mountain, Nevada; data analysis and compilation

USGS Publications Warehouse

Barton, Christopher C.; Page, William R.; Morgan, Terrance L.

1989-01-01

Fractures on outcrops in the vicinity of drill hole USW G-4, Yucca Mountain, Nevada, were studied in order to contribute to characterization of fractures for hydrologjc, geomechanical, and tectonic modeling of the Yucca Mountain block and to characterize fractures prior to the excavation of a proposed exploratory shaft located near USW G-4. Yucca Mountain is a prospective site for the construction of an underground repository for high-level nuclear waste.Measurements were taken and recorded on 5,000 fractures at 50 outcrop stations primarily in the upper lithophysal unit of the Tiva Canyon Member of the Miocene Paintbrush Tuff. Fracture orientation and surface roughness were recorded for each fracture. Additionally, notes were taken on fracture abutting, crossing, and offsetting relations, swarming, curvature, brecciation, slickensides, and fracture fillings. Frequency distributions of orientation and roughness were plotted and analyzed. Fractures with low roughness coefficients (0-4) group tightly into two sets based on orientation. We conclude that such fractures are cooling joints and that all other fractures are tectonic. The development of small-scale fractures adjacent, subparallel, and possibly related to the Ghost Dance fault has been addressed in a preliminary way based on data collected in this study. Such sympathetic fractures are abundant in the upper cliff unit but not in the upper lithophysal unit.

Non-interferometric determination of optical anisotropy in highly-oriented fibres using transport intensity equation technique

NASA Astrophysics Data System (ADS)

Sokkar, T. Z. N.; El-Farahaty, K. A.; El-Bakary, M. A.; Raslan, M. I.; Omar, E. Z.; Hamza, A. A.

2018-03-01

The optical setup of the transport intensity equation (TIE) technique is developed to be valid for measuring the optical properties of the highly-oriented anisotropic fibres. This development is based on the microstructure models of the highly-oriented anisotropic fibres and the principle of anisotropy. We provide the setup of TIE technique with polarizer which is controlled via stepper motor. This developed technique is used to investigate the refractive indices in the parallel and perpendicular polarization directions of light for the highly-oriented poly (ethylene terephthalate) (PET) fibres and hence its birefringence. The obtained results through the developed TIE technique for PET fibre are compared with that determined experimentally using the Mach-Zehnder interferometer under the same conditions. The comparison shows a good agreement between the obtained results from the developed technique and that obtained from the Mach-Zehnder interferometer technique.

Pretransitional phenomena and pinning in liquid-crystalline blue phases

NASA Astrophysics Data System (ADS)

Demikhov, E.; Stegemeyer, H.; Tsukruk, V.

1992-10-01

Blue phases (BP's) in liquid-crystalline systems of high chirality exhibiting a short cholesteric temperature interval are investigated. In a BP I supercooled with respect to the cholesteric phase, the orientation of the cubic lattice with the (1,1,0) wave vector perpendicular to the substrate is spontaneously turned to a [200] orientation within small areas of several tenths of micrometers in diameter. A pinning of BP I lattice temperature waves is observed on the [200] orientational inhomogeneities. The pinning effect explains the observed saturation of the BP I lattice constant on decreasing temperature and its dependence on the cooling rate observed in supercooled region. A different type of cubic blue phase, BP S (``S'' represents supercooled), is observed transforming reversibly from the supercooled BP I but metastable with respect to the cholesteric phase. The BP S has two scales of order: a long-range orientational blue-phase-like order and a short-range positional smecticlike order.

Inducing and manipulating magnetization in 2D zinc–oxide by strain and external voltage

NASA Astrophysics Data System (ADS)

Taivansaikhan, P.; Tsevelmaa, T.; Rhim, S. H.; Hong, S. C.; Odkhuu, D.

2018-04-01

Two-dimensional (2D) structures that exhibit intriguing magnetic phenomena such as perpendicular magnetic anisotropy and its switchable feature are of great interests in spintronics research. Herein, the density functional theory studies reveal the critical impacts of strain and external gating on vacancy-induced magnetism and its spin direction in a graphene-like single layer of zinc oxide (ZnO). In contrast to the pristine and defective ZnO with an O-vacancy, the presence of a Zn-vacancy induces significant magnetic moments to its first neighboring O and Zn atoms due to the charge deficit. We further predict that the direction of magnetization easy axis reverses from an in-plane to perpendicular orientation under a practically achievable biaxial compressive strain of only ~1–2% or applying an electric field by means of the charge density modulation. This magnetization reversal is mainly driven by the strain- and electric-field-induced changes in the spin–orbit coupled d states of the first-neighbor Zn atom to a Zn-vacancy. These findings open interesting prospects for exploiting strain and electric field engineering to manipulate magnetism and magnetization orientation of 2D materials.

Nanoscale control of stripe-ordered magnetic domain walls by vertical spin transfer torque in La0.67Sr0.33MnO3 film

NASA Astrophysics Data System (ADS)

Wang, Jing; Wu, Shizhe; Ma, Ji; Xie, Lishan; Wang, Chuanshou; Malik, Iftikhar Ahmed; Zhang, Yuelin; Xia, Ke; Nan, Ce-Wen; Zhang, Jinxing

2018-02-01

Stripe-ordered domains with perpendicular magnetic anisotropy have been intensively investigated due to their potential applications in high-density magnetic data-storage devices. However, the conventional control methods (e.g., epitaxial strain, local heating, magnetic field, and magnetoelectric effect) of the stripe-ordered domain walls either cannot meet the demands for miniaturization and low power consumption of spintronic devices or require high strength of the electric field due to the small value of the magnetoelectric effect at room temperature. Here, a domain-wall resistive effect of 0.1% was clarified in La0.67Sr0.33MnO3 thin films between the configurations of current in the plane and perpendicular to the plane of walls. Furthermore, a reversible nanoscale control of the domain-wall re-orientation by vertical spin transfer torque across the probe/film interface was achieved, where a probe voltage of 0.1 V was applied on a manganite-based capacitor. We also demonstrated that the stripe-ordered magnetic domain-wall re-orientation strongly depends on the AC frequency of the scanning probe voltage which was applied on the capacitor.

Quantification of the Effect of Cross-shear on the Wear of Conventional and Highly Cross-linked UHMWPE

PubMed Central

Kang, Lu; Galvin, Alison L.; Brown, Thomas D.; Jin, Zhongmin; Fisher, John

2008-01-01

A computational model has been developed to quantify the degree of cross-shear of a polyethylene pin articulating against a metallic plate, based on the direct simulation of a multidirectional pin-on-plate wear machine. The principal molecular orientation (PMO) was determined for each polymer site. The frictional work in the direction perpendicular to the PMO was assumed to produce the greatest orientation softening (Wang et al., 1997). The cross-shear ratio (CS) was defined as the frictional work perpendicular to the PMO direction, divided by the total frictional work. Cross-shear on the pin contact surface was location-specific, and of continuously changing magnitude because the direction of frictional force continuously changed due to pin rotation. The polymer pin motion was varied from a purely linear track (CS=0) up to a maximum rotation of ±55° (CS=0.254). The relationship between wear factors (K) measured experimentally and theoretically predicted CS was defined using logarithmic functions for both conventional and highly cross-linked UHMWPE. Cross-shear increased the apparent wear factor for both polyethylenes by more than 5-fold compared to unidirectional wear. PMID:17936763

Expanded Equations for Torque and Force on a Cylindrical Permanent Magnet Core in a Large-Gap Magnetic Suspension System

NASA Technical Reports Server (NTRS)

Groom, Nelson J.

1997-01-01

The expanded equations for torque and force on a cylindrical permanent magnet core in a large-gap magnetic suspension system are presented. The core is assumed to be uniformly magnetized, and equations are developed for two orientations of the magnetization vector. One orientation is parallel to the axis of symmetry, and the other is perpendicular to this axis. Fields and gradients produced by suspension system electromagnets are assumed to be calculated at a point in inertial space which coincides with the origin of the core axis system in its initial alignment. Fields at a given point in the core are defined by expanding the fields produced at the origin as a Taylor series. The assumption is made that the fields can be adequately defined by expansion up to second-order terms. Examination of the expanded equations for the case where the magnetization vector is perpendicular to the axis of symmetry reveals that some of the second-order gradient terms provide a method of generating torque about the axis of magnetization and therefore provide the ability to produce six-degree-of-freedom control.

Field gradients can control the alignment of nanorods.

PubMed

Ooi, Chinchun; Yellen, Benjamin B

2008-08-19

This work is motivated by the unexpected experimental observation that field gradients can control the alignment of nonmagnetic nanorods immersed inside magnetic fluids. In the presence of local field gradients, nanorods were observed to align perpendicular to the external field at low field strengths, but parallel to the external field at high field strengths. The switching behavior results from the competition between a preference to align with the external field (orientational potential energy) and preference to move into regions of minimum magnetic field (positional potential energy). A theoretical model is developed to explain this experimental behavior by investigating the statistics of nanorod alignment as a function of both the external uniform magnetic field strength and the local magnetic field variation above a periodic array of micromagnets. Computational phase diagrams are developed which indicate that the relative population of nanorods in parallel and perpendicular states can be adjusted through several control parameters. However, an energy barrier to rotation was discovered to influence the rate kinetics and restrict the utility of this assembly technique to nanorods which are slightly shorter than the micromagnet length. Experimental results concerning the orientation of nanorods inside magnetic fluid are also presented and shown to be in strong agreement with the theoretical work.

Formation of surface relief grating in polymers with pendant azobenzene chromophores as studied by AFM/UFM

NASA Astrophysics Data System (ADS)

Kulikovska, Olga; Gharagozloo-Hubmann, Kati; Stumpe, Joachim; Huey, Bryan D.; Bliznyuk, Valery N.

2012-12-01

We studied peculiarities of the structural reconstruction within holographically recorded gratings on the surface of several different amorphous azobenzene-containing polymers. Under illumination with a light interference pattern, two processes take place in this type of polymer. The first process is the light-induced orientation of azobenzene units perpendicular to the polarization plane of the incident light. The second one is a transfer of macromolecules along the grating vector (i.e. perpendicular to the grating lines). These two processes result in the creation of a volume orientation grating (alternating regions of different direction or degree of molecular orientation) and a surface relief grating (SRG)—i.e. modulation of film thickness. One can assume that both orientation of molecules and their movement might change the local mechanical properties of the material. Therefore, formation of the SRG is expected to result also in modulation of the local stiffness of the polymer film. To reveal and investigate these stiffness changes within the grating, spin-coated polymer films were prepared and the gratings were recorded on them in two different ways: with an orthogonal circular or orthogonal linear polarization of two recording light beams. A combination of atomic force microscopy (AFM) and ultrasonic force microscopy (UFM) techniques was applied for SRG development monitoring. We demonstrate that formation of the phase gratings depends on the chemical structure of polymers being used, polymer film thickness, and recording parameters, with the height of grating structures (depth of modulation) increasing with both the exposure time and the film thickness. UFM images suggest that the slopes of the topographic peaks in the phase gratings exhibit an increased stiffness with respect to the grating depressions.

Scattering from Rock and Rock Outcrops

DTIC Science & Technology

2014-09-30

orientations and size distributions reflect the internal fault organization of the bedrock. The plot in Fig. 3 displays experimentally determined PFA...mechanisms contributing could be scattering from small scale roughness combined with specular scattering from facets oriented close to normal incidence to...Larvik, Norway made with a stereo photogrammetry system. 7 IMPACT/APPLICATIONS The primary work completed over the course of this project

Controlling heat transport and flow structures in thermal turbulence using ratchet surfaces

NASA Astrophysics Data System (ADS)

Sun, Chao; Jiang, Hechuan; Zhu, Xiaojue; Mathai, Varghese; Verzicco, Roberto; Lohse, Detlef

2017-11-01

In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchet-like roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the Large Scale Circulation Roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. This work is financially supported by the Natural Science Foundation of China under Grant No. 11672156, the Dutch Foundation for Fundamental Research on Matter (FOM), the Dutch Technology Foundation (STW) and a VIDI Grant.

Celestial orientation with the sun not in view: lizards use a time-compensated sky polarization compass.

PubMed

Maoret, Francesco; Beltrami, Giulia; Bertolucci, Cristiano; Foà, Augusto

2014-04-01

The present investigation was aimed at testing whether the lizard sky polarization compass is time compensated. For this purpose, ruin lizards, Podarcis sicula, were both trained and tested for orientation inside a Morris water maze under clear skies with the sun not in view. During training, lizards showed a striking bimodal orientation along the training axis, demonstrating their capability of determining the symmetry plane of the sky polarization pattern and thus the use of polarization information in orientation. After reaching criteria, lizards were kept 7 days in a 6-h fast clock-shift treatment and then released with the sun not in view. Six-hour clock-shifted lizards showed a bimodal distribution of directional choices, which was oriented perpendicularly to the training axis, as it was expected on the basis of the clock-shift. The results show that the only celestial diurnal compass mechanism that does not need a direct vision of the sun disk (i.e., the sky polarization compass) is a time-compensated compass.

A statistical study of the low-altitude ionospheric magnetic fields over the north pole of Venus

NASA Astrophysics Data System (ADS)

Zhang, T. L.; Baumjohann, W.; Russell, C. T.; Villarreal, M. N.; Luhmann, J. G.; Teh, W. L.

2015-08-01

Examination of Venus Express (VEX) low-altitude ionospheric magnetic field measurements during solar minimum has revealed the presence of strong magnetic fields at low altitudes over the north pole of Venus. A total of 77 events with strong magnetic fields as VEX crossed the northern polar region were identified between July 2008 and October 2009. These events all have strong horizontal fields, slowly varying with position. Using the superposed epoch method, we find that the averaged peak field is about 45 nT, which is well above the average ambient ionospheric field of 20 nT, with a full width at half maximum duration of 32 s, equivalent to a width of about 300 km. Considering the field orientation preference and spacecraft trajectory geometry, we conclude that these strong fields are found over the northern hemisphere with an occurrence frequency of more than 33% during solar minimum. They do not show a preference for any particular interplanetary magnetic field (IMF) orientation. However, they are found over the geographic pole more often when the interplanetary field is in the Venus orbital plane than when it is perpendicular to the orbital plane of Venus. The structures were found most frequently in the -E hemisphere, determined from the IMF orientation. The enhanced magnetic field is mainly quasi perpendicular to solar wind flow direction, and it is suggested that these structures form in the low-altitude collisional ionosphere where the diffusion and convection times are long.

Cross-fiber Bragg grating transducer

NASA Technical Reports Server (NTRS)

Albin, Sacharia (Inventor); Zheng, Jianli (Inventor); Lavarias, Arnel (Inventor)

2000-01-01

A transducer has been invented that uses specially-oriented gratings in waveguide a manner that allows the simultaneous measurement of physical phenomena (such as shear force, strain and temperature) in a single sensing element. The invention has a highly sensitive, linear response and also has directional sensitivity with regard to strain. The transducer has a waveguide with a longitudinal axis as well as two Bragg gratings. The transducer has a first Bragg grating associated with the waveguide that has an angular orientation .theta..sub.a relative to a perpendicular to the longitudinal axis such that 0.degree.<.theta..sub.a <.theta..sub.max. The second Bragg grating is associated with the waveguide in such a way that the angular orientation .theta..sub.b of the grating relative to a perpendicular to the longitudinal axis is (360.degree.-.theta..sub.max)<.theta..sub.b <360.degree.. The first Bragg grating can have a periodicity .LAMBDA..sub.a and the second Bragg grating can have a periodicity .LAMBDA..sub.b such that the periodicity .LAMBDA..sub.a of the first Bragg grating does not equal the periodicity .LAMBDA..sub.b of the second Bragg grating. The angle of the gratings can be such that .theta..sub.a =360.degree.-.theta..sub.b. The waveguide can assume a variety of configurations, including an optical fiber, a rectangular waveguide and a planar waveguide. The waveguide can be fabricated of a variety of materials, including silica and polymer material.

Effects of molecular asymmetry of optically active molecules on the polarization properties of multiply scattered light

NASA Astrophysics Data System (ADS)

Vitkin, I. Alex; Laszlo, Richard D.; Whyman, Claire L.

2002-02-01

The use of polarized light for investigation of optically turbid systems has generated much recent interest since it has been shown that multiple scattering does not fully scramble the incident polarization states. It is possible under some conditions to measure polarization signals in diffusely scattered light, and use this information to characterize the structure or composition of the turbid medium. Furthermore, the idea of quantitative detection of optically active (chiral) molecules contained in such a system is attractive, particularly in clinical medicine where it may contribute to the development of a non-invasive method of glucose sensing in diabetic patients. This study uses polarization modulation and synchronous detection in the perpendicular and in the exact backscattering orientations to detect scattered light from liquid turbid samples containing varying amounts of L and D (left and right) isomeric forms of a chiral sugar. Polarization preservation increased with chiral concentrations in both orientations. In the perpendicular orientation, the optical rotation of the linearly polarized fraction also increased with the concentration of chiral solute, but in different directions for the two isomeric forms. There was no observed optical rotation in the exact backscattering geometry for either isomer. The presence of the chiral species is thus manifest in both detection directions, but the sense of the chiral asymmetry is not resolvable in retroreflection. The experiments show that useful information may be extracted from turbid chiral samples using polarized light.

Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films

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

Arges, Christopher G.; Kambe, Yu; Suh, Hyo Seon

Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which aremore » anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm(-1) at 20 degrees C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport.« less

Modification of local order in FePd films by low energy He{sup +} irradiation

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

Merkel, D. G.; Tancziko, F.; Sajti, Sz.

2008-07-01

Owing to their strong perpendicular magnetic anisotropy, FePd, CoPd, and their Co(Fe)Pt counterparts are candidate materials for ultrahigh density magnetic recording. The stability and magnetic properties of such films are largely dependent on the orientation and local distribution of the L1{sub 0} FePd phase fraction. Therefore, the formation and transformation of the L1{sub 0} phase in such thin films have been the subject of continued interest. Highly ordered epitaxial FePd(001) thin films (with an L1{sub 0} phase fraction of 0.81) were prepared by molecular-beam epitaxy on a MgO(001) substrate. The effect of postgrown room temperature, 130 keV He{sup +} irradiationmore » was investigated at fluences up to 14.9x10{sup 15} ions/cm{sup 2}. X-ray diffraction and conversion electron Moessbauer spectroscopy revealed that with increasing fluence, the L1{sub 0} FePd phase decomposes into the face centered cubic phase with random Fe and Pd occupation of the sites. A partially ordered local environment exhibiting a large hyperfine magnetic field also develops. Upon He{sup +} irradiation, the lattice parameter c of the FePd L1{sub 0} structure increases and the long range order parameter S steeply decreases. The Fe-Fe nearest-neighbor coordination in the Fe-containing environments increases on average from Fe{sub 47}Pd{sub 53} to Fe{sub 54}Pd{sub 46}, indicating a tendency of formation iron-rich clusters. The equilibrium parameters corresponding to the equiatomic L1{sub 0} phase were found at different fluences by conversion electron Moessbauer spectroscopy and by x-ray diffraction a difference, from which a plane-perpendicular compressive stress and a corresponding in-plane tensile stress are conjectured. The steep increase in the interface roughness above 7.4x10{sup 15} ions/cm{sup 2} is interpreted as a percolation-type behavior related to the high diffusion anisotropy in the L1{sub 0} phase.« less

Development of microchannel plate x-ray optics

NASA Technical Reports Server (NTRS)

Kaaret, Philip; Chen, Andrew

1994-01-01

The goal of this research program was to develop a novel technique for focusing x-rays based on the optical system of a lobster's eye. A lobster eye employs many closely packed reflecting surfaces arranged within a spherical or cylindrical shell. These optics have two unique properties: they have unlimited fields of view and can be manufactured via replication of identical structures. Because the angular resolution is given by the ratio of the size of the individual optical elements to the focal length, optical elements with sizes on the order of one hundred microns are required to achieve good angular resolution with a compact telescope. We employed anisotropic etching of single crystal silicon wafers for the fabrication of micron-scale optical elements. This technique, commonly referred to as silicon micromachining, is based on silicon fabrication techniques developed by the microelectronics industry. An anisotropic etchant is a chemical which etches certain silicon crystal planes much more rapidly than others. Using wafers in which the slowly etched crystal planes are aligned perpendicularly to the wafer surface, it is possible to etch a pattern completely through a wafer with very little distortion. Our optics consist of rectangular pores etched completely through group of zone axes (110) oriented silicon wafers. The larger surfaces of the pores (the mirror elements) were aligned with the group of zone axes (111) planes of the crystal perpendicular to the wafer surface. We have succeeded in producing silicon lenses with a geometry suitable for 1-d focusing x-ray optics. These lenses have an aspect ratio (40:1) suitable for x-ray reflection and have very good optical surface alignment. We have developed a number of process refinements which improved the quality of the lens geometry and the repeatability of the etch process. A significant progress was made in obtaining good optical surface quality. The RMS roughness was decreased from 110 A for our initial lenses to 30 A in the final lenses. A further factor of three improvement in surface quality is required for the production of efficient x-ray optics. In addition to the silicon fabrication, an x-ray beam line was constructed at Columbia for testing the optics.

Mechanical signals in plant development: a new method for single cell studies

NASA Technical Reports Server (NTRS)

Lynch, T. M.; Lintilhac, P. M.

1997-01-01

Cell division, which is critical to plant development and morphology, requires the orchestration of hundreds of intracellular processes. In the end, however, cells must make critical decisions, based on a discrete set of mechanical signals such as stress, strain, and shear, to divide in such a way that they will survive the mechanical loads generated by turgor pressure and cell enlargement within the growing tissues. Here we report on a method whereby tobacco protoplasts swirled into a 1.5% agarose entrapment medium will survive and divide. The application of a controlled mechanical load to agarose blocks containing protoplasts orients the primary division plane of the embedded cells. Photoelastic analysis of the agarose entrapment medium can identify the lines of principal stress within the agarose, confirming the hypothesis that cells divide either parallel or perpendicular to the principal stress tensors. The coincidence between the orientation of the new division wall and the orientation of the principal stress tensors suggests that the perception of mechanical stress is a characteristic of individual plant cells. The ability of a cell to determine a shear-free orientation for a new partition wall may be related to the applied load through the deformation of the matrix material. In an isotropic matrix a uniaxial load will produce a rotationally symmetric strain field, which will define a shear-free plane. Where high stress intensities combine with the loading geometry to produce multiaxial loads there will be no axis of rotational symmetry and hence no shear free plane. This suggests that two mechanisms may be orienting the division plane, one a mechanism that works in rotationally symmetrical fields, yielding divisions perpendicular to the compressive tensor, parallel to the long axis of the cell, and one in asymmetric fields, yielding divisions parallel to the short axis of the cell and the compressive tensor.

Indium hexagonal island as seed-layer to boost a-axis orientation of AlN thin films

NASA Astrophysics Data System (ADS)

Redjdal, N.; Salah, H.; Azzaz, M.; Menari, H.; Manseri, A.; Guedouar, B.; Garcia-Sanchez, A.; Chérif, S. M.

2018-06-01

Highly a-axis oriented aluminum nitride films have been grown on Indium coated (100) Si substrate by DC reactive magnetron sputtering. It is shown that In incorporated layer improve the extent of preferential growth along (100) axis and form dense AlN films with uniform surface and large grains, devoid of micro-cracks. As revealed by SEM cross section images, AlN structure consists of oriented columnar grains perpendicular to the Si surface, while AlN/In structure results in uniformely tilted column. SEM images also revealed the presence of In hexagonal islands persistent throughout the entire growth. Micro -Raman spectroscopy of the surface and the cross section of the AlN/In grown films evidenced their high degree of homogeneity and cristallinity.

Stress dependence of the Raman spectrum of polycrystalline barium titanate in presence of localized domain texture

NASA Astrophysics Data System (ADS)

Sakashita, Tatsuo; Deluca, Marco; Yamamoto, Shinsuke; Chazono, Hirokazu; Pezzotti, Giuseppe

2007-06-01

The stress dependence of the Raman spectrum of polycrystalline barium titanate (BaTiO3, BT) ceramics has been examined with microprobe polarized Raman spectroscopy. The angular dependence of the Raman spectrum of the tetragonal BT crystal has been theoretically established, enabling us to assess the stress dependence of selected spectral modes without the influence of crystallographic domain orientation. Upon considering the frequency shift of selected Raman modes as a function of orientation between the crystallographic axis and the polarization vector of incident and scattered light, a suitable instrumental configuration has been selected, which allowed a direct residual stress measurement according to a modified piezospectroscopic procedure. The analysis is based on the selection of mixed photostimulated spectral modes in two perpendicular angular orientations.

X-ray diffraction and Raman investigations of thickness dependent stress effects on Pb(ZrxTi1-x)O3 thin films

NASA Astrophysics Data System (ADS)

Lappalainen, Jyrki; Lantto, Vilho; Frantti, Johannes; Hiltunen, Jussi

2006-06-01

Microstructure, film orientation, and optical transmission spectra of polycrystalline Nd-modified Pb(ZrxTi1-x)O3 films were studied as a function of film thickness. Pulsed laser deposition was used for the fabrication of films with thickness from 80to465nm on single-crystal MgO(100) substrates. Raman spectroscopy, x-ray diffraction, and spectrophotometry measurements were utilized in the film characterization. With the decreasing film thickness, films first oriented with c axis perpendicular to film surface, and then, after some critical thickness, changed to a-axis orientation. At the same time, compressive stress increased up to 1.3GPa and a clear blueshift of the optical absorption edge was found in transmission spectra.

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

Jung, Min-Cherl; Zhang, Dongrong; Nikiforov, Gueorgui O.

Ultrathin (<6 nm) polycrystalline films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-P) are deposited with a two-step spin-coating process. The influence of spin-coating conditions on morphology of the resulting film was examined by atomic force microscopy. Film thickness and RMS surface roughness were in the range of 4.0–6.1 and 0.6–1.1 nm, respectively, except for small holes. Polycrystalline structure was confirmed by grazing incidence x-ray diffraction measurements. Near-edge x-ray absorption fine structure measurements suggested that the plane through aromatic rings of TIPS-P molecules was perpendicular to the substrate surface.

L10-Ordered Thin Films with High Perpendicular Magnetic Anisotropy for STT-MRAM Applications

NASA Astrophysics Data System (ADS)

Huang, Efrem Yuan-Fu

The objective of the research conducted herein was to develop L10-ordered materials and thin film stack structures with high perpendicular magnetic anisotropy (PMA) for spin-transfertorque magnetoresistive random access memory (STT-MRAM) applications. A systematic approach was taken in this dissertation, culminating in exchange coupled L1 0-FePt and L10- MnAl heterogeneous structures showing great promise for developing perpendicular magnetic tunnel junctions (pMTJs) with both high thermal stability and low critical switching current. First, using MgO underlayers on Si substrates, sputtered MnAl films were systematically optimized, ultimately producing a Si substrate/MgO (20 nm)/MnAl (30)/Ta (5) film stack with a high degree of ordering and large PMA. Next, noting the incompatibility of insulating MgO underlayers with industrial-scale CMOS processes, attention was turned to using conductive underlayers. TiN was found to excel at promoting growth of L10-MnAl, with optimized films showing improved magnetic properties over those fabricated on MgO underlayers. The use of different post-annealing processes was then studied as an alternative to in situ annealing. Rapid thermal annealing (RTA) was found to produce PMA in films at lower annealing temperatures than tube furnace annealing, but tube furnace annealing produced films with higher maximum PMA than RTA. While annealed samples had lower surface roughness than those ordered by high in situ deposition temperatures, relying solely on annealing to achieve L10-ordering resulted drastically reduced PMA. Finally, heterogeneous L10-ordered FePt/MgO/MnAl film stacks were explored for pMTJs. Film stacks with MgO barrier layers thinner than 2 nm showed significant interdiffusion between the FePt and MnAl, while film stacks with thicker MgO barrier layers exhibited good ordering and high PMA in both the FePt and MnAl films. It is believed that this limitation is caused by the roughness of the underlying FePt, which was thicker than 2 nm. Unfortunately, MgO barrier layers thinner than 2 nm are needed to make good MTJs. With further study, thin, continuous barriers may be achievable for high-PMA, L10- ordered materials with more materials exploration, deposition optimization, and more advanced thin film processing techniques and fabrication equipment. Use of appropriate underlayers, capping layers, dopant elements, and improved fabrication techniques may help reduce surface roughness while preserving PMA. If smooth electrodes can be developed, the heterogeneous structures discussed have great potential in taking advantage of exchange coupling for developing pMTJs with both high thermal stability and low critical switching current. (Abstract shortened by ProQuest.).

Polarized pump-probe spectroscopy of exciton transport in bacteriochlorophyll a- protein from Prosthecochloris aestuarii

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

Causgrove, T.P.; Yang, S.; Struve, W.S.

1988-11-17

The polarization of the Q/sub x/ electronic transition in the BChl a-protein complex from the green sulfur bacterium Prosthecochloris aestuarii was monitored by pump-probe spectroscopy with approx. 1.5-ps resolution at 598, 603, and 609 nm. At 603 nm, the polarization decays with a mean lifetime of 4.78 ps. Substantial residual polarization appears at long times (the ratio A/sub parallel//A/sub perpendicular/ of optical densities for probe pulses polarized parallel and perpendicular to the excitation pulse is approx. 1.7) in consequence of the nonrandom chromophore orientations. The polarized pump-probe transients have been analyzed in terms of an exciton hopping model that incorporatesmore » the known geometry of the BChl a-protein.« less

Electrohydrodynamic Quincke rotation of a prolate ellipsoid

NASA Astrophysics Data System (ADS)

Brosseau, Quentin; Hickey, Gregory; Vlahovska, Petia M.

2017-01-01

We study experimentally the occurrence of spontaneous spinning (Quincke rotation) of an ellipsoid in a uniform direct current (dc) electric field. For an ellipsoid suspended in an unbounded fluid, we find two stable states characterized by the orientation of the ellipsoid long axis relative to the applied electric field: spinless (parallel) and spinning (perpendicular). The phase diagram of ellipsoid behavior as a function of field strength and aspect ratio is in close agreement with the theory of Cēbers et al. [Phys. Rev. E 63, 016301 (2000)], 10.1103/PhysRevE.63.016301. We also investigate the dynamics of the ellipsoidal Quincke rotor resting on a planar surface with normal perpendicular to the field direction. We find behaviors, such as swinging (long axis oscillating around the applied field direction) and tumbling, due to the confinement.

Cholesterol orientation and tilt modulus in DMPC bilayers

PubMed Central

Khelashvili, George; Pabst, Georg; Harries, Daniel

2010-01-01

We performed molecular dynamics (MD) simulations of hydrated bilayers containing mixtures of dimyristoylphosphatidylcholine (DMPC) and Cholesterol at various ratios, to study the effect of cholesterol concentration on its orientation, and to characterize the link between cholesterol tilt and overall phospholipid membrane organization. The simulations show a substantial probability for cholesterol molecules to transiently orient perpendicular to the bilayer normal, and suggest that cholesterol tilt may be an important factor for inducing membrane ordering. In particular, we find that as cholesterol concentration increases (1%–40% cholesterol) the average cholesterol orientation changes in a manner strongly (anti)correlated with the variation in membrane thickness. Furthermore, cholesterol orientation is found to be determined by the aligning force exerted by other cholesterol molecules. To quantify this aligning field, we analyzed cholesterol orientation using, to our knowledge, the first estimates of the cholesterol tilt modulus χ from MD simulations. Our calculations suggest that the aligning field that determines χ is indeed strongly linked to sterol composition. This empirical parameter (χ) should therefore become a useful quantitative measure to describe cholesterol interaction with other lipids in bilayers, particularly in various coarse-grained force fields. PMID:20518573

Crystalisation of aqueous ferrofluids at the free liquid interface investigated by specular and off-specular x-ray reflectometry

NASA Astrophysics Data System (ADS)

Gapon, I. V.; Petrenko, V. I.; Soltwedel, O.; Khaydukov, Yu N.; Kubovcikova, M.; Kopcansky, P.; Bulavin, L. A.; Avdeev, M. V.

2018-03-01

Structural organization of nanoparticles from aqueous ferrofluids on free liquid surface was studied by X-ray reflectometry. The observed layered structure at interface is associated with the evaporation of the solvent. By orienting an external magnetic during evaporation of the aqueos ferrofluids their structural organization can be manipulated. For a magnetic field applied perpendicular to the surface a more pronounced ordering along the surface normal is observed as in the case of a parallel field. Independent on the orientation of the magantic field a ∼ 20 μm thick surface layer of depleted nanoparticle concentration is found at the interface.

Anisotropic Effects on the Thermoelectric Properties of Highly Oriented Electrodeposited Bi2Te3 Films

PubMed Central

Manzano, Cristina V.; Abad, Begoña; Muñoz Rojo, Miguel; Koh, Yee Rui; Hodson, Stephen L.; Lopez Martinez, Antonio M.; Xu, Xianfan; Shakouri, Ali; Sands, Timothy D.; Borca-Tasciuc, Theodorian; Martin-Gonzalez, Marisol

2016-01-01

Highly oriented [1 1 0] Bi2Te3 films were obtained by pulsed electrodeposition. The structure, composition, and morphology of these films were characterized. The thermoelectric figure of merit (zT), both parallel and perpendicular to the substrate surface, were determined by measuring the Seebeck coefficient, electrical conductivity, and thermal conductivity in each direction. At 300 K, the in-plane and out-of-plane figure of merits of these Bi2Te3 films were (5.6 ± 1.2)·10−2 and (10.4 ± 2.6)·10−2, respectively. PMID:26776726

The Impact of Discontinuity Front Orientation on the Accuracy of L1 Space Weather Forecasting

NASA Astrophysics Data System (ADS)

Szabo, A.

2013-12-01

Current space weather forecasting from the Sun-Earth first Lagrange (L1) point assumes that all observed solar wind discontinuity fronts (interplanetary shocks, ICME boundaries) are perpendicular to the Sun-Earth line and are propagating radially out from eh Sun. In reality, these weather fronts can have significantly tilted orientation. Combined ACE, Wind and Soho observations allow the quantification of this effect. With the launch of the DSCOVR spacecraft in early 2015, dual real-time solar wind measurements will become available (at least at some time). Algorithms and their impact exploiting this unique scenario will be discussed.

Dielectric, piezoelectric, and ferroelectric properties of grain-orientated Bi3.25La0.75Ti3O12 ceramics

NASA Astrophysics Data System (ADS)

Liu, Jing; Shen, Zhijian; Yan, Haixue; Reece, Michael J.; Kan, Yanmei; Wang, Peiling

2007-11-01

By dynamic forging during Spark Plasma Sintering (SPS), grain-orientated ferroelectric Bi3.25La0.75Ti3O12 (BLT) ceramics were prepared. Their ferroelectric, piezoelectric, and dielectric properties are anisotropic. The textured ceramics parallel and perpendicular to the shear flow directions have similar thermal depoling behaviors. The d33 piezoelectric coefficient of BLT ceramics gradually reduces up to 350 °C; it then drops rapidly. The broadness of the dielectric constant and loss peaks and the existence of d33 above the permittivity peak, Tm, show that the BLT ceramic has relaxor-like behavior.

Quantitative Mapping of Surface Texture on the Northern Polar Residual Cap of Mars

NASA Astrophysics Data System (ADS)

Milkovich, S. M.; Byrne, S.; Russell, P. S.

2010-12-01

The northern polar residual cap (NPRC) of Mars is a water ice deposit with a rough surface made up of pits, knobs, and linear depressions on scales of tens of meters [1]. This roughness manifests as a series of bright and dark patches in visible images. Spectral data indicate that the surface of the NPRC is composed of large-grained (and therefore old) water ice. Due to the presence of this old ice, it is thought that the NPRC is in a current state of net loss of material [2]. The NPRC provides a link between the current martian climate and the historical climate recorded within the layers of the underlying north polar layered deposits. By characterizing and mapping the variations in surface texture of the NPRC, we seek to understand what factors (distance from the pole, GCM and mesoscale wind direction predictions, etc) are currently at work in resurfacing the deposit, and may have been at work in shaping the layers below. Maps of NPRC texture wavelength and orientation are being produced from HiRISE images. Two-dimensional Fourier analysis is performed upon a 256 meter x 256 meter region (corresponding to 512 x 512 pixels in 0.5 cm/pxl images, or 1024 x 1024 pixels in 0.25 cm/pxl images) within each image analyzed. The dominant wavelength of the resulting peak power spectrum corresponds to the average size of a pit-knob pair in the image, and so is a proxy for the scale of the surface roughness. The orientation of the surface roughness (i.e., the orientation of a chain of pits and mounds) is measured from a narrow range of wavelengths encompassing the dominant wavelength. We will report on how the dominant wavelengths and orientations of this surface texture vary with location and what that implies for the processes currently shaping this landscape. [1] P. C. Thomas et al, Nature 404, 161-164, 2000 [2]Y. Langevin et al, Science 307, 5715, 1581-1584, 2005.

Melt-induced seismic anisotropy and magma assisted rifting in Ethiopia: Evidence from surface waves

NASA Astrophysics Data System (ADS)

Bastow, I. D.; Pilidou, S.; Kendall, J.-M.; Stuart, G. W.

2010-06-01

The East African rift in Ethiopia is unique worldwide because it captures the final stages of transition from continental rifting to seafloor spreading. A recent study there has shown that magma intrusion plays an important role during the final stages of continental breakup, but the mechanism by which it is incorporated into the extending plate remains ambiguous: wide-angle seismic data and complementary geophysical tools such as gravity analysis are not strongly sensitive to the geometry of subsurface melt intrusions. Studies of shear wave splitting in near-vertical SKS phases beneath the transitional Main Ethiopian Rift (MER) provide strong and consistent evidence for a rift-parallel fast anisotropic direction. However, it is difficult to discriminate between oriented melt pocket (OMP) and lattice preferred orientation (LPO) causes of anisotropy based on SKS study alone. The speeds of horizontally propagating Love (SH) and Rayleigh (SV) waves vary in similar fashions with azimuth for LPO- and OMP-induced anisotropy, but their relative change is distinctive for each mechanism. This diagnostic is exploited by studying the propagation of surface waves from a suite of azimuths across the MER. Anisotropy is roughly perpendicular to the absolute plate motion direction, thus ruling out anisotropy due to the slowly moving African Plate. Instead, three mechanisms for anisotropy act beneath the MER: periodic thin layering of seismically fast and slow material in the uppermost ˜10 km, OMP between ˜20-75 km depth, and olivine LPO in the upper mantle beneath. The results are explained best by a model in which low aspect ratio melt inclusions (dykes and veins) are being intruded into an extending plate during late stage breakup. The observations from Ethiopia join a growing body of evidence from rifts and passive margins worldwide that shows magma intrusion plays an important role in accommodating extension without marked crustal thinning.

Microwave Power Combiners for Signals of Arbitrary Amplitude

NASA Technical Reports Server (NTRS)

Conroy, Bruce; Hoppe, Daniel

2009-01-01

Schemes for combining power from coherent microwave sources of arbitrary (unequal or equal) amplitude have been proposed. Most prior microwave-power-combining schemes are limited to sources of equal amplitude. The basic principle of the schemes now proposed is to use quasi-optical components to manipulate the polarizations and phases of two arbitrary-amplitude input signals in such a way as to combine them into one output signal having a specified, fixed polarization. To combine power from more than two sources, one could use multiple powercombining stages based on this principle, feeding the outputs of lower-power stages as inputs to higher-power stages. Quasi-optical components suitable for implementing these schemes include grids of parallel wires, vane polarizers, and a variety of waveguide structures. For the sake of brevity, the remainder of this article illustrates the basic principle by focusing on one scheme in which a wire grid and two vane polarizers would be used. Wire grids are the key quasi-optical elements in many prior equal-power combiners. In somewhat oversimplified terms, a wire grid reflects an incident beam having an electric field parallel to the wires and passes an incident beam having an electric field perpendicular to the wires. In a typical prior equal-power combining scheme, one provides for two properly phased, equal-amplitude signals having mutually perpendicular linear polarizations to impinge from two mutually perpendicular directions on a wire grid in a plane oriented at an angle of 45 with respect to both beam axes. The wires in the grid are oriented to pass one of the incident beams straight through onto the output path and to reflect the other incident beam onto the output path along with the first-mentioned beam.

Changes in the Orientation of Local Stresses Prior to and During Magmatic Activity at the Soufriere Hills Volcano, Montserrat

NASA Astrophysics Data System (ADS)

Roman, D. C.; Neuberg, J.; Luckett, R. R.; White, R. A.

2005-12-01

Systematic changes in the orientation of double-couple fault-plane solutions (FPS) for volcanotectonic (VT) earthquakes have been linked to stress changes induced by the dilation of the magmatic conduit system and may precede the onset of eruption by weeks to months, potentially providing advance warning of an impending eruption. To determine whether analysis of FPS for VT earthquakes recorded during the ongoing eruption of the Soufriere Hills Volcano, Montserrat, could be used to detect the arrival of magma in the mid-level conduit system, we produced a large catalog of high-quality FPS that spanned several phases of the eruption, and then analyzed this catalog to determine whether a temporal correlation exists between eruptive activity and FPS orientation. We repicked VT earthquakes recorded on the Montserrat Volcano Observatory analog and digital seismic networks from the beginning of the eruption in 1995 to May 2005 and relocated them using a 1D velocity model. We then determined well-constrained FPS for the relocated earthquakes. Well-contrained FPS for 607 VT earthquakes indicate primarily oblique strike-slip faulting. In August 1995 (prior to the onset of lava extrusion in September 1995), October 1996-June 1997 (during a period of dome-building), May-November 1999 (prior to the restart of the eruption in November 1999 following a year-long pause), and April-May 2005 (prior to the restart of the eruption in June-August 2005 following a two year pause), FPS pressure (p-) axes are oriented approximately perpendicular to the inferred direction of regional maximum compressive stress around Montserrat. In contrast, FPS p-axes for earthquakes accompanying a pause in the eruption in 1998-1999, and from December 1999-March 2005 are oriented approximately parallel to regional maximum compression. VT earthquakes with FPS p-axes oriented perpendicular to regional maximum compression are thought to reflect local stresses induced by the inflation of a dike-like magmatic conduit system beneath Soufriere Hills prior to and during episodes of eruption.

Experimental investigation on in-plane/out-of-plane vortex-induced vibrations of curved cylinder in parallel and perpendicular flows

NASA Astrophysics Data System (ADS)

Srinil, Narakorn; Ma, Bowen; Zhang, Licong

2018-05-01

This study is motivated by an industrial need to better understand the vortex-induced vibration (VIV) of a curved structure subject to current flows with varying directions whose data for model calibration and validation are lacking. In this paper, new experimental investigations on the two-degree-of-freedom in-plane/out-of-plane VIV of a rigid curved circular cylinder immersed in steady and uniform free-stream flows are presented. The principal objective is to examine how the approaching flow direction versus the cylinder curvature plane affects cross-flow and in-line VIV and the associated hydrodynamic properties. This is achieved by testing the curved cylinder in 3 different flow orientations comprising the parallel flows aligned with the curvature vertical plane in convex and concave configurations, and the flows perpendicular to the curvature plane. The case of varying flow velocities in a subcritical flow range with a maximum Reynolds number of about 50,000 is considered for the curved cylinder with a low mass ratio and damping ratio. Experimental results are presented and discussed in terms of the cylinder response amplitudes, inclination angles, mean displacements, motion trajectories, oscillation frequencies, hydrodynamic forces, relative phases, fluid excitation and added inertia coefficients. Comparisons with other experimental results of curved and straight cylinder VIV are also presented. The experiments highlight the important effects of cylinder curvature versus flow orientation on the combined cross-flow/in-line VIV. The maximum (minimum) responses occur in the perpendicular (convex) flow case whereas the extended lower-branch responses occur in the concave flow case. For perpendicular flows, some meaningful features are observed, including the appearances of cross-flow mean displacements and asymmetric eight-shaped motion trajectories due to multiple 2:1:1 resonances where two out-of-plane and one in-plane dominant frequencies are simultaneously excited. Overall VIV phenomena caused by the system asymmetry should be recognised in a prediction model and design codes to capture the combined effects of curved configuration and approaching flow direction.

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

NASA Astrophysics Data System (ADS)

Shepley, Philippa M.; Tunnicliffe, Harry; Shahbazi, Kowsar; Burnell, Gavin; Moore, Thomas A.

2018-04-01

We study the magnetic properties of perpendicularly magnetized Pt/Co/Ir thin films and investigate the domain-wall creep method of determining the interfacial Dzyaloshinskii-Moriya (DM) interaction in ultrathin films. Measurements of the Co layer thickness dependence of saturation magnetization, perpendicular magnetic anisotropy, and symmetric and antisymmetric (i.e., DM) exchange energies in Pt/Co/Ir thin films have been made to determine the relationship between these properties. We discuss the measurement of the DM interaction by the expansion of a reverse domain in the domain-wall creep regime. We show how the creep parameters behave as a function of in-plane bias field and discuss the effects of domain-wall roughness on the measurement of the DM interaction by domain expansion. Whereas modifications to the creep law with DM field and in-plane bias fields have taken into account changes in the energy barrier scaling parameter α , we find that both α and the velocity scaling parameter v0 change as a function of in-plane bias field.

Why does a cleavage plane develop parallel to the spindle axis in conical sand dollar eggs? A key question for clarifying the mechanism of contractile ring positioning.

PubMed

Yoshigaki, Tomoyoshi

2003-03-21

Three types of models have been proposed about how the mitotic apparatus determines the position of the cleavage furrow in animal cells. In the first and second types, the contractile ring appears in a cortical region that least and most astral microtubules reach, respectively. The third type is that the spindle midzone positions the contractile ring. In the previous study, a new model was proposed through analyses of cytokinesis in sand dollar and sea urchin eggs. Gradients of the surface density of microtubule plus ends are assumed to drive membrane proteins whose accumulation causes the formation of contractile-ring microfilaments. In the present study, the validity of each model is examined by simulating the furrow formation in conical sand dollar eggs with the mitotic apparatus oriented perpendicular to the cone axis. The new model predicts that unilateral furrows with cleavage planes roughly parallel to the spindle axis appear between the mitotic apparatus and the vertex besides the normally positioned furrow. The predictions are consistent with the observations by Rappaport & Rappaport (1994, Dev. Biol.164, 258-266). The other three types of models do not predict the formation of the ectopic furrows. Furthermore, it is pointed out that only the new model has the ability to explain the geometrical relationship between the mitotic apparatus and the contractile ring under various experimental conditions. These results strongly suggest the real existence of the membrane proteins postulated in the model.

Structural Properties of Alternate Monatomic Layered [Fe/Co]n Epitaxial Films on MgO Substrate

NASA Astrophysics Data System (ADS)

Chu, In Chang; Saki, Yoshinobu; Kawasaki, Shohei; Doi, Masaaki; Sahashi, Masashi

2008-06-01

Body-centered-cubic (bcc) Fe50Co50 material is reported to show a high bulk spin scattering coefficient on current perpendicular to plane-giant magneto-resistance (CPP-GMR) system. But the origin of that phenomenon does not make sure yet. We prepared artificially alternate monatomic layered (AML) [Fe/Co] 41 MLs epitaxial films (Ts: 75, 250 °C) by monatomic deposition method and investigated the topology of AML [Fe/Co]n epitaxial films on MgO substrate with different orientation (001), (011) by the scanning tunnel microscopy (STM) and reflection high energy electron diffraction (RHEED), which we could confirm Frank-van der Merwe (FM) growth mode for AML [Fe/Co]n on MgO(001) and Volmer-Weber (VW) growth mode for that on Mg(011). The roughness of surface, Ra (0.20 nm) of AML [Fe/Co] 41 MLs epitaxial film grown at 75 °C on MgO(001) is smaller than that (0.46 nm) of AML [Fe/Co] grown at 250 °C on MgO(001), which has the large terraces of over 50 nm (Ra: 0.17 nm), even though there are some valleys between large terraces. Moreover we confirmed the structural properties of trilayered epitaxial films with AML [Fe/Co]n (Ra: 0.18 nm) and Fe50Co50 alloy epitaxial film on Au electrode by RHEED before confirming the characteristics of CPP-GMR devices.

Flow deflection over a foredune

NASA Astrophysics Data System (ADS)

Hesp, Patrick A.; Smyth, Thomas A. G.; Nielsen, Peter; Walker, Ian J.; Bauer, Bernard O.; Davidson-Arnott, Robin

2015-02-01

Flow deflection of surface winds is common across coastal foredunes and blowouts. Incident winds approaching obliquely to the dune toe and crestline tend to be deflected towards a more crest-normal orientation across the stoss slope of the foredune. This paper examines field measurements for obliquely incident winds, and compares them to computational fluid dynamics (CFD) modelling of flow deflection in 10° increments from onshore (0°) to alongshore (90°) wind approach angles. The mechanics of flow deflection are discussed, followed by a comparative analysis of measured and modelled flow deflection data that shows strong agreement. CFD modelling of the full range of onshore to alongshore incident winds reveals that deflection of the incident wind flow is minimal at 0° and gradually increases as the incident wind turns towards 30° to the dune crest. The greatest deflection occurs between 30° and 70° incident to the dune crest. The degree of flow deflection depends secondarily on height above the dune surface, with the greatest effect near the surface and toward the dune crest. Topographically forced flow acceleration ("speed-up") across the stoss slope of the foredune is greatest for winds less than 30° (i.e., roughly perpendicular) and declines significantly for winds with more oblique approach angles. There is less lateral uniformity in the wind field when the incident wind approaches from > 60° because the effect of aspect ratio on topographic forcing and streamline convergence is less pronounced.

Concerning the Motion of FTEs and Attendant Signatures

NASA Technical Reports Server (NTRS)

Sibeck, David G.

2010-01-01

We employ the Cooling et al. [2001] model to predict the location, orientation, and motion of flux transfer events (FTEs) generated along finite length component and anti parallel reconnection lines for typical solar wind plasma conditions and various interplanetary magnetic field (IMF) orientations in the plane perpendicular to the SunEarth line at the solstices and equinoxes. For duskward and northward or southward IMF orientations, events formed by component reconnection originate along reconnection curves passing through the sub solar point that tilt from southern dawn to northern dusk. They maintain this orientation as they move either northward into the northern dawn quadrant or southward into the southern dusk quadrant. By contrast, events formed by antiparallel reconnection originate along reconnection curves running from northern dawn to southern dusk in the southern dawn and northern dusk quadrants and maintain these orientations as they move anti sunward into both these quadrants. Although both the component and antiparallel reconnection models can explain previously reported event orientations on the southern dusk magnetopause during intervals of northward and dawn ward IMF orientation, only the component model explains event occurrence near the subsolar magnetopause during intervals when the IMF does not point due southward.

Preparation and characterization of oriented poly(vinyl alcohol)/carbon nanotube composite nanofibers

NASA Astrophysics Data System (ADS)

Shimizu, Akikazu; Kato, Hayato; Sato, Taiga; Kushida, Masahito

2017-07-01

Oriented nanofiber mats blended with carbon nanotubes (CNTs) are expected to be applied as cell seeding scaffolds. Biomaterials that are often used for cell seeding scaffolds generally have low mechanical strength and low electrical conductivity; thus, it has been difficult to apply them to tissues such as heart and nerve. In this study, we prepared oriented poly(vinyl alcohol) (PVA) nanofiber mats blended with various CNT concentrations (up to 10 wt %) by electrospinning using the parallel plate electrodes as collectors with applied voltage. The morphology, mechanical properties, and electrical properties of the prepared oriented nanofiber mats were measured by using various techniques such as scanning electron microscopy (SEM). The tensile strength of the oriented nanofiber mats in the applied voltage direction increased from 2.5 to 9.7 MPa with CNT concentration. Furthermore, the electrical conductivity of the oriented nanofiber mats in the applied voltage direction increased from 0.67 × 10-7 to 4.3 × 10-7 S·m-1. Also, the mechanical strength and electrical conductivity of the oriented nanofiber mats in the applied voltage direction were 3-4 and 2-3 times higher than those in the perpendicular direction, respectively.

Electrodeposition of gold thin films with controlled morphologies and their applications in electrocatalysis and SERS.

PubMed

Elias, Jamil; Gizowska, Magdalena; Brodard, Pierre; Widmer, Roland; Dehazan, Yoram; Graule, Thomas; Michler, Johann; Philippe, Laetitia

2012-06-29

Here, an easy and effective electrochemical route towards the synthesis of gold thin films with well-controlled roughness, morphology and crystallographic orientation is reported. To control these different factors, the applied potential during deposition played a major role. A tentative nucleation and growth mechanism is demonstrated by means of electrochemical characterizations and a formation mechanism is proposed. Interestingly, the differences in geometry and orientation of the different gold deposits have shown a clear correlation with the electrocatalytical activity in the case of oxygen sensing. In addition, not only the electrocatalytical activity but also the surface-enhanced Raman scattering of the gold deposits have been found to depend both on the roughness and on the size of the surface nanostructures, allowing a fine tuning by controlling these two parameters during deposition.

Electrodeposition of gold thin films with controlled morphologies and their applications in electrocatalysis and SERS

NASA Astrophysics Data System (ADS)

Elias, Jamil; Gizowska, Magdalena; Brodard, Pierre; Widmer, Roland; deHazan, Yoram; Graule, Thomas; Michler, Johann; Philippe, Laetitia

2012-06-01

Here, an easy and effective electrochemical route towards the synthesis of gold thin films with well-controlled roughness, morphology and crystallographic orientation is reported. To control these different factors, the applied potential during deposition played a major role. A tentative nucleation and growth mechanism is demonstrated by means of electrochemical characterizations and a formation mechanism is proposed. Interestingly, the differences in geometry and orientation of the different gold deposits have shown a clear correlation with the electrocatalytical activity in the case of oxygen sensing. In addition, not only the electrocatalytical activity but also the surface-enhanced Raman scattering of the gold deposits have been found to depend both on the roughness and on the size of the surface nanostructures, allowing a fine tuning by controlling these two parameters during deposition.

Plasmonic complex fluids of nematiclike and helicoidal self-assemblies of gold nanorods with a negative order parameter.

PubMed

Liu, Qingkun; Senyuk, Bohdan; Tang, Jianwei; Lee, Taewoo; Qian, Jun; He, Sailing; Smalyukh, Ivan I

2012-08-24

We describe a soft matter system of self-organized oblate micelles and plasmonic gold nanorods that exhibit a negative orientational order parameter. Because of anisotropic surface anchoring interactions, colloidal gold nanorods tend to align perpendicular to the director describing the average orientation of normals to the discoidal micelles. Helicoidal structures of highly concentrated nanorods with a negative order parameter are realized by adding a chiral additive and are further controlled by means of confinement and mechanical stress. Polarization-sensitive absorption, scattering, and two-photon luminescence are used to characterize orientations and spatial distributions of nanorods. Self-alignment and effective-medium optical properties of these hybrid inorganic-organic complex fluids match predictions of a simple model based on anisotropic surface anchoring interactions of nanorods with the structured host medium.

Geometry and kinematics of accretionary wedge faults inherited from the structure and rheology of the incoming sedimentary section; insights from 3D seismic reflection data

NASA Astrophysics Data System (ADS)

Bell, Rebecca; Orme, Haydn; Lenette, Kathryn; Jackson, Christopher; Fitch, Peter; Phillips, Thomas; Moore, Gregory

2017-04-01

Intra-wedge thrust faults represent important conduits for fluid flow in accretionary prisms, modulating pore fluid pressure, effective stress and, ultimately, the seismic hazard potential of convergent plate boundaries. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust networks in accretionary prisms, largely due to a lack of 3D seismic reflection data providing high-resolution, 3D images. To address this we here present observations from two subduction zones, the Nankai and Lesser Antilles margins, where 3D seismic and borehole data allow us to constrain the geometry and kinematics of intra-wedge fault networks and to thus shed light on the mechanisms responsible for their structural style variability. At the Muroto transect, Nankai margin we find that the style of protothrust zone deformation varies markedly along-strike over distances of only a few km. Using structural restoration and quantitative fault analysis, we reveal that in the northern part of the study area deformation occurred by buckle folding followed by faulting. Further south, intra-wedge faults nucleate above the décollement and propagate radially with no folding, resulting in variable connectivity between faults and the décollement. The seismic facies character of sediments immediately above the décollement varies along strike, with borehole data revealing that, in the north, where buckle folding dominates un-cemented Lower Shikoku Basin sediments overlie the décollement. In contrast, further south, Opal CT-cemented, and thus rigid Upper Shikoku Basin sediments overlie the décollement. We suggest these along-strike variations in diagenesis and thus rheology control the observed structural style variability. Near Barbados, at the Lesser Antilles margin, rough subducting plate relief is blanketed by up to 700 m of sediment. 3D seismic data reveal that basement relief is defined by linear normal fault blocks and volcanic ridges, and sub-circular seamounts. The youngest, most basinward thrusts in the wedge strike NW-SE; however, 17 km landward, towards the wedge core, they strike NE-SW. The orientation of the more landward faults correlates with the trend of linear basement relief, whereas thrust fault orientations close to the deformation front are perpendicular to the convergence direction. We notice that oceanic crust that has been subducted is characterised by NE-SW striking, now-inverted normal faults, with some faults extending up through the entire sedimentary section. We suggest that the NE-SW orientation of thrust faults has been inherited from linear basement ridges. In contrast, basement currently subducting beneath the deformation front is dominated by seamounts and is devoid of more linear features. Here, there are no pre-existing normal faults available for reactivation and thrust faults develop perpendicular to the convergence direction. We show that the incoming plate properties have a profound effect on the geometry of accretionary wedges; it would be difficult to elucidate this without 3D seismic data. Our insights provide new hypotheses that can be tested with numerical and laboratory models.

Water liquid-vapor interface subjected to various electric fields: A molecular dynamics study.

PubMed

Nikzad, Mohammadreza; Azimian, Ahmad Reza; Rezaei, Majid; Nikzad, Safoora

2017-11-28

Investigation of the effects of E-fields on the liquid-vapor interface is essential for the study of floating water bridge and wetting phenomena. The present study employs the molecular dynamics method to investigate the effects of parallel and perpendicular E-fields on the water liquid-vapor interface. For this purpose, density distribution, number of hydrogen bonds, molecular orientation, and surface tension are examined to gain a better understanding of the interface structure. Results indicate enhancements in parallel E-field decrease the interface width and number of hydrogen bonds, while the opposite holds true in the case of perpendicular E-fields. Moreover, perpendicular fields disturb the water structure at the interface. Given that water molecules tend to be parallel to the interface plane, it is observed that perpendicular E-fields fail to realign water molecules in the field direction while the parallel ones easily do so. It is also shown that surface tension rises with increasing strength of parallel E-fields, while it reduces in the case of perpendicular E-fields. Enhancement of surface tension in the parallel field direction demonstrates how the floating water bridge forms between the beakers. Finally, it is found that application of external E-fields to the liquid-vapor interface does not lead to uniform changes in surface tension and that the liquid-vapor interfacial tension term in Young's equation should be calculated near the triple-line of the droplet. This is attributed to the multi-directional nature of the droplet surface, indicating that no constant value can be assigned to a droplet's surface tension in the presence of large electric fields.

Field induced heliconical structure of cholesteric liquid crystal

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

Lavrentovich, Oleg D.; Shiyanovsii, Sergij V.; Xiang, Jie

A diffraction grating comprises a liquid crystal (LC) cell configured to apply an electric field through a cholesteric LC material that induces the cholesteric LC material into a heliconical state with an oblique helicoid director. The applied electric field produces diffracted light from the cholesteric LC material within the visible, infrared or ultraviolet. The axis of the heliconical state is in the plane of the liquid crystal cell or perpendicular to the plane, depending on the application. A color tuning device operates with a similar heliconical state liquid crystal material but with the heliconical director axis oriented perpendicular to themore » plane of the cell. A power generator varies the strength of the applied electric field to adjust the wavelength of light reflected from the cholesteric liquid crystal material within the visible, infrared or ultraviolet.« less

YCo5±x thin films with perpendicular anisotropy grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Sharma, S.; Hildebrandt, E.; Sharath, S. U.; Radulov, I.; Alff, L.

2017-06-01

The synthesis conditions of buffer-free (00l) oriented YCo5 and Y2Co17 thin films onto Al2O3 (0001) substrates have been explored by molecular beam epitaxy (MBE). The manipulation of the ratio of individual atomic beams of Yttrium, Y and Cobalt, Co, as well as growth rate variations allows establishing a thin film phase diagram. Highly textured YCo5±x thin films were stabilized with saturation magnetization of 517 emu/cm3 (0.517 MA/m), coercivity of 4 kOe (0.4 T), and anisotropy constant, K1, equal to 5.34 ×106 erg/cm3 (0.53 MJ/m3). These magnetic parameters and the perpendicular anisotropy obtained without additional underlayers make the material system interesting for application in magnetic recording devices.

Spin wave propagation in perpendicularly magnetized nm-thick yttrium iron garnet films

NASA Astrophysics Data System (ADS)

Chen, Jilei; Heimbach, Florian; Liu, Tao; Yu, Haiming; Liu, Chuanpu; Chang, Houchen; Stückler, Tobias; Hu, Junfeng; Zeng, Lang; Zhang, Youguang; Liao, Zhimin; Yu, Dapeng; Zhao, Weisheng; Wu, Mingzhong

2018-03-01

Magnonics offers a new way for information transport that uses spin waves (SWs) and is free of charge currents. Unlike Damon-Eshbach SWs, the magneto-static forward volume SWs offer the reciprocity configuration suitable for SW logic devices with low power consumption. Here, we study forward volume SW propagation in yttrium iron garnet (YIG) thin films with an ultra-low damping constant α = 8 ×10-5 . We design different integrated microwave antenna with different k-vector excitation distributions on YIG thin films. Using a vector network analyzer, we measured SW transmission with the films magnetized in perpendicular orientation. Based on the experimental results, we extract the group velocity as well as the dispersion relation of SWs and directly compare the power efficiency of SW propagation in YIG using coplanar waveguide and micro stripline for SW excitation and detection.

Detection of alterations in human sperm using magnetic orientation techniques

NASA Astrophysics Data System (ADS)

Sakhnini, Lama; Dairi, Maheen; Manaa, Hacene

2007-09-01

In this study we report on magnetic orientation of human sperms. Samples were taken from 17 donors. Normal human sperms became oriented with their long axis perpendicular to the magnetic field ( 1 Tesla maximum). Total orientation was achieved with magnetic field at about one Tesla, while for abnormal sperms the magnetic behavior was different. The dependence of the measured degree of orientation on the intensity of the magnetic field was in good agreement with the theoretical equation for the magnetic orientation of diamagnetic substances. As a result for a numerical analysis based on the equation, the anisotropic diamagnetic susceptibility of normal sperm was found to be ▵ χ= 8×10 -20 J/T2. The degree of orientation was influenced by the alterations in the shape of the head, body or the tail. It has been suggested that the DNA in the sperm head retain the strong magnetic anisotropy to counter balance the magnetic anisotropy retained by flagellum microtubules. Recent studies demonstrated a well-defined nuclear architecture in human sperm nucleus, where the head morphology has significant correlation with sperm chromatin structure assay SCSA. Then as the methods to evaluate SCSA can be difficult and expensive our simple magnetic orientation technique can be an alternative to diagnose alteration in DNA.

Cleavage in conical sand dollar eggs.

PubMed

Rappaport, R; Rappaport, B N

1994-07-01

Previous experiments have shown that the mitotic apparatus and the surface can interact and produce functional furrows in various unusual geometrical circumstances. The consistent development of the furrow in the plane equidistant from the aster centers has led to conjecture about the need for a special structural configuration of the subsurface in the future cleavage plane. In most experiments involving altered cell geometry, the relation between each aster and nearby surface was symmetrical, and the effect of that symmetry upon the position and orientation of the cleavage mechanism in the cortex has not been systematically analyzed. The normal symmetry of sand dollar eggs can be changed by reshaping them into cones. When the cone and mitotic axes are parallel, the aster center closer to the vertex is also closer to the nearby surface, and the cleavage plane develops on the vertex side of the midpoint between the asters. A mitotic apparatus oriented perpendicular to the cone axis produces in the base of the cone a normal unilateral furrow that advances toward the vertex, and a second contractile band that isolates the vertex region. This event only occurs when the surface is conical and the mitotic apparatus is perpendicular to the cone axis. Furrow formation is not restricted to the plane of the metaphase plate or the midpoint between the aster centers. The orientation of mitotic apparatus-produced contractile bands is not limited to the circumstances in normal cytokinesis, but may vary according to surface contour. These results confirm predictions of the Harris and Gewalt model of contractile ring induction.

The utilization of satellite data and dynamics in understanding and predicting global weather phenomena

NASA Technical Reports Server (NTRS)

Shirer, H. N. (Editor); Dutton, J. A. (Editor)

1985-01-01

A two layer spectral quasi-geostrophic model is used to simulate the effects of topography on the equilibria, the stability, and the long term evaluation of incipient unstable waves. The flow is forced by latitudinally dependent radiational heating. The nature of the form drag instability of high index equilibria is investigated. The proximity of the equilibrium shear to a resonant value is essential for the instability, provided the equilibrium occurs at a slightly stronger shear than resonance. The properties of the steady Hadley and Rossby required for a thermally forced rotating fluid on a sphere are further explained. An objective parameterization technique is developed for general nonlinear hydrodynamical systems. The typical structure is one in which the rates of change of the dependent variables depend on homogeneous quadratic and linear forms, as well as on inhomogeneous forcing terms. Also documented is a steady, axisymmetric model of the general circulation developed as a basis for climate stability studies. The model includes the effects of heating, rotation, and internal friction, but neglects topography. Included is further research on cloud street phenomena. Orientation angles and horizontal wavelengths of boundary layer rolls and cloud streets are determined from an analysis of a truncated spectral model of three dimensional shallow moist Boussinesq convection in a shearing environment is further explained. Relatively broadly spaced roll clouds have orientations for which the Fourier component of the roll perpendicular shear is nearly zero, but the second corresponds to narrowly spaced rolls having orientations for which the Fourier coefficients of both the perpendicular and the parallel components of the shear are nearly equal.

Topographically driven groundwater flow and the San Andreas heat flow paradox revisited

USGS Publications Warehouse

Saffer, D.M.; Bekins, B.A.; Hickman, S.

2003-01-01

Evidence for a weak San Andreas Fault includes (1) borehole heat flow measurements that show no evidence for a frictionally generated heat flow anomaly and (2) the inferred orientation of ??1 nearly perpendicular to the fault trace. Interpretations of the stress orientation data remain controversial, at least in close proximity to the fault, leading some researchers to hypothesize that the San Andreas Fault is, in fact, strong and that its thermal signature may be removed or redistributed by topographically driven groundwater flow in areas of rugged topography, such as typify the San Andreas Fault system. To evaluate this scenario, we use a steady state, two-dimensional model of coupled heat and fluid flow within cross sections oriented perpendicular to the fault and to the primary regional topography. Our results show that existing heat flow data near Parkfield, California, do not readily discriminate between the expected thermal signature of a strong fault and that of a weak fault. In contrast, for a wide range of groundwater flow scenarios in the Mojave Desert, models that include frictional heat generation along a strong fault are inconsistent with existing heat flow data, suggesting that the San Andreas Fault at this location is indeed weak. In both areas, comparison of modeling results and heat flow data suggest that advective redistribution of heat is minimal. The robust results for the Mojave region demonstrate that topographically driven groundwater flow, at least in two dimensions, is inadequate to obscure the frictionally generated heat flow anomaly from a strong fault. However, our results do not preclude the possibility of transient advective heat transport associated with earthquakes.

Adjustable Powder Injector For Vacuum Plasma Sprayer

NASA Technical Reports Server (NTRS)

Burns, D. H.; Woodford, W. H.; Mckechnie, T. N.; Mcferrin, D. C.; Davis, W. M.; Beason, G. P., Jr.

1993-01-01

Attachment for plasma spray gun provides four degrees of freedom for adjustment of position and orientation at which powder injected externally into plasma flame. Manipulator provides for adjustment of pitch angle of injection tube: set to inject powder at any angle ranging from perpendicular to parallel to cylindrical axis. Scribed lines on extension bar and manipulator indicate pitch angle of extension tube. Collar changed to adapt injector to different gun.

Method of making porous conductive supports for electrodes. [by electroforming and stacking nickel foils

NASA Technical Reports Server (NTRS)

Schaer, G. R. (Inventor)

1973-01-01

Porous conductive supports for electrochemical cell electrodes are made by electroforming thin corrugated nickel foil, and by stacking pieces of the corrugated foil alternatively with pieces of thin flat nickel foil. Corrugations in successive corrugated pieces are oriented at different angles. Adjacent pieces of foil are bonded by heating in a hydrogen atmosphere and then cutting the stack in planes perpendicular to the foils.

High average power pockels cell

DOEpatents

Daly, Thomas P.

1991-01-01

A high average power pockels cell is disclosed which reduces the effect of thermally induced strains in high average power laser technology. The pockels cell includes an elongated, substantially rectangular crystalline structure formed from a KDP-type material to eliminate shear strains. The X- and Y-axes are oriented substantially perpendicular to the edges of the crystal cross-section and to the C-axis direction of propagation to eliminate shear strains.

Direct electronic communication at bio-interfaces assisted by layered-metal-hydroxide slab arrays with controlled nano-micro structures.

PubMed

An, Zhe; He, Jing

2011-10-28

The electronic transfer (eT) at bio-interfaces has been achieved by orientating 2D inorganic slabs in a regular arrangement with the slab ab-planes vertical to the electrode substrate. The eT rate is effectively promoted by tuning the nano-micro scale structures of perpendicular LDH arrays. This journal is © The Royal Society of Chemistry 2011

On the nature of the NAA diffusion attenuated MR signal in the central nervous system.

PubMed

Kroenke, Christopher D; Ackerman, Joseph J H; Yablonskiy, Dmitriy A

2004-11-01

In the brain, on a macroscopic scale, diffusion of the intraneuronal constituent N-acetyl-L-aspartate (NAA) appears to be isotropic. In contrast, on a microscopic scale, NAA diffusion is likely highly anisotropic, with displacements perpendicular to neuronal fibers being markedly hindered, and parallel displacements less so. In this report we first substantiate that local anisotropy influences NAA diffusion in vivo by observing differing diffusivities parallel and perpendicular to human corpus callosum axonal fibers. We then extend our measurements to large voxels within rat brains. As expected, the macroscopic apparent diffusion coefficient (ADC) of NAA is practically isotropic due to averaging of the numerous and diverse fiber orientations. We demonstrate that the substantially non-monoexponential diffusion-mediated MR signal decay vs. b value can be quantitatively explained by a theoretical model of NAA confined to an ensemble of differently oriented neuronal fibers. On the microscopic scale, NAA diffusion is found to be strongly anisotropic, with displacements occurring almost exclusively parallel to the local fiber axis. This parallel diffusivity, ADCparallel, is 0.36 +/- 0.01 microm2/ms, and ADCperpendicular is essentially zero. From ADCparallel the apparent viscosity of the neuron cytoplasm is estimated to be twice as large as that of a temperature-matched dilute aqueous solution. (c) 2004 Wiley-Liss, Inc.

Thin film metallic sensors in an alternating magnetic field for magnetic nanoparticle hyperthermia cancer therapy

NASA Astrophysics Data System (ADS)

Hussein, Z. A.; Boekelheide, Z.

In magnetic nanoparticle hyperthermia in an alternating magnetic field for cancer therapy, it is important to monitor the temperature in situ. This can be done optically or electrically, but electronic measurements can be problematic because conducting parts heat up in a changing magnetic field. Microfabricated thin film sensors may be advantageous because eddy current heating is a function of size, and are promising for further miniaturization of sensors and fabrication of arrays of sensors. Thin films could also be used for in situ magnetic field sensors or for strain sensors. For a proof of concept, we fabricated a metallic thin film resistive thermometer by photolithographically patterning a 500Å Au/100Å Cr thin film on a glass substrate. Measurements were taken in a solenoidal coil supplying 0.04 T (rms) at 235 kHz with the sensor parallel and perpendicular to the magnetic field. In the parallel orientation, the resistive thermometer mirrored the background heating from the coil, while in the perpendicular orientation self-heating was observed due to eddy current heating of the conducting elements by Faraday's law. This suggests that metallic thin film sensors can be used in an alternating magnetic field, parallel to the field, with no significant self-heating.

Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI-LINAC systems.

PubMed

Gargett, Maegan; Oborn, Brad; Metcalfe, Peter; Rosenfeld, Anatoly

2015-02-01

MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named "magic plate," for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. geant4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-line and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm(3)) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm(2) area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm(2) photon field size. The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI-linear accelerator systems. In the in-line orientation, the silicon dose is directly proportional to the water dose. In the perpendicular orientation, there is a shift in dose response relative to water in the highest dose gradient regions, at the edge of jaw-defined and single-segment MLC fields. The trend was not observed in-field for an IMRT beam. The array is expected to be a valuable tool in MRIgRT dosimetry.

Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI–LINAC systems

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

Gargett, Maegan, E-mail: mg406@uowmail.edu.au; Rosenfeld, Anatoly; Oborn, Brad

2015-02-15

Purpose: MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named “magic plate,” for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. Methods: GEANT4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-linemore » and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm{sup 3}) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm{sup 2} area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm{sup 2} photon field size. Results: The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. Conclusions: A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI–linear accelerator systems. In the in-line orientation, the silicon dose is directly proportional to the water dose. In the perpendicular orientation, there is a shift in dose response relative to water in the highest dose gradient regions, at the edge of jaw-defined and single-segment MLC fields. The trend was not observed in-field for an IMRT beam. The array is expected to be a valuable tool in MRIgRT dosimetry.« less

Heating-freezing effects on the orientation of kaolin clay particles

DOE PAGES

Jaradat, Karam A.; Darbari, Zubin; Elbakhshwan, Mohamed; ...

2017-09-29

The effects of temperature changes on the particle orientation of a consolidated kaolin are studied using XRD experiments. Here, two sets of equipment were utilized in this study: a benchtop equipment, and a synchrotron beamline at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. The kaolin specimens tested in the benchtop XRD were subjected to elevated and freezing temperatures ex-situ, while those used for the NSLS-II experiment were exposed to the temperature changes in-situ. The temperatures considered in this study range from freezing (-10 °C) to elevated temperature below boiling (90 °C). The thermally-induced reorientation of claymore » mineral particles is highly dependent on the relative orientation of the clay mineral particles with respect to the applied thermal gradient. For example, kaolin samples with kaolinite particles oriented perpendicular to the thermal gradient, and to the expected thermally-induced pore water flow, experience much higher particles reorientations compared to samples with particles initially oriented parallel to the thermal gradient. Lastly, freezing kaolin preserved its microstructure as ice crystals form.« less

Heating-freezing effects on the orientation of kaolin clay particles

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

Jaradat, Karam A.; Darbari, Zubin; Elbakhshwan, Mohamed

The effects of temperature changes on the particle orientation of a consolidated kaolin are studied using XRD experiments. Here, two sets of equipment were utilized in this study: a benchtop equipment, and a synchrotron beamline at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. The kaolin specimens tested in the benchtop XRD were subjected to elevated and freezing temperatures ex-situ, while those used for the NSLS-II experiment were exposed to the temperature changes in-situ. The temperatures considered in this study range from freezing (-10 °C) to elevated temperature below boiling (90 °C). The thermally-induced reorientation of claymore » mineral particles is highly dependent on the relative orientation of the clay mineral particles with respect to the applied thermal gradient. For example, kaolin samples with kaolinite particles oriented perpendicular to the thermal gradient, and to the expected thermally-induced pore water flow, experience much higher particles reorientations compared to samples with particles initially oriented parallel to the thermal gradient. Lastly, freezing kaolin preserved its microstructure as ice crystals form.« less

Geometrical characterization of perlite-metal syntactic foam

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

Borovinšek, Matej, E-mail: matej.borovinsek@um.si

This paper introduces an improved method for the detailed geometrical characterization of perlite-metal syntactic foam. This novel metallic foam is created by infiltrating a packed bed of expanded perlite particles with liquid aluminium alloy. The geometry of the solidified metal is thus defined by the perlite particle shape, size and morphology. The method is based on a segmented micro-computed tomography data and allows for automated determination of the distributions of pore size, sphericity, orientation and location. The pore (i.e. particle) size distribution and pore orientation is determined by a multi-criteria k-nearest neighbour algorithm for pore identification. The results indicate amore » weak density gradient parallel to the casting direction and a slight preference of particle orientation perpendicular to the casting direction. - Highlights: •A new method for identification of pores in porous materials was developed. •It was applied on perlite-metal syntactic foam samples. •A porosity decrease in the axial direction of the samples was determined. •Pore shape analysis showed a high percentage of spherical pores. •Orientation analysis showed that more pores are oriented in the radial direction.« less

Orienting Periodic Organic-Inorganic Nanoscale Domains Through One-Step Electrodeposition

PubMed Central

Herman, David J.; Goldberger, Joshua E.; Chao, Stephen; Martin, Daniel T.; Stupp, Samuel I

2011-01-01

One of the challenges in the synthesis of hybrid materials with nanoscale structure is to precisely control morphology across length scales. Using a one-step electrodeposition process on indium tin oxide (ITO) substrates followed by annealing, we report here the preparation of materials with preferentially oriented lamellar domains of electron donor surfactants and the semiconductor ZnO. We found that either increasing the concentration of surfactant or the water to dimethyl sulfoxide ratio of solutions used resulted in the suppression of bloom-like morphologies and enhanced the density of periodic domains on ITO substrates. Furthermore, by modifying the surface of the ITO substrate with the conductive polymer blend poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), we were able to alter the orientation of these electrodeposited lamellar domains to be perpendicular to the substrate. The long-range orientation achieved was characterized by 2D grazing incidence small angle X-ray scattering. This high degree of orientation in electronically active hybrids with alternating nanoscale p-type and n-type domains is of potential interest in photovoltaics or thermoelectric materials. PMID:21142087

Uniaxial alignment of triisopropylsilylethynyl pentacene via zone-casting technique.

PubMed

Su, Yajun; Gao, Xiang; Liu, Jiangang; Xing, Rubo; Han, Yanchun

2013-09-14

Uniaxially aligned triisopropylsilylethynyl pentacene (TIPS-pentacene) crystals over a large area were fabricated using zone-casting technique. The array of TIPS-pentacene displayed a high orientation degree with a dichroic ratio (DR) of 0.80. The crystals were arranged with c axis perpendicular to the substrate and the long axis of the ribbon corresponded to the a axis of TIPS-pentacene. The properties of the solutions and the processing parameters were shown to influence the formation of the oriented TIPS-pentacene crystalline array. Solvent with a low boiling point (such as chloroform) favoured the orientation of the ribbon-like crystals. The concentration of the solution should be appropriate, ensuring the crystallization velocity of TIPS-pentacene matching with the receding of the meniscus. Besides, we proved that the casting speed should be large enough to induce a sufficient concentration gradient. The orientation mechanism of TIPS-pentacene was attributed to a synergy of the ordered nuclei and a match between the crystallization velocity and the casting speed. Field effect transistors (FETs) based on the oriented TIPS-pentacene crystalline array showed a mobility of 0.67 cm(2) V(-1) s(-1).

Controlling domain orientation of liquid crystalline block copolymer in thin films through tuning mesogenic chemical structures

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

Xie, He-Lou; Li, Xiao; Ren, Jiaxing

Controlling the macroscopic orientation of nanoscale periodic structures of amphiphilic liquid crystalline block copolymers (LC BCPs) is important to a variety of technical applications (e.g., lithium conducting polymer electrolytes). To study LC BCP domain orientation, a series of LC BCPs containing a poly(ethylene oxide) (PEO) block as a conventional hydrophilic coil block and LC blocks containing azobenzene mesogens is designed and synthesized. LC ordering in thin films of the BCP leads to the formation of highly ordered, microphase-separated nanostructures, with hexagonally arranged PEO cylinders. Substitution on the tail of the azobenzene mesogen is shown to control the orientation of themore » PEO cylinders. When the substitution on the mesogenic tails is an alkyl chain, the PEO cylinders have a perpendicular orientation to the substrate surface, provided the thin film is above a critical thickness value. In contrast, when the substitution on the mesogenic tails has an ether group the PEO cylinders assemble parallel to the substrate surface regardless of the film thickness value.« less

The Effect of Prism Orientation in the Indentation Testing of Human Molar Enamel

PubMed Central

Braly, A.; Darnell, L.A.; Mann, A.B.; Teaford, M.F.; Weihs, T.P.

2007-01-01

Recent nanoindentation studies have demonstrated that the hardness and Young's modulus of human molar enamel decreases by more than 50% on moving from the occlusal surface to the dentin-enamel junction on cross-sectional samples. Possible sources of these variations are changes in local chemistry, microstructure, and prism orientation. This study investigates the latter source by performing nanoindentation tests at two different orientations relative to the hydroxyapatite prisms: parallel and perpendicular. A single sample volume was tested in order to maintain a constant chemistry and microstructure. The resulting data show very small differences between the two orientations for both hardness and Young's modulus. The 1.5 to 3.0% difference is significantly less than the standard deviations found within the data set. Thus, the variations in hardness and Young's modulus on cross-sectional samples of human molar are attributed to changes in local chemistry (varying levels of mineralization, organic matter, and water content) and changes in microstructure (varying volume fractions of inorganic crystals and organic matrix). The impact of prism orientation on mechanical properties measured by nanoindentation appears to be minimal. PMID:17449008

Growth and characterization of MnGa thin films with perpendicular magnetic anisotropy on BiSb topological insulator

NASA Astrophysics Data System (ADS)

Duy Khang, Nguyen Huynh; Ueda, Yugo; Yao, Kenichiro; Hai, Pham Nam

2017-10-01

We report on the crystal growth as well as the structural and magnetic properties of Bi0.8Sb0.2 topological insulator (TI)/MnxGa1-x bi-layers grown on GaAs(111)A substrates by molecular beam epitaxy. By optimizing the growth conditions and Mn composition, we were able to grow MnxGa1-x thin films on Bi0.8Sb0.2 with the crystallographic orientation of Bi0.8Sb0.2(001)[1 1 ¯ 0]//MnGa (001)[100]. Using magnetic circular dichroism (MCD) spectroscopy, we detected both the L10 phase ( x < 0.6 ) and the D022 phase ( x > 0.6 ) of MnxGa1-x. For 0.50 ≤ x ≤ 0.55 , we obtained ferromagnetic L10-MnGa thin films with clear perpendicular magnetic anisotropy, which were confirmed by MCD hysteresis, anomalous Hall effect as well as superconducting quantum interference device measurements. Our results show that the BiSb/MnxGa1-x bi-layer system is promising for perpendicular magnetization switching using the giant spin Hall effect in TIs.

Electrical spin injection into GaAs based light emitting diodes using perpendicular magnetic tunnel junction-type spin injector

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

Tao, B. S.; Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190; Barate, P.

Remanent electrical spin injection into an InGaAs/GaAs based quantum well light emitting diode is realized by using a perpendicularly magnetized MgO/CoFeB/Ta/CoFeB/MgO spin injector. We demonstrate that the Ta interlayer plays an important role to establish the perpendicular magnetic anisotropy and the thickness of Ta interlayer determines the type of exchange coupling between the two adjacent CoFeB layers. They are ferromagnetically or antiferromagnetically coupled for a Ta thickness of 0.5 nm or 0.75 nm, respectively. A circular polarized electroluminescence (P{sub c}) of about 10% is obtained at low temperature and at zero magnetic field. The direction of the electrically injected spins is determinedmore » only by the orientation of the magnetization of the bottom CoFeB layer which is adjacent to the MgO/GaAs interface. This work proves the critical role of the bottom CoFeB/MgO interface on the spin-injection and paves the way for the electrical control of spin injection via magnetic tunnel junction-type spin injector.« less

Partial Reflection and Trapping of a Fast-mode Wave in Solar Coronal Arcade Loops

NASA Astrophysics Data System (ADS)

Kumar, Pankaj; Innes, D. E.

2015-04-01

We report on the first direct observation of a fast-mode wave propagating along and perpendicular to cool (171 Å) arcade loops observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). The wave was associated with an impulsive/compact flare near the edge of a sunspot. The EUV wavefront expanded radially outward from the flare center and decelerated in the corona from 1060 to 760 km s-1 within ˜3-4 minutes. Part of the EUV wave propagated along a large-scale arcade of cool loops and was partially reflected back to the flare site. The phase speed of the wave was about 1450 km s-1, which is interpreted as a fast-mode wave. A second overlying loop arcade, orientated perpendicular to the cool arcade, is heated and becomes visible in the AIA hot channels. These hot loops sway in time with the EUV wave, as it propagated to and fro along the lower loop arcade. We suggest that an impulsive energy release at one of the footpoints of the arcade loops causes the onset of an EUV shock wave that propagates along and perpendicular to the magnetic field.

Research of influence of the underlayer material on the growth rate of carbon nanotube arrays for manufacturing non-volatile memory elements with high speed

NASA Astrophysics Data System (ADS)

Klimin, V. S.; Il'ina, M. V.; Il'in, O. I.; Rudyk, N. N.; Ageev, O. A.

2017-11-01

This experimental work is devoted to the regimes of obtaining arrays of carbon nanotubes. Arrays of perpendicular nanotubes perpendicular to the surface were obtained by the method of Plasma-enhanced chemical vapor deposition. In this paper, geometric and electronic parameters of carbon nanotubes were investigated depending on the material of the sublayer. The rates of growth of carbon nanotubes on various structures were also determined. In the experiments for growth, structures such as Ni-Al-Si, Ni-V-Si, Ni-Ti-Si, Ni-Cr-Si were used. The growth rates for the intensive section were for the Ni-Cr-Si structure, the growth rate is about 1 μm / min, for the Ni-V-Si structure it is 0.55 μm / min. The growth rates for the saturation region for the Ni-Cr-Si structure, the growth rate is about 0.2 μm / min, for the Ni-V-Si structure 0.16 μm / min. The results obtained in this paper can be used to optimize the growth regimes perpendicularly oriented to the substrate carbon nanotubes, which are used as various elements in modern nanoelectronics.

Probable errors in width distributions of sea ice leads measured along a transect

NASA Technical Reports Server (NTRS)

Key, J.; Peckham, S.

1991-01-01

The degree of error expected in the measurement of widths of sea ice leads along a single transect are examined in a probabilistic sense under assumed orientation and width distributions, where both isotropic and anisotropic lead orientations are examined. Methods are developed for estimating the distribution of 'actual' widths (measured perpendicular to the local lead orientation) knowing the 'apparent' width distribution (measured along the transect), and vice versa. The distribution of errors, defined as the difference between the actual and apparent lead width, can be estimated from the two width distributions, and all moments of this distribution can be determined. The problem is illustrated with Landsat imagery and the procedure is applied to a submarine sonar transect. Results are determined for a range of geometries, and indicate the importance of orientation information if data sampled along a transect are to be used for the description of lead geometries. While the application here is to sea ice leads, the methodology can be applied to measurements of any linear feature.

Effects of Shear on the Smectic A Phase of Thermotropic Liquid Crystals

NASA Astrophysics Data System (ADS)

Panizza, Pascal; Archambault, Pascal; Roux, Didier

1995-02-01

The rheological behaviour of the smectic A phase of the thermotropic liquid crystal 4-cyano-4'-octylbiphenyl (8CB) is examined. X-ray scattering studies under shear flow were performed to probe changes of structures. We found that in a certain range of temperatures two states of orientation of lamellae exist. These two steady states of orientation are separated by a first order dynamic transition that becomes continuous at T_c (a temperature different from that of the smectic/nematic transition). At low shear rates, the smectic A phase is non-Newtonian: its viscosity η varies as (T_c-T)^{1/2}.dot{γ}^{-1/2} (where dot{γ} is the shear rate and T the temperature). In this regime, the structure of the system is compatible with multilamellar cylinders oriented along the flow direction. At high shear rates, the system becomes Newtonian, its layers are then oriented perpendicular to the shearing plates (as already noticed by Safinya et al. [1]).

Far field emission profile of pure wurtzite InP nanowires

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

Bulgarini, Gabriele, E-mail: g.bulgarini@tudelft.nl; Reimer, Michael E.; Zwiller, Val

2014-11-10

We report on the far field emission profile of pure wurtzite InP nanowires in comparison to InP nanowires with predominantly zincblende crystal structure. The emission profile is measured on individual nanowires using Fourier microscopy. The most intense photoluminescence of wurtzite nanowires is collected at small angles with respect to the nanowire growth axis. In contrast, zincblende nanowires present a minimum of the collected light intensity in the direction of the nanowire growth. Results are explained by the orientation of electric dipoles responsible for the photoluminescence, which is different from wurtzite to zincblende. Wurtzite nanowires have dipoles oriented perpendicular to themore » nanowire growth direction, whereas zincblende nanowires have dipoles oriented along the nanowire axis. This interpretation is confirmed by both numerical simulations and polarization dependent photoluminescence spectroscopy. Knowledge of the dipole orientation in nanostructures is crucial for developing a wide range of photonic devices such as light-emitting diodes, photodetectors, and solar cells.« less

Amino acids at water-vapor interfaces: surface activity and orientational ordering.

PubMed

Vöhringer-Martinez, Esteban; Toro-Labbé, Alejandro

2010-10-14

The surface activity and orientational ordering of amino acids at water-vapor interfaces were studied with molecular dynamics simulations in combination with thermodynamic integration and umbrella sampling. Asparagine, representing amino acids with polar side chains, displays no surface activity. Tryptophan, in contrast, with its hydrophobic indole ring as side chain unveils a free energy minimum at the water-vapor interface, which lies 6 kJ/mol under the hydration free energy. To study the orientational ordering of tryptophan along the interface, the order parameter was calculated. At the free energy minimum and at the Gibbs dividing surface, the order parameter reveals a parallel alignment of the indole ring with the water surface exposing the π-system to electrophiles in the hydrophobic phase and indicating polarization dependent spectroscopy. In the vicinity of this position a perpendicular orientation is obtained. The surface excess, calculated from the potential of mean force along the interface, is in excellent agreement with experimental measurements.

Influence of substrate microcrystallinity on the orientation of laser-induced periodic surface structures

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

Nürnberger, P.; Reinhardt, H.; Kim, H-C.

2015-10-07

The research in this paper deals with the angular dependence of the formation of laser-induced periodic surface structures (LIPSS) by linearly polarized nanosecond laser pulses on polycrystalline austenitic stainless steel. Incident angles ranging from 45° to 70° lead to the generation of superimposed merely perpendicular oriented LIPSS on steel as well as on monocrystalline (100) silicon which was used as a reference material. Additional extraordinary orientations of superimposing LIPSS along with significantly different periodicities are found on polycrystalline steel but not on (100) silicon. Electron backscatter diffraction measurements indicate that the expansion of these LIPSS is limited to the grainmore » size and affected by the crystal orientation of the individual grains. Atomic force microscopy imaging shows that LIPSS fringe heights are in good agreement with the theoretically predicted penetration depths of surface plasmon polaritons into stainless steel. These results indicate that optical anisotropies must be taken into account to fully describe the theory of light-matter interaction leading to LIPSS formation.« less

Conformation of single block copolymer chain in two-dimensional microphase-separated structure studied by scanning near-field optical microscopy.

PubMed

Sekine, Ryojun; Aoki, Hiroyuki; Ito, Shinzaburo

2009-05-21

The localization and orientation of the symmetric diblock copolymer chain in a quasi-two-dimensional microphase-separated structure were studied by scanning near-field optical microscopy (SNOM). In the monolayer of poly(isobutyl methacrylate)-block-poly(octadecyl methacrylate) (PiBMA-b-PODMA), the individual PiBMA subchains were directly observed by SNOM, and the center of mass (CM) and orientational angle relative to the phase interface were examined at the single chain level. It was found that the position of the CM and the orientation of the PiBMA subchain in the lamellar structure were dependent on the curvature of the PiBMA/PODMA interface. As the interface was bent toward the objective chain, the block chain preferred the CM position closer to the domain center, and the conformation was strongly oriented perpendicularly to the domain interface. With increase of the curvature, the steric hindrance among the block chain increases, resulting in the stretched conformation.

Morphology and orientational behavior of silica-coated spindle-type hematite particles in a magnetic field probed by small-angle X-ray scattering.

PubMed

Reufer, Mathias; Dietsch, Hervé; Gasser, Urs; Hirt, Ann; Menzel, Andreas; Schurtenberger, Peter

2010-04-15

Form factor and magnetic properties of silica-coated spindle-type hematite nanoparticles are determined from SAXS measurements with applied magnetic field and magnetometry measurements. The particle size, polydispersity and porosity are determined using a core-shell model for the form factor. The particles are found to align with their long axis perpendicular to the applied field. The orientational order is determined from the SAXS data and compared to the orientational order obtained from magnetometry. The direct access to both, the orientational order of the particles, and the magnetic moments allow one to determine the magnetic properties of the individual spindle-type hematite particles. We study the influence of the silica coating on the magnetic properties and find a fundamentally different behavior of silica-coated particles. The silica coating reduces the effective magnetic moment of the particles. This effect is enhanced with field strength and can be explained by superparamagnetic relaxation in the highly porous particles.

Theory of "laser distillation" of enantiomers: purification of a racemic mixture of randomly oriented dimethylallene in a collisional environment.

PubMed

Gerbasi, David; Shapiro, Moshe; Brumer, Paul

2006-02-21

Enantiomeric control of 1,3 dimethylallene in a collisional environment is examined. Specifically, our previous "laser distillation" scenario wherein three perpendicular linearly polarized light fields are applied to excite a set of vib-rotational eigenstates of a randomly oriented sample is considered. The addition of internal conversion, dissociation, decoherence, and collisional relaxation mimics experimental conditions and molecular decay processes. Of greatest relevance is internal conversion which, in the case of dimethylallene, is followed by molecular dissociation. For various rates of internal conversion, enantiomeric control is maintained in this scenario by a delicate balance between collisional relaxation of excited dimethylallene that enhances control and collisional dephasing, which diminishes control.

Superconducting magnetic coil

DOEpatents

Aized, Dawood; Schwall, Robert E.

1999-06-22

A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

Superconducting magnetic coil

DOEpatents

Aized, Dawood; Schwall, Robert E.

1996-06-11

A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

Cross-polarised and parallel-polarised light: Viewing and photography for examination and documentation of biological materials in medicine and forensics.

PubMed

Hanlon, Katharine L

2018-01-01

Cross-polarisation, with regard to visible light, is a process wherein two polarisers with perpendicular orientation to one another are used on the incident and reflected lights. Under cross-polarised light birefringent structures which are otherwise invisible become apparent. Cross-polarised light eliminates glare and specular highlights, allowing for an unobstructed view of subsurface pathology. Parallel-polarisation occurs when the polarisers are rotated to the same orientation. When cross- or parallel-polarisation is applied to photography, images can be generated which aid in visualisation of surface and subsurface elements. Improved access to equipment and education has the potential to benefit practitioners, researchers, investigators and patients.

Photoelectron Diffraction from Valence States of Oriented Molecules

NASA Astrophysics Data System (ADS)

Krüger, Peter

2018-06-01

The angular distribution of photoelectrons emitted from valence states of oriented molecules is investigated. The principles underlying the angular pattern formation are explained in terms of photoelectron wave interference, caused by initial state delocalization and final state photoelectron scattering. Computational approaches to photoelectron spectroscopy from molecules are briefly reviewed. Here a combination of molecular orbital calculations for the initial state and multiple scattering theory for the photoelectron final state is used and applied to the 3σ and 4σ orbitals of nitrogen and the highest occupied molecular orbital of pentacene. Appreciable perpendicular emission and circular dichroism in angular distributions is found, two effects that cannot be described by the popular plane wave approximation to the photoelectron final state.

The Perils of Electron Microprobe Analysis of Apatite

NASA Astrophysics Data System (ADS)

Henderson, C. E.; Essene, E. J.; Wang, K. L.; Zhang, Y.

2010-12-01

Accurate electron microprobe analysis of apatite is problematic, especially for F and Cl, whose concentrations are essential in calculating a non-analyzable OH component. The issues include beam-induced sample damage and temporal variation of F and Cl X-rays; both effects are mainly dependent on beam current, beam spot size and apatite orientation [1]. To establish a rigorous analytical procedure, several oriented apatite samples, including the well-known Durango and Wilberforce fluorapatites, were analyzed for a large suite of elements, including oxygen. Careful X-ray spectroscopy was performed, including selection of appropriate analytical standards, background measurement positions and comparison of area peak factors. Polarized infrared spectra on oriented apatite samples were also collected for complementary information. The results show that when apatite samples are oriented with the c-axis parallel to the electron beam, there is significant nonlinear variation (an increase or decrease, depending on measurement conditions) of F and Cl X-ray intensities during analyses, and systematically higher-than-expected F apparent concentrations, despite the careful selection of electron beam conditions from a series of X-ray time scans and zero-time count rate extrapolation. On the other hand, when the electron beam is oriented perpendicular to the c-axis, with a ≤ 15 nA beam current and a ≥ 5 µm diameter defocused beam, F and Cl X-ray intensities do not vary or vary slowly and predictably with time, yielding quantitative analysis results for the Durango and Wilberforce apatites (both containing little OH) which are in good agreement with published wet chemical analyses. Furthermore, the OH and CO2 contents inferred for three other analyzed apatite samples are roughly consistent with infrared analyses. For example, for an apatite from Silver Crater Mine in Ontario, significant deficiency in the P site, as well as extra F, was inferred from microprobe analyses. Infrared spectra show a strong band of (CO3)2- for this apatite, which indicates a possible substitution of (CO3)2-(F)- for (PO4)3-. Other techniques to mitigate temporal variation of F and Cl, including alternative metal coatings, concurrent stage movement, and cryogenic sample-cooling were attempted, but did not eliminate the disparity in measured F concentrations between the two sample orientations. Thus, we believe that F measurements on F-rich apatite samples of unknown orientation are immediately suspect and should be regarded as upper limits of true F concentration. X-ray mapping, CL imaging and subsequent quantitative analyses show compositional variations in Na, S, Si, and REE in the Durango and Wilberforce fluorapatite samples used in this study. Problems of electron beam sensitivity, X-ray intensity anisotropy due to sample orientation, and compositional heterogeneity call into question their continued use as routine microanalysis reference materials. Microanalysts are encouraged to use more robust calibration standards, such as Cl-rich or other F-poor apatites for Ca, P, O and Cl, and MgF2 for F measurements. [1] Stormer, J.C., Pierson, M.L, and Tacker, R.C. (1993) Variation of F and Cl X-ray intensity due to anisotropic diffusion in apatite during electron microprobe analysis. Am. Min., 78, 641-648.

Polarized Raman Spectroscopy for Determining the Orientation of di-D-phenylalanine Molecules in a Nanotube.

PubMed

Sereda, Valentin; Ralbovsky, Nicole M; Vasudev, Milana C; Naik, Rajesh R; Lednev, Igor K

2016-09-01

Self-assembly of short peptides into nanostructures has become an important strategy for the bottom-up fabrication of nanomaterials. Significant interest to such peptide-based building blocks is due to the opportunity to control the structure and properties of well-structured nanotubes, nanofibrils, and hydrogels. X-ray crystallography and solution NMR, two major tools of structural biology, have significant limitations when applied to peptide nanotubes because of their non-crystalline structure and large weight. Polarized Raman spectroscopy was utilized for structural characterization of well-aligned D-Diphenylalanine nanotubes. The orientation of selected chemical groups relative to the main axis of the nanotube was determined. Specifically, the C-N bond of CNH 3 + groups is oriented parallel to the nanotube axis, the peptides' carbonyl groups are tilted at approximately 54° from the axis and the COO - groups run perpendicular to the axis. The determined orientation of chemical groups allowed the understanding of the orientation of D-diphenylalanine molecule that is consistent with its equilibrium conformation. The obtained data indicate that there is only one orientation of D-diphenylalanine molecules with respect to the nanotube main axis.

Friction force microscopy: a simple technique for identifying graphene on rough substrates and mapping the orientation of graphene grains on copper

NASA Astrophysics Data System (ADS)

Marsden, A. J.; Phillips, M.; Wilson, N. R.

2013-06-01

At a single atom thick, it is challenging to distinguish graphene from its substrate using conventional techniques. In this paper we show that friction force microscopy (FFM) is a simple and quick technique for identifying graphene on a range of samples, from growth substrates to rough insulators. We show that FFM is particularly effective for characterizing graphene grown on copper where it can correlate the graphene growth to the three-dimensional surface topography. Atomic lattice stick-slip friction is readily resolved and enables the crystallographic orientation of the graphene to be mapped nondestructively, reproducibly and at high resolution. We expect FFM to be similarly effective for studying graphene growth on other metal/locally crystalline substrates, including SiC, and for studying growth of other two-dimensional materials such as molybdenum disulfide and hexagonal boron nitride.

Determining Surface Roughness in Urban Areas Using Lidar Data

NASA Technical Reports Server (NTRS)

Holland, Donald

2009-01-01

An automated procedure has been developed to derive relevant factors, which can increase the ability to produce objective, repeatable methods for determining aerodynamic surface roughness. Aerodynamic surface roughness is used for many applications, like atmospheric dispersive models and wind-damage models. For this technique, existing lidar data was used that was originally collected for terrain analysis, and demonstrated that surface roughness values can be automatically derived, and then subsequently utilized in disaster-management and homeland security models. The developed lidar-processing algorithm effectively distinguishes buildings from trees and characterizes their size, density, orientation, and spacing (see figure); all of these variables are parameters that are required to calculate the estimated surface roughness for a specified area. By using this algorithm, aerodynamic surface roughness values in urban areas can then be extracted automatically. The user can also adjust the algorithm for local conditions and lidar characteristics, like summer/winter vegetation and dense/sparse lidar point spacing. Additionally, the user can also survey variations in surface roughness that occurs due to wind direction; for example, during a hurricane, when wind direction can change dramatically, this variable can be extremely significant. In its current state, the algorithm calculates an estimated surface roughness for a square kilometer area; techniques using the lidar data to calculate the surface roughness for a point, whereby only roughness elements that are upstream from the point of interest are used and the wind direction is a vital concern, are being investigated. This technological advancement will improve the reliability and accuracy of models that use and incorporate surface roughness.

Effects of orientation on the time decay of magnetization for cobalt-alloy thin film media

NASA Astrophysics Data System (ADS)

Wang, J. P.; Alex, Michael; Tan, L. P.; Yan, M. L.

1999-04-01

The dependence of the time decay of magnetization on orientation ratio was investigated for longitudinal Co-alloy thin film media. The coercivity orientation ratio was controlled by the degree of mechanical texture. For oriented samples, it was found that the remanent magnetization along the circumferential direction decayed faster with time than that along the radial direction when the applied reverse magnetic field was near the remanent coercivity. However, the remanent magnetization along the circumferential direction decayed more slowly with time than that along the radial direction when the applied reverse magnetic field was less than roughly half the remanent coercivity. Anisotropic interactions and magnetic anisotropy distributions appear to be the cause for the different time decay of magnetization along the circumferential and radial directions for oriented media.

Voltage‐Controlled Switching of Strong Light–Matter Interactions using Liquid Crystals

PubMed Central

Hertzog, Manuel; Rudquist, Per; Hutchison, James A.; George, Jino; Ebbesen, Thomas W.

2017-01-01

Abstract We experimentally demonstrate a fine control over the coupling strength of vibrational light–matter hybrid states by controlling the orientation of a nematic liquid crystal. Through an external voltage, the liquid crystal is seamlessly switched between two orthogonal directions. Using these features, for the first time, we demonstrate electrical switching and increased Rabi splitting through transition dipole moment alignment. The C−Nstr vibration on the liquid crystal molecule is coupled to a cavity mode, and FT‐IR is used to probe the formed vibropolaritonic states. A switching ratio of the Rabi splitting of 1.78 is demonstrated between the parallel and the perpendicular orientation. Furthermore, the orientational order increases the Rabi splitting by 41 % as compared to an isotropic liquid. Finally, by examining the influence of molecular alignment on the Rabi splitting, the scalar product used in theoretical modeling between light and matter in the strong coupling regime is verified. PMID:29155469

Simulation of anisotropic fracture behaviour of polycrystalline round blank tungsten using cohesive zone model

NASA Astrophysics Data System (ADS)

Mahler, Michael; Gaganidze, Ermile; Aktaa, Jarir

2018-04-01

The experimental observation of anisotropic fracture behaviour of round blank polycrystalline tungsten was simulated using finite element (FE) method in combination with cohesive zone model. Experiments in the past had shown that due to the anisotropic microstructure the fracture toughness varies by factor of about two for different orientations. The reason is the crack propagation direction, which is - in some orientations - not the typical crack propagation direction for mode I fracture. In some directions the crack is not growing perpendicular to the crack opening tensile load. Nevertheless, in the present paper, the microstructure is modelled by FE mesh including cohesive zone elements which mimic grain boundaries (GB). This is based on the assumption that GB's are the weakest links in the structure. The use of the correct parameters to describe the fracture process allows the description of the observed experimental orientation dependent fracture toughness.

Aligned 1-D nanorods of a π-gelator exhibit molecular orientation and excitation energy transport different from entangled fiber networks.

PubMed

Sakakibara, Keita; Chithra, Parayalil; Das, Bidisa; Mori, Taizo; Akada, Misaho; Labuta, Jan; Tsuruoka, Tohru; Maji, Subrata; Furumi, Seiichi; Shrestha, Lok Kumar; Hill, Jonathan P; Acharya, Somobrata; Ariga, Katsuhiko; Ajayaghosh, Ayyappanpillai

2014-06-18

Linear π-gelators self-assemble into entangled fibers in which the molecules are arranged perpendicular to the fiber long axis. However, orientation of gelator molecules in a direction parallel to the long axes of the one-dimensional (1-D) structures remains challenging. Herein we demonstrate that, at the air-water interface, an oligo(p-phenylenevinylene)-derived π-gelator forms aligned nanorods of 340 ± 120 nm length and 34 ± 5 nm width, in which the gelator molecules are reoriented parallel to the long axis of the rods. The orientation change of the molecules results in distinct excited-state properties upon local photoexcitation, as evidenced by near-field scanning optical microscopy. A detailed understanding of the mechanism by which excitation energy migrates through these 1-D molecular assemblies might help in the design of supramolecular structures with improved charge-transport properties.

Directed block copolymer self-assembly implemented via surface-embedded electrets

NASA Astrophysics Data System (ADS)

Wu, Mei-Ling; Wang, Dong; Wan, Li-Jun

2016-02-01

Block copolymer (BCP) nanolithography is widely recognized as a promising complementary approach to circumvent the feature size limits of conventional photolithography. The directed self-assembly of BCP thin film to form ordered nanostructures with controlled orientation and localized pattern has been the key challenge for practical nanolithography applications. Here we show that BCP nanopatterns can be directed on localized surface electrets defined by electron-beam irradiation to realize diverse features in a simple, effective and non-destructive manner. Charged electrets can generate a built-in electric field in BCP thin film and induce the formation of perpendicularly oriented microdomain of BCP film. The electret-directed orientation control of BCP film can be either integrated with mask-based patterning technique or realized by electron-beam direct-writing method to fabricate microscale arbitrary lateral patterns down to single BCP cylinder nanopattern. The electret-directed BCP self-assembly could provide an alternative means for BCP-based nanolithography, with high resolution.

Alumina plate containing photosystem I reaction center complex oriented inside plate-penetrating silica nanopores.

PubMed

Kamidaki, Chihiro; Kondo, Toru; Noji, Tomoyasu; Itoh, Tetsuji; Yamaguchi, Akira; Itoh, Shigeru

2013-08-22

The photosynthetic photosystem I reaction center complex (PSI-RC), which has a molecular diameter of 21 nm with 100 pigments, was incorporated into silica nanopores with a 100-nm diameter that penetrates an alumina plate of 60-μm thickness to make up an inorganic-biological hybrid photocell. PSI-RCs, purified from a thermophilic cyanobacterium, were stable inside the nanopores and rapidly photoreduced a mediator dye methyl viologen. The reduced dye was more stable inside nanopores suggesting the decrease of dissolved oxygen. The analysis by a cryogenic electron spin paramagnetic resonance indicated the oriented arrangement of RCs inside the 100-nm nanopores, with their surface parallel to the silica wall and perpendicular to the plane of the alumina plate. PSI RC complex in the semicrystalline orientation inside silica nanopores can be a new type of light energy conversion unit to supply strong reducing power selectively to other molecules inside or outside nanopores.

Orientamento della prima fase della moschea al-Aqşā di Gerusalemme

NASA Astrophysics Data System (ADS)

Di Cesare, Michelina

2017-07-01

A new interpretation of the archaeological data regarding the first of the three pre-Crusader structural phases of al-Aqşā mosque in Jerusalem (Aqşā I) is proposed. It suggests that the building had an astronomical orientation like other 7th-century and early 8th-century mosques. Thus, Aqşā I would have been oriented towards the East rather than the South, as believed so far. This hypothesis would allow to solve the anomalies of the plan of Aqşā I. Indeed, by identifying the eastern wall rather than the southern as the qiblī wall, the aisles would not result perpendicular but parallel to it and running along the long side, as usual in Umayyad mosques. Consequently, the precocious appearance of the transept in Aqşā II would be due to the re-orientation of the previous structure.

Shear-induced migration and orientation of rigid fibers

NASA Astrophysics Data System (ADS)

Butler, Jason; Strednak, Scott; Shaikh, Saif; Guazzelli, Elisabeth

2017-11-01

The spatial and orientation distributions are measured for a suspension of fibers during pressure-driven flow. The fibers are rigid and non-colloidal, and two aspect ratios (length to diameter ratios) of 12 and 24 were tested; the suspending fluid is viscous, Newtonian, and density matched to the particles. As with the migration of spheres in parabolic flows, the fibers migrate toward the centerline of the channel if the concentration is sufficiently high. Migration is not observed for concentrations below a volume fraction of 0.035 for aspect ratio 24 and 0.07 for aspect ratio 12. The orientation distribution of the fibers is spatially dependent. Fibers near the center of the channel align closely with the flow direction, but fibers near the wall are observed to preferentially align in the vorticity (perpendicular to the flow and gradient) direction. National Science Foundation (Grants #1511787 and #1362060).

Control of crystallographic texture and surface morphology of Pt/Tio2 templates for enhanced PZT thin film texture.

PubMed

Fox, Austin J; Drawl, Bill; Fox, Glen R; Gibbons, Brady J; Trolier-McKinstry, Susan

2015-01-01

Optimized processing conditions for Pt/TiO2/SiO2/Si templating electrodes were investigated. These electrodes are used to obtain [111] textured thin film lead zirconate titanate (Pb[ZrxTi1-x ]O3 0 ≤ x ≤ 1) (PZT). Titanium deposited by dc magnetron sputtering yields [0001] texture on a thermally oxidized Si wafer. It was found that by optimizing deposition time, pressure, power, and the chamber pre-conditioning, the Ti texture could be maximized while maintaining low surface roughness. When oxidized, titanium yields [100]-oriented rutile. This seed layer has as low as a 4.6% lattice mismatch with [111] Pt; thus, it is possible to achieve strongly oriented [111] Pt. The quality of the orientation and surface roughness of the TiO2 and the Ti directly affect the achievable Pt texture and surface morphology. A transition between optimal crystallographic texture and the smoothest templating surface occurs at approximately 30 nm of original Ti thickness (45 nm TiO2). This corresponds to 0.5 nm (2 nm for TiO2) rms roughness as determined by atomic force microscopy and a full-width at half-maximum (FWHM) of the rocking curve 0002 (200) peak of 5.5/spl degrees/ (3.1/spl degrees/ for TiO2). A Pb[Zr0.52Ti 0.48]O3 layer was deposited and shown to template from the textured Pt electrode, with a maximum [111] Lotgering factor of 87% and a minimum 111 FWHM of 2.4/spl degrees/ at approximately 30 nm of original Ti.

Molecular Dynamics Simulations of PIP2 and PIP3 in Lipid Bilayers: Determination of Ring Orientation, and the Effects of Surface Roughness on a Poisson-Boltzmann Description

PubMed Central

Li, Zheng; Venable, Richard M.; Rogers, Laura A.; Murray, Diana; Pastor, Richard W.

2009-01-01

Abstract Molecular dynamics (MD) simulations of phosphatidylinositol (4,5)-bisphosphate (PIP2) and phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers indicate that the inositol rings are tilted ∼40° with respect to the bilayer surface, as compared with 17° for the P-N vector of POPC. Multiple minima were obtained for the ring twist (analogous to roll for an airplane). The phosphates at position 1 of PIP2 and PIP3 are within an Ångström of the plane formed by the phosphates of POPC; lipids in the surrounding shell are depressed by 0.5–0.8 Å, but otherwise the phosphoinositides do not substantially perturb the bilayer. Finite size artifacts for ion distributions are apparent for systems of ∼26 waters/lipid, but, based on simulations with a fourfold increase of the aqueous phase, the phosphoinositide positions and orientations do not show significant size effects. Electrostatic potentials evaluated from Poisson-Boltzmann (PB) calculations show a strong dependence of potential height and ring orientation, with the maxima on the −25 mV surfaces (17.1 ± 0.1 Å for PIP2 and 19.4 ± 0.3 Å for PIP3) occurring near the most populated orientations from MD. These surfaces are well above the background height of 10 Å estimated for negatively charged cell membranes, as would be expected for lipids involved in cellular signaling. PB calculations on microscopically flat bilayers yield similar maxima as the MD-based (microscopically rough) systems, but show less fine structure and do not clearly indicate the most probable regions. Electrostatic free energies of interaction with pentalysine are also similar for the rough and flat systems. These results support the utility of a rigid/flat bilayer model for PB-based studies of PIP2 and PIP3 as long as the orientations are judiciously chosen. PMID:19580753

Intraplate Stress Field in South America Derived from Earthquake Focal Mechanisms

NASA Astrophysics Data System (ADS)

Dias, F. L.; Assumpcao, M.

2017-12-01

We present an updated compilation of earthquake focal mechanisms in Brazil together with the sub-Andean region through more obtained solutions together with published results from the literature and catalogs of international agencies. Stress orientations from breakouts and in-situ measurements were also compiled. The focal mechanisms were classified according to WSM (World Stress Map) criteria.For Brazil, we have 82 earthquakes with the mechanism that has been determined since 1978, begin that three new from this study. Focal mechanisms in Brazil show reverse, strike-slip and normal faulting while all events in the sub-Andean region have reverse (majority) or strike-slip mechanisms. For sub-Andean region have reverse (majority) or strike-slip mechanisms. Normal mechanisms can be found only in high attitudes. The mechanisms were grouped by proximity to be inverted for the stress tensor. We use the bootstrap technique to analyze the stability of the tensor. In SE Brazil and the Chaco-Pantanal basins, S1 tends to be oriented roughly E-W with S2 approximately equal to S3. This stress pattern changes to purely compressional (both SHmax and Shmin larger than Sv) in the São Francisco craton. A rotation of SHmax from E-W to SE-NW is suggested towards the Amazon region. Along the Atlantic margin, the regional stresses are affected by coastal effects. This coastal effect tends to make SHmax parallel to the coastline and Shmin (usually S3) perpendicular to the coastline. Few breakout data and in-situ measurements are available in Brazil and are generally consistent with the pattern derived from the earthquake focal mechanisms. In the sub-Andean region, the intermediate principal stress (S2) is also compressional, a feature that is not always reproduced in numerical models published in the literature. In mid-plate South America stresses seem to vary in nature and orientation. Although numerical models of global lithospheric stresses tend to reproduce the main large-scale features in most mid-plate areas, the S1 rotation from E-W in SE Brazil to SE-NW in the Amazon region are not well explained by the current numerical models. This means that the observed stress pattern in mid-plate South America should provide new insights into upper mantle dynamics, distinct from current global convection models.

Method of fabricating electrode catalyst layers with directionally oriented carbon support for proton exchange membrane fuel cell

DOEpatents

Liu, Di-Jia [Naperville, IL; Yang, Junbing [Bolingbrook, IL

2012-03-20

A membrane electrode assembly (MEA) of the invention comprises an anode and a cathode and a proton conductive membrane therebetween, the anode and the cathode each comprising a patterned sheet of longitudinally aligned transition metal-containing carbon nanotubes, wherein the carbon nanotubes are in contact with and are aligned generally perpendicular to the membrane, wherein a catalytically active transition metal is incorporated throughout the nanotubes.

Method and apparatus for improving the quality and efficiency of ultrashort-pulse laser machining

DOEpatents

Stuart, Brent C.; Nguyen, Hoang T.; Perry, Michael D.

2001-01-01

A method and apparatus for improving the quality and efficiency of machining of materials with laser pulse durations shorter than 100 picoseconds by orienting and maintaining the polarization of the laser light such that the electric field vector is perpendicular relative to the edges of the material being processed. Its use is any machining operation requiring remote delivery and/or high precision with minimal collateral dames.

The influence of juvenile wood content on shear parallel, compression,and tension perpendicular to grain strength and mode I fracture toughness of loblolly pine at various ring orientation

Treesearch

David E. Kretschmann

2008-01-01

Forest products from improved trees grown on managed plantations and harvested in short rotations will contain higher proportions of juvenile wood than in current harvests. More information is needed on the influence of juvenile wood on lumber properties. Most information developed to date has concentrated on ultimate tensile stress, modulus of rupture, and modulus of...

Orbiter/Space lab momentum management for POP orientations

NASA Technical Reports Server (NTRS)

Cox, J. W.

1974-01-01

An angular momentum management scheme applicable to the orbiter/spacelab is described. The basis of the scheme is to periodically maneuver the vehicle through a small angle thereby using the gravity gradient torque to dump momentum from the control moment gyro (CMG) control system. The orbiter is operated with its principal vehicle axis perpendicular to the orbital plane. Numerous case runs were conducted on the hybrid simulation and representative cases are included.

Multi-Wall Carbon Nanotubes for Flow-Induced Voltage Generation (Preprint)

DTIC Science & Technology

2006-08-01

flow sensors with a large dynamic range. The present work investigates voltage generation properties of multi-walled carbon nanotubes ( MWCNT ) as a...wall carbon nanotubes, has been generated from our perpendicularly-aligned MWCNT in an aqueous solution of 1 M NaCl at a relatively low flow velocity of...generation properties of multi-walled carbon nanotubes ( MWCNT ) as a function of the relative orientation of the nanotube array with respect to the flow

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

Reister, D.B.; Unseren, M.A.; Baker, J.E.

We discuss a series of surface following experiments using a range finder mounted on the end of an arm that is mounted on a vehicle. The goal is to keep the range finder at a fixed distance from an unknown surface and to keep the orientation of the range finder perpendicular to the surface. During the experiments, the vehicle moves along a predefined trajectory while planning software determines the position and orientation of the arm. To keep the range finder perpendicular to the surface, the planning software calculates the surface normal for the unknown surface. We assume that the unknownmore » surface is a cylinder (the surface depends on x and y but does not depend on z). To calculate the surface normal, the planning software must calculate the locations (x,y) of points on the surface in world coordinates. The calculation requires data on the position and orientation of the vehicle, the position and orientation of the arm, and the distance from the range finder to the surface. We discuss four series of experiments. During the first series of experiments, the calculated surface normal values had large high frequency random variations. A filter was used to produce an average value for the surface normal and we limited the rate of change in the yaw angle target for the arm. We performed the experiment for a variety of concave and convex surfaces. While the experiments were qualitative successes, the measured distance to the surface was significantly different than the target. The distance errors were systematic, low frequency, and had magnitudes up to 25 mm. During the second series of experiments, we reduced the variations in the calculated surface normal values. While reviewing the data collected while following the surface of a barrel, we found that the radius of the calculated surface was significantly different than the measured radius of the barrel.« less

Connective Tissue Characteristics around Healing Abutments of Different Geometries: New Methodological Technique under Circularly Polarized Light.

PubMed

Delgado-Ruiz, Rafael Arcesio; Calvo-Guirado, Jose Luis; Abboud, Marcus; Ramirez-Fernandez, Maria Piedad; Maté-Sánchez de Val, José Eduardo; Negri, Bruno; Gomez-Moreno, Gerardo; Markovic, Aleksa

2015-08-01

To describe contact, thickness, density, and orientation of connective tissue fibers around healing abutments of different geometries by means of a new method using coordinates. Following the bilateral extraction of mandibular premolars (P2, P3, and P4) from six fox hound dogs and a 2-month healing period, 36 titanium implants were inserted, onto which two groups of healing abutments of different geometry were screwed: Group A (concave abutments) and Group B (wider healing abutment). After 3 months the animals were sacrificed and samples extracted containing each implant and surrounding soft and hard tissues. Histological analysis was performed without decalcifying the samples by means of circularly polarized light under optical microscope and a system of vertical and horizontal coordinates across all the connective tissue in an area delimited by the implant/abutment, epithelium, and bone tissue. In no case had the connective tissue formed a connection to the healing abutment/implant in the internal zone; a space of 35 ± 10 μm separated the connective tissue fibers from the healing abutment surface. The total thickness of connective tissue in the horizontal direction was significantly greater in the medial zone in Group B than in Group A (p < .05). The orientation of the fibers varied according to the coordinate area so that internal coordinates showed a higher percentage of parallel fibers in Group A (p < .05) and a higher percentage of oblique fibers in Group B (p < .05); medial coordinates showed more oblique fibers (p < .05); and the area of external coordinates showed the highest percentage of perpendicular fibers (p < .05). The fiber density was higher in the basal and medial areas (p < .05). Abutment geometry influences the orientation of collagen fibers; therefore, an abutment with a profile wider than the implant platform favors oblique and perpendicular orientation of collagen fibers and greater connective tissue thickness. © 2013 Wiley Periodicals, Inc.

Hierarchically Ordered Nanopatterns for Spatial Control of Biomolecules

PubMed Central

2015-01-01

The development and study of a benchtop, high-throughput, and inexpensive fabrication strategy to obtain hierarchical patterns of biomolecules with sub-50 nm resolution is presented. A diblock copolymer of polystyrene-b-poly(ethylene oxide), PS-b-PEO, is synthesized with biotin capping the PEO block and 4-bromostyrene copolymerized within the polystyrene block at 5 wt %. These two handles allow thin films of the block copolymer to be postfunctionalized with biotinylated biomolecules of interest and to obtain micropatterns of nanoscale-ordered films via photolithography. The design of this single polymer further allows access to two distinct superficial nanopatterns (lines and dots), where the PEO cylinders are oriented parallel or perpendicular to the substrate. Moreover, we present a strategy to obtain hierarchical mixed morphologies: a thin-film coating of cylinders both parallel and perpendicular to the substrate can be obtained by tuning the solvent annealing and irradiation conditions. PMID:25363506

Polarization-Resolved Study of High Harmonics from Bulk Semiconductors

NASA Astrophysics Data System (ADS)

Kaneshima, Keisuke; Shinohara, Yasushi; Takeuchi, Kengo; Ishii, Nobuhisa; Imasaka, Kotaro; Kaji, Tomohiro; Ashihara, Satoshi; Ishikawa, Kenichi L.; Itatani, Jiro

2018-06-01

The polarization property of high harmonics from gallium selenide is investigated using linearly polarized midinfrared laser pulses. With a high electric field, the perpendicular polarization component of the odd harmonics emerges, which is not present with a low electric field and cannot be explained by the perturbative nonlinear optics. A two-dimensional single-band model is developed to show that the anisotropic curvature of an energy band of solids, which is pronounced in an outer part of the Brillouin zone, induces the generation of the perpendicular odd harmonics. This model is validated by three-dimensional quantum mechanical simulations, which reproduce the orientation dependence of the odd-order harmonics. The quantum mechanical simulations also reveal that the odd- and even-order harmonics are produced predominantly by the intraband current and interband polarization, respectively. These experimental and theoretical demonstrations clearly show a strong link between the band structure of a solid and the polarization property of the odd-order harmonics.

Fractional lattice charge transport

NASA Astrophysics Data System (ADS)

Flach, Sergej; Khomeriki, Ramaz

2017-01-01

We consider the dynamics of noninteracting quantum particles on a square lattice in the presence of a magnetic flux α and a dc electric field E oriented along the lattice diagonal. In general, the adiabatic dynamics will be characterized by Bloch oscillations in the electrical field direction and dispersive ballistic transport in the perpendicular direction. For rational values of α and a corresponding discrete set of values of E(α) vanishing gaps in the spectrum induce a fractionalization of the charge in the perpendicular direction - while left movers are still performing dispersive ballistic transport, the complementary fraction of right movers is propagating in a dispersionless relativistic manner in the opposite direction. Generalizations and the possible probing of the effect with atomic Bose-Einstein condensates and photonic networks are discussed. Zak phase of respective band associated with gap closing regime has been computed and it is found converging to π/2 value.

Intercalation complex of proflavine with DNA: Structure and dynamics by solid-state NMR

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

Tang, Pei; Juang, Chilong; Harbison, G.S.

1990-07-06

The structure of the complex formed between the intercalating agent proflavine and fibrous native DNA was studied by one- and two-dimensional high-resolution solid-state nuclear magnetic resonance (NMR). Carbon-13-labeled proflavine was used to show that the drug is stacked with the aromatic ring plane perpendicular to the fiber axis and that it is essentially immobile. Natural abundance carbon-13 NMR of the DNA itself shows that proflavine binding does not change the puckering of the deoxyribose ring. However, phosphorus-31 NMR spectra show profound changes in the orientation of the phosphodiester grouping on proflavine binding, with some of the phosphodiesters tilting almost parallelmore » to the helix axis, and a second set almost perpendicular. The first group to the phosphodiesters probably spans the intercalation sites, whereas the tilting of the second set likely compensates for the unwinding of the DNA by the intercalator.« less

Variable area light reflecting assembly

DOEpatents

Howard, T.C.

1986-12-23

Device is described for tracking daylight and projecting it into a building. The device tracks the sun and automatically adjusts both the orientation and area of the reflecting surface. The device may be mounted in either a wall or roof of a building. Additionally, multiple devices may be employed in a light shaft in a building, providing daylight to several different floors. The preferred embodiment employs a thin reflective film as the reflecting device. One edge of the reflective film is fixed, and the opposite end is attached to a spring-loaded take-up roller. As the sun moves across the sky, the take-up roller automatically adjusts the angle and surface area of the film. Additionally, louvers may be mounted at the light entrance to the device to reflect incoming daylight in an angle perpendicular to the device to provide maximum reflective capability when daylight enters the device at non-perpendicular angles. 9 figs.

Variable area light reflecting assembly

DOEpatents

Howard, Thomas C.

1986-01-01

Device for tracking daylight and projecting it into a building. The device tracks the sun and automatically adjusts both the orientation and area of the reflecting surface. The device may be mounted in either a wall or roof of a building. Additionally, multiple devices may be employed in a light shaft in a building, providing daylight to several different floors. The preferred embodiment employs a thin reflective film as the reflecting device. One edge of the reflective film is fixed, and the opposite end is attached to a spring-loaded take-up roller. As the sun moves across the sky, the take-up roller automatically adjusts the angle and surface area of the film. Additionally, louvers may be mounted at the light entrance to the device to reflect incoming daylight in an angle perpendicular to the device to provide maximum reflective capability when daylight enters the device at non-perpendicular angles.

Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al2O3 templates

NASA Astrophysics Data System (ADS)

Maximenko, A.; Fedotova, J.; Marszałek, M.; Zarzycki, A.; Zabila, Y.

2016-02-01

Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L10 structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment.

Graphoepitaxy integration and pattern transfer of lamellar silicon-containing high-chi block copolymers

NASA Astrophysics Data System (ADS)

Bézard, P.; Chevalier, X.; Legrain, A.; Navarro, C.; Nicolet, C.; Fleury, G.; Cayrefourcq, I.; Tiron, R.; Zelsmann, M.

2018-03-01

In this work, we present our recent achievements on the integration and transfer etching of a novel silicon-containing high-χ block copolymer for lines/spaces applications. Developed carbo-silane BCPs are synthesized under industrial conditions and present periodicities as low as 14 nm. A full directed self-assembly by graphoepitaxy process is shown using standard photolithography stacks and all processes are performed on 300 mm wafer compatible tools. Specific plasma processes are developed to isolate perpendicular lamellae and sub-12 nm features are finally transferred into silicon substrates. The quality of the final BCP hard mask (CDU, LWR, LER) are also investigated. Finally, thanks to the development of dedicated neutral layers and top-coats allowing perpendicular orientations, it was possible to investigate plasma etching experiments on full-sheets at 7 nm resolution, opening the way to the integration of these polymers in chemoepitaxy stacks.

Chaotic motion of a harmonically bound charged particle in a magnetic field, in the presence of a half-plane barrier

NASA Astrophysics Data System (ADS)

Geurts, Bernard J.; Wiegel, Frederik W.; Creswick, Richard J.

1990-05-01

The motion in the plane of an harmonically bound charged particle interacting with a magnetic field and a half-plane barrier along the positive x-axis is studied. The magnetic field is perpendicular to the plane in which the particle moves. This motion is integrable in between collisions of the particle with the barrier. However, the overall motion of the particle is very complicated. Chaotic regions in phase space exist next to island structures associated with linearly stable periodic orbits. We study in detail periodic orbits of low period and in particular their bifurcation behavior. Independent sequences of period doubling bifurcations and resonant bifurcations are observed associated with independent fixed points in the Poincaré section. Due to the perpendicular magnetic field an orientation is induced on the plane and time-reversal symmetry is broken.

Surface-enhanced Raman scattering studies on bombesin, its selected fragments and related peptides adsorbed at the silver colloidal surface

NASA Astrophysics Data System (ADS)

Podstawka-Proniewicz, Edyta; Ozaki, Yukihiro; Kim, Younkyoo; Xu, Yizhuang; Proniewicz, Leonard M.

2011-07-01

SERS studies presented in this work on BN8-14, [ D-Phe 6,β-Ala11,Phe13,Nle14]BN6-14, [ D-Tyr 6, β-Ala11,Phe13,Nle14]BN6-14, BN and its modified analogues, as well as NMB, NMC, and PG-L show that these molecules at pH 8.3 bind to a colloidal silver surface mainly through Trp 8 and Met 14 residues. Trp 8 adsorbs at the surface almost perpendicularly. Met 14 appears on the surface mainly as a P C-G conformer. His 12, as is evident from the spectra, practically does not take part in the adsorption process. Substitution of L-leucine at the 13 position of amino acid sequence with L-phenylalanine does not change substantially the pattern of the adsorption mechanism; however, substitution of phenylalanine at the 12 position (instead of L-histidine) causes changes in the SERS spectra that show that Phe 12 takes parallel orientation to the surface upon adsorption of [ D-Phe 12]BN, while in the case of [Tyr4, D-Phe 12]BN this residue is perpendicular to the surface and influences the orientation of the bound Trp 8. On the other hand, substitution of Asn with Tyr in the 6 position in nonapeptide fragment causes changes in the adsorption mechanism. In this case, the discussed fragment binds to the silver colloidal surface by Tyr 6, Trp 8, and Met 14. The SERS spectrum of NMC is very similar to that of BN; although it differs by the binding orientation of the amide bond towards the surface. Appearance of Phe 13 in NMB and PG-L causes that this residue competes successfully with Trp 8 forcing it to take tilted orientation. As seen from the enhancement of the characteristic Phe vibrations this moiety in NMB and PG-L adsorbs on the silver surface in a tilted fashion. This arrangements cause that the 8-14 peptide chain in all these studied compounds takes almost a parallel orientation to the surface while the 1-5 fragment of the peptide chain is removed from the silver surface vicinity.

SAR Polarimetry

NASA Technical Reports Server (NTRS)

vanZyl, Jakob J.

2012-01-01

Radar Scattering includes: Surface Characteristics, Geometric Properties, Dielectric Properties, Rough Surface Scattering, Geometrical Optics and Small Perturbation Method Solutions, Integral Equation Method, Magellan Image of Pancake Domes on Venus, Dickinson Impact Crater on Venus (Magellan), Lakes on Titan (Cassini Radar, Longitudinal Dunes on Titan (Cassini Radar), Rough Surface Scattering: Effect of Dielectric Constant, Vegetation Scattering, Effect of Soil Moisture. Polarimetric Radar includes: Principles of Polarimetry: Field Descriptions, Wave Polarizations: Geometrical Representations, Definition of Ellipse Orientation Angles, Scatter as Polarization Transformer, Scattering Matrix, Coordinate Systems, Scattering Matrix, Covariance Matrix, Pauli Basis and Coherency Matrix, Polarization Synthesis, Polarimeter Implementation.

Effect of heavy metal layer thickness on spin-orbit torque and current-induced switching in Hf|CoFeB|MgO structures

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

Akyol, Mustafa; Jiang, Wanjun; Yu, Guoqiang

We study the heavy metal layer thickness dependence of the current-induced spin-orbit torque (SOT) in perpendicularly magnetized Hf broken vertical bar CoFeB broken vertical bar MgO multilayer structures. The damping-like (DL) current-induced SOT is determined by vector anomalous Hall effect measurements. A non-monotonic behavior in the DL-SOT is found as a function of the thickness of the heavy-metal layer. The sign of the DL-SOT changes with increasing the thickness of the Hf layer in the trilayer structure. As a result, in the current-driven magnetization switching, the preferred direction of switching for a given current direction changes when the Hf thicknessmore » is increased above similar to 7 nm. Although there might be a couple of reasons for this unexpected behavior in DL-SOT, such as the roughness in the interfaces and/or impurity based electric potential in the heavy metal, one can deduce a roughness dependence sign reversal in DL-SOT in our trilayer structure.« less

Effect of heavy metal layer thickness on spin-orbit torque and current-induced switching in Hf|CoFeB|MgO structures

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

Akyol, Mustafa; Department of Physics, University of Çukurova, Adana 01330; Jiang, Wanjun

We study the heavy metal layer thickness dependence of the current-induced spin-orbit torque (SOT) in perpendicularly magnetized Hf|CoFeB|MgO multilayer structures. The damping-like (DL) current-induced SOT is determined by vector anomalous Hall effect measurements. A non-monotonic behavior in the DL-SOT is found as a function of the thickness of the heavy-metal layer. The sign of the DL-SOT changes with increasing the thickness of the Hf layer in the trilayer structure. As a result, in the current-driven magnetization switching, the preferred direction of switching for a given current direction changes when the Hf thickness is increased above ∼7 nm. Although there might bemore » a couple of reasons for this unexpected behavior in DL-SOT, such as the roughness in the interfaces and/or impurity based electric potential in the heavy metal, one can deduce a roughness dependence sign reversal in DL-SOT in our trilayer structure.« less

Spin-dependence of the electron scattering cross section by a magnetic layer system and the magneto-resistance

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

Wang, J.T.; Tang, F.; Brown, W.D.

1998-12-20

The authors present a theoretical model for calculating the spin-dependent cross section of the scattering of electrons by a magnetic layer system. The model demonstrates that the cross sections of the scattering are different for spin up and spin down electrons. The model assumes that the electrical resistivity in a conductor is proportional to the scattering cross section of the electron in it. It is believed to support the two channel mechanism in interpreting magneto-resistance (MR). Based on the model without considering the scattering due to the interfacial roughness and the spin flipping scattering, the authors have established a relationshipmore » between MR and the square of the magnetic moment in the bulk sample without considering the scattering due to the interfacial roughness and the spin flipping scattering. It can also qualitatively explain the MR difference between the current in plane (CIP) and current perpendicular to the plane (CPP) configurations. The predictions by the model agree well with the experimental findings.« less

Bio-inspired canopies for the reduction of roughness noise

NASA Astrophysics Data System (ADS)

Clark, Ian A.; Daly, Conor A.; Devenport, William; Alexander, W. Nathan; Peake, Nigel; Jaworski, Justin W.; Glegg, Stewart

2016-12-01

This work takes inspiration from the structure of the down covering the flight feathers of larger species of owls, which contributes to their ability to fly almost silently at frequencies above 1.6 kHz. Microscope photographs of the down show that it consists of hairs that form a structure similar to that of a forest. The hairs initially rise almost perpendicular to the feather surface but then bend over in the flow direction to form a canopy with an open area ratio of about 70 percent. Experiments have been performed to examine the noise radiated by a large open area ratio canopy suspended above a surface. The canopy is found to dramatically reduce pressure fluctuations on the underlying surface. While the canopy can produce its own sound, particularly at high frequencies, the reduction in surface pressure fluctuations can reduce the noise scattered from an underlying rough surface at lower frequencies. A theoretical model is developed which characterizes the mechanism of surface pressure reduction as a result of the mixing layer instability of flow over forest canopies.

Effect of interfacial intermixing on the Dzyaloshinskii-Moriya interaction in Pt/Co/Pt

NASA Astrophysics Data System (ADS)

Wells, Adam W. J.; Shepley, Philippa M.; Marrows, Christopher H.; Moore, Thomas A.

2017-02-01

We study the effect of sputter-deposition conditions, namely, substrate temperature and chamber base pressure, upon the interface quality of epitaxial Pt/Co/Pt thin films with perpendicular magnetic anisotropy. Here we define interface quality to be the inverse of the sum in quadrature of roughness and intermixing. We find that samples with the top Co/Pt layers grown at 250 ∘C exhibit a local maximum in roughness intermixing and that the interface quality is better for lower or higher deposition temperatures, up to 400 ∘C,above which the interface quality degrades. Imaging the expansion of magnetic domains in an in-plane field using wide-field Kerr microscopy, we determine the interfacial Dzyaloshinskii-Moriya interaction (DMI) in films in the deposition temperature range 100 ∘C to 300 ∘C . We find that the net DMI increases as the difference between top and bottom Co interface quality increases. Furthermore, for sufficiently low base pressures, the net DMI increases linearly with the deposition temperature, indicating that fine-tuning of the DMI may be achieved via the deposition conditions.

Characterization, modeling and simulation of fused deposition modeling fabricated part surfaces

NASA Astrophysics Data System (ADS)

Taufik, Mohammad; Jain, Prashant K.

2017-12-01

Surface roughness is generally used for characterization, modeling and simulation of fused deposition modeling (FDM) fabricated part surfaces. But the average surface roughness is not able to provide the insight of surface characteristics with sharp peaks and deep valleys. It deals in the average sense for all types of surfaces, including FDM fabricated surfaces with distinct surface profile features. The present research work shows that kurtosis and skewness can be used for characterization, modeling and simulation of FDM surfaces because these roughness parameters have the ability to characterize a surface with sharp peaks and deep valleys. It can be critical in certain application areas in tribology and biomedicine, where the surface profile plays an important role. Thus, in this study along with surface roughness, skewness and kurtosis are considered to show a novel strategy to provide new transferable knowledge about FDM fabricated part surfaces. The results suggest that the surface roughness, skewness and kurtosis are significantly different at 0° and in the range (0°, 30°], [30°, 90°] of build orientation.

High quality TmIG films with perpendicular magnetic anisotropy grown by sputtering

NASA Astrophysics Data System (ADS)

Wu, C. N.; Tseng, C. C.; Yeh, S. L.; Lin, K. Y.; Cheng, C. K.; Fanchiang, Y. T.; Hong, M.; Kwo, J.

Ferrimagnetic thulium iron garnet (TmIG) films grown on gadolinium gallium garnet substrates recently showed stress-induced perpendicular magnetic anisotropy (PMA), attractive for realization of quantum anomalous Hall effect (QAHE) of topological insulator (TI) films via the proximity effect. Moreover, current induced magnetization switching of Pt/TmIG has been demonstrated for the development of room temperature (RT) spintronic devices. In this work, high quality TmIG films (about 25nm) were grown by sputtering at RT followed by post-annealing. We showed that the film composition is tunable by varying the growth parameters. The XRD results showed excellent crystallinity of stoichiometric TmIG films with an out-of-plane lattice constant of 1.2322nm, a narrow film rocking curve of 0.017 degree, and a film roughness of 0.2 nm. The stoichiometric films exhibited PMA and the saturation magnetization at RT was 109 emu/cm3 (RT bulk value 110 emu/cm3) with a coercive field of 2.7 Oe. In contrast, TmIG films of Fe deficiency showed in-plane magnetic anisotropy. The high quality sputtered TmIG films will be applied to heterostructures with TIs or metals with strong spin-orbit coupling for novel spintronics.

Properties of perpendicular-anisotropy magnetic tunnel junctions fabricated over the bottom electrode contact

NASA Astrophysics Data System (ADS)

Miura, Sadahiko; Honjo, Hiroaki; Kinoshita, Keizo; Tokutome, Keiichi; Koike, Hiroaki; Ikeda, Shoji; Endoh, Tetsuo; Ohno, Hideo

2015-04-01

Perpendicular-anisotropy magnetic tunnel junctions (MTJs) were prepared on four substrate geometries, i.e., directly on the axis of the bottom electrode contact, directly off the axis of the bottom electrode contact, on the axis of the bottom electrode contact with a polished bottom electrode, and off the axis of the bottom electrode contact with a polished bottom electrode. Electrical shorts were observed for direct on-axis geometry at a certain extent, whereas there were no electrical shorts for the other three geometries. The MR ratio/σR, JC0, and thermal stability factor of the devices for polish on-axis geometry were almost the same as those for polish off-axis geometry. From TEM observations of the polish on-axis device, the interface between the bottom contact and the base electrode was determined to be rough, whereas the MgO barrier layer was determined to be smooth, indicating that the polish process was effective for smooth magnetic tunnel junction fabrication over the bottom contact. MTJs for polish on-axis geometry eliminated the base electrode resistance and increased the magnetoresistance ratio. This technology contributes to the higher density of spin transfer torque magnetic random access memory.

Rough viscoelastic sliding contact: Theory and experiments

NASA Astrophysics Data System (ADS)

Carbone, G.; Putignano, C.

2014-03-01

In this paper, we show how the numerical theory introduced by the authors [Carbone and Putignano, J. Mech. Phys. Solids 61, 1822 (2013), 10.1016/j.jmps.2013.03.005] can be effectively employed to study the contact between viscoelastic rough solids. The huge numerical complexity is successfully faced up by employing the adaptive nonuniform mesh developed by the authors in Putignano et al. [J. Mech. Phys. Solids 60, 973 (2012), 10.1016/j.jmps.2012.01.006]. Results mark the importance of accounting for viscoelastic effects to correctly simulate the sliding rough contact. In detail, attention is, first, paid to evaluate the viscoelastic dissipation, i.e., the viscoelastic friction. Fixed the sliding speed and the normal load, friction is completely determined. Furthermore, since the methodology employed in the work allows to study contact between real materials, a comparison between experimental outcomes and numerical prediction in terms of viscoelastic friction is shown. The good agreement seems to validate—at least partially—the presented methodology. Finally, it is shown that viscoelasticity entails not only the dissipative effects previously outlined, but is also strictly related to the anisotropy of the contact solution. Indeed, a marked anisotropy is present in the contact region, which results stretched in the direction perpendicular to the sliding speed. In the paper, the anisotropy of the deformed surface and of the contact area is investigated and quantified.

Topography evolution of rough-surface metallic substrates by solution deposition planarization method

NASA Astrophysics Data System (ADS)

Chu, Jingyuan; Zhao, Yue; Liu, Linfei; Wu, Wei; Zhang, Zhiwei; Hong, Zhiyong; Li, Yijie; Jin, Zhijian

2018-01-01

As an emerging technique for surface smoothing, solution deposition planarization (SDP) has recently drawn more attention on the fabrication of the second generation high temperature superconducting (2G-HTS) tapes. In our work, a number of amorphous oxide layers were deposited on electro-polished or mirror-rolled metallic substrates by chemical solution route. Topography evolution of surface defects on these two types of metallic substrates was thoroughly investigated by atomic force microscopy (AFM). It was showed that root mean square roughness values (at 50 × 50 μm2 scanning scale) on both rough substrates reduced to ∼5 nm after coating with SDP-layer. The smoothing effect was mainly attributed to decrease of the depth at grain boundary grooving on the electro-polished metallic substrate. On the mirror-rolled metallic substrates, the amplitude and frequency of the height fluctuation perpendicular to the rolling direction were gradually reduced as depositing more numbers of SDP-layer. A high Jc value of 4.17 MA cm-2 (at 77 K, s.f.) was achieved on a full stack of YBCO/CeO2/IBAD-MgO/SDP-layer/C276 sample. This study enhanced understanding of the topography evolution on the surface defects covered by the SDP-layer, and demonstrated a low-cost route for fabricating IBAD-MgO based YBCO templates with a simplified architecture.

Comparison of carotid plaque ulcer detection using contrast-enhanced and time-of-flight MRA techniques.

PubMed

Etesami, M; Hoi, Y; Steinman, D A; Gujar, S K; Nidecker, A E; Astor, B C; Portanova, A; Qiao, Y; Abdalla, W M A; Wasserman, B A

2013-01-01

Ulceration in carotid plaque is a risk indicator for ischemic stroke. Our aim was to compare plaque ulcer detection by standard TOF and CE-MRA techniques and to identify factors that influence its detection. Carotid MR imaging scans were acquired on 2066 participants in the ARIC study. We studied the 600 thickest plaques. TOF-MRA, CE-MRA, and black-blood MR images were analyzed together to define ulcer presence (plaque surface niche ≥2 mm in depth). Sixty ulcerated arteries were detected. These arteries were randomly assigned, along with 40 nonulcerated plaques from the remaining 540, for evaluation of ulcer presence by 2 neuroradiologists. Associations between ulcer detection and ulcer characteristics, including orientation, location, and size, were determined and explored by CFD modeling. One CE-MRA and 3 TOF-MRAs were noninterpretable and excluded. Of 71 ulcers in 56 arteries, readers detected an average of 39 (55%) on both TOF-MRA and CE-MRA, 26.5 (37.5%) only on CE-MRA, and 1 (1.5%) only on TOF-MRA, missing 4.5 (6%) ulcers by both methods. Ulcer detection by TOF-MRA was associated with its orientation (distally pointing versus perpendicular: OR = 5.57 [95% CI, 1.08-28.65]; proximally pointing versus perpendicular: OR = 0.21 [95% CI, 0.14-0.29]); location relative to point of maximum stenosis (distal versus isolevel: OR = 5.17 [95% CI, 2.10-12.70]); and neck-to-depth ratio (OR = 1.96 [95% CI, 1.11-3.45]) after controlling for stenosis and ulcer volume. CE-MRA detects more ulcers than TOF-MRA in carotid plaques. Missed ulcers on TOF-MRA are influenced by ulcer orientation, location relative to point of maximum stenosis, and neck-to-depth ratio.

Cyclohexene oxide/CO2 copolymerization catalyzed by chromium(III) salen complexes and N-methylimidazole: effects of varying salen ligand substituents and relative cocatalyst loading.

PubMed

Darensbourg, Donald J; Mackiewicz, Ryan M; Rodgers, Jody L; Fang, Cindy C; Billodeaux, Damon R; Reibenspies, Joseph H

2004-09-20

A detailed mechanistic study into the copolymerization of CO2 and cyclohexene oxide utilizing CrIII(salen)X complexes and N-methylimidazole, where H2salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine and other salen derivatives and X = Cl or N3, has been conducted. By studying salen ligands with various groups on the diimine backbone, we have observed that bulky groups oriented perpendicular to the salen plane reduce the activity of the catalyst significantly, while such groups oriented parallel to the salen plane do not retard copolymer formation. This is not surprising in that the mechanism for asymmetric ring opening of epoxides was found to occur in a bimetallic fashion, whereas these perpendicularly oriented groups along with the tert-butyl groups on the phenolate rings produce considerable steric requirements for the two metal centers to communicate and thus initiate the copolymerization process. It was also observed that altering the substituents on the phenolate rings of the salen ligand had a 2-fold effect, controlling both catalyst solubility as well as electron density around the metal center, producing significant effects on the rate of copolymer formation. This and other data discussed herein have led us to propose a more detailed mechanistic delineation, wherein the rate of copolymerization is dictated by two separate equilibria. The first equilibrium involves the initial second-order epoxide ring opening and is inhibited by excess amounts of cocatalyst. The second equilibrium involves the propagation step and is enhanced by excess cocatalyst. This gives the [cocatalyst] both a positive and negative effect on the overall rate of copolymerization. Copyright 2004 American Chemical Society

Orientation Control in Thin Films of a High-χ Block Copolymer with a Surface Active Embedded Neutral Layer.

PubMed

Zhang, Jieqian; Clark, Michael B; Wu, Chunyi; Li, Mingqi; Trefonas, Peter; Hustad, Phillip D

2016-01-13

Directed self-assembly (DSA) of block copolymers (BCPs) is an attractive advanced patterning technology being considered for future integrated circuit manufacturing. By controlling interfacial interactions, self-assembled microdomains in thin films of polystyrene-block-poly(methyl methacrylate), PS-b-PMMA, can be oriented perpendicular to surfaces to form line/space or hole patterns. However, its relatively weak Flory interaction parameter, χ, limits its capability to pattern sub-10 nm features. Many BCPs with higher interaction parameters are capable of forming smaller features, but these "high-χ" BCPs typically have an imbalance in surface energy between the respective blocks that make it difficult to achieve the required perpendicular orientation. To address this challenge, we devised a polymeric surface active additive mixed into the BCP solution, referred to as an embedded neutral layer (ENL), which segregates to the top of the BCP film during casting and annealing and balances the surface tensions at the top of the thin film. The additive comprises a second BCP with a "neutral block" designed to provide matched surface tensions with the respective polymers of the main BCP and a "surface anchoring block" with very low surface energy that drives the material to the air interface during spin-casting and annealing. The surface anchoring block allows the film to be annealed above the glass transition temperature of the two materials without intermixing of the two components. DSA was also demonstrated with this embedded neutral top layer formulation on a chemical patterned template using a single step coat and simple thermal annealing. This ENL technology holds promise to enable the use of high-χ BCPs in advanced patterning applications.

The Effect of Sn Orientation on Intermetallic Compound Growth in Idealized Sn-Cu-Ag Interconnects

NASA Astrophysics Data System (ADS)

Kinney, Chris; Linares, Xioranny; Lee, Kyu-Oh; Morris, J. W.

2013-04-01

The work reported here explores the influence of crystal orientation on the growth of the interfacial intermetallic layer during electromigration in Cu||Sn||Cu solder joints. The samples were thin, planar Sn-Ag-Cu (SAC) solder layers between Cu bars subject to a uniaxial current. Electron backscatter diffraction (EBSD) was used to characterize the microstructure before and after testing. The most useful representation of the EBSD data identifies the Sn grain orientation by the angle between the Sn c-axis and the current direction. The tested samples included single-crystal joints with c-axis nearly parallel to the current ("green" samples) and with c-axis perpendicular to the current ("red" samples). At current density of 104 A/cm2 (steady-state temperature of ~150°C), an intermetallic layer grew at an observable rate in the "green" samples, but not in the "red" ones. A current density of 1.15 × 104 A/cm2 (temperature ~160°C) led to measurable intermetallic growth in both samples. The growth fronts were nearly planar and the growth rates constant (after an initial incubation period); the growth rates in the "green" samples were about 10× those in the "red" samples. The Cu concentrations were constant within the joints, showing that the intermetallic growth is dominated by the electromigration flux. The measured growth rates and literature values for the diffusion of Cu in Sn were used to extract values for the effective charge, z *, that governs the electromigration of Cu. The calculated value of z * is significantly larger for current perpendicular to the c-axis than along it.

Anisotropy of electrical conductivity in dc due to intrinsic defect formation in α-Al2O3 single crystal implanted with Mg ions

NASA Astrophysics Data System (ADS)

Tardío, M.; Egaña, A.; Ramírez, R.; Muñoz-Santiuste, J. E.; Alves, E.

2016-07-01

The electrical conductivity in α-Al2O3 single crystals implanted with Mg ions in two different crystalline orientations, parallel and perpendicular to c axis, was investigated. The samples were implanted at room temperature with energies of 50 and 100 keV and fluences of 1 × 1015, 5 × 1015 and 5 × 1016 ions/cm2. Optical characterization reveals slight differences in the absorption bands at 6.0 and 4.2 eV, attributed to F type centers and Mie scattering from Mg precipitates, respectively. DC electrical measurements using the four and two-point probe methods, between 295 and 490 K, were used to characterize the electrical conductivity of the implanted area (Meshakim and Tanabe, 2001). Measurements in this temperature range indicate that: (1) the electrical conductivity is thermally activated independently of crystallographic orientation, (2) resistance values in the implanted region decrease with fluence levels, and (3) the I-V characteristic of electrical contacts in samples with perpendicular c axis orientation is clearly ohmic, whereas contacts are blocking in samples with parallel c axis. When thin layers are sequentially removed from the implanted region by immersing the sample in a hot solution of nitric and fluorhydric acids the electrical resistance increases until reaching the values of non-implanted crystal (Jheeta et al., 2006). We conclude that the enhancement in conductivity observed in the implanted regions is related to the intrinsic defects created by the implantation rather than to the implanted Mg ions (da Silva et al., 2002; Tardío et al., 2001; Tardío et al., 2008).

Molecular dynamics simulations of shock waves in oriented nitromethane single crystals: plane-specific effects.

PubMed

He, Lan; Sewell, Thomas D; Thompson, Donald L

2012-01-21

Molecular dynamics simulations of supported shock waves (shock pressure P(s) ∼ 15 GPa) propagating along the [110], [011], [101], and [111] directions in crystalline nitromethane initially at T = 200 K were performed using the nonreactive Sorescu-Rice-Thompson force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)]. These simulations, combined with those from a preceding study of shocks propagating along [100], [010], and [001] directions in nitromethane for similar conditions of temperature and shock pressure [L. He, T. D. Sewell, and D. L. Thompson, J. Chem. Phys. 134, 124506 (2011)], have been used to study the post-shock relaxation phenomena. Shocks along [010] and [101] lead to a crystal-crystal structure transformation. Shocks propagating along [011], [110], [111], [100], and [001] exhibit plane-specific disordering, which was characterized by calculating as functions of time the 1D mean square displacement (MSD), 2D radial distribution function (RDF), and 2D orientation order parameter P(2)(θ) in orthogonal planes mutually perpendicular to the shock plane; and by calculating as functions of distance behind the shock front the Cartesian components of intermolecular, intramolecular, and total kinetic energies. The 2D RDF results show that the structural disordering for shocks along [100], [110], and [111] is strongly plane-specific; whereas for shocks along [001] and [011], the loss of crystal structural order is almost equivalent in the orthogonal planes perpendicular to the shock plane. Based on the entire set of simulations, there is a trend for the most extensive disordering to occur in the (010) and (110) planes, less extensive disordering to occur in the (100) plane, and essentially no disordering to occur in the (001) plane. The 2D P(2)(θ) and 1D MSD profiles show, respectively, that the orientational and translational disordering is plane-specific, which results in the plane-specific structural disordering observed in the 2D RDF. By contrast, the kinetic energy partitioning and redistribution do not exhibit plane specificity, as shown by the similarity of spatial profiles of the Cartesian components of the intermolecular, intramolecular, and total kinetic energies in orthogonal planes perpendicular to the shock plane. © 2012 American Institute of Physics

Molecular dynamics simulations of shock waves in oriented nitromethane single crystals.

PubMed

He, Lan; Sewell, Thomas D; Thompson, Donald L

2011-03-28

The structural relaxation of crystalline nitromethane initially at T = 200 K subjected to moderate (~15 GPa) supported shocks on the (100), (010), and (001) crystal planes has been studied using microcanonical molecular dynamics with the nonreactive Sorescu-Rice-Thompson force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)]. The responses to the shocks were determined by monitoring the mass density, the intermolecular, intramolecular, and total temperatures (average kinetic energies), the partitioning of total kinetic energy among Cartesian directions, the radial distribution functions for directions perpendicular to those of shock propagation, the mean-square displacements in directions perpendicular to those of shock propagation, and the time dependence of molecular rotational relaxation as a function of time. The results show that the mechanical response of crystalline nitromethane strongly depends on the orientation of the shock wave. Shocks propagating along [100] and [001] result in translational disordering in some crystal planes but not in others, a phenomenon that we refer to as plane-specific disordering; whereas for [010] the shock-induced stresses are relieved by a complicated structural rearrangement that leads to a paracrystalline structure. The plane-specific translational disordering is more complete by the end of the simulations (~6 ps) for shock propagation along [001] than along [100]. Transient excitation of the intermolecular degrees of freedom occurs in the immediate vicinity of the shock front for all three orientations; the effect is most pronounced for the [010] shock. In all three cases excitation of molecular vibrations occurs more slowly than the intermolecular excitation. The intermolecular and intramolecular temperatures are nearly equal by the end of the simulations, with 400-500 K of net shock heating. Results for two-dimensional mean-square molecular center-of-mass displacements, calculated as a function of time since shock wave passage in planes perpendicular to the direction of shock propagation, show that the molecular translational mobility in the picoseconds following shock wave passage is greatest for [001] and least for the [010] case. In all cases the root-mean-square center-of-mass displacement is small compared to the molecular diameter of nitromethane on the time scale of the simulations. The calculated time scales for the approach to thermal equilibrium are generally consistent with the predictions of a recent theoretical analysis due to Hooper [J. Chem. Phys. 132, 014507 (2010)].

Superconducting magnetic coil

DOEpatents

Aized, D.; Schwall, R.E.

1999-06-22

A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil. 15 figs.

Stress State of the Earth's Crust in Azerbaijan

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

Agayeva, Solmaz T.

2006-03-23

The study of the crustal stress has a practical implication in hazard mitigation. Knowledge on stress-related ground motion may help to improve the stability of public and private buildings. The stress state of the crust in Azerbaijan is studied in this paper by means of focal mechanism analysis and using different methods to determine the principal stress orientations. Two types of stress states were revealed in the studied regions. The territory of Great and Lesser Caucasus and Talysh folded zone are characterized by near-horizontal compression. The territories of Caspian Sea and Kura depression are characterized by near-horizontal tension. For bothmore » types of stress state, the predominant stress axes are oriented perpendicular to the regional geological structures.« less

Microstructure of Transparent Strontium Fresnoite Glass-Ceramics

PubMed Central

Wisniewski, Wolfgang; Takano, Kazuya; Takahashi, Yoshihiro; Fujiwara, Takumi; Rüssel, Christian

2015-01-01

Glass-ceramics grown from a glass of the composition Sr2TiSi2.45O8.9 (STS 45) are analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Oriented nucleation with the c-axes preferably perpendicular to the surface is detected. A very strong 001-texture is observed after only 10 μm of growth into the bulk, making this the first system in which an orientation preferred during nucleation prevails during growth into the bulk in glass-ceramics. Piezoelectric measurements are performed and d33-values presented and discussed. The obtained results are critically viewed with respect to the two growth models describing Sr2TiSi2O8 growth in glasses. PMID:25780988

Sulphur hexaflouride: low energy (e,2e) experiments and molecular three-body distorted wave theory

NASA Astrophysics Data System (ADS)

Nixon, Kate L.; Murray, Andrew J.; Chaluvadi, H.; Ning, C. G.; Colgan, James; Madison, Don H.

2016-10-01

Experimental and theoretical triple differential ionisation cross-sections (TDCSs) are presented for the highest occupied molecular orbital of sulphur hexafluoride. These measurements were performed in the low energy regime, with outgoing electron energies ranging from 5 to 40 eV in a coplanar geometry, and with energies of 10 and 20 eV in a perpendicular geometry. Complementary theoretical predictions of the TDCS were calculated using the molecular three-body distorted wave formalism. Calculations were performed using a proper average over molecular orientations as well as the orientation-averaged molecular orbital approximation. This more sophisticated model was found to be in closer agreement with the experimental data, however neither model accurately predicts the TDCS over all geometries and energies.

Gaseous Vortices in Barred Spiral Galaxies

NASA Technical Reports Server (NTRS)

England, Martin N.; Hunter, James H., Jr.

1995-01-01

During the course of examining many two-dimensional, as well as a smaller sample of three-dimensional, models of gas flows in barred spiral galaxies, we have been impressed by the ubiquitous presence fo vortex pairs, oriented roughly perpendicular to their bars, with one vortex on each side. The vortices are obvious only when viewed in the bar frame, and the centers of their velocity fields usually are near Lagrangian points L(sub 4,5). In all models that we have studied, the vortices form on essentially the same time scale as that for the development of gaseous spiral arms, typically two bar rotations. Usually the corotation radius, r(sub c), lies slightly beyond the end of the bar. Depending upon the mass distributions of the various components, gas spirals either into, or out of, the vortices: In the former case, the vortices become regions of high density, whereas the opposite is true if the gas spirals out of a vortex. The models described in this paper have low-density vortices, as do most of the models we have studied. Moreover, usually the vortex centers lie approximately within +/- 15 deg of L(sub 4,5). In the stellar dynamic limit, when pressure and viscous forces are absent, short-period orbits exist, centered on L(sub 4,5). These orbits need not cross and therefore their morphology is that of gas streamlines, that is, vortices. We believe that the gas vortices in our models are hydrodynamic analogues of closed, short-period, libration orbits centered on L(sub 4,5).

Synergetic effect of laser patterning and micro coining for controlled lubricant propagation

NASA Astrophysics Data System (ADS)

Rosenkranz, Andreas; Gruetzmacher, Philipp G.; Szurdak, Adam; Gachot, Carsten; Hirt, Gerhard; Muecklich, Frank

2016-09-01

In this study, the anisotropic spreading behavior of Poly-(alpha)-olefin oil (kinematic viscosity of 7.8 cSt at 100 °C) on stainless steel samples (AISI 403) having periodic, channel-like structures produced by hot micro-coining (periodicity of 400 μm and depth of 40 μm) as well as multi-scale structures (coining and laser patterning) was investigated. These results were compared to the behavior of periodic channels fabricated by direct laser interference patterning (periodicity of 5 μm and depth of 1 μm). The spreading behavior of a droplet (3 μl) was studied for a polished reference as well as for all modified surfaces and recorded by a digital light microscope. From this study, it can be concluded that the polished reference leads to an isotropic spreading behavior resulting from the stochastic surface roughness without any preferential orientation whereas all structured samples induce an anisotropic spreading behavior but with different degrees of anisotropy. The observed behavior can be well correlated with pinning induced by the grooves thus hindering the droplet propagation perpendicular to the grooves and the generation of capillary forces which favor the droplet movement along the grooves. It could be proved that the structural depth is a very desicive parameter with regard to the resulting spreading behavior. The multi-scale surface combining large structural depths and the steeper pattern geometry of the micro-coined surface with much smaller grooves of the laser-structure shows the largest anisotropic spreading behavior due to a stronger pinning and increased capillary forces.

Polyaxial stress-dependent permeability of a three-dimensional fractured rock layer

NASA Astrophysics Data System (ADS)

Lei, Qinghua; Wang, Xiaoguang; Xiang, Jiansheng; Latham, John-Paul

2017-12-01

A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a "through-going" joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments.

Fantastic Striations and Where to Find Them: The Origin of Magnetically Aligned Striations in Interstellar Clouds

NASA Astrophysics Data System (ADS)

Chen, Che-Yu; Li, Zhi-Yun; King, Patrick K.; Fissel, Laura M.

2017-10-01

Thin, magnetically aligned striations of relatively moderate contrast with the background are commonly observed in both atomic and molecular clouds. They are also prominent in MHD simulations with turbulent converging shocks. The simulated striations develop within a dense, stagnated sheet in the midplane of the post-shock region where magnetically induced converging flows collide. We show analytically that the secondary flows are an inevitable consequence of the jump conditions of oblique MHD shocks. They produce the stagnated, sheet-like sub-layer through a secondary shock when, roughly speaking, the Alfvénic speed in the primary converging flows is supersonic, a condition that is relatively easy to satisfy in interstellar clouds. The dense sub-layer is naturally threaded by a strong magnetic field that lies close to the plane of the sub-layer. The substantial magnetic field makes the sheet highly anisotropic, which is the key to the striation formation. Specifically, perturbations of the primary inflow that vary spatially perpendicular to the magnetic field can easily roll up the sheet around the field lines without bending them, creating corrugations that appear as magnetically aligned striations in column density maps. On the other hand, perturbations that vary spatially along the field lines curve the sub-layer and alter its orientation relative to the magnetic field locally, seeding special locations that become slanted overdense filaments and prestellar cores through enhanced mass accumulation along field lines. In our scenario, the dense sub-layer, which is unique to magnetized oblique shocks, is the birthplace for both magnetically aligned diffuse striations and massive star-forming structures.

Unconformity-related oil entrapment in Muddy Sandstone: comparison of Kitty and Amos Draw fields, Powder River basin, Wyoming

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

Odland, S.K.; Gardner, M.H.; Gustason, E.R.

1986-08-01

It has long been known that an unconformity plays a critical role in trapping oil in the Muddy Sandstone in the Powder River basin, but opinions have varied as to exactly where in the section that unconformity is located. Their work indicates that there are, in fact, two unconformities associated with the Muddy in the northern part of the basin. The older of these occurs on top of the Skull Creek Shale, whereas the younger is largely intraformational. In places, the younger unconformity has truncated the older one. It is the younger unconformity that is responsible for creating favorable settingsmore » for stratigraphic entrapment of oil. Two types of unconformity-related oil traps result from fluvial downcutting into and through the strand-plain sandstones of the oldest member of the Muddy during a major sea level drop. In cases where the unconformity cuts through the Muddy into the underlying Skull Creek Shale, permeable valley-fill sediments, deposited during the Muddy transgression, are juxtaposed against the impermeable Skull Creek Shale along the valley walls. Where valleys are oriented roughly perpendicular to regional structure, as at Kitty field, the updip portion of the valley wall can form a permeability barrier to the fluvial reservoir sandstones of the adjacent valley fill. In cases where the unconformity is intraformational, such as at Amos Draw field, early diagenetic clay, associated with the weathered horizon directly beneath the unconformity, can create a seal on top of the strand-plain sandstones of the oldest member of the Muddy.« less

Specific cross-gender behaviour in boyhood and later homosexual orientation.

PubMed

Green, R; Roberts, C W; Williams, K; Goodman, M; Mixon, A

1987-07-01

Data from a group of males aged 13 to 23, who as children exhibited extensive cross-gender behaviour, was analysed. In boyhood they frequently played with dress-up dolls, role-played as females, dressed in girls' clothes, stated the wish to be girls, primarily had girls as friends, and avoided rough-and-tumble play. The majority of the group evolved a bisexual or homosexual orientation; two types of behaviour, boyhood doll play and female role-playing, were found to be associated with later homosexual orientation. The findings suggest developmental associations between specific types of boyhood cross-gender behaviour and the objects of later sexual arousal.

Nanofiber-Based Bulk-Heterojunction Organic Solar Cells Using Coaxial Electrospinning

DTIC Science & Technology

2012-01-01

chains are likely oriented with the [010] direction, perpendicular to the substrate, in the fi lm device. Glancing incidence X - ray diffraction (GIXD...Electron and X - ray diffraction measurements were per- formed in order to study the structural order in annealed fi bers and devices. For reference... angle X - ray scattering (SAXS/WAXS) beamline 7.3.3 of the Advanced Light Source at Lawrence Berkeley National Laboratory at 10 keV (1.24 Å) from a bend

Digital Data Acquisition for Laser Radar for Vibration Analysis

DTIC Science & Technology

1998-06-01

and the resulting signal is a function of the relative phase of the two waves , which changes as the target vibrates. The relative phase is inversely...light crosses the medium in a direction perpendicular to the acoustic waves , a modulated optical wave front will result. A standing acoustic wave in the...mean that the frequency can be up or down-shifted, depending on the orientation of the AOM, or the direction of the traveling acoustic waves . An

The One-Pot Directed Assembly of Cylinder-Forming Block Copolymer on Adjacent Chemical Patterns for Bimodal Patterning.

PubMed

Chang, Tzu-Hsuan; Xiong, Shisheng; Liu, Chi-Chun; Liu, Dong; Nealey, Paul F; Ma, Zhenqiang

2017-09-01

The direct self-assembly of cylinder-forming poly(styrene-block-methyl-methacrylate) (PS-b-PMMA) block copolymer is successfully assembled into two orientations, according to the underlying guiding pattern in different areas. Lying-down and perpendicular cylinders are formed, respectively, depending on the design of chemical pattern: sparse line/space pattern or hexagonal dot array. The first chemical pattern composed of prepatterned cross-linked polystyrene (XPS) line/space structure has a period (L S ) equal to twice the intercylinder period of the block copolymer (L 0 ). The PS-b-PMMA thin film on the prepared chemical template after thermal annealing forms a lying-down cylinder morphology when the width of the PS strips is less than the width of PS block in the PS-b-PMMA block copolymer. The morphology is only applicable at the discrete thickness of the PS-b-PMMA film. In addition to forming the lying-down cylinders directly on the XPS guiding pattern, the cylinder-forming block copolymer can also be assembled in a perpendicular way on the second guiding pattern (the hexagonal dot array). The block copolymer films are registered into two orientations in a single directed self-assembly process. The features of the assembled patterns are successfully transferred down to the silicon oxide substrate. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of c-axis perpendicularly oriented ultra-thin L10-FePt films on MgO and VN underlayers

NASA Astrophysics Data System (ADS)

Futamoto, Masaaki; Shimizu, Tomoki; Ohtake, Mitsuru

2018-05-01

Ultra-thin L10-FePt films of 2 nm average thickness are prepared on (001) oriented MgO and VN underlayers epitaxially grown on base substrate of SrTiO3(001) single crystal. Detailed cross-sectional structures are observed by high-resolution transmission electron microscopy. Continuous L10-FePt(001) thin films with very flat surface are prepared on VN(001) underlayer whereas the films prepared on MgO(001) underlayer consist of isolated L10-FePt(001) crystal islands. Presence of misfit dislocation and lattice bending in L10-FePt material is reducing the effective lattice mismatch with respect to the underlayer to be less than 0.5 %. Formation of very flat and continuous FePt layer on VN underlayer is due to the large surface energy of VN material where de-wetting of FePt material at high temperature annealing process is suppressed under a force balance between the surface and interface energies of FePt and VN materials. An employment of underlayer or substrate material with the lattice constant and the surface energy larger than those of L10-FePt is important for the preparation of very thin FePt epitaxial thin continuous film with the c-axis controlled to be perpendicular to the substrate surface.

Swi5-Sfr1 protein stimulates Rad51-mediated DNA strand exchange reaction through organization of DNA bases in the presynaptic filament

PubMed Central

Fornander, Louise H.; Renodon-Cornière, Axelle; Kuwabara, Naoyuki; Ito, Kentaro; Tsutsui, Yasuhiro; Shimizu, Toshiyuki; Iwasaki, Hiroshi; Nordén, Bengt; Takahashi, Masayuki

2014-01-01

The Swi5-Sfr1 heterodimer protein stimulates the Rad51-promoted DNA strand exchange reaction, a crucial step in homologous recombination. To clarify how this accessory protein acts on the strand exchange reaction, we have analyzed how the structure of the primary reaction intermediate, the Rad51/single-stranded DNA (ssDNA) complex filament formed in the presence of ATP, is affected by Swi5-Sfr1. Using flow linear dichroism spectroscopy, we observe that the nucleobases of the ssDNA are more perpendicularly aligned to the filament axis in the presence of Swi5-Sfr1, whereas the bases are more randomly oriented in the absence of Swi5-Sfr1. When using a modified version of the natural protein where the N-terminal part of Sfr1 is deleted, which has no affinity for DNA but maintained ability to stimulate the strand exchange reaction, we still observe the improved perpendicular DNA base orientation. This indicates that Swi5-Sfr1 exerts its activating effect through interaction with the Rad51 filament mainly and not with the DNA. We propose that the role of a coplanar alignment of nucleobases induced by Swi5-Sfr1 in the presynaptic Rad51/ssDNA complex is to facilitate the critical matching with an invading double-stranded DNA, hence stimulating the strand exchange reaction. PMID:24304898

Swi5-Sfr1 protein stimulates Rad51-mediated DNA strand exchange reaction through organization of DNA bases in the presynaptic filament.

PubMed

Fornander, Louise H; Renodon-Cornière, Axelle; Kuwabara, Naoyuki; Ito, Kentaro; Tsutsui, Yasuhiro; Shimizu, Toshiyuki; Iwasaki, Hiroshi; Nordén, Bengt; Takahashi, Masayuki

2014-02-01

The Swi5-Sfr1 heterodimer protein stimulates the Rad51-promoted DNA strand exchange reaction, a crucial step in homologous recombination. To clarify how this accessory protein acts on the strand exchange reaction, we have analyzed how the structure of the primary reaction intermediate, the Rad51/single-stranded DNA (ssDNA) complex filament formed in the presence of ATP, is affected by Swi5-Sfr1. Using flow linear dichroism spectroscopy, we observe that the nucleobases of the ssDNA are more perpendicularly aligned to the filament axis in the presence of Swi5-Sfr1, whereas the bases are more randomly oriented in the absence of Swi5-Sfr1. When using a modified version of the natural protein where the N-terminal part of Sfr1 is deleted, which has no affinity for DNA but maintained ability to stimulate the strand exchange reaction, we still observe the improved perpendicular DNA base orientation. This indicates that Swi5-Sfr1 exerts its activating effect through interaction with the Rad51 filament mainly and not with the DNA. We propose that the role of a coplanar alignment of nucleobases induced by Swi5-Sfr1 in the presynaptic Rad51/ssDNA complex is to facilitate the critical matching with an invading double-stranded DNA, hence stimulating the strand exchange reaction.

A correlative microscopy approach relates microtubule behaviour, local organ geometry, and cell growth at the Arabidopsis shoot apical meristem

PubMed Central

Burian, Agata; Uyttewaal, Magalie

2013-01-01

Cortical microtubules (CMTs) are often aligned in a particular direction in individual cells or even in groups of cells and play a central role in the definition of growth anisotropy. How the CMTs themselves are aligned is not well known, but two hypotheses have been proposed. According to the first hypothesis, CMTs align perpendicular to the maximal growth direction, and, according to the second, CMTs align parallel to the maximal stress direction. Since both hypotheses were formulated on the basis of mainly qualitative assessments, the link between CMT organization, organ geometry, and cell growth is revisited using a quantitative approach. For this purpose, CMT orientation, local curvature, and growth parameters for each cell were measured in the growing shoot apical meristem (SAM) of Arabidopsis thaliana. Using this approach, it has been shown that stable CMTs tend to be perpendicular to the direction of maximal growth in cells at the SAM periphery, but parallel in the cells at the boundary domain. When examining the local curvature of the SAM surface, no strict correlation between curvature and CMT arrangement was found, which implies that SAM geometry, and presumed geometry-derived stress distribution, is not sufficient to prescribe the CMT orientation. However, a better match between stress and CMTs was found when mechanical stress derived from differential growth was also considered. PMID:24153420

The competition between magnetocrystalline and shape anisotropy on the magnetic and magneto-transport properties of crystallographically aligned CuCr2Se4 thin films

NASA Astrophysics Data System (ADS)

Edelman, I.; Esters, M.; Johnson, D. C.; Yurkin, G.; Tarasov, A.; Rautsky, M.; Volochaev, M.; Lyashchenko, S.; Ivantsov, R.; Petrov, D.; Solovyov, L. A.

2017-12-01

Crystallographically aligned nanocrystalline films of the ferromagnetic spinel CuCr2Se4 were successfully synthesized and their structure and alignment were confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The average size of the crystallites is about 200-250 nm, and their (1 1 1) crystal planes are parallel to the film plane. A good match of the film's electronic structure to that of bulk CuCr2Se4 is confirmed by transverse Kerr effect measurements. Four easy 〈1 1 1〉 axes are present in the films. One of these axes is oriented perpendicular and three others are oriented at an angle of 19.5° relative to the film plane. The magnetic properties of the films are determined by a competition between the out-of-plane magnetocrystalline anisotropy and the in-plane shape anisotropy. Magnetic measurements show that the dominating type of anisotropy switches from shape to magnetocrystalline anisotropy near 160 K, which leads to a switch of the effective easy axis from inside the film plane at room temperature to perpendicular to the film plane as the temperature decreases. At last, a moderately large, negative value of the low-temperature magnetoresistance was observed for the first time in CuCr2Se4 films.

A correlative microscopy approach relates microtubule behaviour, local organ geometry, and cell growth at the Arabidopsis shoot apical meristem.

PubMed

Burian, Agata; Ludynia, Michal; Uyttewaal, Magalie; Traas, Jan; Boudaoud, Arezki; Hamant, Olivier; Kwiatkowska, Dorota

2013-12-01

Cortical microtubules (CMTs) are often aligned in a particular direction in individual cells or even in groups of cells and play a central role in the definition of growth anisotropy. How the CMTs themselves are aligned is not well known, but two hypotheses have been proposed. According to the first hypothesis, CMTs align perpendicular to the maximal growth direction, and, according to the second, CMTs align parallel to the maximal stress direction. Since both hypotheses were formulated on the basis of mainly qualitative assessments, the link between CMT organization, organ geometry, and cell growth is revisited using a quantitative approach. For this purpose, CMT orientation, local curvature, and growth parameters for each cell were measured in the growing shoot apical meristem (SAM) of Arabidopsis thaliana. Using this approach, it has been shown that stable CMTs tend to be perpendicular to the direction of maximal growth in cells at the SAM periphery, but parallel in the cells at the boundary domain. When examining the local curvature of the SAM surface, no strict correlation between curvature and CMT arrangement was found, which implies that SAM geometry, and presumed geometry-derived stress distribution, is not sufficient to prescribe the CMT orientation. However, a better match between stress and CMTs was found when mechanical stress derived from differential growth was also considered.

Strength and Anisotropy in Tournemire Shale: Temperature, Pressure and Time Dependences

NASA Astrophysics Data System (ADS)

Bonnelye, A.; Schubnel, A.; Zhi, G.; David, C.; Dick, P.

2017-12-01

Time and temperature dependent rock deformation has both scientific and socio-economic implications for natural hazards, the oil and gas industry and nuclear waste disposal. During the past decades, most studies on brittle creep have focused on igneous rocks and porous sedimentary rocks. To our knowledge, only few studies have been carried out on the brittle creep behavior of shale. We conducted a series of creep experiments on shale specimens coming from the French Institute for Nuclear Safety (IRSN) underground research laboratory located in Tournemire, France, under two different temperatures (26°C, 75°C) and confining pressures (10 MPa, 80 MPa), for three orientations (σ1along, perpendicular and 45° to bedding). In these long-term experiments (approximately 10 days), stress and strains were recorded continuously, while ultrasonic acoustic velocities were recorded every 1 15 minutes. The brittle creep failure stress of our Tournemire shale samples was systematically observed 50% higher than its short-term peak strength, with larger final axial strain accumulated. During creep, ultrasonic wave velocities first decreased, and then increased gradually. The magnitude of elastic wave velocity variations showed an important orientation and temperature dependence: velocities measured perpendicular to bedding showed increased variation, variation that was enhanced at higher temperature and higher pressure. The case of complete elastic anisotropy reversal was observed for sample deformed perpendicular to bedding, with amount of axial strain needed to reach anisotropy reversal reduced at higher temperature. SEM observations highlight the competition between crack growth, sealing/healing, and possibly mineral rotation, pressure solution or anisotropic compaction during creep defromation. Our study highlights that the short-term peak strength has little meaning in shale material, which can over-consolidate importantly by `plastic' flow. In addition, we show that elastic anisotropy can switch and even reverse over relatively short time periods (<10 days) and for relatively small amount of plastic deformation (<5%).

Varying Degrees of Nonlinear Mechanical Behavior Arising From Geometric Differences of Urogynecological Meshes

PubMed Central

Feola, Andrew; Pal, Siladitya; Moalli, Pamela; Maiti, Spandan; Abramowitch, Steven

2014-01-01

Synthetic polypropylene meshes were designed to restore pelvic organ support for women suffering from pelvic organ prolapse; however, the FDA released two notifications regarding the potential complications associated with mesh implantation. Our aim was to characterize the structural properties of Restorelle and UltraPro subjected to uniaxial tension along perpendicular directions, and then model the tensile behavior of these meshes utilizing a co-rotational finite element model, with an imbedded linear or fiber-recruitment local stress-strain relationship. Both meshes exhibited highly nonlinear stress-strain behavior; Restorelle had no significant differences between the two perpendicular directions, while UltraPro had a 93% difference in the low (initial) stiffness (p=0.009) between loading directions. Our model predicted that early alignment of the mesh segments in the loading direction and subsequent stretching could explain the observed nonlinear tensile behavior. However, a nonlinear stress-strain response in the stretching regime, that may be inherent to the mesh segment, was required to better capture experimental results. Utilizing a nonlinear fiber recruitment model with two parameters A and B, we observed improved agreement between the simulations and the experimental results. An inverse analysis found A=120 MPa and B=1.75 for Restorelle (RMSE=0.36). This approach yielded A=30 MPa and B=3.5 for UltraPro along one direction (RMSE=0.652), while the perpendicular orientation resulted in A=130 MPa and B=4.75 (RMSE=4.36). From the uniaxial protocol, Restorelle was found to have little variance in structural properties along these two perpendicular directions; however, UltraPro was found to behave anisotropically. PMID:25011619

Impact of the MLC on the MRI field distortion of a prototype MRI-linac

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

Kolling, Stefan; Keall, Paul; Oborn, Brad

2013-12-15

Purpose: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality.Methods: The finite element method was employed to model a MRI-linac assembly comprised of a 1.0 T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps ofmore » the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30 cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300 μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200 cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20 cm{sup 2}, to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B{sub 0} of 0.5, 1.0, and 1.5 T, to estimate how the MLC impact changes with B{sub 0}.Results: (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field distortion was generally smaller in the perpendicular beam orientation. The peak-to-peak DSV distortion was below 300 μT at SID≥130 cm (perpendicular) and SID≥140 cm (inline) for the 1.0 T design. (4) The simulation of different treatment fields was identified to cause dynamic changes in the field distribution. However, the estimated residual distortion was below 1.2 mm geometric distortion at SID≥120 cm (perpendicular) and SID≥130 cm (inline) for a 10 mT/m frequency-encoding gradient. (5) Due to magnetic saturation of the MLC materials, the field distortion remained constant at B{sub 0}>1.0 T.Conclusions: This work shows that the MRI field distortions caused by the MLC cannot be ignored and must be thoroughly investigated for any MRI-linac system. The numeric distortion values obtained for our 1.0 T magnet may vary for other magnet designs with substantially different fringe fields, however the concept of modest increases in the SID to reduce the distortion to a shimmable level is generally applicable.« less

X-Z-Theta cutting method

DOEpatents

Bieg, Lothar F.

1993-01-12

A method for machining a workpiece. The method includes the use of a rotary cutting tool mounted on the end of a movable arm. The arm is adapted to move in a plane perpendicular to the axis of rotation of the cutting tool. The cutting tool has cutting teeth to cut chips of material off of the workpiece in a predetermined size and shape to facilitate better removal of the chips from the workpiece. The teeth can be of different type and length to permit the tool to both rough cut and finish cut the workpiece during machining. The total depth of cut is divided by the number of tool teeth, so that the longest tool always performs the finishing cut.

Methods to induce perpendicular magnetic anisotropy in full-Heusler Co2FeSi thin layers in a magnetic tunnel junction structure

NASA Astrophysics Data System (ADS)

Shinohara, Koki; Suzuki, Takahiro; Takamura, Yota; Nakagawa, Shigeki

2018-05-01

In this study, to obtain perpendicular magnetic tunnel junctions (p-MTJs) using half-metallic ferromagnets (HMFs), several methods were developed to induce perpendicular magnetic anisotropy (PMA) in full-Heusler Co2FeSi (CFS) alloy thin layers in an MTJ multilayer composed of a layered CFS/MgO/CFS structure. Oxygen exposure at 2.0 Pa for 10 min after deposition of the bottom CFS layer was effective for obtaining PMA in the CFS layer. One of the reasons for the PMA is the formation of nearly ideal CFS/MgO interfaces due to oxygen exposure before the deposition of the MgO layer. The annealing process was effective for obtaining PMA in the top CFS layer capped with a Pd layer. PMA was clearly observed in the top CFS layer of a Cr(40 nm)/Pd(50 nm)/bottom CFS(0.6 nm)/MgO(2.0 nm)/top CFS(0.6 nm)/ Pd(10 nm) multilayer, where the top CFS and Pd thin films were deposited at RT and subsequently annealed at 300°C. In addition to the continuous layer growth of the films, the crystalline orientation alignment at the top CFS/Pd interface probably attributes to the origin of PMA at the top CFS layer.

Microwave frequency tuning in heterogeneous spin torque oscillator with perpendicular polarizer: A macrospin study

NASA Astrophysics Data System (ADS)

Bhoomeeswaran, H.; Vivek, T.; Sabareesan, P.

2018-04-01

In this article, we have theoretically devised a Spin Torque Nano Oscillator (STNO) with perpendicular polarizer using macro spin model. The devised spin valve structure is heterogeneous (i.e.) it is made of two different ferromagnetic materials [Co and its alloy CoFeB]. The dynamics of magnetization provoked by spin transfer torque is studied numerically by solving the famous Landau-Lifshitz-Gilbert-Slonczewski [LLGS] equation. The results are obtained for the perpendicular polarizer and for that particular out of plane orientation we vary the free layer angle from 10° to 90°. The obtained results are highly appealing, because frequency range is available in all the tilt angles of free layer and it is exceptionally tunable in all free layer tilt angles with zero applied field. Moreover, the utmost operating frequency of about 83.3 GHz and its corresponding power of 4.488 µW/mA2/GHz is acquired for the free layer tilt angle θ = 90° with the solid applied current density of 10 × 1010 A/m2. Also, our device emits high quality factor of about 396, which is remarkably desirable for making devices. These pioneering results provides a significant development for future spintronic based devices.

Size and Shape of the Distant Magnetotail

NASA Technical Reports Server (NTRS)

Sibeck, D.G.; Lin, R.-Q.

2014-01-01

We employ a global magnetohydrodynamic model to study the effects of the interplanetary magnetic field (IMF) strength and direction upon the cross-section of the magnetotail at lunar distances. The anisotropic pressure of draped magnetosheath magnetic field lines and the inclusion of a reconnection-generated standing slow mode wave fan bounded by a rotational discontinuity within the definition of the magnetotail result in cross-sections elongated in the direction parallel to the component of the IMF in the plane perpendicular to the Sun-Earth line. Tilted cross-tail plasma sheets separate the northern and southern lobes within these cross-sections. Greater fast mode speeds perpendicular than parallel to the draped magnetos heath magnetic field lines result in greater distances to the bow shock in the direction perpendicular than parallel to the component of the IMF in the plane transverse to the Sun-Earth line. The magnetotail cross-section responds rapidly to reconnected magnetic field lines requires no more than the magnetosheath convection time to appear at any distance downstream, and further adjustments of the cross-section in response to the anisotropic pressures of the draped magnetic field lines require no more than 10-20 minutes. Consequently for typical ecliptic IMF orientations and strengths, the magnetotail cross-section is oblate while the bow shock is prolate.

Near-infrared integral field spectroscopy of massive young stellar objects

NASA Astrophysics Data System (ADS)

Murakawa, K.; Lumsden, S. L.; Oudmaijer, R. D.; Davies, B.; Wheelwright, H. E.; Hoare, M. G.; Ilee, J. D.

2013-11-01

We present medium-resolution (R ≈ 5300) K-band integral field spectroscopy of six massive young stellar objects (MYSOs). The targets are selected from the Red MSX Source (RMS) survey, and we used the ALTAIR adaptive optics assisted Near-Infrared Integral Field Spectrometer (NIFS) mounted on the Gemini North telescope. The data show various spectral line features including Brγ, CO, H2 and He I. The Brγ line is detected in emission in all objects with vFWHM ˜ 100-200 km s-1. V645 Cyg shows a high-velocity P-Cygni profile between -800 and -300 km s-1. We performed three-dimensional spectroastrometry to diagnose the circumstellar environment in the vicinity of the central stars using the Brγ line. We measured the centroids of the velocity components with sub-mas precision. The centroids allow us to discriminate the blueshifted and redshifted components in a roughly east-west direction in both IRAS 18151-1208 and S106 in Brγ. This lies almost perpendicular to observed larger scale outflows. We conclude, given the widths of the lines and the orientation of the spectroastrometric signature, that our results trace a disc wind in both IRAS 18151-1208 and S106. The CO ν = 2-0 absorption lines at low J transitions are detected in IRAS 18151-1208 and AFGL 2136. We analysed the velocity structure of the neutral gas discs, which we find to have nearly Keplerian motions. In IRAS 18151-1208, the absorption centroids of the blueshifted and redshifted components are separated in a direction of north-east to south-west, nearly perpendicular to that of the larger scale H2 jet. The position-velocity relations of these objects can be reproduced with central masses of 30 M⊙ for IRAS 18151-1208 and 20 M⊙ for AFGL 2136. We also detect CO ν = 2-0 bandhead emission in IRAS 18151-1208, S106 and V645 Cyg. The results can be fitted reasonably with a Keplerian rotation model, with masses of 15, 20 and 20 M⊙, respectively. These results for a sample of MYSOs can be explained with disc and outflow models and support the hypothesis of massive star formation via mass accretion through discs as is the case for lower mass counterparts.

Emergent scar lines in chaotic advection of passive directors

NASA Astrophysics Data System (ADS)

Hejazi, Bardia; Mehlig, Bernhard; Voth, Greg A.

2017-12-01

We examine the spatial field of orientations of slender fibers that are advected by a two-dimensional fluid flow. The orientation field of these passive directors are important in a wide range of industrial and geophysical flows. We introduce emergent scar lines as the dominant coherent structures in the orientation field of passive directors in chaotic flows. Previous work has identified the existence of scar lines where the orientation rotates by π over short distances, but the lines that were identified disappeared as time progressed. As a result, earlier work focused on topological singularities in the orientation field, which we find to play a negligible role at long times. We use the standard map as a simple time-periodic two-dimensional flow that produces Lagrangian chaos. This class of flows produces persistent patterns in passive scalar advection and we find that a different kind of persistent pattern develops in the passive director orientation field. We identify the mechanism by which emergent scar lines grow to dominate these patterns at long times in complex flows. Emergent scar lines form where the recent stretching of the fluid element is perpendicular to earlier stretching. Thus these scar lines can be labeled by their age, defined as the time since their stretching reached a maximum.

A bio-inspired microstructure induced by slow injection moulding of cylindrical block copolymers.

PubMed

Stasiak, Joanna; Brubert, Jacob; Serrani, Marta; Nair, Sukumaran; de Gaetano, Francesco; Costantino, Maria Laura; Moggridge, Geoff D

2014-08-28

It is well known that block copolymers with cylindrical morphology show alignment with shear, resulting in anisotropic mechanical properties. Here we show that well-ordered bi-directional orientation can be achieved in such materials by slow injection moulding. This results in a microstructure, and anisotropic mechanical properties, similar to many natural tissues, making this method attractive for engineering prosthetic fibrous tissues. An application of particular interest to us is prosthetic polymeric heart valve leaflets, mimicking the shape, microstructure and hence performance of the native valve. Anisotropic layers have been observed for cylinder-forming block copolymers centrally injected into thin circular discs. The skin layers exhibit orientation parallel to the flow direction, whilst the core layer shows perpendicularly oriented domains; the balance of skin to core layers can be controlled by processing parameters such as temperature and injection rate. Heart valve leaflets with a similar layered structure have been prepared by injection moulding. Numerical modelling demonstrates that such complex orientation can be explained and predicted by the balance of shear and extensional flow.

Model-based analysis of multi-shell diffusion MR data for tractography: How to get over fitting problems

PubMed Central

Jbabdi, Saad; Sotiropoulos, Stamatios N; Savio, Alexander M; Graña, Manuel; Behrens, Timothy EJ

2012-01-01

In this article, we highlight an issue that arises when using multiple b-values in a model-based analysis of diffusion MR data for tractography. The non-mono-exponential decay, commonly observed in experimental data, is shown to induce over-fitting in the distribution of fibre orientations when not considered in the model. Extra fibre orientations perpendicular to the main orientation arise to compensate for the slower apparent signal decay at higher b-values. We propose a simple extension to the ball and stick model based on a continuous Gamma distribution of diffusivities, which significantly improves the fitting and reduces the over-fitting. Using in-vivo experimental data, we show that this model outperforms a simpler, noise floor model, especially at the interfaces between brain tissues, suggesting that partial volume effects are a major cause of the observed non-mono-exponential decay. This model may be helpful for future data acquisition strategies that may attempt to combine multiple shells to improve estimates of fibre orientations in white matter and near the cortex. PMID:22334356

Parameter selection with the Hotelling observer in linear iterative image reconstruction for breast tomosynthesis

NASA Astrophysics Data System (ADS)

Rose, Sean D.; Roth, Jacob; Zimmerman, Cole; Reiser, Ingrid; Sidky, Emil Y.; Pan, Xiaochuan

2018-03-01

In this work we investigate an efficient implementation of a region-of-interest (ROI) based Hotelling observer (HO) in the context of parameter optimization for detection of a rod signal at two orientations in linear iterative image reconstruction for DBT. Our preliminary results suggest that ROI-HO performance trends may be efficiently estimated by modeling only the 2D plane perpendicular to the detector and containing the X-ray source trajectory. In addition, the ROI-HO is seen to exhibit orientation dependent trends in detectability as a function of the regularization strength employed in reconstruction. To further investigate the ROI-HO performance in larger 3D system models, we present and validate an iterative methodology for calculating the ROI-HO. Lastly, we present a real data study investigating the correspondence between ROI-HO performance trends and signal conspicuity. Conspicuity of signals in real data reconstructions is seen to track well with trends in ROI-HO detectability. In particular, we observe orientation dependent conspicuity matching the orientation dependent detectability of the ROI-HO.

Orthogonally superimposed laser-induced periodic surface structures (LIPSS) upon nanosecond laser pulse irradiation of SiO2/Si layered systems

NASA Astrophysics Data System (ADS)

Nürnberger, Philipp; Reinhardt, Hendrik M.; Kim, Hee-Cheol; Pfeifer, Erik; Kroll, Moritz; Müller, Sandra; Yang, Fang; Hampp, Norbert A.

2017-12-01

In this study we examined the formation of laser-induced periodic surface structures (LIPSS) on silicon (Si) in dependence on the thickness of silicon-dioxide (SiO2) on top. LIPSS were generated in air by linearly polarized ≈8 nanosecond laser pulses with a fluence per pulse of 2.41 J cm-2 at a repetition rate of 100 kHz. For SiO2 layers <80 nm, LIPSS oriented perpendicular to the laser polarization were obtained, but for SiO2 layers >120 nm parallel oriented LIPSS were observed. In both cases the periodicity was about 80-90% of the applied laser wavelength (λ0 = 532 nm). By variation of the SiO2 layer thickness in the range between 80 nm-120 nm, the dominating orientation changes. Even orthogonally superimposed LIPSS with a periodicity of only 60% of the laser wavelength were found. We show that the transition of the orientation direction of LIPSS is related to the penetration depth of surface plasmon polariton (SPP) fields into the oxide layer.

New Algorithm Identifies Tidal Streams Oriented Along our Line-of-Sight

NASA Astrophysics Data System (ADS)

Lin, Ziyi; Newberg, Heidi; Amy, Paul; Martin, Charles Harold; Rockcliffe, Keighley E.

2018-01-01

The known dwarf galaxy tidal streams in the Milky Way are primarily oriented perpendicular to our line-of-sight. That is because they are concentrated into an observable higher-surface-brightness feature at a particular distance, or because they tightly cluster in line-of-sight velocity in a particular direction. Streams that are oriented along our line-of-sight are spread over a large range of distances and velocities. However, these distances and velocities are correlated in predicable ways. We used a set of randomly oriented Milky Way orbits to develop a technique that bins stars in combinations of distance and velocity that are likely for tidal streams. We applied this technique to identify previously unknown tidal streams in a set of blue horizontal branch stars in the first quadrant from Data Release 10 of the Sloan Digital Sky Survey (SDSS). This project was supported by NSF grant AST 16-15688, a Rensselaer Presidential Fellowship, the NASA/NY Space Grant fellowship, and contributions made by The Marvin Clan, Babette Josephs, Manit Limlamai, and the 2015 Crowd Funding Campaign to Support Milky Way Research.

Examination of Surface Roughness on Light Scattering by Long Ice Columns by Use of a Two-Dimensional Finite-Difference Time-Domain Algorithm

NASA Technical Reports Server (NTRS)

Sun, W.; Loeb, N. G.; Videen, G.; Fu, Q.

2004-01-01

Natural particles such as ice crystals in cirrus clouds generally are not pristine but have additional micro-roughness on their surfaces. A two-dimensional finite-difference time-domain (FDTD) program with a perfectly matched layer absorbing boundary condition is developed to calculate the effect of surface roughness on light scattering by long ice columns. When we use a spatial cell size of 1/120 incident wavelength for ice circular cylinders with size parameters of 6 and 24 at wavelengths of 0.55 and 10.8 mum, respectively, the errors in the FDTD results in the extinction, scattering, and absorption efficiencies are smaller than similar to 0.5%. The errors in the FDTD results in the asymmetry factor are smaller than similar to 0.05%. The errors in the FDTD results in the phase-matrix elements are smaller than similar to 5%. By adding a pseudorandom change as great as 10% of the radius of a cylinder, we calculate the scattering properties of randomly oriented rough-surfaced ice columns. We conclude that, although the effect of small surface roughness on light scattering is negligible, the scattering phase-matrix elements change significantly for particles with large surface roughness. The roughness on the particle surface can make the conventional phase function smooth. The most significant effect of the surface roughness is the decay of polarization of the scattered light.

Experimental and density functional theoretical investigations of linkage isomerism in six-coordinate FeNO(6) iron porphyrins with axial nitrosyl and nitro ligands.

PubMed

Novozhilova, Irina V; Coppens, Philip; Lee, Jonghyuk; Richter-Addo, George B; Bagley, Kimberly A

2006-02-15

A critical component of the biological activity of NO and nitrite involves their coordination to the iron center in heme proteins. Irradiation (330 < lambda < 500 nm) of the nitrosyl-nitro compound (TPP)Fe(NO)(NO(2)) (TPP = tetraphenylporphyrinato dianion) at 11 K results in changes in the IR spectrum associated with both nitro-to-nitrito and nitrosyl-to-isonitrosyl linkage isomerism. Only the nitro-to-nitrito linkage isomer is obtained at 200 K, indicating that the isonitrosyl linkage isomer is less stable than the nitrito linkage isomer. DFT calculations reveal two ground-state conformations of (porphine)Fe(NO)(NO(2)) that differ in the relative axial ligand orientations (i.e., GS parallel and GS perpendicular). In both conformations, the FeNO group is bent (156.4 degrees for GS parallel, 159.8 degrees for GS perpendicular) for this formally {FeNO}(6) compound. Three conformations of the nitrosyl-nitrito isomer (porphine)Fe(NO)(ONO) (MSa parallel, MSa perpendicular, and MSa(L)) and two conformations of the isonitrosyl-nitro isomer (porphine)Fe(ON)(NO(2)) (MSb parallel and MSb perpendicular) are identified, as are three conformations of the double-linkage isomer (porphine)Fe(ON)(ONO) (MSc parallel, MSc perpendicular, MSc(L)). Only 2 of the 10 optimized geometries contain near-linear FeNO (MSa(L)) and FeON (MSc(L)) bonds. The energies of the ground-state and isomeric structures increase in the order GS < MSa < MSb < MSc. Vibrational frequencies for all of the linkage isomers have been calculated, and the theoretical gas-phase absorption spectrum of (porphine)Fe(NO)(NO(2)) has been analyzed to obtain information on the electronic transitions responsible for the linkage isomerization. Comparison of the experimental and theoretical IR spectra does not provide evidence for the existence of a double linkage isomer of (TPP)Fe(NO)(NO(2)).

Surface roughness estimation of MBE grown CdTe/GaAs(211)B by ex-situ spectroscopic ellipsometry

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

Karakaya, Merve, E-mail: mervegunnar@iyte.edu.tr; Bilgilisoy, Elif; Arı, Ozan

Spectroscopic ellipsometry (SE) ranging from 1.24 eV to 5.05 eV is used to obtain the film thickness and optical properties of high index (211) CdTe films. A three-layer optical model (oxide/CdTe/GaAs) was chosen for the ex-situ ellipsometric data analysis. Surface roughness cannot be determined by the optical model if oxide is included. We show that roughness can be accurately estimated, without any optical model, by utilizing the correlation between SE data (namely the imaginary part of the dielectric function, or phase angle, ψ) and atomic force microscopy (AFM) roughness. and ψ values at 3.31 eV, which corresponds to E{sub 1}more » critical transition energy of CdTe band structure, are chosen for the correlation since E{sub 1} gives higher resolution than the other critical transition energies. On the other hand, due to the anisotropic characteristic of (211) oriented CdTe surfaces, SE data ( and ψ) shows varieties for different azimuthal angle measurements. For this reason, in order to estimate the surface roughness by considering these correlations, it is shown that SE measurements need to be taken at the same surface azimuthal angle. Estimating surface roughness in this manner is an accurate way to eliminate cumbersome surface roughness measurement by AFM.« less

Some Insights on Roughness Induced Transition and Control from DNS and Experiments

NASA Astrophysics Data System (ADS)

Suryanarayanan, Saikishan; Ibitayo, Ifeoluwa; Goldstein, David; Brown, Garry

2016-11-01

We study the receptivity and subsequent evolution of an initially laminar flat boundary layer on a flat plate to single and multiple discrete roughness elements (DRE) using a combination of immersed boundary DNS and water channel flow visualization experiments. We examine the transition caused by a single DRE and demonstrate the possibility of suppressing it by an appropriately designed second DRE in both DNS and experiments. The different phases of transition are identified and the roles of Reynolds numbers based on roughness height and boundary layer thickness are investigated. The underlying mechanisms in the observed transition and its control are understood by examining detailed vorticity flux balances. Connections are also made to recent developments in transient growth and streak instability. A unified picture is sought from a parametric study of different DRE dimensions and orientations. The potential applicability of the observations and understanding derived from this study to controlling transition caused by design and environmental roughness over aircraft wings is discussed. Supported by AFOSR # FA9550-15-1-0345.

Effects of surface topography on magnetization reversal of magnetic thin films.

PubMed

Girgis, E; Pogossian, S P; Benkhedar, M L

2006-04-01

The influence of the created surface roughness on the coercivity of magnetic thin films has been investigated. The magnetic thin films (CoFe and alternatively NiFe) are sputtered on top of smooth substrates that were previously covered with an array of considerably rougher lines with one of these materials Pt, Cu, CoFe, and NiFe. The lines have been patterned using optical lithography into arrays that are deposited with different thicknesses varying between 5 nm-15 nm. The lines have been designed to have a very rough edge and seated in two different angles relative to the wafer edge (zero and 45 degrees). Magneto-optic Kerr effect (MOKE) measurements showed two distinct switching fields in the hysteresis loops that are due to magnetic domain wall trapping created by the surface roughness. The magnetization reversal showed a strong dependence on the height, the orientation angle, and the material's type of the created surface roughness (the lines).

Rapid assessment of crystal orientation in semi-crystalline polymer films using rotational zone annealing and impact of orientation on mechanical properties

DOE PAGES

Ye, Changhuai; Wang, Chao; Wang, Jing; ...

2017-08-17

Crystal orientation in semi-crystalline polymers tends to enhance their performance, such as increased yield strength and modulus, along the orientation direction. Zone annealing (ZA) orients the crystal lamellae through a sharp temperature gradient that effectively directs the crystal growth, but the sweep rate (V ZA) of this gradient significantly impacts the extent of crystal orientation. Here in this work, we demonstrate rotational zone annealing (RZA) as an efficient method to elucidate the influence of V ZA on the crystal morphology of thin films in a single experiment using isotactic poly(1-butene), PB-1, as a model semi-crystalline polymer. These RZA results aremore » confirmed using standard, serial linear ZA to tune the structure from an almost unidirectional oriented morphology to weakly oriented spherulites. The overall crystallinity is only modestly changed in comparison to isothermal crystallization (maximum of 55% from ZA vs. 48% for isothermal crystallization). However, the average grain size increases and the spherulites become anisotropic from ZA. Due to these structural changes, the Young's modulus of the oriented films, both parallel and perpendicular to the spherulite orientation direction, is significantly increased by ZA. The modulus does become anisotropic after ZA due to the directionality in the crystal structure, with more than a threefold increase in the modulus parallel to the orientation direction for the highest oriented film in comparison to the modulus from isothermal crystallization. Lastly, RZA enables rapid identification of conditions to maximize orientation of crystals in thin polymer films, which could find utility in determining conditions to improve crystallinity and performance in organic electronics.« less

Rapid assessment of crystal orientation in semi-crystalline polymer films using rotational zone annealing and impact of orientation on mechanical properties

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

Ye, Changhuai; Wang, Chao; Wang, Jing

Crystal orientation in semi-crystalline polymers tends to enhance their performance, such as increased yield strength and modulus, along the orientation direction. Zone annealing (ZA) orients the crystal lamellae through a sharp temperature gradient that effectively directs the crystal growth, but the sweep rate (V ZA) of this gradient significantly impacts the extent of crystal orientation. Here in this work, we demonstrate rotational zone annealing (RZA) as an efficient method to elucidate the influence of V ZA on the crystal morphology of thin films in a single experiment using isotactic poly(1-butene), PB-1, as a model semi-crystalline polymer. These RZA results aremore » confirmed using standard, serial linear ZA to tune the structure from an almost unidirectional oriented morphology to weakly oriented spherulites. The overall crystallinity is only modestly changed in comparison to isothermal crystallization (maximum of 55% from ZA vs. 48% for isothermal crystallization). However, the average grain size increases and the spherulites become anisotropic from ZA. Due to these structural changes, the Young's modulus of the oriented films, both parallel and perpendicular to the spherulite orientation direction, is significantly increased by ZA. The modulus does become anisotropic after ZA due to the directionality in the crystal structure, with more than a threefold increase in the modulus parallel to the orientation direction for the highest oriented film in comparison to the modulus from isothermal crystallization. Lastly, RZA enables rapid identification of conditions to maximize orientation of crystals in thin polymer films, which could find utility in determining conditions to improve crystallinity and performance in organic electronics.« less

Measurement of the orientation of buffer-gas-cooled, electrostatically-guided ammonia molecules

NASA Astrophysics Data System (ADS)

Steer, Edward W.; Petralia, Lorenzo S.; Western, Colin M.; Heazlewood, Brianna R.; Softley, Timothy P.

2017-02-01

The extent to which the spatial orientation of internally and translationally cold ammonia molecules can be controlled as molecules pass out of a quadrupole guide and through different electric field regions is examined. Ammonia molecules are collisionally cooled in a buffer gas cell, and are subsequently guided by a three-bend electrostatic quadrupole into a detection chamber. The orientation of ammonia molecules is probed using (2 + 1) resonance-enhanced multiphoton ionisation (REMPI), with the laser polarisation axis aligned both parallel and perpendicular to the time-of-flight axis. Even with the presence of a near-zero field region, the ammonia REMPI spectra indicate some retention of orientation. Monte Carlo simulations propagating the time-dependent Schrödinger equation in a full basis set including the hyperfine interaction enable the orientation of ammonia molecules to be calculated - with respect to both the local field direction and a space-fixed axis - as the molecules pass through different electric field regions. The simulations indicate that the orientation of ∼95% of ammonia molecules in JK =11 could be achieved with the application of a small bias voltage (17 V) to the mesh separating the quadrupole and detection regions. Following the recent combination of the buffer gas cell and quadrupole guide apparatus with a linear Paul ion trap, this result could enable one to examine the influence of molecular orientation on ion-molecule reaction dynamics and kinetics.

Orientation selective deep brain stimulation

NASA Astrophysics Data System (ADS)

Lehto, Lauri J.; Slopsema, Julia P.; Johnson, Matthew D.; Shatillo, Artem; Teplitzky, Benjamin A.; Utecht, Lynn; Adriany, Gregor; Mangia, Silvia; Sierra, Alejandra; Low, Walter C.; Gröhn, Olli; Michaeli, Shalom

2017-02-01

Objective. Target selectivity of deep brain stimulation (DBS) therapy is critical, as the precise locus and pattern of the stimulation dictates the degree to which desired treatment responses are achieved and adverse side effects are avoided. There is a clear clinical need to improve DBS technology beyond currently available stimulation steering and shaping approaches. We introduce orientation selective neural stimulation as a concept to increase the specificity of target selection in DBS. Approach. This concept, which involves orienting the electric field along an axonal pathway, was tested in the corpus callosum of the rat brain by freely controlling the direction of the electric field on a plane using a three-electrode bundle, and monitoring the response of the neurons using functional magnetic resonance imaging (fMRI). Computational models were developed to further analyze axonal excitability for varied electric field orientation. Main results. Our results demonstrated that the strongest fMRI response was observed when the electric field was oriented parallel to the axons, while almost no response was detected with the perpendicular orientation of the electric field relative to the primary fiber tract. These results were confirmed by computational models of the experimental paradigm quantifying the activation of radially distributed axons while varying the primary direction of the electric field. Significance. The described strategies identify a new course for selective neuromodulation paradigms in DBS based on axonal fiber orientation.

Effects of fracture surface roughness and shear displacement on geometrical and hydraulic properties of three-dimensional crossed rock fracture models

NASA Astrophysics Data System (ADS)

Huang, Na; Liu, Richeng; Jiang, Yujing; Li, Bo; Yu, Liyuan

2018-03-01

While shear-flow behavior through fractured media has been so far studied at single fracture scale, a numerical analysis of the shear effect on the hydraulic response of 3D crossed fracture model is presented. The analysis was based on a series of crossed fracture models, in which the effects of fracture surface roughness and shear displacement were considered. The rough fracture surfaces were generated using the modified successive random additions (SRA) algorithm. The shear displacement was applied on one fracture, and at the same time another fracture shifted along with the upper and lower surfaces of the sheared fracture. The simulation results reveal the development and variation of preferential flow paths through the model during the shear, accompanied by the change of the flow rate ratios between two flow planes at the outlet boundary. The average contact area accounts for approximately 5-27% of the fracture planes during shear, but the actual calculated flow area is about 38-55% of the fracture planes, which is much smaller than the noncontact area. The equivalent permeability will either increase or decrease as shear displacement increases from 0 to 4 mm, depending on the aperture distribution of intersection part between two fractures. When the shear displacement continuously increases by up to 20 mm, the equivalent permeability increases sharply first, and then keeps increasing with a lower gradient. The equivalent permeability of rough fractured model is about 26-80% of that calculated from the parallel plate model, and the equivalent permeability in the direction perpendicular to shear direction is approximately 1.31-3.67 times larger than that in the direction parallel to shear direction. These results can provide a fundamental understanding of fluid flow through crossed fracture model under shear.

Investigating Architectural Issues in Neuromorphic Computing

DTIC Science & Technology

2009-06-01

An example of this is Diffusion Tensor Imaging ( DTI ), a variant of fMRI, which detects water diffusion. DTI is routinely applied at medical...model computed for a subfield positioned over a section of the silhouette dog’s hind leg . The illustrated angles roughly correspond to orientation

Radiative transfer theory for active remote sensing of a forested canopy

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.

1989-01-01

A canopy is modeled as a two-layer medium above a rough interface. The upper layer stands for the forest crown, with the leaves modeled as randomly oriented and distributed disks and needles and the branches modeled as randomly oriented finite dielectric cylinders. The lower layer contains the tree trunks, modeled as randomly positioned vertical cylinders above the rough soil. Radiative-transfer theory is applied to calculate EM scattering from such a canopy, is expressed in terms of the scattering-amplitude tensors (SATs). For leaves, the generalized Rayleigh-Gans approximation is applied, whereas the branch and trunk SATs are obtained by estimating the inner field by fields inside a similar cylinder of infinite length. The Kirchhoff method is used to calculate the soil SAT. For a plane wave exciting the canopy, the radiative-transfer equations are solved by iteration to the first order in albedo of the leaves and the branches. Numerical results are illustrated as a function of the incidence angle.

Tornadogensis within Hurricanes Based on the Orientation of the Rainband to the Coast after Landfall

NASA Astrophysics Data System (ADS)

Etten-Bohm, M.

2015-12-01

The focus of this study is to investigate the development of tornadoes within the rainband of a hurricane for various orientations of the rainband when a hurricane makes landfall. The rainband of a hurricane is a common area where tornadogenesis is found depending on the size, intensity, and orientation of the rain band when the storm makes landfall. As a hurricane approaches a coast line, land-surface roughness contributes to surface friction, which can contribute in tornadogenesis. The orientation of the rainband may play a part in the type of supercells that are formed in that rainband and the number and intensity of the tornadoes produced. This study will investigate if the orientation of the rainband leads to the direction in which the supercells rotate, whether clockwise or counter-clockwise, and the scale and intensity of the tornadoes produced.

Vertically aligned carbon nanofibers as sacrificial templates for nanofluidic structures

NASA Astrophysics Data System (ADS)

Melechko, A. V.; McKnight, T. E.; Guillorn, M. A.; Merkulov, V. I.; Ilic, B.; Doktycz, M. J.; Lowndes, D. H.; Simpson, M. L.

2003-02-01

We report a method to fabricate nanoscale pipes ("nanopipes") suitable for fluidic transport. Vertically aligned carbon nanofibers grown by plasma-enhanced chemical vapor deposition are used as sacrificial templates for nanopipes with internal diameters as small as 30 nm and lengths up to several micrometers that are oriented perpendicular to the substrate. This method provides a high level of control over the nanopipe location, number, length, and diameter, permitting them to be deterministically positioned on a substrate and arranged into arrays.

Nanoscale growth twins in sputtered metal films

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

Misra, Amit; Anderoglu, Osman; Hoagland, Richard G

2008-01-01

We review recent studies on the mechanical properties of sputtered Cu and 330 stainless steel films with {l_brace}1 1 1{r_brace} nanoscale growth twins preferentially oriented perpendicular to growth direction. The mechanisms of formation of growth twins during sputtering and the deformation mechanisms that enable usually high strengths in nanotwinned structures are highlighted. Growth twins in sputtered films possess good thermal stability at elevated temperature, providing an approach to extend the application of high strength nanostructured metals to higher temperatures.

The effect of axial crucible rotation on microstructural uniformity during horizontal directional solidification

NASA Technical Reports Server (NTRS)

Grugel, R. N.; Kim, Shinwoo; Woodward, Tracey; Wang, T. G.

1992-01-01

The effects on microstructure of crucible orientation with respect to the earth's gravitational vector, g, during directional solidification of low-volume fraction copper and aluminum, Pb-Cu, and Sn-Al alloys are examined. It is demonstrated that horizontal alignment (i.e. perpendicular to g) in combination with axial rotation of the crucible during growth is sufficient to negate factors which initiate macrosegregation, e.g. density gradients attributed to temperature and/or compositional differences, and promotes a uniform microstructure.

Method and apparatus for measuring birefringent particles

DOEpatents

Bishop, James K.; Guay, Christopher K.

2006-04-18

A method and apparatus for measuring birefringent particles is provided comprising a source lamp, a grating, a first polarizer having a first transmission axis, a sample cell and a second polarizer having a second polarization axis. The second polarizer has a second polarization axis that is set to be perpendicular to the first polarization axis, and thereby blocks linearly polarized light with the orientation of the beam of light passing through the first polarizer. The beam of light passing through the second polarizer is measured using a detector.

Calculations of Exchange Bias in Thin Films with Ferromagnetic/Antiferromagnetic Interfaces

NASA Astrophysics Data System (ADS)

Koon, N. C.

1997-06-01

A microscopic explanation of exchange bias in thin films with compensated ferro/antiferromagnetic interfaces is presented. Full micromagnetic calculations show the interfacial exchange coupling to be relatively strong with a perpendicular orientation between the ferro/antiferromagnetic axis directions, similar to the classic ``spin-flop'' state in bulk antiferromagnets. With reasonable parameters the calculations predict bias fields comparable to those observed and provide a possible explanation for both anomalous high field rotational hysteresis and recently discovered ``positive'' exchange bias.

Single scattering from nonspherical Chebyshev particles: A compendium of calculations

NASA Technical Reports Server (NTRS)

Wiscombe, W. J.; Mugnai, A.

1986-01-01

A large set of exact calculations of the scattering from a class of nonspherical particles known as Chebyshev particles' has been performed. Phase function and degree of polarization in random orientation, and parallel and perpendicular intensities in fixed orientations, are plotted for a variety of particles shapes and sizes. The intention is to furnish a data base against which both experimental data, and the predictions of approximate methods, can be tested. The calculations are performed with the widely-used Extended Boundary Condition Method. An extensive discussion of this method is given, including much material that is not easily available elsewhere (especially the analysis of its convergence properties). An extensive review is also given of all extant methods for nonspherical scattering calculations, as well as of the available pool of experimental data.

Conductivity of an inverse lyotropic lamellar phase under shear flow

NASA Astrophysics Data System (ADS)

Panizza, P.; Soubiran, L.; Coulon, C.; Roux, D.

2001-08-01

We report conductivity measurements on solutions of closed compact monodisperse multilamellar vesicles (the so-called ``onion texture'') formed by shearing an inverse lyotropic lamellar Lα phase. The conductivity measured in different directions as a function of the applied shear rate reveals a small anisotropy of the onion structure due to the existence of free oriented membranes. The results are analyzed in terms of a simple model that allows one to deduce the conductivity tensor of the Lα phase itself and the proportion of free oriented membranes. The variation of these two parameters is measured along a dilution line and discussed. The high value of the conductivity perpendicular to the layers with respect to that of solvent suggests the existence of a mechanism of ionic transport through the insulating solvent.

Membrane-Based Functions in the Origin of Cellular Life

NASA Technical Reports Server (NTRS)

Wilson, Michael

1997-01-01

If peptides consist of nonpolar residues only, they become inserted into the nonpolar phase. As demonstrated by the example of the leucine undecamer, such peptides fold into an a-helix as they partition into the nonpolar medium. The folding proceeds through an intermediate, called the 310-helix, which remains in equilibrium with the a-helix. This process represents a simple, protobiologically relevant example of environmentally-mediated self-organization of biological molecules. Once in the nonpolar environment, the peptides can readily change their orientation with respect to the interface from parallel to perpendicular, especially in response to local electric fields. The ability of nonpolar peptides to modify both the structure and orientation with changing external conditions may have provided a simple mechanism of transmitting signals from the environment to the interior of a protocell.

Diurnal movements of cotton leaves expressed as thermodynamic work and entropy changes

NASA Technical Reports Server (NTRS)

Schutt, J. B.; Kimes, D. S.; Newcomb, W. W.

1985-01-01

It is pointed out that some important agricultural crops show heliotropic leaf movements. In these species, the proclivity of leaves to orient either perpendicularly or parallel or in some combination of these positions with respect to the sun is controlled by the leaf turgor and the availability of water. Such an orientational response is particularly noticeable for cotton. Schutt et al. (1985) have detailed leaf trajectories using three angles. The present investigation applies the three-angle representation to leaf trajectory mapping and to the calculation of the phase angle 'gamma' between the individual leaf normals and the solar direction. Using gamma, the thermodynamic work and entropy functions are evaluated and used to distinguish between the behavior of water-stressed and well watered cotton canopies.

The Influence of Pulsed Electroplating Frequency and Duty Cycle on Copper Film Microstructure and Stress State

PubMed Central

Marro, James B.; Darroudi, Taghi; Okoro, Chukwudi A.; Obeng, Yaw S.; Richardson, Kathleen C.

2017-01-01

In this work we studied the impact of pulse electroplating parameters on the cross-sectional and surface microstructures of blanket copper films using electron backscattering diffraction and x-ray diffraction. The films evaluated were highly (111) textured in the direction perpendicular to the film surface. The degree of preferential orientation was found to decrease with longer pulse on-times, due to strain energy driven growth of other grain orientations. Residual biaxial stresses were also measured in the films and higher pulse frequencies during deposition led to smaller biaxial stresses in the films. Film stress was also found to correlate with the amount of twinning in the copper film cross-sections. This has been attributed to the twins’ thermal stability and mechanical properties. PMID:28239200

Brownian Motion with Active Fluctuations

NASA Astrophysics Data System (ADS)

Romanczuk, Pawel; Schimansky-Geier, Lutz

2011-06-01

We study the effect of different types of fluctuation on the motion of self-propelled particles in two spatial dimensions. We distinguish between passive and active fluctuations. Passive fluctuations (e.g., thermal fluctuations) are independent of the orientation of the particle. In contrast, active ones point parallel or perpendicular to the time dependent orientation of the particle. We derive analytical expressions for the speed and velocity probability density for a generic model of active Brownian particles, which yields an increased probability of low speeds in the presence of active fluctuations in comparison to the case of purely passive fluctuations. As a consequence, we predict sharply peaked Cartesian velocity probability densities at the origin. Finally, we show that such a behavior may also occur in non-Gaussian active fluctuations and discuss briefly correlations of the fluctuating stochastic forces.

Formation of laser-induced periodic surface structures (LIPSS) on tool steel by multiple picosecond laser pulses of different polarizations

NASA Astrophysics Data System (ADS)

Gregorčič, Peter; Sedlaček, Marko; Podgornik, Bojan; Reif, Jürgen

2016-11-01

Laser-induced periodic surface structures (LIPSS) are produced on cold work tool steel by irradiation with a low number of picosecond laser pulses. As expected, the ripples, with a period of about 90% of the laser wavelength, are oriented perpendicular to the laser polarization. Subsequent irradiation with the polarization rotated by 45° or 90° results in a corresponding rotation of the ripples. This is visible already with the first pulse and becomes almost complete - erasing the previous orientation - after as few as three pulses. The phenomenon is not only observed for single-spot irradiation but also for writing long coherent traces. The experimental results strongly defy the role of surface plasmon-polaritons as the predominant key to LIPSS formation.

Circular-polarization-sensitive metamaterial based on triple-quantum-dot molecules.

PubMed

Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Schön, Gerd

2014-12-05

We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency Ω, above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry.

Mutual orientation of three magnetic tensors in a polycrystalline dipeptide by dipole-modulated 15N chemical shift spectroscopy

NASA Astrophysics Data System (ADS)

Hartzell, C. J.; Pratum, T. K.; Drobny, G.

1987-10-01

This study demonstrates the mutual orientation of three tensor interactions in a single NMR experiment. The orientation of the 15N chemical shift tensor relative to the molecular frame has thus been determined in polycrystalline L-[1-13C] alanyl-L-[15N] alanine. The 13C-15N and 15N-1H dipole interactions are determined using the 1H dipole-modulated, 13C dipole-coupled 15N spectrum obtained as a transform of the data in t2. From simulations of the experimental spectra, two sets of polar angles have been determined relating the 13C-15N and 15N-1H dipoles to the 15N chemical shift tensor. The values determined are βCN =106°, αCN =5° and βNH =-19°, αNH =12°. The experiment verifies, without reference to single crystal data, that σ33 lies in the peptide plane and σ22 is nearly perpendicular to the plane.

A Semi-analytical Line Transfer (SALT) Model. II: The Effects of a Bi-conical Geometry

NASA Astrophysics Data System (ADS)

Carr, Cody; Scarlata, Claudia; Panagia, Nino; Henry, Alaina

2018-06-01

We generalize the semi-analytical line transfer model recently introduced by Scarlata & Panagia for modeling galactic outflows, to account for bi-conical geometries of various opening angles and orientations with respect to the line of sight to the observer, as well as generalized velocity fields. We model the absorption and emission component of the line profile resulting from resonant absorption in the bi-conical outflow. We show how the outflow geometry impacts the resulting line profile. We use simulated spectra with different geometries and velocity fields to study how well the outflow parameters can be recovered. We find that geometrical parameters (including the opening angle and the orientation) are always well recovered. The density and velocity field parameters are reliably recovered when both an absorption and an emission component are visible in the spectra. This condition implies that the velocity and density fields for narrow cones oriented perpendicular to the line of sight will remain unconstrained.

Anisotropy of diamagnetic susceptibility in Thassos marble: A comparison between measured and modeled data

NASA Astrophysics Data System (ADS)

de Wall, Helga; Bestmann, Michel; Ullemeyer, Klaus

2000-11-01

A study of shear zones within the calcite marble complex of the island of Thassos (Greece) shows that the low field anisotropy of magnetic susceptibility (AMS)-technique can be successfully applied to diamagnetic rocks for characterizing rock fabrics. The strain path involves both an early pure shear stage and a simple shear overprint that is documented by a transition from triaxial (neutral) to uniaxial (prolate) shapes of AMS ellipsoids. The maximum susceptibility is oriented perpendicular to the rock foliation, reflecting the preferred orientation of calcite c-axes in the protolith as well as in the mylonites. For three samples that represent different types of calcite fabrics, the AMS was recalculated from neutron and electron backscatter diffraction textural data. A comparison of the measured and modeled data shows a good coincidence for the orientation of the principal AMS axes and for the recalculated anisotropy data. Both measured and modeled data sets reflect the change from neutral to distinct prolate ellipsoids during progressive deformation.

Wave-plate structures, power selective optical filter devices, and optical systems using same

DOEpatents

Koplow, Jeffrey P [San Ramon, CA

2012-07-03

In an embodiment, an optical filter device includes an input polarizer for selectively transmitting an input signal. The device includes a wave-plate structure positioned to receive the input signal, which includes first and second substantially zero-order, zero-wave plates arranged in series with and oriented at an angle relative to each other. The first and second zero-wave plates are configured to alter a polarization state of the input signal passing in a manner that depends on the power of the input signal. Each zero-wave plate includes an entry and exit wave plate each having a fast axis, with the fast axes oriented substantially perpendicular to each other. Each entry wave plate is oriented relative to a transmission axis of the input polarizer at a respective angle. An output polarizer is positioned to receive a signal output from the wave-plate structure and selectively transmits the signal based on the polarization state.

The High Strain Rate Deformation Behavior of High Purity Magnesium and AZ31B Magnesium Alloy

NASA Astrophysics Data System (ADS)

Livescu, Veronica; Cady, Carl M.; Cerreta, Ellen K.; Henrie, Benjamin L.; Gray, George T.

The deformation in compression of pure magnesium and AZ31B magnesium alloy, both with a strong basal pole texture, has been investigated as a function of temperature, strain rate, and specimen orientation. The mechanical response of both metals is highly dependent upon the orientation of loading direction with respect to the basal pole. Specimens compressed along the basal pole direction have a high sensitivity to strain rate and temperature and display a concave down work hardening behavior. Specimens loaded perpendicularly to the basal pole have a yield stress that is relatively insensitive to strain rate and temperature and a work hardening behavior that is parabolic and then linearly upwards. Both specimen orientations display a mechanical response that is sensitive to temperature and strain rate. Post mortem characterization of the pure magnesium was conducted on a subset of specimens to determine the microstructural and textural evolution during deformation and these results are correlated with the observed work hardening behavior and strain rate sensitivities were calculated.

Measurement of Anisotropic Particle Interactions with Nonuniform ac Electric Fields.

PubMed

Rupp, Bradley; Torres-Díaz, Isaac; Hua, Xiaoqing; Bevan, Michael A

2018-02-20

Optical microscopy measurements are reported for single anisotropic polymer particles interacting with nonuniform ac electric fields. The present study is limited to conditions where gravity confines particles with their long axis parallel to the substrate such that particles can be treated using quasi-2D analysis. Field parameters are investigated that result in particles residing at either electric field maxima or minima and with long axes oriented either parallel or perpendicular to the electric field direction. By nonintrusively observing thermally sampled positions and orientations at different field frequencies and amplitudes, a Boltzmann inversion of the time-averaged probability of states yields kT-scale energy landscapes (including dipole-field, particle-substrate, and gravitational potentials). The measured energy landscapes show agreement with theoretical potentials using particle conductivity as the sole adjustable material property. Understanding anisotropic particle-field energy landscapes vs field parameters enables quantitative control of local forces and torques on single anisotropic particles to manipulate their position and orientation within nonuniform fields.

Analytical models for coupling reliability in identical two-magnet systems during slow reversals

NASA Astrophysics Data System (ADS)

Kani, Nickvash; Naeemi, Azad

2017-12-01

This paper follows previous works which investigated the strength of dipolar coupling in two-magnet systems. While those works focused on qualitative analyses, this manuscript elucidates reversal through dipolar coupling culminating in analytical expressions for reversal reliability in identical two-magnet systems. The dipolar field generated by a mono-domain magnetic body can be represented by a tensor containing both longitudinal and perpendicular field components; this field changes orientation and magnitude based on the magnetization of neighboring nanomagnets. While the dipolar field does reduce to its longitudinal component at short time-scales, for slow magnetization reversals, the simple longitudinal field representation greatly underestimates the scope of parameters that ensure reliable coupling. For the first time, analytical models that map the geometric and material parameters required for reliable coupling in two-magnet systems are developed. It is shown that in biaxial nanomagnets, the x ̂ and y ̂ components of the dipolar field contribute to the coupling, while all three dimensions contribute to the coupling between a pair of uniaxial magnets. Additionally, the ratio of the longitudinal and perpendicular components of the dipolar field is also very important. If the perpendicular components in the dipolar tensor are too large, the nanomagnet pair may come to rest in an undesirable meta-stable state away from the free axis. The analytical models formulated in this manuscript map the minimum and maximum parameters for reliable coupling. Using these models, it is shown that there is a very small range of material parameters which can facilitate reliable coupling between perpendicular-magnetic-anisotropy nanomagnets; hence, in-plane nanomagnets are more suitable for coupled systems.

Tailoring the morphology of electrodeposited ZnO and its photoluminescence properties

NASA Astrophysics Data System (ADS)

Cui, H.; Mollar, M.; Marí, B.

2011-01-01

High density ZnO columnar films with well-aligned and well-perpendicular to the surface of film were electrodeposited on ITO substrates by using an electrolyte consisting of a mix of water and organic solvent namely dimethylsulfoxide (DMSO). The effect of mixing ratio of water and DMSO on the growth of film has been examined critically. SEM images have shown that well-oriented ZnO quasi-nano columns were formed perpendicular to the substrate. At the same time we found there are three kinds of competitions for growth of ZnO crystalmorphology i.e. column, rod and needle like. The needle like morphology has high density with well-aligned structure. The reasons for the growth of films of different morphology and their photoluminescence (PL) properties have been presented and discussed. It has been found that the three-dimensional (3D) ordered ZnO structure exhibits high intensity PL band which may shift their position and intensity with the varying conditions of depositions.

Mechanical and electrical strain response of a piezoelectric auxetic PZT lattice structure

NASA Astrophysics Data System (ADS)

Fey, Tobias; Eichhorn, Franziska; Han, Guifang; Ebert, Kathrin; Wegener, Moritz; Roosen, Andreas; Kakimoto, Ken-ichi; Greil, Peter

2016-01-01

A two-dimensional auxetic lattice structure was fabricated from a PZT piezoceramic. Tape casted and sintered sheets with a thickness of 530 μm were laser cut into inverted honeycomb lattice structure with re-entrant cell geometry (θ = -25°) and poling direction oriented perpendicular to the lattice plane. The in-plane strain response upon applying an uniaxial compression load as well as an electric field perpendicular to the lattice plane were analyzed by a 2D image data detection analysis. The auxetic lattice structure exhibits orthotropic deformation behavior with a negative in-plane Poisson’s ratio of -2.05. Compared to PZT bulk material the piezoelectric auxetic lattice revealed a strain amplification by a factor of 30-70. Effective transversal coupling coefficients {{d}al}31 of the PZT lattice exceeding 4 × 103 pm V-1 were determined which result in an effective hydrostatic coefficient {{d}al}h 66 times larger than that of bulk PZT.

Importance of projectile-target interactions in the triple differential cross sections for Low energy (e,2e) ionization of aligned H2

NASA Astrophysics Data System (ADS)

Ali, Esam; Madison, Don; Ren, X.; Dorn, A.; Ning, Chuangang

2014-10-01

Experimental and theoretical Triple Differential Cross Sections (TDCS) are presented for electron impact ionization-excitation of the 2 sσg state of H2 in the perpendicular plane. The excited 2 sσg state immediately dissociates and the alignment of the molecule is determined by detecting one of the fragments. Results are presented for three different alignments in the xy-plane (scattering plane is xz)-alignment along y-axis, x-axis, and 45° between the x- and y-axes for incident electron energies of 4, 10, and 25 eV and different scattered electron angles of 20° and 30° in the perpendicular plane. Theoretical M4DW (molecular 4-body distorted wave) results are compared to experimental data, and overall we found reasonably good agreement between experiment and theory. The Results show that (e,2e) cross sections for excitation-ionization depend strongly on the orientation of the H2 molecule.

Role of polarizer-tilting-angle in zero-field spin-transfer nano-oscillators with perpendicular anisotropy

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

Gonzalez-Fuentes, C.; Gallardo, R. A., E-mail: rodolfo.gallardo@usm.cl; Landeros, P.

2015-10-05

An analytical model for studying the stability of a single domain ferromagnetic layer under the influence of a spin-polarized current is presented. The theory is applied to bias-field-free nano-oscillators with perpendicular anisotropy, which allows to obtain a polarizer-angle vs. current phase diagram that describes the stability of magnetic states. Explicit formulae for the critical current densities unveil the influence of the relative orientation between free and polarizer layers, allowing the emergence of precessional steady-states, and also the possibility to reduce the magnitude of the threshold current density to produce microwave oscillations. It is shown that oscillating steady-states arise in amore » broad angular region, and the dependence of their boundaries is fully specified by the model. The reliability of the analytical results has been corroborated by comparison to numerical calculations. Such structures are currently under intense research because of remarkable properties offering new prospects for microwave applications in communication technologies.« less

A Dzyaloshinskii-Moriya Anisotropy in nanomagnets with in-plane magnetization

NASA Astrophysics Data System (ADS)

Cubukcu, M.; Sampaio, J.; Khvalkovskiy, A. V.; Apalkov, D.; Cros, V.; Reyren, N.

The Dzyaloshinskii-Moriya interaction (DMI) is known to be a direct manifestation of spin-orbit coupling in systems with broken inversion symmetry. We present a new anisotropy for in-plane-magnetized nanomagnets which is due to the interfacial DMI. This new anisotropy depends on the shape of the magnet, and is perpendicular to the demagnetization shape anisotropy. The DMI anisotropy term that we introduce here results from the DMI energy reduction due to an out-of-plane tilt of the spins at the edges that are oriented perpendicular to the magnetization. For large enough DMI, the reduction of the DMI and anisotropy energies takes over the demagnetization energy cost when magnetization lies along the minor axis of a structure. Our experimental, numerical and analytical results demonstrate this prediction in magnets of elongated shape for small enough volume (and thus quasi-uniform magnetization). Our results also provide the first experimental evidence of the interfacial DMI-induced tilt of the spins at the borders. This work was supported by the Samsung Global MRAM Innovation Program.

How supercontinents and superoceans affect seafloor roughness.

PubMed

Whittaker, Joanne M; Müller, R Dietmar; Roest, Walter R; Wessel, Paul; Smith, Walter H F

2008-12-18

Seafloor roughness varies considerably across the world's ocean basins and is fundamental to controlling the circulation and mixing of heat in the ocean and dissipating eddy kinetic energy. Models derived from analyses of active mid-ocean ridges suggest that ocean floor roughness depends on seafloor spreading rates, with rougher basement forming below a half-spreading rate threshold of 30-35 mm yr(-1) (refs 4, 5), as well as on the local interaction of mid-ocean ridges with mantle plumes or cold-spots. Here we present a global analysis of marine gravity-derived roughness, sediment thickness, seafloor isochrons and palaeo-spreading rates of Cretaceous to Cenozoic ridge flanks. Our analysis reveals that, after eliminating effects related to spreading rate and sediment thickness, residual roughness anomalies of 5-20 mGal remain over large swaths of ocean floor. We found that the roughness as a function of palaeo-spreading directions and isochron orientations indicates that most of the observed excess roughness is not related to spreading obliquity, as this effect is restricted to relatively rare occurrences of very high obliquity angles (>45 degrees ). Cretaceous Atlantic ocean floor, formed over mantle previously overlain by the Pangaea supercontinent, displays anomalously low roughness away from mantle plumes and is independent of spreading rates. We attribute this observation to a sub-Pangaean supercontinental mantle temperature anomaly leading to slightly thicker than normal Late Jurassic and Cretaceous Atlantic crust, reduced brittle fracturing and smoother basement relief. In contrast, ocean crust formed above Pacific superswells, probably reflecting metasomatized lithosphere underlain by mantle at only slightly elevated temperatures, is not associated with basement roughness anomalies. These results highlight a fundamental difference in the nature of large-scale mantle upwellings below supercontinents and superoceans, and their impact on oceanic crustal accretion.

Effect of roughness formulation on the performance of a coupled wave, hydrodynamic, and sediment transport model

USGS Publications Warehouse

Ganju, Neil K.; Sherwood, Christopher R.

2010-01-01

A variety of algorithms are available for parameterizing the hydrodynamic bottom roughness associated with grain size, saltation, bedforms, and wave–current interaction in coastal ocean models. These parameterizations give rise to spatially and temporally variable bottom-drag coefficients that ostensibly provide better representations of physical processes than uniform and constant coefficients. However, few studies have been performed to determine whether improved representation of these variable bottom roughness components translates into measurable improvements in model skill. We test the hypothesis that improved representation of variable bottom roughness improves performance with respect to near-bed circulation, bottom stresses, or turbulence dissipation. The inner shelf south of Martha’s Vineyard, Massachusetts, is the site of sorted grain-size features which exhibit sharp alongshore variations in grain size and ripple geometry over gentle bathymetric relief; this area provides a suitable testing ground for roughness parameterizations. We first establish the skill of a nested regional model for currents, waves, stresses, and turbulent quantities using a uniform and constant roughness; we then gauge model skill with various parameterization of roughness, which account for the influence of the wave-boundary layer, grain size, saltation, and rippled bedforms. We find that commonly used representations of ripple-induced roughness, when combined with a wave–current interaction routine, do not significantly improve skill for circulation, and significantly decrease skill with respect to stresses and turbulence dissipation. Ripple orientation with respect to dominant currents and ripple shape may be responsible for complicating a straightforward estimate of the roughness contribution from ripples. In addition, sediment-induced stratification may be responsible for lower stresses than predicted by the wave–current interaction model.

Study of the three-dimensional orientation of the labrum: its relations with the osseous acetabular rim

PubMed Central

Bonneau, Noémie; Bouhallier, July; Baylac, Michel; Tardieu, Christine; Gagey, Olivier

2012-01-01

Understanding the three-dimensional orientation of the coxo-femoral joint remains a challenge as an accurate three-dimensional orientation ensure an efficient bipedal gait and posture. The quantification of the orientation of the acetabulum can be performed using the three-dimensional axis perpendicular to the plane that passes along the edge of the acetabular rim. However, the acetabular rim is not regular as an important indentation in the anterior rim was observed. An innovative cadaver study of the labrum was developed to shed light on the proper quantification of the three-dimensional orientation of the acetabulum. Dissections on 17 non-embalmed corpses were performed. Our results suggest that the acetabular rim is better represented by an anterior plane and a posterior plane rather than a single plane along the entire rim as it is currently assumed. The development of the socket from the Y-shaped cartilage was suggested to explain the different orientations in these anterior and posterior planes. The labrum forms a plane that takes an orientation in between the anterior and posterior parts of the acetabular rim, filling up inequalities of the bony rim. The vectors VL, VA2 and VP, representing the three-dimensional orientation of the labrum, the anterior rim and the posterior rim, are situated in a unique plane that appears biomechanically dependent. The three-dimensional orientation of the acetabulum is a fundamental parameter to understand the hip joint mechanism. Important applications for hip surgery and rehabilitation, as well as for physical anthropology, were discussed. PMID:22360458

A method to determine the orientation of the upper arm about its longitudinal axis during dynamic motions.

PubMed

Gordon, Brian J; Dapena, Jesús

2013-01-04

Inaccuracy in determining the orientation of the upper arm about its longitudinal axis (twist orientation) has been a pervasive problem in sport biomechanics research. The purpose of this study was to develop a method to improve the calculation of the upper arm twist orientation in dynamic sports activities. The twist orientation of the upper arm is defined by the orientation of its mediolateral axis. The basis for the new method is that at any angle in the flexion/extension range of an individual's elbow, it is possible to define a true mediolateral axis and also a surrogate mediolateral axis perpendicular to the plane containing the shoulder, elbow and wrist joints. The difference between the twist orientations indicated by these two versions of the mediolateral axis will vary from one elbow angle to another, but if the elbow joint deforms equally in different activities, for any given subject the difference should be constant at any given value of the elbow angle. Application of the new method required individuals to execute sedate elbow extension trials prior to the dynamic trials. Three-dimensional motion analysis of the sedate extension trials allowed quantification of the difference between the true and surrogate mediolateral axes for all angles in the entire flexion/extension range of an individual's elbow. This made it possible to calculate in any dynamic trial the twist orientation defined by the true mediolateral axis from the twist orientation defined by the surrogate mediolateral axis. The method was tested on a wooden model of the arm. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Electrochemical Assembly of Semiconducting Organic-Inorganic Lamellar Domains for Photovoltaics

NASA Astrophysics Data System (ADS)

Herman, David John

This dissertation investigates the one-step electrodeposition of alternating nanoscale domains of n-type ZnO and p-type organic molecules for photovoltaics. In such hybrid photovoltaic systems, a nanoscale lamellar periodicity of 5-10 nm between electron donor and electron acceptor materials is ideal for efficient exciton separation. In addition, achieving uniform density and substrate-wide alignment of the hybrid lamellar structures with orientation perpendicular to substrate surfaces is important in providing direct pathways for charge carriers to the electrodes. To this end, it is first reported how to control the assembly of the pyrene-based surfactant 1-pyrenebutyric acid (PyBA) with zinc hydroxide (a precursor to the semiconductor ZnO), resulting in a nanoscale lamellar structure with a periodicity of 3.2 nm. By exploring solution chemistry parameters, the surfactant concentration and solvent composition are shown to have the greatest effect on the morphology of lamellar growth. By studying the early nucleation and growth on indium tin oxide (ITO) substrates with 2D grazing incidence small angle X-ray scattering, it is revealed that the lamellae preferentially nucleate parallel to the hydrophilic ITO surface. It is hypothesized that the conductive and more hydrophobic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) surface increases the affinity for the pyrene functions to the surface, and therefore the oriented growth of the lamellae changes from parallel to perpendicular with respect to the substrate surface. The second part of this thesis investigates the effects of conjugated surfactant design in directing the growth of hybrid lamellar structures by incorporating either a pyrene or terthiophene moiety and varying overall molecular design. It is found that high aspect ratio and amphiphilic surfactants possessing a flexible alkyl spacer between the carboxylic acid and conjugated moiety consistently allow for the controlled and directed assembly of lamellae with orientations either parallel (on ITO) or perpendicular (on PEDOT:PSS) to the substrate. For surfactants without the spacer or with bolaamphiphilic design, the decrease in entropic freedom either during surface assembly or during lamellae growth is believed to result in uncontrolled orientations and heterogeneous morphologies. In all cases, the lack or low-density of solution micelles at the deposition conditions implied that the growth and orientation of lamellar structures is mediated by surfactant-substrate interactions and assemblies. Finally, the controlled deposition of quinquethiophene surfactant and ZnO lamellae with a periodicity of 2.5 nm was achieved. By optimizing the device architecture with an inverted design, the photovoltaic efficiency improved from 0.0008% to 0.01%. Converting the Zn(OH)2 to ZnO by annealing at 150 °C and pulsing the electrodeposition potential led to a three-fold improvement in efficiency to 0.035%. External quantum efficiency measurements indicate that pulsed depositions lead to better π-π stacking of the thiophenes inside the lamellar galleries. Although the seemingly ideal assembly between n- and p-type materials is approached and photovoltaic devices are demonstrated, the efficiencies remain limited due to high charge carrier resistances from the excess active layer thickness, which was required to prevent electrode shorting during device fabrication.

Peptide backbone orientation and dynamics in spider dragline silk and two-photon excitation in nuclear magnetic and quadrupole resonance

NASA Astrophysics Data System (ADS)

Eles, Philip Thomas

2005-07-01

In the first part of the dissertation, spider dragline silk is studied by solid state NMR techniques. The dependence of NMR frequency on molecular orientation is exploited using the DECODER experiment to determine the orientation of the protein backbone within the silk fibre. Practical experimental considerations require that the silk fibres be wound about a cylindrical axis perpendicular to the external magnetic field, complicating the reconstruction of the underlying orientation distribution and necess-itating the development of numerical techniques for this purpose. A two-component model of silk incorporating static b-sheets and polyglycine II helices adequately fits the NMR data and suggests that the b-sheets are well aligned along the silk axis (20 FWHM) while the helices are poorly aligned (68 FWHM). The effects of fibre strain, draw rate and hydration on orientation are measured. Measurements of the time-scale for peptide backbone motion indicate that when wet, a strain-dependent frac-tion of the poorly aligned component becomes mobile. This suggests a mechanism for the supercontraction of silk involving latent entropic springs that undergo a local strain-dependent phase transition, driving supercontraction. In the second part of this dissertation a novel method is developed for exciting NMR and nuclear quadrupole resonance (NQR) by rf irradiation at multiple frequencies that sum to (or differ by) the resonance frequency. This is fundamentally different than traditional NMR experiments where irradiation is applied on-resonance. With excitation outside the detection bandwidth, two-photon excitation allows for detection of free induction signals during excitation, completely eliminating receiver dead-time. A theoretical approach to describing two-photon excitation is developed based on average Hamiltonian theory. An intuition for two-photon excitation is gained by analogy to the coherent absorption of multiple photons requiring conservation of total energy and momentum. It is shown that two-photon excitation efficiency impro-ves when the two applied rf frequencies deviate from half-resonance. For two-photon NQR, it is shown that observable magnetization appears perpendicular to the excita-tion coil, requiring a second coil for detection, and that double quantum coherences are also generated. Several model systems and experimental geometries are used to demonstrate the peculiarities of two-photon excitation in NMR and NQR.

Fractured-aquifer hydrogeology from geophysical logs; the passaic formation, New Jersey

USGS Publications Warehouse

Morin, R.H.; Carleton, G.B.; Poirier, S.

1997-01-01

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84??W and dip of 20??N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79??E and dip of 71??S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally diminish in magnitude and frequency with depth. The high-angle fractures have average transmissivities that are about half those of the bedding-plane partings and show no apparent dependence upon depth. The geophysical logging results allow us to infer a distinct hydrogeologic structure within this aquifer that is defined by fracture type and orientation. Fluid flow near the surface is controlled primarily by the highly transmissive, subhorizontal bedding-plane partings. As depth increases, the high-angle fractures apparently become more dominant hydrologically.The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84?? W and dip of 20?? N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79?? E and dip of 71?? S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally dimi

Electrostatic ion cyclotron velocity shear instability

NASA Technical Reports Server (NTRS)

Lemons, D. S.; Winske, D.; Gary, S. P.

1992-01-01

A local electrostatic dispersion equation is derived for a shear flow perpendicular to an ambient magnetic field, which includes all kinetic effects and involves only one important parameter. The dispersion equation is cast in the form of Gordeyev integrals and is solved numerically. Numerical solutions indicate that an ion cyclotron instability is excited. The instability occurs roughly at multiples of the ion cyclotron frequency (modified by the shear), with the growth rate or the individual harmonics overlapping in the wavenumber. At large values of the shear parameter, the instability is confined to long wavelengths, but at smaller shear, a second distinct branch at shorter wavelengths also appears. The properties of the instability obtained are compared with those obtained in the nonlocal limit by Ganguli et al. (1985, 1988).

Spectromicroscopy study of interfacial Co/NiO(001)

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

van der Laan, Gerrit; Telling, Neil; Potenza, Alberto

2010-09-26

Photoemission electron microscopy (PEEM) with linearly polarized x-rays is used to determine the orientation of antiferromagnetic domains by monitoring the relative peak intensities at the 3d transition metal L{sub 2} absorption edge. In such an analysis the orientations of the x-ray polarization E and magnetization H with respect to the crystalline axes has to be taken into account. We address this problem by presenting a general expression of the angular dependence for both x-ray absorption spectroscopy and x-ray magnetic linear dichroism (XMLD) for arbitrary direction of E and H in the (001) cubic plane. In cubic symmetry the angular dependentmore » XMLD is a linear combination of two spectra with different photon energy dependence, which reduces to one spectrum when E or H is along a high-symmetry axis. The angular dependent XMLD can be separated into an isotropic term, which is symmetric along H, and an anisotropic term, which depends on the orientation of the crystal axes. The anisotropic term has maximal intensity when E and H have equal but opposite angles with respect to the [100] direction. The Ni{sup 2+} L{sub 2} edge has the peculiarity that the isotropic term vanishes, which means that the maximum in the XMLD intensity is observed not only for E {parallel} H {parallel} [100] but also for (E {parallel} [110], H {parallel} [110]). We apply the angular dependent theory to determine the spin orientation near the Co/NiO(100) interface. The PEEM images show that the ferromagnetic Co moments and antiferromagnetic NiO moments are aligned perpendicular to each other. By rotating the sample with respect to the linear x-ray polarization we furthermore find that the perpendicular coupling with the ferromagnetic Co layer at the interface causes a canting of the antiferromagnetic Ni moments. This shows that taking into account the angular dependence of the XMLD in the detailed analysis of PEEM images leads to an accurate retrieval of the spin axes of the antiferromagnetic domains.« less

Mapping Magnetic Susceptibility Anisotropies of White Matter in vivo in the Human Brain at 7 Tesla

PubMed Central

Li, Xu; Vikram, Deepti S; Lim, Issel Anne L; Jones, Craig K; Farrell, Jonathan A.D.; van Zijl, Peter C. M.

2012-01-01

High-resolution magnetic resonance phase- or frequency- shift images acquired at high field show contrast related to magnetic susceptibility differences between tissues. Such contrast varies with the orientation of the organ in the field, but the development of quantitative susceptibility mapping (QSM) has made it possible to reproducibly image the intrinsic tissue susceptibility contrast. However, recent studies indicate that magnetic susceptibility is anisotropic in brain white matter and, as such, needs to be described by a symmetric second-rank tensor (χ¯¯). To fully determine the elements of this tensor, it would be necessary to acquire frequency data at six or more orientations. Assuming cylindrical symmetry of the susceptibility tensor in myelinated white matter fibers, we propose a simplified method to reconstruct the susceptibility tensor in terms of a mean magnetic susceptibility, MMS = (χ∥ + 2χ⊥)/3 and a magnetic susceptibility anisotropy, MSA = χ∥ − χ⊥, where χ∥ and χ⊥ are susceptibility parallel and perpendicular to the white matter fiber direction, respectively. Computer simulations show that with a practical head rotation angle of around 20°–30°, four head orientations suffice to reproducibly reconstruct the tensor with good accuracy. We tested this approach on whole brain 1×1×1 mm3 frequency data acquired from five healthy subjects at 7 T. The frequency information from phase images collected at four head orientations was combined with the fiber direction information extracted from diffusion tensor imaging (DTI) to map the white matter susceptibility tensor. The MMS and MSA were quantified for regions in several large white matter fiber structures, including the corona radiata, posterior thalamic radiation and corpus callosum. MMS ranged from −0.037 to −0.053 ppm (referenced to CSF being about zero). MSA values could be quantified without the need for a reference and ranged between 0.004 and 0.029 ppm, in line with the expectation that the susceptibility perpendicular to the fiber is more diamagnetic than the one parallel to it. PMID:22561358

Comparison of molecular orientation and phase transition behaviors in the two kinds of ordered ultrathin films of reversed duckweed polymer ES-3 studied by infrared grazing reflection-absorption spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Qiang; Xu, Weiqing; Zhao, Bing

2003-03-01

A multilayer LB film and a casting film of reversed duckweed polymer ES-3 on Au-evaporated glass slides were investigated by Fourier Transform infrared grazing reflection-absorption spectroscopy. It is found that the two kinds of ordered ultrathin films have different orientation of alkyl chains, nearly perpendicular to the substrate surface for the LB film while rather tilted for the casting film. The studies on their thermal transition behaviors indicate that both of the films have three phase transition processes, respectively, occurring near 65, 105 and 140 °C for the former while near 80, 105 and 140 °C for the latter, but show different transition behavior in the each corresponding transition process. It is referred that at room temperature there are island-like domain structures formed in the LB film, but no ones in the casting film; however, the latter can form the domain structures between the first two transition points due to the desorption of solvents. The formation of domain structure seems to play two important roles, one of which is to make alkyl chains more perpendicular to the substrate surface, and the other to make alkyl chains more packed closely. Thermal cyclic experiments reveal that neither of the films could return to its original state after thermal cyclic treatment up to the temperature, which is above the third transition point, although its alkyl chain becomes highly ordered again.

Dunes and microdunes on Venus: Why were so few found in the Magellan data?

NASA Technical Reports Server (NTRS)

Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

1994-01-01

A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle 1 images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel relfections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

Dunes and Microdunes on Venus: Why Were So Few Found in the Magellan Data?

NASA Technical Reports Server (NTRS)

Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

1994-01-01

A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle I images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel reflections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be the most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

Ca2+ improves organization of single-stranded DNA bases in human Rad51 filament, explaining stimulatory effect on gene recombination.

PubMed

Fornander, Louise H; Frykholm, Karolin; Reymer, Anna; Renodon-Cornière, Axelle; Takahashi, Masayuki; Nordén, Bengt

2012-06-01

Human RAD51 protein (HsRad51) catalyses the DNA strand exchange reaction for homologous recombination. To clarify the molecular mechanism of the reaction in vitro being more effective in the presence of Ca(2+) than of Mg(2+), we have investigated the effect of these ions on the structure of HsRad51 filament complexes with single- and double-stranded DNA, the reaction intermediates. Flow linear dichroism spectroscopy shows that the two ionic conditions induce significantly different structures in the HsRad51/single-stranded DNA complex, while the HsRad51/double-stranded DNA complex does not demonstrate this ionic dependence. In the HsRad51/single-stranded DNA filament, the primary intermediate of the strand exchange reaction, ATP/Ca(2+) induces an ordered conformation of DNA, with preferentially perpendicular orientation of nucleobases relative to the filament axis, while the presence of ATP/Mg(2+), ADP/Mg(2+) or ADP/Ca(2+) does not. A high strand exchange activity is observed for the filament formed with ATP/Ca(2+), whereas the other filaments exhibit lower activity. Molecular modelling suggests that the structural variation is caused by the divalent cation interfering with the L2 loop close to the DNA-binding site. It is proposed that the larger Ca(2+) stabilizes the loop conformation and thereby the protein-DNA interaction. A tight binding of DNA, with bases perpendicularly oriented, could facilitate strand exchange.

Supramolecular order and structural dynamics: A STM study of 2H-tetraphenylporphycene on Cu(111)

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

Stark, Michael; Träg, Johannes; Ditze, Stefanie

2015-03-14

The adsorption of 2H-tetraphenylporphycene (2HTPPc) on Cu(111) was investigated by scanning tunneling microscopy (STM). At medium coverages, supramolecular ordered islands are observed. The individual 2HTPPc molecules appear as two pairs of intense protrusions which are separated by an elongated depression. In the islands, the molecules are organized in rows oriented along one of the close packed Cu(111) substrate rows; the structure is stabilized by T-type interactions of the phenyl substituents of neighboring molecules. Two types of rows are observed, namely, highly ordered rows in which all molecules exhibit the same orientation, and less ordered rows in which the molecules exhibitmore » two perpendicular orientations. Altogether, three different azimuthal orientations of 2HTPPc are observed within one domain, all of them rotated by 15° ± 1° relative to one closed packed Cu direction. The highly ordered rows are always separated by either one or two less ordered rows, with the latter structure being the thermodynamically more stable one. The situation in the islands is highly dynamic, such that molecules in the less ordered rows occasionally change orientation, also complete highly ordered rows can move. The supramolecular order and structural dynamics are discussed on the basis of the specific molecule-substrate and molecule-molecule interactions.« less

COBRA, an Arabidopsis Extracellular Glycosyl-Phosphatidyl Inositol-Anchored Protein, Specifically Controls Highly Anisotropic Expansion through Its Involvement in Cellulose Microfibril OrientationW⃞

PubMed Central

Roudier, François; Fernandez, Anita G.; Fujita, Miki; Himmelspach, Regina; Borner, Georg H.H.; Schindelman, Gary; Song, Shuang; Baskin, Tobias I.; Dupree, Paul; Wasteneys, Geoffrey O.; Benfey, Philip N.

2005-01-01

The orientation of cell expansion is a process at the heart of plant morphogenesis. Cellulose microfibrils are the primary anisotropic material in the cell wall and thus are likely to be the main determinant of the orientation of cell expansion. COBRA (COB) has been identified previously as a potential regulator of cellulose biogenesis. In this study, characterization of a null allele, cob-4, establishes the key role of COB in controlling anisotropic expansion in most developing organs. Quantitative polarized-light and field-emission scanning electron microscopy reveal that loss of anisotropic expansion in cob mutants is accompanied by disorganization of the orientation of cellulose microfibrils and subsequent reduction of crystalline cellulose. Analyses of the conditional cob-1 allele suggested that COB is primarily implicated in microfibril deposition during rapid elongation. Immunodetection analysis in elongating root cells revealed that, in agreement with its substitution by a glycosylphosphatidylinositol anchor, COB was polarly targeted to both the plasma membrane and the longitudinal cell walls and was distributed in a banding pattern perpendicular to the longitudinal axis via a microtubule-dependent mechanism. Our observations suggest that COB, through its involvement in cellulose microfibril orientation, is an essential factor in highly anisotropic expansion during plant morphogenesis. PMID:15849274

COBRA, an Arabidopsis extracellular glycosyl-phosphatidyl inositol-anchored protein, specifically controls highly anisotropic expansion through its involvement in cellulose microfibril orientation.

PubMed

Roudier, François; Fernandez, Anita G; Fujita, Miki; Himmelspach, Regina; Borner, Georg H H; Schindelman, Gary; Song, Shuang; Baskin, Tobias I; Dupree, Paul; Wasteneys, Geoffrey O; Benfey, Philip N

2005-06-01

The orientation of cell expansion is a process at the heart of plant morphogenesis. Cellulose microfibrils are the primary anisotropic material in the cell wall and thus are likely to be the main determinant of the orientation of cell expansion. COBRA (COB) has been identified previously as a potential regulator of cellulose biogenesis. In this study, characterization of a null allele, cob-4, establishes the key role of COB in controlling anisotropic expansion in most developing organs. Quantitative polarized-light and field-emission scanning electron microscopy reveal that loss of anisotropic expansion in cob mutants is accompanied by disorganization of the orientation of cellulose microfibrils and subsequent reduction of crystalline cellulose. Analyses of the conditional cob-1 allele suggested that COB is primarily implicated in microfibril deposition during rapid elongation. Immunodetection analysis in elongating root cells revealed that, in agreement with its substitution by a glycosylphosphatidylinositol anchor, COB was polarly targeted to both the plasma membrane and the longitudinal cell walls and was distributed in a banding pattern perpendicular to the longitudinal axis via a microtubule-dependent mechanism. Our observations suggest that COB, through its involvement in cellulose microfibril orientation, is an essential factor in highly anisotropic expansion during plant morphogenesis.

Liquid-Vapor Interfacial Properties of Aqueous Solutions of Guanidinium and Methyl Guanidinium Chloride: Influence of Molecular Orientation on Interface Fluctuations

PubMed Central

Ou, Shuching; Cui, Di; Patel, Sandeep

2014-01-01

The guanidinium cation (C(NH2)3+) is a highly stable cation in aqueous solution due to its efficient solvation by water molecules and resonance stabilization of the charge. Its salts increase the solubility of nonpolar molecules (”salting-in”) and decrease the ordering of water. It is one of the strongest denaturants used in biophysical studies of protein folding. We investigate the behavior of guanidinium and its derivative, methyl guanidinium (an amino acid analogue) at the air-water surface, using atomistic molecular dynamics (MD) simulations and calculation of potentials of mean force. Methyl guanidinium cation is less excluded from the air-water surface than guanidinium cation, but both cations show orientational dependence of surface affinity. Parallel orientations of the guanidinium ring (relative to the Gibbs dividing surface) show pronounced free energy minima in the interfacial region, while ring orientations perpendicular to the GDS exhibit no discernible surface stability. Calculations of surface fluctuations demonstrate that near the air-water surface, the parallel-oriented cations generate significantly greater interfacial fluctuations compared to other orientations, which induces more long-ranged perturbations and solvent density redistribution. Our results suggest a strong correlation with induced interfacial fluctuations and ion surface stability. These results have implications for interpreting molecular-level, mechanistic action of this osmolyte’s interaction with hydrophobic interfaces as they impact protein denaturation (solubilization). PMID:23937431

Oriented Nucleation of both Ge-Fresnoite and Benitoite/BaGe4O9 during the Surface Crystallisation of Glass Studied by Electron Backscatter Diffraction

PubMed Central

Wisniewski, Wolfgang; Patschger, Marek; Murdzheva, Steliana; Thieme, Christian; Rüssel, Christian

2016-01-01

Two glasses of the compositions 2 BaO - TiO2 - 2.75 GeO2 and 2 BaO – TiO2 –3.67 GeO2 (also known as BTG55) are annealed at temperatures from 680 to 970 °C to induce surface crystallization. The resulting samples are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD). Ge-Fresnoite (Ba2TiGe2O8, BTG) is observed at the immediate surface of all samples and oriented nucleation is proven in both compositions. After a very fast kinetic selection, the crystal growth of BTG into the bulk occurs via highly oriented dendrites where the c-axes are oriented perpendicular to the surface. The growth of this oriented layer is finally blocked by dendritc BTG originating from bulk nucleation. The secondary phases BaTiGe3O9 (benitoite) and BaGe4O9 are also identified near the surface by XRD and localized by EBSD which additionally indicates orientation preferences for these phases. This behaviour is in contrast with previous reports from the Ba2TiSi2O8 as well as the Sr2TiSi2O8 systems. PMID:26853738

Effects of coil orientation on the electric field induced by TMS over the hand motor area

NASA Astrophysics Data System (ADS)

Laakso, Ilkka; Hirata, Akimasa; Ugawa, Yoshikazu

2014-01-01

Responses elicited by transcranial magnetic stimulation (TMS) over the hand motor area depend on the position and orientation of the stimulating coil. In this work, we computationally investigate the induced electric field for multiple coil orientations and locations in order to determine which parts of the brain are affected and how the sensitivity of motor cortical activation depends on the direction of the electric field. The finite element method is used for calculating the electric field induced by TMS in two individual anatomical models of the head and brain. The orientation of the coil affects both the strength and depth of penetration of the electric field, and the field strongly depends on the direction of the sulcus, where the target neurons are located. The coil position that gives the strongest electric field in the target cortical region may deviate from the closest scalp location by a distance on the order of 1 cm. Together with previous experimental data, the results support the hypothesis that the cortex is most sensitive to fields oriented perpendicular to the cortical layers, while it is relatively insensitive to fields parallel to them. This has important implications for targeting of TMS. To determine the most effective coil position and orientation, it is essential to consider both biological (the direction of the targeted axons) and physical factors (the strength and direction of the electric field).

Statistical-mechanical analysis of self-organization and pattern formation during the development of visual maps

NASA Astrophysics Data System (ADS)

Obermayer, K.; Blasdel, G. G.; Schulten, K.

1992-05-01

We report a detailed analytical and numerical model study of pattern formation during the development of visual maps, namely, the formation of topographic maps and orientation and ocular dominance columns in the striate cortex. Pattern formation is described by a stimulus-driven Markovian process, the self-organizing feature map. This algorithm generates topologically correct maps between a space of (visual) input signals and an array of formal ``neurons,'' which in our model represents the cortex. We define order parameters that are a function of the set of visual stimuli an animal perceives, and we demonstrate that the formation of orientation and ocular dominance columns is the result of a global instability of the retinoptic projection above a critical value of these order parameters. We characterize the spatial structure of the emerging patterns by power spectra, correlation functions, and Gabor transforms, and we compare model predictions with experimental data obtained from the striate cortex of the macaque monkey with optical imaging. Above the critical value of the order parameters the model predicts a lateral segregation of the striate cortex into (i) binocular regions with linear changes in orientation preference, where iso-orientation slabs run perpendicular to the ocular dominance bands, and (ii) monocular regions with low orientation specificity, which contain the singularities of the orientation map. Some of these predictions have already been verified by experiments.

Effect of strain field on displacement cascade in tungsten studied by molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Wang, D.; Gao, N.; Wang, Z. G.; Gao, X.; He, W. H.; Cui, M. H.; Pang, L. L.; Zhu, Y. B.

2016-10-01

Using atomistic methods, the coupling effect of strain field and displacement cascade in body-centered cubic (BCC) tungsten is directly simulated by molecular dynamics (MD) simulations at different temperatures. The values of the hydrostatic and uniaxial (parallel or perpendicular to primary knock-on atom (PKA) direction) strains are from -2% to 2% and the temperature is from 100 to 1000 K. Because of the annealing effect, the influence of strain on radiation damage at low temperature has been proved to be more significant than that at high temperature. When the cascade proceeds under the hydrostatic strain, the Frenkel Pair (FP) production, the fraction of defect in cluster and the average size of the defect cluster, all increase at tensile state and decrease at compressive state. When the cascade is under uniaxial strain, the effect of strain parallel to PKA direction is less than the effect of hydrostatic strain, while the effect of strain perpendicular to PKA direction can be negligible. Under the uniaxial strain along <1 1 1> direction, the SIA and SIA cluster is observed to orientate along the strain direction at tensile state and the uniaxial compressive strain with direction perpendicular to <1 1 1> has led to the similar preferred nucleation. All these results indicate that under irradiation, the tensile state should be avoided for materials used in nuclear power plants.

Microstructure anisotropy of nanocrystalline titanium produced by cryomechanical grain fragmentation

NASA Astrophysics Data System (ADS)

Pohribnaya, Yu. M.; Moskalenko, V. A.; Braude, I. S.

2018-05-01

Using X-ray diffraction analysis, a systematic study was undertaken of the parameters of the deformation microstructure formed in commercially pure VT1-0 titanium as a result of cryogenic rolling at a temperature of 77 K at different degrees of compression. In order to ascertain the anisotropy of the microstructure, a comparative analysis of diffraction patterns, dimensions of crystallites (coherent scattering regions) L and microdeformation values ⟨" separators="| ɛ2 ⟩ 1 / 2 in the rolling plane and in a plane perpendicular to the rolling direction was performed by comparison with the relative activity of deformation modes. As a result, anisotropy was detected in the distribution of integral intensities of diffraction peaks for mutually perpendicular planes. The established difference in the dimensions of crystallites in the rolling plane and in the plane perpendicular to the rolling direction indicates the shape anisotropy of the crystallites. The effect of morphological anisotropy of crystallites/grains is most pronounced for the nanocrystalline state. The observed complex variation in the microdeformation values ⟨" separators="| ɛ2 ⟩ 1 / 2 ( e ) with compression deformation is well correlated with relative slip and twinning activity, which affect the level of local internal stresses and the possibility of their relaxation. The observed anisotropy with respect to the magnitude of microdeformations may be attributed to the presence of oriented grain boundaries associated with the shape anisotropy of crystallites/grains.

Evolution of the interfacial perpendicular magnetic anisotropy constant of the Co2FeAl/MgO interface upon annealing

NASA Astrophysics Data System (ADS)

Conca, A.; Niesen, A.; Reiss, G.; Hillebrands, B.

2018-04-01

We investigate a series of films with different thickness of the Heusler alloy Co2FeAl in order to study the effect of annealing on the interface with a MgO layer and on the bulk magnetic properties. Our results reveal that while the perpendicular interface anisotropy constant K\\perpS is zero for the as-deposited samples, its value increases with annealing up to a value of 1.14 +/- 0.07 mJ m‑2 for the series annealed at 320 °C and of 2.01 +/- 0.7 mJ m‑2 for the 450 °C annealed series owing to a strong modification of the interface during the thermal treatment. This large value ensures a stabilization of a perpendicular magnetization orientation for an extrapolated thickness below 1.7 nm. The data additionally shows that the in-plane biaxial anisotropy constant has a different evolution with thickness in as-deposited and annealed systems. The Gilbert damping parameter α shows minima for all series for a thickness of 40 nm and an absolute minimum value of 2.8+/-0.1×10-3 . The thickness dependence is explained in terms of an inhomogeneous magnetization state generated by the interplay between the different anisotropies of the system and by the crystalline disorder.

Simulation of silicon thin-film solar cells for oblique incident waves

NASA Astrophysics Data System (ADS)

Jandl, Christine; Hertel, Kai; Pflaum, Christoph; Stiebig, Helmut

2011-05-01

To optimize the quantum efficiency (QE) and short-circuit current density (JSC) of silicon thin-film solar cells, one has to study the behavior of sunlight in these solar cells. Simulations are an adequate and economic method to analyze the optical properties of light caused by absorption and reflection. To this end a simulation tool is developed to take several demands into account. These include the analysis of perpendicular and oblique incident waves under E-, H- and circularly polarized light. Furthermore, the topology of the nanotextured interfaces influences the efficiency and therefore also the short-circuit current density. It is well known that a rough transparent conductive oxide (TCO) layer increases the efficiency of solar cells. Therefore, it is indispensable that various roughness profiles at the interfaces of the solar cell layers can be modeled in such a way that atomic force microscope (AFM) scan data can be integrated. Numerical calculations of Maxwell's equations based on the finite integration technique (FIT) and Finite Difference Time Domain (FDTD) method are necessary to incorporate all these requirements. The simulations are performed in parallel on high performance computers (HPC) to meet the large computational requirements.

Aerodynamics of sports balls

NASA Astrophysics Data System (ADS)

Mehta, R. D.

Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

Aerodynamics of sports balls

NASA Technical Reports Server (NTRS)

Mehta, R. D.

1985-01-01

Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

Optimal conditions for particle-bubble attachment in flotation: an experimental study

NASA Astrophysics Data System (ADS)

Sanchez Yanez, Aaron; Hernandez Sanchez, Jose Federico; Thoroddsen, Sigurdur T.

2017-11-01

Mineral flotation is a process used in the mining industry for separating solid particles of different sizes and densities. The separation is done by injecting bubbles into a slurry where the particles attach to them, forming floating aggregates. The attachment depends mainly on the bubbles and particles sizes as well as the hydrophobicity and roughness of the particles. We simplified the collective behavior in the industrial process to a single free particle-bubble collision, in contrast with previous studies where one of the two was kept fixed. We experimentally investigated the collision of spherical solid particles of a fixed diameter with bubbles of different sizes. By controlling the initial relative offset of the bubble and the particle, we conducted experiments observing their interaction. Recording with two synchronized high-speed cameras, perpendicular to each other, we can reconstruct the tridimensional trajectories of the bubble, the solid particle, and the aggregate. We describe the conditions for which the attachment happens in terms of dimensionless parameters such as the Ohnesorge number, the relative particle-bubble offset and the hydrophobicity of the particle surface. We furthermore investigate the role of the surface roughness in the attachment.

Accounting for Fault Roughness in Pseudo-Dynamic Ground-Motion Simulations

NASA Astrophysics Data System (ADS)

Mai, P. Martin; Galis, Martin; Thingbaijam, Kiran K. S.; Vyas, Jagdish C.; Dunham, Eric M.

2017-09-01

Geological faults comprise large-scale segmentation and small-scale roughness. These multi-scale geometrical complexities determine the dynamics of the earthquake rupture process, and therefore affect the radiated seismic wavefield. In this study, we examine how different parameterizations of fault roughness lead to variability in the rupture evolution and the resulting near-fault ground motions. Rupture incoherence naturally induced by fault roughness generates high-frequency radiation that follows an ω-2 decay in displacement amplitude spectra. Because dynamic rupture simulations are computationally expensive, we test several kinematic source approximations designed to emulate the observed dynamic behavior. When simplifying the rough-fault geometry, we find that perturbations in local moment tensor orientation are important, while perturbations in local source location are not. Thus, a planar fault can be assumed if the local strike, dip, and rake are maintained. We observe that dynamic rake angle variations are anti-correlated with the local dip angles. Testing two parameterizations of dynamically consistent Yoffe-type source-time function, we show that the seismic wavefield of the approximated kinematic ruptures well reproduces the radiated seismic waves of the complete dynamic source process. This finding opens a new avenue for an improved pseudo-dynamic source characterization that captures the effects of fault roughness on earthquake rupture evolution. By including also the correlations between kinematic source parameters, we outline a new pseudo-dynamic rupture modeling approach for broadband ground-motion simulation.