Dynamic analysis of four bar planar mechanism extended to six-bar planar mechanism with variable topology

NASA Astrophysics Data System (ADS)

Belleri, Basayya K.; Kerur, Shravankumar B.

2018-04-01

A computer-oriented procedure for solving the dynamic force analysis problem for general planar mechanisms is presented. This paper provides position analysis, velocity analysis, acceleration analysis and force analysis of six bar mechanism with variable topology approach. Six bar mechanism is constructed by joining two simple four bar mechanisms. Initially the position, velocity and acceleration analysis of first four bar mechanism are determined by using the input parameters. The outputs (angular displacement, velocity and acceleration of rocker)of first four bar mechanism are used as input parameter for the second four bar mechanism and the position, velocity, acceleration and forces are analyzed. With out-put parameters of second four-bar mechanism the force analysis of first four-bar mechanism is carried out.

Method for directional hydraulic fracturing

DOEpatents

Swanson, David E.; Daly, Daniel W.

1994-01-01

A method for directional hydraulic fracturing using borehole seals to confine pressurized fluid in planar permeable regions, comprising: placing a sealant in the hole of a structure selected from geologic or cemented formations to fill the space between a permeable planar component and the geologic or cemented formation in the vicinity of the permeable planar component; making a hydraulic connection between the permeable planar component and a pump; permitting the sealant to cure and thereby provide both mechanical and hydraulic confinement to the permeable planar component; and pumping a fluid from the pump into the permeable planar component to internally pressurize the permeable planar component to initiate a fracture in the formation, the fracture being disposed in the same orientation as the permeable planar component.

Isolated planar gyroscope with internal radial sensing and actuation

NASA Technical Reports Server (NTRS)

Challoner, A. Dorian (Inventor); Shcheglov, Kirill V. (Inventor)

2006-01-01

The present invention discloses an inertial sensor comprising a planar mechanical resonator with embedded sensing and actuation for substantially in-plane vibration and having a central rigid support for the resonator. At least one excitation or torquer electrode is disposed within an interior of the resonator to excite in-plane vibration of the resonator and at least one sensing or pickoff electrode is disposed within the interior of the resonator for sensing the motion of the excited resonator. In one embodiment, the planar resonator includes a plurality of slots in an annular pattern; in another embodiment, the planar mechanical resonator comprises four masses; each embodiment having a simple degenerate pair of in-plane vibration modes.

Chemical-mechanical polishing of recessed microelectromechanical devices

DOEpatents

Barron, Carole C.; Hetherington, Dale L.; Montague, Stephen

1999-01-01

A method is disclosed for micromachining recessed layers (e.g. sacrificial layers) of a microelectromechanical system (MEMS) device formed in a cavity etched into a semiconductor substrate. The method uses chemical-mechanical polishing (CMP) with a resilient polishing pad to locally planarize one or more of the recessed layers within the substrate cavity. Such local planarization using the method of the present invention is advantageous for improving the patterning of subsequently deposited layers, for eliminating mechanical interferences between functional elements (e.g. linkages) of the MEMS device, and for eliminating the formation of stringers. After the local planarization of one or more of the recessed layers, another CMP step can be provided for globally planarizing the semiconductor substrate to form a recessed MEMS device which can be integrated with electronic circuitry (e.g. CMOS, BiCMOS or bipolar circuitry) formed on the surface of the substrate.

Chemical-mechanical polishing of recessed microelectromechanical devices

DOEpatents

Barron, C.C.; Hetherington, D.L.; Montague, S.

1999-07-06

A method is disclosed for micromachining recessed layers (e.g. sacrificial layers) of a microelectromechanical system (MEMS) device formed in a cavity etched into a semiconductor substrate. The method uses chemical-mechanical polishing (CMP) with a resilient polishing pad to locally planarize one or more of the recessed layers within the substrate cavity. Such local planarization using the method of the present invention is advantageous for improving the patterning of subsequently deposited layers, for eliminating mechanical interferences between functional elements (e.g. linkages) of the MEMS device, and for eliminating the formation of stringers. After the local planarization of one or more of the recessed layers, another CMP step can be provided for globally planarizing the semiconductor substrate to form a recessed MEMS device which can be integrated with electronic circuitry (e.g., CMOS, BiCMOS or bipolar circuitry) formed on the surface of the substrate. 23 figs.

Output Error Analysis of Planar 2-DOF Five-bar Mechanism

NASA Astrophysics Data System (ADS)

Niu, Kejia; Wang, Jun; Ting, Kwun-Lon; Tao, Fen; Cheng, Qunchao; Wang, Quan; Zhang, Kaiyang

2018-03-01

Aiming at the mechanism error caused by clearance of planar 2-DOF Five-bar motion pair, the method of equivalent joint clearance of kinematic pair to virtual link is applied. The structural error model of revolute joint clearance is established based on the N-bar rotation laws and the concept of joint rotation space, The influence of the clearance of the moving pair is studied on the output error of the mechanis. and the calculation method and basis of the maximum error are given. The error rotation space of the mechanism under the influence of joint clearance is obtained. The results show that this method can accurately calculate the joint space error rotation space, which provides a new way to analyze the planar parallel mechanism error caused by joint space.

Structure–Function Dissection of the Frizzled Receptor in Drosophila melanogaster Suggests Different Mechanisms of Action in Planar Polarity and Canonical Wnt Signaling

PubMed Central

Strutt, David; Madder, Daisy; Artymiuk, Peter J.

2012-01-01

Members of the Frizzled family of sevenpass transmembrane receptors signal via the canonical Wnt pathway and also via noncanonical pathways of which the best characterized is the planar polarity pathway. Activation of both canonical and planar polarity signaling requires interaction between Frizzled receptors and cytoplasmic proteins of the Dishevelled family; however, there has been some dispute regarding whether the Frizzled–Dishevelled interactions are the same in both cases. Studies looking at mutated forms of Dishevelled suggested that stable recruitment of Dishevelled to membranes by Frizzled was required only for planar polarity activity, implying that qualitatively different Frizzled–Dishevelled interactions underlie canonical signaling. Conversely, studies looking at the sequence requirements of Frizzled receptors in the fruit fly Drosophila melanogaster for canonical and planar polarity signaling have concluded that there is most likely a common mechanism of action. To understand better Frizzled receptor function, we have carried out a large-scale mutagenesis in Drosophila to isolate novel mutations in frizzled that affect planar polarity activity and have identified a group of missense mutations in cytosolic-facing regions of the Frizzled receptor that block Dishevelled recruitment. Interestingly, although some of these affect both planar polarity and canonical activity, as previously reported for similar lesions, we find a subset that affect only planar polarity activity. These results support the view that qualitatively different Frizzled–Dishevelled interactions underlie planar polarity and canonical Wnt signaling. PMID:23023003

Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating

NASA Astrophysics Data System (ADS)

Kuo, Ju-Nan; Chen, Kuan-Yu

2010-11-01

In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

Fabrication and Characterization of Planar Spring Based on FR4-PCB for Electrodynamics Vibration Energy Harvesting Application

NASA Astrophysics Data System (ADS)

Sugandi, Gandi; Mambu, Grace A.; Mulyadi, Dadang; Mulyana, Edi

2017-07-01

Planar spring as a mechanical resonator is very important in designing an electrodynamic vibration energy harvesting application (EVEH) to generate output power with high efficiency. Generally, component of the mechanical resonator is a cantilever beam that is designed using one cantilever with an inertial mass placed cantilever tip. In this study, a planar spring which has four arms cantilever beam was designed and fabricated using an extra-thin FR4-PCB material with a total thickness of 130 µm. There are four types of planar spring that were designed and fabricated in this research to produce resonant frequencies at about 30, 40, 50 and 60 Hz with 1 mm width cantilever arm and various length of 13.5, 11.2, 9.8 and 8.7 mm, respectively. FR4 resonator is fabricated using technology LASER-cutting in order to obtain results precisely. The resonant frequency generated by the mechanical resonator is characterized using vibrator system with certain acceleration. The resonant frequency of the planar spring was obtained at a frequency where the maximum induced voltage occurs. The resonant frequency generated by each type of planar spring was obtained at 24.81, 34.24, 40.2, and 46.8 Hz with three conditions of acceleration of 0.02, 0.06, and 0,1g (g=9.8 m/s2).

A flexible nanobrush pad for the chemical mechanical planarization of Cu/ultra-low-к materials

NASA Astrophysics Data System (ADS)

Han, Guiquan; Liu, Yuhong; Lu, Xinchun; Luo, Jianbin

2012-10-01

A new idea of polishing pad called flexible nanobrush pad (FNP) has been proposed for the low down pressure chemical mechanical planarization (CMP) process of Cu/ultra-low-к materials. The FNP was designed with a surface layer of flexible brush-like nanofibers which can `actively' carry nanoscale abrasives in slurry independent of the down pressure. Better planarization performances including high material removal rate, good planarization, good polishing uniformity, and low defectivity are expected in the CMP process under the low down pressure with such kind of pad. The FNP can be made by template-assisted replication or template-based synthesis methods, which will be driven by the development of the preparation technologies for ordered nanostructure arrays. The present work would potentially provide a new solution for the Cu/ultra-low-к CMP process.

Characterization of mechanical properties of pericardium tissue using planar biaxial tension and flexural deformation.

PubMed

Murdock, Kyle; Martin, Caitlin; Sun, Wei

2018-01-01

Flexure is an important mode of deformation for native and bioprosthetic heart valves. However, mechanical characterization of bioprosthetic leaflet materials has been done primarily through planar tensile testing. In this study, an integrated experimental and computational cantilever beam bending test was performed to characterize the flexural properties of glutaraldehyde-treated bovine and porcine pericardium of different thicknesses. A strain-invariant based structural constitutive model was used to model the pericardial mechanical behavior quantified through the bending tests of this study and the planar biaxial tests previously performed. The model parameters were optimized through an inverse finite element (FE) procedure in order to describe both sets of experimental data. The optimized material properties were implemented in FE simulations of transcatheter aortic valve (TAV) deformation. It was observed that porcine pericardium TAV leaflets experienced significantly more flexure than bovine when subjected to opening pressurization, and that the flexure may be overestimated using a constitutive model derived from purely planar tensile experimental data. Thus, modeling of a combination of flexural and biaxial tensile testing data may be necessary to more accurately describe the mechanical properties of pericardium, and to computationally investigate bioprosthetic leaflet function and design. Copyright © 2017 Elsevier Ltd. All rights reserved.

Quantum electromechanics on silicon nitride nanomembranes

PubMed Central

Fink, J. M.; Kalaee, M.; Pitanti, A.; Norte, R.; Heinzle, L.; Davanço, M.; Srinivasan, K.; Painter, O.

2016-01-01

Radiation pressure has recently been used to effectively couple the quantum motion of mechanical elements to the fields of optical or microwave light. Integration of all three degrees of freedom—mechanical, optical and microwave—would enable a quantum interconnect between microwave and optical quantum systems. We present a platform based on silicon nitride nanomembranes for integrating superconducting microwave circuits with planar acoustic and optical devices such as phononic and photonic crystals. Using planar capacitors with vacuum gaps of 60 nm and spiral inductor coils of micron pitch we realize microwave resonant circuits with large electromechanical coupling to planar acoustic structures of nanoscale dimensions and femtoFarad motional capacitance. Using this enhanced coupling, we demonstrate microwave backaction cooling of the 4.48 MHz mechanical resonance of a nanobeam to an occupancy as low as 0.32. These results indicate the viability of silicon nitride nanomembranes as an all-in-one substrate for quantum electro-opto-mechanical experiments. PMID:27484751

Quantum electromechanics on silicon nitride nanomembranes.

PubMed

Fink, J M; Kalaee, M; Pitanti, A; Norte, R; Heinzle, L; Davanço, M; Srinivasan, K; Painter, O

2016-08-03

Radiation pressure has recently been used to effectively couple the quantum motion of mechanical elements to the fields of optical or microwave light. Integration of all three degrees of freedom-mechanical, optical and microwave-would enable a quantum interconnect between microwave and optical quantum systems. We present a platform based on silicon nitride nanomembranes for integrating superconducting microwave circuits with planar acoustic and optical devices such as phononic and photonic crystals. Using planar capacitors with vacuum gaps of 60 nm and spiral inductor coils of micron pitch we realize microwave resonant circuits with large electromechanical coupling to planar acoustic structures of nanoscale dimensions and femtoFarad motional capacitance. Using this enhanced coupling, we demonstrate microwave backaction cooling of the 4.48 MHz mechanical resonance of a nanobeam to an occupancy as low as 0.32. These results indicate the viability of silicon nitride nanomembranes as an all-in-one substrate for quantum electro-opto-mechanical experiments.

Mechanical failure modes of chronically implanted planar silicon-based neural probes for laminar recording

PubMed Central

Kozai, Takashi D. Y.; Catt, Kasey; Li, Xia; Gugel, Zhannetta V.; Olafsson, Valur T.; Vazquez, Alberto L.; Cui, X. Tracy

2014-01-01

Penetrating intracortical electrode arrays that record brain activity longitudinally are powerful tools for basic neuroscience research and emerging clinical applications. However, regardless of the technology used, signals recorded by these electrodes degrade over time. The failure mechanisms of these electrodes are understood to be a complex combination of the biological reactive tissue response and material failure of the device over time. While mechanical mismatch between the brain tissue and implanted neural electrodes have been studied as a source of chronic inflammation and performance degradation, the electrode failure caused by mechanical mismatch between different material properties and different structural components within a device have remained poorly characterized. Using Finite Element Model (FEM) we simulate the mechanical strain on a planar silicon electrode. The results presented here demonstrate that mechanical mismatch between iridium and silicon leads to concentrated strain along the border of the two materials. This strain is further focused on small protrusions such as the electrical traces in planar silicon electrodes. These findings are confirmed with chronic in vivo data (133–189 days) in mice by correlating a combination of single-unit electrophysiology, evoked multi-unit recordings, electrochemical impedance spectroscopy, and scanning electron microscopy from traces and electrode sites with our modeling data. Several modes of mechanical failure of chronically implanted planar silicon electrodes are found that result in degradation and/or loss of recording. These findings highlight the importance of strains and material properties of various subcomponents within an electrode array. PMID:25453935

Comparison Of Planar And Wound Transformers For Flyback Forward And Half-Bridge Space Power Converters

NASA Astrophysics Data System (ADS)

Bjorklund, Thomas; Andreasen, John; Brosen, Finn; Matthiesen, Erik; Poulsen, Ole

2011-10-01

Planar technology has now entered the space domain. The big advantages of planar technology are; - Low profile - Excellent repeatability - Economical assembly - Mechanical integrity - Superior thermal characteristics This is why the general power industries increasingly are using planar magnetics in more and more applications, and therefore also why we see a rising demand for the usability of the planar technology among space application developers. The differences between wound and planar transformers have been mapped with a detailed look on the various parasitic component values, such as DC- and AC- resistance, Leakage Inductance and stray capacitance, and revealed the magnitude of the advantages of planar technology. This technical solution is proven in prototypes that have been built in different combination of PCB's and copper foil, with more or less interleaving of windings. Furthermore the transformers have been designed with several outputs stacked together with a fairly high number of primary turns, in order to have planar transformers similar to the wound types that are generally used for space applications.

Global geometry of non-planar 3-body motions

NASA Astrophysics Data System (ADS)

Salehani, Mahdi Khajeh

2011-12-01

The aim of this paper is to study the global geometry of non-planar 3-body motions in the realms of equivariant Differential Geometry and Geometric Mechanics. This work was intended as an attempt at bringing together these two areas, in which geometric methods play the major role, in the study of the 3-body problem. It is shown that the Euler equations of a three-body system with non-planar motion introduce non-holonomic constraints into the Lagrangian formulation of mechanics. Applying the method of undetermined Lagrange multipliers to study the dynamics of three-body motions reduced to the level of moduli space {bar{M}} subject to the non-holonomic constraints yields the generalized Euler-Lagrange equations of non-planar three-body motions in {bar{M}} . As an application of the derived dynamical equations in the level of {bar{M}} , we completely settle the question posed by A. Wintner in his book [The analytical foundations of Celestial Mechanics, Sections 394-396, 435 and 436. Princeton University Press (1941)] on classifying the constant inclination solutions of the three-body problem.

Fabrication of the planar angular rotator using the CMOS process

NASA Astrophysics Data System (ADS)

Dai, Ching-Liang; Chang, Chien-Liu; Chen, Hung-Lin; Chang, Pei-Zen

2002-05-01

In this investigation we propose a novel planar angular rotator fabricated by the conventional complementary metal-oxide semiconductor (CMOS) process. Following the 0.6 μm single poly triple metal (SPTM) CMOS process, the device is completed by a simple maskless, post-process etching step. The rotor of the planar angular rotator rotates around its geometric center with electrostatic actuation. The proposed design adopts an intelligent mechanism including the slider-crank system to permit simultaneous motion. The CMOS planar angular rotator could be driven with driving voltages of around 40 V. The design proposed here has a shorter response time and longer life, without problems of friction and wear, compared to the more common planar angular micromotor.

A flexible nanobrush pad for the chemical mechanical planarization of Cu/ultra-low-к materials

PubMed Central

2012-01-01

A new idea of polishing pad called flexible nanobrush pad (FNP) has been proposed for the low down pressure chemical mechanical planarization (CMP) process of Cu/ultra-low-к materials. The FNP was designed with a surface layer of flexible brush-like nanofibers which can ‘actively’ carry nanoscale abrasives in slurry independent of the down pressure. Better planarization performances including high material removal rate, good planarization, good polishing uniformity, and low defectivity are expected in the CMP process under the low down pressure with such kind of pad. The FNP can be made by template-assisted replication or template-based synthesis methods, which will be driven by the development of the preparation technologies for ordered nanostructure arrays. The present work would potentially provide a new solution for the Cu/ultra-low-к CMP process. PMID:23110959

On the genetic control of planar growth during tissue morphogenesis in plants.

PubMed

Enugutti, Balaji; Kirchhelle, Charlotte; Schneitz, Kay

2013-06-01

Tissue morphogenesis requires extensive intercellular communication. Plant organs are composites of distinct radial cell layers. A typical layer, such as the epidermis, is propagated by stereotypic anticlinal cell divisions. It is presently unclear what mechanisms coordinate cell divisions relative to the plane of a layer, resulting in planar growth and maintenance of the layer structure. Failure in the regulation of coordinated growth across a tissue may result in spatially restricted abnormal growth and the formation of a tumor-like protrusion. Therefore, one way to approach planar growth control is to look for genetic mutants that exhibit localized tumor-like outgrowths. Interestingly, plants appear to have evolved quite robust genetic mechanisms that govern these aspects of tissue morphogenesis. Here we provide a short summary of the current knowledge about the genetics of tumor formation in plants and relate it to the known control of coordinated cell behavior within a tissue layer. We further portray the integuments of Arabidopsis thaliana as an excellent model system to study the regulation of planar growth. The value of examining this process in integuments was established by the recent identification of the Arabidopsis AGC VIII kinase UNICORN as a novel growth suppressor involved in the regulation of planar growth and the inhibition of localized ectopic growth in integuments and other floral organs. An emerging insight is that misregulation of central determinants of adaxial-abaxial tissue polarity can lead to the formation of spatially restricted multicellular outgrowths in several tissues. Thus, there may exist a link between the mechanisms regulating adaxial-abaxial tissue polarity and planar growth in plants.

Method of producing an inertial sensor

NASA Technical Reports Server (NTRS)

Shcheglov, Kirill V. (Inventor); Challoner, A. Dorian (Inventor)

2008-01-01

The present invention discloses an inertial sensor comprising a planar mechanical resonator with embedded sensing and actuation for substantially in-plane vibration and having a central rigid support for the resonator. At least one excitation or torquer electrode is disposed within an interior of the resonator to excite in-plane vibration of the resonator and at least one sensing or pickoff electrode is disposed within the interior of the resonator for sensing the motion of the excited resonator. In one embodiment, the planar resonator includes a plurality of slots in an annular pattern; in another embodiment, the planar mechanical resonator comprises four masses; each embodiment having a simple degenerate pair of in-plane vibration modes.

Negative refraction and planar focusing based on parity-time symmetric metasurfaces.

PubMed

Fleury, Romain; Sounas, Dimitrios L; Alù, Andrea

2014-07-11

We introduce a new mechanism to realize negative refraction and planar focusing using a pair of parity-time symmetric metasurfaces. In contrast to existing solutions that achieve these effects with negative-index metamaterials or phase conjugating surfaces, the proposed parity-time symmetric lens enables loss-free, all-angle negative refraction and planar focusing in free space, without relying on bulk metamaterials or nonlinear effects. This concept may represent a pivotal step towards loss-free negative refraction and highly efficient planar focusing by exploiting the largely uncharted scattering properties of parity-time symmetric systems.

Chaos vibration of pinion and rack steering trapezoidal mechanism containing two clearances

NASA Astrophysics Data System (ADS)

Wei, Daogao; Wang, Yu; Jiang, Tong; Zheng, Sifa; Zhao, Wenjing; Pan, Zhijie

2017-08-01

The multi-clearances of breaking type steering trapezoidal mechanism joints influences vehicle steering stability. Hence, to ascertain the influence of clearance value on steering stability, this paper takes the steering mechanism of a certain vehicle type as a prototype that can be simplified into a planar six-bar linkage, then establishes the system dynamic differential equations after considering the two clearances of tie rods and the steering knuckle arms. The influence of the clearance parameters on the movement stability of the steering mechanism is studied using a numerical computation method. Results show that when the two clearances are equal, the planar movement of the tie rods changes from period-doubling to chaos as the clearances increase. When the two clearances are 0.25 mm and 1.5 mm respectively, the planar movements of the two side tie rods come into chaos, causing the steering stability to deteriorate. Moreover, with the increase of clearances, turning moment fluctuates more intensively and the peak value increases.

Gibbs–Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth

DOE PAGES

Shen, Youde; Chen, Renjie; Yu, Xuechao; ...

2016-06-02

Epitaxy-enabled bottom-up synthesis of self-assembled planar nanowires via the vapor–liquid–solid mechanism is an emerging and promising approach toward large-scale direct integration of nanowire-based devices without postgrowth alignment. In this paper, by examining large assemblies of indium tin oxide nanowires on yttria-stabilized zirconia substrate, we demonstrate for the first time that the growth dynamics of planar nanowires follows a modified version of the Gibbs–Thomson mechanism, which has been known for the past decades to govern the correlations between thermodynamic supersaturation, growth speed, and nanowire morphology. Furthermore, the substrate orientation strongly influences the growth characteristics of epitaxial planar nanowires as opposed tomore » impact at only the initial nucleation stage in the growth of vertical nanowires. The rich nanowire morphology can be described by a surface-energy-dependent growth model within the Gibbs–Thomson framework, which is further modulated by the tin doping concentration. Our experiments also reveal that the cutoff nanowire diameter depends on the substrate orientation and decreases with increasing tin doping concentration. Finally, these results enable a deeper understanding and control over the growth of planar nanowires, and the insights will help advance the fabrication of self-assembled nanowire devices.« less

Gibbs-Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth.

PubMed

Shen, Youde; Chen, Renjie; Yu, Xuechao; Wang, Qijie; Jungjohann, Katherine L; Dayeh, Shadi A; Wu, Tom

2016-07-13

Epitaxy-enabled bottom-up synthesis of self-assembled planar nanowires via the vapor-liquid-solid mechanism is an emerging and promising approach toward large-scale direct integration of nanowire-based devices without postgrowth alignment. Here, by examining large assemblies of indium tin oxide nanowires on yttria-stabilized zirconia substrate, we demonstrate for the first time that the growth dynamics of planar nanowires follows a modified version of the Gibbs-Thomson mechanism, which has been known for the past decades to govern the correlations between thermodynamic supersaturation, growth speed, and nanowire morphology. Furthermore, the substrate orientation strongly influences the growth characteristics of epitaxial planar nanowires as opposed to impact at only the initial nucleation stage in the growth of vertical nanowires. The rich nanowire morphology can be described by a surface-energy-dependent growth model within the Gibbs-Thomson framework, which is further modulated by the tin doping concentration. Our experiments also reveal that the cutoff nanowire diameter depends on the substrate orientation and decreases with increasing tin doping concentration. These results enable a deeper understanding and control over the growth of planar nanowires, and the insights will help advance the fabrication of self-assembled nanowire devices.

Mechanical Strain Determines Cilia Length, Motility, and Planar Position in the Left-Right Organizer.

PubMed

Chien, Yuan-Hung; Srinivasan, Shyam; Keller, Ray; Kintner, Chris

2018-05-07

The Xenopus left-right organizer (LRO) breaks symmetry along the left-right axis of the early embryo by producing and sensing directed ciliary flow as a patterning cue. To carry out this process, the LRO contains different ciliated cell types that vary in cilia length, whether they are motile or sensory, and how they position their cilia along the anterior-posterior (A-P) planar axis. Here, we show that these different cilia features are specified in the prospective LRO during gastrulation, based on anisotropic mechanical strain that is oriented along the A-P axis, and graded in levels along the medial-lateral axis. Strain instructs ciliated cell differentiation by acting on a mesodermal prepattern present at blastula stages, involving foxj1. We propose that differential strain is a graded, developmental cue, linking the establishment of an A-P planar axis to cilia length, motility, and planar location during formation of the Xenopus LRO. Copyright © 2018 Elsevier Inc. All rights reserved.

A Study of Phased Array Antennas for NASA's Deep Space Network

NASA Technical Reports Server (NTRS)

Jamnejad, Vahraz; Huang, John; Cesarone, Robert J.

2001-01-01

In this paper we briefly discuss various options but focus on the feasibility of the phased arrays as a viable option for this application. Of particular concern and consideration will be the cost, reliability, and performance compared to the present 70-meter antenna system, particularly the gain/noise temperature levels in the receive mode. Many alternative phased arrays including planar horizontal arrays, hybrid mechanically/electronically steered arrays, phased array of mechanically steered reflectors, multi-faceted planar arrays, phased array-fed lens antennas, and planar reflect-arrays are compared and their viability is assessed. Although they have many advantages including higher reliability, near-instantaneous beam switching or steering capability, the cost of such arrays is presently prohibitive and it is concluded that the only viable array options at the present are the arrays of a few or many small reflectors. The active planar phased arrays, however, may become feasible options in the next decade and can be considered for deployment in smaller configurations as supplementary options.

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks

PubMed Central

Yang, Ruiyue; Huang, Zhongwei; Yu, Wei; Li, Gensheng; Ren, Wenxi; Zuo, Lihua; Tan, Xiaosi; Sepehrnoori, Kamy; Tian, Shouceng; Sheng, Mao

2016-01-01

A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A “hump” that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the “hump” can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the “hump” more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production. PMID:27819349

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks.

PubMed

Yang, Ruiyue; Huang, Zhongwei; Yu, Wei; Li, Gensheng; Ren, Wenxi; Zuo, Lihua; Tan, Xiaosi; Sepehrnoori, Kamy; Tian, Shouceng; Sheng, Mao

2016-11-07

A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A "hump" that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the "hump" can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the "hump" more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production.

Sterically Hindered Square-Planar Nickel(II) Organometallic Complexes: Preparation, Characterization, and Substitution Behavior

ERIC Educational Resources Information Center

Martinez, Manuel; Muller, Guillermo; Rocamora, Merce; Rodriguez, Carlos

2007-01-01

The series of experiments proposed for advanced undergraduate students deal with both standard organometallic preparative methods in dry anaerobic conditions and with a kinetic study of the mechanisms operating in the substitution of square-planar complexes. The preparation of organometallic compounds is carried out by transmetallation or…

WHY DOES 5-METHYL CHRYSENE INTERACT WITH DNA LIKE BOTH A PLANAR AND A NON-PLANAR POLYCYCLIC AROMATIC HYDROCARBON? QUANTUM MECHANICAL STUDIES

EPA Science Inventory

Polycyclic aromatic hydrocarbons are a large class of anthropogenic chemicals found in the environment. Some class members are potent animal carcinogens while other similar class members show little carcinogenic activity. When considering a series of in vitro studies of the int...

COMPARATIVE STUDIES OF THE EFFECT OF POLYCYCLIC AROMATIC HYDROCARBON GEOMETRY ON THE HYDROLYSIS OF DIOL EPOXIDES

EPA Science Inventory

Comparative studies of the effect of polycyclic aromatic hydrocarbon geometry on the hydrolysis of diol epoxides

The interaction of the diol epoxides (DEs) of both planar and non-planar PAHs with water have been examined using quantum mechanical and molecular dynamics. Th...

Integral resonator gyroscope

NASA Technical Reports Server (NTRS)

Shcheglov, Kirill V. (Inventor); Challoner, A. Dorian (Inventor); Hayworth, Ken J. (Inventor); Wiberg, Dean V. (Inventor); Yee, Karl Y. (Inventor)

2008-01-01

The present invention discloses an inertial sensor having an integral resonator. A typical sensor comprises a planar mechanical resonator for sensing motion of the inertial sensor and a case for housing the resonator. The resonator and a wall of the case are defined through an etching process. A typical method of producing the resonator includes etching a baseplate, bonding a wafer to the etched baseplate, through etching the wafer to form a planar mechanical resonator and the wall of the case and bonding an end cap wafer to the wall to complete the case.

Method of producing an integral resonator sensor and case

NASA Technical Reports Server (NTRS)

Challoner, A. Dorian (Inventor); Yee, Karl Y. (Inventor); Shcheglov, Kirill V. (Inventor); Hayworth, Ken J. (Inventor); Wiberg, Dean V. (Inventor)

2005-01-01

The present invention discloses an inertial sensor having an integral resonator. A typical sensor comprises a planar mechanical resonator for sensing motion of the inertial sensor and a case for housing the resonator. The resonator and a wall of the case are defined through an etching process. A typical method of producing the resonator includes etching a baseplate, bonding a wafer to the etched baseplate, through etching the wafer to form a planar mechanical resonator and the wall of the case and bonding an end cap wafer to the wall to complete the case.

Constrained Quantum Mechanics: Chaos in Non-Planar Billiards

ERIC Educational Resources Information Center

Salazar, R.; Tellez, G.

2012-01-01

We illustrate some of the techniques to identify chaos signatures at the quantum level using as guiding examples some systems where a particle is constrained to move on a radial symmetric, but non-planar, surface. In particular, two systems are studied: the case of a cone with an arbitrary contour or "dunce hat billiard" and the rectangular…

Failure Mechanisms of GaAs Transistors - A Literature Survey

DTIC Science & Technology

1990-03-01

doping profile cannot be as sharp as with epitaxial methods. This is the result of the statistics of the implantation and the general diffusion that...Speed GaAs Logic Gates 5.1 GaAs PLANAR TRANSITOR STRUCTURES USED IN IC’S Some planar transistor structures used in IC’s with examples of the

Controllable curvature from planar polymer sheets in response to light.

PubMed

Hubbard, Amber M; Mailen, Russell W; Zikry, Mohammed A; Dickey, Michael D; Genzer, Jan

2017-03-22

The ability to change shape and control curvature in 3D structures starting from planar sheets can aid in assembly and add functionality to an object. Herein, we convert planar sheets of shape memory polymers (SMPs) into 3D objects with controllable curvature by dictating where the sheets shrink. Ink patterned on the surface of the sheet absorbs infrared (IR) light, resulting in localized heating, and the material shrinks locally wherever the temperature exceeds the activation temperature, T a . We introduce two different mechanisms for controlling curvature within SMP sheets. The 'direct' mechanism uses localized shrinkage to induce curvature only in regions patterned with ink. The 'indirect' mechanism uses localized shrinkage in regions patterned with ink to induce curvature in neighboring regions without ink through a balance of internal stresses. Finite element analysis predicts the final shape of the polymer sheets with excellent qualitative agreement with experimental studies. Results from this study show that curvature can be controlled by the distribution and darkness of the ink pattern on the polymer sheet. Additionally, we utilize the direct and indirect curvature mechanisms to demonstrate the formation and actuation of gripper devices, which represent the potential utility of this approach.

The way to zeros: The future of semiconductor device and chemical mechanical polishing technologies

NASA Astrophysics Data System (ADS)

Tsujimura, Manabu

2016-06-01

For the last 60 years, the development of cutting-edge semiconductor devices has strongly emphasized scaling; the effort to scale down current CMOS devices may well achieve the target of 5 nm nodes by 2020. Planarization by chemical mechanical polishing (CMP), is one technology essential for supporting scaling. This paper summarizes the history of CMP transitions in the planarization process as well as the changing degree of planarity required, and, finally, introduces innovative technologies to meet the requirements. The use of CMP was triggered by the replacement of local oxidation of silicon (LOCOS) as the element isolation technology by shallow trench isolation (STI) in the 1980s. Then, CMP’s use expanded to improving embedability of aluminum wiring, tungsten (W) contacts, Cu wiring, and, more recently, to its adoption in high-k metal gate (HKMG) and FinFET (FF) processes. Initially, the required degree of planarity was 50 nm, but now 0 nm is required. Further, zero defects on a post-CMP wafer is now the goal, and it is possible that zero psi CMP loading pressure will be required going forward. Soon, it seems, everything will have to be “zero” and perfect. Although the process is also chemical in nature, the CMP process is actually mechanical with a load added using slurry particles several tens of nm in diameter. Zero load in the loading process, zero nm planarity with no trace of processing, and zero residual foreign material, including the very slurry particles used in the process, are all required. This article will provide an overview of how to achieve these new requirements and what technologies should be employed.

Evanescent field refractometry in planar optical fiber.

PubMed

Holmes, Christopher; Jantzen, Alexander; Gray, Alan C; Gow, Paul C; Carpenter, Lewis G; Bannerman, Rex H S; Gates, James C; Smith, Peter G R

2018-02-15

This Letter demonstrates a refractometer in integrated optical fiber, a new optical platform that planarizes fiber using flame hydrolysis deposition (FHD). The unique advantage of the technology is survivability in harsh environments. The platform is mechanically robust, and can survive elevated temperatures approaching 1000°C and exposure to common solvents, including acetone, gasoline, and methanol. For the demonstrated refractometer, fabrication was achieved through wet etching an SMF-28 fiber to a diameter of 8 μm before FHD planarization. An external refractive index was monitored using fiber Bragg gratings (FBGs), written into the core of the planarized fiber. A direct comparison to alternative FBG refractometers is made, for which the developed platform is shown to have comparable sensitivity, with the added advantage of survivability in harsh environments.

Planarized thick copper gate polycrystalline silicon thin film transistors for ultra-large AMOLED displays

NASA Astrophysics Data System (ADS)

Yun, Seung Jae; Lee, Yong Woo; Son, Se Wan; Byun, Chang Woo; Reddy, A. Mallikarjuna; Joo, Seung Ki

2012-08-01

A planarized thick copper (Cu) gate low temperature polycrystalline silicon (LTPS) thin film transistors (TFTs) is fabricated for ultra-large active-matrix organic light-emitting diode (AMOLED) displays. We introduce a damascene and chemical mechanical polishing process to embed a planarized Cu gate of 500 nm thickness into a trench and Si3N4/SiO2 multilayer gate insulator, to prevent the Cu gate from diffusing into the silicon (Si) layer at 550°C, and metal-induced lateral crystallization (MILC) technology to crystallize the amorphous Si layer. A poly-Si TFT with planarized thick Cu gate exhibits a field effect mobility of 5 cm2/Vs and a threshold voltage of -9 V, and a subthreshold swing (S) of 1.4 V/dec.

Molecular filter based planar Doppler velocimetry

NASA Astrophysics Data System (ADS)

Elliott, Gregory S.; Beutner, Thomas J.

1999-11-01

Molecular filter based diagnostics are continuing to gain popularity as a research tool for investigations in areas of aerodynamics, fluid mechanics, and combustion. This class of diagnostics has gone by many terms including Filtered Rayleigh Scattering, Doppler Global Velocimetry, and Planar Doppler Velocimetry. The majority of this article reviews recent advances in Planar Doppler Velocimetry in measuring up to three velocity components over a planar region in a flowfield. The history of the development of these techniques is given with a description of typical systems, components, and levels of uncertainty in the measurement. Current trends indicate that uncertainties on the order of 1 m/s are possible with these techniques. A comprehensive review is also given on the application of Planar Doppler Velocimetry to laboratory flows, supersonic flows, and large scale subsonic wind tunnels. The article concludes with a description of future trends, which may simplify the technique, followed by a description of techniques which allow multi-property measurements (i.e. velocity, density, temperature, and pressure) simultaneously.

The core planar cell polarity gene prickle interacts with flamingo to promote sensory axon advance in the Drosophila embryo.

PubMed

Mrkusich, Eli M; Flanagan, Dustin J; Whitington, Paul M

2011-10-01

The atypical cadherin Drosophila protein Flamingo and its vertebrate homologues play widespread roles in the regulation of both dendrite and axon growth. However, little is understood about the molecular mechanisms that underpin these functions. Whereas flamingo interacts with a well-defined group of genes in regulating planar cell polarity, previous studies have uncovered little evidence that the other core planar cell polarity genes are involved in regulation of neurite growth. We present data in this study showing that the planar cell polarity gene prickle interacts with flamingo in regulating sensory axon advance at a key choice point - the transition between the peripheral nervous system and the central nervous system. The cytoplasmic tail of the Flamingo protein is not required for this interaction. Overexpression of another core planar cell polarity gene dishevelled produces a similar phenotype to prickle mutants, suggesting that this gene may also play a role in regulation of sensory axon advance. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

The core planar cell polarity gene, Vangl2, maintains apical-basal organisation of the corneal epithelium.

PubMed

Panzica, D Alessio; Findlay, Amy S; van Ladesteijn, Rianne; Collinson, J Martin

2017-08-17

The role of the core planar cell polarity (PCP) pathway protein, Vangl2, was investigated in the corneal epithelium of the mammalian eye, a paradigm anatomical model of planar cell migration. The gene was conditionally knocked out in vivo and knocked down by siRNA, followed by immunohistochemical, behavioural and morphological analysis of corneal epithelial cells. The primary defects observed in vivo were of apical-basal organisation of the corneal epithelium, with abnormal stratification throughout life, mislocalisation of the cell membrane protein, Scribble, to the basal side of cells, and partial loss of the epithelial basement membrane. Planar defects in migration after wounding and in the presence of an applied electric field were noted. However, knockdown of Vangl2 also retarded cell migration in individual cells that had no contact with their neighbours, which precluded a classic PCP mechanism. It is concluded that some of the planar polarity phenotypes in PCP mutants may arise from disruption of apical-basal polarity. © 2017 Anatomical Society.

Use of chemical mechanical polishing in micromachining

DOEpatents

Nasby, Robert D.; Hetherington, Dale L.; Sniegowski, Jeffry J.; McWhorter, Paul J.; Apblett, Christopher A.

1998-01-01

A process for removing topography effects during fabrication of micromachines. A sacrificial oxide layer is deposited over a level containing functional elements with etched valleys between the elements such that the sacrificial layer has sufficient thickness to fill the valleys and extend in thickness upwards to the extent that the lowest point on the upper surface of the oxide layer is at least as high as the top surface of the functional elements in the covered level. The sacrificial oxide layer is then polished down and planarized by chemical-mechanical polishing. Another layer of functional elements is then formed upon this new planarized surface.

Role of Slip Mode on Stress Corrosion Cracking Behavior

NASA Astrophysics Data System (ADS)

Vasudevan, A. K.; Sadananda, K.

2011-02-01

In this article, we examine the effect of aging treatment and the role of planarity of slip on stress corrosion cracking (SCC) behavior in precipitation-hardened alloys. With aging, the slip mode can change from a planar slip in the underage (UA) to a wavy slip in the overage (OA) region. This, in turn, results in sharpening the crack tip in the UA compared to blunting in the OA condition. We propose that the planar slip enhances the stress concentration effects by making the alloys more susceptible to SCC. In addition, the planarity of slip enhances plateau velocities, reduces thresholds for SCC, and reduces component life. We show that the effect of slip planarity is somewhat similar to the effects of mechanically induced stress concentrations such as due to the presence of sharp notches. Aging treatment also causes variations in the matrix and grain boundary (GB) microstructures, along with typical mechanical and SCC properties. These properties include yield stress, work hardening rate, fracture toughness K IC , thresholds K Iscc, and steady-state plateau velocity ( da/ dt). The SCC data for a wide range of ductile alloys including 7050, 7075, 5083, 5456 Al, MAR M steels, and solid solution copper-base alloys are collected from the literature. Our assertion is that slip mode and the resulting stress concentration are important factors in SCC behavior. This is further supported by similar observations in many other systems including some steels, Al alloys, and Cu alloys.

Paving the Way Towards Reactive Planar Spanner Construction in Wireless Networks

NASA Astrophysics Data System (ADS)

Frey, Hannes; Rührup, Stefan

A spanner is a subgraph of a given graph that supports the original graph's shortest path lengths up to a constant factor. Planar spanners and their distributed construction are of particular interest for geographic routing, which is an efficient localized routing scheme for wireless ad hoc and sensor networks. Planarity of the network graph is a key criterion for guaranteed delivery, while the spanner property supports efficiency in terms of path length. We consider the problem of reactive local spanner construction, where a node's local topology is determined on demand. Known message-efficient reactive planarization algorithms do not preserve the spanner property, while reactive spanner constructions with a low message overhead have not been described so far. We introduce the concept of direct planarization which may be an enabler of efficient reactive spanner construction. Given an edge, nodes check for all incident intersecting edges a certain geometric criterion and withdraw the edge if this criterion is not satisfied. We use this concept to derive a generic reactive topology control mechanism and consider two geometric criteria. Simulation results show that direct planarization increases the performance of localized geographic routing by providing shorter paths than existing reactive approaches.

The opercular mouth-opening mechanism of largemouth bass functions as a 3D four-bar linkage with three degrees of freedom.

PubMed

Olsen, Aaron M; Camp, Ariel L; Brainerd, Elizabeth L

2017-12-15

The planar, one degree of freedom (1-DoF) four-bar linkage is an important model for understanding the function, performance and evolution of numerous biomechanical systems. One such system is the opercular mechanism in fishes, which is thought to function like a four-bar linkage to depress the lower jaw. While anatomical and behavioral observations suggest some form of mechanical coupling, previous attempts to model the opercular mechanism as a planar four-bar have consistently produced poor model fits relative to observed kinematics. Using newly developed, open source mechanism fitting software, we fitted multiple three-dimensional (3D) four-bar models with varying DoF to in vivo kinematics in largemouth bass to test whether the opercular mechanism functions instead as a 3D four-bar with one or more DoF. We examined link position error, link rotation error and the ratio of output to input link rotation to identify a best-fit model at two different levels of variation: for each feeding strike and across all strikes from the same individual. A 3D, 3-DoF four-bar linkage was the best-fit model for the opercular mechanism, achieving link rotational errors of less than 5%. We also found that the opercular mechanism moves with multiple degrees of freedom at the level of each strike and across multiple strikes. These results suggest that active motor control may be needed to direct the force input to the mechanism by the axial muscles and achieve a particular mouth-opening trajectory. Our results also expand the versatility of four-bar models in simulating biomechanical systems and extend their utility beyond planar or single-DoF systems. © 2017. Published by The Company of Biologists Ltd.

FIBRE AND INTEGRATED OPTICS. OPTICAL PROCESSING OF INFORMATION: Mechanism of lock-in detection with the aid of an alternating field perpendicular to the surface of a planar photorefractive waveguide

NASA Astrophysics Data System (ADS)

Zel'dovich, Boris Ya; Miklyaev, Yu V.; Safonov, V. I.

1995-02-01

An analysis is made of the mechanism of formation of a stationary grating in a planar photorefractive waveguide by a travelling interference pattern with the aid of an alternating electric field applied perpendicular to the waveguide layer. A theoretical calculation is reported of the distribution of the space-charge field in a transverse section of the waveguide. Finite drift lengths and trap saturation are taken into account in these calculations, which are carried out on the assumption of a weak contrast in the interference pattern.

Phase Diagram of Planar Matrix Quantum Mechanics, Tensor, and Sachdev-Ye-Kitaev Models.

PubMed

Azeyanagi, Tatsuo; Ferrari, Frank; Massolo, Fidel I Schaposnik

2018-02-09

We study the Schwinger-Dyson equations of a fermionic planar matrix quantum mechanics [or tensor and Sachdev-Ye-Kitaev (SYK) models] at leading melonic order. We find two solutions describing a high entropy, SYK black-hole-like phase and a low entropy one with trivial IR behavior. There is a line of first order phase transitions that terminates at a new critical point. Critical exponents are nonmean field and differ on the two sides of the transition. Interesting phenomena are also found in unstable and stable bosonic models, including Kazakov critical points and inconsistency of SYK-like solutions of the IR limit.

Propulsion of flexible polymer structures in a rotating magnetic field.

PubMed

Garstecki, Piotr; Tierno, Pietro; Weibel, Douglas B; Sagués, Francesc; Whitesides, George M

2009-05-20

We demonstrate a new concept for the propulsions of abiological structures at low Reynolds numbers. The approach is based on the design of flexible, planar polymer structures with a permanent magnetic moment. In the presence of an external, uniform, rotating magnetic field these structures deform into three-dimensional shapes that have helical symmetry and translate linearly through fluids at Re between 10(-1) and 10. The mechanism for the motility of these structures involves reversible deformation that breaks their planar symmetry and generates propulsion. These elastic propellers resemble microorganisms that use rotational mechanisms based on flagella and cilia for their motility in fluids at low Re.

Use of chemical mechanical polishing in micromachining

DOEpatents

Nasby, R.D.; Hetherington, D.L.; Sniegowski, J.J.; McWhorter, P.J.; Apblett, C.A.

1998-09-08

A process for removing topography effects during fabrication of micromachines. A sacrificial oxide layer is deposited over a level containing functional elements with etched valleys between the elements such that the sacrificial layer has sufficient thickness to fill the valleys and extend in thickness upwards to the extent that the lowest point on the upper surface of the oxide layer is at least as high as the top surface of the functional elements in the covered level. The sacrificial oxide layer is then polished down and planarized by chemical-mechanical polishing. Another layer of functional elements is then formed upon this new planarized surface. 4 figs.

Electrochemical-mechanical coupling in composite planar structures that integrate flow channels and ion-conducting membranes

DOE PAGES

Euser, Bryan Jeffry; Zhu, Huayang; Berger, John; ...

2017-01-01

Ceramic oxygen-transport membranes, such as the doped perovskite La 0.6Sr 0.4Co 0.8Fe 0.2O 3-δ(LSCF6482) considered in the present paper, are effective in applications such as air separation. The present paper considers a planar configuration that is composed of a thin (order tens of microns) ion-transport membrane, a relatively thick (order millimeter) porous-ceramic support structure, and millimeter-scale oxygen-collection flow channels. The lattice-scale strain associated with charged defects (oxygen vacancies and small polarons) within ion-transport membranes causes macroscopic stress that could distort or damage the assembly. The modeling approach is based on an extended twodimensional Nernst–Planck–Poisson (NPP) formulation that is developed andmore » applied to evaluate the effects of chemically induced stress within a planar oxygen-separation assembly. The computational model predicts two-dimensional distributions of steady-state defect concentrations, electrostatic potentials, and stress. Parameter studies consider the effects of support-membrane dimensions, materials mechanical properties, and operating conditions. Although the stress is found to have a negligible influence on the defect transport, the defect transport is found to significantly affect the stress distributions. Such results can play important roles in the design and development of planar ion-transport membranes and their support structures.« less

Investigation of the in-plane and out-of-plane electrical properties of metallic nanoparticles in dielectric matrix thin films elaborated by atomic layer deposition

NASA Astrophysics Data System (ADS)

Thomas, D.; Puyoo, E.; Le Berre, M.; Militaru, L.; Koneti, S.; Malchère, A.; Epicier, T.; Roiban, L.; Albertini, D.; Sabac, A.; Calmon, F.

2017-11-01

Pt nanoparticles in a Al2O3 dielectric matrix thin films are elaborated by means of atomic layer deposition. These nanostructured thin films are integrated in vertical and planar test structures in order to assess both their in-plane and out-of-plane electrical properties. A shadow edge evaporation process is used to develop planar devices with electrode separation distances in the range of 30 nm. Both vertical and planar test structures show a Poole-Frenkel conduction mechanism. Low trap energy levels (<0.1 eV) are identified for the two test structures which indicates that the Pt islands themselves are not acting as traps in the PF mechanism. Furthermore, a more than three order of magnitude current density difference is observed between the two geometries. This electrical anisotropy is attributed to a large electron mobility difference in the in-plane and out-of-plane directions which can be related to different trap distributions in both directions.

Echo planar imaging at 4 Tesla with minimum acoustic noise.

PubMed

Tomasi, Dardo G; Ernst, Thomas

2003-07-01

To minimize the acoustic sound pressure levels of single-shot echo planar imaging (EPI) acquisitions on high magnetic field MRI scanners. The resonance frequencies of gradient coil vibrations, which depend on the coil length and the elastic properties of the materials in the coil assembly, were measured using piezoelectric transducers. The frequency of the EPI-readout train was adjusted to avoid the frequency ranges of mechanical resonances. Our MRI system exhibited two sharp mechanical resonances (at 720 and 1220 Hz) that can increase vibrational amplitudes up to six-fold. A small adjustment of the EPI-readout frequency made it possible to reduce the sound pressure level of EPI-based perfusion and functional MRI scans by 12 dB. Normal vibrational modes of MRI gradient coils can dramatically increase the sound pressure levels during echo planar imaging (EPI) scans. To minimize acoustic noise, the frequency of EPI-readout trains and the resonance frequencies of gradient coil vibrations need to be different. Copyright 2003 Wiley-Liss, Inc.

A fracture mechanics study of the phase separating planar electrodes: Phase field modeling and analytical results

NASA Astrophysics Data System (ADS)

Haftbaradaran, H.; Maddahian, A.; Mossaiby, F.

2017-05-01

It is well known that phase separation could severely intensify mechanical degradation and expedite capacity fading in lithium-ion battery electrodes during electrochemical cycling. Experiments have frequently revealed that such degradation effects could be substantially mitigated via reducing the electrode feature size to the nanoscale. The purpose of this work is to present a fracture mechanics study of the phase separating planar electrodes. To this end, a phase field model is utilized to predict how phase separation affects evolution of the solute distribution and stress profile in a planar electrode. Behavior of the preexisting flaws in the electrode in response to the diffusion induced stresses is then examined via computing the time dependent stress intensity factor arising at the tip of flaws during both the insertion and extraction half-cycles. Further, adopting a sharp-interphase approximation of the system, a critical electrode thickness is derived below which the phase separating electrode becomes flaw tolerant. Numerical results of the phase field model are also compared against analytical predictions of the sharp-interphase model. The results are further discussed with reference to the available experiments in the literature. Finally, some of the limitations of the model are cautioned.

Whole-Cell Electrical Activity Under Direct Mechanical Stimulus by AFM Cantilever Using Planar Patch Clamp Chip Approach

PubMed Central

Upadhye, Kalpesh V.; Candiello, Joseph E.; Davidson, Lance A.; Lin, Hai

2011-01-01

Patch clamp is a powerful tool for studying the properties of ion-channels and cellular membrane. In recent years, planar patch clamp chips have been fabricated from various materials including glass, quartz, silicon, silicon nitride, polydimethyl-siloxane (PDMS), and silicon dioxide. Planar patch clamps have made automation of patch clamp recordings possible. However, most planar patch clamp chips have limitations when used in combination with other techniques. Furthermore, the fabrication methods used are often expensive and require specialized equipments. An improved design as well as fabrication and characterization of a silicon-based planar patch clamp chip are described in this report. Fabrication involves true batch fabrication processes that can be performed in most common microfabrication facilities using well established MEMS techniques. Our planar patch clamp chips can form giga-ohm seals with the cell plasma membrane with success rate comparable to existing patch clamp techniques. The chip permits whole-cell voltage clamp recordings on variety of cell types including Chinese Hamster Ovary (CHO) cells and pheochromocytoma (PC12) cells, for times longer than most available patch clamp chips. When combined with a custom microfluidics chamber, we demonstrate that it is possible to perfuse the extra-cellular as well as intra-cellular buffers. The chamber design allows integration of planar patch clamp with atomic force microscope (AFM). Using our planar patch clamp chip and microfluidics chamber, we have recorded whole-cell mechanosensitive (MS) currents produced by directly stimulating human keratinocyte (HaCaT) cells using an AFM cantilever. Our results reveal the spatial distribution of MS ion channels and temporal details of the responses from MS channels. The results show that planar patch clamp chips have great potential for multi-parametric high throughput studies of ion channel proteins. PMID:22174731

Development of advanced second-generation micromirror devices fabricated in a four-level planarized surface-micromachined polycrystalline silicon process

NASA Astrophysics Data System (ADS)

Michalicek, M. Adrian; Comtois, John H.; Schriner, Heather K.

1998-04-01

This paper describes the design and characterization of several types of micromirror devices to include process capabilities, device modeling, and test data resulting in deflection versus applied potential curves and surface contour measurements. These devices are the first to be fabricated in the state-of-the-art four-level planarized polysilicon process available at Sandia National Laboratories known as the Sandia Ultra-planar Multi-level MEMS Technology. This enabling process permits the development of micromirror devices with near-ideal characteristics which have previously been unrealizable in standard three-layer polysilicon processes. This paper describes such characteristics which have previously been unrealizable in standard three-layer polysilicon processes. This paper describes such characteristics as elevated address electrodes, various address wiring techniques, planarized mirror surfaces suing Chemical Mechanical Polishing, unique post-process metallization, and the best active surface area to date.

Parametric study of the mode coupling instability for a simple system with planar or rectilinear friction

NASA Astrophysics Data System (ADS)

Charroyer, L.; Chiello, O.; Sinou, J.-J.

2016-12-01

In this paper, the study of a damped mass-spring system of three degrees of freedom with friction is proposed in order to highlight the differences in mode coupling instabilities between planar and rectilinear friction assumptions. Well-known results on the effect of structural damping in the field of friction-induced vibration are extended to the specific case of a damped mechanical system with planar friction. It is emphasised that the lowering and smoothing effects are not so intuitive in this latter case. The stability analysis is performed by calculating the complex eigenvalues of the linearised system and by using the Routh-Hurwitz criterion. Parametric studies are carried out in order to evaluate the effects of various system parameters on stability. Special attention is paid to the understanding of the role of damping and the associated destabilisation paradox in mode-coupling instabilities with planar and rectilinear friction assumptions.

Chaotic non-planar vibrations of the thin elastica. Part I: Experimental observation of planar instability

NASA Astrophysics Data System (ADS)

Cusumano, J. P.; Moon, F. C.

1995-01-01

In this two-part paper, the results of an investigation into the non-linear dynamics of a flexible cantilevered rod (the elastica) with a thin rectangular cross-section are presented. An experimental examination of the dynamics of the elastica over a broad parameter range forms the core of Part I. In Part II, the experimental work is related to a theoretical study of the mechanics of the elastica, and the study of a two-degree-of-freedom model obtained by modal projection. The experimental system used in this investigation is a rod with clamped-free boundary conditions, forced by sinusoidally displacing the clamped end. Planar periodic motions of the driven elastica are shown to lose stability at distinct resonant wedges, and the resulting motions are shown in general to be non-planar, chaotic, bending-torsion oscillations. Non-planar motions in all resonances exhibit energy cascading and dynamic two-well phenomena, and a family of asymmetric, bending-torsion non-linear modes is discovered. Correlation dimension calculations are used to estimate the number of active degrees of freedom in the system.

Dynamic structure of confined shocks undergoing sudden expansion

NASA Astrophysics Data System (ADS)

Abate, G.; Shyy, W.

2002-01-01

The gas dynamic phenomenon associated with a normal shock wave within a tube undergoing a sudden area expansion consists of highly transient flow and diffraction that give rise to turbulent, compressible, vortical flows. These interactions can occur at time scales typically ranging from micro- to milliseconds. In this article, we review recent experimental and numerical results to highlight the flow phenomena and main physical mechanisms associated with this geometry. The topics addressed include time-accurate shock and vortex locations, flowfield evolution and structure, wall-shock Mach number, two- vs. three-dimensional sudden expansions, and the effect of viscous dissipation on planar shock-front expansions. Between axisymmetric and planar geometries, the flow structure evolves very similarly early on in the sudden expansion process (i.e., within the first two shock tube diameters). Both numerical and experimental studies confirm that the trajectory of the vortex formed at the expansion corner is convected into the flowfield faster in the axisymmetric case than the planar case. The lateral propagation of the vortices correlates very well between axisymmetric and planar geometries. In regard to the rate of dissipation of turbulent kinetic energy (TKE) for a two-dimensional planar shock undergoing a sudden expansion within a confined chamber, calculations show that the solenoidal dissipation is confined to the region of high strain rates arising from the expansion corner. Furthermore, the dilatational dissipation is concentrated mainly at the curvature of the incident, reflected, and barrel shock fronts. The multiple physical mechanisms identified, including shock-strain rate interaction, baroclinic effect, vorticity generation, and different aspects of viscous dissipation, have produced individual and collective flow structures observed experimentally.

Performance improvement of planar dielectric elastomer actuators by magnetic modulating mechanism

NASA Astrophysics Data System (ADS)

Zhao, Yun-Hua; Li, Wen-Bo; Zhang, Wen-Ming; Yan, Han; Peng, Zhi-Ke; Meng, Guang

2018-06-01

In this paper, a novel planar dielectric elastomer actuator (DEA) with magnetic modulating mechanism is proposed. This design can provide the availability of wider actuation range and larger output force, which are significant indicators to evaluate the performance of DEAs. The DEA tends to be a compact and simple design, and an analytical model is developed to characterize the mechanical behavior. The result shows that the output force induced by the DEA can be improved by 76.90% under a certain applied voltage and initial magnet distance. Moreover, experiments are carried out to reveal the performance of the proposed DEA and validate the theoretical model. It demonstrates that the DEA using magnetic modulating mechanism can enlarge the actuation range and has more remarkable effect with decreasing initial magnet distance within the stable range. It can be useful to promote the applications of DEAs to soft robots and haptic feedback.

Complexion-mediated martensitic phase transformation in Titanium

PubMed Central

Zhang, J.; Tasan, C. C.; Lai, M. J.; Dippel, A. -C.; Raabe, D.

2017-01-01

The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations. Examples are shape memory alloys and high strength steels, which together stand for 1,500 million tons annual production. In these materials, martensite formation and mechanical twinning are tuned via composition adjustment for realizing complex microstructures and beneficial mechanical properties. Here we report a new phase transformation that has the potential to widen the application window of Ti alloys, the most important structural material in aerospace design, by nanostructuring them via complexion-mediated transformation. This is a reversible martensitic transformation mechanism that leads to a final nanolaminate structure of α″ (orthorhombic) martensite bounded with planar complexions of athermal ω (a–ω, hexagonal). Both phases are crystallographically related to the parent β (BCC) matrix. As expected from a planar complexion, the a–ω is stable only at the hetero-interface. PMID:28145484

Complexion-mediated martensitic phase transformation in Titanium.

PubMed

Zhang, J; Tasan, C C; Lai, M J; Dippel, A-C; Raabe, D

2017-02-01

The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations. Examples are shape memory alloys and high strength steels, which together stand for 1,500 million tons annual production. In these materials, martensite formation and mechanical twinning are tuned via composition adjustment for realizing complex microstructures and beneficial mechanical properties. Here we report a new phase transformation that has the potential to widen the application window of Ti alloys, the most important structural material in aerospace design, by nanostructuring them via complexion-mediated transformation. This is a reversible martensitic transformation mechanism that leads to a final nanolaminate structure of α″ (orthorhombic) martensite bounded with planar complexions of athermal ω (a-ω, hexagonal). Both phases are crystallographically related to the parent β (BCC) matrix. As expected from a planar complexion, the a-ω is stable only at the hetero-interface.

Interaction of planar and nonplanar organic contaminants with coal fly ash: effects of polar and nonpolar solvent solutions.

PubMed

Burgess, Robert M; Ryba, Stephan A; Cantwell, Mark G; Gundersen, Jennifer L; Tien, Rex; Perron, Monique M

2006-08-01

Coal fly ash has a very high sorption capacity for a variety of anthropogenic contaminants and has been used to cleanse wastewater of pollutants for approximately 40 years. Like other black carbons, the planar structure of the residual carbon in fly ash results in elevated affinities for planar organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and some polychlorinated biphenyls (PCBs). The present study was performed to understand better the mechanisms affecting the strong interaction between planar contaminants and coal fly ash. The removal of 10 PCBs and 10 PAHs by several fly ashes and other sorbents was evaluated under different experimental conditions to highlight the intermolecular forces influencing adsorption. Varying fly ash concentration and solvent system composition indicated that dispersive interactions were most prevalent. For the PCBs, empirical results also were compared to molecular modeling estimates of the energy necessary for the PCB molecule to assume a planar conformation (PCe). The PCe levels ranged from 8 to 25 kcal/mol, depending on the degree of ortho-substituted chlorination of the PCB. A significant correlation between PCe and PCB removal from solution was observed for the fly ashes and activated carbon, whereas the nonplanar sorbent octadecyl (C18) indicated no relationship. These findings demonstrate the strong interaction between black carbon fly ash and planar organic contaminants. Furthermore, as exemplified by the PCBs, these results show how this interaction is a function of a contaminant's ability to assume a planar conformation.

Designing with figer-reinforced plastics (planar random composites)

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1982-01-01

The use of composite mechanics to predict the hygrothermomechanical behavior of planar random composites (PRC) is reviewed and described. These composites are usually made from chopped fiber reinforced resins (thermoplastics or thermosets). The hygrothermomechanical behavior includes mechanical properties, physical properties, thermal properties, fracture toughness, creep and creep rupture. Properties are presented in graphical form with sample calculations to illustrate their use. Concepts such as directional reinforcement and strip hybrids are described. Typical data that can be used for preliminary design for various PRCs are included. Several resins and molding compounds used to make PRCs are described briefly. Pertinent references are cited that cover analysis and design methods, materials, data, fabrication procedures and applications.

Virtual Metrology applied in Run-to-Run Control for a Chemical Mechanical Planarization process

NASA Astrophysics Data System (ADS)

Jebri, M. A.; El Adel, E. M.; Graton, G.; Ouladsine, M.; Pinaton, J.

2017-01-01

This paper deals with missing data in semiconductor manufacturing derived from a measurement sampling strategies. The idea is to construct a virtual metrology module to estimate non measured variables using a new modified Just-In-Time Learning approach (JITL). The aim of this paper is to integrate estimated data into product control loop. In collaboration with our industrial partner STMicroelectronics Rousset, the accuracy of the proposed method is illustrated by using industrial data-sets derived from Chemical Mechanical Planarization (CMP) process that enables us to compare results obtained with the classical and the modified version of JITL approach. Then, the contribution of the estimated data is shown in product quality improvement.

Characterization of printed planar electromagnetic coils using digital extrusion and roll-to-roll flexographic processes

NASA Astrophysics Data System (ADS)

Rickard, Scott

Electromagnets are a crucial component in a wide range of more complex electrical devices due to their ability to turn electrical energy into mechanical energy and vice versa. The trend for electronics becoming smaller and lighter has led to increased interest in using flat, planar electromagnetic coils, which have been shown to perform better at scaled down sizes. The two-dimensional geometry of a planar electromagnetic coil yields itself to be produced by a roll-to-roll additive manufacturing process. The emergence of the printed electronics field, which uses traditional printing processes to pattern functional inks, has led to new methods of mass-producing basic electrical components. The ability to print a planar electromagnetic coil using printed electronics could rival the traditional subtractive and semi-subtractive PCB process of manufacturing. The ability to print lightweight planar electromagnetic coils on flexible substrates could lead to their inclusion into intelligent packaging applications and could have specific use in actuating devices, transformers, and electromagnetic induction applications such as energy harvesting or wireless charging. In attempts to better understand the limitations of printing planar electromagnetic coils, the effect that the design parameters of the planar coils have on the achievable magnetic field strength were researched. A comparison between prototyping methods of digital extrusion and manufacturing scale flexographic printing are presented, discussing consistency in the printed coils and their performance in generating magnetic fields. A method to predict the performance of these planar coils is introduced to allow for design within required needs of an application. Results from the research include a demonstration of a printed coil being used in a flat speaker design, working off of actuating principles.

Millimeter And Submillimeter-Wave Integrated Circuits On Quartz

NASA Technical Reports Server (NTRS)

Mehdi, Imran; Mazed, Mohammad; Siegel, Peter; Smith, R. Peter

1995-01-01

Proposed Quartz substrate Upside-down Integrated Device (QUID) relies on UV-curable adhesive to bond semiconductor with quartz. Integrated circuits including planar GaAs Schottky diodes and passive circuit elements (such as bandpass filters) fabricated on quartz substrates. Circuits designed to operate as mixers in waveguide circuit at millimeter and submillimeter wavelengths. Integrated circuits mechanically more robust, larger, and easier to handle than planar Schottky diode chips. Quartz substrate more suitable for waveguide circuits than GaAs substrate.

SEMICONDUCTOR TECHNOLOGY Dummy fill effect on CMP planarity

NASA Astrophysics Data System (ADS)

Junxiong, Zhou; Lan, Chen; Wenbiao, Ruan; Zhigang, Li; Weixiang, Shen; Tianchun, Ye

2010-10-01

With the use of a chemical-mechanical polishing (CMP) simulator verified by testing data from a foundry, the effect of dummy fill characteristics, such as fill size, fill density and fill shape, on CMP planarity is analyzed. The results indicate that dummy density has a significant impact on oxide erosion, and copper dishing is in proportion to dummy size. We also demonstrate that cross shape dummy fill can have the best dishing performance at the same density.

Cascaded exciton energy transfer in a monolayer semiconductor lateral heterostructure assisted by surface plasmon polariton.

PubMed

Shi, Jinwei; Lin, Meng-Hsien; Chen, I-Tung; Mohammadi Estakhri, Nasim; Zhang, Xin-Quan; Wang, Yanrong; Chen, Hung-Ying; Chen, Chun-An; Shih, Chih-Kang; Alù, Andrea; Li, Xiaoqin; Lee, Yi-Hsien; Gwo, Shangjr

2017-06-26

Atomically thin lateral heterostructures based on transition metal dichalcogenides have recently been demonstrated. In monolayer transition metal dichalcogenides, exciton energy transfer is typically limited to a short range (~1 μm), and additional losses may be incurred at the interfacial regions of a lateral heterostructure. To overcome these challenges, here we experimentally implement a planar metal-oxide-semiconductor structure by placing a WS 2 /MoS 2 monolayer heterostructure on top of an Al 2 O 3 -capped Ag single-crystalline plate. We find that the exciton energy transfer range can be extended to tens of microns in the hybrid structure mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, allowing cascaded exciton energy transfer from one transition metal dichalcogenides region supporting high-energy exciton resonance to a different transition metal dichalcogenides region in the lateral heterostructure with low-energy exciton resonance. The realized planar hybrid structure combines two-dimensional light-emitting materials with planar plasmonic waveguides and offers great potential for developing integrated photonic and plasmonic devices.Exciton energy transfer in monolayer transition metal dichalcogenides is limited to short distances. Here, Shi et al. fabricate a planar metal-oxide-semiconductor structure and show that exciton energy transfer can be extended to tens of microns, mediated by an exciton-surface-plasmon-polariton-exciton conversion mechanism.

Water management in a planar air-breathing fuel cell array using operando neutron imaging

NASA Astrophysics Data System (ADS)

Coz, E.; Théry, J.; Boillat, P.; Faucheux, V.; Alincant, D.; Capron, P.; Gébel, G.

2016-11-01

Operando Neutron imaging is used for the investigation of a planar air-breathing array comprising multiple cells in series. The fuel cell demonstrates a stable power density level of 150 mW/cm2. Water distribution and quantification is carried out at different operating points. Drying at high current density is observed and correlated to self-heating and natural convection. Working in dead-end mode, water accumulation at lower current density is largely observed on the anode side. However, flooding mechanisms are found to begin with water condensation on the cathode side, leading to back-diffusion and anodic flooding. Specific in-plane and through-plane water distribution is observed and linked to the planar array design.

Crack Growth Mechanisms under Anti-Plane Shear in Composite Laminates

NASA Astrophysics Data System (ADS)

Horner, Allison Lynne

The research conducted for this dissertation focuses on determining the mechanisms associated with crack growth in polymer matrix composite laminates subjected to anti-plane shear (mode III) loading. For mode III split-beam test methods were proposed, and initial evaluations were conducted. A single test method was selected for further evaluation. Using this test method, it was determined that the apparent mode III delamination toughness, GIIIc , depended on geometry, which indicated a true material property was not being measured. Transverse sectioning and optical microscopy revealed an array of transverse matrix cracks, or echelon cracks, oriented at approximately 45° and intersecting the plane of the delamination. Subsequent investigations found the echelon array formed prior to the onset of planar delamination advance and that growth of the planar delamination is always coupled to echelon array formation in these specimens. The evolution of the fracture surfaces formed by the echelon array and planar delamination were studied, and it was found that the development was similar to crack growth in homogenous materials subjected to mode III or mixed mode I-III loading, although the composite laminate architecture constrained the fracture surface development differently than homogenous materials. It was also found that, for split-beam specimens such as those used herein, applying an anti-plane shear load results in twisting of the specimen's uncracked region which gives rise to a mixed-mode I-III load condition. This twisting has been related to the apparent mode III toughness as well as the orientation of the transverse matrix cracks. A finite element model was then developed to study the mechanisms of initial echelon array formation. From this, it is shown that an echelon array will develop, but will become self-limiting prior to the onset of planar delamination growth.

Observing planar cell polarity in multiciliated mouse airway epithelial cells.

PubMed

Vladar, Eszter K; Lee, Yin Loon; Stearns, Tim; Axelrod, Jeffrey D

2015-01-01

The concerted movement of cilia propels inhaled contaminants out of the lungs, safeguarding the respiratory system from toxins, pathogens, pollutants, and allergens. Motile cilia on the multiciliated cells (MCCs) of the airway epithelium are physically oriented along the tissue axis for directional motility, which depends on the planar cell polarity (PCP) signaling pathway. The MCCs of the mouse respiratory epithelium have emerged as an important model for the study of motile ciliogenesis and the PCP signaling mechanism. Unlike other motile ciliated or planar polarized tissues, airway epithelial cells are relatively easily accessible and primary cultures faithfully model many of the essential features of the in vivo tissue. There is growing interest in understanding how cells acquire and polarize motile cilia due to the impact of mucociliary clearance on respiratory health. Here, we present methods for observing and quantifying the planar polarized orientation of motile cilia both in vivo and in primary culture airway epithelial cells. We describe how to acquire and evaluate electron and light microscopy images of ciliary ultrastructural features that reveal planar polarized orientation. Furthermore, we describe the immunofluorescence localization of PCP pathway components as a simple readout for airway epithelial planar polarization and ciliary orientation. These methods can be adapted to observe ciliary orientation in other multi- and monociliated cells and to detect PCP pathway activity in any tissue or cell type. Copyright © 2015 Elsevier Inc. All rights reserved.

Silicon Dioxide Planarization: Impacts on Optical Coatings for High Energy Laser

NASA Astrophysics Data System (ADS)

Day, Travis E.

The work of this thesis is devoted to examining the impact of silicon dioxide (silica or SiO2) planarization on the optical properties and laser damage resistance of thin-film coatings. SiO2 planarization is a process to smooth out fluence limiting nodular defects within multilayer coatings for high-energy laser applications. Mitigating these defects will improve the power handling abilities and improve the lifetime of laser coatings. Presented here is a combination of work with the aim of evaluating the optical and laser damage properties of SiO2 planarization within single layers, bilayers, and multilayers. As compared to control (non-planarized) samples, a 2-3x increase in the thin-film absorption, which decreases with post-process annealing, was discovered for SiO2 planarized samples. This suggests that planarization creates oxygen-related defects which can be annealed out and little impurity implantation. Investigations of laser damage resistance were carried out at lambda = 1030nm and pulse durations of tau = 220ps and 9ps. The laser damage of single and bilayer coatings is known to be dependent on the substrate-coating interface and this is further evidenced within this thesis. This is because the effects of planarization are masked by the extrinsic laser damage processes within the single and bilayers. Slight change (< 15%) in the laser induced damage threshold (LIDT) at 220ps and 9ps was observed for planarized single and bilayers. Depending on coating design, post-process annealing was shown to increase the LIDT by 10% to 75% at 220ps and 10% to 45% at 9ps. Although the fused silica substrate surface LIDT was shown to follow the √tau pulse scaling law for pulses above 10ps, the single and bilayer coatings do not follow this pulse scaling. The divergence from the √tau pulse scaling on the coatings suggests a variation in the laser damage initiation mechanisms between 220ps and 9ps. Multilayer high-reflecting (HR) mirrors with varying planarization design were also damage tested. A 6-7 J/cm2 LIDT, with 220ps, was observed for HR coatings with SiO2 planarization layers within high electric-field areas within the coating. However, SiO2 planarization at the substrate-coating interface, where the electric-field is minimal, and control (non-planarized) was shown to have a LIDT of 63 +/- 1.2 J/cm 2 and 21.5 +/- 0.5 J/cm2 for 220ps, respectively. At 9ps, the LIDT varied less than 90% difference between the various planarization designs. The substrate-coating planarization multilayer and control coating had an equal LIDT of 9.6 +/- .3 J/cm2 at 9ps.

The Mechanism of Covalent Bonding: Analysis within the Huckel Model of Electronic Structure

ERIC Educational Resources Information Center

Nordholm, Sture; Back, Andreas; Backsay, George B.

2007-01-01

The commonly used Huckel model of electronic structure is employed to study the mechanisms of covalent bonding, a quantum effect related to electron dynamics. The model also explains the conjugation and aromaticity of planar hydrocarbon molecules completely.

Inkjet-based adaptive planarization (Conference Presentation)

NASA Astrophysics Data System (ADS)

Singhal, Shrawan; Grigas, Michelle M.; Khusnatdinov, Niyaz; Sreenivasan, Srinivasan V.

2017-03-01

Planarization is a critical unit step in the lithography process because it enables patterning of surfaces with versatile pattern density without compromising on the stringent planarity and depth-of-focus requirements. In addition to nanoscale pattern density variation, parasitics such as pre-existing wafer topography, can corrupt the desired process output after planarization. The topography of any surface can be classified in three broad categories, depending upon the amplitude and spatial wavelength of the same [1], [2]: (i) nominal shape, (ii) nanotopography and (iii) roughness. The nominal shape is given by the largest spatial wavelengths, typically < 20mm. For spatial length scales of 1-20mm, height variations at this spatial wavelength range are classified as nanotopography. Roughness usually has lower spatial wavelengths. While the nominal shape of a substrate surface is usually decided by the nature of wafer preparation and the tooling and chucking infrastructure used in the same, roughness is usually mitigated by standard polishing techniques. It is the intermediate nanotopography that is probably the most critical surface topography parameter. This is because most traditional polishing techniques cannot selectively address pre-existing substrate topography, without introducing a parasitic signature at the scale of nanotopography. Moreover, fields with pattern density variation typically also have length scales that are commensurate with nanotopography. It is thus instructive to summarize existing planarization technology to understand current limitations. Spin on Glass and Etch back is one technique used for micron scale device manufacturing [3]. As the name implies, a glass dielectric is spin-coated on the substrate followed by etching in a chemistry that ensures equal etching rates for both the sacrificial glass and the underlying film or substrate material. Photoresists may also be used instead of glass. However, the global planarity that can be achieved by this technique is limited. Also, planarization over a large isolated topographical feature has been studied for the reverse-tone Jet-and-Flash Imprint Lithography process, also known as JFIL-R [4]. This relies on surface tension and capillary effects to smoothen a spin-coated Si containing film that can be etched to obtain a smooth profile. To meet the stringent requirement of planarity in submicron device technologies Chemical Mechanical Planarization (CMP) is the most widely used planarization technology [5], [6]. It uses a combination of abrasive laden chemical slurry and a mechanical pad for achieving planar profiles. The biggest concern with CMP is the dependence of material removal rate on the pattern density of material, leading to the formation of a step between the high density and low-density. The step shows up as a long-range thickness variation in the planarized film, similar in scale to pre-existing substrate topography that should have been polished away. Preventive techniques like dummy fill and patterned resist can be used to reduce the variation in pattern density. These techniques increase the complexity of the planarization process and significantly limit the device design flexibility. Contact Planarization (CP) has also been reported as an alternative to the CMP processing [7], [8]. A substrate is spin coated with a photo curable material and pre baked to remove residual solvent. An ultra-flat surface or an optical flat is pressed on the spin-coated wafer. The material is forced to reflow. Pressure is used to spread out material evenly and achieve global planarization. The substrate is then exposed to UV radiation to harden the photo curable material. Although attractive, this process is not adaptive as it does not account for differences in surface topography of the wafer and the optical flat, nor can it address all the parasitics that arise during the process itself. The optical flat leads to undesirable planarization of even the substrate nominal shape and nanotopography, which corrupts the final film thickness profile. Hence, it becomes extremely difficult to eliminate this signature to a desirable extent without introducing other parasitic signatures. An example of this is shown in Figure 1. In this paper, a novel adaptive planarization process has been presented that potentially addresses the problems associated with planarization of varying pattern density, even in the presence of pre-existing substrate topography [9]. This process is called Inkjet-enabled Adaptive Planarization (IAP). The IAP process uses an inverse optimization scheme, built around a validated fluid mechanics-based forward model [10], that takes the pre-existing substrate topography and pattern layout as inputs. It then generates an inkjet drop pattern with a material distribution that is correlated with the desired planarization film profile. This allows a contiguous film to be formed with the desired thickness variation to cater to the topography and any parasitic signatures caused by the pattern layout. This film is formed by the coercing action of a compliant superstrate, which forces the drops to spread and merge and eliminates any bubble trapping. Then, the film is cured using blanket UV exposure and the superstrate separated to reveal the desired planarized film. The use of an inverse optimization algorithm allows substrate topography to be addressed adaptively. In other words, the algorithm can generate a drop pattern that does not disturb the pre-existing substrate topography substantially, but only caters to the pattern density variation. This process has potential advantages over other planarization techniques because of its adaptive nature. Hence, the IAP process can cater to substrates of varying topographies and pattern densities by changing the inkjetted material distribution, without any changes in hardware. The IAP process can also address pre-existing substrate topography selectively by conforming to the nominal shape while planarizing over the pattern layout. A schematic of the IAP process is shown in Figure 2. The goal of this paper is to present some preliminary results from the IAP process. A test pattern layout has been generated with the help of photolithography, and is shown in Figure 3. For the purpose of this trial, the nanoscale features have not been patterned, as it is expected that the planarization process will be blind to their presence. Thus, areas with nanoscale patterns have been patterned as a single feature of SiO2 with height equal to 100 nm. These features are adjacent to pattern-less areas, thus marking a drastic change in pattern density. As can be seen in Figure 4, the smallest length scale across which pattern density changes, is 70 microns. The goal of the IAP process is to be able to planarize this pattern with a film that conforms to pre-existing substrate topography. The targeted planarity of the film is 95% 3sigma, while the targeted film thickness at the tallest feature is less than 30 nm. In another trial, the inverse tone of the same layout will also be tested. This pattern has features of height equal to 100 nm where the previous pattern did not. The targeted metrics for the inverse layout are the same as the nominal layout.

Planar Cell Polarity Breaks the Symmetry of PAR Protein Distribution prior to Mitosis in Drosophila Sensory Organ Precursor Cells.

PubMed

Besson, Charlotte; Bernard, Fred; Corson, Francis; Rouault, Hervé; Reynaud, Elodie; Keder, Alyona; Mazouni, Khalil; Schweisguth, François

2015-04-20

During development, cell-fate diversity can result from the unequal segregation of fate determinants at mitosis. Polarization of the mother cell is essential for asymmetric cell division (ACD). It often involves the formation of a cortical domain containing the PAR complex proteins Par3, Par6, and atypical protein kinase C (aPKC). In the fly notum, sensory organ precursor cells (SOPs) divide asymmetrically within the plane of the epithelium and along the body axis to generate two distinct cells. Fate asymmetry depends on the asymmetric localization of the PAR complex. In the absence of planar cell polarity (PCP), SOPs divide with a random planar orientation but still asymmetrically, showing that PCP is dispensable for PAR asymmetry at mitosis. To study when and how the PAR complex localizes asymmetrically, we have used a quantitative imaging approach to measure the planar polarization of the proteins Bazooka (Baz, fly Par3), Par6, and aPKC in living pupae. By using imaging of functional GFP-tagged proteins with image processing and computational modeling, we find that Baz, Par6, and aPKC become planar polarized prior to mitosis in a manner independent of the AuroraA kinase and that PCP is required for the planar polarization of Baz, Par6, and aPKC during interphase. This indicates that a "mitosis rescue" mechanism establishes asymmetry at mitosis in PCP mutants. This study therefore identifies PCP as the initial symmetry-breaking signal for the planar polarization of PAR proteins in asymmetrically dividing SOPs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Magnetic Induction Machines Integrated into Bulk-Micromachined Silicon

DTIC Science & Technology

2006-04-01

Actuator Workshop (Hilton Head 2000), pp. 43–7, Jun. 2000. [5] H. Guckel et al., “A first functional current excited planar rotational magnetic micromotor ...in Proc. IEEE Micro Electro Mechanical Sys- tems (MEMS’93), Feb. 1993, pp. 7–11. [6] , “Planar rotational magnetic micromotors ,” Int. J. Appl... micromotor with fully integrated stator and coils,” J. Micro- electromech. Syst., vol. 2, no. 4, pp. 165–73, Dec. 1993. [8] B. Wagner, M. Kreutzer, and W

Generalized Models for Rock Joint Surface Shapes

PubMed Central

Du, Shigui; Hu, Yunjin; Hu, Xiaofei

2014-01-01

Generalized models of joint surface shapes are the foundation for mechanism studies on the mechanical effects of rock joint surface shapes. Based on extensive field investigations of rock joint surface shapes, generalized models for three level shapes named macroscopic outline, surface undulating shape, and microcosmic roughness were established through statistical analyses of 20,078 rock joint surface profiles. The relative amplitude of profile curves was used as a borderline for the division of different level shapes. The study results show that the macroscopic outline has three basic features such as planar, arc-shaped, and stepped; the surface undulating shape has three basic features such as planar, undulating, and stepped; and the microcosmic roughness has two basic features such as smooth and rough. PMID:25152901

Security hologram foil labels with a design facilitating authenticity testing: effects of mechanical bending of substrates with the glued on holograms

NASA Astrophysics Data System (ADS)

Aubrecht, Ivo

2015-05-01

Optimal design of security holograms or diffractive optically variable image devices (DOVIDs) that would be complex enough to deter counterfeiters from attempts of mimicking but contains features readily recognizable by laymen has been addressed by many experts. This paper tries to discuss effects of mechanical bending of a flexible substrate to visual appearance of a glued-on foil DOVID. Initially plane, the DOVID is deformed to a convex- or concave-shaped curved surface. Theoretical analyses and experimental results assume the surface to be a cylindrical segment and concern rainbow-type surface-relief holograms that are recorded piecewise in a photoresist material, coated on planar and non-planar substrates.

A novel mechatronic system for measuring end-point stiffness: mechanical design and preliminary tests.

PubMed

Masia, L; Sandini, G; Morasso, P G

2011-01-01

Measuring arm stiffness is of great interest for many disciplines from biomechanics to medicine especially because modulation of impedance represents one of the main mechanism underlying control of movement and interaction with external environment. Previous works have proposed different methods to identify multijoint hand stiffness by using planar or even tridimensional haptic devices, but the associated computational burden makes them not easy to implement. We present a novel mechanism conceived for measuring multijoint planar stiffness by a single measurement and in a reduced execution time. A novel mechanical rotary device applies cyclic radial perturbation to human arm of a known displacement and the force is acquired by means of a 6-axes commercial load cell. The outcomes suggest that the system is not only reliable but allows obtaining a bi-dimensional estimation of arm stiffness in reduced amount of time and the results are comparable with those reported in previous researches. © 2011 IEEE

Use of chemical-mechanical polishing for fabricating photonic bandgap structures

DOEpatents

Fleming, James G.; Lin, Shawn-Yu; Hetherington, Dale L.; Smith, Bradley K.

1999-01-01

A method is disclosed for fabricating a two- or three-dimensional photonic bandgap structure (also termed a photonic crystal, photonic lattice, or photonic dielectric structure). The method uses microelectronic integrated circuit (IC) processes to fabricate the photonic bandgap structure directly upon a silicon substrate. One or more layers of arrayed elements used to form the structure are deposited and patterned, with chemical-mechanical polishing being used to planarize each layer for uniformity and a precise vertical tolerancing of the layer. The use of chemical-mechanical planarization allows the photonic bandgap structure to be formed over a large area with a layer uniformity of about two-percent. Air-gap photonic bandgap structures can also be formed by removing a spacer material separating the arrayed elements by selective etching. The method is useful for fabricating photonic bandgap structures including Fabry-Perot resonators and optical filters for use at wavelengths in the range of about 0.2-20 .mu.m.

Triple bar, high efficiency mechanical sealer

DOEpatents

Pak, Donald J.; Hawkins, Samantha A.; Young, John E.

2013-03-19

A clamp with a bottom clamp bar that has a planar upper surface is provided. The clamp may also include a top clamp bar connected to the bottom clamp bar, and a pressure distribution bar between the top clamp bar and the bottom clamp bar. The pressure distribution bar may have a planar lower surface in facing relation to the upper surface of the bottom clamp bar. An object is capable of being disposed in a clamping region between the upper surface and the lower surface. The width of the planar lower surface may be less than the width of the upper surface within the clamping region. Also, the pressure distribution bar may be capable of being urged away from the top clamp bar and towards the bottom clamp bar.

Atomically informed nonlocal semi-discrete variational Peierls-Nabarro model for planar core dislocations

PubMed Central

Liu, Guisen; Cheng, Xi; Wang, Jian; Chen, Kaiguo; Shen, Yao

2017-01-01

Prediction of Peierls stress associated with dislocation glide is of fundamental concern in understanding and designing the plasticity and mechanical properties of crystalline materials. Here, we develop a nonlocal semi-discrete variational Peierls-Nabarro (SVPN) model by incorporating the nonlocal atomic interactions into the semi-discrete variational Peierls framework. The nonlocal kernel is simplified by limiting the nonlocal atomic interaction in the nearest neighbor region, and the nonlocal coefficient is directly computed from the dislocation core structure. Our model is capable of accurately predicting the displacement profile, and the Peierls stress, of planar-extended core dislocations in face-centered cubic structures. Our model could be extended to study more complicated planar-extended core dislocations, such as <110> {111} dislocations in Al-based and Ti-based intermetallic compounds. PMID:28252102

Interfacing planar superconducting qubits with high overtone bulk acoustic phonons

NASA Astrophysics Data System (ADS)

Kervinen, Mikael; Rissanen, Ilkka; Sillanpää, Mika

2018-05-01

Mechanical resonators are a promising way for interfacing qubits in order to realize hybrid quantum systems that offer great possibilities for applications. Mechanical systems can have very long energy lifetimes, and they can be further interfaced to other systems. Moreover, integration of a mechanical oscillator with qubits creates a potential platform for the exploration of quantum physics in macroscopic mechanical degrees of freedom. The utilization of high overtone bulk acoustic resonators coupled to superconducting qubits is an intriguing platform towards these goals. These resonators exhibit a combination of high-frequency and high-quality factors. They can reach their quantum ground state at dilution refrigeration temperatures and they can be strongly coupled to superconducting qubits via their piezoelectric effect. In this paper, we demonstrate our system where bulk acoustic phonons of a high overtone resonator are coupled to a transmon qubit in a planar circuit architecture. We show that the bulk acoustic phonons are interacting with the qubit in a simple design architecture at the quantum level, representing further progress towards the quantum control of mechanical motion.

Tribochemical investigation of microelectronic materials

NASA Astrophysics Data System (ADS)

Kulkarni, Milind Sudhakar

To achieve efficient planarization with reduced device dimensions in integrated circuits, a better understanding of the physics, chemistry, and the complex interplay involved in chemical mechanical planarization (CMP) is needed. The CMP process takes place at the interface of the pad and wafer in the presence of the fluid slurry medium. The hardness of Cu is significantly less than the slurry abrasive particles which are usually alumina or silica. It has been accepted that a surface layer can protect the Cu surface from scratching during CMP. Four competing mechanisms in materials removal have been reported: the chemical dissolution of Cu, the mechanical removal through slurry abrasives, the formation of thin layer of Cu oxide and the sweeping surface material by slurry flow. Despite the previous investigation of Cu removal, the electrochemical properties of Cu surface layer is yet to be understood. The motivation of this research was to understand the fundamental aspects of removal mechanisms in terms of electrochemical interactions, chemical dissolution, mechanical wear, and factors affecting planarization. Since one of the major requirements in CMP is to have a high surface finish, i.e., low surface roughness, optimization of the surface finish in reference to various parameters was emphasized. Three approaches were used in this research: in situ measurement of material removal, exploration of the electropotential activation and passivation at the copper surface and modeling of the synergistic electrochemical-mechanical interactions on the copper surface. In this research, copper polishing experiments were conducted using a table top tribometer. A potentiostat was coupled with this tribometer. This combination enabled the evaluation of important variables such as applied pressure, polishing speed, slurry chemistry, pH, materials, and applied DC potential. Experiments were designed to understand the combined and individual effect of electrochemical interactions as well as mechanical impact during polishing. Extensive surface characterization was performed with AFM, SEM, TEM and XPS. An innovative method for direct material removal measurement on the nanometer scale was developed and used. Experimental observations were compared with the theoretically calculated material removal rate values. The synergistic effect of all of the components of the process, which result in a better quality surface finish was quantitatively evaluated for the first time. Impressed potential during CMP proved to be a controlling parameter in the material removal mechanism. Using the experimental results, a model was developed, which provided a practical insight into the CMP process. The research is expected to help with electrochemical material removal in copper planarization with low-k dielectrics.

Spontaneous Planar Chiral Symmetry Breaking in Cells

NASA Astrophysics Data System (ADS)

Hadidjojo, Jeremy; Lubensky, David

Recent progress in animal development has highlighted the central role played by planar cell polarity (PCP) in epithelial tissue morphogenesis. Through PCP, cells have the ability to collectively polarize in the plane of the epithelium by localizing morphogenetic proteins along a certain axis. This allows direction-dependent modulation of tissue mechanical properties that can translate into the formation of complex, non-rotationally invariant shapes. Recent experimental observations[1] show that cells, in addition to being planar-polarized, can also spontaneously develop planar chirality, perhaps in the effort of making yet more complex shapes that are reflection non-invariant. In this talk we will present our work in characterizing general mechanisms that can lead to spontaneous chiral symmetry breaking in cells. We decompose interfacial concentration of polarity proteins in a hexagonal cell packing into irreducible representations. We find that in the case of polar concentration distributions, a chiral state can only be reached from a secondary instability after the cells are polarized. However in the case of nematic distributions, we show that a finite-amplitude (subcritical, or ``first-order'') nematic transition can send the system from disorder directly to a chiral state. In addition, we find that perturbing the system by stretching the hexagonal packing enables direct (supercritical, or ``second-order'') chiral transition in the nematic case. Finally, we do a Landau expansion to study competition between stretch-induced chirality and the tendency towards a non-chiral state in packings that have retained the full 6-fold symmetry.

Motor vehicle seat belt restraint system analysis during rollover.

PubMed

Meyer, Steven E; Hock, Davis; Forrest, Stephen; Herbst, Brian; Sances, Anthony; Kumaresan, Srirangam

2003-01-01

The multi-planar and multiple impact long duration accident sequence of a real world rollover results in multidirectional vehicle acceleration pulses and multiplanar occupant motions not typically seen in a planar crash sequence. Various researchers have documented that, while contemporary production emergency locking seatbelt retractors (ELRs) have been found to be extremely effective in the planar crashes in which they are extensively evaluated, when subjected to multi-planar acceleration environments their response may be different than expected. Specifically, accelerations in the vertical plane have been shown to substantially affect the timeliness of the retractors inertial sensor moving out of its neutral position and locking the seat belt. An analysis of the vehicle occupant motions relative to the acceleration pulses sensed at the retractor location indicates a time phase shift that, under certain circumstances, can result in unexpected seat belt spool out and occupant excursions in these multi-planar, multiple impact crash sequences. This paper will review the various previous studies focusing on the retractors response to these multidirectional, including vertical, acceleration environments and review statistical studies based upon U.S. government collected data indicating a significant difference in belt usage rates in rollover accidents as compared to all other planar accident modes. A significant number of real world accident case studies will be reviewed wherein the performance of ELR equipped seatbelt systems spooled out. Finally, the typical occupant injury and the associated mechanism due to belt spool out in real world accidents will be delineated.

Handsheet formation and mechanical testing via fiber-level simulations

Treesearch

Leonard H. Switzer; Daniel J. Klingenberg; C. Tim Scott

2004-01-01

A fiber model and simulation method are employed to investigate the mechanical response of planar fiber networks subjected to elongational deformation. The simulated responses agree qualitatively with numerous experimental observations. suggesting that such simulation methods may be useful for probing the relationships between fiber properties and interactions and the...

On equally and completely stressed hinged mechanisms

NASA Astrophysics Data System (ADS)

Kovalev, M. D.

2018-05-01

The following new question is investigated: is there any bar and joint planar linkage with every bar having the same nonzero stress in each position of the linkage, and with each angle between adjacent bars varying, when the linkage moves? The absence of such mechanisms under appropriate condition is prooved.

Mechanical interface having multiple grounded actuators

DOEpatents

Martin, Kenneth M.; Levin, Mike D.; Rosenberg, Louis B.

1998-01-01

An apparatus and method for interfacing the motion of a user-manipulable object with a computer system includes a user object physically contacted or grasped by a user. A 3-D spatial mechanism is coupled to the user object, such as a stylus or a medical instrument, and provides three degrees of freedom to the user object. Three grounded actuators provide forces in the three degrees of freedom. Two of the degrees of freedom are a planar workspace provided by a closed-loop linkage of members, and the third degree of freedom is rotation of the planar workspace provided by a rotatable carriage. Capstan drive mechanisms transmit forces between actuators and the user object and include drums coupled to the carriage, pulleys coupled to grounded actuators, and flexible cables transmitting force between the pulleys and the drums. The flexibility of the cable allows the drums to rotate with the carriage while the pulleys and actuators remain fixed to ground. The interface also may include a floating gimbal mechanism coupling the linkage to the user object. The floating gimbal mechanism includes rotatably coupled gimbal members that provide three degrees of freedom to the user object and capstan mechanisms coupled between sensors and the gimbal members for providing enhanced sensor resolution.

Book Reviews

NASA Astrophysics Data System (ADS)

Radl, Bruce M.; Donnelly, J. P.; Oliner, Arthur A.

1986-08-01

Laser Beam Scanning: Opto-mechanical devices, systems, and data Storage Optics-Reviewed by Bruce M. Radl; Integrated Optoelectronics-Reviewed by J.P. Donnelly; Planar Circuits for Microwaves and Lightwaves-Reviewed by Arthur A. Oliner;

Unveiling the Switching Riddle of Silver Tetracyanoquinodimethane Towards Novel Planar Single-Crystalline Electrochemical Metallization Memories.

PubMed

Yang, Fangxu; Zhao, Qiang; Xu, Chunhui; Zou, Ye; Dong, Huanli; Zheng, Yonggang; Hu, Wenping

2016-09-01

The switching riddle of AgTCNQ is shown to be caused by the solid electrolyte mechanism. Both factors of bulk phase change and contact issue play key roles in the efficient work of the devices. An effective strategy is developed to locate the formation/disruption of Ag conductive filaments using the planar asymmetric configuration of Au/AgTCNQ/AlOx /Al. These novel electrochemical metallization memories demonstrate many promising properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reliability of Cascaded THz Frequency Chains with Planar GaAs Circuits

NASA Technical Reports Server (NTRS)

Maiwald, Frank; Schlecht, Erich; Lin, Robert; Ward, John; Pearson, John; Siegel, Peter; Mehdi, Imran

2004-01-01

Planar GaAs Schottky diodes will be utilized for all of the LO chains on the HIPI instrument for the Herschel Space Observatory. A better understanding of device degradation mechanisms is desirable in order to specify environmental and operational conditions that do not reduce device life times. Failures and degradation associated with ESD (Electrostatic Discharge), high temperatures, DC currents and RF induced current and heating have been investigated. The goal is to establish a procedure to obtain the safe operating range for a given frequency multiplier.

Multi-functional composite materials for catalysis and chemical mechanical planarization

NASA Astrophysics Data System (ADS)

Coutinho, Cecil A.

2009-12-01

Composite materials formed from two or more functionally different materials offer a versatile avenue to create a tailored material with well defined traits. Within this dissertation research, multi-functional composites were synthesized based on organic and inorganic materials. The functionally of these composites was experimentally tested and a semi-empirical model describing the sedimentation behavior of these particles was developed. This first objective involved the fabrication of microcomposites consisting of titanium dioxide (TiO2) nanoparticles confined within porous, microgels of a thermo-responsive polymer for use in the photocatalytic treatment of wastewater. TiO2 has been shown to be an excellent photocatalyst with potential applications in advanced oxidative processes such as wastewater remediation. Upon UV irradiation, short-lived electron-hole pairs are generated, which produce oxidative species that degrade simple organic contaminants. The rapid sedimentation of these microcomposites provided an easy gravimetric separation after remediation. Methyl orange was used as a model organic contaminant to investigate the kinetics of photodegradation under a range of concentrations and pH conditions. Although after prolonged periods of UV irradiation (˜8-13 hrs), the titania-microgels also degrade, regeneration of the microcomposites was straightforward via the addition of polymer microgels with no loss in photocatalytic activity of the reformed microcomposites. The second objective within this dissertation involved the systematic development of abrasive microcomposite particles containing well dispersed nanoparticles of ceria in an organic/inorganic hybrid polymeric particle for use in chemical mechanical polishing/planarization (CMP). A challenge in IC fabrication involves the defect-free planarization of silicon oxide films for successful multi-layer deposition. Planarization studies conducted with the microcomposites prepared in this research, yield very smooth, planar surfaces with removal rates that rival those of inorganic oxides slurries typically used in industry. The density and size of these ceria-microgel particles could be controlled by varying the temperature or composition during synthesis, leading to softer or harder polishing when desired.

Research on some auxiliary mechanisms used in passenger cars

NASA Astrophysics Data System (ADS)

Antonescu, Daniela; Iozsa, Daniel; Antonescu, Ovidiu; Fratila, Gh.

2017-10-01

The paper presents the results of researches on the topological structure and geometrical analysis of the planar mechanisms with articulated bars, which are used for actuating the doors of cars. The main five types of car doors with rotate movement (folding) are presented, being described both as constructive structure and mode of operation, through suitable kinematic schemes. Some innovative solutions for vehicle door actuating mechanisms aim to use as little space as possible, which is beneficial for car parking. There are three types of car door movements: rotation, sliding and planar rotational-sliding. Most of the cars are equipped with folding doors, where the rotate movement is limited and operates horizontally. Almost all sliding doors are placed on the rear of the car (only for passengers, not for driver). Unlike rotate doors, the sliding doors require a minimum lateral space, which is an advantage, especially in parking places. In the end of the paper, a kinematic analysis of the canopy 4-bar mechanism has been performed, in order to increase the passenger comfort on the access into the vehicle.

Shoulder Injuries in US Astronauts Related to EVA Suit Design

NASA Technical Reports Server (NTRS)

Scheuring, R. A.; McCulloch, P.; Van Baalen, Mary; Minard, Charles; Watson, Richard; Blatt, T.

2011-01-01

Introduction: For every one hour spent performing extravehicular activity (EVA) in space, astronauts in the US space program spend approximately six to ten hours training in the EVA spacesuit at NASA-Johnson Space Center's Neutral Buoyancy Lab (NBL). In 1997, NASA introduced the planar hard upper torso (HUT) EVA spacesuit which subsequently replaced the existing pivoted HUT. An extra joint in the pivoted shoulder allows increased mobility but also increased complexity. Over the next decade a number of astronauts developed shoulder problems requiring surgical intervention, many of whom performed EVA training in the NBL. This study investigated whether changing HUT designs led to shoulder injuries requiring surgical repair. Methods: US astronaut EVA training data and spacesuit design employed were analyzed from the NBL data. Shoulder surgery data was acquired from the medical record database, and causal mechanisms were obtained from personal interviews Analysis of the individual HUT designs was performed as it related to normal shoulder biomechanics. Results: To date, 23 US astronauts have required 25 shoulder surgeries. Approximately 48% (11/23) directly attributed their injury to training in the planar HUT, whereas none attributed their injury to training in the pivoted HUT. The planar HUT design limits shoulder abduction to 90 degrees compared to approximately 120 degrees in the pivoted HUT. The planar HUT also forces the shoulder into a forward flexed position requiring active retraction and extension to increase abduction beyond 90 degrees. Discussion: Multiple factors are associated with mechanisms leading to shoulder injury requiring surgical repair. Limitations to normal shoulder mechanics, suit fit, donning/doffing, body position, pre-existing injury, tool weight and configuration, age, in-suit activity, and HUT design have all been identified as potential sources of injury. Conclusion: Crewmembers with pre-existing or current shoulder injuries or certain anthropometric body types should conduct NBL EVA training in the pivoted HUT.

Fabrication of a stretchable solid-state micro-supercapacitor array.

PubMed

Kim, Daeil; Shin, Gunchul; Kang, Yu Jin; Kim, Woong; Ha, Jeong Sook

2013-09-24

We fabricated a stretchable micro-supercapacitor array with planar SWCNT electrodes and an ionic liquid-based triblock copolymer electrolyte. The mechanical stability of the entire supercapacitor array upon stretching was obtained by adopting strategic design concepts. First, the narrow and long serpentine metallic interconnections were encapsulated with polyimide thin film to ensure that they were within the mechanical neutral plane. Second, an array of two-dimensional planar micro-supercapacitor with SWCNT electrodes and an ion-gel-type electrolyte was made to achieve all-solid-state energy storage devices. The formed micro-supercapacitor array showed excellent performances which were stable over stretching up to 30% without any noticeable degradation. This work shows the strong potential of a stretchable micro-supercapacitor array in applications such as wearable computers, power dressing, electronic newspapers, paper-like mobile phones, and other easily collapsible gadgets.

Integration of planar cell polarity and ECM signaling in elongation of the vertebrate body plan.

PubMed

Skoglund, Paul; Keller, Ray

2010-10-01

The shaping of the vertebrate embryonic body plan depends heavily on the narrowing and lengthening (convergence and extension) of embryonic tissues by cell intercalation, a process by which cells actively crawl between one another along the axis of convergence to produce a narrower, longer array. We discuss recent evidence that the vertebrate non-canonical Wnt/Planar Cell Polarity (PCP) pathway, known to directly function in polarizing the movements of intercalating cells, is also involved in the localized assembly of extracellular matrix (ECM). These cell-ECM interactions, in turn, are necessary for expression of the oriented, polarized cell intercalation. The mechanism of PCP/ECM interactions, their molecular signaling, and their mechanical consequences for morphogenesis are discussed with the goal of identifying important unsolved issues. Copyright © 2010 Elsevier Ltd. All rights reserved.

Molecular mechanisms of decomposition of hydrated Na+Cl- ion pairs under planar nanopore conditions

NASA Astrophysics Data System (ADS)

Shevkunov, S. V.

2017-02-01

The decomposition of Na+Cl- ion pairs under the conditions of a nanoscopic planar pore with structureless walls in a material contact with water vapor at 298 K is simulated by Monte Carlo method. The transition from the state of a contact ion pair (CIP) to the state of solvent-separated ion pair (SSIP) is shown to occur as a result of an increase in the vapor pressure over a pore after exceeding the threshold number of molecules in a hydrate shell. It is found that the planar form of a molecular cluster under the conditions of a narrow pore does not level an abrupt structural transition and the formation of hydrogen bonds in the hydrate shell starts after three molecules are added. The hydrogen bond length under pore conditions is found to be resistant to variations in the hydrate shell size and coincides with that in water under normal conditions.

Pseudo Jahn-Teller effect in control and rationalization of chemical transformations in two-dimensional compounds

NASA Astrophysics Data System (ADS)

Gorinchoy, N. N.; Bersuker, I. B.

2017-05-01

We show that the pseudo Jahn-Teller effect (PJTE) is instrumental in predicting and rationalizing structural changes in chemical transformations of two-dimensional (2D) molecular systems by means of analyzing the symmetries and electron occupation of the ground and lowest excited electronic states and the energy gap between them, subject to their PJT coupling along the main distortion coordinates. Special attention is paid to rationalizing the PJTE origin of non-planarity of 2D compounds and to the restoration of their planar configurations. Examples of two series of 1,2- and 1,4-dithiin containing tricyclic compounds (carbon sulfide, thianthrene, and antracene and their derivatives) are used to demonstrate in detail the mechanism of (1) enhancement and suppression of the PJTE distortions (puckering) in redox processes, and (2) PJTE induced symmetry breaking and restoration of the planar configuration by chemical substitutions.

CMOS chip planarization by chemical mechanical polishing for a vertically stacked metal MEMS integration

NASA Astrophysics Data System (ADS)

Lee, Hocheol; Miller, Michele H.; Bifano, Thomas G.

2004-01-01

In this paper we present the planarization process of a CMOS chip for the integration of a microelectromechanical systems (MEMS) metal mirror array. The CMOS chip, which comes from a commercial foundry, has a bumpy passivation layer due to an underlying aluminum interconnect pattern (1.8 µm high), which is used for addressing individual micromirror array elements. To overcome the tendency for tilt error in the CMOS chip planarization, the approach is to sputter a thick layer of silicon nitride at low temperature and to surround the CMOS chip with dummy silicon pieces that define a polishing plane. The dummy pieces are first lapped down to the height of the CMOS chip, and then all pieces are polished. This process produced a chip surface with a root-mean-square flatness error of less than 100 nm, including tilt and curvature errors.

Effective constitutive relations for large repetitive frame-like structures

NASA Technical Reports Server (NTRS)

Nayfeh, A. H.; Hefzy, M. S.

1981-01-01

Effective mechanical properties for large repetitive framelike structures are derived using combinations of strength of material and orthogonal transformation techniques. Symmetry considerations are used in order to identify independent property constants. The actual values of these constants are constructed according to a building block format which is carried out in the three consecutive steps: (1) all basic planar lattices are identified; (2) effective continuum properties are derived for each of these planar basic grids using matrix structural analysis methods; and (3) orthogonal transformations are used to determine the contribution of each basic set to the overall effective continuum properties of the structure.

Planar cell polarity in moving cells: think globally, act locally

PubMed Central

Davey, Crystal F.

2017-01-01

ABSTRACT The planar cell polarity (PCP) pathway is best known for its role in polarizing epithelial cells within the plane of a tissue but it also plays a role in a range of cell migration events during development. The mechanism by which the PCP pathway polarizes stationary epithelial cells is well characterized, but how PCP signaling functions to regulate more dynamic cell behaviors during directed cell migration is much less understood. Here, we review recent discoveries regarding the localization of PCP proteins in migrating cells and their impact on the cell biology of collective and individual cell migratory behaviors. PMID:28096212

A Primer on Elliptic Functions with Applications in Classical Mechanics

ERIC Educational Resources Information Center

Brizard, Alain J.

2009-01-01

The Jacobi and Weierstrass elliptic functions used to be part of the standard mathematical arsenal of physics students. They appear as solutions of many important problems in classical mechanics: the motion of a planar pendulum (Jacobi), the motion of a force-free asymmetric top (Jacobi), the motion of a spherical pendulum (Weierstrass) and the…

Polymer planar waveguide Bragg gratings: fabrication, characterization, and sensing applications

NASA Astrophysics Data System (ADS)

Rosenberger, M.; Hessler, S.; Pauer, H.; Girschikofsky, M.; Roth, G. L.; Adelmann, B.; Woern, H.; Schmauss, B.; Hellmann, R.

2017-02-01

In this contribution, we give a comprehensive overview of the fabrication, characterization, and application of integrated planar waveguide Bragg gratings (PPBGs) in cyclo-olefin copolymers (COC). Starting with the measurement of the refractive index depth profile of integrated UV-written structures in COC by phase shifting Mach-Zehnder- Interferometry, we analyze the light propagation using numerical simulations. Furthermore, we show the rapid fabrication of humidity insensitive polymer waveguide Bragg gratings in cyclo-olefin copolymers and discuss the influence of the UV-dosage onto the spectral characteristics and the transmission behavior of the waveguide. Based on these measurements we exemplify that our Bragg gratings exhibit a reflectivity of over 99 % and are highly suitable for sensing applications. With regard to a negligible affinity to absorb water and in conjunction with high temperature stability these polymer devices are ideal for mechanical deformation sensing. Since planar structures are not limited to tensile but can also be applied for measuring compressive strain, we manufacture different functional devices and corroborate their applicability as optical sensors. Exemplarily, we highlight a temperature referenced PPBG sensor written into a femtosecond-laser cut tensile test geometry for tensile and compressive strain sensing. Furthermore, a flexible polymer planar shape sensor is presented.

Shaping the Atomic-Scale Geometries of Electrodes to Control Optical and Electrical Performance of Molecular Devices.

PubMed

Zhao, Zhikai; Liu, Ran; Mayer, Dirk; Coppola, Maristella; Sun, Lu; Kim, Youngsang; Wang, Chuankui; Ni, Lifa; Chen, Xing; Wang, Maoning; Li, Zongliang; Lee, Takhee; Xiang, Dong

2018-04-01

A straightforward method to generate both atomic-scale sharp and atomic-scale planar electrodes is reported. The atomic-scale sharp electrodes are generated by precisely stretching a suspended nanowire, while the atomic-scale planar electrodes are obtained via mechanically controllable interelectrodes compression followed by a thermal-driven atom migration process. Notably, the gap size between the electrodes can be precisely controlled at subangstrom accuracy with this method. These two types of electrodes are subsequently employed to investigate the properties of single molecular junctions. It is found, for the first time, that the conductance of the amine-linked molecular junctions can be enhanced ≈50% as the atomic-scale sharp electrodes are used. However, the atomic-scale planar electrodes show great advantages to enhance the sensitivity of Raman scattering upon the variation of nanogap size. The underlying mechanisms for these two interesting observations are clarified with the help of density functional theory calculation and finite-element method simulation. These findings not only provide a strategy to control the electron transport through the molecule junction, but also pave a way to modulate the optical response as well as to improve the stability of single molecular devices via the rational design of electrodes geometries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rotational MEMS mirror with latching arm for silicon photonics

NASA Astrophysics Data System (ADS)

Brière, Jonathan; Beaulieu, Philippe-Olivier; Saidani, Menouer; Nabki, Frederic; Menard, Michaël.

2015-02-01

We present an innovative rotational MEMS mirror that can control the direction of propagation of light beams inside of planar waveguides implemented in silicon photonics. Potential applications include but are not limited to optical telecommunications, medical imaging, scan and spectrometry. The mirror has a half-cylinder shape with a radius of 300 μm that provides low and constant optical losses over the full angular displacement range. A circular comb drive structure is anchored such that it allows free or latched rotation experimentally demonstrated over 8.5° (X-Y planar rotational movement) using 290V electrostatic actuation. The entire MEMS structure was implemented using the MEMSCAP SOIMUMPs process. The center of the anchor beam is designed to be the approximate rotation point of the circular comb drive to counter the rotation offset of the mirror displacement. A mechanical characterization of the MEMS mirror is presented. The latching mechanism provides up to 20 different angular locking positions allowing the mirror to counter any resonance or vibration effects and it is actuated with an electrostatic linear comb drive. An innovative gap closing structure was designed to reduce optical propagation losses due to beam divergence in the interstitial space between the mirror and the planar waveguide. The gap closing structure is also electrostatically actuated and includes two side stoppers to prevent stiction.

A Cul-3-BTB ubiquitylation pathway regulates junctional levels and asymmetry of core planar polarity proteins

PubMed Central

Strutt, Helen; Searle, Elizabeth; Thomas-MacArthur, Victoria; Brookfield, Rosalind; Strutt, David

2013-01-01

The asymmetric localisation of core planar polarity proteins at apicolateral junctions is required to specify cell polarity in the plane of epithelia. This asymmetric distribution of the core proteins is proposed to require amplification of an initial asymmetry by feedback loops. In addition, generation of asymmetry appears to require the regulation of core protein levels, but the importance of such regulation and the underlying mechanisms is unknown. Here we show that ubiquitylation acts through more than one mechanism to control core protein levels in Drosophila, and that without this regulation cellular asymmetry is compromised. Levels of Dishevelled at junctions are regulated by a Cullin-3-Diablo/Kelch ubiquitin ligase complex, the activity of which is most likely controlled by neddylation. Furthermore, activity of the deubiquitylating enzyme Fat facets is required to maintain Flamingo levels at junctions. Notably, ubiquitylation does not alter the total cellular levels of Dishevelled or Flamingo, but only that of the junctional population. When junctional core protein levels are either increased or decreased by disruption of the ubiquitylation machinery, their asymmetric localisation is reduced and this leads to disruption of planar polarity at the tissue level. Loss of asymmetry by altered core protein levels can be explained by reference to feedback models for amplification of asymmetry. PMID:23487316

PCP Signaling between Migrating Neurons and their Planar-Polarized Neuroepithelial Environment Controls Filopodial Dynamics and Directional Migration

PubMed Central

Moens, Cecilia B.

2016-01-01

The planar cell polarity (PCP) pathway is a cell-contact mediated mechanism for transmitting polarity information between neighboring cells. PCP “core components” (Vangl, Fz, Pk, Dsh, and Celsr) are essential for a number of cell migratory events including the posterior migration of facial branchiomotor neurons (FBMNs) in the plane of the hindbrain neuroepithelium in zebrafish and mice. While the mechanism by which PCP signaling polarizes static epithelial cells is well understood, how PCP signaling controls highly dynamic processes like neuronal migration remains an important outstanding question given that PCP components have been implicated in a range of directed cell movements, particularly during vertebrate development. Here, by systematically disrupting PCP signaling in a rhombomere-restricted manner we show that PCP signaling is required both within FBMNs and the hindbrain rhombomere 4 environment at the time when they initiate their migration. Correspondingly, we demonstrate planar polarized localization of PCP core components Vangl2 and Fzd3a in the hindbrain neuroepithelium, and transient localization of Vangl2 at the tips of retracting FBMN filopodia. Using high-resolution timelapse imaging of FBMNs in genetic chimeras we uncover opposing cell-autonomous and non-cell-autonomous functions for Fzd3a and Vangl2 in regulating FBMN protrusive activity. Within FBMNs, Fzd3a is required to stabilize filopodia while Vangl2 has an antagonistic, destabilizing role. However, in the migratory environment Fzd3a acts to destabilize FBMN filopodia while Vangl2 has a stabilizing role. Together, our findings suggest a model in which PCP signaling between the planar polarized neuroepithelial environment and FBMNs directs migration by the selective stabilization of FBMN filopodia. PMID:26990447

On spontaneous emission into guided modes with curved wavefronts

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

Yariv, A.; Margalit, S.

1982-11-01

The problem of spontaneous emission into guided modes with curved wavefronts is examined quantum mechanically. A classical result due to Petermann, which shows an increased emission rate relative to modes with planar phase fronts, is corroborated.

Dynamic simulation of train derailments

DOT National Transportation Integrated Search

2006-11-05

This paper describes a planar rigid-body model to examine the gross motions of rail cars in a train derailment. The model is implemented using a commercial software package called ADAMS (Automatic Dynamic Analysis of Mechanical Systems). The results ...

Test of the diffusing-diffusivity mechanism using near-wall colloidal dynamics

NASA Astrophysics Data System (ADS)

Matse, Mpumelelo; Chubynsky, Mykyta V.; Bechhoefer, John

2017-10-01

The mechanism of diffusing diffusivity predicts that, in environments where the diffusivity changes gradually, the displacement distribution becomes non-Gaussian, even though the mean-square displacement grows linearly with time. Here, we report single-particle tracking measurements of the diffusion of colloidal spheres near a planar substrate. Because the local effective diffusivity is known, we have been able to carry out a direct test of this mechanism for diffusion in inhomogeneous media.

Near-field flat focusing mirrors

NASA Astrophysics Data System (ADS)

Cheng, Yu-Chieh; Staliunas, Kestutis

2018-03-01

This article reviews recent progress towards the design of near-field flat focusing mirrors, focusing/imaging light patterns in reflection. An important feature of such flat focusing mirrors is their transverse invariance, as they do not possess any optical axis. We start with a review of the physical background to the different focusing mechanisms of near- and far-field focusing. These near-field focusing devices like flat lenses and the reviewed near-field focusing mirrors can implement planar focusing devices without any optical axis. In contrast, various types of far-field planar focusing devices, such as high-contrast gratings and metasurfaces, unavoidably break the transverse invariance due to their radially symmetrical structures. The particular realizations of near-field flat focusing mirrors including Bragg-like dielectric mirrors and dielectric subwavelength gratings are the main subjects of the review. The first flat focusing mirror was demonstrated with a chirped mirror and was shown to manage an angular dispersion for beam focusing, similar to the management of chromatic dispersion for pulse compression. Furthermore, the reviewed optimized chirped mirror demonstrated a long near-field focal length, hardly achieved by a flat lens or a planar hyperlens. Two more different configurations of dielectric subwavelength gratings that focus a light beam at normal or oblique incidence are also reviewed. We also summarize and compare focusing performance, limitations, and future perspectives between the reviewed flat focusing mirrors and other planar focusing devices including a flat lens with a negative-index material, a planar hyperlens, a high-contrast grating, and a metasurface.

Direct Electrical Probing of Periodic Modulation of Zinc-Dopant Distributions in Planar Gallium Arsenide Nanowires.

PubMed

Choi, Wonsik; Seabron, Eric; Mohseni, Parsian K; Kim, Jeong Dong; Gokus, Tobias; Cernescu, Adrian; Pochet, Pascal; Johnson, Harley T; Wilson, William L; Li, Xiuling

2017-02-28

Selective lateral epitaxial (SLE) semiconductor nanowires (NWs), with their perfect in-plane epitaxial alignment, ability to form lateral complex p-n junctions in situ, and compatibility with planar processing, are a distinctive platform for next-generation device development. However, the incorporation and distribution of impurity dopants in these planar NWs via the vapor-liquid-solid growth mechanism remain relatively unexplored. Here, we present a detailed study of SLE planar GaAs NWs containing multiple alternating axial segments doped with Si and Zn impurities by metalorganic chemical vapor deposition. The dopant profile of the lateral multi-p-n junction GaAs NWs was imaged simultaneously with nanowire topography using scanning microwave impedance microscopy and correlated with infrared scattering-type near-field optical microscopy. Our results provide unambiguous evidence that Zn dopants in the periodically twinned and topologically corrugated p-type segments are preferentially segregated at twin plane boundaries, while Si impurity atoms are uniformly distributed within the n-type segments of the NWs. These results are further supported by microwave impedance modulation microscopy. The density functional theory based modeling shows that the presence of Zn dopant atoms reduces the formation energy of these twin planes, and the effect becomes significantly stronger with a slight increase of Zn concentration. This implies that the twin formation is expected to appear when a threshold planar concentration of Zn is achieved, making the onset and twin periodicity dependent on both Zn concentration and nanowire diameter, in perfect agreement with our experimental observations.

Geometry can provide long-range mechanical guidance for embryogenesis

PubMed Central

Dicko, Mahamar; Saramito, Pierre

2017-01-01

Downstream of gene expression, effectors such as the actomyosin contractile machinery drive embryo morphogenesis. During Drosophila embryonic axis extension, actomyosin has a specific planar-polarised organisation, which is responsible for oriented cell intercalation. In addition to these cell rearrangements, cell shape changes also contribute to tissue deformation. While cell-autonomous dynamics are well described, understanding the tissue-scale behaviour challenges us to solve the corresponding mechanical problem at the scale of the whole embryo, since mechanical resistance of all neighbouring epithelia will feedback on individual cells. Here we propose a novel numerical approach to compute the whole-embryo dynamics of the actomyosin-rich apical epithelial surface. We input in the model specific patterns of actomyosin contractility, such as the planar-polarisation of actomyosin in defined ventro-lateral regions of the embryo. Tissue strain rates and displacements are then predicted over the whole embryo surface according to the global balance of stresses and the material behaviour of the epithelium. Epithelia are modelled using a rheological law that relates the rate of deformation to the local stresses and actomyosin anisotropic contractility. Predicted flow patterns are consistent with the cell flows observed when imaging Drosophila axis extension in toto, using light sheet microscopy. The agreement between model and experimental data indicates that the anisotropic contractility of planar-polarised actomyosin in the ventro-lateral germband tissue can directly cause the tissue-scale deformations of the whole embryo. The three-dimensional mechanical balance is dependent on the geometry of the embryo, whose curved surface is taken into account in the simulations. Importantly, we find that to reproduce experimental flows, the model requires the presence of the cephalic furrow, a fold located anteriorly of the extending tissues. The presence of this geometric feature, through the global mechanical balance, guides the flow and orients extension towards the posterior end. PMID:28346461

Multifunctional Antenna Techniques

DTIC Science & Technology

2015-11-25

the planar structure that can be sufficiently isolated from the radiation mechanism of the antenna and transformed into a TEM transmission line feed...an equivalent transmission line structure, and isolate the physical 5 | P a g e mechanisms responsible for impedance and radiation behavior...gap-fed Archimedean spiral antenna in free space with non-negligible metal width, insertion PMC boundaries to isolate the radiation and propagation

A graphene-based non-volatile memory

NASA Astrophysics Data System (ADS)

Loisel, Loïc.; Maurice, Ange; Lebental, Bérengère; Vezzoli, Stefano; Cojocaru, Costel-Sorin; Tay, Beng Kang

2015-09-01

We report on the development and characterization of a simple two-terminal non-volatile graphene switch. After an initial electroforming step during which Joule heating leads to the formation of a nano-gap impeding the current flow, the devices can be switched reversibly between two well-separated resistance states. To do so, either voltage sweeps or pulses can be used, with the condition that VSET < VRESET , where SET is the process decreasing the resistance and RESET the process increasing the resistance. We achieve reversible switching on more than 100 cycles with resistance ratio values of 104. This approach of graphene memory is competitive as compared to other graphene approaches such as redox of graphene oxide, or electro-mechanical switches with suspended graphene. We suggest a switching model based on a planar electro-mechanical switch, whereby electrostatic, elastic and friction forces are competing to switch devices ON and OFF, and the stability in the ON state is achieved by the formation of covalent bonds between the two stretched sides of the graphene, hence bridging the nano-gap. Developing a planar electro-mechanical switch enables to obtain the advantages of electro-mechanical switches while avoiding most of their drawbacks.

The effective compliance of spatially evolving planar wing-cracks

NASA Astrophysics Data System (ADS)

Ayyagari, R. S.; Daphalapurkar, N. P.; Ramesh, K. T.

2018-02-01

We present an analytic closed form solution for anisotropic change in compliance due to the spatial evolution of planar wing-cracks in a material subjected to largely compressive loading. A fully three-dimensional anisotropic compliance tensor is defined and evaluated considering the wing-crack mechanism, using a mixed-approach based on kinematic and energetic arguments to derive the coefficients in incremental compliance. Material, kinematic and kinetic parametric influences on the increments in compliance are studied in order to understand their physical implications on material failure. Model verification is carried out through comparisons to experimental uniaxial compression results to showcase the predictive capabilities of the current study.

Progress and challenges in understanding planar cell polarity signaling.

PubMed

Axelrod, Jeffrey D

2009-10-01

During development, epithelial cells in some tissues acquire a polarity orthogonal to their apical-basal axis. This polarity, referred to as planar cell polarity (PCP), or tissue polarity, is essential for the normal physiological function of many epithelia. Early studies of PCP focused on insect epithelia (Lawrence, 1966 [1]), and the earliest genetic analyses were carried out in Drosophila (Held et al., 1986; Gubb and Garcia-Bellido, 1982 [2,3]). Indeed, most of our mechanistic understanding of PCP derives from the ongoing use of Drosophila as a model system. However, a range of medically important developmental defects and physiological processes are under the control of PCP mechanisms that appear to be at least partially conserved, driving considerable interest in studying PCP both in Drosophila and in vertebrate model systems. Here, I present a model of the PCP signaling mechanism based on studies in Drosophila. I highlight two areas in which our understanding is deficient, and which lead to current confusion in the literature. Future studies that shed light on these areas will substantially enhance our understanding of the fascinating yet challenging problem of understanding the mechanisms that generate PCP.

Clustering and negative feedback by endocytosis in planar cell polarity signaling is modulated by ubiquitinylation of prickle.

PubMed

Cho, Bomsoo; Pierre-Louis, Gandhy; Sagner, Andreas; Eaton, Suzanne; Axelrod, Jeffrey D

2015-05-01

The core components of the planar cell polarity (PCP) signaling system, including both transmembrane and peripheral membrane associated proteins, form asymmetric complexes that bridge apical intercellular junctions. While these can assemble in either orientation, coordinated cell polarization requires the enrichment of complexes of a given orientation at specific junctions. This might occur by both positive and negative feedback between oppositely oriented complexes, and requires the peripheral membrane associated PCP components. However, the molecular mechanisms underlying feedback are not understood. We find that the E3 ubiquitin ligase complex Cullin1(Cul1)/SkpA/Supernumerary limbs(Slimb) regulates the stability of one of the peripheral membrane components, Prickle (Pk). Excess Pk disrupts PCP feedback and prevents asymmetry. We show that Pk participates in negative feedback by mediating internalization of PCP complexes containing the transmembrane components Van Gogh (Vang) and Flamingo (Fmi), and that internalization is activated by oppositely oriented complexes within clusters. Pk also participates in positive feedback through an unknown mechanism promoting clustering. Our results therefore identify a molecular mechanism underlying generation of asymmetry in PCP signaling.

Fabrication and characterization of 3C-silicon carbide micro sensor for wireless blood pressure measurements

NASA Astrophysics Data System (ADS)

Basak, Nupur

A potentially implantable single crystal 3C-SiC pressure sensor for blood pressure measurement was designed, simulated, fabricated, characterized and optimized. This research uses a single crystal 3C-SiC, for the first time, to demonstrate its application as a blood pressure measurement sensor. The sensor, which uses the epitaxial grown 3C-SiC membrane to measure changes in pressure, is designed to be wireless, biocompatible and linear. The SiC material was chosen for its superior physical, chemical and mechanical properties; the capacitive sensor uses a 3C-SiC membrane as one of the electrodes; and, the sensor system is wireless for comfort and to allow for convenient reading of real-time pressure data (wireless communication is enabled by connecting the sensor parallel to a planar inductor). Together, the variable capacitive sensor and planar inductor create a pressure sensitive resonant circuit. The sensor system described above allows for implantation into a human patient's body, after which the planar inductor can be coupled with an external inductor to receive data for real-time blood pressure measurement. Electroplating, thick photo-resist characterization, RIE etching, oxidation, CVD, chemical mechanical polishing and wafer bonding were optimized during the process of fabricating the sensor system and, in addition to detailing the sensor system simulation and characterization; the optimized processes are detailed in the dissertation. This absolute pressure sensor is designed to function optimally within the human blood pressure range of 50-350mmHg. The layout and modeling of the sensor uses finite element analysis (FEA) software. The simulations for membrane deflection, stress analysis and electro-mechanical analysis are performed for 100 μm2 and 400μm2sensors. The membrane deflection-pressure, capacitance-pressure and resonant frequency-pressure graphs were obtained, and detailed in the dissertation, along with the planar inductor simulation for differently sized inductors. Ultimately, an optimized sensor with a size of 400μm2 was chosen because of its high sensitivity. The sensor, and the planar inductor, which is 3mm 2, is comparable to the presently researched implantable chip size. The measured inductance of the gold electroplated inductor is 0.371μH. The capacitance changes from 0.934 pF to 0.997pF with frequency shift of 248MHz to 256 MHz. The sensitivity of the sensor is found to be 0.21 fF/mmHg or 27.462 kHz/mmHg with an average non-linearity of 0.23216%.

Feasibility of motion laws for planar one degree of freedom linkage mechanisms at dead point configurations

NASA Astrophysics Data System (ADS)

Lores García, E.; Veciana Fontanet, J. M.; Jordi Nebot, L.

2018-01-01

This paper proposes an analytical solution of the Inverse Kinematics (IK) problem at dead point configurations for any planar one degree of freedom linkage mechanism, with regard to the continuity Cn of the motion law. The systems analyzed are those whose elements are linked with lower pairs and do not present redundancies. The study aims to provide the user with some rules to facilitate the design of feasible motion profiles to be reproduced by conventional electrical actuators at these configurations. During the last decades, several methods and techniques have been developed to study this specific configuration. However, these techniques are mainly focused on solving numerically the IK indeterminacy, rather than analyzing the motion laws that the mechanisms are able to perform at these particular configurations. The analysis presented in this paper has been carried out differentiating and applying l'Hôpital's rule to the system of constraint equations ϕ (q) of the mechanism. The study also considers the feasibility of the time-domain profiles to be reproduced with conventional electrical actuators (i.e. AC/DC motors, linear actuators, etc.). To show the usefulness and effectiveness of the method, the development includes the analytical application and numerical simulations for two common one degree of freedom systems: a slider-crank and a four linkage mechanisms. Finally, experimental results are presented on a four linkage mechanism test bed.

Transient Effects in Planar Solidification of Dilute Binary Alloys

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin; Volz, Martin P.

2008-01-01

The initial transient during planar solidification of dilute binary alloys is studied in the framework of the boundary integral method that leads to the non-linear Volterra integral governing equation. An analytical solution of this equation is obtained for the case of a constant growth rate which constitutes the well-known Tiller's formula for the solute transient. The more physically relevant, constant ramping down temperature case has been studied both numerically and analytically. In particular, an asymptotic analytical solution is obtained for the initial transient behavior. A numerical technique to solve the non-linear Volterra equation is developed and the solution is obtained for a family of the governing parameters. For the rapid solidification condition, growth rate spikes have been observed even for the infinite kinetics model. When recirculating fluid flow is included into the analysis, the spike feature is dramatically diminished. Finally, we have investigated planar solidification with a fluctuating temperature field as a possible mechanism for frequently observed solute trapping bands.

The Peierls stress of the moving [Formula: see text] screw dislocation in Ta.

PubMed

Liu, Ruiping; Wang, Shaofeng; Wu, Xiaozhi

2009-08-26

The Peierls stress of the moving [Formula: see text] screw dislocation with a planar and non-dissociated core structure in Ta has been calculated. The elastic strain energy which is associated with the discrete effect of the lattice and ignored in classical Peierls-Nabarro (P-N) theory has been taken into account in calculating the Peierls stress, and it can make the Peierls stress become smaller. The Peierls stress we obtain is very close to the experimental data. As shown in the numerical calculations and atomistic simulations, the core structure of the screw dislocation undergoes significant changes under the explicit stress before the screw dislocation moves. Moreover, the mechanism of the screw dislocation is revealed by our results and the experimental data that the screw dislocation retracts its extension in three {110} planes and transforms its dissociated core structure into a planar configuration. Therefore, the core structure of the moving [Formula: see text] screw dislocation in Ta is proposed to be planar.

Reduced cytotoxicity in PCB-exposed Chinese Hamster Ovary (CHO) cells pretreated with vitamin E.

PubMed

Murati, Teuta; Šimić, Branimir; Pleadin, Jelka; Vukmirović, Maja; Miletić, Marina; Durgo, Ksenija; Kniewald, Jasna; Kmetič, Ivana

2017-01-01

The aim of this study was to evaluate protective effects of vitamin E (50 -150 μM) in ovary cells upon cytotoxic effects induced by two structurally distinct PCB congeners - planar "dioxin-like" PCB 77 and non-planar di-ortho-substituted PCB 153 with an emphasis on identifying differences in the mechanism of vitamin E action depending on the structure of congeners. Application of three bioassays confirmed that PCBs decrease ovarian cell proliferation with slightly profound effects of PCB 77. PCB - induced ROS production and lipid peroxidation were significant for both congeners with also more noticeable effect for PCB 77. Vitamin E pre-incubation has improved viability of cells, reduced ROS formation and lipid peroxidation induced by PCBs' treatment. Preincubation with vitamin E was more effective when cells where treated with non-planar PCB 153. Altogether, vitamin E action was protective, congener specific and more effective when ovary cells were exposed to ortho-substituted PCB congener. Copyright © 2016 Elsevier Ltd. All rights reserved.

Insight into Evolution, Processing and Performance of Multi-length-scale Structures in Planar Heterojunction Perovskite Solar Cells.

PubMed

Huang, Yu-Ching; Tsao, Cheng-Si; Cho, Yi-Ju; Chen, Kuan-Chen; Chiang, Kai-Ming; Hsiao, Sheng-Yi; Chen, Chang-Wen; Su, Chun-Jen; Jeng, U-Ser; Lin, Hao-Wu

2015-09-04

The structural characterization correlated to the processing control of hierarchical structure of planar heterojunction perovskite layer is still incomplete due to the limitations of conventional microscopy and X-ray diffraction. This present study performed the simultaneously grazing-incidence small-angle scattering and wide-angle scattering (GISAXS/GIWAXS) techniques to quantitatively probe the hierarchical structure of the planar heterojunction perovskite solar cells. The result is complementary to the currently microscopic study. Correlation between the crystallization behavior, crystal orientation, nano- and meso-scale internal structure and surface morphology of perovskite film as functions of various processing control parameters is reported for the first time. The structural transition from the fractal pore network to the surface fractal can be tuned by the chloride percentage. The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance. The result can provide the insight into formation mechanism and rational synthesis design.

Insight into Evolution, Processing and Performance of Multi-length-scale Structures in Planar Heterojunction Perovskite Solar Cells

NASA Astrophysics Data System (ADS)

Huang, Yu-Ching; Tsao, Cheng-Si; Cho, Yi-Ju; Chen, Kuan-Chen; Chiang, Kai-Ming; Hsiao, Sheng-Yi; Chen, Chang-Wen; Su, Chun-Jen; Jeng, U.-Ser; Lin, Hao-Wu

2015-09-01

The structural characterization correlated to the processing control of hierarchical structure of planar heterojunction perovskite layer is still incomplete due to the limitations of conventional microscopy and X-ray diffraction. This present study performed the simultaneously grazing-incidence small-angle scattering and wide-angle scattering (GISAXS/GIWAXS) techniques to quantitatively probe the hierarchical structure of the planar heterojunction perovskite solar cells. The result is complementary to the currently microscopic study. Correlation between the crystallization behavior, crystal orientation, nano- and meso-scale internal structure and surface morphology of perovskite film as functions of various processing control parameters is reported for the first time. The structural transition from the fractal pore network to the surface fractal can be tuned by the chloride percentage. The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance. The result can provide the insight into formation mechanism and rational synthesis design.

Numerical modeling of the early interaction of a planar shock with a dense particle field

NASA Astrophysics Data System (ADS)

Regele, Jonathan; Blanquart, Guillaume

2011-11-01

Dense compressible multiphase flows are of interest for multiphase turbomachinary and energetic material detonations. Still, there is little understanding of the detailed interaction mechanisms between shock waves and dense (particle volume fraction αd > 0 . 001) particle fields. A recent experimental study [Wagner et al, AIAA Aero. Sci., Orlando, 2011-188] has focused on the impingement of a planar shock wave on a dense particle curtain. In the present work, numerical solutions of the Euler equations in one and two dimensions are performed for a planar shock wave impinging on a fixed particle curtain and are compared to the experimental data for early times. Comparison of the one- and two-dimensional results demonstrate that the one-dimensional description captures the large scale flow behavior, but is inadequate to capture all the details observed in the experiments. The two-dimensional solutions are shown to reproduce the experimentally observed flow structures and provide insight into how these details originate.

Surface Plasmon Polariton-Assisted Long-Range Exciton Transport in Monolayer Semiconductor Lateral Heterostructure

NASA Astrophysics Data System (ADS)

Shi, Jinwei; Lin, Meng-Hsien; Chen, Yi-Tong; Estakhri, Nasim Mohammadi; Tseng, Guo-Wei; Wang, Yanrong; Chen, Hung-Ying; Chen, Chun-An; Shih, Chih-Kang; Alã¹, Andrea; Li, Xiaoqin; Lee, Yi-Hsien; Gwo, Shangjr

Recently, two-dimensional (2D) semiconductor heterostructures, i.e., atomically thin lateral heterostructures (LHSs) based on transition metal dichalcogenides (TMDs) have been demonstrated. In an optically excited LHS, exciton transport is typically limited to a rather short spatial range ( 1 micron). Furthermore, additional losses may occur at the lateral interfacial regions. Here, to overcome these challenges, we experimentally implement a planar metal-oxide-semiconductor (MOS) structure by placing a monolayer of WS2/MoS2 LHS on top of an Al2O3 capped Ag single-crystalline plate. We found that the exciton transport range can be extended to tens of microns. The process of long-range exciton transport in the MOS structure is confirmed to be mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, which allows a cascaded energy transfer process. Thus, the planar MOS structure provides a platform seamlessly combining 2D light-emitting materials with plasmonic planar waveguides, offering great potential for developing integrated photonic/plasmonic functionalities.

Free energy surfaces for the interaction of D-glucose with planar aromatic groups in aqueous solution

NASA Astrophysics Data System (ADS)

Wohlert, Jakob; Schnupf, Udo; Brady, John W.

2010-10-01

Multidimensional potentials of mean force for the interactions in aqueous solution of both anomers of D-glucopyranose with two planar aromatic molecules, indole and para-methyl-phenol, have been calculated using molecular dynamics simulations with umbrella sampling and were subsequently used to estimate binding free energies. Indole and para-methyl-phenol serve as models for the side chains of the amino acids tryptophan and tyrosine, respectively. In all cases, a weak affinity between the glucose molecules and the flat aromatic surfaces was found. The global minimum for these interactions was found to be for the case when the pseudoplanar face of β-D-glucopyranose is stacked against the planar surfaces of the aromatic residues. The calculated binding free energies are in good agreement with both experiment and previous simulations. The multidimensional free energy maps suggest a mechanism that could lend kinetic stability to the complexes formed by sugars bound to sugar-binding proteins.

Design principles for single standing nanowire solar cells: going beyond the planar efficiency limits.

PubMed

Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

2014-05-09

Semiconductor nanowires (NWs) have long been used in photovoltaic applications but restricted to approaching the fundamental efficiency limits of the planar devices with less material. However, recent researches on standing NWs have started to reveal their potential of surpassing these limits when their unique optical property is utilized in novel manners. Here, we present a theoretical guideline for maximizing the conversion efficiency of a single standing NW cell based on a detailed study of its optical absorption mechanism. Under normal incidence, a standing NW behaves as a dielectric resonator antenna, and its optical cross-section shows its maximum when the lowest hybrid mode (HE11δ) is excited along with the presence of a back-reflector. The promotion of the cell efficiency beyond the planar limits is attributed to two effects: the built-in concentration caused by the enlarged optical cross-section, and the shifting of the absorption front resulted from the excited mode profile. By choosing an optimal NW radius to support the HE11δ mode within the main absorption spectrum, we demonstrate a relative conversion-efficiency enhancement of 33% above the planar cell limit on the exemplary a-Si solar cells. This work has provided a new basis for designing and analyzing standing NW based solar cells.

Transient Evolution of a Planar Diffusion Flame Aft of a Translating Flat Plate

NASA Technical Reports Server (NTRS)

Gokoglu, Suleyman A.

2003-01-01

The high degree of spatial symmetry of a planar diffusion flame affords great simplifications for experimental and modeling studies of gaseous fuel combustion. Particularly, in a microgravity environment, where buoyancy effects are negligible, an effectively strain-rate-free, vigorous flame may be obtained. Such a flame can also provide long residence times and large length scales for practical probing of flame structures and soot processes. This 2-D numerical study explores the feasibility of establishing such a planar diffusion flame in an enclosed container utilizing a realistic test protocol for a microgravity experiment. Fuel and oxygen mixtures, initially segregated into two half-volumes of a squat rectangular container by a thin separator, are ignited as soon as a flammable mixture is formed in the wake of the separator withdrawn in the centerplane. A triple-flame ensues that propagates behind the trailing edge of the separator. The results of calculations show that the mechanically- and thermally-induced convection decays in about two seconds. The establishment of a planar diffusion flame after this period seems feasible in the central region of the container with sufficient quantities of reactants left over for subsequent studies. An analysis of the flame initiation and formation process suggests how the feasibility of creating such a flame can be further improved.

Design principles for single standing nanowire solar cells: going beyond the planar efficiency limits

PubMed Central

Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

2014-01-01

Semiconductor nanowires (NWs) have long been used in photovoltaic applications but restricted to approaching the fundamental efficiency limits of the planar devices with less material. However, recent researches on standing NWs have started to reveal their potential of surpassing these limits when their unique optical property is utilized in novel manners. Here, we present a theoretical guideline for maximizing the conversion efficiency of a single standing NW cell based on a detailed study of its optical absorption mechanism. Under normal incidence, a standing NW behaves as a dielectric resonator antenna, and its optical cross-section shows its maximum when the lowest hybrid mode (HE11δ) is excited along with the presence of a back-reflector. The promotion of the cell efficiency beyond the planar limits is attributed to two effects: the built-in concentration caused by the enlarged optical cross-section, and the shifting of the absorption front resulted from the excited mode profile. By choosing an optimal NW radius to support the HE11δ mode within the main absorption spectrum, we demonstrate a relative conversion-efficiency enhancement of 33% above the planar cell limit on the exemplary a-Si solar cells. This work has provided a new basis for designing and analyzing standing NW based solar cells. PMID:24810591

Ultrafast carrier dynamics in GaN/InGaN multiple quantum wells nanorods

NASA Astrophysics Data System (ADS)

Chen, Weijian; Wen, Xiaoming; Latzel, Michael; Yang, Jianfeng; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Christiansen, Silke; Conibeer, Gavin

2018-01-01

GaN/InGaN multiple quantum wells (MQW) is a promising material for high-efficiency solid-state lighting. Ultrafast optical pump-probe spectroscopy is an important characterization technique for examining fundamental phenomena in semiconductor nanostructure with sub-picosecond resolution. In this study, ultrafast exciton and charge carrier dynamics in GaN/InGaN MQW planar layer and nanorod are investigated using femtosecond transient absorption (TA) techniques at room temperature. Here nanorods are fabricated by etching the GaN/InGaN MQW planar layers using nanosphere lithography and reactive ion etching. Photoluminescence efficiency of the nanorods have been proved to be much higher than that of the planar layers, but the mechanism of the nanorod structure improvement of PL efficiency is not adequately studied. By comparing the TA profile of the GaN/InGaN MQW planar layers and nanorods, the impact of surface states and nanorods lateral confinement in the ultrafast carrier dynamics of GaN/InGaN MQW is revealed. The nanorod sidewall surface states have a strong influence on the InGaN quantum well carrier dynamics. The ultrafast relaxation processes studied in this GaN/InGaN MQW nanostructure is essential for further optimization of device application.

Epithelial rotation is preceded by planar symmetry breaking of actomyosin and protects epithelial tissue from cell deformations.

PubMed

Viktorinová, Ivana; Henry, Ian; Tomancak, Pavel

2017-11-01

Symmetry breaking is involved in many developmental processes that form bodies and organs. One of them is the epithelial rotation of developing tubular and acinar organs. However, how epithelial cells move, how they break symmetry to define their common direction, and what function rotational epithelial motions have remains elusive. Here, we identify a dynamic actomyosin network that breaks symmetry at the basal surface of the Drosophila follicle epithelium of acinar-like primitive organs, called egg chambers, and may represent a candidate force-generation mechanism that underlies the unidirectional motion of this epithelial tissue. We provide evidence that the atypical cadherin Fat2, a key planar cell polarity regulator in Drosophila oogenesis, directs and orchestrates transmission of the intracellular actomyosin asymmetry cue onto a tissue plane in order to break planar actomyosin symmetry, facilitate epithelial rotation in the opposite direction, and direct the elongation of follicle cells. In contrast, loss of this rotational motion results in anisotropic non-muscle Myosin II pulses that are disorganized in plane and causes cell deformations in the epithelial tissue of Drosophila eggs. Our work demonstrates that atypical cadherins play an important role in the control of symmetry breaking of cellular mechanics in order to facilitate tissue motion and model epithelial tissue. We propose that their functions may be evolutionarily conserved in tubular/acinar vertebrate organs.

Epithelial rotation is preceded by planar symmetry breaking of actomyosin and protects epithelial tissue from cell deformations

PubMed Central

Henry, Ian; Tomancak, Pavel

2017-01-01

Symmetry breaking is involved in many developmental processes that form bodies and organs. One of them is the epithelial rotation of developing tubular and acinar organs. However, how epithelial cells move, how they break symmetry to define their common direction, and what function rotational epithelial motions have remains elusive. Here, we identify a dynamic actomyosin network that breaks symmetry at the basal surface of the Drosophila follicle epithelium of acinar-like primitive organs, called egg chambers, and may represent a candidate force-generation mechanism that underlies the unidirectional motion of this epithelial tissue. We provide evidence that the atypical cadherin Fat2, a key planar cell polarity regulator in Drosophila oogenesis, directs and orchestrates transmission of the intracellular actomyosin asymmetry cue onto a tissue plane in order to break planar actomyosin symmetry, facilitate epithelial rotation in the opposite direction, and direct the elongation of follicle cells. In contrast, loss of this rotational motion results in anisotropic non-muscle Myosin II pulses that are disorganized in plane and causes cell deformations in the epithelial tissue of Drosophila eggs. Our work demonstrates that atypical cadherins play an important role in the control of symmetry breaking of cellular mechanics in order to facilitate tissue motion and model epithelial tissue. We propose that their functions may be evolutionarily conserved in tubular/acinar vertebrate organs. PMID:29176774

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spatial-temporal distribution of a mechanical load resulting from interaction of laser radiation with a barrier (analytic model)

NASA Astrophysics Data System (ADS)

Fedyushin, B. T.

1992-01-01

The concepts developed earlier are used to propose a simple analytic model describing the spatial-temporal distribution of a mechanical load (pressure, impulse) resulting from interaction of laser radiation with a planar barrier surrounded by air. The correctness of the model is supported by a comparison with experimental results.

Reaction mechanism of the acidic hydrolysis of highly twisted amides: Rate acceleration caused by the twist of the amide bond.

PubMed

Mujika, Jon I; Formoso, Elena; Mercero, Jose M; Lopez, Xabier

2006-08-03

We present an ab initio study of the acid hydrolysis of a highly twisted amide and a planar amide analogue. The aim of these studies is to investigate the effect that the twist of the amide bond has on the reaction barriers and mechanism of acid hydrolysis. Concerted and stepwise mechanisms were investigated using density functional theory and polarizable continuum model calculations. Remarkable differences were observed between the mechanism of twisted and planar amide, due mainly to the preference for N-protonation of the former and O-protonation of the latter. In addition, we were also able to determine that the hydrolytic mechanism of the twisted amide will be pH dependent. Thus, there is a preference for a stepwise mechanism with formation of an intermediate in the acid hydrolysis, whereas the neutral hydrolysis undergoes a concerted-type mechanism. There is a nice agreement between the characterized intermediate and available X-ray data and a good agreement with the kinetically estimated rate acceleration of hydrolysis with respect to analogous undistorted amide compounds. This work, along with previous ab initio calculations, describes a complex and rich chemistry for the hydrolysis of highly twisted amides as a function of pH. The theoretical data provided will allow for a better understanding of the available kinetic data of the rate acceleration of amides upon twisting and the relation of the observed rate acceleration with intrinsic differential reactivity upon loss of amide bond resonance.

What is Scanner and NonScanner?

Atmospheric Science Data Center

2014-12-08

... instruments specifically designed by a team of electronic, thermal, and mechanical experts, built and integrated with the ERBS and NOAA ... of three co-planar detectors (longwave, shortwave and total energy), all of which scan from one limb of the Earth to the other, across the ...

Higher-order continuation for the determination of robot workspace boundaries

NASA Astrophysics Data System (ADS)

Hentz, Gauthier; Charpentier, Isabelle; Renaud, Pierre

2016-02-01

In the medical and surgical fields, robotics may be of great interest for safer and more accurate procedures. Space constraints for a robotic assistant are however strict. Therefore, roboticists study non-conventional mechanisms with advantageous size/workspace ratios. The determination of mechanism workspace, and primarily its boundaries, is thus of major importance. This Note builds on boundary equation definition, continuation and automatic differentiation to propose a general, accurate, fast and automated method for the determination of mechanism workspace. The method is illustrated with a planar RRR mechanism and a three-dimensional Orthoglide parallel mechanism.

Nanohelices from planar polymer self-assembled in carbon nanotubes

PubMed Central

Fu, Hongjin; Xu, Shuqiong; Li, Yunfang

2016-01-01

The polymer possessing with planar structure can be activated and guided to encapsulate the inner space of SWNT and form a helix through van der Waals interaction and the π-π stacking effect between the polymer and the inner surface of SWNT. The SWNT size, the nanostructure and flexibility of polymer chain are all determine the final structures. The basic interaction between the polymer and the nanotubes is investigated, and the condition and mechanism of the helix-forming are explained particularly. Hybrid polymers improve the ability of the helix formation. This study provides scientific basis for fabricating helical polymers encapsulated in SWNTs and eventually on their applications in various areas. PMID:27440493

The influence of morphology on charge transport/recombination dynamics in planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Yu, Man; Wang, Yi; Wang, Hao-Yi; Han, Jun; Qin, Yujun; Zhang, Jian-Ping; Ai, Xi-Cheng

2016-10-01

The photovoltaic performance of planar perovskite solar cell is significantly influenced by the morphology of perovskite film. In this work, five kinds of devices with different perovskite film morphologies were prepared by varying the concentration of CH3NH3Cl in precursor solutions. We found that best morphology of perovskite film results in the excellent photovoltaic performance with an average efficiency of 15.52% and a champion efficiency of 16.38%. Transient photovoltage and photocurrent measurements are performed to elucidate the mechanism of photoelectric conversion processes, which shows that the charge recombination is effectively suppressed and the charge transport is obviously promoted by optimized morphology.

Physical mechanism for flat-to-lenticular lens conversion in homogeneous liquid crystal cell with periodically undulated electrode.

PubMed

Na, Jun-Hee; Park, Seung Chul; Kim, Se-Um; Choi, Yoonseuk; Lee, Sin-Doo

2012-01-16

A convertible lenticular liquid crystal (LC) lens architecture is demonstrated using an index-matched planarization layer on a periodically undulated electrode for the homogeneous alignment of an LC. It is found that the in-plane component of the electric field by the undulated electrode plays a primary role in the flat-to-lens effect while the out-of-plane component contributes to the anchoring enhancement of the LC molecules in the surface layer. Our LC device having an index-matched planarization layer on the undulated electrode is capable of achieving the electrical tunability from the flat surface to the lenticular lens suitable for 2D/3D convertible displays.

Multi-axis planar slide system

DOEpatents

Bieg, Lothar F.

2002-01-01

An apparatus for positioning an item that provides two-dimensional, independent orthogonal motion of a platform in a X-Y plane. A pair of master and slave disks engages opposite sides of the platform. Rotational drivers are connected to master disks so the disks rotate eccentrically about axes of rotation. Opposing slave disks are connected to master disks on opposite sides of the platform by a timing belt, or are electronically synchronized together using stepper motors, to effect coordinated motion. The coordinated eccentric motion of the pairs of master/slave disks compels smooth linear motion of the platform in the X-Y plane without backlash. The apparatus can be a planar mechanism implemented in a MEMS device.

Single nanowire green InGaN/GaN light emitting diodes

NASA Astrophysics Data System (ADS)

Zhang, Guogang; Li, Ziyuan; Yuan, Xiaoming; Wang, Fan; Fu, Lan; Zhuang, Zhe; Ren, Fang-Fang; Liu, Bin; Zhang, Rong; Tan, Hark Hoe; Jagadish, Chennupati

2016-10-01

Single nanowire (NW) green InGaN/GaN light-emitting diodes (LEDs) were fabricated by top-down etching technology. The electroluminescence (EL) peak wavelength remains approximately constant with an increasing injection current in contrast to a standard planar LED, which suggests that the quantum-confined Stark effect is significantly reduced in the single NW device. The strain relaxation mechanism is studied in the single NW LED using Raman scattering analysis. As compared to its planar counterpart, the EL peak of the NW LED shows a redshift, due to electric field redistribution as a result of changes in the cavity mode pattern after metallization. Our method has important implication for single NW optoelectronic device applications.

Nanoscale interfacial defect shedding in a growing nematic droplet.

PubMed

Gurevich, Sebastian; Provatas, Nikolas; Rey, Alejandro

2017-08-01

Interfacial defect shedding is the most recent known mechanism for defect formation in a thermally driven isotropic-to-nematic phase transition. It manifests in nematic-isotropic interfaces going through an anchoring switch. Numerical computations in planar geometry established that a growing nematic droplet can undergo interfacial defect shedding, nucleating interfacial defect structures that shed into the bulk as +1/2 point defects. By extending the study of interfacial defect shedding in a growing nematic droplet to larger length and time scales, and to three dimensions, we unveil an oscillatory growth mode involving shape and anchoring transitions that results in a controllable regular distributions of point defects in planar geometry, and complex structures of disclination lines in three dimensions.

Genetic analysis of ectopic growth suppression during planar growth of integuments mediated by the Arabidopsis AGC protein kinase UNICORN.

PubMed

Enugutti, Balaji; Schneitz, Kay

2013-01-02

The coordination of growth within a tissue layer is of critical importance for tissue morphogenesis. For example, cells within the epidermis undergo stereotypic cell divisions that are oriented along the plane of the layer (planar growth), thereby propagating the layered epidermal structure. Little is known about the developmental control that regulates such planar growth in plants. Recent evidence suggested that the Arabidopsis AGC VIII protein kinase UNICORN (UCN) maintains planar growth by suppressing the formation of ectopic multicellular protrusions in several floral tissues including integuments. In the current model UCN controls this process during integument development by directly interacting with the ABERRANT TESTA SHAPE (ATS) protein, a member of the KANADI (KAN) family of transcription factors, thereby repressing its activity. Here we report on the further characterization of the UCN mechanism. Phenotypic analysis of flowers of ucn-1 plants impaired in floral homeotic gene activity revealed that any of the four floral whorls could produce organs carrying ucn-1 protrusions. The ectopic outgrowths of ucn integuments did not accumulate detectable signals of the auxin and cytokinin reporters DR5rev::GFP and ARR5::GUS, respectively. Furthermore, wild-type and ucn-1 seedlings showed similarly strong callus formation upon in vitro culture on callus-inducing medium. We also show that ovules of ucn-1 plants carrying the dominant ats allele sk21-D exhibited more pronounced protrusion formation. Finally ovules of ucn-1 ett-1 double mutants and ucn-1 ett-1 arf4-1 triple mutants displayed an additive phenotype. These data deepen the molecular insight into the UCN-mediated control of planar growth during integument development. The presented evidence indicates that UCN downstream signaling does not involve the control of auxin or cytokinin homeostasis. The results also reveal that UCN interacts with ATS independently of an ATS/ETT complex required for integument initiation and they further emphasize the necessity to balance UCN and ATS proteins during maintenance of planar growth in integuments.

Type 0 open string amplitudes and the tensionless limit

NASA Astrophysics Data System (ADS)

Rojas, Francisco

2014-12-01

The sum over planar multiloop diagrams in the NS + sector of type 0 open strings in flat spacetime has been proposed by Thorn as a candidate to resolve nonperturbative issues of gauge theories in the large N limit. With S U (N ) Chan-Paton factors, the sum over planar open string multiloop diagrams describes the 't Hooft limit N →∞ with N gs2 held fixed. By including only planar diagrams in the sum the usual mechanism for the cancellation of loop divergences (which occurs, for example, among the planar and Möbius strip diagrams by choosing a specific gauge group) is not available and a renormalization procedure is needed. In this article the renormalization is achieved by suspending total momentum conservation by an amount p ≡∑ i n ki≠0 at the level of the integrands in the integrals over the moduli and analytically continuing them to p =0 at the very end. This procedure has been successfully tested for the 2 and 3 gluon planar loop amplitudes by Thorn. Gauge invariance is respected and the correct running of the coupling in the limiting gauge field theory was also correctly obtained. In this article we extend those results in two directions. First, we generalize the renormalization method to an arbitrary n -gluon planar loop amplitude giving full details for the 4-point case. One of our main results is to provide a fully renormalized amplitude which is free of both UV and the usual spurious divergences leaving only the physical singularities in it. Second, using the complete renormalized amplitude, we extract the high-energy scattering regime at fixed angle (tensionless limit). Apart from obtaining the usual exponential falloff at high energies, we compute the full dependence on the scattering angle which shows the existence of a smooth connection between the Regge and hard scattering regimes.

Mechanisms of flexural flow folding of competent single-layers as evidenced by folded fibrous dolomite veins

NASA Astrophysics Data System (ADS)

Torremans, Koen; Muchez, Philippe; Sintubin, Manuel

2014-12-01

Flexural flow is thought unlikely to occur in naturally deformed, competent isotropic single-layers. In this study we discuss a particular case of folded bedding-parallel fibrous dolomite veins in shale, in which the internal strain pattern and microstructural deformation features provide new insights in the mechanisms enabling flexural flow folding. Strain in the pre-folding veins is accommodated by two main mechanisms: intracrystalline deformation by bending and intergranular deformation with bookshelf rotation of dolomite fibres. The initially orthogonal dolomite fibres allowed a reconstruction of the strain distribution across the folded veins. This analysis shows that the planar mechanical anisotropy created by the fibres causes the veins to approximate flexural flow. During folding, synkinematic veins overgrow the pre-folding fibrous dolomite veins. Microstructures and dolomite growth morphologies reflect growth during progressive fold evolution, with evidence for flexural slip at fold lock-up. Homogeneous flattening, as evidenced by disjunctive axial-planar cleavage, subsequently modified these folds from class 1B to 1C folds. Our study shows that the internal vein fabric has a first-order influence on folding kinematics. Moreover, the fibrous dolomite veins show high viscosity contrasts with the shale matrix, essential in creating transient permeability for subsequent mineralising stages in the later synkinematic veins during progressive folding.

Effects of fO2, fH2O and aoxide on formation and density of extended planar defects in olivine

NASA Astrophysics Data System (ADS)

Burgess, K.; Cooper, R. F.

2011-12-01

Melt inclusions are used in geochemistry to inform our understanding of many physiochemical processes taking place in the mantle, such as melting, melt-rock interactions and magma mixing. Fundamental to this interpretation of melt inclusions is the assumption that they act as closed systems, i.e., they are chemically isolated after trapping and preserve primitive magma compositions. However, recent work indicates that volatiles (e.g., H and F) can be rapidly reset [Portnyagin et al., 2008], and the diffusion mechanisms and rates in tracer diffusion experiments, specifically of REEs, are a matter of some debate [Spandler and O'Neill, 2010; Cherniak, 2010]. The compendium of observations and experiments suggests a role of planar extended defects in effecting and affecting diffusion kinetics in olivine. Planar extended defects are the exothermic condensation of charged point defects into two-dimensional structures, their third dimension insufficient (i.e., sub-unit cell) to describe them as a unique phase. These planar defects, in a manner similar to mechanisms of "pipe" diffusion along dislocations and of grain boundary diffusion, can lead to measured diffusivities far greater than the lattice diffusivity, and their overall effect on flux is proportional to their spatial density [cf. Hart, 1957]. High-resolution TEM and AEM investigation of experimental olivine-basalt samples show the presence of planar defects near the olivine-melt interface, with the area fraction of the high-contrast defects in the images being greatest at high fO2 and/or fH2O while temperature has an effect on the defect dimensions but not total areal density. EDS analysis of the interface regions indicate high Ti/Ca and Ti/Al ratios compared to the glass; the stability of intercalated humite-type defects in olivine, a planar defect type found in some natural olivines [e.g., Risold et al., 2001; Hermann et al., 2007], is increased to higher temperature by the incorporation of Ti. Activities of oxides clearly affect the presence and density of the defects. Olivine-ilmenite experiments were also carried out in varying fO2 and fH2O conditions. Thermodynamic calculations for concentrations of point defects, defect association(s) and defect condensation in olivine can relate experimental data for measured diffusivities to discerning natural conditions where condensed-defect, fast-path diffusion in olivine could be significant. Planar extended defects can potentially play a role in the kinetics of deformation of olivine in the mantle, particularly as the condensation reaction lowers the activity of mobile point defects. Cherniak, Am. Mineral. 95 (2010) 362-368. Hart, Acta Met. 5 (1957) 597. Hermann et al., Contrib. Mineral. Petrol. 153 (2007) 417-428. Portnyagin et al., Earth Planet. Sci.Lett. 272 (2008) 541-552. Risold et al., Contrib. Mineral. Petrol. 142 (2001) 619-628. Spandler and O'Neill, Contrib. Mineral. Petrol. 159 (2010) 791-818.

A wheelchair with lever propulsion control for climbing up and down stairs.

PubMed

Sasaki, Kai; Eguchi, Yosuke; Suzuki, Kenji

2016-08-01

This study proposes a novel stair-climbing wheelchair based on lever propulsion control using the human upper body. Wheelchairs are widely used as supporting locomotion devices for people with acquired lower limb disabilities. However, steps and stairs are critical obstacles to locomotion, which restrict their activities when using wheelchairs. Previous research focused on power-assisted, stair-climbing wheelchairs, which were large and heavy due to its large actuators and mechanisms. In the previous research, we proposed a wheelchair with lever propulsion mechanism and presented its feasibility of climbing up the stairs. The developed stair-climbing wheelchair consists of manual wheels with casters for planar locomotion and a rotary-leg mechanism based on lever propulsion that is capable of climbing up stairs. The wheelchair also has a passive mechanism powered by gas springs for posture transition to shift the user's center of gravity between the desired positions for planar locomotion and stair-climbing. In this paper, we present an advanced study on both climbing up and going down using lever propulsion control by the user's upper body motion. For climbing down the stairs, we reassembled one-way clutches used for the rotary-leg mechanism to help a user climb down the stairs through lever operation. We also equipped the wheelchair with sufficient torque dampers. The frontal wheels were fixed while climbing down the stairs to ensure safety. Relevant experiments were then performed to investigate its performance and verify that the wheelchair users can operate the proposed lever propulsion mechanism.

Multi-planar bending properties of lumbar intervertebral joints following cyclic bending.

PubMed

Chow, Daniel H K; Luk, Keith D K; Holmes, Andrew D; Li, Xing-Fei; Tam, Steven C W

2004-02-01

To assess the changes in the multi-planar bending properties of intervertebral joints following cyclic bending along different directions. An in vitro biomechanical study using porcine lumbar motion segments. Repeated bending has been suggested as part of the etiology of gradual prolapse of the intervertebral disc, but the multi-planar changes in bending properties following cyclic loading have not been examined in detail. Porcine lumbar motion segments were subject to 1500 cycles of bending along directions of 0 degrees (flexion), 30 degrees, 60 degrees, or 90 degrees (right lateral bending). The multi-planar bending moments and hysteresis energies were recorded before loading and after various cycle numbers. Repeated bending at 30 degrees and 60 degrees resulted in greater decreases in mean bending moment and hysteresis energy than bending at 0 degrees or 90 degrees. No significant differences were seen between loading groups for the change in bending moment along the anterior testing directions, but significant differences were observed in the posterior and lateral testing directions, with bending at 30 degrees causing a significantly greater decrease in bending moment in the postero-lateral directions. The change in mechanical properties of porcine intervertebral joints due to cyclic bending depend on the direction of loading and the direction in which the properties are measured. Loading at 30 degrees provokes the most marked changes in bending moment and hysteresis energy.

Retentivity, selectivity and thermodynamic behavior of polycyclic aromatic hydrocarbons on charge-transfer and hypercrosslinked stationary phases under conditions of normal phase high performance liquid chromatography.

PubMed

Jiang, Ping; Lucy, Charles A

2016-03-11

Charge-transfer and hypercrosslinked polystyrene phases offer retention and separation for polycyclic aromatic hydrocarbons (PAHs) and thus have potential for petroleum analysis. The size, shape and planarity selectivity for PAH standards on charge-transfer (DNAP column) and hypercrosslinked polystyrene (HC-Tol and 5HGN columns) phases are different under normal phase liquid chromatography (NPLC). The HC-Tol column behaves like a conventional NPLC column with low retention of PAHs. Retention of PAHs on the DNAP and 5HGN are strong and increases with the number of aromatic rings. The main retention mechanism is through π-π interactions and dipole-induced dipole interaction. Thermodynamics indicates that the retention mechanism of PAHs remains unchanged over the temperature range 20-60°C. In addition, on either DNAP or 5HGN column, both linear and bent PAHs are retained through the same mechanism. But DNAP possesses smaller π-π interaction and higher planarity selectivity than 5HGN for PAHs. This is suggestive that DNAP interacts with PAHs through a disordered phase arrangement, while 5HGN behaves as an ordered adsorption phase. Copyright © 2016 Elsevier B.V. All rights reserved.

Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

NASA Technical Reports Server (NTRS)

Sali, Robert; Harsanyi, Gabor

1995-01-01

A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

[DNA complexes, formed on aqueous phase surfaces: new planar polymeric and composite nanostructures].

PubMed

Antipina, M N; Gaĭnutdinov, R V; Rakhnianskaia, A A; Sergeev-Cherenkov, A N; Tolstikhina, A L; Iurova, T V; Kislov, V V; Khomutov, G B

2003-01-01

The formation of DNA complexes with Langmuir monolayers of the cationic lipid octadecylamine (ODA) and the new amphiphilic polycation poly-4-vinylpyridine with 16% of cetylpyridinium groups (PVP-16) on the surface of an aqueous solution of native DNA of low ionic strength was studied. Topographic images of Langmuir-Blodgett films of DNA/ODA and DNA/PVP-16 complexes applied to micaceous substrates were investigated by the method of atomic force microscopy. It was found that films of the amphiphilic polycation have an ordered planar polycrystalline structure. The morphology of planar DNA complexes with the amphiphilic cation substantially depended on the incubation time and the phase state of the monolayer on the surface of the aqueous DNA solution. Complex structures and individual DNA molecules were observed on the surface of the amphiphilic monolayer. Along with quasi-linear individual bound DNA molecules, characteristic extended net-like structures and quasi-circular toroidal condensed conformations of planar DNA complexes were detected. Mono- and multilayer films of DNA/PVP-16 complexes were used as templates and nanoreactors for the synthesis of inorganic nanostructures via the binding of metal cations from the solution and subsequent generation of the inorganic phase. As a result, ultrathin polymeric composite films with integrated DNA building blocks and quasi-linear arrays of inorganic semiconductor (CdS) and iron oxide nanoparticles and nanowires were obtained. The nanostructures obtained were characterized by scanning probe microscopy and transmission electron microscopy techniques. The methods developed are promising for investigating the mechanisms of structural organization and transformation in DNA and polyelectrolyte complexes at the gas-liquid interface and for the design of new extremely thin highly ordered planar polymeric and composite materials, films, and coatings with controlled ultrastructure for applications in nanoelectronics and nanobiotechnology.

Sequential development of apical-basal and planar polarities in aggregating epitheliomuscular cells of Hydra.

PubMed

Seybold, Anna; Salvenmoser, Willi; Hobmayer, Bert

2016-04-01

Apical-basal and planar cell polarities are hallmarks of metazoan epithelia required to separate internal and external environments and to regulate trans- and intracellular transport, cytoskeletal organization, and morphogenesis. Mechanisms of cell polarization have been intensively studied in bilaterian model organisms, particularly in early embryos and cultured cells, while cell polarity in pre-bilaterian tissues is poorly understood. Here, we have studied apical-basal and planar polarization in regenerating (aggregating) clusters of epitheliomuscular cells of Hydra, a simple representative of the ancestral, pre-bilaterian phylum Cnidaria. Immediately after dissociation, single epitheliomuscular cells do not exhibit cellular polarity, but they polarize de novo during aggregation. Reestablishment of the Hydra-specific epithelial bilayer is a result of short-range cell sorting. In the early phase of aggregation, apical-basal polarization starts with an enlargement of the epithelial apical-basal diameter and by the development of belt-like apical septate junctions. Specification of the basal pole of epithelial cells occurs shortly later and is linked to synthesis of mesoglea, development of hemidesmosome-like junctions, and formation of desmosome-like junctions connecting the basal myonemes of neighbouring cells. Planar polarization starts, while apical-basal polarization is already ongoing. It is executed gradually starting with cell-autonomous formation, parallelization, and condensation of myonemes at the basal end of each epithelial cell and continuing with a final planar alignment of epitheliomuscular cells at the tissue level. Our findings reveal that epithelial polarization in Hydra aggregates occurs in defined steps well accessible by histological and ultrastructural techniques and they will provide a basis for future molecular studies. Copyright © 2016 Elsevier Inc. All rights reserved.

Altered thyroid status in lake trout (Salvelinus namaycush) exposed to co-planar 3,3',4,4',5-pentachlorobiphenyl.

PubMed

Brown, Scott B; Evans, Robert E; Vandenbyllardt, Lenore; Finnson, Ken W; Palace, Vince P; Kane, Andrew S; Yarechewski, Alvin Y; Muir, Derek C G

2004-03-30

Recent studies indicate that co-planar 3,3',4,4',5-pentachlorobiphenyl (PCB) congeners or their metabolites may disrupt thyroid function in fishes. Although co-planar PCB have been detected at microgram per kilogram levels in fish from contaminated areas, few studies have examined mechanisms whereby, co-planar PCBs may alter thyroid function in fish. We treated immature lake trout by intraperitoneal (i.p.)-injection or dietary gavage with vehicle containing 0, 0.7, 1.2, 25 or 40 microg 3,3',4,4',5-pentachlorobiphenyl (PCB 126) per kgBW. Blood and tissue samples were collected at various times up to 61 weeks following exposure. The treatments produced sustained dose-dependent elevations of tissue (PCB 126) concentrations. Thyroid epithelial cell height (TECH), plasma thyroxine (T4) and 3,3',5-triiodo-l-thyronine (T3) concentrations, hepatic 5'-monodeiodinase, hepatic glucuronidation of T4 and T3, as well as plasma T4 kinetics and fish growth were analyzed. Exposure to the highest doses of PCB 126 caused increased TECH, plasma T4 dynamics and T4-glucuronidation (T4-G). PCB 126 did not affect 5'-monodeiodinase and T3-glucuronidation (T3-G) and there were no effects on fish growth or condition. Because T3 status and growth were unaffected, the thyroid system was able to compensate for the alterations caused by the PCB 126 exposure. It is clear that concentrations of co-planar PCBs similar to those found in predatory fish from contaminated areas in the Great Lakes are capable of enhancing metabolism of T4. These changes may be of significance when T4 requirements are high for other reasons (e.g. periods of rapid growth, warm temperatures, metamorphosis, and parr-smolt transformation).

A short review of nanographenes: structures, properties and applications

NASA Astrophysics Data System (ADS)

Dai, Yafei; Liu, Yi; Ding, Kai; Yang, Jinlong

2018-04-01

Graphene has attracted great interest in the science and technology since it was exfoliated mechanically from the graphite in 2004. Although graphene has various potential applications, its practical applications are constrained enormously by its serious drawbacks, such as zero band gap, tendency of aggregation between layers and hydrophobicity, which mainly caused by the infinite planar hexagonal structure of graphene. Considering that the structural defects in the honeycomb lattice and the edges of graphene break the infinite structure and thus change the properties, which may improve the application efficiency, nanographene (NG) is proposed and attracts extensive attention. In this work, we review the structures of multifarious well-defined NGs synthesised in recent experiments. The effects of the shape, size, edges and substituents of NGs to the properties are discussed in detail and the regulation for various properties of NG is analysed. For the well-defined NGs, including planar and non-planar ones, the challenges and perspectives of their potential applications in nonlinear optical material, gas molecular detector and gas separation material, hydrogen storage material, and hole-transporting material in perovskite solar cells are envisioned.

The impact of solar cell technology on planar solar array performance

NASA Technical Reports Server (NTRS)

Mills, Michael W.; Kurland, Richard M.

1989-01-01

The results of a study into the potential impact of advanced solar cell technologies on the characteristics (weight, cost, area) of typical planar solar arrays designed for low, medium and geosynchronous altitude earth orbits are discussed. The study considered planar solar array substrate designs of lightweight, rigid-panel graphite epoxy and ultra-lightweight Kapton. The study proposed to answer the following questions: Do improved cell characteristics translate into array-level weight, size and cost improvements; What is the relative importance of cell efficiency, weight and cost with respect to array-level performance; How does mission orbital environment affect array-level performance. Comparisons were made at the array level including all mechanisms, hinges, booms, and harnesses. Array designs were sized to provide 5kW of array power (not spacecraft bus power, which is system dependent but can be scaled from given values). The study used important grass roots issues such as use of the GaAs radiation damage coefficients as determined by Anspaugh. Detailed costing was prepared, including cell and cover costs, and manufacturing attrition rates for the various cell types.

All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes

PubMed Central

Al-Dirini, Feras; Hossain, Faruque M.; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

2014-01-01

Graphene normally behaves as a semimetal because it lacks a bandgap, but when it is patterned into nanoribbons a bandgap can be introduced. By varying the width of these nanoribbons this band gap can be tuned from semiconducting to metallic. This property allows metallic and semiconducting regions within a single Graphene monolayer, which can be used in realising two-dimensional (2D) planar Metal-Insulator-Semiconductor field effect devices. Based on this concept, we present a new class of nano-scale planar devices named Graphene Self-Switching MISFEDs (Metal-Insulator-Semiconductor Field-Effect Diodes), in which Graphene is used as the metal and the semiconductor concurrently. The presented devices exhibit excellent current-voltage characteristics while occupying an ultra-small area with sub-10 nm dimensions and an ultimate thinness of a single atom. Quantum mechanical simulation results, based on the Extended Huckel method and Nonequilibrium Green's Function Formalism, show that a Graphene Self-Switching MISFED with a channel as short as 5 nm can achieve forward-to-reverse current rectification ratios exceeding 5000. PMID:24496307

Structural synthesis of linkages for quadruped bio-robot legs

NASA Astrophysics Data System (ADS)

Antonescu, O.; Robu, C.; Antonescu, P.

2016-08-01

The paper presents a few kinematic schemes of planar mechanisms with bars (linkages) used as part of the quadruped robot legs. The Dunshee linkage having only four elements as crank-rocker mechanism is analyzed. Further, the Klann linkage, which is accomplished by amplifying the crank-rocker mechanism with a dyadic kinematic chain, is also presented. More than that, the Jansen linkage, which is obtained by extending and amplifying the crank-rocker mechanism with two dyadic kinematic chains, is also analyzed. At the end of the paper, the authors present a novel linkage application consisting of a quadric kinematic chain.

Model-Based Spectrum Management. Part 1: Modeling and Computation Manual, Version 2.0

DTIC Science & Technology

2013-12-01

Occurrence of Occlusion by the Earth’s Surface C- 4 Figure C-6. Scenario for Evaluating the Significance of Angle Discrepancy in Using Planar...their transmit power at those locations. Many developers of DSA systems seek more aggressive sharing that favors behaviors allowing compatible reuse...provide behavioral guidance that allows finer coexistence mechanisms, e.g., mechanisms based on sensing and timing in addition to location as means to

Modeling the mechanical properties of DNA nanostructures.

PubMed

Arbona, Jean Michel; Aimé, Jean-Pierre; Elezgaray, Juan

2012-11-01

We discuss generalizations of a previously published coarse-grained description [Mergell et al., Phys. Rev. E 68, 021911 (2003)] of double stranded DNA (dsDNA). The model is defined at the base-pair level and includes the electrostatic repulsion between neighbor helices. We show that the model reproduces mechanical and elastic properties of several DNA nanostructures (DNA origamis). We also show that electrostatic interactions are necessary to reproduce atomic force microscopy measurements on planar DNA origamis.

The effect of aluminum alloying on strength properties and deformation mechanisms of the <123> Hadfield steel single crystals

NASA Astrophysics Data System (ADS)

Astafurova, E. G.; Tukeev, M. S.; Chumlyakov, Yu. I.

2007-10-01

The role of aluminum alloying on strength properties and deformation mechanisms (slip, twinning) of <123> single crystals of Hadfield steel under tensile loading at T = 300 K is demonstrated. It is found out that aluminum alloying suppresses twinning deformation in the <123> single crystals and, during slip, results in a dislocation structure change from a uniform dislocation distribution to a planar dislocation structure.

Simulation of Tip-Sample Interaction in the Atomic Force Microscope

NASA Technical Reports Server (NTRS)

Good, Brian S.; Banerjea, Amitava

1994-01-01

Recent simulations of the interaction between planar surfaces and model Atomic Force Microscope (AFM) tips have suggested that there are conditions under which the tip may become unstable and 'avalanche' toward the sample surface. Here we investigate via computer simulation the stability of a variety of model AFM tip configurations with respect to the avalanche transition for a number of fcc metals. We perform Monte-Carlo simulations at room temperature using the Equivalent Crystal Theory (ECT) of Smith and Banerjea. Results are compared with recent experimental results as well as with our earlier work on the avalanche of parallel planar surfaces. Our results on a model single-atom tip are in excellent agreement with recent experiments on tunneling through mechanically-controlled break junctions.

Modeling and simulation of dynamics of a planar-motion rigid body with friction and surface contact

NASA Astrophysics Data System (ADS)

Wang, Xiaojun; Lv, Jing

2017-07-01

The modeling and numerical method for the dynamics of a planar-motion rigid body with frictional contact between plane surfaces were presented based on the theory of contact mechanics and the algorithm of linear complementarity problem (LCP). The Coulomb’s dry friction model is adopted as the friction law, and the normal contact forces are expressed as functions of the local deformations and their speeds in contact bodies. The dynamic equations of the rigid body are obtained by the Lagrange equation. The transition problem of stick-slip motions between contact surfaces is formulated and solved as LCP through establishing the complementary conditions of the friction law. Finally, a numerical example is presented as an example to show the application.

THE VERTICAL PLANAR MOTION MECHANISM; A DYNAMIC TEST APPARATUS FOR EVALUATING CURRENT METERS AND OTHER MARINE INSTRUMENTATION

EPA Science Inventory

The overall objective was to provide a dynamic test apparatus that can produce known, controlled high frequency dynamics for the evaluation of current meters and other marine instrumentation. Of primary interest is the establishment of flow sensor measurement capabilities, and he...

Issues of planning trajectory of parallel robots taking into account zones of singularity

NASA Astrophysics Data System (ADS)

Rybak, L. A.; Khalapyan, S. Y.; Gaponenko, E. V.

2018-03-01

A method for determining the design characteristics of a parallel robot necessary to provide specified parameters of its working space that satisfy the controllability requirement is developed. The experimental verification of the proposed method was carried out using an approximate planar 3-RPR mechanism.

Maximum a posteriori Bayesian estimation of mycophenolic Acid area under the concentration-time curve: is this clinically useful for dosage prediction yet?

PubMed

Staatz, Christine E; Tett, Susan E

2011-12-01

This review seeks to summarize the available data about Bayesian estimation of area under the plasma concentration-time curve (AUC) and dosage prediction for mycophenolic acid (MPA) and evaluate whether sufficient evidence is available for routine use of Bayesian dosage prediction in clinical practice. A literature search identified 14 studies that assessed the predictive performance of maximum a posteriori Bayesian estimation of MPA AUC and one report that retrospectively evaluated how closely dosage recommendations based on Bayesian forecasting achieved targeted MPA exposure. Studies to date have mostly been undertaken in renal transplant recipients, with limited investigation in patients treated with MPA for autoimmune disease or haematopoietic stem cell transplantation. All of these studies have involved use of the mycophenolate mofetil (MMF) formulation of MPA, rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation. Bias associated with estimation of MPA AUC using Bayesian forecasting was generally less than 10%. However some difficulties with imprecision was evident, with values ranging from 4% to 34% (based on estimation involving two or more concentration measurements). Evaluation of whether MPA dosing decisions based on Bayesian forecasting (by the free website service https://pharmaco.chu-limoges.fr) achieved target drug exposure has only been undertaken once. When MMF dosage recommendations were applied by clinicians, a higher proportion (72-80%) of subsequent estimated MPA AUC values were within the 30-60 mg · h/L target range, compared with when dosage recommendations were not followed (only 39-57% within target range). Such findings provide evidence that Bayesian dosage prediction is clinically useful for achieving target MPA AUC. This study, however, was retrospective and focussed only on adult renal transplant recipients. Furthermore, in this study, Bayesian-generated AUC estimations and dosage predictions were not compared with a later full measured AUC but rather with a further AUC estimate based on a second Bayesian analysis. This study also provided some evidence that a useful monitoring schedule for MPA AUC following adult renal transplant would be every 2 weeks during the first month post-transplant, every 1-3 months between months 1 and 12, and each year thereafter. It will be interesting to see further validations in different patient groups using the free website service. In summary, the predictive performance of Bayesian estimation of MPA, comparing estimated with measured AUC values, has been reported in several studies. However, the next step of predicting dosages based on these Bayesian-estimated AUCs, and prospectively determining how closely these predicted dosages give drug exposure matching targeted AUCs, remains largely unaddressed. Further prospective studies are required, particularly in non-renal transplant patients and with the EC-MPS formulation. Other important questions remain to be answered, such as: do Bayesian forecasting methods devised to date use the best population pharmacokinetic models or most accurate algorithms; are the methods simple to use for routine clinical practice; do the algorithms actually improve dosage estimations beyond empirical recommendations in all groups that receive MPA therapy; and, importantly, do the dosage predictions, when followed, improve patient health outcomes?

Atomistic Simulation of the Rate-Dependent Ductile-to-Brittle Failure Transition in Bicrystalline Metal Nanowires.

PubMed

Tao, Weiwei; Cao, Penghui; Park, Harold S

2018-02-14

The mechanical properties and plastic deformation mechanisms of metal nanowires have been studied intensely for many years. One of the important yet unresolved challenges in this field is to bridge the gap in properties and deformation mechanisms reported for slow strain rate experiments (∼10 -2 s -1 ), and high strain rate molecular dynamics (MD) simulations (∼10 8 s -1 ) such that a complete understanding of strain rate effects on mechanical deformation and plasticity can be obtained. In this work, we use long time scale atomistic modeling based on potential energy surface exploration to elucidate the atomistic mechanisms governing a strain-rate-dependent incipient plasticity and yielding transition for face centered cubic (FCC) copper and silver nanowires. The transition occurs for both metals with both pristine and rough surfaces for all computationally accessible diameters (<10 nm). We find that the yield transition is induced by a transition in the incipient plastic event from Shockley partials nucleated on primary slip systems at MD strain rates to the nucleation of planar defects on non-Schmid slip planes at experimental strain rates, where multiple twin boundaries and planar stacking faults appear in copper and silver, respectively. Finally, we demonstrate that, at experimental strain rates, a ductile-to-brittle transition in failure mode similar to previous experimental studies on bicrystalline silver nanowires is observed, which is driven by differences in dislocation activity and grain boundary mobility as compared to the high strain rate case.

Evaluation of dual γ-ray imager with active collimator using various types of scintillators.

PubMed

Lee, Wonho; Lee, Taewoong; Jeong, Manhee; Kim, Ho Kyung

2011-10-01

The performance of a specialized dual γ-ray imager using both mechanical and electronic collimation was evaluated by Monte Carlo simulation (MCNP5). The dual imager consisted of an active collimator and a planar detector that were made from scintillators. The active collimator served not only as a coded aperture for mechanical collimation but also as a first detector for electronic collimation. Therefore, a single system contained both mechanical and electronic collimation. Various types of scintillators were tested and compared with each other in terms of their angular resolution, efficiency, and background noise. In general, a BGO active collimator had the best mechanical collimation performance, and an LaCl₃(Ce) active collimator provided the best electronic collimation performance. However, for low radiation energies, the mechanical collimation images made from both scintillators showed the same quality, and, for high radiation energies, electronic collimation images made from both scintillators also show similar quality. Therefore, if mechanical collimation is used to detect low-energy radiation and electronic collimation is applied to reconstruct a high-energy source, either LaCl₃(Ce) or BGO would be appropriate for the active collimator of a dual γ-ray imager. These results broaden the choice of scintillators for the active collimator of the dual γ-ray imager, which makes it possible to consider other factors, such as machinability and cost, in making the imager. As a planar detector, BGO showed better performance than other scintillators since its radiation detection efficiency was highest of all. Copyright © 2011 Elsevier Ltd. All rights reserved.

Selected AB4 2−/− (A = C, Si, Ge; B = Al, Ga, In) ions: a battle between covalency and aromaticity, and prediction of square planar Si in SiIn4 2−/−†

PubMed Central

Alexandrova, Anastassia N.; Nayhouse, Michael J.; Huynh, Mioy T.; Kuo, Jonathan L.; Melkonian, Arek V.; Chavez, Gerardo; Hernando, Nina M.; Kowal, Matthew D.; Liu, Chi-Ping

2012-01-01

CAl4 2−/− (D4h, 1A1g) is a cluster ion that has been established to be planar, aromatic, and contain a tetracoordinate planar C atom. Valence isoelectronic substitution of C with Si and Ge in this cluster leads to a radical change of structure toward distorted pentagonal species. We find that this structural change goes together with the cluster acquiring partial covalency of bonding between Si/Ge and Al4, facilitated by hybridization of the atomic orbitals (AOs). Counter intuitively, for the AAl4 2−/− (A = C, Si, Ge) clusters, hybridization in the dopant atom is strengthened from C, to Si, and to Ge, even though typically AOs are more likely to hybridize if they are closer in energy (i.e. in earlier elements in the Periodic Table). The trend is explained by the better overlap of the hybrids of the heavier dopants with the orbitals of Al4. From the thus understood trend, it is inferred that covalency in such clusters can be switched off, by varying the relative sizes of the AOs of the main element and the dopant. Using this mechanism, we then successfully killed covalency in Si, and predicted a new aromatic cluster ion containing a tetracoordinate square planar Si, SiIn4 2−/−. PMID:22868353

Design and Characterization of Next-Generation Micromirrors Fabricated in a Four-Level, Planarized Surface-Micromachined Polycrystalline Silicon Process

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

Michalicek, M.A.; Comtois, J.H.; Barron, C.C.

This paper describes the design and characterization of several types of micromirror devices to include process capabilities, device modeling, and test data resulting in deflection versus applied potential curves. These micromirror devices are the first to be fabricated in the state-of-the-art four-level planarized polysilicon process available at Sandia National Laboratories known as the Sandia Ultra-planar Multi-level MEMS Technology (SUMMiT). This enabling process permits the development of micromirror devices with near-ideal characteristics which have previously been unrealizable in standard three-layer polysilicon processes. This paper describes such characteristics as elevated address electrodes, individual address wiring beneath the device, planarized mirror surfaces usingmore » Chemical Mechanical Polishing (CMP), unique post-process metallization, and the best active surface area to date. This paper presents the design, fabrication, modeling, and characterization of several variations of Flexure-Beam (FBMD) and Axial-Rotation Micromirror Devices (ARMD). The released devices are first metallized using a standard sputtering technique relying on metallization guards and masks that are fabricated next to the devices. Such guards are shown to enable the sharing of bond pads between numerous arrays of micromirrors in order to maximize the number of on-chip test arrays. The devices are modeled and then empirically characterized using a laser interferometer setup located at the Air Force Institute of Technology (AFIT) at Wright-Patterson AFB in Dayton, Ohio. Unique design considerations for these devices and the process are also discussed.« less

Gate Tunable Transport in Graphene/MoS₂/(Cr/Au) Vertical Field-Effect Transistors.

PubMed

Nazir, Ghazanfar; Khan, Muhammad Farooq; Aftab, Sikandar; Afzal, Amir Muhammad; Dastgeer, Ghulam; Rehman, Malik Abdul; Seo, Yongho; Eom, Jonghwa

2017-12-28

Two-dimensional materials based vertical field-effect transistors have been widely studied due to their useful applications in industry. In the present study, we fabricate graphene/MoS₂/(Cr/Au) vertical transistor based on the mechanical exfoliation and dry transfer method. Since the bottom electrode was made of monolayer graphene (Gr), the electrical transport in our Gr/MoS₂/(Cr/Au) vertical transistors can be significantly modified by using back-gate voltage. Schottky barrier height at the interface between Gr and MoS₂ can be modified by back-gate voltage and the current bias. Vertical resistance (R vert ) of a Gr/MoS₂/(Cr/Au) transistor is compared with planar resistance (R planar ) of a conventional lateral MoS₂ field-effect transistor. We have also studied electrical properties for various thicknesses of MoS₂ channels in both vertical and lateral transistors. As the thickness of MoS₂ increases, R vert increases, but R planar decreases. The increase of R vert in the thicker MoS₂ film is attributed to the interlayer resistance in the vertical direction. However, R planar shows a lower value for a thicker MoS₂ film because of an excess of charge carriers available in upper layers connected directly to source/drain contacts that limits the conduction through layers closed to source/drain electrodes. Hence, interlayer resistance associated with these layers contributes to planer resistance in contrast to vertical devices in which all layers contribute interlayer resistance.

Dynamic Neuromuscular Control of the Lower Limbs in Response to Unexpected Single-Planar versus Multi-Planar Support Perturbations in Young, Active Adults.

PubMed

Malfait, Bart; Staes, Filip; de Vries, Aijse; Smeets, Annemie; Hawken, Malcolm; Robinson, Mark A; Vanrenterghem, Jos; Verschueren, Sabine

2015-01-01

An anterior cruciate ligament (ACL) injury involves a multi-planar injury mechanism. Nevertheless, unexpected multi-planar perturbations have not been used to screen athletes in the context of ACL injury prevention yet could reveal those more at risk. The objective of this study was to compare neuromuscular responses to multi-planar (MPP) and single-planar perturbations (SPP) during a stepping-down task. These results might serve as a basis for future implementation of external perturbations in ACL injury screening programs. Thirteen young adults performed a single leg stepping-down task in eight conditions (four MPP and four SPP with a specified amplitude and velocity). The amplitudes of vastus lateralis (VL), vastus medialis (VM), hamstrings lateralis (HL), hamstrings medialis (HM) EMG activity, medio-lateral and anterior-posterior centre of mass (COM) displacements, the peak knee flexion and abduction angles were compared between conditions using an one-way ANOVA. Number of stepping responses were monitored during all conditions. Significantly greater muscle activity levels were found in response to the more challenging MPP and SPP compared to the less challenging conditions (p < 0.05). No differences in neuromuscular activity were found between the MPP conditions and their equivalents in the SPP. Eighteen stepping responses were monitored in the SPP versus nine in the MPP indicating that the overall neuromuscular control was even more challenged during the SPP which was supported by greater COM displacements in the SPP. The more intense MPP and SPP evoked different neuromuscular responses resulting in greater muscle activity levels compared to small perturbations. Based on the results of COM displacements and based on the amount of stepping responses, dynamic neuromuscular control of the knee joint appeared less challenged during the MPP. Therefore, future work should investigate extensively if other neuromuscular differences (i.e. co-activation patterns and kinetics) exist between MPP and SPP. In addition, future work should examine the influence on the neuromuscular control of the magnitude of the perturbations and the magnitude of stepping height and stepping distance.

Genetic analysis of ectopic growth suppression during planar growth of integuments mediated by the Arabidopsis AGC protein kinase UNICORN

PubMed Central

2013-01-01

Background The coordination of growth within a tissue layer is of critical importance for tissue morphogenesis. For example, cells within the epidermis undergo stereotypic cell divisions that are oriented along the plane of the layer (planar growth), thereby propagating the layered epidermal structure. Little is known about the developmental control that regulates such planar growth in plants. Recent evidence suggested that the Arabidopsis AGC VIII protein kinase UNICORN (UCN) maintains planar growth by suppressing the formation of ectopic multicellular protrusions in several floral tissues including integuments. In the current model UCN controls this process during integument development by directly interacting with the ABERRANT TESTA SHAPE (ATS) protein, a member of the KANADI (KAN) family of transcription factors, thereby repressing its activity. Here we report on the further characterization of the UCN mechanism. Results Phenotypic analysis of flowers of ucn-1 plants impaired in floral homeotic gene activity revealed that any of the four floral whorls could produce organs carrying ucn-1 protrusions. The ectopic outgrowths of ucn integuments did not accumulate detectable signals of the auxin and cytokinin reporters DR5rev::GFP and ARR5::GUS, respectively. Furthermore, wild-type and ucn-1 seedlings showed similarly strong callus formation upon in vitro culture on callus-inducing medium. We also show that ovules of ucn-1 plants carrying the dominant ats allele sk21-D exhibited more pronounced protrusion formation. Finally ovules of ucn-1 ett-1 double mutants and ucn-1 ett-1 arf4-1 triple mutants displayed an additive phenotype. Conclusions These data deepen the molecular insight into the UCN-mediated control of planar growth during integument development. The presented evidence indicates that UCN downstream signaling does not involve the control of auxin or cytokinin homeostasis. The results also reveal that UCN interacts with ATS independently of an ATS/ETT complex required for integument initiation and they further emphasize the necessity to balance UCN and ATS proteins during maintenance of planar growth in integuments. PMID:23281875

Estimating Fuel Bed Loadings in Masticated Areas

Treesearch

Sharon Hood; Ros Wu

2006-01-01

Masticated fuel treatments that chop small trees, shrubs, and dead woody material into smaller pieces to reduce fuel bed depth are used increasingly as a mechanical means to treat fuels. Fuel loading information is important to monitor changes in fuels. The commonly used planar intercept method however, may not correctly estimate fuel loadings because masticated fuels...

An X-Y Platform for Randsight-Type Instruments.

ERIC Educational Resources Information Center

Clewett, R. W.; And Others

A hand-operated mechanical device, called an X-Y Platform because of its ability to undergo orthogonal planar motions reminiscent of X and Y coordinates, permits design simplifications and lower costs when used with RANDSIGHT-type closed circuit television to enable the partially sighted to read and write. This paper presents a detailed discussion…

EUV efficiency of a 6000-grooves per mm diffraction grating

NASA Technical Reports Server (NTRS)

Hurwitz, Mark; Bowyer, Stuart; Edelstein, Jerry; Harada, Tatsuo; Kita, Toshiaki

1990-01-01

In order to explore whether grooves ruled mechanically at a density of 6000 per mm can perform well at EUV wavelengths, a sample grating is measured with this density in an EUV calibration facility. Measurements are presented of the planar uniform line-space diffraction grating's efficiency and large-angle scattering.

Efficient dynamic modeling of manipulators containing closed kinematic loops

NASA Astrophysics Data System (ADS)

Ferretti, Gianni; Rocco, Paolo

An approach to efficiently solve the forward dynamics problem for manipulators containing closed chains is proposed. The two main distinctive features of this approach are: the dynamics of the equivalent open loop tree structures (any closed loop can be in general modeled by imposing some additional kinematic constraints to a suitable tree structure) is computed through an efficient Newton Euler formulation; the constraint equations relative to the most commonly adopted closed chains in industrial manipulators are explicitly solved, thus, overcoming the redundancy of Lagrange's multipliers method while avoiding the inefficiency due to a numerical solution of the implicit constraint equations. The constraint equations considered for an explicit solution are those imposed by articulated gear mechanisms and planar closed chains (pantograph type structures). Articulated gear mechanisms are actually used in all industrial robots to transmit motion from actuators to links, while planar closed chains are usefully employed to increase the stiffness of the manipulators and their load capacity, as well to reduce the kinematic coupling of joint axes. The accuracy and the efficiency of the proposed approach are shown through a simulation test.

Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process

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

Jang, Sunjae; Kulkarni, Atul; Qin, Hongyi

In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution bymore » analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements.« less

Practical sliced configuration spaces for curved planar pairs

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

Sacks, E.

1999-01-01

In this article, the author presents a practical configuration-space computation algorithm for pairs of curved planar parts, based on the general algorithm developed by Bajaj and the author. The general algorithm advances the theoretical understanding of configuration-space computation, but is too slow and fragile for some applications. The new algorithm solves these problems by restricting the analysis to parts bounded by line segments and circular arcs, whereas the general algorithm handles rational parametric curves. The trade-off is worthwhile, because the restricted class handles most robotics and mechanical engineering applications. The algorithm reduces run time by a factor of 60 onmore » nine representative engineering pairs, and by a factor of 9 on two human-knee pairs. It also handles common special pairs by specialized methods. A survey of 2,500 mechanisms shows that these methods cover 90% of pairs and yield an additional factor of 10 reduction in average run time. The theme of this article is that application requirements, as well as intrinsic theoretical interest, should drive configuration-space research.« less

Electrical and mechanical anharmonicities from NIR-VCD spectra of compounds exhibiting axial and planar chirality: the cases of (S)-2,3-pentadiene and methyl-d(3) (R)- and (S)-[2.2]paracyclophane-4-carboxylate.

PubMed

Abbate, Sergio; Longhi, Giovanna; Gangemi, Fabrizio; Gangemi, Roberto; Superchi, Stefano; Caporusso, Anna Maria; Ruzziconi, Renzo

2011-10-01

The IR and Near infrared (NIR) vibrational circular dichroism (VCD) spectra of molecules endowed with noncentral chirality have been investigated. Data for fundamental, first, and second overtone regions of (S)-2,3-pentadiene, exhibiting axial chirality, and methyl-d(3) (R)- and (S)-[2.2]paracyclophane-4-carboxylate, exhibiting planar chirality have been measured and analyzed. The analysis of NIR and IR VCD spectra was based on the local-mode model and the use of density functional theory (DFT), providing mechanical and electrical anharmonic terms for all CH-bonds. The comparison of experimental and calculated spectra is satisfactory and allows one to monitor fine details in the asymmetric charge distribution in the molecules: these details consist in the harmonic frequencies, in the principal anharmonicity constants, in both the atomic polar and axial tensors and in their first and second derivatives with respect to the CH-stretching coordinates. Copyright © 2011 Wiley-Liss, Inc.

Microstructural effects on the room and elevated temperature low cycle fatigue behavior of Waspaloy. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Lerch, B. A.

1982-01-01

Longitudinal specimens of Waspaloy containing either coarse grains with small gamma or fine grains with large gamma were tested in air at a frequency of 0.33 Hz or 0.50 Hz. The coarse grained structures exhibited planar slip on (III) planes and precipitate shearing at all temperatures. Cracks initiated by a Stage 1 mechanism and propagated by a striation forming mechanism. At 700 C and 800 C, cleavage and intergranular cracking were observed. Testing at 500 C, 700 C, and 800 C caused precipitation of grain boundary carbides. At 700 C, carbides precipitated on slip bands. The fine grained structures exhibited planar slip on (111) planes. Dislocations looped the large gamma precipitates. This structure led to stress saturation and propagation was observed. Increasing temperatures resulted in increased specimen oxidation for both heat treatments. Slip band and grain boundary oxidation were observed. At 800 C, oxidized grain boundaries were cracked by intersecting slip bands which resulted in intergranular failure. The fine specimens had crack initiation later in the fatigue life, but with more rapid propagation crack propagation.

A parameters optimization method for planar joint clearance model and its application for dynamics simulation of reciprocating compressor

NASA Astrophysics Data System (ADS)

Hai-yang, Zhao; Min-qiang, Xu; Jin-dong, Wang; Yong-bo, Li

2015-05-01

In order to improve the accuracy of dynamics response simulation for mechanism with joint clearance, a parameter optimization method for planar joint clearance contact force model was presented in this paper, and the optimized parameters were applied to the dynamics response simulation for mechanism with oversized joint clearance fault. By studying the effect of increased clearance on the parameters of joint clearance contact force model, the relation of model parameters between different clearances was concluded. Then the dynamic equation of a two-stage reciprocating compressor with four joint clearances was developed using Lagrange method, and a multi-body dynamic model built in ADAMS software was used to solve this equation. To obtain a simulated dynamic response much closer to that of experimental tests, the parameters of joint clearance model, instead of using the designed values, were optimized by genetic algorithms approach. Finally, the optimized parameters were applied to simulate the dynamics response of model with oversized joint clearance fault according to the concluded parameter relation. The dynamics response of experimental test verified the effectiveness of this application.

Effect of Vertical Concentration Gradient on Globally Planar Detonation with Detailed Reaction Mechanism

NASA Astrophysics Data System (ADS)

Song, Qingguana; Wang, Cheng; Han, Yong; Gao, Dayuan; Duan, Yingliang

2017-06-01

Since detonation often initiates and propagates in the non-homogeneous mixtures, investigating its behavior in non-uniform mixtures is significant not only for the industrial explosion in the leakage combustible gas, but also for the experimental investigations with a vertical concentration gradient caused by the difference in the molecular weight of gas mixture. Objective of this work is to show the detonation behavior in the mixture with different concentration gradients with detailed chemical reaction mechanism. A globally planar detonation in H2-O2 system is simulated by a high-resolution code based on the fifth-order weighted essentially non-oscillatory (WENO) scheme in spatial discretization and the third-order Additive Runge-Kutta schemes in time discretization. The different shocked combustion modes appear in the rich-fuel and poor-fuel layers due to the concentration gradient effect. Globally, for the cases with the lower gradient detonation can be sustained in a way of the alternation of the multi-heads mode and single-head mode, whereas for the cases with the higher gradient detonation propagates with a single-head mode. Institute of Chemical Materials, CAEP.

Anaerobic biodegradability and methanogenic toxicity of key constituents in copper chemical mechanical planarization effluents of the semiconductor industry.

PubMed

Hollingsworth, Jeremy; Sierra-Alvarez, Reyes; Zhou, Michael; Ogden, Kimberly L; Field, Jim A

2005-06-01

Copper chemical mechanical planarization (CMP) effluents can account for 30-40% of the water discharge in semiconductor manufacturing. CMP effluents contain high concentrations of soluble copper and a complex mixture of organic constituents. The aim of this study is to perform a preliminary assessment of the treatability of CMP effluents in anaerobic sulfidogenic bioreactors inoculated with anaerobic granular sludge by testing individual compounds expected in the CMP effluents. Of all the compounds tested (copper (II), benzotriazoles, polyethylene glycol (M(n) 300), polyethylene glycol (M(n) 860) monooleate, perfluoro-1-octane sulfonate, citric acid, oxalic acid and isopropanol) only copper was found to be inhibitory to methanogenic activity at the concentrations tested. Most of the organic compounds tested were biodegradable with the exception of perfluoro-1-octane sulfonate and benzotriazoles under sulfate reducing conditions and with the exception of the same compounds as well as Triton X-100 under methanogenic conditions. The susceptibility of key components in CMP effluents to anaerobic biodegradation combined with their low microbial inhibition suggest that CMP effluents should be amenable to biological treatment in sulfate reducing bioreactors.

Near field planar microwave probe sensor for nondestructive condition assessment of wood products

NASA Astrophysics Data System (ADS)

Tiwari, Nilesh Kumar; Singh, Surya Prakash; Akhtar, M. Jaleel

2018-06-01

In this work, the unified methodology based on the newly designed electrically small planar resonant microwave sensor to detect the subsurface defect in wood products is presented. The proposed planar sensor involves loading of the specially designed coupled microstrip line with a novel small resonating element at its end. The novel design topology of the proposed near field sensor substantially increases the overall resolution and sensitivity of the microwave scanning system due to the strong localization of the electric field in the electrically small sensing region. A detailed electromagnetic and quasi static analysis of the near field scanning mechanism is also described in this work, which helps to understand the physics involved in the proposed scanning mechanism. The prototype of the designed sensor is fabricated on a 0.8 mm Roger 5880 substrate, and accordingly, the scattering parameters of the sensor under both loaded and unloaded conditions are measured. The measured and simulated scattering parameters under the unloaded condition are compared to validate the fabricated sensor, and a closed match between the simulated and measured resonance frequencies is observed. The fabricated sensor is used here for two potential applications, viz., the dielectric sensing of various low permittivity contrast dielectric materials and subsurface imaging of wood products to trace concealed defects and moisture content under the thin paint layer. The proposed resonant sensor can potentially be used to develop the low profile, low cost, non-destructive, and non-invasive quality monitoring system for inspecting various types of wood products without peeling off the upper paint coating.

[Planar molecular arrangements aid the design of MHC class II binding peptides].

PubMed

Cortés, A; Coral, J; McLachlan, C; Benítez, R; Pinilla, L

2017-01-01

The coupling between peptides and MHC-II proteins in the human immune system is not well understood. This work presents an evidence-based hypothesis of a guiding intermolecular force present in every human MHC-II protein (HLA-II). Previously, we examined the spatial positions of the fully conserved residues in all HLA-II protein types. In each one, constant planar patterns were revealed. These molecular planes comprise of amino acid groups of the same chemical species (for example, Gly) distributed across the protein structure. Each amino acid plane has a unique direction and this directional element offers spatial selectivity. Constant within all planes, too, is the presence of an aromatic residue possessing electrons in movement, leading the authors to consider that the planes generate electromagnetic fields that could serve as an attractive force in a single direction. Selection and attraction between HLA-II molecules and antigen peptides would, therefore, be non-random, resulting in a coupling mechanism as effective and rapid as is clearly required in the immune response. On the basis of planar projections onto the HLA-II groove, modifications were made by substituting the key residues in the class II-associated invariant chain peptide-a peptide with a universal binding affinity-resulting in eight different modified peptides with affinities greater than that of the unmodified peptide. Accurate and reliable prediction of MHC class II-binding peptides may facilitate the design of universal vaccine-peptides with greatly enhanced binding affinities. The proposed mechanisms of selection, attraction and coupling between HLA-II and antigen peptides are explained further in the paper.

Solid-state membrane module

DOEpatents

Hinklin, Thomas Ray; Lewinsohn, Charles Arthur

2015-06-30

A module for separating oxygen from an oxygen-containing gaseous mixture comprising planar solid-state membrane units, each membrane unit comprising planar dense mixed conducting oxides layers, planar channel-free porous support layers, and one or more planar intermediate support layers comprising at least one channeled porous support layer. The porosity of the planar channeled porous support layers is less than the porosity of the planar channel-free porous support layers.

Exploration of the mechanisms of temperature-dependent grain boundary mobility: Search for the common origin of ultrafast grain boundary motion

DOE PAGES

O’Brien, C. J.; Foiles, S. M.

2016-04-19

The temperature dependence of grain boundary mobility is complex, varied, and rarely fits ideal Arrhenius behavior. This work presents a series of case studies of planar grain boundaries in a model FCC system that were previously demonstrated to exhibit a variety of temperature-dependent mobility behaviors. It is demonstrated that characterization of the mobility versus temperature plots is not sufficient to predict the atomic motion mechanism of the grain boundaries. Herein, the temperature-dependent motion and atomistic motion mechanisms of planar grain boundaries are driven by a synthetic, orientation-dependent, driving force. The systems studied include CSL boundaries with Σ values of 5,more » 7, and 15, including both symmetric and asymmetric boundaries. These boundaries represent a range of temperature-dependent trends including thermally activated, antithermal, and roughening behaviors. Examining the atomic-level motion mechanisms of the thermally activated boundaries reveals that each involves a complex shuffle, and at least one atom that changes the plane it resides on. The motion mechanism of the antithermal boundary is qualitatively different and involves an in-plane coordinated shuffle that rotates atoms about a fixed atom lying on a point in the coincident site lattice. Furthermore, this provides a mechanistic reason for the observed high mobility, even at low temperatures, which is due to the low activation energy needed for such motion. However, it will be demonstrated that this mechanism is not universal, or even common, to other boundaries exhibiting non-thermally activated motion. This work concludes that no single atomic motion mechanism is sufficient to explain the existence of non-thermally activated boundary motion.« less

A novel voice coil motor-driven compliant micropositioning stage based on flexure mechanism

NASA Astrophysics Data System (ADS)

Shang, Jiangkun; Tian, Yanling; Li, Zheng; Wang, Fujun; Cai, Kunhai

2015-09-01

This paper presents a 2-degrees of freedom flexure-based micropositioning stage with a flexible decoupling mechanism. The stage is composed of an upper planar stage and four vertical support links to improve the out-of-plane stiffness. The moving platform is driven by two voice coil motors, and thus it has the capability of large working stroke. The upper stage is connected with the base through six double parallel four-bar linkages mechanisms, which are orthogonally arranged to implement the motion decoupling in the x and y directions. The vertical support links with serially connected hook joints are utilized to guarantee good planar motion with heavy-loads. The static stiffness and the dynamic resonant frequencies are obtained based on the theoretical analyses. Finite element analysis is used to investigate the characteristics of the developed stage. Experiments are carried out to validate the established models and the performance of the developed stage. It is noted that the developed stage has the capability of translational motion stroke of 1.8 mm and 1.78 mm in working axes. The maximum coupling errors in the x and y directions are 0.65% and 0.82%, respectively, and the motion resolution is less than 200 nm. The experimental results show that the developed stage has good capability for trajectory tracking.

Linear complementarity formulation for 3D frictional sliding problems

USGS Publications Warehouse

Kaven, Joern; Hickman, Stephen H.; Davatzes, Nicholas C.; Mutlu, Ovunc

2012-01-01

Frictional sliding on quasi-statically deforming faults and fractures can be modeled efficiently using a linear complementarity formulation. We review the formulation in two dimensions and expand the formulation to three-dimensional problems including problems of orthotropic friction. This formulation accurately reproduces analytical solutions to static Coulomb friction sliding problems. The formulation accounts for opening displacements that can occur near regions of non-planarity even under large confining pressures. Such problems are difficult to solve owing to the coupling of relative displacements and tractions; thus, many geomechanical problems tend to neglect these effects. Simple test cases highlight the importance of including friction and allowing for opening when solving quasi-static fault mechanics models. These results also underscore the importance of considering the effects of non-planarity in modeling processes associated with crustal faulting.

The concerted trimerization of ethyne to benzene revisited

NASA Astrophysics Data System (ADS)

Cioslowski, Jerzy; Liu, Guanghua; Moncrieff, David

2000-01-01

CCSD(T)/6-311G ∗∗//QCISD/6-311G ∗∗ calculations on the concerted [2+2+2] trimerization of ethyne to benzene yield Δ Htrimo (HCCH)=-140.2 kcal/mol and Δ Hacto(HCCH)=53.1 kcal/mol. The corresponding transition state (TS) possesses C 2 symmetry, although both the planar D 3h and nonplanar D 3 structures are negligibly higher in energy, indicating extreme flatness of the potential energy hypersurface along the distortion paths. The analogous trimerizations of HCCCl and ClCCCl are predicted to be considerably more exothermic. As the respective TSs cannot be located and the planar pseudo-TSs that possess several imaginary vibrational frequencies are associated with high reaction barriers, the concerted mechanism can be ruled out for these reactions.

A Study of a Mechanical Swimming Dolphin

NASA Astrophysics Data System (ADS)

Fang, Lilly; Maass, Daniel; Leftwich, Megan; Smits, Alexander

2007-11-01

A one-third scale dolphin model was constructed to investigate dolphin swimming hydrodynamics. Design and construction of the model were achieved using body coordinate data from the common dolphin (Delphinus delphis) to ensure geometric similarity. The front two-thirds of the model are rigid and stationary, while an external mechanism drives the rear third. This motion mimics the kinematics of dolphin swimming. Planar laser induced florescence (PLIF) and particle image velocimetry (PIV) are used to study the hydrodynamics of the wake and to develop a vortex skeleton model.

Reynolds Number Effects on Thrust Coefficients and PIV for Flapping Wing Micro Air Vehicles

DTIC Science & Technology

2012-03-09

flapper and smallest gear attached to the drive shaft from the motor. Lastly, passive rotation stops were designed and printed using the Objet Eden 500V...for different flapping mechanisms are also compared to a rotating propeller with the goal of elucidating the design trade space between rotorcraft and...flapping wings at Reynolds numbers less than 100,000. One flapping-wing mechanism was designed to incorporate a coupled 4-bar planar and 4-bar

Bi-directional planar slide mechanism

DOEpatents

Bieg, Lothar F.

2003-11-04

A bi-directional slide mechanism. A pair of master and slave disks engages opposite sides of the platform. Rotational drivers are connected to master disks so the disks rotate eccentrically about their respective axes of rotation. Opposing slave disks are connected to master disks on opposite sides of the platform by a circuitous mechanical linkage, or are electronically synchronized together using stepper motors, to effect coordinated motion. The synchronized eccentric motion of the pairs of master/slave disks compels smooth linear motion of the platform forwards and backwards without backlash. The apparatus can be incorporated in a MEMS device.

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

Alexandrova, Anastassia N.; Nayhouse, Michael J.; Huynh, Mioy T.

CAl₄²-/- (D₄h, ¹A₁g) is is a cluster ion that has been established to be planar, aromatic, and contain a tetracoordinate planar C atom. Valence isoelectronic substitution of C with Si and Ge in this cluster leads to a radical change of structure toward distorted pentagonal species. We find that this structural change goes together with the cluster acquiring partial covalency of bonding between Si/Ge and Al₄, facilitated by hybridization of the atomic orbitals (AOs). Counter intuitively, for the AAl₄²-/- (A = C, Si, Ge) clusters, hybridization in the dopant atom is strengthened from C, to Si, and to Ge, evenmore » though typically AOs are more likely to hybridize if they are closer in energy (i.e. in earlier elements in the Periodic Table). The trend is explained by the better overlap of the hybrids of the heavier dopants with the orbitals of Al₄. From the thus understood trend, it is inferred that covalency in such clusters can be switched off, by varying the relative sizes of the AOs of the main element and the dopant. Using this mechanism, we then successfully killed covalency in Si, and predicted a new aromatic cluster ion containing a tetracoordinate square planar Si, SiIn₄²-/-.« less

Theoretical study of the impact of stress and interstitial oxygen on the behavior of intrinsic point defects in growing Czochralski Si crystals

NASA Astrophysics Data System (ADS)

Sueoka, K.; Nakamura, K.; Vanhellemont, J.

2017-09-01

For the development of crystal pulling processes for 450 mm-diameter defect-free Si crystals, it is important to evaluate the impact of thermal stress on intrinsic point defect behavior during crystal growth. In a crystal growing from a melt, the melt/solid interface can be considered as being stress-free. Due to that the thermal stress in the growing substrate near the interface is internal plane stress. Previously, we evaluated the impact of (001) planar-isotropic stress on the formation enthalpy (Hf) of the vacancy (V) and the self-interstitial (I) using density functional theory (DFT) calculations, and explained quantitatively the published experimental values of the so-called ;Voronkov criterion;. The thermal stress in a growing crystal is indeed planar but is not isotropic in the plane except for the central region of the crystal. The purpose of the present study is to estimate the impact of planar-anisotropic stress on the formation enthalpy Hf of V and I. It is found that the three stress dependencies of σx: σy=1: 1 (planar-isotropic), 2: 1, 5: 1 (planar-anisotropic) are close to each other, independent of the assumption of isotropic or anisotropic planar stress. This is the reason why the experimental results obtained over the whole radial direction of the crystal are well reproduced by the calculated results assuming planar-isotropic stress. A uniaxial stress dependence which is a good assumption for the crystal peripheral region, leads also to results that are close to those for the planar stress dependence. Also the mechanisms behind the experimentally observed impact of interstitial oxygen (Oi), introduced during Czochralski Si growth, on V and I concentrations are clarified. DFT calculations are performed to obtain the formation energies (Ef) of V and I at all sites within a sphere with 5 Å radius around the Oi atom. Formation (vibration) entropy (Sf) calculations for V and I are also performed. It is found that both EfV and SfV of V in the zigzag-bond (1st, 2nd, 5th) including the Oi atom decrease while EfI of I is not affected by the Oi atom. ;Total V; is defined as the sum of free V and V trapped by the Oi atoms. The total V concentration at the melting point is evaluated by considering the EfV and SfV at each site. The calculated V concentration increases by about 2.9% with 1×1018 Oi cm-3 and agrees well with the experimentally estimated value of a few % increase with 1×1018 Oi cm-3.

Frame-mounted wire management device

DOEpatents

Grushkowitz, Tyler; Fischer, Kevin; Danning, Matthew

2016-09-20

A wire management device is disclosed. The device comprises a clip comprising an upper planar member and a lower planar member, each planar member having an inner and outer surface, wherein the inner surface of the upper planar member includes a post extending toward the inner surface of the lower planar member, a stem extending from the outer surface of the lower planar member, the stem including two outwardly-extending flanges, each of the first and second outwardly-extending flanges including an edge portion extending toward the outer surface of the lower planar member, and a transverse passage extending along the outer surface of the lower planar member, the transverse passage extending across the stem, wherein the stem has a recessed portion along the transverse passage.

Kinematic synthesis of adjustable robotic mechanisms

NASA Astrophysics Data System (ADS)

Chuenchom, Thatchai

1993-01-01

Conventional hard automation, such as a linkage-based or a cam-driven system, provides high speed capability and repeatability but not the flexibility required in many industrial applications. The conventional mechanisms, that are typically single-degree-of-freedom systems, are being increasingly replaced by multi-degree-of-freedom multi-actuators driven by logic controllers. Although this new trend in sophistication provides greatly enhanced flexibility, there are many instances where the flexibility needs are exaggerated and the associated complexity is unnecessary. Traditional mechanism-based hard automation, on the other hand, neither can fulfill multi-task requirements nor are cost-effective mainly due to lack of methods and tools to design-in flexibility. This dissertation attempts to bridge this technological gap by developing Adjustable Robotic Mechanisms (ARM's) or 'programmable mechanisms' as a middle ground between high speed hard automation and expensive serial jointed-arm robots. This research introduces the concept of adjustable robotic mechanisms towards cost-effective manufacturing automation. A generalized analytical synthesis technique has been developed to support the computational design of ARM's that lays the theoretical foundation for synthesis of adjustable mechanisms. The synthesis method developed in this dissertation, called generalized adjustable dyad and triad synthesis, advances the well-known Burmester theory in kinematics to a new level. While this method provides planar solutions, a novel patented scheme is utilized for converting prescribed three-dimensional motion specifications into sets of planar projections. This provides an analytical and a computational tool for designing adjustable mechanisms that satisfy multiple sets of three-dimensional motion specifications. Several design issues were addressed, including adjustable parameter identification, branching defect, and mechanical errors. An efficient mathematical scheme for identification of adjustable member was also developed. The analytical synthesis techniques developed in this dissertation were successfully implemented in a graphic-intensive user-friendly computer program. A physical prototype of a general purpose adjustable robotic mechanism has been constructed to serve as a proof-of-concept model.

Single Degree-of-Freedom Exoskeleton Mechanism Design for Finger Rehabilitation

PubMed Central

Wolbrecht, Eric T.; Reinkensmeyer, David J.; Perez-Gracia, Alba

2014-01-01

This paper presents the kinematic design of a single degree-of-freedom exoskeleton mechanism: a planar eight-bar mechanism for finger curling. The mechanism is part of a finger-thumb robotic device for hand therapy that will allow users to practice key pinch grip and finger-thumb opposition, allowing discrete control inputs for playing notes on a musical gaming interface. This approach uses the mechanism to generate the desired grasping trajectory rather than actuating the joints of the fingers and thumb independently. In addition, the mechanism is confined to the back of the hand, so as to allow sensory input into the palm of the hand, minimal size and apparent inertia, and the possibility of placing multiple mechanisms side-by-side to allow control of individual fingers. PMID:22275628

Delivering both sum and difference beam distributions to a planar monopulse antenna array

DOEpatents

Strassner, II, Bernd H.

2015-12-22

A planar monopulse radar apparatus includes a planar distribution matrix coupled to a planar antenna array having a linear configuration of antenna elements. The planar distribution matrix is responsive to first and second pluralities of weights applied thereto for providing both sum and difference beam distributions across the antenna array.

Optical coupling of bare optoelectronic components and flexographically printed polymer waveguides in planar optronic systems

NASA Astrophysics Data System (ADS)

Wang, Yixiao; Wolfer, Tim; Lange, Alex; Overmeyer, Ludger

2016-05-01

Large scale, planar optronic systems allowing spatially distributed functionalities can be well used in diverse sensor networks, such as for monitoring the environment by measuring various physical quantities in medicine or aeronautics. In these systems, mechanically flexible and optically transparent polymeric foils, e.g. polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET), are employed as carrier materials. A benefit of using these materials is their low cost. The optical interconnections from light sources to light transmission structures in planar optronic systems occupy a pivotal position for the sensing functions. As light sources, we employ the optoelectronic components, such as edgeemitting laser diodes, in form of bare chips, since their extremely small structures facilitate a high integration compactness and ensure sufficient system flexibility. Flexographically printed polymer optical waveguides are deployed as light guiding structures for short-distance communication in planar optronic systems. Printing processes are utilized for this generation of waveguides to achieve a cost-efficient large scale and high-throughput production. In order to attain a high-functional optronic system for sensing applications, one of the most essential prerequisites is the high coupling efficiency between the light sources and the waveguides. Therefore, in this work, we focus on the multimode polymer waveguide with a parabolic cross-section and investigate its optical coupling with the bare laser diode. We establish the geometrical model of the alignment based on the previous works on the optodic bonding of bare laser diodes and the fabrication process of polymer waveguides with consideration of various parameters, such as the beam profile of the laser diode, the employed polymer properties of the waveguides as well as the carrier substrates etc. Accordingly, the optical coupling of the bare laser diodes and the polymer waveguides was simulated. Additionally, we demonstrate optical links by adopting the aforementioned processes used for defining the simulation. We verify the feasibility of the developed processes for planar optronic systems by using an active alignment and conduct discussions for further improvements of optical alignment.

A nano-scale mirror-like surface of Ti-6Al-4V attained by chemical mechanical polishing

NASA Astrophysics Data System (ADS)

Chenliang, Liang; Weili, Liu; Shasha, Li; Hui, Kong; Zefang, Zhang; Zhitang, Song

2016-05-01

Metal Ti and its alloys have been widely utilized in the fields of aviation, medical science, and micro-electro-mechanical systems, for its excellent specific strength, resistance to corrosion, and biological compatibility. As the application of Ti moves to the micro or nano scale, however, traditional methods of planarization have shown their short slabs. Thus, we introduce the method of chemical mechanical polishing (CMP) to provide a new way for the nano-scale planarization method of Ti alloys. We obtain a mirror-like surface, whose flatness is of nano-scale, via the CMP method. We test the basic mechanical behavior of Ti-6Al-4V (Ti64) in the CMP process, and optimize the composition of CMP slurry. Furthermore, the possible reactions that may take place in the CMP process have been studied by electrochemical methods combined with x-ray photoelectron spectroscopy (XPS). An equivalent circuit has been built to interpret the dynamic of oxidation. Finally, a model has been established to explain the synergy of chemical and mechanical effects in the CMP of Ti-6Al-4V. Project supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period of China (Grant No. 2009ZX02030-1), the National Natural Science Foundation of China (Grant No. 51205387), the Support by Science and Technology Commission of Shanghai City, China (Grant No. 11nm0500300), and the Science and Technology Commission of Shanghai City, China (Grant No. 14XD1425300).

Planar controlled zone microwave plasma system

DOEpatents

Ripley, Edward B [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Morrell, Jonathan S [Knoxvlle, TN

2011-10-04

An apparatus and method for initiating a process gas plasma. A conductive plate having a plurality of conductive fingers is positioned in a microwave applicator. An arc forms between the conductive fingers to initiate the formation of a plasma. A transport mechanism may convey process materials through the plasma. A spray port may be provided to expel processed materials.

In vitro quantification of the performance of model-based mono-planar and bi-planar fluoroscopy for 3D joint kinematics estimation.

PubMed

Tersi, Luca; Barré, Arnaud; Fantozzi, Silvia; Stagni, Rita

2013-03-01

Model-based mono-planar and bi-planar 3D fluoroscopy methods can quantify intact joints kinematics with performance/cost trade-off. The aim of this study was to compare the performances of mono- and bi-planar setups to a marker-based gold-standard, during dynamic phantom knee acquisitions. Absolute pose errors for in-plane parameters were lower than 0.6 mm or 0.6° for both mono- and bi-planar setups. Mono-planar setups resulted critical in quantifying the out-of-plane translation (error < 6.5 mm), and bi-planar in quantifying the rotation along bone longitudinal axis (error < 1.3°). These errors propagated to joint angles and translations differently depending on the alignment of the anatomical axes and the fluoroscopic reference frames. Internal-external rotation was the least accurate angle both with mono- (error < 4.4°) and bi-planar (error < 1.7°) setups, due to bone longitudinal symmetries. Results highlighted that accuracy for mono-planar in-plane pose parameters is comparable to bi-planar, but with halved computational costs, halved segmentation time and halved ionizing radiation dose. Bi-planar analysis better compensated for the out-of-plane uncertainty that is differently propagated to relative kinematics depending on the setup. To take its full benefits, the motion task to be investigated should be designed to maintain the joint inside the visible volume introducing constraints with respect to mono-planar analysis.

Structure and properties of B20Si-/0/+ clusters

NASA Astrophysics Data System (ADS)

Lu, Qi Liang; Luo, Qi Quan; Li, Yi De; Huang, Shou Guo

2018-06-01

A global search for the lowest energy structure of B20Si-, B20Si0 and B20Si+ clusters is conducted. Structural transitions at different charge states are observed. B20Si- is a 2D planar configuration with no polygonal holes, and Si atom occupies a peripheral position. B20Si+ adopts a 3D tubular shape, and each Si is bonded with four B atoms. But for B20Si0, competition among quasi-planar, tubular and cage like structures is found. These structures differ greatly from that of pure B21 - cluster. The structural transition may result from changes in the framework of bonding, sp 2 hybridization, and structural mechanics. Some of the clusters' properties including frontier molecular orbital, on-site charge on Si atom, electron density, and magnetism are also discussed.

Thermo-Mechanical and Electrochemistry Modeling of Planar SOFC Stacks

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

Khaleel, Mohammad A.; Recknagle, Kurtis P.; Lin, Zijing

2002-12-01

Modeling activities at PNNL support design and development of modular SOFC systems. The SOFC stack modeling capability at PNNL has developed to a level at which planar stack designs can be compared and optimized for startup performance. Thermal-fluids and stress modeling is being performed to predict the transient temperature distribution and to determine the thermal stresses based on the temperature distribution. Current efforts also include the development of a model for calculating current density, cell voltage, and heat production in SOFC stacks with hydrogen or other fuels. The model includes the heat generation from both Joule heating and chemical reactions.more » It also accounts for species production and destruction via mass balance. The model is being linked to the finite element code MARC to allow for the evaluation of temperatures and stresses during steady state operations.« less

An architecture for integrating planar and 3D cQED devices

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

Axline, C.; Reagor, M.; Heeres, R.

Numerous loss mechanisms can limit coherence and scalability of planar and 3D-based circuit quantum electrodynamics (cQED) devices, particularly due to their packaging. The low loss and natural isolation of 3D enclosures make them good candidates for coherent scaling. We introduce a coaxial transmission line device architecture with coherence similar to traditional 3D cQED systems. Measurements demonstrate well-controlled external and on-chip couplings, a spectrum absent of cross-talk or spurious modes, and excellent resonator and qubit lifetimes. We integrate a resonator-qubit system in this architecture with a seamless 3D cavity, and separately pattern a qubit, readout resonator, Purcell filter, and high-Q striplinemore » resonator on a single chip. Device coherence and its ease of integration make this a promising tool for complex experiments.« less

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

Zhuang, Jinda; Ju, Y. Sungtaek, E-mail: just@seas.ucla.edu

One major challenge in incorporating flexible electronics or optoelectronics on curved surfaces is the requirement of significant stretchability. We report a tunable platform for incorporating flexible and yet non-stretching device layers on a hemisphere. In this configuration, an array of planar petals contractively maps onto the surface of an inflatable hemisphere through elastocapillary interactions mediated by an interface liquid. A mechanical model is developed to elucidate the dependence of the conformality of the petal structures on their elastic modulus and thickness and the liquid surface tension. The modeling results are validated against experimental results obtained using petal structures of differentmore » thicknesses, restoring elastic spring elements of different spring constants, and liquids with different surface tension coefficients. Our platform will enable facile integration of non-stretching electronic and optoelectronic components prepared using established planar fabrication techniques on tunable hemispherical surfaces.« less

Integration of mechanism and control for large-angle slew maneuvers of flexible structures

NASA Technical Reports Server (NTRS)

Chew, Meng-Sang

1991-01-01

A rolling contact noncircular gear system is applied to assist a desired controller in the slewing of a flexible space structure. The varying gear ratio in cooperation with the controller results in lower feedback gains at the controller, as well as considerably reducing flexural vibrations of the space structure. The noncircular gears consist of a pair of convex noncircular cylinders with specially designed profiles that are synthesized in conjunction with the optimal controller gains for minimizing the flexural vibrations of flexible structure during a slew maneuver. Convexity of the cylindrical profiles for this noncircular gear device must be ensured to maintain rolling contact between the two cylinders. Simulations of slewing control tasks for two kinds of flexible space structures, such as a planar flexible beam and the planar articulated flexible beams, are presented.

Perspectives and Open Problems in the Early Phases of Left-Right Patterning

PubMed Central

Vandenberg, Laura N.; Levin, Michael

2009-01-01

Summary Embryonic left-right (LR) patterning is a fascinating aspect of embryogenesis. The field currently faces important questions about the origin of LR asymmetry, the mechanisms by which consistent asymmetry is imposed on the scale of the whole embryo, and the degree of conservation of early phases of LR patterning among model systems. Recent progress on planar cell polarity and cellular asymmetry in a variety of tissues and species provides a new perspective on the early phases of LR patterning. Despite the huge diversity in body-plans over which consistent LR asymmetry is imposed, and the apparent divergence in molecular pathways that underlie laterality, the data reveal conservation of physiological modules among phyla and a basic scheme of cellular chirality amplified by a planar cell polarity-like pathway over large cell fields. PMID:19084609

Planar Supported Membranes with Mobile SNARE Proteins and Quantitative Fluorescence Microscopy Assays to Study Synaptic Vesicle Fusion

PubMed Central

Kiessling, Volker; Liang, Binyong; Kreutzberger, Alex J. B.; Tamm, Lukas K.

2017-01-01

Synaptic vesicle membrane fusion, the process by which neurotransmitter gets released at the presynaptic membrane is mediated by a complex interplay between proteins and lipids. The realization that the lipid bilayer is not just a passive environment where other molecular players like SNARE proteins act, but is itself actively involved in the process, makes the development of biochemical and biophysical assays particularly challenging. We summarize in vitro assays that use planar supported membranes and fluorescence microscopy to address some of the open questions regarding the molecular mechanisms of SNARE-mediated membrane fusion. Most of the assays discussed in this mini-review were developed in our lab over the last 15 years. We emphasize the sample requirements that we found are important for the successful application of these methods. PMID:28360838

US-ROK Action Sheet 34: Safeguards Application of a Hand-held Mechanically Cooled Germanium Spectrometer

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

Dreyer, J.; Burks, M.; Ham, Y.

2015-10-20

This report summarizes results of Action Sheet 34 - for the cooperative efforts on the field testing and evaluation of a high-resolution, hand-held, gamma-ray spectrometer, known as SPG (Spectroscopic Planar Germanium), for safeguards application such as short notice inspections, UF6 analysis, enrichment determination, and other potential applications. The Spectroscopic Planar Germanium (SPG) has been demonstrated IAEA Physical Inventory Verification (PIV) in South Korea. This field test was a success and the feedback provided by KINAC, IAEA, and national laboratory staff was used to direct efforts to improve the instrument this year. Key points in this report include measurement results frommore » PIV, analysis of spectra with commercially available Ortec U235 and PC-FRAM, and completion of tripod and tungsten collimator and integration of user feedback.« less

To the theory of mechanisms subfamilies

NASA Astrophysics Data System (ADS)

Fomin, A.; Dvornikov, L.; Paramonov, M.; Jahr, A.

2016-04-01

The principles of formation of mechanisms subfamilies based on the usage of different kinds of kinematic pairs within the families of mechanisms are substantiated in the current paper. The division of mechanisms into subfamilies allows defining not only fundamental differences in the structure of mechanisms, but also provides the necessary foundation for the synthesis of new structures. 57 subfamilies of mechanisms have been totally distinguished. Among them, 31 subfamilies - within the zero family, 15 subfamilies - within the first family, 7 subfamilies - within the second family, 3 subfamilies - within the third family and 1 subfamily-within the fourth family. There were separately viewed planar mechanisms of the third family with three general imposed constraints and spatial mechanisms of the second family with two general imposed constraints in terms of their subfamilies. New methods of kinematical and dynamical investigations of mechanisms might be developed according to their analytical equations describing structural organization of different subfamilies of mechanisms.

Self-expanding/shrinking structures by 4D printing

NASA Astrophysics Data System (ADS)

Bodaghi, M.; Damanpack, A. R.; Liao, W. H.

2016-10-01

The aim of this paper is to create adaptive structures capable of self-expanding and self-shrinking by means of four-dimensional printing technology. An actuator unit is designed and fabricated directly by printing fibers of shape memory polymers (SMPs) in flexible beams with different arrangements. Experiments are conducted to determine thermo-mechanical material properties of the fabricated part revealing that the printing process introduced a strong anisotropy into the printed parts. The feasibility of the actuator unit with self-expanding and self-shrinking features is demonstrated experimentally. A phenomenological constitutive model together with analytical closed-form solutions are developed to replicate thermo-mechanical behaviors of SMPs. Governing equations of equilibrium are developed for printed structures based on the non-linear Green-Lagrange strain tensor and solved implementing a finite element method along with an iterative incremental Newton-Raphson scheme. The material-structural model is then applied to digitally design and print SMP adaptive lattices in planar and tubular shapes comprising a periodic arrangement of SMP actuator units that expand and then recover their original shape automatically. Numerical and experimental results reveal that the proposed planar lattice as meta-materials can be employed for plane actuators with self-expanding/shrinking features or as structural switches providing two different dynamic characteristics. It is also shown that the proposed tubular lattice with a self-expanding/shrinking mechanism can serve as tubular stents and grippers for bio-medical or piping applications.

A mechanism for decoupling within the oceanic lithosphere revealed in the Troodos ophiolite

USGS Publications Warehouse

Agar, Susan M.; Klitgord, Kim D.

1995-01-01

Contrasting kinematic histories recorded in the sheeted dykes and underlying plutonic rocks of the Troodos ophiolite provide a new perspective on the mechanical evolution of oceanic spreading centres. The kinematic framework of the decoupling zone that partitions deformation between the sheeted dykes and plutonics contrasts with low-angle detachment models for slow-spreading ridges based on continental-rift analogues. A model for the generation of multiple, horizontal decoupling horizons, linked by planar normal faults, demonstrates new possibilities for the kinematic and rheological significance of seismic reflectors in oceanic lithosphere.

Silicone substrate with in situ strain relief for stretchable thin-film transistors

NASA Astrophysics Data System (ADS)

Graz, Ingrid M.; Cotton, Darryl P. J.; Robinson, Adam; Lacour, Stéphanie P.

2011-03-01

We have manufactured stretchable thin-film transistors and interconnects directly onto an engineered silicone matrix with localized and graded mechanical compliance. The fabrication only involves planar and standard processing. Brittle active device materials are patterned on non deformable elastomer regions (strain <1% at all times) while interconnects run smoothly from "stiff" to "soft" elastomer. Pentacene thin-film transistors sustain applied strain up to 13% without electrical degradation and mechanical fracture. This integrated approach opens promising options for the manufacture of physically adaptable and transformable circuitry.

A Mathematica package for calculation of planar channeling radiation spectra of relativistic electrons channeled in a diamond-structure single crystal (quantum approach)

NASA Astrophysics Data System (ADS)

Azadegan, B.

2013-03-01

The presented Mathematica code is an efficient tool for simulation of planar channeling radiation spectra of relativistic electrons channeled along major crystallographic planes of a diamond-structure single crystal. The program is based on the quantum theory of channeling radiation which has been successfully applied to study planar channeling at electron energies between 10 and 100 MeV. Continuum potentials for different planes of diamond, silicon and germanium single crystals are calculated using the Doyle-Turner approximation to the atomic scattering factor and taking thermal vibrations of the crystal atoms into account. Numerical methods are applied to solve the one-dimensional Schrödinger equation. The code is designed to calculate the electron wave functions, transverse electron states in the planar continuum potential, transition energies, line widths of channeling radiation and depth dependencies of the population of quantum states. Finally the spectral distribution of spontaneously emitted channeling radiation is obtained. The simulation of radiation spectra considerably facilitates the interpretation of experimental data. Catalog identifier: AEOH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOH_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 446 No. of bytes in distributed program, including test data, etc.: 209805 Distribution format: tar.gz Programming language: Mathematica. Computer: Platforms on which Mathematica is available. Operating system: Operating systems on which Mathematica is available. RAM: 1 MB Classification: 7.10. Nature of problem: Planar channeling radiation is emitted by relativistic charged particles during traversing a single crystal in direction parallel to a crystallographic plane. Channeling is modeled as the motion of charged particles in a continuous planar potential which is formed by the spatially and thermally averaged action of the individual electrostatic potentials of the crystal atoms of the corresponding plane. Classically, the motion of channeled particles through the crystal resembles transverse oscillations being the source of radiation emission. For electrons of energy less than 100 MeV considered here, planar channeling has to be treated quantum mechanically by a one-dimensional Schrödinger equation for the transverse motion. Hence, this motion of the channeled electrons is restricted to a number of discrete (bound) channeling states in the planar continuum potential, and the emission of channeling radiation is caused by spontaneous electron transitions between these eigenstates. Due to relativistic and Doppler effects, the energy of the emitted photons directed into a narrow forward cone is typically shifted up by about three to five orders of magnitude. Consequently, the observed energy spectrum of channeling radiation is characterized by a number of radiation lines in the energy domain of hard X-rays. Channeling radiation may, therefore, be applied as an intense, tunable, quasi-monochromatic X-ray source. Solution method: The problem consists in finding the electron wave function for the planar continuum potential. Both the wave functions and corresponding energies of channeling states solve the Schrödinger equation of transverse electron motion. In the framework of the so-called many-beam formalism, solving the Schrödinger equation reduces to a eigenvector-eigenvalue problem of a Hermitian matrix. For that the program employs the mathematical tools allocated in the commercial computation software Mathematica. The electric field of the atomic planes in the crystal forces dipole oscillations of the channeled charged particles. In the quantum mechanical approach, the dipole approximation is also valid for spontaneous transitions between bound states. The transition strength for dedicated states depends on the magnitude of the corresponding dipole matrix element. The photon energy correlates with the particle energy, and the spectral width of radiation lines is a function of the life times of the channeling states. Running time: The program has been tested on a PC AMD Athlon X2 245 processor 2.9 GHz with 2 GB RAM. Depending on electron energy and crystal thickness, the running time of the program amounts to 5-10 min.

Planarization of metal films for multilevel interconnects

DOEpatents

Tuckerman, D.B.

1985-06-24

In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping lase pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

Planarization of metal films for multilevel interconnects

DOEpatents

Tuckerman, D.B.

1985-08-23

In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

Planarization of metal films for multilevel interconnects

DOEpatents

Tuckerman, D.B.

1989-03-21

In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration. 6 figs.

New squeezed landau states

NASA Technical Reports Server (NTRS)

Aragone, C.

1993-01-01

We introduce a new set of squeezed states through the coupled two-mode squeezed operator. It is shown that their behavior is simpler than the correlated coherent states introduced by Dodonov, Kurmyshev, and Man'ko in order to quantum mechanically describe the Landau system, i.e., a planar charged particle in a uniform magnetic field. We compare results for both sets of squeezed states.

The History of the Planar Elastica: Insights into Mechanics and Scientific Method

ERIC Educational Resources Information Center

Goss, Victor Geoffrey Alan

2009-01-01

Euler's formula for the buckling of an elastic column is widely used in engineering design. However, only a handful of engineers will be familiar with Euler's classic paper "De Curvis Elasticis" in which the formula is derived. In addition to the Euler Buckling Formula, "De Curvis Elasticis" classifies all the bent configurations of elastic rod--a…

Vascular stents with submicrometer-scale surface patterning realized via titanium deep reactive ion etching

NASA Astrophysics Data System (ADS)

Gott, Shannon C.; Jabola, Benjamin A.; Rao, Masaru P.

2015-08-01

Herein, we report progress towards realization of vascular stents that will eventually provide opportunity for evaluating cellular response to rationally-designed, submicrometer-scale surface patterning in physiologically-relevant contexts, i.e. those that provide exposure to the complex multicellular milieu, flow-induced shear, and tissue-device interactions present in vivo. Specifically, using our novel titanium deep reactive ion etching technique (Ti DRIE), we discuss recent advances that have enabled: (a) fabrication of precisely-defined, grating-based surface patterns on planar Ti foils with minimum feature sizes as small as 0.15 μm (b) creation of cylindrical stents from micromachined planar Ti foils; and (c) integration of these processes to produce the first submicrometer-scale surface-patterned Ti stents that are compatible with conventional balloon catheter deployment techniques. We also discuss results from elastoplastic finite element simulations and preliminary mechanical testing of these devices to assess their mechanical performance. These efforts represent key steps towards our long-term goal of developing a new paradigm in stenting, where rationally-designed surface patterning provides a physical means for facilitating healing, and thus, improving outcomes in vascular intervention applications.

Drawing dependent structures, mechanical properties and cyclization behaviors of polyacrylonitrile and polyacrylonitrile/carbon nanotube composite fibers prepared by plasticized spinning.

PubMed

Li, Xiang; Qin, Aiwen; Zhao, Xinzhen; Liu, Dapeng; Wang, Haiye; He, Chunju

2015-09-14

Drawing to change the structural properties and cyclization behaviors of the polyacrylonitrile (PAN) chains in crystalline and amorphous regions is carried out on PAN and PAN/carbon nanotube (CNT) composite fibers. Various characterization methods including Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermal gravimetric analysis are used to monitor the structural evolution and cyclization behaviors of the fibers. With an increase of the draw ratio during the plasticized spinning process, the structural parameters of the fibers, i.e. crystallinity and planar zigzag conformation, are decreased at first, and then increased, which are associated with the heat exchange rate and the oriented-crystallization rate. A possible mechanism for plasticized spinning is proposed to explain the changing trends of crystallinity and planar zigzag conformation. PAN and PAN/CNT fibers exhibit various cyclization behaviors induced by drawing, e.g., the initiation temperature for the cyclization (Ti) of PAN fibers is increased with increasing draw ratio, while Ti of PAN/CNT fibers is decreased. Drawing also facilitates cyclization and lowers the percentage of β-amino nitrile for PAN/CNT fibers during the stabilization.

Investigating Alkylsilane Monolayer Tribology at a Single-Asperity Contact with Molecular Dynamics Simulation.

PubMed

Summers, Andrew Z; Iacovella, Christopher R; Cummings, Peter T; McCabe, Clare

2017-10-24

Chemisorbed monolayer films are known to possess favorable characteristics for nanoscale lubrication of micro- and nanoelectromechanical systems (MEMS/NEMS). Prior studies have shown that the friction observed for monolayer-coated surfaces features a strong dependence on the geometry of contact. Specifically, tip-like geometries have been shown to penetrate into monolayer films, inducing defects in the monolayer chains and leading to plowing mechanisms during shear, which result in higher coefficients of friction (COF) than those observed for planar geometries. In this work, we use molecular dynamics simulations to examine the tribology of model silica single-asperity contacts under shear with monolayer-coated substrates featuring various film densities. It is observed that lower monolayer densities lead to reduced COFs, in contrast to results for planar systems where COF is found to be nearly independent of monolayer density. This is attributed to a liquid-like response to shear, whereby fewer defects are imparted in monolayer chains from the asperity, and chains are easily displaced by the tip as a result of the higher free volume. This transition in the mechanism of molecular plowing suggests that liquid-like films should provide favorable lubrication at single-asperity contacts.

Design of Mechanism for Assisting Standing Movement Using Planar Linkage and Gear Train

NASA Astrophysics Data System (ADS)

Nango, Jun; Yoshizawa, Hisato; Liu, Jiajun

The number of people who are in need of nursing care due to difficulties they experience with performing various activities of daily living is increasing. In particular, the action of standing up is performed frequently in daily life, and this action starts to induce pain in joints as people age. In this research, we develop a device whose seat plate follows the movement of the thigh in the action of standing up for the purpose of relieving the burden from the joints and reducing the effort associated with nursing care. The device is designed by using a planar five-link mechanism and a gear train, and only a single input is needed to drive the device. The respective lengths of the links are determined by comparing the movement of the seat plate of the device with the movement of the human thigh in the action of standing up. In addition, this device is expected to be useful for assisting users in standing up in a natural manner, including in the case when the body remains supported by the seat plate, as well as for guiding the individual movements of users in the action of standing up.

Structural design of a vertical antenna boresight 18.3 by 18.3-m planar near-field antenna measurement system

NASA Technical Reports Server (NTRS)

Sharp, G. R.; Trimarchi, P. A.; Wanhainen, J. S.

1984-01-01

A large very precise near-field planar scanner was proposed for NASA Lewis Research Center. This scanner would permit near-field measurements over a horizontal scan plane measuring 18.3 m by 18.3 m. Large aperture antennas mounted with antenna boresight vertical could be tested up to 60 GHz. When such a large near field scanner is used for pattern testing, the antenna or antenna system under test does not have to be moved. Hence, such antennas and antenna systems can be positioned and supported to simulate configuration in zero g. Thus, very large and heavy machinery that would be needed to accurately move the antennas are avoided. A preliminary investigation was undertaken to address the mechanical design of such a challenging near-field antenna scanner. The configuration, structural design and results of a parametric NASTRAN structural optimization analysis are contained. Further, the resulting design was dynamically analyzed in order to provide resonant frequency information to the scanner mechanical drive system designers. If other large near field scanners of comparable dimensions are to be constructed, the information can be used for design optimization of these also.

Atomisation and droplet formation mechanisms in a model two-phase mixing layer

NASA Astrophysics Data System (ADS)

Zaleski, Stephane; Ling, Yue; Fuster, Daniel; Tryggvason, Gretar

2017-11-01

We study atomization in a turbulent two-phase mixing layer inspired by the Grenoble air-water experiments. A planar gas jet of large velocity is emitted on top of a planar liquid jet of smaller velocity. The density ratio and momentum ratios are both set at 20 in the numerical simulation in order to ease the simulation. We use a Volume-Of-Fluid method with good parallelisation properties, implemented in our code http://parissimulator.sf.net. Our simulations show two distinct droplet formation mechanisms, one in which thin liquid sheets are punctured to form rapidly expanding holes and the other in which ligaments of irregular shape form and breakup in a manner similar but not identical to jets in Rayleigh-Plateau-Savart instabilities. Observed distributions of particle sizes are extracted for a sequence of ever more refined grids, the largest grid containing approximately eight billion points. Although their accuracy is limited at small sizes by the grid resolution and at large size by statistical effects, the distributions overlap in the central region. The observed distributions are much closer to log normal distributions than to gamma distributions as is also the case for experiments.

Fabrication of Circuits on Flexible Substrates Using Conductive SU-8 for Sensing Applications

PubMed Central

Gerardo, Carlos D.; Cretu, Edmond; Rohling, Robert

2017-01-01

This article describes a new low-cost rapid microfabrication technology for high-density interconnects and passive devices on flexible substrates for sensing applications. Silver nanoparticles with an average size of 80 nm were used to create a conductive SU-8 mixture with a concentration of wt 25%. The patterned structures after hard baking have a sheet resistance of 11.17 Ω/☐. This conductive SU-8 was used to pattern planar inductors, capacitors and interconnection lines on flexible Kapton film. The conductive SU-8 structures were used as a seed layer for a subsequent electroplating process to increase the conductivity of the devices. Examples of inductors, resistor-capacitor (RC) and inductor-capacitor (LC) circuits, interconnection lines and a near-field communication (NFC) antenna are presented as a demonstration. As an example of high-resolution miniaturization, we fabricated microinductors having line widths of 5 μm. Mechanical bending tests were successful down to a 5 mm radius. To the best of the authors’ knowledge, this is the first report of conductive SU-8 used to fabricate such planar devices and the first on flexible substrates. This is a proof of concept that this fabrication approach can be used as an alternative for microfabrication of planar passive devices on flexible substrates. PMID:28629134

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

Lloyd-Hughes, James; Mosley, C. D. W.; Jones, S. P. P.

Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La 0.7Sr 0.3MnO 3. At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: themore » mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. As a result, the VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.« less

Comparison of Extruded and Sonicated Vesicles for Planar Bilayer Self-Assembly

PubMed Central

Cho, Nam-Joon; Hwang, Lisa Y.; Solandt, Johan J.R.; Frank, Curtis W.

2013-01-01

Lipid vesicles are an important class of biomaterials that have a wide range of applications, including drug delivery, cosmetic formulations and model membrane platforms on solid supports. Depending on the application, properties of a vesicle population such as size distribution, charge and permeability need to be optimized. Preparation methods such as mechanical extrusion and sonication play a key role in controlling these properties, and yet the effects of vesicle preparation method on vesicular properties and integrity (e.g., shape, size, distribution and tension) remain incompletely understood. In this study, we prepared vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid by either extrusion or sonication, and investigated the effects on vesicle size distribution over time as well as the concomitant effects on the self-assembly of solid-supported planar lipid bilayers. Dynamic light scattering (DLS), quartz crystal microbalance with dissipation (QCM-D) monitoring, fluorescence recovery after photobleaching (FRAP) and atomic force microscopy (AFM) experiments were performed to characterize vesicles in solution as well as their interactions with silicon oxide substrates. Collectively, the data support that sonicated vesicles offer more robust control over the self-assembly of homogenous planar lipid bilayers, whereas extruded vesicles are vulnerable to aging and must be used soon after preparation. PMID:28811437

All substituted nickel porphyrins are highly nonplanar

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

Shelnutt, J.A.; Song, X.Z.; Jentzen, W.

1996-12-31

X-ray crystallographic and resonance Raman studies show that only un-substituted Ni porphine is planar in solution; all substituted Ni porphyrin derivatives either are nonplanar or exist as a mixture of planar and nonplanar conformers in solution. Recent modifications in a molecular mechanics force field improve the ability the MM calculations to predict the X-ray structures of porphyrins and also the planar-nonplanar conformational equilibria in many cases. Calculations using the new force field suggests that all geoporphyrins will be highly nonplanar, especially those having meso substituents. The nonplanarity is expected to influence properties such as solubility and metallation/dematallation reactions. Further, amore » method of quantifying these nonplanar structures has been devised; any porphyrin structure can be decomposed into displacements along the out-of-plane normal coordinates. However, usually distortions along only the lowest-frequency normal modes of each symmetry type are required to adequately describe the structure. The lowest-frequency normal coordinates of b{sub lu}, a{sub 2u}, b{sub 2u}, and e{sub g} symmetries correspond to commonly observed symmetric distortions called ruffling (ruf), doming(dom), saddling (sad), and waving (wav(x), wav(y)). The application of this structural decomposition method to several problems including the influences of steric crowding and protein folding on porphyrin conformation will be described.« less

New Insight into the Angle Insensitivity of Ultrathin Planar Optical Absorbers for Broadband Solar Energy Harvesting.

PubMed

Liu, Dong; Yu, Haitong; Duan, Yuanyuan; Li, Qiang; Xuan, Yimin

2016-09-01

Two challenging problems still remain for optical absorbers consisting of an ultrathin planar semiconductor film on top of an opaque metallic substrate. One is the angle-insensitive mechanism and the other is the system design needed for broadband solar energy harvesting. Here, first we theoretically demonstrates that the high refractive index, instead of the ultrathin feature as reported in previous studies, is the physical origin of the angle insensitivity for ultrathin planar optical absorbers. They exhibit omnidirectional resonance for TE polarization due to the high complex refractive index difference between the semiconductor and the air, while for TM polarization the angle insensitivity persists up to an incident angle related to the semiconductor refractive index. These findings were validated by fabricating and characterizing an 18 nm Ge/Ag absorber sample (representative of small band gap semiconductors for photovoltaic applications) and a 22 nm hematite/Ag sample (representative of large band gap semiconductors for photoelectrochemical applications). Then, we took advantage of angle insensitivity and designed a spectrum splitting configuration for broadband solar energy harvesting. The cascaded solar cell and unassisted solar water splitting systems have photovoltaic and photoelectrochemical cells that are also spectrum splitters, so an external spectrum splitting element is not needed.

Planarization of metal films for multilevel interconnects by pulsed laser heating

DOEpatents

Tuckerman, David B.

1987-01-01

In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

Continuous planar phospholipid bilayer supported on porous silicon thin film reflector.

PubMed

Cunin, Frédérique; Milhiet, Pierre-Emmanuel; Anglin, Emily; Sailor, Michael J; Espenel, Cédric; Le Grimellec, Christian; Brunel, Daniel; Devoisselle, Jean-Marie

2007-10-01

Reconstituting artificial membranes for in vitro studies of cell barrier mechanisms and properties is of major interest in biology. Here, artificial membranes supported on porous silicon photonic crystal reflectors are prepared and investigated. The materials are of interest for label-free probing of supported membrane events such as protein binding, molecular recognition, and transport. The porous silicon substrates are prepared as multilayered films consisting of a periodically varying porosity, with pore dimensions of a few nanometers in size. Planar phospholipid bilayers are deposited on the topmost surface of the oxidized hydrophilic mesoporous silicon films. Atomic force microscopy provides evidence of continuous bilayer deposition at the surface, and optical measurements indicate that the lipids do not significantly infiltrate the porous region. The presence of the supported bilayer does not obstruct the optical spectrum from the porous silicon layer, suggesting that the composite structures can act as effective optical biosensors.

Leakage and field emission in side-gate graphene field effect transistors

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

Di Bartolomeo, A., E-mail: dibant@sa.infn.it; Iemmo, L.; Romeo, F.

We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO{sub 2}/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO{sub 2} up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current densitymore » as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices.« less

Effect of Steel Galvanization on the Microstructure and Mechanical Performances of Planar Magnetic Pulse Welds of Aluminum and Steel

NASA Astrophysics Data System (ADS)

Avettand-Fènoël, M.-N.; Khalil, C.; Taillard, R.; Racineux, G.

2018-07-01

For the first time, planar joints between pure aluminum and galvanized or uncoated DP450 steel joints have been developed via magnetic pulse welding. Both present a wavy interface. The microstructure of the interfacial zone differs according to the joint. With uncoated steel, the interface is composed of discrete 2.5- µm-thick FeAl3 intermetallic compounds and Fe penetration lamellae, whereas the interface of the pure Al-galvanized steel joint is bilayered and composed of a 10-nm-thick (Al)Zn solid solution and a few micrometers thick aggregate of Al- and Zn-based grains, arranged from the Al side to the Zn coating. Even if the nature of the interfacial zone differs with or without the steel coating, both welds present rather similar maximum tensile forces and ductility in shear lap testing.

Spectral behavior of integrated optics asymmetric y-junction used for optimizing a planar optics telescope beam combiner

NASA Astrophysics Data System (ADS)

Schanen-Duport, Isabelle; Persegol, Dominique; Collomb, Virginie; Minier, Vincent; Haguenauer, Pierre

2017-11-01

Astronomical aperture synthesis requires to combine beams coming from telescopes, with constraints on mechanical and thermal stability, accuracy on the measurement of the interferences visibility. One adapted way for solving the problem is integrated planar optics. A first two telescope beam combiner made by ion exchange technique on glass substrate and build with symmetric Y-junction provides laboratory white light interferograms simultaneously with photometric calibration. In order to increase the interferometric signal without loss of photometric output, we propose to replace symmetric Y-junctions by asymmetric ones. In this paper, we report the conception, the manufacturing and the characterization of asymmetric Y-junction realized by ion exchange on glass substrate. The specific application of astronomical interferometry required the characterization of such component in term of spectral behavior, so we report the simulation and the measurement of asymmetric Y-junction response versus wavelength.

Morphological instability of a thermophoretically growing deposit

NASA Technical Reports Server (NTRS)

Castillo, Jose L.; Garcia-Ybarra, Pedro L.; Rosner, Daniel E.

1992-01-01

The stability of the planar interface of a structureless solid growing from a depositing component dilute in a carrier fluid is studied when the main solute transport mechanism is thermal (Soret) diffusion. A linear stability analysis, carried out in the limit of low growth Peclet number, leads to a dispersion relation which shows that the planar front is unstable either when the thermal diffusion factor of the condensing component is positive and the latent heat release is small or when the thermal diffusion factor is negative and the solid grows over a thermally-insulating substrate. Furthermore, the influence of interfacial energy effects and constitutional supersaturation in the vicinity of the moving interface is analyzed in the limit of very small Schmidt numbers (small solute Fickian diffusion). The analysis is relevant to physical vapor deposition of very massive species on cold surfaces, as in recent experiments of organic solid film growth under microgravity conditions.

Shock response of 7068 aluminium alloy

NASA Astrophysics Data System (ADS)

Chapman, David; Eakins, Daniel; Proud, William

2013-06-01

Aluminium alloys are widely employed throughout the aerospace and defence industries due to their high specific strength. Aluminium alloy 7068, often described as the ultimate aluminium alloy was developed by Kasier Aluminium in the mid-1990s and is the strongest aluminium commercially produced. There remains little published data on the response of this micro-structurally anisotropic alloy to dynamic loading. As part of an investigation of the high-rate mechanical properties of Al 7068, a series of plate-impact experiments using a novel meso-scale planar impact facility and a more conventional large bore gas gun were undertaken. The evolution of the elastic-plastic shock wave and spall strength as a function of sample thickness and specimen orientation were investigated using optical velocimetry (line-VISAR, PDV) techniques. Planar shock wave experiments were conducted on specimens several 100 microns to several millimetres thick cut from either parallel or perpendicular to the extrusion direction.

Planar cell polarity genes control the connectivity of enteric neurons

PubMed Central

Sasselli, Valentina; Boesmans, Werend; Vanden Berghe, Pieter; Tissir, Fadel; Goffinet, André M.; Pachnis, Vassilis

2013-01-01

A highly complex network of intrinsic enteric neurons is required for the digestive and homeostatic functions of the gut. Nevertheless, the genetic and molecular mechanisms that regulate their assembly into functional neuronal circuits are currently unknown. Here we report that the planar cell polarity (PCP) genes Celsr3 and Fzd3 are required during murine embryogenesis to specifically control the guidance and growth of enteric neuronal projections relative to the longitudinal and radial gut axes. Ablation of these genes disrupts the normal organization of nascent neuronal projections, leading to subtle changes of axonal tract configuration in the mature enteric nervous system (ENS), but profound abnormalities in gastrointestinal motility. Our data argue that PCP-dependent modules of connectivity established at early stages of enteric neurogenesis control gastrointestinal function in adult animals and provide the first evidence that developmental deficits in ENS wiring may contribute to the pathogenesis of idiopathic bowel disorders. PMID:23478408

A 5 meter range non-planar CMUT array for Automotive Collision Avoidance

NASA Astrophysics Data System (ADS)

Hernandez Aguirre, Jonathan

A discretized hyperbolic paraboloid geometry capacitive micromachined ultrasonic transducer (CMUT) array has been designed and fabricated for automotive collision avoidance. The array is designed to operate at 40 kHz, beamwidth of 40° with a maximum sidelobe intensity of -10dB. An SOI based fabrication technology has been used for the 5x5 array with 5 sensing surfaces along each x and y axis and 7 elevation levels. An assembly and packaging technique has been developed to realize the non-planar geometry in a PGA-68 package. A highly accurate mathematical method has been presented for analytical characterization of capacitive micromachined ultrasonic transducers (CMUTs) built with square diaphragms. The method uses a new two-dimensional polynomial function to more accurately predict the deflection curve of a multilayer square diaphragm subject to both mechanical and electrostatic pressure and a new capacitance model that takes into account the contribution of the fringing field capacitances.

Strain induced plasmon tuning in planar square-shaped aluminum nanoparticles array

NASA Astrophysics Data System (ADS)

Mokkath, Junais Habeeb

2018-06-01

Metal nanoparticle aggregate is an exciting platform for manipulating light-matter interactions at the nanoscale, thanks to the optically driven free electrons couple electrically across the inter-particle gap region. We use time dependent density functional theory calculations to investigate the optical response modulations in planar square-shaped aluminum nanoparticles array via morphology deformation (varying the inter-particle gap distance in the range of 2-20 Å) separately along one and two directions. We report the surprising observation that irrespective of the different morphology deformations, there exists a unique inter-particle gap distance of 12 Å for which, a maximum optical field enhancement can be achieved. We remark that plasmonic interaction between metal nanoparticles in an aggregate is controlled to a large extent by the size of the inter-particle gap distance. We believe that our quantum mechanical calculations will inspire and contribute to the design, control, and exploitation of aluminum based plasmonic devices.

Tunable Crystallinity and Charge Transfer in Two-Dimensional G-Quadruplex Organic Frameworks.

PubMed

Wu, Yi-Lin; Bobbitt, N Scott; Logsdon, Jenna L; Powers-Riggs, Natalia E; Nelson, Jordan N; Liu, Xiaolong; Wang, Timothy C; Snurr, Randall Q; Hupp, Joseph T; Farha, Omar K; Hersam, Mark C; Wasielewski, Michael R

2018-04-03

DNA G-quadruplex structures were recently discovered to provide reliable scaffolding for two-dimensional organic frameworks due to the strong hydrogen-bonding ability of guanine. Herein, 2,7-diaryl pyrene building blocks with high HOMO energies and large optical gaps are incorporated into G-quadruplex organic frameworks. The adjustable substitution on the aryl groups provides an opportunity to elucidate the framework formation mechanism; molecular non-planarity is found to be beneficial for restricting interlayer slippage, and the framework crystallinity is highest when intermolecular interaction and non-planarity strike a fine balance. When guanine-functionalized pyrenes are co-crystallized with naphthalene diimide, charge-transfer (CT) complexes are obtained. The photophysical properties of the pyrene-only and CT frameworks are characterized by UV/Vis and steady-state and time-resolved photoluminescence spectroscopies, and by EPR spectroscopy for the CT complex frameworks. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Steel Galvanization on the Microstructure and Mechanical Performances of Planar Magnetic Pulse Welds of Aluminum and Steel

NASA Astrophysics Data System (ADS)

Avettand-Fènoël, M.-N.; Khalil, C.; Taillard, R.; Racineux, G.

2018-05-01

For the first time, planar joints between pure aluminum and galvanized or uncoated DP450 steel joints have been developed via magnetic pulse welding. Both present a wavy interface. The microstructure of the interfacial zone differs according to the joint. With uncoated steel, the interface is composed of discrete 2.5-µm-thick FeAl3 intermetallic compounds and Fe penetration lamellae, whereas the interface of the pure Al-galvanized steel joint is bilayered and composed of a 10-nm-thick (Al)Zn solid solution and a few micrometers thick aggregate of Al- and Zn-based grains, arranged from the Al side to the Zn coating. Even if the nature of the interfacial zone differs with or without the steel coating, both welds present rather similar maximum tensile forces and ductility in shear lap testing.

Misalignments calibration in small-animal PET scanners based on rotating planar detectors and parallel-beam geometry.

PubMed

Abella, M; Vicente, E; Rodríguez-Ruano, A; España, S; Lage, E; Desco, M; Udias, J M; Vaquero, J J

2012-11-21

Technological advances have improved the assembly process of PET detectors, resulting in quite small mechanical tolerances. However, in high-spatial-resolution systems, even submillimetric misalignments of the detectors may lead to a notable degradation of image resolution and artifacts. Therefore, the exact characterization of misalignments is critical for optimum reconstruction quality in such systems. This subject has been widely studied for CT and SPECT scanners based on cone beam geometry, but this is not the case for PET tomographs based on rotating planar detectors. The purpose of this work is to analyze misalignment effects in these systems and to propose a robust and easy-to-implement protocol for geometric characterization. The result of the proposed calibration method, which requires no more than a simple calibration phantom, can then be used to generate a correct 3D-sinogram from the acquired list mode data.

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

NASA Astrophysics Data System (ADS)

Hamers, M. F.; Pennock, G. M.; Drury, M. R.

2017-04-01

The study of deformation features has been of great importance to determine deformation mechanisms in quartz. Relevant microstructures in both growth and deformation processes include dislocations, subgrains, subgrain boundaries, Brazil and Dauphiné twins and planar deformation features (PDFs). Dislocations and twin boundaries are most commonly imaged using a transmission electron microscope (TEM), because these cannot directly be observed using light microscopy, in contrast to PDFs. Here, we show that red-filtered cathodoluminescence imaging in a scanning electron microscope (SEM) is a useful method to visualise subgrain boundaries, Brazil and Dauphiné twin boundaries. Because standard petrographic thin sections can be studied in the SEM, the observed structures can be directly and easily correlated to light microscopy studies. In contrast to TEM preparation methods, SEM techniques are non-destructive to the area of interest on a petrographic thin section.

Alterations in geometry, biomechanics, and mineral composition of juvenile rat femur induced by nonplanar PCB-155 and/or planar PCB-169.

PubMed

Brankovič, Jana; Jovanovski, Sašo; Jevnikar, Peter; Hofmeister, Alexander; Reininger-Gutmann, Birgit; Jan, Janja; Grošelj, Maja; Osredkar, Joško; Uršič, Matjaž; Fazarinc, Gregor; Pogačnik, Azra; Vrecl, Milka

2017-04-01

Exposure to widespread lipophilic and bioaccumulative polychlorinated biphenyls (PCBs) induces diverse biochemical and toxicological responses in various organs, including the bone. The aim of this study was to evaluate the changes in growth rate, geometry, serum, and bone biochemical parameters and biomechanics of juvenile rat femur induced by lactational exposure to nonplanar PCB-155 and planar PCB-169 individually and in combination. Fifteen lactating Wistar rats were divided into four groups (PCB-169, PCB-155, PCB-155+169, and control), and PCBs were administered intraperitoneally at different time points after delivery. Femurs from 22-day-old offspring were analyzed by microCT, three-point bending test and inductively coupled plasma-mass spectrometry (ICP-MS) to obtain data on bone geometry, biomechanics and mineral composition. The serum levels of calcium, phosphate and alkaline phosphatase were also determined. Lactational exposure to planar PCB-169 resulted in shorter and thinner femurs, reduced endosteal and periosteal perimeters, smaller total cross-sectional and medullary areas, and lowered serum bone marker levels and calcium levels in the bone, while femur mechanical properties were not significantly altered. The changes observed in the combination exposure (PCB-155+169) group were similar to those observed in the PCB-169 group but were less pronounced. In summary, our results demonstrate that alterations in lactationally exposed offspring were primarily induced by planar PCB-169. The milder outcome in the combined group suggested that the PCB-169-mediated toxic effects on the bone might be reduced by a nonplanar PCB-155 congener. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1135-1146, 2017. © 2016 Wiley Periodicals, Inc.

Engineering three-dimensional cell mechanical microenvironment with hydrogels.

PubMed

Huang, Guoyou; Wang, Lin; Wang, Shuqi; Han, Yulong; Wu, Jinhui; Zhang, Qiancheng; Xu, Feng; Lu, Tian Jian

2012-12-01

Cell mechanical microenvironment (CMM) significantly affects cell behaviors such as spreading, migration, proliferation and differentiation. However, most studies on cell response to mechanical stimulation are based on two-dimensional (2D) planar substrates, which cannot mimic native three-dimensional (3D) CMM. Accumulating evidence has shown that there is a significant difference in cell behavior in 2D and 3D microenvironments. Among the materials used for engineering 3D CMM, hydrogels have gained increasing attention due to their tunable properties (e.g. chemical and mechanical properties). In this paper, we provide an overview of recent advances in engineering hydrogel-based 3D CMM. Effects of mechanical cues (e.g. hydrogel stiffness and externally induced stress/strain in hydrogels) on cell behaviors are described. A variety of approaches to load mechanical stimuli in 3D hydrogel-based constructs are also discussed.

Electrochemical characterization of bulk and thin film copper in ammonia- and nitric acid-based slurries for chemical mechanical planarization of interconnects

NASA Astrophysics Data System (ADS)

Sainio, Carlyn Anne

Copper will be replacing aluminum as the interconnect material in silicon integrated circuits. Chemical mechanical planarization (CMP) in combination with an inlaid metal interconnection scheme has been utilized to pattern copper interconnects. The thesis describes an attempt to understand the electrochemistry of copper in slurries used for CMP. Steady-state electrochemical potential measurements, linear polarization resistance determinations, and potentiodynamic and potentiostatic polarization scans have been used in order to characterize the mechanism by which copper is removed during CMP. Electrochemical measurements were implemented on a rotating disk assembly to simulate conditions during CMP. Experiments were performed on both bulk copper samples and blanket copper thin films sputter deposited onto silicon wafers. Electrochemical potential measurements have been used in conjunction with potential-pH diagrams to determine the possible copper species which are stable during CMP. Electrochemical results were correlated to CMP experiments to determine slurry compositions with optimum potential-pH ranges for copper planarization. The results indicate that such studies present an opportunity to isolate the electrochemical and chemical effects from the mechanical effects in the CMP of metals and to determine the dependencies of each of these effects on the other. CMP of copper was controlled by the removal of native or non-native surface films. High CMP rates were achieved by matching the rates of film formation and copper and film dissolution. During CMP, surface films are abraded, allowing increased dissolution of copper until the surface film reforms. When the surface was indented by abrasive particles, the corrosion rate of the exposed copper increased by two orders of magnitude. Etchants (i.e. ammonia or nitric acid) were necessary for high CMP rates (120-240 nm/min) and to minimize scratching. CMP rates of copper in 1 volume percent NHsb4OH and 0.7 volume percent HNOsb3 with 0.0016 weight percent KMnOsb4 were comparable. Electrochemical characterization can narrow the possible slurry compositions that may be used for polishing. Also, the possibility of implementing electrochemical techniques to detect the endpoint of polishing was investigated. Although electrochemical measurements in ammonia-based slurries did not indicate when tantalum was exposed, similar measurements may be used to determine when polishing pads should be replaced.

Self-propelled colloidal particle near a planar wall: A Brownian dynamics study

NASA Astrophysics Data System (ADS)

Mozaffari, Ali; Sharifi-Mood, Nima; Koplik, Joel; Maldarelli, Charles

2018-01-01

Miniaturized, self-propelled locomotors use chemo-mechanical transduction mechanisms to convert fuel in the environment to autonomous motion. Recent experimental and theoretical studies demonstrate that these autonomous engines can passively follow the contours of solid boundaries they encounter. Boundary guidance, however, is not necessarily stable: Mechanical disturbances can cause the motor to hydrodynamically depart from the passively guided pathway. Furthermore, given the scaled-down size of micromotors (typically 100 nm to10 μ m ), Brownian thermal fluctuation forces are necessarily important, and these stochastic forces can randomize passively steered trajectories. Here we examine theoretically the stability of boundary-guided motion of micromotors along infinite planar walls to mechanical disturbances and to Brownian forces. Our aim is to understand under what conditions this passively guided motion is stable. We choose a locomotor design in which spherical colloids are partially coated with a catalytic cap that reacts with solute to produce a product. The product is repelled from the particle surface, causing the particle to move with the inert face at the front (autonomous motion via self-diffusiophoresis). When propelled towards a planar wall, deterministic hydrodynamic studies demonstrate that these locomotors can exhibit, for large enough cap sizes, steady trajectories in which the particle either skims unidirectionally along the surface at a constant distance from the wall or becomes stationary. We first investigate the linear hydrodynamic stability of these states by expanding the equations of motion about the states, and we find that linear perturbations decay exponentially in time. We then study the effects of thermal fluctuations by formulating a Langevin equation for the particle motion which includes the Brownian stochastic force. The Péclet number scales the ratio of deterministic to Brownian forces, where Pe =π μ a2v˜c/kBT and a denotes the colloid radius, μ the continuous phase viscosity, v˜c the characteristic diffusiophoretic velocity, and kBT the thermal energy. The skimming and stationary states are found to persist for Pe above 103. At Pe below 200, the trajectory of a locomotor approaching the wall is unpredictable. We present representative individual trajectories along with probability distributions for statistical ensembles of particles, quantifying the effects of thermal fluctuations and illustrating the transition from unpredictable to passively guided motion.

Strategies for increasing the efficiency of heterojunction organic solar cells: material selection and device architecture.

PubMed

Heremans, Paul; Cheyns, David; Rand, Barry P

2009-11-17

Thin-film blends or bilayers of donor- and acceptor-type organic semiconductors form the core of heterojunction organic photovoltaic cells. Researchers measure the quality of photovoltaic cells based on their power conversion efficiency, the ratio of the electrical power that can be generated versus the power of incident solar radiation. The efficiency of organic solar cells has increased steadily in the last decade, currently reaching up to 6%. Understanding and combating the various loss mechanisms that occur in processes from optical excitation to charge collection should lead to efficiencies on the order of 10% in the near future. In organic heterojunction solar cells, the generation of photocurrent is a cascade of four steps: generation of excitons (electrically neutral bound electron-hole pairs) by photon absorption, diffusion of excitons to the heterojunction, dissociation of the excitons into free charge carriers, and transport of these carriers to the contacts. In this Account, we review our recent contributions to the understanding of the mechanisms that govern these steps. Starting from archetype donor-acceptor systems of planar small-molecule heterojunctions and solution-processed bulk heterojunctions, we outline our search for alternative materials and device architectures. We show that non-planar phthalocynanines have appealing absorption characteristics but also have reduced charge carrier transport. As a result, the donor layer needs to be ultrathin, and all layers of the device have to be tuned to account for optical interference effects. Using these optimization techniques, we illustrate cells with 3.1% efficiency for the non-planar chloroboron subphthalocyanine donor. Molecules offering a better compromise between absorption and carrier mobility should allow for further improvements. We also propose a method for increasing the exciton diffusion length by converting singlet excitons into long-lived triplets. By doping a polymer with a phosphorescent molecule, we demonstrate an increase in the exciton diffusion length of a polymer from 4 to 9 nm. If researchers can identify suitable phosphorescent dopants, this method could be employed with other materials. The carrier transport from the junction to the contacts is markedly different for a bulk heterojunction cell than for planar junction cells. Unlike for bulk heterojunction cells, the open-circuit voltage of planar-junction cells is independent of the contact work functions, as a consequence of the balance of drift and diffusion currents in these systems. This understanding helps to guide the development of new materials (particularly donor materials) that can further boost the efficiency of single-junction cells to 10%. With multijunction architectures, we expect that efficiencies of 12-16% could be attained, at which point organic photovoltaic cells could become an important renewable energy source.

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

Singleton, Jr., Robert

This report documents the implementation of several related 1D heat flow problems in the verification package ExactPack [1]. In particular, the planar sandwich class defined in Ref. [2], as well as the classes PlanarSandwichHot, PlanarSandwichHalf, and other generalizations of the planar sandwich problem, are defined and documented here. A rather general treatment of 1D heat flow is presented, whose main results have been implemented in the class Rod1D. All planar sandwich classes are derived from the parent class Rod1D.

Microstructure of wave propagation during combustion synthesis of advanced materials: Experiments and theory

NASA Astrophysics Data System (ADS)

Hwang, Stephen

Combustion synthesis (CS) is an attractive method for producing advanced materials, including ceramics, intermetallics, and composites. In this process, after initiation by an external heat source, a highly exothermic reaction propagates through the sample in a self-sustained combustion wave. The process offers the possibility of producing materials with novel structures and properties. At conventional magnifications and imaging rates, the combustion wave appears to propagate in a planar, steady manner. However, using higher magnifications (>400X) and imaging rates (1000 frames/sec), fluctuations in the shape and propagation of the combustion front were observed. These variations in local conditions (i.e., the microstructure of the combustion wave) can influence the microstructure and properties of materials produced by combustion synthesis. In this work, the microstructure of wave propagation during combustion synthesis is investigated experimentally and theoretically. Using microscopic high-speed imaging, the spatial and temporal fluctuations of the combustion front shape and propagation were investigated. New image analysis methods were developed to characterize the heterogeneity of the combustion front quantitatively. The initial organization of the reaction medium was found to affect the heterogeneity of the combustion wave. Moreover, at the microscopic level, two different regimes of combustion propagation were observed. In the quasihomogeneous mechanism, the microstructure of the combustion wave resembles what is viewed macroscopically, and steady, planar propagation is observed. In the relay-race mechanism, while planar at the macroscopic level, the combustion front profiles are irregularly shaped, with arc-shaped convexities and concavities at the microscopic level. Also, the reaction front propagates as a series of rapid jumps and hesitations. Based on the combustion wave microstructure, new criteria were developed to determine the boundaries between quasihomogeneous and relay-race mechanisms, as functions of the initial organization of the reaction medium (i.e. particle size and porosity). In conjunction with the experiments, a microheterogeneous cell model was developed that simulates the local propagation of the combustion wave. Accounting for the stochastically organized medium with non-uniform properties, calculated results for the microstructural parameters of the combustion wave, and their dependence on density and reactant particle size, were in good qualitative agreement with experimental data.

Efficacy of 67 gallium ECT imaging in lymphoma, infection, and lung carcinoma: A comparison with planar imaging

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

Harwood, S.J.; Anderson, M.W.; Klein, R.C.

1984-01-01

Emission computed tomography (ECT) studies were performed on a GE 400 A/T camera and ADAC computers (system 3 and system 3300). Thirty-three sets of ECT and planar images were obtained in 20 patients over a six month period. Imaging was performed 48 hours after the intravenous administration of 5 mc of Gallium 67 citrate. No bowel preparation was employed. Comparison is made of the initial nuclear medicine report derived from planar and ECT imaging aided by clinical knowledge versus the consensus opinion of two nuclear medicine physicians reading the planar images along with minimal clinical information. The lymphoma series consistsmore » of 18 scans in 10 patients. There were 5 scans in which a false negative planar interpretation was changed to a true positive ECT interpretation. Sensitivity of planar imaging for lymphoma was 58% which rose to 100% with addition of ECT information. There were no false positives by either technique. There were 5 sets of scans in 5 lung carcinoma patients. Sensitivity of the planar images was 60% because of 2 false negative results. Sensitivity of the ECT technique was 100%. There were no false positives. The infection series consists of 10 scans in 5 patients. Sensitivity of ECT was 100%, sensitivity of planar was 66%. There was 1 false positive planar. For the total series the accuracy of planar imaging was 69% and the predictive value of a negative planar interpretation was 44%. Corresponding values for ECT imaging were 100%. The authors' experience demonstrates significant increase in sensitivity without loss of specificity resulting from the use of Emission Computed Tomography in both chest and abdomen in patients with lymphoma, infection, and lung cancer.« less

Formation of gallium nitride templates and freestanding substrates by hydride vapor phase epitaxy for homoepitaxial growth of III-nitride devices

NASA Astrophysics Data System (ADS)

Williams, Adrian Daniel

Gallium nitride (GaN) is a direct wide band gap semiconductor currently under heavy development worldwide due to interest in its applications in ultra-violet optoelectronics, power electronics, devices operating in harsh environments (high temperature or corrorsive), etc. While a number of devices have been demonstrated with this material and its related alloys, the unavailability of GaN substrates is seen as one of the current major bottlenecks to both material quality and device performance. This dissertation is concerned with the synthesis of high quality GaN substrates by the hydride vapor phase epitaxy method (HVPE). In this work, the flow of growth precursors in a home-built HVPE reactor was modeled by the Navier-Stokes equation and solved by finite element analysis to promote uniformity of GaN on 2'' sapphire substrates. Kinetics of growth was studied and various regimes of growth were identified to establish a methodology for HVPE GaN growth, independent of reactor geometry. GaN templates as well as bulk substrates were fabricated in this work. Realization of freestanding GaN substrates was achieved through discovery of a natural stress-induced method of separating bulk GaN from sapphire via mechanical failure of a low-temperature GaN buffer layer. Such a process eliminates the need for pre- or post-processing of sapphire substrates, as is currently the standard. Stress in GaN-on-sapphire is discussed, with the dominant contributor identified as thermal stress due to thermal expansion coefficient mismatch between the two materials. This thermal stress is analyzed using Stoney's equation and conditions for crack-free growth of thick GaN substrates were identified. An etch-back process for planarizing GaN templates was also developed and successfully applied to rough GaN templates. The planarization of GaN has been mainly addressed by chemo-mechanical polishing (CMP) methods in the literature, with notable shortcomings including the inability to effectively planarize gallium-polar GaN, the preferred growth plane for devices. The process developed in this work bypasses the constraints of CMP, allowing for the planarization of all surfaces of GaN irrespective of crystal orientation. The GaN samples grown for this dissertation were studied by various techniques to characterize their structural, optical, and electrical properties.

Unveiling the mechanisms of dressed-photon-phonon etching based on hierarchical surface roughness measure

NASA Astrophysics Data System (ADS)

Naruse, Makoto; Yatsui, Takashi; Nomura, Wataru; Kawazoe, Tadashi; Aida, Masaki; Ohtsu, Motoichi

2013-02-01

Dressed-photon-phonon (DPP) etching is a disruptive technology in planarizing material surfaces because it completely eliminates mechanical contact processes. However, adequate metrics for evaluating the surface roughness and the underlying physical mechanisms are still not well understood. Here, we propose a two-dimensional hierarchical surface roughness measure, inspired by the Allan variance, that represents the effectiveness of DPP etching while conserving the original two-dimensional surface topology. Also, we build a simple physical model of DPP etching that agrees well with the experimental observations, which clearly shows the involvement of the intrinsic hierarchical properties of dressed photons, or optical near-fields, in the surface processing.

A Experimental Investigation of Hydrodynamic Forces on Circular Cylinders in Sinusoidal and Random Oscillating Flow

NASA Astrophysics Data System (ADS)

Longoria, Raul Gilberto

An experimental apparatus has been developed which can be used to generate a general time-dependent planar flow across a cylinder. A mass of water enclosed with no free surface within a square cross-section tank and two spring pre-loaded pistons is oscillated using a hydraulic actuator. A circular cylinder is suspended horizontally in the tank by two X-Y force transducers used to simultaneously measure the total in-line and transverse forces. Fluid motion is measured using a differential pressure transducer for instantaneous acceleration and an LVDT for displacement. This investigation provides measurement of forces on cylinders subjected to planar fluid flow velocity with a time (and frequency) dependence which more accurately represent the random conditions encountered in a natural ocean environment. The use of the same apparatus for both sinusoidal and random experiments provides a quantified assessment of the applicability of sinusoidal planar oscillatory flow data in offshore structure design methods. The drag and inertia coefficients for a Morison equation representation of the inline force are presented for both sinusoidal and random flow. Comparison of the sinusoidal results is favorable with those of previous investigations. The results from random experiments illustrates the difference in the force mechanism by contrasting the force transfer coefficients for the inline and transverse forces. It is found that application of sinusoidal results to random hydrodynamic inline force prediction using the Morison equation wrongly weighs the drag and inertia components, and the transverse force is overpredicted. The use of random planar oscillatory flow in the laboratory, contrasted with sinusoidal planar oscillatory flow, quantifies the accepted belief that the force transfer coefficients from sinusoidal flow experiments are conservative for prediction of forces on cylindrical structures subjected to random sea waves and the ensuing forces. Further analysis of data is conducted in the frequency domain to illustrate models used for predicting the power spectral density of the inline force including a nonlinear describing function method. It is postulated that the large-scale vortex activity prominent in sinusoidal oscillatory flow is subdued in random flow conditions.

Electrochemical planarization

DOEpatents

Bernhardt, A.F.; Contolini, R.J.

1993-10-26

In a process for fabricating planarized thin film metal interconnects for integrated circuit structures, a planarized metal layer is etched back to the underlying dielectric layer by electropolishing, ion milling or other procedure. Electropolishing reduces processing time from hours to minutes and allows batch processing of multiple wafers. The etched back planarized thin film interconnect is flush with the dielectric layer. 12 figures.

Integration of planar transformer and/or planar inductor with power switches in power converter

DOEpatents

Chen, Kanghua; Ahmed, Sayeed; Zhu, Lizhi

2007-10-30

A power converter integrates at least one planar transformer comprising a multi-layer transformer substrate and/or at least one planar inductor comprising a multi-layer inductor substrate with a number of power semiconductor switches physically and thermally coupled to a heat sink via one or more multi-layer switch substrates.

Enjoyment of Euclidean Planar Triangles

ERIC Educational Resources Information Center

Srinivasan, V. K.

2013-01-01

This article adopts the following classification for a Euclidean planar [triangle]ABC, purely based on angles alone. A Euclidean planar triangle is said to be acute angled if all the three angles of the Euclidean planar [triangle]ABC are acute angles. It is said to be right angled at a specific vertex, say B, if the angle ?ABC is a right angle…

Kirigami design and fabrication for biomimetic robotics

NASA Astrophysics Data System (ADS)

Rossiter, Jonathan; Sareh, Sina

2014-03-01

Biomimetics faces a continual challenge of how to bridge the gap between what Nature has so effectively evolved and the current tools and materials that engineers and scientists can exploit. Kirigami, from the Japanese `cut' and `paper', is a method of design where laminar materials are cut and then forced out-of-plane to yield 3D structures. Kirimimetic design provides a convenient and relatively closed design space within which to replicate some of the most interesting niche biological mechanisms. These include complex flexing organelles such as cilia in algae, energy storage and buckled structures in plants, and organic appendages that actuate out-of-plane such as the myoneme of the Vorticella protozoa. Where traditional kirigami employs passive materials which must be forced to transition to higher dimensions, we can exploit planar smart actuators and artificial muscles to create self-actuating kirigami structures. Here we review biomimetics with respect to the kirigami design and fabrication methods and examine how smart materials, including electroactive polymers and shape memory polymers, can be used to realise effective biomimetic components for robotic, deployable structures and engineering systems. One-way actuation, for example using shape memory polymers, can yield complete self-deploying structures. Bi-directional actuation, in contrast, can be exploited to mimic fundamental biological mechanisms such as thrust generation and fluid control. We present recent examples of kirigami robotic mechanisms and actuators and discuss planar fabrication methods, including rapid prototyping and 3D printing, and how current technologies, and their limitations, affect Kirigami robotics.

Assessing rockfall susceptibility in steep and overhanging slopes using three-dimensional analysis of failure mechanisms

USGS Publications Warehouse

Matasci, Battista; Stock, Greg M.; Jaboyedoff, Michael; Carrea, Dario; Collins, Brian D.; Guérin, Antoine; Matasci, G.; Ravanel, L.

2018-01-01

Rockfalls strongly influence the evolution of steep rocky landscapes and represent a significant hazard in mountainous areas. Defining the most probable future rockfall source areas is of primary importance for both geomorphological investigations and hazard assessment. Thus, a need exists to understand which areas of a steep cliff are more likely to be affected by a rockfall. An important analytical gap exists between regional rockfall susceptibility studies and block-specific geomechanical calculations. Here we present methods for quantifying rockfall susceptibility at the cliff scale, which is suitable for sub-regional hazard assessment (hundreds to thousands of square meters). Our methods use three-dimensional point clouds acquired by terrestrial laser scanning to quantify the fracture patterns and compute failure mechanisms for planar, wedge, and toppling failures on vertical and overhanging rock walls. As a part of this work, we developed a rockfall susceptibility index for each type of failure mechanism according to the interaction between the discontinuities and the local cliff orientation. The susceptibility for slope parallel exfoliation-type failures, which are generally hard to identify, is partly captured by planar and toppling susceptibility indexes. We tested the methods for detecting the most susceptible rockfall source areas on two famously steep landscapes, Yosemite Valley (California, USA) and the Drus in the Mont-Blanc massif (France). Our rockfall susceptibility models show good correspondence with active rockfall sources. The methods offer new tools for investigating rockfall hazard and improving our understanding of rockfall processes.

Detection of Sentinel Lymph Nodes in Gynecologic Tumours by Planar Scintigraphy and SPECT/CT

PubMed Central

Kraft, Otakar; Havel, Martin

2012-01-01

Objective: Assess the role of planar lymphoscintigraphy and fusion imaging of SPECT/CT in sentinel lymph node (SLN) detection in patients with gynecologic tumours. Material and Methods: Planar scintigraphy and hybrid modality SPECT/CT were performed in 64 consecutive women with gynecologic tumours (mean age 53.6 with range 30-77 years): 36 pts with cervical cancer (Group A), 21 pts with endometrial cancer (Group B), 7 pts with vulvar carcinoma (Group C). Planar and SPECT/CT images were interpreted separately by two nuclear medicine physicians. Efficacy of these two techniques to image SLN were compared. Results: Planar scintigraphy did not image SLN in 7 patients (10.9%), SPECT/CT was negative in 4 patients (6.3%). In 35 (54.7%) patients the number of SLNs captured on SPECT/CT was higher than on planar imaging. Differences in detection of SLN between planar and SPECT/CT imaging in the group of all 64 patients are statistically significant (p<0.05). Three foci of uptake (1.7% from totally visible 177 foci on planar images) in 2 patients interpreted on planar images as hot LNs were found to be false positive non-nodal sites of uptake when further assessed on SPECT/CT. SPECT/CT showed the exact anatomical location of all visualised sentinel nodes. Conclusion: In some patients with gynecologic cancers SPECT/CT improves detection of sentinel lymph nodes. It can image nodes not visible on planar scintigrams, exclude false positive uptake and exactly localise pelvic and paraaortal SLNs. It improves anatomic localization of SLNs. Conflict of interest:None declared. PMID:23486989

Effects of planar shear on the three-dimensional instability in flow past a circular cylinder

NASA Astrophysics Data System (ADS)

Park, Doohyun; Yang, Kyung-Soo

2018-03-01

A Floquet stability analysis has been carried out in order to investigate how a planar shear in wake flow affects the three-dimensional (3D) instability in the near-wake region. We consider a circular cylinder immersed in a freestream with planar shear. The cylinder was implemented in a Cartesian grid system by means of an immersed boundary method. Planar shear tends to promote the primary instability, known as Hopf bifurcation where steady flow bifurcates into time-periodic flow, in the sense that its critical Reynolds number decreases with increasing planar shear. The effects of planar shear on the 3D instability are different depending on the type of 3D instability. The flow asymmetry caused by the planar shear suppresses a QP-type mode but generates a C-type mode. The conventional A and B modes are stabilized by the planar shear, whereas mode C is intensified with increasing shear. The criticality of each 3D mode is discussed, and the neutral stability curves for each 3D mode are presented. The current Floquet results have been validated by using direct numerical simulation for some selected cases of flow parameters.

Modeling dispersive coupling and losses of localized optical and mechanical modes in optomechanical crystals

NASA Astrophysics Data System (ADS)

Eichenfield, Matt; Chan, Jasper; Safavi-Naeini, Amir H.; Vahala, Kerry J.; Painter, Oskar

2009-10-01

Periodically structured materials can sustain both optical and mechanical excitations which are tailored by the geometry. Here we analyze the properties of dispersively coupled planar photonic and phononic crystals: optomechanical crystals. In particular, the properties of co-resonant optical and mechanical cavities in quasi-1D (patterned nanobeam) and quasi-2D (patterned membrane) geometries are studied. It is shown that the mechanical Q and optomechanical coupling in these structures can vary by many orders of magnitude with modest changes in geometry. An intuitive picture is developed based upon a perturbation theory for shifting material boundaries that allows the optomechanical properties to be designed and optimized. Several designs are presented with mechanical frequency ~ 1-10 GHz, optical Q-factor Qo > 10^7, motional masses meff 100 femtograms, optomechanical coupling length LOM < 5 microns, and a radiation-limited mechanical Q-factor Qm > 10^7.

Learning planar Ising models

DOE PAGES

Johnson, Jason K.; Oyen, Diane Adele; Chertkov, Michael; ...

2016-12-01

Inference and learning of graphical models are both well-studied problems in statistics and machine learning that have found many applications in science and engineering. However, exact inference is intractable in general graphical models, which suggests the problem of seeking the best approximation to a collection of random variables within some tractable family of graphical models. In this paper, we focus on the class of planar Ising models, for which exact inference is tractable using techniques of statistical physics. Based on these techniques and recent methods for planarity testing and planar embedding, we propose a greedy algorithm for learning the bestmore » planar Ising model to approximate an arbitrary collection of binary random variables (possibly from sample data). Given the set of all pairwise correlations among variables, we select a planar graph and optimal planar Ising model defined on this graph to best approximate that set of correlations. Finally, we demonstrate our method in simulations and for two applications: modeling senate voting records and identifying geo-chemical depth trends from Mars rover data.« less

Learning planar Ising models

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

Johnson, Jason K.; Oyen, Diane Adele; Chertkov, Michael

Inference and learning of graphical models are both well-studied problems in statistics and machine learning that have found many applications in science and engineering. However, exact inference is intractable in general graphical models, which suggests the problem of seeking the best approximation to a collection of random variables within some tractable family of graphical models. In this paper, we focus on the class of planar Ising models, for which exact inference is tractable using techniques of statistical physics. Based on these techniques and recent methods for planarity testing and planar embedding, we propose a greedy algorithm for learning the bestmore » planar Ising model to approximate an arbitrary collection of binary random variables (possibly from sample data). Given the set of all pairwise correlations among variables, we select a planar graph and optimal planar Ising model defined on this graph to best approximate that set of correlations. Finally, we demonstrate our method in simulations and for two applications: modeling senate voting records and identifying geo-chemical depth trends from Mars rover data.« less

Bipolar pulse forming line

DOEpatents

Rhodes, Mark A.

2008-10-21

A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

Method of fabricating lipid bilayer membranes on solid supports

NASA Technical Reports Server (NTRS)

Cho, Nam-Joon (Inventor); Frank, Curtis W. (Inventor); Glenn, Jeffrey S. (Inventor); Cheong, Kwang Ho (Inventor)

2012-01-01

The present invention provides a method of producing a planar lipid bilayer on a solid support. With this method, a solution of lipid vesicles is first deposited on the solid support. Next, the lipid vesicles are destabilized by adding an amphipathic peptide solution to the lipid vesicle solution. This destabilization leads to production of a planar lipid bilayer on the solid support. The present invention also provides a supported planar lipid bilayer, where the planar lipid bilayer is made of naturally occurring lipids and the solid support is made of unmodified gold or titanium oxide. Preferably, the supported planar lipid bilayer is continuous. The planar lipid bilayer may be made of any naturally occurring lipid or mixture of lipids, including, but not limited to phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinsitol, cardiolipin, cholesterol, and sphingomyelin.

Development of a wavelength tunable filter using MEMS technology

NASA Astrophysics Data System (ADS)

Liu, Junting

Microelectromechanical systems (MEMS) for optical applications have received intensive attention in recent years because of their potential applications in optical telecommunication. Traditional wavelength division multiplexing (WDM) offers high capacity but requires the fabrication of selective add-drop filters. MEMS technology offers an effective way to fabricate these components at low cost. This thesis presents the development of a device that tunes the Bragg wavelength by coupling into the evanescent field of the grating. A Bragg grating is a periodic perturbation of the refractive index along a fiber or a periodic perturbation of the structure of a planar waveguide. The Bragg wavelength can be tuned by changing the degree to which a dielectric slab couples into the evanescent field. The result is a change in the effective index of the grating, and thus a change in the wavelength that which it reflects. In this thesis Bragg gratings were successfully written into an optical fiber using phase mask technique. Mechanical polishing was used to side-polish the fiber and remove cladding to expose the core. Grating structures were also fabricated in planar waveguide using E-beam writing and dry etching. In order to achieve the smoothest possible morphology of the waveguide, plasma dry etching of transparent substrates was studied in great detail. It is found that the pre-etch cleaning procedure greatly influences the ability to obtain a smooth etched surface. Upper limits of evanescent field tuning were investigated by applying different index liquids such as D. I. water and index matching oils or by positioning different dielectric materials such as glass and silicon close to the grating. Planar waveguides were found to be more sensitive to effective index change. Two kinds of computer simulation were carried out to understand the mode profile and to estimate the value of effective index of planar waveguide under "dry" and "wet" conditions. The first one used an average depth of grating approximation. The second explicitly considered the corrugated structure of the waveguide. Results of both simulations were compared with the experimental results in order to find the proper simulation approach. The fiber or planar waveguide gratings were "device" integrated and their pro and cons were compared. Devices using an optical fiber employed a microactuator driven by electrothermal vibromotor to change the degree of coupling between fiber and "tuning block". Device using planar waveguides used an electrostatic force actuated membrane, flip-chip mounted atop the waveguide. All devices were fabricated using polysilicon surface micromachining processes. I concluded that devices driven by electrostatic force were easier to actuate and their integration with waveguide less challenging.

Burning mechanism and regression rate of RX-35-AU and RX-35-AV as a function of HMX particle size measured by the hybrid closed bomb-strand burner

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

Tao, W.C.; Costantino, M.S.; Ornellas, D.L.

1990-04-01

In this study, the average surface regression rate of two HMX-based cast explosives, RX-35-AU and RX-35-AV, is measured to pressures above 750 MPa using a hybrid closed bomb-strand burner. The hybrid design allows the simultaneous measurement of pressure and regression rate over a large range of pressures in each experiment. Nitroglycerin/Triacetin (75/25) and polyethylene glycol (PEG) are used as the energetic plasticizer and polymeric binder, respectively, in both formulations. The HMX solids loading in each formulation is 50 wt %, consisting of a narrow particle size distribution of 6--8 {mu}m for RX-35-AU and 150--177 {mu}m for RX-35-AV. Of special interestmore » are the regression rate and burning mechanism as a function of the initial particle size distribution and the mechanical properties fo the cast explosives. In general, the regression rate for the larger particle size formulation, RX-35-AV, is two to three times faster compared to that for RX-35-AU. Up to 750 MPa and independent of the initial confinement pressure, RX-35-AU exhibits a planar burning mechanism with the regression rate obeying the classical aP{sup n} formalism. For RX-35-AV, however, the burning behavior is erratic for samples ignited at 200 MPa confinement pressure. At confinement pressures above 400 MPa, the regression exhibits more of a planar burning mechanism. The unstable combustion behavior for RX-35-AV at lower confinement pressures is related to several mechanisms: (1) an abrupt increase in surface area due to particle fracture and subsequent translation and rotation, resulting in debonding and creating porosity, (2) thixotropic'' separation of the binder and nitramine, causing the significantly greater fracture damage to the nitramine during the loading cycle, (3) microscopic damage to the nitramine crystals that increase its intrinsic burning rate. 12 refs., 8 figs., 2 tabs.« less

Cold cathode emission studies on topographically modified few layer and single layer MoS2 films

NASA Astrophysics Data System (ADS)

Gaur, Anand P. S.; Sahoo, Satyaprakash; Mendoza, Frank; Rivera, Adriana M.; Kumar, Mohit; Dash, Saroj P.; Morell, Gerardo; Katiyar, Ram S.

2016-01-01

Nanostructured materials, such as carbon nanotubes, are excellent cold cathode emitters. Here, we report comparative field emission (FE) studies on topographically tailored few layer MoS2 films consisting of ⟨0001⟩ plane perpendicular (⊥) to c-axis (i.e., edge terminated vertically aligned) along with planar few layer and monolayer (1L) MoS2 films. FE measurements exhibited lower turn-on field Eto (defined as required applied electric field to emit current density of 10 μA/cm2) ˜4.5 V/μm and higher current density ˜1 mA/cm2, for edge terminated vertically aligned (ETVA) MoS2 films. However, Eto magnitude for planar few layer and 1L MoS2 films increased further to 5.7 and 11 V/μm, respectively, with one order decrease in emission current density. The observed differences in emission behavior, particularly for ETVA MoS2 is attributed to the high value of geometrical field enhancement factor (β), found to be ˜1064, resulting from the large confinement of localized electric field at edge exposed nanograins. Emission behavior of planar few layers and 1L MoS2 films are explained under a two step emission mechanism. Our studies suggest that with further tailoring the microstructure of ultra thin ETVA MoS2 films would result in elegant FE properties.

Colossal Terahertz Magnetoresistance at Room Temperature in Epitaxial La0.7Sr0.3MnO3 Nanocomposites and Single-Phase Thin Films.

PubMed

Lloyd-Hughes, J; Mosley, C D W; Jones, S P P; Lees, M R; Chen, A; Jia, Q X; Choi, E-M; MacManus-Driscoll, J L

2017-04-12

Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La 0.7 Sr 0.3 MnO 3 . At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. The VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.

Self-propulsion of a planar electric or magnetic microbot immersed in a polar viscous fluid

NASA Astrophysics Data System (ADS)

Felderhof, B. U.

2011-05-01

A planar sheet immersed in an electrically polar liquid like water can propel itself by means of a plane wave charge density propagating in the sheet. The corresponding running electric wave polarizes the fluid and causes an electrical torque density to act on the fluid. The sheet is convected by the fluid motion resulting from the conversion of rotational particle motion, generated by the torque density, into translational fluid motion by the mechanism of friction and spin diffusion. Similarly, a planar sheet immersed in a magnetic ferrofluid can propel itself by means of a plane wave current density in the sheet and the torque density acting on the fluid corresponding to the running wave magnetic field and magnetization. The effect is studied on the basis of the micropolar fluid equations of motion and Maxwell’s equations of electrostatics or magnetostatics, respectively. An analytic expression is derived for the velocity of the sheet by perturbation theory to second order in powers of the amplitude of the driving charge or current density. Under the assumption that the equilibrium magnetic equation of state may be used in linearized form and that higher harmonics than the first may be neglected, a set of self-consistent integral equations is derived which can be solved numerically by iteration. In typical situations the second-order perturbation theory turns out to be quite accurate.

Effect of Low Temperature on Charge Transport in Operational Planar and Mesoporous Perovskite Solar Cells.

PubMed

Petrović, Miloš; Ye, Tao; Chellappan, Vijila; Ramakrishna, Seeram

2017-12-13

Low-temperature optoelectrical studies of perovskite solar cells using MAPbI 3 and mixed-perovskite absorbers implemented into planar and mesoporous architectures reveal fundamental charge transporting properties in fully assembled devices operating under light bias. Both types of devices exhibit inverse correlation of charge carrier lifetime as a function of temperature, extending carrier lifetimes upon temperature reduction, especially after exposure to high optical biases. Contribution of bimolecular channels to the overall recombination process should not be overlooked because the density of generated charge surpasses trap-filling concentration requirements. Bimolecular charge recombination coefficient in both device types is smaller than Langevin theory prediction, and its mean value is independent of the applied illumination intensity. In planar devices, charge extraction declines upon MAPbI 3 transition from a tetragonal to an orthorhombic phase, indicating a connection between the trapping/detrapping mechanism and temperature. Studies on charge extraction by linearly increasing voltage further support this assertion, as charge carrier mobility dependence on temperature follows multiple-trapping predictions for both device structures. The monotonously increasing trend following the rise in temperature opposes the behavior observed in neat perovskite films and indicates the importance of transporting layers and the effect they have on charge transport in fully assembled solar cells. Low-temperature phase transition shows no pattern of influence on thermally activated electron/hole transport.

Colossal terahertz magnetoresistance at room temperature in epitaxial La 0.7Sr 0.3MnO 3 nanocomposites and single-phase thin films

DOE PAGES

Lloyd-Hughes, James; Mosley, C. D. W.; Jones, S. P. P.; ...

2017-03-13

Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La 0.7Sr 0.3MnO 3. At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: themore » mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. This suggests that colossal magnetoresistance at THz frequencies may find use in nanoelectronics and in THz optical components controlled by magnetic fields. As a result, the VAN can be scaled in thickness while retaining a high structural quality and offers a larger THz CMR at room temperature than the planar film.« less

A chemically defined substrate for the expansion and neuronal differentiation of human pluripotent stem cell-derived neural progenitor cells.

PubMed

Tsai, Yihuan; Cutts, Josh; Kimura, Azuma; Varun, Divya; Brafman, David A

2015-07-01

Due to the limitation of current pharmacological therapeutic strategies, stem cell therapies have emerged as a viable option for treating many incurable neurological disorders. Specifically, human pluripotent stem cell (hPSC)-derived neural progenitor cells (hNPCs), a multipotent cell population that is capable of near indefinite expansion and subsequent differentiation into the various cell types that comprise the central nervous system (CNS), could provide an unlimited source of cells for such cell-based therapies. However the clinical application of these cells will require (i) defined, xeno-free conditions for their expansion and neuronal differentiation and (ii) scalable culture systems that enable their expansion and neuronal differentiation in numbers sufficient for regenerative medicine and drug screening purposes. Current extracellular matrix protein (ECMP)-based substrates for the culture of hNPCs are expensive, difficult to isolate, subject to batch-to-batch variations, and, therefore, unsuitable for clinical application of hNPCs. Using a high-throughput array-based screening approach, we identified a synthetic polymer, poly(4-vinyl phenol) (P4VP), that supported the long-term proliferation and self-renewal of hNPCs. The hNPCs cultured on P4VP maintained their characteristic morphology, expressed high levels of markers of multipotency, and retained their ability to differentiate into neurons. Such chemically defined substrates will eliminate critical roadblocks for the utilization of hNPCs for human neural regenerative repair, disease modeling, and drug discovery. Copyright © 2015. Published by Elsevier B.V.

A look at 15 years of planar thallium-201 imaging

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

Kaul, S.

1989-09-01

Extensive experience has been accumulated over the past 15 years regarding planar thallium-201 imaging. Quantitation of technically superior images provides a high sensitivity and specificity for the detection of CAD. In addition, planar thallium-201 images provide very important prognostic information in different clinical situations. Although single photon emission computerized tomography offers potential theoretical advantages over planar imaging, because of the problems involved in reconstruction, specifically the creation of artifacts, it may not be the ideal imaging modality in all situations. Good quality planar thallium-201 imaging still has an important role in clinical cardiology today. 144 references.

Chip-based device for parallel sorting, amplification, detection, and identification of nucleic acid subsequences

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

Beer, Neil Reginald; Colston, Jr, Billy W.

An apparatus for chip-based sorting, amplification, detection, and identification of a sample having a planar substrate. The planar substrate is divided into cells. The cells are arranged on the planar substrate in rows and columns. Electrodes are located in the cells. A micro-reactor maker produces micro-reactors containing the sample. The micro-reactor maker is positioned to deliver the micro-reactors to the planar substrate. A microprocessor is connected to the electrodes for manipulating the micro-reactors on the planar substrate. A detector is positioned to interrogate the sample contained in the micro-reactors.

Planarization of metal films for multilevel interconnects

DOEpatents

Tuckerman, David B.

1987-01-01

In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

Planarization of metal films for multilevel interconnects

DOEpatents

Tuckerman, David B.

1989-01-01

In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

Analytical expressions for stability regions in the Ince-Strutt diagram of Mathieu equation

NASA Astrophysics Data System (ADS)

Butikov, Eugene I.

2018-04-01

Simple analytical expressions are suggested for transition curves that separate, in the Ince-Strutt diagram, different types of solutions to the famous Mathieu equation. The derivations of these expressions in this paper rely on physically meaningful periodic solutions describing various regular motions of a familiar nonlinear mechanical system—a rigid planar pendulum with a vertically oscillating pivot. The paper is accompanied by a relevant simulation program.

A Low-wear Planar-contact Silicon Raceway for Microball Bearing Applications

DTIC Science & Technology

2009-04-01

of friction between stainless steel microballs and silicon grooves (18–20). Both linear and rotary micromotors for sensor platforms were developed...mechanism, like a micromotor , will enable devices to reach higher speeds. Previously, the radial surface wear track depth was >15 m for a device...can lead to significant whirl and axial misalignment, which is critical for micromotor and micropump applications. Small changes in the alignment

Comparative study of tow buckling defect during preforming of structural composites based on vegetable fibers

NASA Astrophysics Data System (ADS)

Salem, Mohamed; Fazzini, Marina; Ouagne, Pierre

2018-02-01

During the complex shape forming of composite fibrous reinforcement, the planar bending of roving tows results in an out-of-plane deflection, along with a rotation on its central axis. The need to accurately follow and quantify the mechanism of formation of such defect has led us to consider two 3D imaging techniques, of which, have been tested and compared in this work.

Effect of photocatalytic oxidation technology on GaN CMP

NASA Astrophysics Data System (ADS)

Wang, Jie; Wang, Tongqing; Pan, Guoshun; Lu, Xinchun

2016-01-01

GaN is so hard and so chemically inert that it is difficult to obtain a high material removal rate (MRR) in the chemical mechanical polishing (CMP) process. This paper discusses the application of photocatalytic oxidation technology in GaN planarization. Three N-type semiconductor particles (TiO2, SnO2, and Fe2O3) are used as catalysts and added to the H2O2-SiO2-based slurry. By optical excitation, highly reactive photoinduced holes are produced on the surface of the particles, which can oxidize OH- and H2O absorbed on the surface of the catalysts; therefore, more OH* will be generated. As a result, GaN MRRs in an H2O2-SiO2-based polishing system combined with catalysts are improved significantly, especially when using TiO2, the MRR of which is 122 nm/h. The X-ray photoelectron spectroscopy (XPS) analysis shows the variation trend of chemical composition on the GaN surface after polishing, revealing the planarization process. Besides, the effect of pH on photocatalytic oxidation combined with TiO2 is analyzed deeply. Furthermore, the physical model of GaN CMP combined with photocatalytic oxidation technology is proposed to describe the removal mechanism of GaN.

An apparatus to estimate the hydrodynamic coefficients of autonomous underwater vehicles using water tunnel testing.

PubMed

Nouri, N M; Mostafapour, K; Bahadori, R

2016-06-01

Hydrodynamic coefficients or hydrodynamic derivatives of autonomous underwater vehicles (AUVs) play an important role in their development and maneuverability. The most popular way of estimating their coefficients is to implement captive model tests such as straight line tests and planar motion mechanism (PMM) tests in the towing tanks. This paper aims to develop an apparatus based on planar experiments of water tunnel in order to estimate hydrodynamic derivatives due to AUVs' acceleration and velocity. The capability of implementing straight line tests and PMM ones using mechanical oscillators located in the downstream flow of the model is considered in the design procedure of the system. The hydrodynamic derivatives that resulted from the acceleration and velocity of the AUV model were estimated using the apparatus that we developed. Static and dynamics test results were compared for the similar derivatives. The findings showed that the system provided the basis for conducting static tests, i.e., straight-line and dynamic tests that included pure pitch and pure heave. By conducting such tests in a water tunnel, we were able to eliminate errors related to the time limitation of the tests and the effects of surface waves in the towing tank on AUVs with applications in the deep sea.

Chemical-mechanical planarization of aluminum and copper interconnects with magnetic liners

NASA Astrophysics Data System (ADS)

Wang, Bin

2000-10-01

Chemical Mechanical Planarization (CMP) has been employed to achieve Damascene patterning of aluminum and copper interconnects with unique magnetic liners. A one-step process was developed for each interconnect scheme, using a double-layered pad with mesh cells, pores, and perforations on a top hard layer. In a hydrogen peroxide-based slurry, aluminum CMP was a process of periodic removal and formation of a surface oxide layer. Cu CMP in the same slurry, however, was found to be a dissolution dominant process. In a potassium iodate-based slurry, copper removal was the result of two competing reactions: copper dissolution and a non-native surface layer formation. Guided by electrochemistry, slurries were developed to remove nickel in different regimes of the corrosion kinetics diagram. Nickel CMP in a ferric sulfate-based slurry resulted in periodic removal and formation of a passive surface layer. In a potassium permanganate-based slurry, nickel removal is a dissolution dominant process. Visible Al(Cu) surface damages obtained with copper-doped aluminum could be eliminated by understanding the interactions between the substrate, the pad, and the abrasive agglomerate. Increasing substrate hardness by annealing prior to CMP led to a surface finish free of visible scratches. A similar result was also obtained by preventing formation of abrasive agglomerates and minimizing their contact with the substrate.

Numerical simulation of stress amplification induced by crack interaction in human femur bone

NASA Astrophysics Data System (ADS)

Alia, Noor; Daud, Ruslizam; Ramli, Mohammad Fadzli; Azman, Wan Zuki; Faizal, Ahmad; Aisyah, Siti

2015-05-01

This research is about numerical simulation using a computational method which study on stress amplification induced by crack interaction in human femur bone. Cracks in human femur bone usually occur because of large load or stress applied on it. Usually, the fracture takes longer time to heal itself. At present, the crack interaction is still not well understood due to bone complexity. Thus, brittle fracture behavior of bone may be underestimated and inaccurate. This study aims to investigate the geometrical effect of double co-planar edge cracks on stress intensity factor (K) in femur bone. This research focuses to analyze the amplification effect on the fracture behavior of double co-planar edge cracks, where numerical model is developed using computational method. The concept of fracture mechanics and finite element method (FEM) are used to solve the interacting cracks problems using linear elastic fracture mechanics (LEFM) theory. As a result, this study has shown the identification of the crack interaction limit (CIL) and crack unification limit (CUL) exist in the human femur bone model developed. In future research, several improvements will be made such as varying the load, applying thickness on the model and also use different theory or method in calculating the stress intensity factor (K).

Electron-transfer boat-vibration mechanism for superconductivity in organic molecules based on BEDT-TTF

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

Demiralp, E.; Dasgupta, S.; Goddard, W.A. III

1995-08-09

The highest T{sub c} organic superconductors all involve the organic molecule bis(ethylenedithio)tetrathiafulvalene (denoted as BEDT-TTF or ET) coupled with an appropriate acceptor. This leads to ET, ET{sup +}, or (ET){sub 2}{sup +} species in the crystal. Using ab initio Hartree-Fock calculations (6-31G** basis set), we show that ET deforms to a boat structure with an energy 28 meV (0.65 kcal/mol) lower than that of planar ET (D{sub 2} symmetry). On the other hand, ET{sup +} is planar. Thus, conduction in this system leads to a coupling between charge transfer and the boat deformation vibrational modes at 20 cm{sup -1} (ET)more » and 28 cm{sup -1} (ET{sup +}). We suggest that this electron-phonon coupling is responsible for the superconductivity and predict the isotope shifts ({delta}T{sub c}) for experimental tests of the electron-transfer boat-vibration (ET-BV) mechanism. The low frequency of this boat mode and its coupling to various lattice modes could explain the sensitivity of T{sub c} to defects, impurities, and pressure. We suggest that new higher temperature organic donors can be sought by finding modifications that change the frequency and stability of this boat distortion mode. 25 refs., 5 figs., 4 tabs.« less

[Optical Design of Miniature Infrared Gratings Spectrometer Based on Planar Waveguide].

PubMed

Li, Yang-yu; Fang, Yong-hua; Li, Da-cheng; Liu, Yang

2015-03-01

In order to miniaturize an infrared spectrometer, we analyze the current optical design of miniature spectrometers and propose a method for designing a miniature infrared gratings spectrometer based on planar waveguide. Common miniature spectrometer uses miniature optical elements to reduce the size of system, which also shrinks the effective aperture. So the performance of spectrometer has dropped. Miniaturization principle of planar waveguide spectrometer is different from the principle of common miniature spectrometer. In planar waveguide spectrometer, the propagation of light is limited in a thin planar waveguide, which looks like the whole optical system is squashed flat. In the direction parallel to the planar waveguide, the light through the slit is collimated, dispersed and focused. And a spectral image is formed in the detector plane. This propagation of light is similar to the light in common miniature spectrometer. In the direction perpendicular to the planar waveguide, light is multiple reflected by the upper and lower surfaces of the planar waveguide and propagates in the waveguide. So the size of corresponding optical element could be very small in the vertical direction, which can reduce the size of the optical system. And the performance of the spectrometer is still good. The design method of the planar waveguide spectrometer can be separated into two parts, Czerny-Turner structure design and planar waveguide structure design. First, by using aberration theory an aberration-corrected (spherical aberration, coma, focal curve) Czerny-Turner structure is obtained. The operation wavelength range and spectral resolution are also fixed. Then, by using geometrical optics theory a planar waveguide structure is designed for reducing the system size and correcting the astigmatism. The planar waveguide structure includes a planar waveguide and two cylindrical lenses. Finally, they are modeled together in optical design software and are optimized as a whole. An infrared planar waveguide spectrometer is designed using this method. The operation wavelength range is 8 - 12 μm, the numerical aperture is 0.22, and the linear array detector contains 64 elements. By using Zemax software, the design is optimized and analyzed. The results indicate that the size of the optical system is 130 mm x 125 mm x 20 mm and the spectral resolution of spectrometer is 80 nm, which satisfy the requirements of design index. Thus it is this method that can be used for designing a miniature spectrometer without movable parts and sizes in the range of several cubic centimeters.

Multi-pass light amplifier

NASA Technical Reports Server (NTRS)

Plaessmann, Henry (Inventor); Grossman, William M. (Inventor); Olson, Todd E. (Inventor)

1996-01-01

A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. A second embodiment uses two curvilinear mirrors and one planar mirror, with a gain medium positioned in the optical path between each curvilinear mirror and the planar mirror. A third embodiment uses two curvilinear mirrors and two planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses a curvilinear mirror and three planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses four planar mirrors and a focusing lens system, with a gain medium positioned between the four mirrors. A fifth embodiment uses first and second planar mirrors, a focusing lens system and a third mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the third mirror. A sixth embodiment uses two planar mirrors and a curvilinear mirror and a fourth mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the fourth mirror. In a seventh embodiment, first and second mirrors face a third mirror, all curvilinear, in a White Cell configuration, and a gain medium is positioned adjacent to one of the mirrors.

SPECT/CT in patients with lower back pain after lumbar fusion surgery.

PubMed

Sumer, Johannes; Schmidt, Daniela; Ritt, Philipp; Lell, Michael; Forst, Raimund; Kuwert, Torsten; Richter, Richard

2013-10-01

The aim of the study was to investigate the incremental diagnostic value of skeletal hybrid imaging with single-photon emission computed tomography and X-ray computed tomography (SPECT/CT) over conventional nuclear medical imaging in patients with lower back pain after lumbar fusion surgery (LFS). This retrospective study comprised 37 patients suffering from lower back pain after LFS in whom three-phase planar bone scintigraphies of the lumbar spine including SPECT/CT of that region had been performed. The findings visible on these imaging data sets were classified into the following five diagnostic categories: (a) metal loosening; (b) insufficient stabilizing function of the metal implants indicated by metabolically active facet joint arthritis and/or intervertebral osteochondrosis in the instrumented region; (c) adjacent instability defined as metabolically active degenerative disease in the segments adjacent to the instrumented region; (d) indeterminate; and (e) normal. In the case of eight patients no lesions were visible on their planar scintigraphy and SPECT (planar/SPECT) or SPECT/CT images. In the remaining 29 patients, planar/SPECT disclosed 62 pathological foci of uptake within the graft region and SPECT/CT revealed 55. The rate of reclassification by SPECT/CT compared with planar/SPECT was 5/12 for lesions categorized as metal loosening by planar/SPECT, 16/29 for foci with a planar/SPECT diagnosis of insufficient stabilizing function, 7/20 when the planar/SPECT diagnosis had been adjacent instability, and 1/1 for the lesions indeterminate on planar/SPECT. Two lesions had been detected on SPECT/CT only. The overall rate of reclassification was 45.2% (28/62) (95% confidence interval, 33.4-57.5%). Because of its significantly higher accuracy compared with planar/SPECT, SPECT/CT should be the conventional nuclear medical procedure of choice for patients with lower back pain after LFS.

A flexible, planar energy harvesting device for scavenging road side waste mechanical energy via the synergistic piezoelectric response of K0.5Na0.5NbO3-BaTiO3/PVDF composite films.

PubMed

Vivekananthan, Venkateswaran; Alluri, Nagamalleswara Rao; Purusothaman, Yuvasree; Chandrasekhar, Arunkumar; Kim, Sang-Jae

2017-10-12

Flexible, planar composite piezoelectric nanogenerators (C-PNGs) were developed to harness waste mechanical energy using cost-effective composite films (CFs) prepared via a probe-sonication technique. CFs, made up of highly crystalline, randomly oriented lead free piezoelectric nanoparticles (1 - x)K 0.5 Na 0.5 NbO 3 -xBaTiO 3 , where x = 0.02, 0.04, 0.06, or 0.08 [designated as KNN-xBTO], were impregnated in a polyvinylidene fluoride (PVDF) matrix. The KNN piezoelectric properties were tuned via the substitution of BTO nanoparticles, without altering the orthorhombic phase. A C-PNG device (x ≈ 0.02) generates a maximum open circuit voltage ≈160 V, and the instantaneous area power density is ≈14 mW m -2 upon a low mechanical force ≈0.4 N. The effects of BTO concentration in the KNN lattice, electrical poling effects, the fixed weight ratio of nanoparticles in the PVDF matrix, switching polarity tests, and load resistance analysis of C-PNG devices were investigated with constant mechanical force. Furthermore, the experimentally demonstrated C-PNG device output is sufficient to drive commercial blue light emitting diodes. The C-PNG device was placed on a road side, and the maximum energy generation and stability under real time harsh conditions, such as vehicle motion (motorcycle and bicycle) and human walking, were tested. C-PNG generates a peak-to-peak output voltage ≈16 V, when motorcycle forward/backward motion acts on it. This result indicates that the C-PNG device is a potential candidate to power road side sensors, speed tachometers, light indicators, etc. on highways.

Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity

PubMed Central

Kiefer, Christian S.; Claes, Andrea R.; Nzayisenga, Jean-Claude; Pietra, Stefano; Stanislas, Thomas; Hüser, Anke; Ikeda, Yoshihisa; Grebe, Markus

2015-01-01

The coordination of cell polarity within the plane of the tissue layer (planar polarity) is crucial for the development of diverse multicellular organisms. Small Rac/Rho-family GTPases and the actin cytoskeleton contribute to planar polarity formation at sites of polarity establishment in animals and plants. Yet, upstream pathways coordinating planar polarity differ strikingly between kingdoms. In the root of Arabidopsis thaliana, a concentration gradient of the phytohormone auxin coordinates polar recruitment of Rho-of-plant (ROP) to sites of polar epidermal hair initiation. However, little is known about cytoskeletal components and interactions that contribute to this planar polarity or about their relation to the patterning machinery. Here, we show that ACTIN7 (ACT7) represents a main actin isoform required for planar polarity of root hair positioning, interacting with the negative modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2). ACT7, AIP1-2 and their genetic interaction are required for coordinated planar polarity of ROP downstream of ethylene signalling. Strikingly, AIP1-2 displays hair cell file-enriched expression, restricted by WEREWOLF (WER)-dependent patterning and modified by ethylene and auxin action. Hence, our findings reveal AIP1-2, expressed under control of the WER-dependent patterning machinery and the ethylene signalling pathway, as a modulator of actin-mediated planar polarity. PMID:25428588

Power spectrum and non-Gaussianities in anisotropic inflation

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

Dey, Anindya; Kovetz, Ely D.; Paban, Sonia, E-mail: anindya@physics.utexas.edu, E-mail: elykovetz@gmail.com, E-mail: paban@physics.utexas.edu

2014-06-01

We study the planar regime of curvature perturbations for single field inflationary models in an axially symmetric Bianchi I background. In a theory with standard scalar field action, the power spectrum for such modes has a pole as the planarity parameter goes to zero. We show that constraints from back reaction lead to a strong lower bound on the planarity parameter for high-momentum planar modes and use this bound to calculate the signal-to-noise ratio of the anisotropic power spectrum in the CMB, which in turn places an upper bound on the Hubble scale during inflation allowed in our model. Wemore » find that non-Gaussianities for these planar modes are enhanced for the flattened triangle and the squeezed triangle configurations, but show that the estimated values of the f{sub NL} parameters remain well below the experimental bounds from the CMB for generic planar modes (other, more promising signatures are also discussed). For a standard action, f{sub NL} from the squeezed configuration turns out to be larger compared to that from the flattened triangle configuration in the planar regime. However, in a theory with higher derivative operators, non-Gaussianities from the flattened triangle can become larger than the squeezed configuration in a certain limit of the planarity parameter.« less

Core shroud corner joints

DOEpatents

Gilmore, Charles B.; Forsyth, David R.

2013-09-10

A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.

Direct Bandgap Group IV Materials

DTIC Science & Technology

2016-01-21

devices. In this project, we have accomplished (a) direct bandgap group IV materials of GeSn, (b) GeSn-based planar light - emitting diode operated at near...devices of planar light emitting diode , detector and laser ” 6/12/2015 PI and Co-PI information: - Name of Principal Investigators: Prof. H. H. Cheng...IV materials of GeSn, (b) GeSn-based planar light - emitting diode operated at near infrared with direct emission, and (c) the first planar

Liftings and stresses for planar periodic frameworks

PubMed Central

Borcea, Ciprian; Streinu, Ileana

2015-01-01

We formulate and prove a periodic analog of Maxwell’s theorem relating stressed planar frameworks and their liftings to polyhedral surfaces with spherical topology. We use our lifting theorem to prove deformation and rigidity-theoretic properties for planar periodic pseudo-triangulations, generalizing features known for their finite counterparts. These properties are then applied to questions originating in mathematical crystallography and materials science, concerning planar periodic auxetic structures and ultrarigid periodic frameworks. PMID:26973370

Unsplit bipolar pulse forming line

DOEpatents

Rhodes, Mark A [Pleasanton, CA

2011-05-24

A bipolar pulse forming transmission line module and system for linear induction accelerators having first, second, third, and fourth planar conductors which form a sequentially arranged interleaved stack having opposing first and second ends, with dielectric layers between the conductors. The first and second planar conductors are connected to each other at the first end, and the first and fourth planar conductors are connected to each other at the second end via a shorting plate. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short at the first end a high voltage from the third planar conductor to the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

Interface Characteristics and the Mechanical Properties of Metal Matrix Composites.

DTIC Science & Technology

1987-09-28

of Composites ’" 18 Appendix B Interfaces in Aluminum Metal Matrix Composites g 28 Appendix C Interface Failure in Planar Aluminum-Graphite Composites...Appendix G Residual Stresses in Composite Materials: An Overview of Measurements Used 92 Appendix H Raman Microprobe Measurements of Residual Stresses at...In addition .. to this direct electrostatic attraction, the space charge establishes an electric field of 2 S.. % ° °° % " ° " g

Characterizing hydrophobicity of amino acid side chains in a protein environment via measuring contact angle of a water nanodroplet on planar peptide network

PubMed Central

Zhu, Chongqin; Gao, Yurui; Li, Hui; Meng, Sheng; Li, Lei; Francisco, Joseph S.; Zeng, Xiao Cheng

2016-01-01

Hydrophobicity of macroscopic planar surface is conventionally characterized by the contact angle of water droplets. However, this engineering measurement cannot be directly extended to surfaces of proteins, due to the nanometer scale of amino acids and inherent nonplanar structures. To measure the hydrophobicity of side chains of proteins quantitatively, numerous parameters were developed to characterize behavior of hydrophobic solvation. However, consistency among these parameters is not always apparent. Herein, we demonstrate an alternative way of characterizing hydrophobicity of amino acid side chains in a protein environment by constructing a monolayer of amino acids (i.e., artificial planar peptide network) according to the primary and the β-sheet secondary structures of protein so that the conventional engineering measurement of the contact angle of a water droplet can be brought to bear. Using molecular dynamics simulations, contact angles θ of a water nanodroplet on the planar peptide network, together with excess chemical potentials of purely repulsive methane-sized Weeks−Chandler−Andersen solute, are computed. All of the 20 types of amino acids and the corresponding planar peptide networks are studied. Expectedly, all of the planar peptide networks with nonpolar amino acids are hydrophobic due to θ > 90°, whereas all of the planar peptide networks of the polar and charged amino acids are hydrophilic due to θ < 90°. Planar peptide networks of the charged amino acids exhibit complete-wetting behavior due to θ = 0°. This computational approach for characterization of hydrophobicity can be extended to artificial planar networks of other soft matter. PMID:27803319

Semi-metallic Be5C2 monolayer global minimum with quasi-planar pentacoordinate carbons and negative Poisson's ratio.

PubMed

Wang, Yu; Li, Feng; Li, Yafei; Chen, Zhongfang

2016-05-03

Designing new materials with novel topological properties and reduced dimensionality is always desirable for material innovation. Here we report the design of a two-dimensional material, namely Be5C2 monolayer on the basis of density functional theory computations. In Be5C2 monolayer, each carbon atom binds with five beryllium atoms in almost the same plane, forming a quasi-planar pentacoordinate carbon moiety. Be5C2 monolayer appears to have good stability as revealed by its moderate cohesive energy, positive phonon modes and high melting point. It is the lowest-energy structure with the Be5C2 stoichiometry in two-dimensional space and therefore holds some promise to be realized experimentally. Be5C2 monolayer is a gapless semiconductor with a Dirac-like point in the band structure and also has an unusual negative Poisson's ratio. If synthesized, Be5C2 monolayer may find applications in electronics and mechanics.

Highly flexible, all solid-state micro-supercapacitors from vertically aligned carbon nanotubes.

PubMed

Hsia, Ben; Marschewski, Julian; Wang, Shuang; In, Jung Bin; Carraro, Carlo; Poulikakos, Dimos; Grigoropoulos, Costas P; Maboudian, Roya

2014-02-07

We report a highly flexible planar micro-supercapacitor with interdigitated finger electrodes of vertically aligned carbon nanotubes (VACNTs). The planar electrode structures are patterned on a thin polycarbonate substrate with a facile, maskless laser-assisted dry transfer method. Sputtered Ni is used to reduce the in-plane resistance of the VACNT electrodes. An ionogel, an ionic liquid in a semi-solid matrix, is used as an electrolyte to form a fully solid-state device. We measure a specific capacitance of 430 μF cm(-2) for a scan rate of 0.1 V s(-1) and achieve rectangular cyclic voltammograms at high scan rates of up to 100 V s(-1). Minimal change in capacitance is observed under bending. Mechanical fatigue tests with more than 1000 cycles confirm the high flexibility and durability of the novel material combination chosen for this device. Our results indicate that this scalable and facile fabrication technique shows promise for application in integrated energy storage for all solid-state flexible microdevices.

Fusion of single proteoliposomes with planar, cushioned bilayers in microfluidic flow cells

PubMed Central

Karatekin, Erdem; Rothman, James E.

2013-01-01

Many biological processes rely on membrane fusion, therefore assays to study its mechanisms are necessary. Here we report an assay with sensitivity to single-vesicle, even to single-molecule events using fluorescently labeled vesicle-associated v-SNARE liposomes and target-membrane-associated t-SNARE-reconstituted planar, supported bilayers (SBLs). Docking and fusion events can be detected using conventional far-field epifluorescence or total internal reflection fluorsecence microscopy. Unlike most previous attempts, fusion here is dependent on SNAP25, one of the t-SNARE subunits that is required for fusion in vivo. The success of the assay is due to the use of (i) bilayers covered with a thin layer of poly(ethylene glycol) to control bilayer-bilayer and bilayer-substrate interactions, (ii) microfluidic flow channels which presents many advantages such as the removal of non-specifically bound liposomes by flow. The protocol takes 6–8 days to complete. Analysis can take up to two weeks. PMID:22517259

Passively aligned multichannel fiber-pigtailing of planar integrated optical waveguides

NASA Astrophysics Data System (ADS)

Kremmel, Johannes; Lamprecht, Tobias; Crameri, Nino; Michler, Markus

2017-02-01

A silicon device to simplify the coupling of multiple single-mode fibers to embedded single-mode waveguides has been developed. The silicon device features alignment structures that enable a passive alignment of fibers to integrated waveguides. For passive alignment, precisely machined V-grooves on a silicon device are used and the planar lightwave circuit board features high-precision structures acting as a mechanical stop. The approach has been tested for up to eight fiber-to-waveguide connections. The alignment approach, the design, and the fabrication of the silicon device as well as the assembly process are presented. The characterization of the fiber-to-waveguide link reveals total coupling losses of (0.45±0.20 dB) per coupling interface, which is significantly lower than the values reported in earlier works. Subsequent climate tests reveal that the coupling losses remain stable during thermal cycling but increases significantly during an 85°C/85 Rh-test. All applied fabrication and bonding steps have been performed using standard MOEMS fabrication and packaging processes.

Planar cell polarity signaling coordinates oriented cell division and cell rearrangement in clonally expanding growth plate cartilage.

PubMed

Li, Yuwei; Li, Ang; Junge, Jason; Bronner, Marianne

2017-10-10

Both oriented cell divisions and cell rearrangements are critical for proper embryogenesis and organogenesis. However, little is known about how these two cellular events are integrated. Here we examine the linkage between these processes in chick limb cartilage. By combining retroviral-based multicolor clonal analysis with live imaging, the results show that single chondrocyte precursors can generate both single-column and multi-column clones through oriented division followed by cell rearrangements. Focusing on single column formation, we show that this stereotypical tissue architecture is established by a pivot-like process between sister cells. After mediolateral cell division, N-cadherin is enriched in the post-cleavage furrow; then one cell pivots around the other, resulting in stacking into a column. Perturbation analyses demonstrate that planar cell polarity signaling enables cells to pivot in the direction of limb elongation via this N-cadherin-mediated coupling. Our work provides new insights into the mechanisms generating appropriate tissue architecture of limb skeleton.

Study of flow stress and spall strength of additively manufactured Ti-6-4 alloy

NASA Astrophysics Data System (ADS)

Cohen, Amitay; Paris, Vitaly; Yosef-Hai, Arnon; Gudinetsky, Eli; Tiferet, Eitan

2017-06-01

The use of additive manufacturing (AM) by Electron Beam Melting (EBM) or Selective Laser Melting (SLM) has extensively grown in the past few years. A major goal in AM is to manufacture materials with mechanical properties at least as good as traditionally manufactured materials. In this work we present results of planar impact tests and Split Hopkinson Pressure Bar tests (SHPB) on Ti-6-4 manufactured by EBM and SLM processes. Results of planar impact tests on SLM samples display slightly higher spall strength compared to EBM while the stress at Hugoniot elastic limit (HEL) is practically the same. Stress strain curves based on SHPB measurements at two different strain rates present similar plastic flow stresses for SLM and EBM processed Ti-6-4 alloy, while the flow stress is about 20% higher than reported for commercial reference material. The strain to failure of both materials shows considerable strain rate sensitivity. The results of post-mortem analysis of spall fracture will also be presented.

Chemical potential in active systems: predicting phase equilibrium from bulk equations of state?

NASA Astrophysics Data System (ADS)

Paliwal, Siddharth; Rodenburg, Jeroen; van Roij, René; Dijkstra, Marjolein

2018-01-01

We derive a microscopic expression for a quantity μ that plays the role of chemical potential of active Brownian particles (ABPs) in a steady state in the absence of vortices. We show that μ consists of (i) an intrinsic chemical potential similar to passive systems, which depends on density and self-propulsion speed, but not on the external potential, (ii) the external potential, and (iii) a newly derived one-body swim potential due to the activity of the particles. Our simulations on ABPs show good agreement with our Fokker-Planck calculations, and confirm that μ (z) is spatially constant for several inhomogeneous active fluids in their steady states in a planar geometry. Finally, we show that phase coexistence of ABPs with a planar interface satisfies not only mechanical but also diffusive equilibrium. The coexistence can be well-described by equating the bulk chemical potential and bulk pressure obtained from bulk simulations for systems with low activity but requires explicit evaluation of the interfacial contributions at high activity.

Planar cell polarity signaling coordinates oriented cell division and cell rearrangement in clonally expanding growth plate cartilage

PubMed Central

Li, Yuwei; Li, Ang; Junge, Jason

2017-01-01

Both oriented cell divisions and cell rearrangements are critical for proper embryogenesis and organogenesis. However, little is known about how these two cellular events are integrated. Here we examine the linkage between these processes in chick limb cartilage. By combining retroviral-based multicolor clonal analysis with live imaging, the results show that single chondrocyte precursors can generate both single-column and multi-column clones through oriented division followed by cell rearrangements. Focusing on single column formation, we show that this stereotypical tissue architecture is established by a pivot-like process between sister cells. After mediolateral cell division, N-cadherin is enriched in the post-cleavage furrow; then one cell pivots around the other, resulting in stacking into a column. Perturbation analyses demonstrate that planar cell polarity signaling enables cells to pivot in the direction of limb elongation via this N-cadherin-mediated coupling. Our work provides new insights into the mechanisms generating appropriate tissue architecture of limb skeleton. PMID:28994649

Assembly and positioning of actomyosin rings by contractility and planar cell polarity

PubMed Central

Sehring, Ivonne M; Recho, Pierre; Denker, Elsa; Kourakis, Matthew; Mathiesen, Birthe; Hannezo, Edouard; Dong, Bo; Jiang, Di

2015-01-01

The actomyosin cytoskeleton is a primary force-generating mechanism in morphogenesis, thus a robust spatial control of cytoskeletal positioning is essential. In this report, we demonstrate that actomyosin contractility and planar cell polarity (PCP) interact in post-mitotic Ciona notochord cells to self-assemble and reposition actomyosin rings, which play an essential role for cell elongation. Intriguingly, rings always form at the cells′ anterior edge before migrating towards the center as contractility increases, reflecting a novel dynamical property of the cortex. Our drug and genetic manipulations uncover a tug-of-war between contractility, which localizes cortical flows toward the equator and PCP, which tries to reposition them. We develop a simple model of the physical forces underlying this tug-of-war, which quantitatively reproduces our results. We thus propose a quantitative framework for dissecting the relative contribution of contractility and PCP to the self-assembly and repositioning of cytoskeletal structures, which should be applicable to other morphogenetic events. DOI: http://dx.doi.org/10.7554/eLife.09206.001 PMID:26486861

Immunosensing by luminescence reduction in surface-modified microstructured SU-8

NASA Astrophysics Data System (ADS)

Eravuchira, Pinkie Jacob; Baranowska, Malgorzata; Eckstein, Chris; Díaz, Francesc; Llobet, Eduard; Marsal, Lluis F.; Ferré-Borrull, Josep

2017-01-01

SU-8, an epoxy based negative photoresist is extensively used as a structural material for the fabrication of microelectro-mechanical systems and in microelectronics technology. However, the possible applications of SU-8 for biosensing have not been explored much, mainly because of the photoluminescence SU-8 possesses in the near-UV and visible wavelength ranges which hinders fluorescent labelling of biorecognition events. In this study we demonstrate that photoluminescence of SU-8 can be employed itself as a sensing transduction parameter to produce a tool for immunosensing: the photoluminescence shows a systematic reduction upon modification of its surface chemistry, and in particular upon attachment of an antigen-antibody (aIgG-IgG) pair. We investigate the relation of the amount of reduction of photoluminescence on planar and microstructured surfaces, and we show that microstructuring leads to a higher reduction than a planar surface. Furthermore, we evaluated the dependence of photoluminescence reduction as a function of analyte concentration to prove that this magnitude can be applied to immunosensing.

Black Phosphorus Quantum Dots for Hole Extraction of Typical Planar Hybrid Perovskite Solar Cells.

PubMed

Chen, Wei; Li, Kaiwen; Wang, Yao; Feng, Xiyuan; Liao, Zhenwu; Su, Qicong; Lin, Xinnan; He, Zhubing

2017-02-02

Black phosphorus, famous as two-dimensional (2D) materials, shows such excellent properties for optoelectronic devices such as tunable direct band gap, extremely high hole mobility (300-1000 cm 2 /(V s)), and so forth. In this Letter, facile processed black phosphorus quantum dots (BPQDs) were successfully applied to enhance hole extraction at the anode side of the typical p-i-n planar hybrid perovskite solar cells, which remarkably improved the performance of devices with photon conversion efficiency ramping up from 14.10 to 16.69%. Moreover, more detailed investigations by c-AFM, SKPM, SEM, hole-only devices, and photon physics measurements discover further the hole extraction effect and work mechanism of the BPQDs, such as nucleation assistance for the growth of large grain size perovskite crystals, fast hole extraction, more efficient hole transfer, and suppression of energy-loss recombination at the anode interface. This work definitely paves the way for discovering more and more 2D materials with high electronic properties to be used in photovoltaics and optoelectronics.

High-performance tandem organic light-emitting diodes based on a buffer-modified p/n-type planar organic heterojunction as charge generation layer

NASA Astrophysics Data System (ADS)

Wu, Yukun; Sun, Ying; Qin, Houyun; Hu, Shoucheng; Wu, Qingyang; Zhao, Yi

2017-04-01

High-performance tandem organic light-emitting diodes (TOLEDs) were realized using a buffer-modified p/n-type planar organic heterojunction (OHJ) as charge generation layer (CGL) consisting of common organic materials, and the configuration of this p/n-type CGL was "LiF/N,N'-diphenyl-N,N'-bis(1-napthyl)-1,1'-biphenyl-4,4'-diamine (NPB)/4,7-diphenyl-1,10-phenanthroline (Bphen)/molybdenum oxide (MoOx)". The optimized TOLED exhibited a maximum current efficiency of 77.6 cd/A without any out-coupling techniques, and the efficiency roll-off was greatly improved compared to the single-unit OLED. The working mechanism of the p/n-type CGL was discussed in detail. It is found that the NPB/Bphen heterojunction generated enough charges under a forward applied voltage and the carrier extraction was a tunneling process. These results could provide a new method to fabricate high-performance TOLEDs.

Unusual ion UO(4)(-) formed upon collision induced dissociation of [UO(2)(NO(3))(3)](-), [UO(2)(ClO(4))(3)](-), [UO(2)(CH(3)COO)(3)](-) ions.

PubMed

Sokalska, Marzena; Prussakowska, Małgorzata; Hoffmann, Marcin; Gierczyk, Błazej; Frański, Rafał

2010-10-01

The following ions [UO(2)(NO(3))(3)](-), [UO(2)(ClO(4))(3)](-), [UO(2)(CH(3)COO)(3)](-) were generated from respective salts (UO(2)(NO(3))(2), UO(2)(ClO(4))(3), UO(2)(CH(3)COO)(2)) by laser desorption/ionization (LDI). Collision induced dissociation of the ions has led, among others, to the formation of UO(4)(-) ion (m/z 302). The undertaken quantum mechanical calculations showed this ion is most likely to possess square planar geometry as suggested by MP2 results or strongly deformed geometry in between tetrahedral and square planar as indicated by DFT results. Interestingly, geometrical parameters and analysis of electron density suggest it is an U(VI) compound, in which oxygen atoms bear unpaired electron and negative charge. Copyright © 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

Chitosan-Assisted Crystallization and Film Forming of Perovskite Crystals through Biomineralization.

PubMed

Yang, Yang; Sun, Chen; Yip, Hin-Lap; Sun, Runcang; Wang, Xiaohui

2016-03-18

Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical suitability of glycerol-preserved human dura mater for construction of prosthetic cardiac valves.

PubMed

McGarvey, K A; Lee, J M; Boughner, D R

1984-03-01

We have examined the tensile viscoelastic properties of fresh and glycerol-preserved human dura mater, and correlated the results with structural information from the scanning electron microscope. The interwoven laminar structure of dura produces rather high flexural stiffness, while the crossed-fibrillar laminae produce planar mechanical isotropy. Glycerol storage shifts the stress-strain curve to lower strain, reduces stress relaxation and creep, and lowers the ultimate tensile strength and strain at fracture. These changes may be due to glyceraldehyde crosslinking, or to increased interfibrillar friction. The latter hypothesis suggests that glycerol storage may reduce the fatigue lifetime of the tissue.

Three sets of crystallographic sub-planar structures in quartz formed by tectonic deformation

NASA Astrophysics Data System (ADS)

Derez, Tine; Pennock, Gill; Drury, Martyn; Sintubin, Manuel

2016-05-01

In quartz, multiple sets of fine planar deformation microstructures that have specific crystallographic orientations parallel to planes with low Miller-Bravais indices are commonly considered as shock-induced planar deformation features (PDFs) diagnostic of shock metamorphism. Using polarized light microscopy, we demonstrate that up to three sets of tectonically induced sub-planar fine extinction bands (FEBs), sub-parallel to the basal, γ, ω, and π crystallographic planes, are common in vein quartz in low-grade tectonometamorphic settings. We conclude that the observation of multiple (2-3) sets of fine scale, closely spaced, crystallographically controlled, sub-planar microstructures is not sufficient to unambiguously distinguish PDFs from tectonic FEBs.

Ultrathin two-dimensional MnO2/graphene hybrid nanostructures for high-performance, flexible planar supercapacitors.

PubMed

Peng, Lele; Peng, Xu; Liu, Borui; Wu, Changzheng; Xie, Yi; Yu, Guihua

2013-05-08

Planar supercapacitors have recently attracted much attention owing to their unique and advantageous design for 2D nanomaterials based energy storage devices. However, improving the electrochemical performance of planar supercapacitors still remains a great challenge. Here we report for the first time a novel, high-performance in-plane supercapacitor based on hybrid nanostructures of quasi-2D ultrathin MnO2/graphene nanosheets. Specifically, the planar structures based on the δ-MnO2 nanosheets integrated on graphene sheets not only introduce more electrochemically active surfaces for absorption/desorption of electrolyte ions, but also bring additional interfaces at the hybridized interlayer areas to facilitate charge transport during charging/discharging processes. The unique structural design for planar supercapacitors enables great performance enhancements compared to graphene-only devices, exhibiting high specific capacitances of 267 F/g at current density of 0.2 A/g and 208 F/g at 10 A/g and excellent rate capability and cycling stability with capacitance retention of 92% after 7000 charge/discharge cycles. Moreover, the high planar malleability of planar supercapacitors makes possible superior flexibility and robust cyclability, yielding capacitance retention over 90% after 1000 times of folding/unfolding. Ultrathin 2D nanomaterials represent a promising material platform to realize highly flexible planar energy storage devices as the power back-ups for stretchable/flexible electronic devices.

Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity.

PubMed

Kiefer, Christian S; Claes, Andrea R; Nzayisenga, Jean-Claude; Pietra, Stefano; Stanislas, Thomas; Hüser, Anke; Ikeda, Yoshihisa; Grebe, Markus

2015-01-01

The coordination of cell polarity within the plane of the tissue layer (planar polarity) is crucial for the development of diverse multicellular organisms. Small Rac/Rho-family GTPases and the actin cytoskeleton contribute to planar polarity formation at sites of polarity establishment in animals and plants. Yet, upstream pathways coordinating planar polarity differ strikingly between kingdoms. In the root of Arabidopsis thaliana, a concentration gradient of the phytohormone auxin coordinates polar recruitment of Rho-of-plant (ROP) to sites of polar epidermal hair initiation. However, little is known about cytoskeletal components and interactions that contribute to this planar polarity or about their relation to the patterning machinery. Here, we show that ACTIN7 (ACT7) represents a main actin isoform required for planar polarity of root hair positioning, interacting with the negative modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2). ACT7, AIP1-2 and their genetic interaction are required for coordinated planar polarity of ROP downstream of ethylene signalling. Strikingly, AIP1-2 displays hair cell file-enriched expression, restricted by WEREWOLF (WER)-dependent patterning and modified by ethylene and auxin action. Hence, our findings reveal AIP1-2, expressed under control of the WER-dependent patterning machinery and the ethylene signalling pathway, as a modulator of actin-mediated planar polarity. © 2015. Published by The Company of Biologists Ltd.

"Finite part" electric and magnetic stored energies for planar antennas

NASA Technical Reports Server (NTRS)

Cockrell, C. R.

1981-01-01

A pair of formulas representing the time-average "finite part" electric and magnetic stored energies for planar antennas are derived. It is also shown that the asymptotic reciprocal relationship between quality factor and relative bandwidth exists for planar antennas.

Discernment of Possible Organic Magnetic Field Effect Mechanisms Using Polymer Light-Emitting Electrochemical Cells

NASA Astrophysics Data System (ADS)

Geng, R.; Subedi, R. C.; Liang, S.; Nguyen, T. D.

2014-07-01

We report studies of magnetic field effect (MFE) in polymer light-emitting electrochemical cells (PLEC) using the "super-yellow" poly-(phenylene vynilene) (SY-PPV) polymer in vertical and planar device configurations. The purpose is to discern the existing MFE mechanisms in organic light emitting diodes (OLEDs) where the current and electroluminescence are strongly modulated by a small applied magnetic field. In particular, we investigate the mutual relationship between magneto-conductance (MC) and magneto-electroluminescence (MEL) by studying the role of polaron density dissociated from polaron pairs (PP) on these magnetic responses. In general, the dissociated polaron density is determined by the PP dissociation rate and the PP density. For the planar PLEC, which possesses a small dissociation rate, we observe small and negative MC at all applied voltages regardless of the emission intensity, while MEL becomes positive when electroluminescence quantum efficiency increases. The MC has a much narrower width than the MEL, indicating that the MC and MEL do not share a common origin. However, MC reverses and has the same width as MEL when the device is exposed to a threshold laser power. For the vertical PLEC, characterized by a large dissociation rate, MC and MEL are positive and have the same width. We discuss the results using the existing MFE mechanism in OLEDs. We show that the PP model can explain the positive MEL and MC, while the negative MC can be explained by the bipolaron model. Finally, we present a possibility to complete an all-organic PLEC magnetic sensor by using an inkjet printer.

Radiation sources with planar wire arrays and planar foils for inertial confinement fusion and high energy density physics research

NASA Astrophysics Data System (ADS)

Kantsyrev, V. L.; Chuvatin, A. S.; Safronova, A. S.; Rudakov, L. I.; Esaulov, A. A.; Velikovich, A. L.; Shrestha, I.; Astanovitsky, A.; Osborne, G. C.; Shlyaptseva, V. V.; Weller, M. E.; Keim, S.; Stafford, A.; Cooper, M.

2014-03-01

This article reports on the joint success of two independent lines of research, each of them being a multi-year international effort. One of these is the development of innovative sources, such as planar wire arrays (PWAs). PWAs turned out to be a prolific radiator, which act mainly as a resistor, even though the physical mechanism of efficient magnetic energy conversion into radiation still remains unclear. We review the results of our extensive studies of PWAs. We also report the new results of the experimental comparison PWAs with planar foil liners (another promising alternative to wire array loads at multi-mega-ampere generators). Pioneered at UNR, the PWA Z-pinch loads have later been tested at the Sandia National Laboratories (SNL) on the Saturn generator, on GIT-12 machine in Russia, and on the QiangGuang-1 generator in China, always successfully. Another of these is the drastic improvement in energy efficiency of pulsed-power systems, which started in early 1980s with Zucker's experiments at Naval Research Laboratory (NRL). Successful continuation of this approach was the Load Current Multiplier (LCM) proposed by Chuvatin in collaboration with Rudakov and Weber from NRL. The 100 ns LCM was integrated into the Zebra generator, which almost doubled the plasma load current, from 0.9 to 1.7 MA. The two above-mentioned innovative approaches were used in combination to produce a new compact hohlraum radiation source for ICF, as jointly proposed by SNL and UNR [Jones et al., Phys. Rev. Lett. 104, 125001 (2010)]. The first successful proof-of-the-principle experimental implementation of new hohlraum concept at university-scale generator Zebra/LCM is demonstrated. A numerical simulation capability with VisRaD code (from PRISM Co.) established at UNR allowed for the study of hohlraum coupling physics and provides the possibility of optimization of a new hohlraum. Future studies are discussed.

Excited-State Conformational/Electronic Responses of Saddle-Shaped N,N'-Disubstituted-Dihydrodibenzo[a,c]phenazines: Wide-Tuning Emission from Red to Deep Blue and White Light Combination.

PubMed

Zhang, Zhiyun; Wu, Yu-Sin; Tang, Kuo-Chun; Chen, Chi-Lin; Ho, Jr-Wei; Su, Jianhua; Tian, He; Chou, Pi-Tai

2015-07-08

A tailored strategy is utilized to modify 5,10-dimethylphenazine (DMP) to donor-acceptor type N,N'-disubstituted-dihydrodibenzo[a,c]phenazines. The representative compounds DMAC (N,N'-dimethyl), DPAC (N,N'-diphenyl), and FlPAC (N-phenyl-N'-fluorenyl) reveal significant nonplanar distortions (i.e., a saddle shape) and remarkably large Stokes-shifted emission independent of the solvent polarity. For DPAC and FlPAC with higher steric hindrance on the N,N'-substituents, normal Stokes-shifted emission also appears, for which the peak wavelength reveals solvent-polarity dependence. These unique photophysical behaviors are rationalized by electronic configuration coupled conformation changes en route to the geometry planarization in the excited state. This proposed mechanism is different from the symmetry rule imposed to explain the anomalously long-wavelength emission for DMP and is firmly supported by polarity-, viscosity-, and temperature-dependent steady-state and nanosecond time-resolved spectroscopy. Together with femtosecond early dynamics and computational simulation of the reaction energy surfaces, the results lead us to establish a sequential, three-step kinetics. Upon electronic excitation of N,N'-disubstituted-dihydrodibenzo[a,c]phenazines, intramolecular charge-transfer takes place, followed by the combination of polarization stabilization and skeletal motion toward the planarization, i.e., elongation of the π-delocalization over the benzo[a,c]phenazines moiety. Along the planarization, DPAC and FlPAC encounter steric hindrance raised by the N,N'-disubstitutes, resulting in a local minimum state, i.e., the intermediate. The combination of initial charge-transfer state, intermediate, and the final planarization state renders the full spectrum of interest and significance in their anomalous photophysics. Depending on rigidity, the N,N'-disubstituted-dihydrodibenzo[a,c]phenazines exhibit multiple emissions, which can be widely tuned from red to deep blue and even to white light generation upon optimization of the surrounding media.

Transfer-Efficient Face Routing Using the Planar Graphs of Neighbors in High Density WSNs

PubMed Central

Kim, Sang-Ha

2017-01-01

Face routing has been adopted in wireless sensor networks (WSNs) where topological changes occur frequently or maintaining full network information is difficult. For message forwarding in networks, a planar graph is used to prevent looping, and because long edges are removed by planarization and the resulting planar graph is composed of short edges, and messages are forwarded along multiple nodes connected by them even though they can be forwarded directly. To solve this, face routing using information on all nodes within 2-hop range was adopted to forward messages directly to the farthest node within radio range. However, as the density of the nodes increases, network performance plunges because message transfer nodes receive and process increased node information. To deal with this problem, we propose a new face routing using the planar graphs of neighboring nodes to improve transfer efficiency. It forwards a message directly to the farthest neighbor and reduces loads and processing time by distributing network graph construction and planarization to the neighbors. It also decreases the amount of location information to be transmitted by sending information on the planar graph nodes rather than on all neighboring nodes. Simulation results show that it significantly improves transfer efficiency. PMID:29053623

Planar xanthomas secondary to post-transplantation cholangiopathy in a 16-month-old boy.

PubMed

Patel, Nirali; Norberg, Adam; Hogeling, Marcia

2018-05-01

Planar xanthomas in children represent rare dermatologic findings associated with abnormalities in lipid metabolism. While planar xanthomas in Alagille's syndrome have been well described in the literature, there have been no cases reported of eruptive xanthomas in pediatric liver transplant patients. Herein we report a case of a 16-month-old boy status post-liver transplantation who presents with planar xanthomas secondary to cholangiopathy. A brief review of xanthomas and the related literature is also provided. © 2018 Wiley Periodicals, Inc.

Resolution of Port/Starboard Ambiguity Using a Linear Array of Triplets and a Twin-Line Planar Array

DTIC Science & Technology

2016-06-01

STARBOARD AMBIGUITY USING A LINEAR ARRAY OF TRIPLETS AND A TWIN- LINE PLANAR ARRAY by Stilson Veras Cardoso June 2016 Thesis Advisor...OF TRIPLETS AND A TWIN-LINE PLANAR ARRAY 5. FUNDING NUMBERS 6. AUTHOR(S) Stilson Veras Cardoso 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES...A LINEAR ARRAY OF TRIPLETS AND A TWIN-LINE PLANAR ARRAY Stilson Veras Cardoso Civilian, Brazilian Navy B.S., University of Brasília, 1993

Hermetic Packages For Millimeter-Wave Circuits

NASA Technical Reports Server (NTRS)

Herman, Martin I.; Lee, Karen A.; Lowry, Lynn E.; Carpenter, Alain; Wamhof, Paul

1994-01-01

Advanced hermetic packages developed to house electronic circuits operating at frequencies from 1 to 100 gigahertz and beyond. Signals coupled into and out of packages electromagnetically. Provides circuit packages small, lightweight, rugged, and inexpensive in mass production. Packages embedded in planar microstrip and coplanar waveguide circuits, in waveguide-to-planar and planar-to-waveguide circuitry, in waveguide-to-waveguide circuitry, between radiating (antenna) elements, and between planar transmission lines and radiating elements. Other applications in automotive, communication, radar, remote sensing, and biomedical electronic systems foreseen.

Thin film hydrogen sensor

DOEpatents

Cheng, Yang-Tse; Poli, Andrea A.; Meltser, Mark Alexander

1999-01-01

A thin film hydrogen sensor, includes: a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end.

Enumeration of spanning trees in planar unclustered networks

NASA Astrophysics Data System (ADS)

Xiao, Yuzhi; Zhao, Haixing; Hu, Guona; Ma, Xiujuan

2014-07-01

Among a variety of subgraphs, spanning trees are one of the most important and fundamental categories. They are relevant to diverse aspects of networks, including reliability, transport, self-organized criticality, loop-erased random walks and so on. In this paper, we introduce a family of modular, self-similar planar networks with zero clustering. Relevant properties of this family are comparable to those networks associated with technological systems having low clustering, like power grids, some electronic circuits, the Internet and some biological systems. So, it is very significant to research on spanning trees of planar networks. However, for a large network, evaluating the relevant determinant is intractable. In this paper, we propose a fairly generic linear algorithm for counting the number of spanning trees of a planar network. Using the algorithm, we derive analytically the exact numbers of spanning trees in planar networks. Our result shows that the computational complexity is O(t) , which is better than that of the matrix tree theorem with O(m2t2) , where t is the number of steps and m is the girth of the planar network. We also obtain the entropy for the spanning trees of a given planar network. We find that the entropy of spanning trees in the studied network is small, which is in sharp contrast to the previous result for planar networks with the same average degree. We also determine an upper bound and a lower bound for the numbers of spanning trees in the family of planar networks by the algorithm. As another application of the algorithm, we give a formula for the number of spanning trees in an outerplanar network with small-world features.

Characterizing hydrophobicity of amino acid side chains in a protein environment via measuring contact angle of a water nanodroplet on planar peptide network.

PubMed

Zhu, Chongqin; Gao, Yurui; Li, Hui; Meng, Sheng; Li, Lei; Francisco, Joseph S; Zeng, Xiao Cheng

2016-11-15

Hydrophobicity of macroscopic planar surface is conventionally characterized by the contact angle of water droplets. However, this engineering measurement cannot be directly extended to surfaces of proteins, due to the nanometer scale of amino acids and inherent nonplanar structures. To measure the hydrophobicity of side chains of proteins quantitatively, numerous parameters were developed to characterize behavior of hydrophobic solvation. However, consistency among these parameters is not always apparent. Herein, we demonstrate an alternative way of characterizing hydrophobicity of amino acid side chains in a protein environment by constructing a monolayer of amino acids (i.e., artificial planar peptide network) according to the primary and the β-sheet secondary structures of protein so that the conventional engineering measurement of the contact angle of a water droplet can be brought to bear. Using molecular dynamics simulations, contact angles θ of a water nanodroplet on the planar peptide network, together with excess chemical potentials of purely repulsive methane-sized Weeks-Chandler-Andersen solute, are computed. All of the 20 types of amino acids and the corresponding planar peptide networks are studied. Expectedly, all of the planar peptide networks with nonpolar amino acids are hydrophobic due to θ [Formula: see text] 90°, whereas all of the planar peptide networks of the polar and charged amino acids are hydrophilic due to θ [Formula: see text] 90°. Planar peptide networks of the charged amino acids exhibit complete-wetting behavior due to θ [Formula: see text] 0°. This computational approach for characterization of hydrophobicity can be extended to artificial planar networks of other soft matter.

Formation and mosaicity of coccolith segment calcite of the marine algae Emiliania huxleyi.

PubMed

Yin, Xiaofei; Ziegler, Andreas; Kelm, Klemens; Hoffmann, Ramona; Watermeyer, Philipp; Alexa, Patrick; Villinger, Clarissa; Rupp, Ulrich; Schlüter, Lothar; Reusch, Thorsten B H; Griesshaber, Erika; Walther, Paul; Schmahl, Wolfgang W

2018-02-01

Coccolithophores belong to the most abundant calcium carbonate mineralizing organisms. Coccolithophore biomineralization is a complex and highly regulated process, resulting in a product that strongly differs in its intricate morphology from the abiogenically produced mineral equivalent. Moreover, unlike extracellularly formed biological carbonate hard tissues, coccolith calcite is neither a hybrid composite, nor is it distinguished by a hierarchical microstructure. This is remarkable as the key to optimizing crystalline biomaterials for mechanical strength and toughness lies in the composite nature of the biological hard tissue and the utilization of specific microstructures. To obtain insight into the pathway of biomineralization of Emiliania huxleyi coccoliths, we examine intracrystalline nanostructural features of the coccolith calcite in combination with cell ultrastructural observations related to the formation of the calcite in the coccolith vesicle within the cell. With TEM diffraction and annular dark-field imaging, we prove the presence of planar imperfections in the calcite crystals such as planar mosaic block boundaries. As only minor misorientations occur, we attribute them to dislocation networks creating small-angle boundaries. Intracrystalline occluded biopolymers are not observed. Hence, in E. huxleyi calcite mosaicity is not caused by occluded biopolymers, as it is the case in extracellularly formed hard tissues of marine invertebrates, but by planar defects and dislocations which are typical for crystals formed by classical ion-by-ion growth mechanisms. Using cryo-preparation techniques for SEM and TEM, we found that the membrane of the coccolith vesicle and the outer membrane of the nuclear envelope are in tight proximity, with a well-controlled constant gap of ~4 nm between them. We describe this conspicuous connection as a not yet described interorganelle junction, the "nuclear envelope junction". The narrow gap of this junction likely facilitates transport of Ca 2+ ions from the nuclear envelope to the coccolith vesicle. On the basis of our observations, we propose that formation of the coccolith utilizes the nuclear envelope-endoplasmic reticulum Ca 2+ -store of the cell for the transport of Ca 2+ ions from the external medium to the coccolith vesicle and that E. huxleyi calcite forms by ion-by-ion growth rather than by a nanoparticle accretion mechanism. © 2017 Phycological Society of America.

Quantifying losses and thermodynamic limits in nanophotonic solar cells

NASA Astrophysics Data System (ADS)

Mann, Sander A.; Oener, Sebastian Z.; Cavalli, Alessandro; Haverkort, Jos E. M.; Bakkers, Erik P. A. M.; Garnett, Erik C.

2016-12-01

Nanophotonic engineering shows great potential for photovoltaics: the record conversion efficiencies of nanowire solar cells are increasing rapidly and the record open-circuit voltages are becoming comparable to the records for planar equivalents. Furthermore, it has been suggested that certain nanophotonic effects can reduce costs and increase efficiencies with respect to planar solar cells. These effects are particularly pronounced in single-nanowire devices, where two out of the three dimensions are subwavelength. Single-nanowire devices thus provide an ideal platform to study how nanophotonics affects photovoltaics. However, for these devices the standard definition of power conversion efficiency no longer applies, because the nanowire can absorb light from an area much larger than its own size. Additionally, the thermodynamic limit on the photovoltage is unknown a priori and may be very different from that of a planar solar cell. This complicates the characterization and optimization of these devices. Here, we analyse an InP single-nanowire solar cell using intrinsic metrics to place its performance on an absolute thermodynamic scale and pinpoint performance loss mechanisms. To determine these metrics we have developed an integrating sphere microscopy set-up that enables simultaneous and spatially resolved quantitative absorption, internal quantum efficiency (IQE) and photoluminescence quantum yield (PLQY) measurements. For our record single-nanowire solar cell, we measure a photocurrent collection efficiency of >90% and an open-circuit voltage of 850 mV, which is 73% of the thermodynamic limit (1.16 V).

Large area thinned planar sensors for future high-luminosity-LHC upgrades

NASA Astrophysics Data System (ADS)

Wittig, T.; Lawerenz, A.; Röder, R.

2016-12-01

Planar hybrid silicon sensors are a well proven technology for past and current particle tracking detectors in HEP experiments. However, the future high-luminosity upgrades of the inner trackers at the LHC experiments pose big challenges to the detectors. A first challenge is an expected radiation damage level of up to 2ṡ 1016 neq/cm2. For planar sensors, one way to counteract the charge loss and thus increase the radiation hardness is to decrease the thickness of their active area. A second challenge is the large detector area which has to be built as cost-efficient as possible. The CiS research institute has accomplished a proof-of-principle run with n-in-p ATLAS-Pixel sensors in which a cavity is etched to the sensor's back side to reduce its thickness. One advantage of this technology is the fact that thick frames remain at the sensor edges and guarantee mechanical stability on wafer level while the sensor is left on the resulting thin membrane. For this cavity etching technique, no handling wafers are required which represents a benefit in terms of process effort and cost savings. The membranes with areas of up to ~ 4 × 4 cm2 and thicknesses of 100 and 150 μm feature a sufficiently good homogeneity across the whole wafer area. The processed pixel sensors show good electrical behaviour with an excellent yield for a suchlike prototype run. First sensors with electroless Ni- and Pt-UBM are already successfully assembled with read-out chips.

Structural Determinants of Improved Fluorescence in a Family of Bacteriophytochrome-Based Infrared Fluorescent Proteins: Insights from Continuum Electrostatic Calculations and Molecular Dynamics Simulations.

PubMed

Feliks, Mikolaj; Lafaye, Céline; Shu, Xiaokun; Royant, Antoine; Field, Martin

2016-08-09

Using X-ray crystallography, continuum electrostatic calculations, and molecular dynamics simulations, we have studied the structure, protonation behavior, and dynamics of the biliverdin chromophore and its molecular environment in a series of genetically engineered infrared fluorescent proteins (IFPs) based on the chromophore-binding domain of the Deinococcus radiodurans bacteriophytochrome. Our study suggests that the experimentally observed enhancement of fluorescent properties results from the improved rigidity and planarity of the biliverdin chromophore, in particular of the first two pyrrole rings neighboring the covalent linkage to the protein. We propose that the increases in the levels of both motion and bending of the chromophore out of planarity favor the decrease in fluorescence. The chromophore-binding pocket in some of the studied proteins, in particular the weakly fluorescent parent protein, is shown to be readily accessible to water molecules from the solvent. These waters entering the chromophore region form hydrogen bond networks that affect the otherwise planar conformation of the first three rings of the chromophore. On the basis of our simulations, the enhancement of fluorescence in IFPs can be achieved either by reducing the mobility of water molecules in the vicinity of the chromophore or by limiting the interactions of the nearby protein residues with the chromophore. Finally, simulations performed at both low and neutral pH values highlight differences in the dynamics of the chromophore and shed light on the mechanism of fluorescence loss at low pH.

Unsteady planar diffusion flames: Ignition, travel, burnout

NASA Technical Reports Server (NTRS)

Fendell, F.; Wu, F.

1995-01-01

In microgravity, a thin planar diffusion flame is created and thenceforth travels so that the flame is situated at all times at an interface at which the hydrogen and oxygen meet in stoichiometric proportion. If the initial amount of hydrogen is deficient relative to the initial amount of oxygen, then the planar flame will travel further and further into the half volume initially containing hydrogen, until the hydrogen is (virtually) fully depleted. Of course, when the amount of residual hydrogen becomes small, the diffusion flame is neither vigorous nor thin; in practice, the flame is extinguished before the hydrogen is fully depleted, owing to the finite rate of the actual chemical-kinetic mechanism. The rate of travel of the hydrogen-air diffusion flame is much slower than the rate of laminar flame propagation through a hydrogen-air mixture. This slow travel facilitates diagnostic detection of the flame position as a function of time, but the slow travel also means that the time to burnout (extinction) probably far exceeds the testing time (typically, a few seconds) available in earth-sited facilities for microgravity-environment experiments. We undertake an analysis to predict (1) the position and temperature of the diffusion flame as a function of time, (2) the time at which extinction of the diffusion flame occurs, and (3) the thickness of quench layers formed on side walls (i.e., on lateral boundaries, with normal vectors parallel to the diffusion-flame plane), and whether, prior to extinction, water vapor formed by burning will condense on these cold walls.

Reconfigurable Antennas for High Data Rate Multi-beam Communication Systems

NASA Technical Reports Server (NTRS)

Bernhard, Jennifer T.; Michielssen, Eric

2005-01-01

High-speed (2-100 Mb/sec) wireless data communication - whether land- or satellite-based - faces a major challenge: high error rates caused by interference and unpredictable environments. A planar antenna system that can be reconfigured to respond to changing conditions has the potential to dramatically improve data throughput and system reliability. Moreover, new planar antenna designs that reduce array size, weight, and cost can have a significant impact on terrestrial and satellite communication system performance. This research developed new individually-reconfigurable planar antenna array elements that can be adjusted to provide multiple beams while providing increased scan angles and higher aperture efficiency than traditional diffraction-limited arrays. These new elements are microstrip spiral antennas with specialized tuning mechanisms that provide adjustable radiation patterns. We anticipate that these new elements can be used in both large and small arrays for inter-satellite communication as well as tracking of multiple mobile surface-based units. Our work has developed both theoretical descriptions as well as experimental prototypes of the antennas in both single element and array embodiments. The technical summary of the results of this work is divided into six sections: A. Cavity model for analysis and design of pattern reconfigurable antennas; B. Performance of antenna in array configurations for broadside and endfire operation; C. Performance of antenna in array configurations for beam scanning operation; D. Simulation of antennas in infinite phased arrays; E. Demonstration of antenna with commercially-available RF MEMS switches; F. Design of antenna MEMS switch combinations for direct simultaneous fabrication.

Planar solar concentrator featuring alignment-free total-internal-reflection collectors and an innovative compound tracker.

PubMed

Teng, Tun-Chien; Lai, Wei-Che

2014-12-15

This study proposed a planar solar concentrator featuring alignment-free total-internal-reflection (TIR) collectors and an innovative compound tracker. The compound tracker, combining a mechanical single-axis tracker and scrollable prism sheets, can achieve a performance on a par with dual-axis tracking while reducing the cost of the tracking system and increasing its robustness. The alignment-free TIR collectors are assembled on the waveguide without requiring alignment, so the planar concentrator is relatively easily manufactured and markedly increases the feasibility for use in large concentrators. Further, the identical TIR collector is applicable to various-sized waveguide slab without requiring modification, which facilitates flexibility regarding the size of the waveguide slab. In the simulation model, the thickness of the slab was 2 mm, and its maximal length reached 6 m. With an average angular tolerance of ±0.6°, and after considering both the Fresnel loss and the angular spread of the sun, the simulation indicates that the waveguide concentrator of a 1000-mm length provides the optical efficiencies of 62-77% at the irradiance concentrations of 387-688, and the one of a 2000-mm length provides the optical efficiencies of 52-64.5% at the irradiance concentrations of 645-1148. Alternatively, if a 100-mm horizontally staggered waveguide slab is collocated with the alignment-free TIR collectors, the optical efficiency would be greatly improved up to 91.5% at an irradiance concentration of 1098 (C(geo) = 1200X).

Large eddy simulation study of turbulent kinetic energy and scalar variance budgets and turbulent/non-turbulent interface in planar jets

NASA Astrophysics Data System (ADS)

Watanabe, Tomoaki; Sakai, Yasuhiko; Nagata, Koji; Ito, Yasumasa

2016-04-01

Spatially developing planar jets with passive scalar transports are simulated for various Reynolds (Re = 2200, 7000, and 22 000) and Schmidt numbers (Sc = 1, 4, 16, 64, and 128) by the implicit large eddy simulation (ILES) using low-pass filtering as an implicit subgrid-scale model. The budgets of resolved turbulent kinetic energy k and scalar variance < {φ }\\prime 2> are explicitly evaluated from the ILES data except for the dissipation terms, which are obtained from the balance in the transport equations. The budgets of k and < {φ }\\prime 2> in the ILES agree well with the DNS and experiments for both high and low Re cases. The streamwise decay of the mean turbulent kinetic energy dissipation rate obeys the power low obtained by the scaling argument. The mechanical-to-scalar timescale ratio C ϕ is evaluated in the self-similar region. For the high Re case, C ϕ is close to the isotropic value (C ϕ = 2) near the jet centerline. However, when Re is not large, C ϕ is smaller than 2 and depends on the Schmidt number. The T/NT interface is also investigated by using the scalar isosurface. The velocity and scalar fields near the interface depend on the interface orientation for all Re. The velocity toward the interface is observed near the interface facing in the streamwise, cross-streamwise, and spanwise directions in the planar jet in the resolved velocity field.

Internal gain in Er-doped As₂S₃ chalcogenide planar waveguides.

PubMed

Yan, Kunlun; Vu, Khu; Madden, Steve

2015-03-01

Low-loss erbium-doped As₂S₃ planar waveguides are fabricated by cothermal evaporation and plasma etching. Internal gain in the telecommunications band is demonstrated for the first time in any chalcogenide glass and additionally in a thin film planar waveguide amplifier configuration.

Two-dimensional topological crystalline insulator phase in Sb/Bi planar honeycomb with tunable Dirac gap

DOE PAGES

Hsu, Chia -Hsiu; Huang, Zhi -Quan; Crisostomo, Christian P.; ...

2016-01-14

We predict planar Sb/Bi honeycomb to harbor a two-dimensional (2D) topological crystalline insulator (TCI) phase based on first-principles computations. Although buckled Sb and Bi honeycombs support 2D topological insulator (TI) phases, their structure becomes planar under tensile strain. The planar Sb/Bi honeycomb structure restores the mirror symmetry, and is shown to exhibit non-zero mirror Chern numbers, indicating that the system can host topologically protected edge states. Our computations show that the electronic spectrum of a planar Sb/Bi nanoribbon with armchair or zigzag edges contains two Dirac cones within the band gap and an even number of edge bands crossing themore » Fermi level. Lattice constant of the planar Sb honeycomb is found to nearly match that of hexagonal-BN. As a result, the Sb nanoribbon on hexagonal-BN exhibits gapped edge states, which we show to be tunable by an out-of the-plane electric field, providing controllable gating of edge state important for device applications.« less

Effects of planar and non-planar driver-side mirrors on age-related discomfort-glare responses

PubMed Central

Lockhart, Thurmon E.; Atsumi, Bunji; Ghosh, Arka; Mekaroonreung, Haruetai; Spaulding, Jeremy

2010-01-01

In this study, we evaluated subjective nighttime discomfort-glare responses on three different types of planar and non-planar driver-side mirrors on two age groups. Fifty-six individuals (28 young [18–35 years] and 28 old [65 years and over]) participated in this experiment. Subjective discomfort-glare rating scores on three different types of driver-side mirrors were assessed utilizing De Boer's rating scale in a controlled nighttime driving environment (laboratory ambient illuminant level—l lux with headlight turned off). Three driver-side mirrors included planar “flat mirror”: radius of curvature 242650.92 mm, reflectivity 0.60114, and surface reflectance 0.60568; “curved mirror”: radius of curvature 1433.3 mm, reflectivity 0.21652, and surface reflectance 0.58092; “blue mirror”: radius of curvature 1957.1 mm, reflectivity 0.25356, and surface reflectance 0.54585. The results indicated that with the same glare level (as measured by angle of incidence and illuminance in front of the eyes), older adults reported worse feelings of glare than their younger counterparts. Furthermore, the results indicated that both young and older adults reported worse feelings of glare for planar driver-side mirror than non-planar driver-side mirrors. These results suggest that older adults' criterion of discomfort-glare is more sensitive than their younger counterparts, and importantly, the non-planar driver-side mirrors can be beneficial in terms of reducing nighttime discomfort-glare for both the young and the elderly. PMID:20582252

Nonlinear air-coupled emission: The signature to reveal and image microdamage in solid materials

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

Solodov, Igor; Busse, Gerd

2007-12-17

It is shown that low-frequency elastic vibrations of near-surface planar defects cause high-frequency ultrasonic radiation in surrounding air. The frequency conversion mechanism is concerned with contact nonlinearity of the defect vibrations and provides efficient generation of air-coupled higher-order ultraharmonics, ultrasubharmonics, and combination frequencies. The nonlinear air-coupled ultrasonic emission is applied for location and high-resolution imaging of damage-induced defects in a variety of solid materials.

Admissible Shape Parameters for a Planar Quasi-Static Constraint Mode Tire Model

DTIC Science & Technology

2014-01-21

Journal of Vibration, 1988. 110(1): p. 70-75. 4. Zegelaar, P.W.A.P., H. B., The In-plane Dynamics of Tyres on Uneven Roads . Vehicle System Dynamics...ADDRESS(ES) Vehicle Terrain performance laboratory,Virginia Tech Mechanical Engineering Department,635 Prices Fork Road - MC 0238,Blacksburg,VA,24061...such that the upper portion is in direct contact with the lower portion and there is a discontinuous and dramatic increase in apparent stiffness). A

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

Howard, J. B.; Richter, H.

This project is concerned with the kinetics and mechanisms of aromatics oxidation and the growth process to polycyclic aromatic hydrocarbons (PAH) of increasing size, soot and fullerenes formation in flames. The overall objective of the experimental aromatics oxidation work is to extend the set of available data by measuring concentration profiles for decomposition intermediates such as phenyl, cyclopentadienyl, phenoxy or indenyl radicals which could not be measured with molecular-beam mass spectrometry to permit further refinement and testing of benzene oxidation mechanisms. The focus includes PAH radicals which are thought to play a major role in the soot formation process whilemore » their concentrations are in many cases too low to permit measurement with conventional mass spectrometry. The radical species measurements are used in critical testing and improvement of a kinetic model describing benzene oxidation and PAH growth. Thermodynamic property data of selected species are determined computationally, for instance using density functional theory (DFT). Potential energy surfaces are explored in order to identify additional reaction pathways. The ultimate goal is to understand the conversion of high molecular weight compounds to nascent soot particles, to assess the roles of planar and curved PAH and relationships between soot and fullerenes formation. The specific aims are to characterize both the high molecular weight compounds involved in the nucleation of soot particles and the structure of soot including internal nanoscale features indicative of contributions of planar and/or curved PAH to particle inception.« less

A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

NASA Astrophysics Data System (ADS)

Li, Hongkai; Qu, Zilian; Zhao, Qian; Tian, Fangxin; Zhao, Dewen; Meng, Yonggang; Lu, Xinchun

2013-12-01

In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to know the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules' GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time.

A reliable control system for measurement on film thickness in copper chemical mechanical planarization system.

PubMed

Li, Hongkai; Qu, Zilian; Zhao, Qian; Tian, Fangxin; Zhao, Dewen; Meng, Yonggang; Lu, Xinchun

2013-12-01

In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to know the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules' GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time.

A reliable control system for measurement on film thickness in copper chemical mechanical planarization system

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

Li, Hongkai; Qu, Zilian; Zhao, Qian

In recent years, a variety of film thickness measurement techniques for copper chemical mechanical planarization (CMP) are subsequently proposed. In this paper, the eddy-current technique is used. In the control system of the CMP tool developed in the State Key Laboratory of Tribology, there are in situ module and off-line module for measurement subsystem. The in situ module can get the thickness of copper film on wafer surface in real time, and accurately judge when the CMP process should stop. This is called end-point detection. The off-line module is used for multi-points measurement after CMP process, in order to knowmore » the thickness of remained copper film. The whole control system is structured with two levels, and the physical connection between the upper and the lower is achieved by the industrial Ethernet. The process flow includes calibration and measurement, and there are different algorithms for two modules. In the process of software development, C++ is chosen as the programming language, in combination with Qt OpenSource to design two modules’ GUI and OPC technology to implement the communication between the two levels. In addition, the drawing function is developed relying on Matlab, enriching the software functions of the off-line module. The result shows that the control system is running stably after repeated tests and practical operations for a long time.« less

Tectonic models for Yucca Mountain, Nevada

USGS Publications Warehouse

O'Leary, Dennis W.

2006-01-01

Performance of a high-level nuclear waste repository at Yucca Mountain hinges partly on long-term structural stability of the mountain, its susceptibility to tectonic disruption that includes fault displacement, seismic ground motion, and igneous intrusion. Because of the uncertainty involved with long-term (10,000 yr minimum) prediction of tectonic events (e.g., earthquakes) and the incomplete understanding of the history of strain and its mechanisms in the Yucca Mountain region, a tectonic model is needed. A tectonic model should represent the structural assemblage of the mountain in its tectonic setting and account for that assemblage through a history of deformation in which all of the observed deformation features are linked in time and space. Four major types of tectonic models have been proposed for Yucca Mountain: a caldera model; simple shear (detachment fault) models; pure shear (planar fault) models; and lateral shear models. Most of the models seek to explain local features in the context of well-accepted regional deformation mechanisms. Evaluation of the models in light of site characterization shows that none of them completely accounts for all the known tectonic features of Yucca Mountain or is fully compatible with the deformation history. The Yucca Mountain project does not endorse a preferred tectonic model. However, most experts involved in the probabilistic volcanic hazards analysis and the probabilistic seismic hazards analysis preferred a planar fault type model. ?? 2007 Geological Society of America. All rights reserved.

Resistive switching effect in the planar structure of all-printed, flexible and rewritable memory device based on advanced 2D nanocomposite of graphene quantum dots and white graphene flakes

NASA Astrophysics Data System (ADS)

Muqeet Rehman, Muhammad; Uddin Siddiqui, Ghayas; Kim, Sowon; Choi, Kyung Hyun

2017-08-01

Pursuit of the most appropriate materials and fabrication methods is essential for developing a reliable, rewritable and flexible memory device. In this study, we have proposed an advanced 2D nanocomposite of white graphene (hBN) flakes embedded with graphene quantum dots (GQDs) as the functional layer of a flexible memory device owing to their unique electrical, chemical and mechanical properties. Unlike the typical sandwich type structure of a memory device, we developed a cost effective planar structure, to simplify device fabrication and prevent sneak current. The entire device fabrication was carried out using printing technology followed by encapsulation in an atomically thin layer of aluminum oxide (Al2O3) for protection against environmental humidity. The proposed memory device exhibited attractive bipolar switching characteristics of high switching ratio, large electrical endurance and enhanced lifetime, without any crosstalk between adjacent memory cells. The as-fabricated device showed excellent durability for several bending cycles at various bending diameters without any degradation in bistable resistive states. The memory mechanism was deduced to be conductive filamentary; this was validated by illustrating the temperature dependence of bistable resistive states. Our obtained results pave the way for the execution of promising 2D material based next generation flexible and non-volatile memory (NVM) applications.

Exploration of dielectric relaxations of a room temperature anti-ferroelectric liquid crystal mixture

NASA Astrophysics Data System (ADS)

Dwivedi, Aanchal; Verma, Rohit; Dhar, R.; Dabrowski, R.

2018-05-01

Dielectric characterization of a technologically important room temperature anti-ferroelectric liquid crystal (AFLC) mixture has been carried out as a function of temperature and frequency. The mixture has a phase sequence of I-SmA*-SmC*-SmCA* -SmIA* -Cr. Electrical study for the planar anchoring of the molecules demonstrates seven relaxation mechanisms in various mesophases of the mixture. Dielectric spectrum of paraelectric SmA* phase exhibits a relaxation mechanism due to the tilt fluctuation of the molecules. In ferroelectric SmC* phase, Goldstone mode has been observed due to the fluctuation in azimuthal angle. In antiferroelectric SmCA*and hexatic SmIA* phases two relaxation mechanisms are observed due to bond orientation order & anti-phase fluctuation and rotation around the short axes respectively.

Recent advances in the fabrication and structure-specific applications of graphene-based inorganic hybrid membranes.

PubMed

Zhao, Xinne; Zhang, Panpan; Chen, Yuting; Su, Zhiqiang; Wei, Gang

2015-03-12

The preparation and applications of graphene (G)-based materials are attracting increasing interests due to their unique electronic, optical, magnetic, thermal, and mechanical properties. Compared to G-based hybrid and composite materials, G-based inorganic hybrid membrane (GIHM) offers enormous advantages ascribed to their facile synthesis, planar two-dimensional multilayer structure, high specific surface area, and mechanical stability, as well as their unique optical and mechanical properties. In this review, we report the recent advances in the technical fabrication and structure-specific applications of GIHMs with desirable thickness and compositions. In addition, the advantages and disadvantages of the methods utilized for creating GIHMs are discussed in detail. Finally, the potential applications and key challenges of GIHMs for future technical applications are mentioned.

Mechanism of instabilities in turbulent combustion leading to flashback

NASA Astrophysics Data System (ADS)

Keller, J. O.; Vaneveld, L.; Ghoniem, A. F.; Daily, J. W.; Oppenheim, A. K.; Korschelt, D.; Hubbard, G. L.

1981-01-01

High-speed schlieren cinematography, combined with synchronized pressure transducer records, was used to investigate the mechanism of combustion instabilities leading to flashback. The combustion chamber had an oblong rectangular cross-section to model the essential features of planar flow, and was provided with a rearward facing step acting as a flameholder. As the rich limit was approached, three instability modes were observed: (1) humming - a significant increase in the amplitude of the vortex pattern; (2) buzzing - a large-scale oscillation of the flame; and (3) chucking - a cyclic reformation of the flame, which results in flashback. The mechanism of these phenomena is ascribed to the action of vortices in the recirculation zone and their interactions with the trailing vortex pattern of the turbulent mixing layer behind the step.

Study on chemical mechanical polishing of silicon wafer with megasonic vibration assisted.

PubMed

Zhai, Ke; He, Qing; Li, Liang; Ren, Yi

2017-09-01

Chemical mechanical polishing (CMP) is the primary method to realize the global planarization of silicon wafer. In order to improve this process, a novel method which combined megasonic vibration to assist chemical mechanical polishing (MA-CMP) is developed in this paper. A matching layer structure of polishing head was calculated and designed. Silicon wafers are polished by megasonic assisted chemical mechanical polishing and traditional chemical mechanical polishing respectively, both coarse polishing and precision polishing experiments were carried out. With the use of megasonic vibration, the surface roughness values Ra reduced from 22.260nm to 17.835nm in coarse polishing, and the material removal rate increased by approximately 15-25% for megasonic assisted chemical mechanical polishing relative to traditional chemical mechanical polishing. Average Surface roughness values Ra reduced from 0.509nm to 0.387nm in precision polishing. The results show that megasonic assisted chemical mechanical polishing is a feasible method to improve polishing efficiency and surface quality. The material removal and finishing mechanisms of megasonic vibration assisted polishing are investigated too. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanical measurements on lithium phosphorous oxynitride coated silicon thin film electrodes for lithium-ion batteries during lithiation and delithiation

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

Al-Obeidi, Ahmed, E-mail: alobeidi@mit.edu; Thompson, Carl V., E-mail: reiner.moenig@kit.edu, E-mail: cthomp@mit.edu; Kramer, Dominik, E-mail: dominik.kramer@kit.edu

2016-08-15

The development of large stresses during lithiation and delithiation drives mechanical and chemical degradation processes (cracking and electrolyte decomposition) in thin film silicon anodes that complicate the study of normal electrochemical and mechanical processes. To reduce these effects, lithium phosphorous oxynitride (LiPON) coatings were applied to silicon thin film electrodes. Applying a LiPON coating has two purposes. First, the coating acts as a stable artificial solid electrolyte interphase. Second, it limits mechanical degradation by retaining the electrode's planar morphology during cycling. The development of stress in LiPON-coated electrodes was monitored using substrate curvature measurements. LiPON-coated electrodes displayed highly reproducible cycle-to-cyclemore » behavior, unlike uncoated electrodes which had poorer coulombic efficiency and exhibited a continual loss in stress magnitude with continued cycling due to film fracture. The improved mechanical stability of the coated silicon electrodes allowed for a better investigation of rate effects and variations of mechanical properties during electrochemical cycling.« less

Planar regions of GaAs (001) prepared by Ga droplet motion

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

Zheng, Changxi, E-mail: changxi.zheng@monash.edu; Tang, Wen-Xin; Jesson, David E., E-mail: jessonDE@cardiff.ac.uk

2016-07-15

The authors describe a simple method for obtaining planar regions of GaAs (001) suitable for surface science studies. The technique, which requires no buffer layer growth, atomic hydrogen source, or the introduction of As flux, employs controllable Ga droplet motion to create planar trail regions during Langmuir evaporation. Low-energy electron microscopy/diffraction techniques are applied to monitor the droplet motion and characterize the morphology and the surface reconstruction. It is found that the planar regions exhibit atomic flatness at the level of a high-quality buffer layer.

Non-planar chemical preconcentrator

DOEpatents

Manginell, Ronald P [Albuquerque, NM; Adkins, Douglas R [Albuquerque, NM; Sokolowski, Sara S [Albuquerque, NM; Lewis, Patrick R [Albuquerque, NM

2006-10-10

A non-planar chemical preconcentrator comprises a high-surface area, low mass, three-dimensional, flow-through sorption support structure that can be coated or packed with a sorptive material. The sorptive material can collect and concentrate a chemical analyte from a fluid stream and rapidly release it as a very narrow temporal plug for improved separations in a microanalytical system. The non-planar chemical preconcentrator retains most of the thermal and fabrication benefits of a planar preconcentrator, but has improved ruggedness and uptake, while reducing sorptive coating concerns and extending the range of collectible analytes.

Anisotropic Magnus Force in Type-II Superconductors with Planar Defects

NASA Astrophysics Data System (ADS)

Monroy, Ricardo Vega; Gomez, Eliceo Cortés

2015-02-01

The effect of planar defects on the Magnus force in type-II superconductors is studied. It is shown that the deformation of the vortex due to the presence of a planar defect leads to a local decrease in the mean free path of electrons in the vortex. This effect reduces the effective Magnus coefficient in normal direction to the planar defect, leading to an anisotropic regime of the Hall effect. The presented developments here can qualitatively explain experimental observations of the anisotropic Hall effect in high- T c superconductors in the mixed state.

Thin film hydrogen sensor

DOEpatents

Cheng, Y.T.; Poli, A.A.; Meltser, M.A.

1999-03-23

A thin film hydrogen sensor includes a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end. 5 figs.

A Planar Hall Thruster for Investigating Electron Mobility in ExB Devices (Preprint)

DTIC Science & Technology

2007-08-24

Hall thruster that emits and collects the Hall current across a planar discharge channel is described. The planar Hall thruster (PHT) is being investigated for use as a test bed to study electron mobility in ExB devices. The planar geometry attempts to de-couple the complex electron motion found in annular thrusters by using simplified geometry. During this initial test, the PHT was operated at discharge voltages between 50-150 V to verify operability and stability of the device. Hall current was emitted by hollow cathode electron sources and

Dichlorido[(S,R(S))-1-diphenylphosphino-2-(ethylsulfanylmethyl)ferrocene]palladium(II).

PubMed

Diab, Lisa; Daran, Jean-Claude; Gouygou, Maryse; Manoury, Eric; Urrutigoïty, Martine

2007-12-01

The reaction of enantiomerically pure planar chiral ferrocene phosphine thioether with bis(acetonitrile)dichloridopalladium yields the title square-planar mononuclear palladium complex as an enantiomerically pure single diastereoisomer, [PdFe(C5H5)(C20H20PS)Cl2]. The planar chirality of the ligand is retained in the complex and fully controls the central chirality on the S atom. The absolute configuration, viz. S for the planar chirality and R for the S atom, is unequivocally determined by refinement of the Flack parameter.

Radiative flux from a planar multiple point source within a cylindrical enclosure reaching a coaxial circular plane

NASA Astrophysics Data System (ADS)

Tryka, Stanislaw

2007-04-01

A general formula and some special integral formulas were presented for calculating radiative fluxes incident on a circular plane from a planar multiple point source within a coaxial cylindrical enclosure perpendicular to the source. These formula were obtained for radiation propagating in a homogeneous isotropic medium assuming that the lateral surface of the enclosure completely absorbs the incident radiation. Exemplary results were computed numerically and illustrated with three-dimensional surface plots. The formulas presented are suitable for determining fluxes of radiation reaching planar circular detectors, collectors or other planar circular elements from systems of laser diodes, light emitting diodes and fiber lamps within cylindrical enclosures, as well as small biological emitters (bacteria, fungi, yeast, etc.) distributed on planar bases of open nontransparent cylindrical containers.

Method for laser welding a fin and a tube

DOEpatents

Fuerschbach, Phillip W.; Mahoney, A. Roderick; Milewski, John O

2001-01-01

A method of laser welding a planar metal surface to a cylindrical metal surface is provided, first placing a planar metal surface into approximate contact with a cylindrical metal surface to form a juncture area to be welded, the planar metal surface and cylindrical metal surface thereby forming an acute angle of contact. A laser beam, produced, for example, by a Nd:YAG pulsed laser, is focused through the acute angle of contact at the juncture area to be welded, with the laser beam heating the juncture area to a welding temperature to cause welding to occur between the planar metal surface and the cylindrical metal surface. Both the planar metal surface and cylindrical metal surface are made from a reflective metal, including copper, copper alloys, stainless steel alloys, aluminum, and aluminum alloys.

Catadioptric planar compound eye with large field of view.

PubMed

Deng, Huaxia; Gao, Xicheng; Ma, Mengchao; Li, Yunyang; Li, Hang; Zhang, Jin; Zhong, Xiang

2018-05-14

The planar compound eye has the advantages of simple structure and no requirement for complex relay optical elements, but the field of view (FOV) is very difficult to expand. Overcoming the limitation of FOV, especially with simple structures, is a great challenge for the development of planar compound eyes. Different from the existing designs that only considering refraction, this article proposes a catadioptric planar compound eye based on the reflection and refraction to expand the FOV. In the proposed design, the incident light from a large angle is reflected into the lenslet array by two rotationally symmetric mirrors whose surface equations are optimized by mathematical and optical softwares. The FOV of the proposed catadioptric planar compound eye theoretically can reach 96.6°, which is much wider than the opening record of 70°. Moreover, no distortion of the imaging system can be obtained theoretically in this design. Simulation results show a linearity of better than 99% for the most of the incident angles. The verification experiments show that the FOV of the proposed device can reach 90.7° while the FOV of the corresponding planar compound eye without mirrors is 41.6°. The proposed catadioptric planar compound eye has the great potential in monitoring, detection and virtual reality since the FOV has been widen significantly.

Planar induction of convergence and extension of the neural plate by the organizer of Xenopus.

PubMed

Keller, R; Shih, J; Sater, A K; Moreno, C

1992-03-01

This paper demonstrates that convergence and extension within the neural plate of Xenopus laevis are regulated by planar inductive interactions with the adjacent Spemann organizer. The companion article (Keller et al.: Developmental Dynamics 193:199-217, 1992) showed that the prospective hindbrain and spinal cord occupy a very short and very wide area just above the Spemann organizer in the early gastrula and that these regions converge and extend greatly during gastrulation and neurulation, using a sequence of radial and mediolateral cell intercalations. In this article, we show that "planar" contact of these regions with the organizer at their vegetal edge until stage 11 is sufficient to induce convergence and extension, after which their convergence and extension become autonomous. Grafts of the organizer in planar contact with uninduced ectodermal tissues induce these ectodermal tissues to converge and extend by a planar inductive signal from the organizer. Labeling of the inducing or responding tissues confirms that only planar interactions occur. Neural convergence and extension are actually hindered in explants deliberately constructed so that vertical interactions occur. These results show unambiguously that the Spemann organizer induces the extraordinary and precocious convergence and extension movements of the Xenopus neural plate by planar interactions acting over short distances.

Analysis and design of planar and non-planar wings for induced drag minimization

NASA Technical Reports Server (NTRS)

Mortara, K.; Straussfogel, Dennis M.; Maughmer, Mark D.

1991-01-01

The goal of the work was to develop and validate computational tools to be used for the design of planar and non-planar wing geometries for minimum induced drag. Because of the iterative nature of the design problem, it is important that, in addition to being sufficiently accurate for the problem at hand, they are reasonably fast and computationally efficient. Toward this end, a method of predicting induced drag in the presence of a non-rigid wake is coupled with a panel method. The induced drag prediction technique is based on the Kutta-Joukowski law applied at the trailing edge. Until recently, the use of this method has not been fully explored and pressure integration and Trefftz-plane calculations favored. As is shown in this report, however, the Kutta-Joukowski method is able to give better results for a given amount of effort than the more common techniques, particularly when relaxed wakes and non-planar wing geometries are considered. Using these tools, a workable design method is in place which takes into account relaxed wakes and non-planar wing geometries. It is recommended that this method be used to design a wind-tunnel experiment to verify the predicted aerodynamic benefits of non-planar wing geometries.

Simulations of absorption spectra of conjugated oligomers: role of planar conformation and aggregation in condensed phase

NASA Astrophysics Data System (ADS)

Yuan, Xiang-Ai; Wen, Jin; Zheng, Dong; Ma, Jing

2018-04-01

This Review highlights the structure/property relationship underlying the morphology modulation through various factors towards the exploration of light-absorbing materials for efficient utilisation of solar power. Theoretical study using a combination of molecular dynamics imulations and the time-dependent density functional theory demonstrated that the planarity plays an important role in tuning spectral properties of oligomer aggregates. The aggregation-induced blue-shift in absorption spectra of oligothiophenes and the red-shift for oligofluorenols were rationalised in a unified way from the reduced (and increased) content of planar conformations in molecular aggregates. The planarity versus non-planarity of oligomers can be modulated by introduction of alkyl side chain or steric bulky substituents. The substitution with various groups in the ortho-position of azobenzene leads to the distorted backbone, breaking symmetry, and hence the red-shift in spectra, expanding the application in biological systems with visible light absorption. The donor-acceptor substituent groups in conjugated oligomers can increase the degree of planarity, electron delocalisation and polarisation, and charge separation, giving rise to the red-shift in spectra and enhancement in polarisability and charge mobility for device applications. The solvent dependent and pH-sensitive properties and intramolecular hydrogen bonds also caused the shift of absorption spectra with the appearance of planar conformers.

Multiple-stripe lithiation mechanism of individual SnO2 nanowires in a flooding geometry

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

Zhong, Li; Liu, Xiao H.; Wang, G. F.

2011-06-17

The atomic scale lithiation mechanism of individual SnO2 nanowires in a flooding geometry with the entire wires being immersed in the electrolyte was revealed by in-situ transmission electron microscopy. The lithiation initiated multiple stripes with width of a few nanometer parallel to {020} planes transversing the entire wires, serving as multiple reaction fronts for late stage of lithiation. Inside the stripes, we identified high density of dislocations and enlarged inter-planar spacing, which provide effective path for lithium ion transport. The density of the stripes increased with further lithiation, and eventually they merged with one another, causing a large enlongation andmore » volume expansion and the crystalline to amorphous phase transformation. This multiple stripes and multiple reaction fronts lithiation mechanism is unexpected and differs completely from the expected core-shell lithiation mechanism.« less

Planar Impacts in Rollover Crashes: Significance, Distribution and Injury Epidemiology

PubMed Central

Bose, Dipan; Kerrigan, Jason R.; Foster, Jonathan B.; Crandall, Jeff R.; Tobaru, Shigeo

2011-01-01

While one third of all fatal motor vehicle crashes involve rollover of the vehicle, a substantially large portion of these rollover crashes involve planar impacts (e.g., frontal, side or rear impact) that influence the crash kinematics and subsequently the injury outcome. The objective of the study was to evaluate the distribution of planar impacts in rollover crashes, and in particular, to describe the differences in the underlying crash kinematics, injury severity and the regional distribution of injuries when compared to the rollover-dominated crashes without significant planar impact (i.e., primary rollovers). Sampled cases (n=6,900) from the U.S. National Automotive Sampling System – Crashworthiness Data System, representing approximately 3.3 million belted drivers involved in a rollover crash in years 1998–2008, were analyzed. Single vehicle rollover crashes with significant planar impact (21% of all rollover crashes) were in general more likely to result in occupant fatality and involved higher incidence of moderate to severe injuries compared to single vehicle primary rollovers (p<0.05). A substantial proportion of the planar impact rollovers ended in single quarter turn crashes (30%), mostly resulting from a frontal impact (59%). While chest was the most frequently injured body region among all rollover victims sustaining severe injuries, severe injuries sustained in primary rollovers were more isolated (single body region) in comparison to the ones sustained in rollovers with planar impacts. The results emphasize the higher risk of rollover victims sustaining an injury and the differences in distribution of injuries sustained when a planar impact is associated with the rollover crash. PMID:22105400

Free-Piston Stirling Power Conversion Unit for Fission Surface Power, Phase I Final Report

NASA Technical Reports Server (NTRS)

Wood, J. Gary; Buffalino, Andrew; Holliday, Ezekiel; Penswick, Barry; Gedeon, David

2010-01-01

This report summarizes the design of a 12 kW dual opposed free-piston Stirling convertor and controller for potential future use in space missions. The convertor is heated via a pumped NaK loop and cooling is provided by a pumped water circuit. Convertor efficiency is projected at 27 percent (AC electrical out/heat in). The controller converts the AC electrical output to 120 Vdc and is projected at 91 percent efficiency. A mechanically simple arrangement, based on proven technology, was selected in which the piston is resonated almost entirely by the working space pressure swing, while the displacer is resonated by planar mechanical springs in the bounce space.

Flow structures in the wake of heaving and pitching foils

NASA Astrophysics Data System (ADS)

Najdzin, Derek; Pardo, Enrique; Leftwich, Megan C.; Bardet, Philippe M.

2012-11-01

A 10-bar mechanism drives a cambering hydrofoil in an oscillatory heaving and pitching motion that replicates the flapping motion of a dolphin tail. The mechanism sits on a force-balance with six strain gages that together measure the forces and moments experienced by the fin during an oscillation. Planar Laser-Induced Fluorescence is used to image the flow structures created downstream of the cambering fin for a range of Reynolds and Strouhal numbers. The images are taken in the mid-plane, parallel to the bottom of the water tunnel. These results are compared to a rigid foil at matching conditions to investigate the role of camber changes during the flapping cycle.

Results from new multi-megabar shockless compression experiments at the Z machine

DOE PAGES

Davis, Jean-Paul; Knudson, Marcus D.; Brown, Justin L.

2017-01-01

Sandia’s Z Machine has been used to magnetically drive shockless compression of materials in a planar configuration to multi-megabar pressure levels, allowing accurate measurements of quasi-isentropic mechanical response at relatively low temperatures in the solid phase. This work details recent improvements to design and analysis of such experiments, including the use of new data on the mechanical and optical response of lithium fluoride windows. Comparison of windowed and free-surface data on copper to 350 GPa lends confidence to the window correction method. Preliminary results are presented on gold to 500 GPa and platinum to 450 GPa; both appear stiffer thanmore » existing models.« less

Surface Tension: Mechanics, Thermodynamics, and Relaxation Times

NASA Astrophysics Data System (ADS)

Tovbin, Yu. K.

2018-06-01

A microscopic analysis is presented of the existing definitions of equilibrium surface tension, which can be divided into two types: mechanical and thermodynamic. Each type of definition can be studied from the presentation below according to thermodynamic hypotheses or molecular calculations. An analysis of the planar interface is given and its generalization for curved (spherical) interfaces is considered. The distinction between approaches describing the surface tension of metastable and equilibrium droplets is discussed. Based on nonequilibrium thermodynamics, it is shown that the introduction of metastable droplets is due to a violation of the relationship between the times of impulse and chemical potential relaxation in condensed phases. Problems of calculating the surface tension in nonequilibrium situations are created.

Recent progress in design and hybridization of planar grating-based transceivers

NASA Astrophysics Data System (ADS)

Bidnyk, S.; Pearson, M.; Balakrishnan, A.; Gao, M.

2007-06-01

We report on recent progress in simulations, physical layout, fabrication and hybridization of planar grating-based transceivers for passive optical networks (PONs). Until recently, PON transceivers have been manufactured using bulk micro-optical components. Today, advancements in modeling and simulation techniques has made it possible to design complex elements in the same silica-on silicon PLC platform and create an alternative platform for manufacturing of bi-directional transceivers. In our chips we simulated an integrated chip that monolithically combined planar reflective gratings and cascaded Mach-Zehnder interferometers. We used a combination of the finite element method and beam propagation method to model cascaded interferometers with enhanced coupling coefficients. Our simulations show that low-diffraction order planar reflective gratings, designed for small incidence and reflection angles, possess the required dispersion strength to meet the PON specifications. Subsequently, we created structures for passive alignment and hybridized photodetectors and lasers. We believe that advancements in simulation of planar lightwave circuits with embedded planar reflective gratings will result in displacement of the thin-film filters (TFFs) technology in many applications that require a high degree of monolithic and hybrid integration.

Modeling and analysis of a novel planar eddy current damper

NASA Astrophysics Data System (ADS)

Zhang, He; Kou, Baoquan; Jin, Yinxi; Zhang, Lu; Zhang, Hailin; Li, Liyi

2014-05-01

In this paper, a novel 2-DOF permanent magnet planar eddy current damper is proposed, of which the stator is made of a copper plate and the mover is composed of two orthogonal 1-D permanent magnet arrays with a double sided structure. The main objective of the planar eddy current damper is to provide two orthogonal damping forces for dynamic systems like the 2-DOF high precision positioning system. Firstly, the basic structure and the operating principle of the planar damper are introduced. Secondly, the analytical model of the planar damper is established where the magnetic flux density distribution of the permanent magnet arrays is obtained by using the equivalent magnetic charge method and the image method. Then, the analytical expressions of the damping force and damping coefficient are derived. Lastly, to verify the analytical model, the finite element method (FEM) is adopted for calculating the flux density and a planar damper prototype is manufactured and thoroughly tested. The results from FEM and experiments are in good agreement with the ones from the analytical expressions indicating that the analytical model is reasonable and correct.

Dynamical analysis of surface-insulated planar wire array Z-pinches

NASA Astrophysics Data System (ADS)

Li, Yang; Sheng, Liang; Hei, Dongwei; Li, Xingwen; Zhang, Jinhai; Li, Mo; Qiu, Aici

2018-05-01

The ablation and implosion dynamics of planar wire array Z-pinches with and without surface insulation are compared and discussed in this paper. This paper first presents a phenomenological model named the ablation and cascade snowplow implosion (ACSI) model, which accounts for the ablation and implosion phases of a planar wire array Z-pinch in a single simulation. The comparison between experimental data and simulation results shows that the ACSI model could give a fairly good description about the dynamical characteristics of planar wire array Z-pinches. Surface insulation introduces notable differences in the ablation phase of planar wire array Z-pinches. The ablation phase is divided into two stages: insulation layer ablation and tungsten wire ablation. The two-stage ablation process of insulated wires is simulated in the ACSI model by updating the formulas describing the ablation process.

SU-C-207-02: A Method to Estimate the Average Planar Dose From a C-Arm CBCT Acquisition

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

Supanich, MP

2015-06-15

Purpose: The planar average dose in a C-arm Cone Beam CT (CBCT) acquisition had been estimated in the past by averaging the four peripheral dose measurements in a CTDI phantom and then using the standard 2/3rds peripheral and 1/3 central CTDIw method (hereafter referred to as Dw). The accuracy of this assumption has not been investigated and the purpose of this work is to test the presumed relationship. Methods: Dose measurements were made in the central plane of two consecutively placed 16cm CTDI phantoms using a 0.6cc ionization chamber at each of the 4 peripheral dose bores and in themore » central dose bore for a C-arm CBCT protocol. The same setup was scanned with a circular cut-out of radiosensitive gafchromic film positioned between the two phantoms to capture the planar dose distribution. Calibration curves for color pixel value after scanning were generated from film strips irradiated at different known dose levels. The planar average dose for red and green pixel values was calculated by summing the dose values in the irradiated circular film cut out. Dw was calculated using the ionization chamber measurements and film dose values at the location of each of the dose bores. Results: The planar average dose using both the red and green pixel color calibration curves were within 10% agreement of the planar average dose estimated using the Dw method of film dose values at the bore locations. Additionally, an average of the planar average doses calculated using the red and green calibration curves differed from the ionization chamber Dw estimate by only 5%. Conclusion: The method of calculating the planar average dose at the central plane of a C-arm CBCT non-360 rotation by calculating Dw from peripheral and central dose bore measurements is a reasonable approach to estimating the planar average dose. Research Grant, Siemens AG.« less

The equilibrium molecular structures of cross-conjugated alkenes with particular reference to [3]- and [4]-dendralene from ab initio studies of various conformers

NASA Astrophysics Data System (ADS)

Palmer, Michael H.; Blair-Fish, John A.; Sherwood, Paul

1997-07-01

A study of the equilibrium structures and relative energies for the conformers of 3-methylenepenta-1,4-diene (MPD) and bis(3,4-methylene)-1,5-hexadiene (MHD) have been obtained by SCF and MP2 correlated methods; a double zeta+polarisation basis set (DZP) was used. Both planar and non-planar forms were evaluated for a variety of point groups. The force constants for each conformer were obtained, in order to determine whether the minima were saddle points rather than genuine minima owing to the constraints of molecular symmetry. For both molecules, all the non-planar forms studied were of lower energy than the best planar-forms. Indeed the planar structures are all saddle-points between the interconverting pairs of non-planar forms, as shown by one or more negative vibration frequencies for the planar molecules. The relative energies and structures of the different conformers of MPD and MHD are almost identical between the SCF and MP2 series, the MP2 calculations merely leading to slight extensions of the C=C bonds, minor changes in dihedral angles, and small changes otherwise. Because of the H⋯H interactions, all the planar forms showed considerable in-plane angle bending, and small but consistent H-C bond compressions were also obtained in the most hindered cases. The lowest energy conformer of MPD is a gauche-trans conformer, with symmetry C 1, but a second conformer of trans-trans type and C 2 symmetry lies only 6 kJ mol -1 above. The C 2 non-planar conformer of MHD containing (basically) trans-butadiene units is the lowest energy by a significant amount, but several trans-cis and cis-cis conformers were all identified as potential species for gas phase mixtures.

Electrolytic Cell For Production Of Aluminum Employing Planar Anodes.

DOEpatents

Barnett, Robert J.; Mezner, Michael B.; Bradford, Donald R

2004-10-05

A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising providing a molten salt electrolyte having alumina dissolved therein in an electrolytic cell. A plurality of anodes and cathodes having planar surfaces are disposed in a generally vertical orientation in the electrolyte, the anodes and cathodes arranged in alternating or interleaving relationship to provide anode planar surfaces disposed opposite cathode planar surfaces, the anode comprised of carbon. Electric current is passed through anodes and through the electrolyte to the cathodes depositing aluminum at the cathodes and forming carbon containing gas at the anodes.

Development of Ultra-Low Noise, High Sensitivity Planar Metal Grating Coupled AlGaAs/GaAs Multiquantum Well IR Detectors for Focal Plane Array Staring IR Sensor Systems

DTIC Science & Technology

1992-05-01

Development of Ultra-Low Noise , High Sensitivity Planar Metal Grating Coupled AlGaAs/GaAs Multiquantum Well IR Detectors for Focal Plane Array...February 1 - April 30, 1992 Project Title: Development of low- noise high-detectivity planar metal grating coupled III-V multiquantum-well/superlattice...low- noise and high-detectivity planar metal grating coupled bound-to- miniband (BTM) GaAs/AlGaAs and step-bound-to-miniband (SBTM) InGaAs/AlGaAs /GaAs

Planar-type ferromagnetic tunnel junctions fabricated by SPM local oxidation

NASA Astrophysics Data System (ADS)

Tomoda, Y.; Kayashima, S.; Ogino, T.; Motoyama, M.; Takemura, Y.; Shirakashi, J.

Nanometer-scale oxide wires were fabricated by local oxidation nanolithography using scanning probe microscope (SPM). This technique was applied to the fabrication of planar-type Ni/Ni oxide/Ni ferromagnetic tunnel junctions. In order to induce magnetic shape anisotropy, asymmetrical channel structure was patterned by conventional photolithography and wet etching processes. The magnetoresistance (MR) characteristics were clearly shown in the planar-type Ni/Ni oxide/Ni ferromagnetic tunnel junctions. MR ratio of above 100% was obtained at 17 K. This result suggests that the local oxidation nanolithography using SPM is useful for the application to planar-type ferromagnetic tunnel junctions.

Features and technologies of ERS-1 (ESA) and X-SAR antennas

NASA Technical Reports Server (NTRS)

Schuessler, R.; Wagner, R.

1986-01-01

Features and technologies of planar waveguide array antennas developed for spaceborne microwave sensors are described. Such antennas are made from carbon fiber reinforced plastic (CFRP) employing special manufacturing and metallization techniques to achieve satisfactory electrical properties. Mechanical design enables deployable antenna structures necessary for satellite applications (e.g., ESA ERS-1). The slotted waveguide concept provides high aperture efficiency, good beamshaping capabilities, and low losses. These CFRP waveguide antennas feature low mass, high accuracy and stiffness, and can be operated within wide temperature ranges.

Flexible and weaveable capacitor wire based on a carbon nanocomposite fiber.

PubMed

Ren, Jing; Bai, Wenyu; Guan, Guozhen; Zhang, Ye; Peng, Huisheng

2013-11-06

A flexible and weaveable electric double-layer capacitor wire is developed by twisting two aligned carbon nanotube/ordered mesoporous carbon composite fibers with remarkable mechanical and electronic properties as electrodes. This capacitor wire exhibits high specific capacitance and long life stability. Compared with the conventional planar structure, the capacitor wire is also lightweight and can be integrated into various textile structures that are particularly promising for portable and wearable electronic devices. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical and Genetic Mechanisms Guiding the Evolution and Development of Dendritic, Flapping Insect-Wings

DTIC Science & Technology

2010-04-12

computer graphics, to music . Map L systems [2, 6, 7] extend the parallel rewriting in L systems to planar graphs with cycles, called maps [8]. The maps...carbon. For easy of reading , in the results below the mass is represented by the percentage carbon laminate coverage. As explained previously, the...previously, that value can be read in the left vertical axis. There are nine designs in the Pareto front. Depending on design goals any of these individuals

High energy behavior of gravity at large N

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

Canfora, F.

2006-09-15

A first step in the analysis of the renormalizability of gravity at large N is carried out. Suitable resummations of planar diagrams give rise to a theory in which there is only a finite number of primitive, superficially divergent, Feynman diagrams. The mechanism is similar to the one which makes the 3D Gross-Neveu model renormalizable at large N. The connections with gravitational confinement and Kawai-Lewellen-Tye relations are briefly analyzed. Some potential problems in fulfilling the Zinn-Justin equations are pointed out.

A Mobile Robot for Small Object Handling

NASA Astrophysics Data System (ADS)

Fišer, Ondřej; Szűcsová, Hana; Grimmer, Vladimír; Popelka, Jan; Vonásek, Vojtěch; Krajník, Tomáš; Chudoba, Jan

The aim of this paper is to present an intelligent autonomous robot capable of small object manipulation. The design of the robot is influenced mainly by the rules of EUROBOT 09 competition. In this challenge, two robots pick up objects scattered on a planar rectangular playfield and use these elements to build models of Hellenistic temples. This paper describes the robot hardware, i.e. electro-mechanics of the drive, chassis and manipulator, as well as the software, i.e. localization, collision avoidance, motion control and planning algorithms.

Biaxial Mechanical Evaluation of Absorbable and Nonabsorbable Synthetic Surgical Meshes Used for Hernia Repair: Physiological Loads Modify Anisotropy Response.

PubMed

Cordero, A; Hernández-Gascón, B; Pascual, G; Bellón, J M; Calvo, B; Peña, E

2016-07-01

The aim of this study was to obtain information about the mechanical properties of six meshes commonly used for hernia repair (Surgipro(®), Optilene(®), Infinit(®), DynaMesh(®), Ultrapro™ and TIGR(®)) by planar biaxial tests. Stress-stretch behavior and equibiaxial stiffness were evaluated, and the anisotropy was determined by testing. In particular, equibiaxial test (equal simultaneous loading in both directions) and biaxial test (half of the load in one direction following the Laplace law) were selected as a representation of physiologically relevant loads. The majority of the meshes displayed values in the range of 8 and 18 (N/mm) in each direction for equibiaxial stiffness (tangent modulus under equibiaxial load state in both directions), while a few achieved 28 and 50 (N/mm) (Infinit (®) and TIGR (®)). Only the Surgipro (®) mesh exhibited planar isotropy, with similar mechanical properties regardless of the direction of loading, and an anisotropy ratio of 1.18. Optilene (®), DynaMesh (®), Ultrapro (®) and TIGR (®) exhibited moderate anisotropy with ratios of 1.82, 1.84, 2.17 and 1.47, respectively. The Infinit (®) scaffold exhibited very high anisotropy with a ratio of 3.37. These trends in material anisotropic response changed during the physiological state in the human abdominal wall, i.e. T:0.5T test, which the meshes were loaded in one direction with half the load used in the other direction. The Surgipro (®) mesh increased its anisotropic response (Anis[Formula: see text] = 0.478) and the materials that demonstrated moderate and high anisotropic responses during multiaxial testing presented a quasi-isotropic response, especially the Infinit(®) mesh that decreased its anisotropic response from 3.369 to 1.292.

An ultrafast spectroscopic and quantum mechanical investigation of multiple emissions in push-pull pyridinium derivatives bearing different electron donors.

PubMed

Carlotti, B; Benassi, E; Cesaretti, A; Fortuna, C G; Spalletti, A; Barone, V; Elisei, F

2015-08-28

A joint experimental and theoretical approach, involving state-of-the-art femtosecond fluorescence up-conversion measurements and quantum mechanical computations including vibronic effects, was employed to get a deep insight into the excited state dynamics of two cationic dipolar chromophores (Donor-π-Acceptor(+)) where the electron deficient portion is a N-methyl pyridinium and the electron donor a trimethoxyphenyl or a pyrene, respectively. The ultrafast spectroscopic investigation, and the time resolved area normalised emission spectra in particular, revealed a peculiar multiple emissive behaviour and allowed the distinct emitting states to be remarkably distinguished from solvation dynamics, occurring in water in a similar timescale. The two and three emissions experimentally detected for the trimethoxyphenyl and pyrene derivatives, respectively, were associated with specific local emissive minima in the potential energy surface of S1 on the ground of quantum-mechanical calculations. A low polar and planar Locally Excited (LE) state together with a highly polar and Twisted Intramolecular Charge Transfer (TICT) state is identified to be responsible for the dual emission of the trimethoxyphenyl compound. Interestingly, the more complex photobehaviour of the pyrenyl derivative was explained considering the contribution to the fluorescence coming not only from the LE and TICT states but also from a nearly Planar Intramolecular Charge Transfer (PICT) state, with both the TICT and the PICT generated from LE by progressive torsion around the quasi-single bond between the methylpyridinium and the ethene bridge. These findings point to an interconversion between rotamers for the pyrene compound taking place in its excited state against the Non-equilibrated Excited Rotamers (NEER) principle.

Generation of whistler-wave heated discharges with planar resonant RF networks.

PubMed

Guittienne, Ph; Howling, A A; Hollenstein, Ch

2013-09-20

Magnetized plasma discharges generated by a planar resonant rf network are investigated. A regime transition is observed above a magnetic field threshold, associated with rf waves propagating in the plasma and which present the characteristics of whistler waves. These wave heated regimes can be considered as analogous to conventional helicon discharges, but in planar geometry.

Deterministic switching of hierarchy during wrinkling in quasi-planar bilayers

DOE PAGES

Saha, Sourabh K.; Culpepper, Martin L.

2016-04-25

Emergence of hierarchy during compression of quasi-planar bilayers is preceded by a mode-locked state during which the quasi-planar form persists. Transition to hierarchy is determined entirely by geometrically observable parameters. This results in a universal transition phase diagram that enables one to deterministically tune hierarchy even with limited knowledge about material properties.

D-section structural tubes

NASA Technical Reports Server (NTRS)

Leete, II, John H. (Inventor); Skinner, William J. (Inventor)

1989-01-01

Structural members for a frame or truss are formed of two substantially identical elongated tubular like members each having a planar extending wall with the tubular members joined together along the planar wall, back to back, and end portions of the joined planar walls form extending lugs. A complementary joint fitting includes a clevis having a slot for receiving the lug.

Dolomitization and neomorphism of Mississippian (Visean) upper debolt formation, Blueberry field, northeastern British Columbia: Geologic, petrologic, and chemical evidence

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

Durocher, S.; Al-Aasm, I.S.

1997-06-01

Petrographic, chemical, and isotopic studies of the Mississippian (Visean) upper Debolt Formation in the Blueberry field, British Columbia, Canada, reveal that dolomitization was the result of several diagenetic events and that neomorphic alteration of these dolomites significantly modified their original chemical signatures. These studies also demonstrate how tectonics play an important role in controlling and modifying reservoir dolomites in the area. Petrographic investigations have documented two early dolomite phases, (1) early matrix dolomite and (2) pervasive dolomite, and two later generations, (3) coarse cement and (4) pseudomorphic replacement of crinoids. Early matrix dolomite occurs as small (average 25 {mu}m) subhedralmore » to euhedral crystals that replace the matrix of carbonate mudstones, wackestones, and packstones. Petrographic evidence suggests that early matrix dolomite had a relatively early, precompaction origin, possibly from marine fluids. However, geochemical evidence indicates that later fluids have altered their original geochemical signatures. Pervasive dolomite, which forms the reservoir intercrystalline porosity, occurs with planar-s and planar-e textures. Planar-s crystals typically have a dirty appearance and exhibit homogeneous dull brown/red cathodoluminescence colors. Planar-e crystals may appear with a cloudy core and a clear rim, and under cathodoluminescence display an irregular dull brown/red core and a thin, bright red rim. Due to the spatial distribution pattern of pervasive dolomite with respect to the overlying unconformity surface, its paleogeographic distribution and close temporal relationship with meteoric diagenetic events, pervasive dolomite formed from a mixture of seawater and meteoric fluids. However, alteration of their primary chemistry by later fluids is indicated by their depleted {delta}{sup 18}O values and radiogenic {sup 87}Sr/{sup 86}Sr ratios.« less

Observation of ‘hidden’ planar defects in boron carbide nanowires and identification of their orientations

PubMed Central

2014-01-01

The physical properties of nanostructures strongly depend on their structures, and planar defects in particular could significantly affect the behavior of the nanowires. In this work, planar defects (twins or stacking faults) in boron carbide nanowires are extensively studied by transmission electron microscopy (TEM). Results show that these defects can easily be invisible, i.e., no presence of characteristic defect features like modulated contrast in high-resolution TEM images and streaks in diffraction patterns. The simplified reason of this invisibility is that the viewing direction during TEM examination is not parallel to the (001)-type planar defects. Due to the unique rhombohedral structure of boron carbide, planar defects are only distinctive when the viewing direction is along the axial or short diagonal directions ([100], [010], or 1¯10) within the (001) plane (in-zone condition). However, in most cases, these three characteristic directions are not parallel to the viewing direction when boron carbide nanowires are randomly dispersed on TEM grids. To identify fault orientations (transverse faults or axial faults) of those nanowires whose planar defects are not revealed by TEM, a new approach is developed based on the geometrical analysis between the projected preferred growth direction of a nanowire and specific diffraction spots from diffraction patterns recorded along the axial or short diagonal directions out of the (001) plane (off-zone condition). The approach greatly alleviates tedious TEM examination of the nanowire and helps to establish the reliable structure–property relations. Our study calls attention to researchers to be extremely careful when studying nanowires with potential planar defects by TEM. Understanding the true nature of planar defects is essential in tuning the properties of these nanostructures through manipulating their structures. PMID:24423258

Observation of 'hidden' planar defects in boron carbide nanowires and identification of their orientations.

PubMed

Guan, Zhe; Cao, Baobao; Yang, Yang; Jiang, Youfei; Li, Deyu; Xu, Terry T

2014-01-15

The physical properties of nanostructures strongly depend on their structures, and planar defects in particular could significantly affect the behavior of the nanowires. In this work, planar defects (twins or stacking faults) in boron carbide nanowires are extensively studied by transmission electron microscopy (TEM). Results show that these defects can easily be invisible, i.e., no presence of characteristic defect features like modulated contrast in high-resolution TEM images and streaks in diffraction patterns. The simplified reason of this invisibility is that the viewing direction during TEM examination is not parallel to the (001)-type planar defects. Due to the unique rhombohedral structure of boron carbide, planar defects are only distinctive when the viewing direction is along the axial or short diagonal directions ([100], [010], or 1¯10) within the (001) plane (in-zone condition). However, in most cases, these three characteristic directions are not parallel to the viewing direction when boron carbide nanowires are randomly dispersed on TEM grids. To identify fault orientations (transverse faults or axial faults) of those nanowires whose planar defects are not revealed by TEM, a new approach is developed based on the geometrical analysis between the projected preferred growth direction of a nanowire and specific diffraction spots from diffraction patterns recorded along the axial or short diagonal directions out of the (001) plane (off-zone condition). The approach greatly alleviates tedious TEM examination of the nanowire and helps to establish the reliable structure-property relations. Our study calls attention to researchers to be extremely careful when studying nanowires with potential planar defects by TEM. Understanding the true nature of planar defects is essential in tuning the properties of these nanostructures through manipulating their structures.

Growth and characterization of textured well-faceted ZnO on planar Si(100), planar Si(111), and textured Si(100) substrates for solar cell applications.

PubMed

Tsai, Chin-Yi; Lai, Jyong-Di; Feng, Shih-Wei; Huang, Chien-Jung; Chen, Chien-Hsun; Yang, Fann-Wei; Wang, Hsiang-Chen; Tu, Li-Wei

2017-01-01

In this work, textured, well-faceted ZnO materials grown on planar Si(100), planar Si(111), and textured Si(100) substrates by low-pressure chemical vapor deposition (LPCVD) were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathode luminescence (CL) measurements. The results show that ZnO grown on planar Si(100), planar Si(111), and textured Si(100) substrates favor the growth of ZnO(110) ridge-like, ZnO(002) pyramid-like, and ZnO(101) pyramidal-tip structures, respectively. This could be attributed to the constraints of the lattice mismatch between the ZnO and Si unit cells. The average grain size of ZnO on the planar Si(100) substrate is slightly larger than that on the planar Si(111) substrate, while both of them are much larger than that on the textured Si(100) substrate. The average grain sizes (about 10-50 nm) of the ZnO grown on the different silicon substrates decreases with the increase of their strains. These results are shown to strongly correlate with the results from the SEM, AFM, and CL as well. The reflectance spectra of these three samples show that the antireflection function provided by theses samples mostly results from the nanometer-scaled texture of the ZnO films, while the micrometer-scaled texture of the Si substrate has a limited contribution. The results of this work provide important information for optimized growth of textured and well-faceted ZnO grown on wafer-based silicon solar cells and can be utilized for efficiency enhancement and optimization of device materials and structures, such as heterojunction with intrinsic thin layer (HIT) solar cells.

Breaking symmetry in non-planar bifurcations: distribution of flow and wall shear stress.

PubMed

Lu, Yiling; Lu, Xiyun; Zhuang, Lixian; Wang, Wen

2002-01-01

Non-planarity in blood vessels is known to influence arterial flows and wall shear stress. To gain insight, computational fluid dynamics (CFD) has been used to investigate effects of curvature and out-of-plane geometry on the distribution of fluid flows and wall shear stresses in a hypothetical non-planar bifurcation. Three-dimensional Navier-Stokes equations for a steady state Newtonian fluid were solved numerically using a finite element method. Non-planarity in one of the two daughter vessels is found to deflect flow from the inner wall of the vessel to the outer wall and to cause changes in the distribution of wall shear stresses. Results from this study agree to experimental observations and CFD simulations in the literature, and support the view that non-planarity in blood vessels is a factor with important haemodynamic significance and may play a key role in vascular biology and pathophysiology.

Arabidopsis  SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity.

PubMed

Pietra, Stefano; Gustavsson, Anna; Kiefer, Christian; Kalmbach, Lothar; Hörstedt, Per; Ikeda, Yoshihisa; Stepanova, Anna N; Alonso, Jose M; Grebe, Markus

2013-01-01

The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes.

Fundamental and practical limits of planar tracking solar concentrators.

PubMed

Grede, Alex J; Price, Jared S; Giebink, Noel C

2016-12-26

Planar microtracking provides an alternate paradigm for solar concentration that offers the possibility of realizing high-efficiency embedded concentrating photovoltaic systems in the form factor of standard photovoltaic panels. Here, we investigate the thermodynamic limit of planar tracking optical concentrators and establish that they can, in principal, achieve the sine limit of their orientationally-tracked counterparts provided that the receiver translates a minimum distance set by the field of view half-angle. We develop a phase space methodology to optimize practical planar tracking concentrators and apply it to the design of a two surface, catadioptric system that operates with > 90% optical efficiency over a 140° field of view at geometric gains exceeding 1000×. These results provide a reference point for subsequent developments in the field and indicate that planar microtracking can achieve the high optical concentration ratio required in commercial concentrating photovoltaic systems.

Multi-projector auto-calibration and placement optimization for non-planar surfaces

NASA Astrophysics Data System (ADS)

Li, Dong; Xie, Jinghui; Zhao, Lu; Zhou, Lijing; Weng, Dongdong

2015-10-01

Non-planar projection has been widely applied in virtual reality and digital entertainment and exhibitions because of its flexible layout and immersive display effects. Compared with planar projection, a non-planar projection is more difficult to achieve because projector calibration and image distortion correction are difficult processes. This paper uses a cylindrical screen as an example to present a new method for automatically calibrating a multi-projector system in a non-planar environment without using 3D reconstruction. This method corrects the geometric calibration error caused by the screen's manufactured imperfections, such as an undulating surface or a slant in the vertical plane. In addition, based on actual projection demand, this paper presents the overall performance evaluation criteria for the multi-projector system. According to these criteria, we determined the optimal placement for the projectors. This method also extends to surfaces that can be parameterized, such as spheres, ellipsoids, and paraboloids, and demonstrates a broad applicability.

Synthesis of square-planar aluminum(III) complexes.

PubMed

Thompson, Emily J; Myers, Thomas W; Berben, Louise A

2014-12-15

The synthesis of two four-coordinate and square planar (SP) complexes of aluminum(III) is presented. Reaction of a phenyl-substituted bis(imino)pyridine ligand that is reduced by two electrons, Na2((Ph)I2P(2-)), with AlCl3 afforded five-coordinate [((Ph)I2P(2-))Al(THF)Cl] (1). Square-planar [((Ph)I2P(2-))AlCl] (2) was obtained by performing the same reaction in diethyl ether followed by lyphilization of 2 from benzene. The four-coordinate geometry index for 2, τ4, is 0.22, where 0 would be a perfectly square-planar molecule. The analogous aluminum hydride complex, [((Ph)I2P(2-))AlH] (3), is also square-planar, and was characterized crystallographically and has τ4=0.13. Both 2 and 3 are Lewis acidic and bind 2,6-lutidine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Non-planar microfabricated gas chromatography column

DOEpatents

Lewis, Patrick R.; Wheeler, David R.

2007-09-25

A non-planar microfabricated gas chromatography column comprises a planar substrate having a plurality of through holes, a top lid and a bottom lid bonded to opposite surfaces of the planar substrate, and inlet and outlet ports for injection of a sample gas and elution of separated analytes. A plurality of such planar substrates can be aligned and stacked to provide a longer column length having a small footprint. Furthermore, two or more separate channels can enable multi-channel or multi-dimensional gas chromatography. The through holes preferably have a circular cross section and can be coated with a stationary phase material or packed with a porous packing material. Importantly, uniform stationary phase coatings can be obtained and band broadening can be minimized with the circular channels. A heating or cooling element can be disposed on at least one of the lids to enable temperature programming of the column.

Factors controlling the size of graphene oxide sheets produced via the graphite oxide route.

PubMed

Pan, Shuyang; Aksay, Ilhan A

2011-05-24

We have studied the effect of the oxidation path and the mechanical energy input on the size of graphene oxide sheets derived from graphite oxide. The cross-planar oxidation of graphite from the (0002) plane results in periodic cracking of the uppermost graphene oxide layer, limiting its lateral dimension to less than 30 μm. We use an energy balance between the elastic strain energy associated with the undulation of graphene oxide sheets at the hydroxyl and epoxy sites, the crack formation energy, and the interaction energy between graphene layers to determine the cell size of the cracks. As the effective crack propagation rate in the cross-planar direction is an order of magnitude smaller than the edge-to-center oxidation rate, graphene oxide single sheets larger than those defined by the periodic cracking cell size are produced depending on the aspect ratio of the graphite particles. We also demonstrate that external energy input from hydrodynamic drag created by fluid motion or sonication, further reduces the size of the graphene oxide sheets through tensile stress buildup in the sheets.

Alternans and Spiral Breakup in an Excitable Reaction-Diffusion System: A Simulation Study

PubMed Central

Gani, M. Osman; Ogawa, Toshiyuki

2014-01-01

The determination of the mechanisms of spiral breakup in excitable media is still an open problem for researchers. In the context of cardiac electrophysiological activities, spiral breakup exhibits complex spatiotemporal pattern known as ventricular fibrillation. The latter is the major cause of sudden cardiac deaths all over the world. In this paper, we numerically study the instability of periodic planar traveling wave solution in two dimensions. The emergence of stable spiral pattern is observed in the considered model. This pattern occurs when the heart is malfunctioning (i.e., ventricular tachycardia). We show that the spiral wave breakup is a consequence of the transverse instability of the planar traveling wave solutions. The alternans, that is, the oscillation of pulse widths, is observed in our simulation results. Moreover, we calculate the widths of spiral pulses numerically and observe that the stable spiral pattern bifurcates to an oscillatory wave pattern in a one-parameter family of solutions. The spiral breakup occurs far below the bifurcation when the maximum and the minimum excited states become more distinct, and hence the alternans becomes more pronounced. PMID:27379274

Alternans and Spiral Breakup in an Excitable Reaction-Diffusion System: A Simulation Study.

PubMed

Gani, M Osman; Ogawa, Toshiyuki

2014-01-01

The determination of the mechanisms of spiral breakup in excitable media is still an open problem for researchers. In the context of cardiac electrophysiological activities, spiral breakup exhibits complex spatiotemporal pattern known as ventricular fibrillation. The latter is the major cause of sudden cardiac deaths all over the world. In this paper, we numerically study the instability of periodic planar traveling wave solution in two dimensions. The emergence of stable spiral pattern is observed in the considered model. This pattern occurs when the heart is malfunctioning (i.e., ventricular tachycardia). We show that the spiral wave breakup is a consequence of the transverse instability of the planar traveling wave solutions. The alternans, that is, the oscillation of pulse widths, is observed in our simulation results. Moreover, we calculate the widths of spiral pulses numerically and observe that the stable spiral pattern bifurcates to an oscillatory wave pattern in a one-parameter family of solutions. The spiral breakup occurs far below the bifurcation when the maximum and the minimum excited states become more distinct, and hence the alternans becomes more pronounced.

Cholesteric pitch transitions induced by mechanical strain.

PubMed

Lelidis, I; Barbero, G; Alexe-Ionescu, A L

2013-02-01

We investigate thickness and surface anchoring strength influence on pitch transitions in a planar cholesteric liquid crystal layer. The cholesteric-nematic transition is also investigated. We assume planar boundary conditions, with strong anchoring strength at one interface and weak anchoring strength at the other. The surface anchoring energy we consider to describe the deviation of the surface twist angle from the easy axis induced by a bulk deformation is a parabolic potential or Rapini and Papoular periodic potential, respectively. We show that under strain, all pitch transitions take place at a critical thickness that is equal to the quarter of the natural cholesteric pitch. The latter result does not depend on the anchoring strength, the particular surface potential, or material properties. The twist angle on the limiting surface characterized by weak anchoring varies with strain either by slipping and or in a discontinuous manner according to the thickness of the sample. The position of the bifurcation point depends only on the ratio of the extrapolation length over the layer thickness, but its value is model dependent. Multistability and multiplicity of the transition are discussed.

The invariant cleavage pattern displayed by ascidian embryos depends on spindle positioning along the cell's longest axis in the apical plane and relies on asynchronous cell divisions

PubMed Central

Dumollard, Rémi; Minc, Nicolas; Salez, Gregory; Aicha, Sameh Ben; Bekkouche, Faisal; Hebras, Céline; Besnardeau, Lydia; McDougall, Alex

2017-01-01

The ascidian embryo is an ideal system to investigate how cell position is determined during embryogenesis. Using 3D timelapse imaging and computational methods we analyzed the planar cell divisions in ascidian early embryos and found that spindles in every cell tend to align at metaphase in the long length of the apical surface except in cells undergoing unequal cleavage. Furthermore, the invariant and conserved cleavage pattern of ascidian embryos was found to consist in alternate planar cell divisions between ectoderm and endomesoderm. In order to test the importance of alternate cell divisions we manipulated zygotic transcription induced by β-catenin or downregulated wee1 activity, both of which abolish this cell cycle asynchrony. Crucially, abolishing cell cycle asynchrony consistently disrupted the spindle orienting mechanism underpinning the invariant cleavage pattern. Our results demonstrate how an evolutionary conserved cell cycle asynchrony maintains the invariant cleavage pattern driving morphogenesis of the ascidian blastula. DOI: http://dx.doi.org/10.7554/eLife.19290.001 PMID:28121291

Fabrication of silicon-embedded low resistance high-aspect ratio planar copper microcoils

NASA Astrophysics Data System (ADS)

Syed Mohammed, Zishan Ali; Puiu, Poenar Daniel; Aditya, Sheel

2018-01-01

Low resistance is an important requirement for microcoils which act as a signal receiver to ensure low thermal noise during signal detection. High-aspect ratio (HAR) planar microcoils entrenched in blind silicon trenches have features that make them more attractive than their traditional counterparts employing electroplating through a patterned thick polymer or achieved through silicon vias. However, challenges met in fabrication of such coils have not been discussed in detail until now. This paper reports the realization of such HAR microcoils embedded in Si blind trenches, fabricated with a single lithography step by first etching blind trenches in the silicon substrate with an aspect ratio of almost 3∶1 and then filling them up using copper electroplating. The electroplating was followed by chemical wet etching as a faster way of removing excess copper than traditional chemical mechanical polishing. Electrical resistance was further reduced by annealing the microcoils. The process steps and challenges faced in the realization of such structures are reported here followed by their electrical characterization. The obtained electrical resistances are then compared with those of other similar microcoils embedded in blind vias.

Coumarin benzothiazole derivatives as chemosensors for cyanide anions

NASA Astrophysics Data System (ADS)

Wang, Kangnan; Liu, Zhiqiang; Guan, Ruifang; Cao, Duxia; Chen, Hongyu; Shan, Yanyan; Wu, Qianqian; Xu, Yongxiao

2015-06-01

Four coumarin benzothiazole derivatives, N-(benzo[d]thiazol-2-yl)-2-oxo-2H-chromene-3-carboxamide (1), (Z)-N-(3-methylbenzo[d]thiazol-2(3H)-ylidene)-2-oxo-2H-chromene-3-carboxamide (2), 7-(diethylamino)-N-(benzo[d]thiazol-2-yl)-2-oxo-2H-chromene-3-carboxamide (3) and (Z)-7-(diethylamino)-N-(3-methylbenzo[d]thiazol-2(3H)-ylidene)-2-oxo-2H-chromene-3-carboxamide) (4), have been synthesized. Their crystal structures, photophysical properties in acetonitrile and recognition properties for cyanide anions have been investigated. All the compounds are generally planar, especially compound 1 exhibits perfect planarity with dihedral angle between benzothiazolyl group and coumarin group being only 3.63°. Coumarin benzothiazole compounds 1 and 3 can recognize cyanide anions by Michael addition reaction and compound 3 exhibits color change from yellow to colorless and green fluorescence was quenched completely, which can be observed by naked eye. Coumarin benzothiazolyliden compound 4 can recognize cyanide anions with fluorescence turn-on response based on the copper complex ensemble displacement mechanism.

Investigating and understanding fouling in a planar setup using ultrasonic methods.

PubMed

Wallhäusser, E; Hussein, M A; Becker, T

2012-09-01

Fouling is an unwanted deposit on heat transfer surfaces and occurs regularly in foodstuff heat exchangers. Fouling causes high costs because cleaning of heat exchangers has to be carried out and cleaning success cannot easily be monitored. Thus, used cleaning cycles in foodstuff industry are usually too long leading to high costs. In this paper, a setup is described with which it is possible, first, to produce dairy protein fouling similar to the one found in industrial heat exchangers and, second, to detect the presence and absence of such fouling using an ultrasonic based measuring method. The developed setup resembles a planar heat exchanger in which fouling can be made and cleaned reproducible. Fouling presence, absence, and cleaning progress can be monitored by using an ultrasonic detection unit. The setup is described theoretically based on electrical and mechanical lumped circuits to derive the wave equation and the transfer function to perform a sensitivity analysis. Sensitivity analysis was done to determine influencing quantities and showed that fouling is measurable. Also, first experimental results are compared with results from sensitivity analysis.

Ultrafast exciton migration in an HJ-aggregate: Potential surfaces and quantum dynamics

NASA Astrophysics Data System (ADS)

Binder, Robert; Polkehn, Matthias; Ma, Tianji; Burghardt, Irene

2017-01-01

Quantum dynamical and electronic structure calculations are combined to investigate the mechanism of exciton migration in an oligothiophene HJ aggregate, i.e., a combination of oligomer chains (J-type aggregates) and stacked aggregates of such chains (H-type aggregates). To this end, a Frenkel exciton model is parametrized by a recently introduced procedure [Binder et al., J. Chem. Phys. 141, 014101 (2014)] which uses oligomer excited-state calculations to perform an exact, point-wise mapping of coupled potential energy surfaces to an effective Frenkel model. Based upon this parametrization, the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method is employed to investigate ultrafast dynamics of exciton transfer in a small, asymmetric HJ aggregate model composed of 30 sites and 30 active modes. For a partially delocalized initial condition, it is shown that a torsional defect confines the trapped initial exciton, and planarization induces an ultrafast resonant transition between an HJ-aggregated segment and a covalently bound "dangling chain" end. This model is a minimal realization of experimentally investigated mixed systems exhibiting ultrafast exciton transfer between aggregated, highly planarized chains and neighboring disordered segments.

Design and Evaluation of a Scalable and Reconfigurable Multi-Platform System for Acoustic Imaging

PubMed Central

Izquierdo, Alberto; Villacorta, Juan José; del Val Puente, Lara; Suárez, Luis

2016-01-01

This paper proposes a scalable and multi-platform framework for signal acquisition and processing, which allows for the generation of acoustic images using planar arrays of MEMS (Micro-Electro-Mechanical Systems) microphones with low development and deployment costs. Acoustic characterization of MEMS sensors was performed, and the beam pattern of a module, based on an 8 × 8 planar array and of several clusters of modules, was obtained. A flexible framework, formed by an FPGA, an embedded processor, a computer desktop, and a graphic processing unit, was defined. The processing times of the algorithms used to obtain the acoustic images, including signal processing and wideband beamforming via FFT, were evaluated in each subsystem of the framework. Based on this analysis, three frameworks are proposed, defined by the specific subsystems used and the algorithms shared. Finally, a set of acoustic images obtained from sound reflected from a person are presented as a case study in the field of biometric identification. These results reveal the feasibility of the proposed system. PMID:27727174

Shock tube Multiphase Experiments

NASA Astrophysics Data System (ADS)

Middlebrooks, John; Allen, Roy; Paudel, Manoj; Young, Calvin; Musick, Ben; McFarland, Jacob

2017-11-01

Shock driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching practical applications in engineering and science. The instability is present in high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase interface is impulsively accelerated by the passage of a shockwave. It is similar in development to the Richtmyer-Meshkov (RM) instability however, particle-to-gas coupling is the driving mechanism of the SDMI. As particle effects such as lag and phase change become more prominent, the SDMI's development begins to significantly deviate from the RM instability. We have developed an experiment for studying the SDMI in our shock tube facility. In our experiments, a multiphase interface is created using a laminar jet and flowed into the shock tube where it is accelerated by the passage of a planar shockwave. The interface development is captured using CCD cameras synchronized with planar laser illumination. This talk will give an overview of new experiments conducted to examine the development of a shocked cylindrical multiphase interface. The effects of Atwood number, particle size, and a second acceleration (reshock) of the interface will be discussed.

Improving ex vivo skin permeation of non-steroidal anti-inflammatory drugs: enhancing extemporaneous transformation of liposomes into planar lipid bilayers.

PubMed

Vázquez-González, Martha L; Bernad, Rafael; Calpena, Ana C; Domènech, Oscar; Montero, M T; Hernández-Borrell, Jordi

2014-01-30

Transdermal delivery of active principles is a versatile method widely used in medicine. The main drawback for the transdermal route, however, is the low efficiency achieved in the absorption of many drugs, mostly due to the complexity of the skin barrier. To improve drug delivery through the skin, we prepared and characterized liposomes loaded with ibuprofen and designed pharmaceutical formulations based on the extemporaneous addition of penetration enhancer (PE) surfactants. Afterwards, permeation and release studies were carried out. According to the permeation studies, the ibuprofen liposomal formulation supplemented with PEs exhibited similar therapeutic effects, but at lower doses (20%) comparing with a commercial formulation used as a reference. Atomic force microscopy (AFM) was used to investigate the effect caused by PEs on the adsorption mechanism of liposomal formulations onto the skin. Non-fused liposomes, bilayers and multilayered lipid structures were observed. The transformation of vesicles into planar structures is proposed as a possible rationale for explaining the lower doses required when a liposome formulation is supplemented with surfactant PEs. Copyright © 2013 Elsevier B.V. All rights reserved.

The signalling receptor MCAM coordinates apical-basal polarity and planar cell polarity during morphogenesis

PubMed Central

Gao, Qian; Zhang, Junfeng; Wang, Xiumei; Liu, Ying; He, Rongqiao; Liu, Xingfeng; Wang, Fei; Feng, Jing; Yang, Dongling; Wang, Zhaoqing; Meng, Anming; Yan, Xiyun

2017-01-01

The apical–basal (AB) polarity and planar cell polarity (PCP) provide an animal cell population with different phenotypes during morphogenesis. However, how cells couple these two patterning systems remains unclear. Here we provide in vivo evidence that melanoma cell adhesion molecule (MCAM) coordinates AB polarity-driven lumenogenesis and c-Jun N-terminal kinase (JNK)/PCP-dependent ciliogenesis. We identify that MCAM is an independent receptor of fibroblast growth factor 4 (FGF4), a membrane anchor of phospholipase C-γ (PLC-γ), an immediate upstream receptor of nuclear factor of activated T-cells (NFAT) and a constitutive activator of JNK. We find that MCAM-mediated vesicular trafficking towards FGF4, while generating a priority-grade transcriptional response of NFAT determines lumenogenesis. We demonstrate that MCAM plays indispensable roles in ciliogenesis through activating JNK independently of FGF signals. Furthermore, mcam-deficient zebrafish and Xenopus exhibit a global defect in left-right (LR) asymmetric establishment as a result of morphogenetic failure of their LR organizers. Therefore, MCAM coordination of AB polarity and PCP provides insight into the general mechanisms of morphogenesis. PMID:28589943

Planar cell polarity signaling in the uterus directs appropriate positioning of the crypt for embryo implantation

PubMed Central

Yuan, Jia; Cha, Jeeyeon; Deng, Wenbo; Bartos, Amanda; Sun, Xiaofei; Ho, Hsin-Yi Henry; Borg, Jean-Paul; Yamaguchi, Terry P.; Yang, Yingzi; Dey, Sudhansu K.

2016-01-01

Blastocyst implantation is a complex process requiring coordination of a dynamic sequence of embryo–uterine interactions. Blood vessels enter the uterus from the mesometrium, demarcating the uterus into mesometrial (M) and antimesometrial (AM) domains. Implantation occurs along the uterine longitudinal axis within specialized implantation chambers (crypts) that originate within the evaginations directed from the primary lumen toward the AM domain. The morphological orientation of crypts in rodent uteri was recognized more than a century ago, but the mechanism remained unknown. Here we provide evidence that planar cell polarity (PCP) signaling orchestrates directed epithelial evaginations to form crypts for implantation in mice. Uterine deletion of Vang-like protein 2, but not Vang-like protein 1, conferred aberrant PCP signaling, misdirected epithelial evaginations, defective crypt formation, and blastocyst attachment, leading to severely compromised pregnancy outcomes. The study reveals a previously unrecognized role for PCP in executing spatial cues for crypt formation and implantation. Because PCP is an evolutionarily conserved phenomenon, our study is likely to inspire implantation studies of this signaling pathway in humans and other species. PMID:27911818

Tyrocidine A Analogues Bearing the Planar d-Phe-2-Abz Turn Motif: How Conformation Impacts Bioactivity.

PubMed

Cameron, Alan J; Edwards, Patrick J B; Harjes, Elena; Sarojini, Vijayalekshmi

2017-12-14

The d-Phe-Pro β-turn of the cyclic β-hairpin antimicrobial decapeptide tyrocidine A, (Tyrc A) was substituted with the d-Phe-2-aminobenzoic acid (2-Abz) motif in a synthetic analogue (1). The NMR structure of 1 demonstrated that compound 1 retained the β-hairpin structure of Tyrc A with additional planarity, resulting in approximately 30-fold reduced hemolysis than Tyrc A. Although antibacterial activity was partially compromised, a single Gln to Lys substitution (2) restored activity equivalent to Tyrc A against S. aureus, enhanced activity against two Gram negative strains and maintained the reduced hemeloysis of 1. Analysis by transmission electron microscopy (TEM) suggested a membrane lytic mechanism of action for these peptides. Compound 2 also exhibits nanomolar antifungal activity in synergy with amphotericin B. The d-Phe-2-Abz turn may serve as a tool for the synthesis of structurally predictable β-hairpin libraries. Unlike traditional β-turn motifs such as d-Pro-Gly, both the 2-Abz and d-Phe rings may be further functionalized.

Optics and Nonlinear Buckling Mechanics in Large-Area, Highly Stretchable Arrays of Plasmonic Nanostructures.

PubMed

Gao, Li; Zhang, Yihui; Zhang, Hui; Doshay, Sage; Xie, Xu; Luo, Hongying; Shah, Deesha; Shi, Yan; Xu, Siyi; Fang, Hui; Fan, Jonathan A; Nordlander, Peter; Huang, Yonggang; Rogers, John A

2015-06-23

Large-scale, dense arrays of plasmonic nanodisks on low-modulus, high-elongation elastomeric substrates represent a class of tunable optical systems, with reversible ability to shift key optical resonances over a range of nearly 600 nm at near-infrared wavelengths. At the most extreme levels of mechanical deformation (strains >100%), nonlinear buckling processes transform initially planar arrays into three-dimensional configurations, in which the nanodisks rotate out of the plane to form linear arrays with "wavy" geometries. Analytical, finite-element, and finite-difference time-domain models capture not only the physics of these buckling processes, including all of the observed modes, but also the quantitative effects of these deformations on the plasmonic responses. The results have relevance to mechanically tunable optical systems, particularly to soft optical sensors that integrate on or in the human body.

Supracolloidal fullerene-like cages: design principles and formation mechanisms.

PubMed

Li, Zhan-Wei; Zhu, You-Liang; Lu, Zhong-Yuan; Sun, Zhao-Yan

2016-11-30

How to create novel desired structures by rational design of building blocks represents a significant challenge in materials science. Here we report a conceptually new design principle for creating supracolloidal fullerene-like cages through the self-assembly of soft patchy particles interacting via directional nonbonded interactions by mimicking non-planar sp 2 hybridized carbon atoms in C 60 . Our numerical investigations demonstrate that the rational design of patch configuration, size, and interaction can drive soft three-patch particles to reversibly self-assemble into a vast collection of supracolloidal fullerene-like cages. We further elucidate the formation mechanisms of supracolloidal fullerene-like cages by analyzing the structural characteristics and the formation process. Our results provide conceptual and practical guidance towards the experimental realization of supracolloidal fullerene-like cages, as well as a new perspective on understanding the fullerene formation mechanisms.

Dimensional effects on the magnetic domains in planar magnetophotonic crystal waveguides

NASA Astrophysics Data System (ADS)

Huang, Xiaoyue

2007-05-01

The application of photonic crystal technology in magneto-optic media can yield significant improvements in polarization rotation efficiency and optical switching capability and an overall reduction in magneto-optic device dimensions. Resonant photonic crystal structures in planar ferrimagnetic film waveguides are of interest because they may lead to the development of on-chip magneto-optical switches and isolators for photonic device integration. In the present work, two different methods for the fabrication of on-chip waveguide magnetophotonic crystals, through electron beam lithography and focused ion beam milling, are discussed and demonstrated. A high precision photonic measurement system was set up for testing and analysis of the waveguide devices. The results obtained show photonic band gaps with resonant transmission in the gap, and enhanced magneto-optic rotation efficiency. The character of waveguide modes therein, birefringence effects, and structural variation effects were studied extensively and are presented in this thesis. Planar magnetization control produced by manipulation of the magnetic shape anisotropy in the photonic crystal micro-cavity was demonstrated in this work. By introducing strip structures into the resonant cavity formed on magnetic garnet films with in-plane anisotropy, a bi-stable magnetic state and an enhanced magnetic field reversal mechanism were demonstrated. This effect was extensively studied through experimental and micromagnetic simulation analysis of the polarization rotation hysteresis. The results discussed herein show that domain closure loops between the strips limit the magnification of the coercivity in the resonant cavity and that these limitations can be overcome by the formation of isolated single-domain magnetic microstrips in the cavity.

Stability of Molasse: TLS for structural analysis in the valley of Gotteron-Fribourg, Switzerland

NASA Astrophysics Data System (ADS)

Ben Hammouda, Mariam; Jaboyedoff, Michel; Derron, Marc Henri; Bouaziz, Samir; Mazotti, Benoit

2016-04-01

The marine molasses of Fribourg (Switzerland) is an area where the cliff collapses and rockfalls are quite frequent and difficult to predict due to this particular lithology, a poorly consolidated greywacke. Because of some recent rockfall events, the situation became critical especially in the valley of Gotteron where a big block has slightly moved down and might destroy a house in case of rupture. The cliff made of jointed sandstone and thin layers of clay and siltstone presents many fractures, joints and massive cross bedding surfaces which increases the possibility of slab failure. This paper presents a detailed structural analysis of the cliff and the identification of the potential failure mechanisms. The methodology is about combining field observation and terrestrial LiDAR scanning point cloud in order to assess the stability of potential slope instabilities of molasses. Three LiDAR scans were done i) to extract discontinuity families depending to the dip and the dip direction of joints and ii) to run kinematic tests in order to identify responsible sets for each potential failure mechanisms. Raw point clouds were processed using IMAlign module of Polyworks and CloudCompare software. The structural analysis based on COLTOP 3D (Jaboyedoff et al. 2007) allowed the identification of four discontinuity sets that were not measured in the field. Two different failure mechanisms have been identified as critical: i) planar sliding which is the main responsible mechanism of the present fallen block and ii) wedge sliding. The planar sliding is defined by the discontinuity sets J1 and J5 with a direction parallel to the slope and with a steep dip angle. The wedges, defined by couples of discontinuity sets, contribute to increase cracks' opening and to the detachment of slabs. The use of TLS combined with field survey provides us a first interpretation of instabilities and a very promising structural analysis.

Process Of Bonding A Metal Brush Structure To A Planar Surface Of A Metal Substrate

DOEpatents

Slattery, Kevin T.; Driemeyer, Daniel E.; Wille; Gerald W.

1999-11-02

Process for bonding a metal brush structure to a planar surface of a metal substrate in which an array of metal rods are retained and immobilized at their tips by a common retention layer formed of metal, and the brush structure is then joined to a planar surface of a metal substrate via the retention layer.

Multi-Layer Tiled Array.

DTIC Science & Technology

1996-12-16

the Invention 13 The present invention relates to planar sonar arrays. More 14 particularly, the invention relates to the arrangement of 15...transducer elements in planar sonar arrays. 16 (2) Description of the Prior Art 17 Conventional planar sonar array designs typically comprise 18 ceramic...signal 5 conditioners ( preamplifiers )/as short as possible. However, this 6 requirement complicates fabrication and provides little space to 7

Transition Metal d-Orbital Splitting Diagrams: An Updated Educational Resource for Square Planar Transition Metal Complexes

ERIC Educational Resources Information Center

Bo¨rgel, Jonas; Campbell, Michael G.; Ritter, Tobias

2016-01-01

The presentation of d-orbital splitting diagrams for square planar transition metal complexes in textbooks and educational materials is often inconsistent and therefore confusing for students. Here we provide a concise summary of the key features of orbital splitting diagrams for square planar complexes, which we propose may be used as an updated…

Planar Poincare chart - A planar graphic representation of the state of light polarization

NASA Technical Reports Server (NTRS)

Tedjojuwono, Ken K.; Hunter, William W., Jr.; Ocheltree, Stewart L.

1989-01-01

The planar Poincare chart, which represents the complete planar equivalence of the Poincare sphere, is proposed. The four sets of basic lines are drawn on two separate charts for the generalization and convenience of reading the scale. The chart indicates the rotation of the principal axes of linear birefringent material. The relationships between parameters of the two charts are given as 2xi-2phi (orientation angle of the major axis-ellipticity angle) pair and 2alpha-delta (angle of amplitude ratio-phase difference angle) pair. The results are useful for designing and analyzing polarization properties of optical components with birefringent properties.

Piezo Voltage Controlled Planar Hall Effect Devices

PubMed Central

Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K. W.; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

2016-01-01

The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials. PMID:27329068

Piezo Voltage Controlled Planar Hall Effect Devices.

PubMed

Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K W; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

2016-06-22

The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

Contact planarization of ensemble nanowires

NASA Astrophysics Data System (ADS)

Chia, A. C. E.; LaPierre, R. R.

2011-06-01

The viability of four organic polymers (S1808, SC200, SU8 and Cyclotene) as filling materials to achieve planarization of ensemble nanowire arrays is reported. Analysis of the porosity, surface roughness and thermal stability of each filling material was performed. Sonication was used as an effective method to remove the tops of the nanowires (NWs) to achieve complete planarization. Ensemble nanowire devices were fully fabricated and I-V measurements confirmed that Cyclotene effectively planarizes the NWs while still serving the role as an insulating layer between the top and bottom contacts. These processes and analysis can be easily implemented into future characterization and fabrication of ensemble NWs for optoelectronic device applications.

Contact planarization of ensemble nanowires.

PubMed

Chia, A C E; LaPierre, R R

2011-06-17

The viability of four organic polymers (S1808, SC200, SU8 and Cyclotene) as filling materials to achieve planarization of ensemble nanowire arrays is reported. Analysis of the porosity, surface roughness and thermal stability of each filling material was performed. Sonication was used as an effective method to remove the tops of the nanowires (NWs) to achieve complete planarization. Ensemble nanowire devices were fully fabricated and I-V measurements confirmed that Cyclotene effectively planarizes the NWs while still serving the role as an insulating layer between the top and bottom contacts. These processes and analysis can be easily implemented into future characterization and fabrication of ensemble NWs for optoelectronic device applications.

Planar Cell Polarity Pathway – Coordinating morphogenetic cell behaviors with embryonic polarity

PubMed Central

Gray, Ryan S.; Roszko, Isabelle; Solnica-Krezel, Lilianna

2011-01-01

Planar cell polarization entails establishment of cellular asymmetries within the tissue plane. An evolutionarily conserved Planar Cell Polarity (PCP) signaling system employs intra- and intercellular feedback interactions between its core components, including Frizzled, Van Gogh, Flamingo, Prickle and Dishevelled, to establish their characteristic asymmetric intracellular distributions and coordinate planar polarity of cell populations. By translating global patterning information into asymmetries of cell membranes and intracellular organelles, PCP signaling coordinates morphogenetic behaviors of individual cells and cell populations with the embryonic polarity. In vertebrates, by polarizing cilia in the node/Kupffer’s vesicle, PCP signaling links the anteroposterior to left-right embryonic polarity. PMID:21763613

Technology of silicon charged-particle detectors developed at the Institute of Electron Technology (ITE)

NASA Astrophysics Data System (ADS)

Wegrzecka, Iwona; Panas, Andrzej; Bar, Jan; Budzyński, Tadeusz; Grabiec, Piotr; Kozłowski, Roman; Sarnecki, Jerzy; Słysz, Wojciech; Szmigiel, Dariusz; Wegrzecki, Maciej; Zaborowski, Michał

2013-07-01

The paper discusses the technology of silicon charged-particle detectors developed at the Institute of Electron Technology (ITE). The developed technology enables the fabrication of both planar and epiplanar p+-ν-n+ detector structures with an active area of up to 50 cm2. The starting material for epiplanar structures are silicon wafers with a high-resistivity n-type epitaxial layer ( ν layer - ρ < 3 kΩcm) deposited on a highly doped n+-type substrate (ρ< 0,02Ωcm) developed and fabricated at the Institute of Electronic Materials Technology. Active layer thickness of the epiplanar detectors (νlayer) may range from 10 μm to 150 μm. Imported silicon with min. 5 kΩcm resistivity is used to fabricate planar detectors. Active layer thickness of the planar detectors (ν) layer) may range from 200 μm to 1 mm. This technology enables the fabrication of both discrete and multi-junction detectors (monolithic detector arrays), such as single-sided strip detectors (epiplanar and planar) and double-sided strip detectors (planar). Examples of process diagrams for fabrication of the epiplanar and planar detectors are presented in the paper, and selected technological processes are discussed.

Photodegradation of Selected PCBs in the Presence of Nano-TiO2 as Catalyst and H2O2 as an Oxidant

PubMed Central

Dasary, Samuel S. R.; Saloni, Julia; Fletcher, Amanda; Anjaneyulu, Yerramilli; Yu, Hongtao

2010-01-01

Photodegradation of five strategically selected PCBs was carried out in acetonitrile/water 80:20. Quantum chemical calculations reveal that PCBs without any chlorine on ortho-positions are closer to be planar, while PCBs with at least one chlorine atoms at the ortho-positions causes the two benzene rings to be nearly perpendicular. Light-induced degradation of planar PCBs is much slower than the perpendicular ones. The use of nano-TiO2 speeds up the degradation of the planar PCBs, but slows down the degradation of the non-planar ones. The use of H2O2 speeds up the degradation of planar PCBs greatly (by >20 times), but has little effect on non-planar ones except 2,3,5,6-TCB. The relative photodegradation rate is: 2,2′,4,4′-TCB > 2,3,5,6-TCB > 2,6-DCB ≈ 3,3′,4,4′-TCB > 3,4′,5-TCB. The use of H2O2 in combination with sunlight irradiation could be an efficient and “green” technology for PCB remediation. PMID:21139872

Design, fabrication, and performance analysis of GaN vertical electron transistors with a buried p/n junction

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

Yeluri, Ramya, E-mail: ramyay@ece.ucsb.edu; Lu, Jing; Keller, Stacia

2015-05-04

The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9 kA/cm{sup 2}) and low ON-resistance (0.4 mΩ cm{sup 2}) are demonstrated. Non-planar selective area regrowth is identified as the limiting factormore » to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown voltage with high current will enable GaN vertical transistors with high power densities.« less

Development of a simple MR-compatible vibrotactile stimulator using a planar-coil-type actuator.

PubMed

Kim, Hyung-Sik; Choi, Mi-Hyun; Chung, Yoon-Gi; Kim, Sung-Phil; Jun, Jae-Hoon; Park, Jang-Yeon; Yi, Jeong-Han; Park, Jong-Rak; Lim, Dae-Woon; Chung, Soon-Cheol

2013-06-01

For this study, we developed a magnetic resonance (MR)-compatible vibrotactile stimulator using a planar-coil-type actuator. The newly developed vibrotactile stimulator consists of three units: control unit, drive unit, and planar-coil-type actuator. The control unit controls frequency, intensity, time, and channel, and transfers the stimulation signals to the drive unit. The drive unit operates the planar-coil-type actuator in response to commands from the control unit. The planar-coil-type actuator, which uses a planar coil instead of conventional electric wire, generates vibrating stimulation through interaction of the current of the planar coil with the static magnetic field of the MR scanner. Even though the developed tactile stimulating system is small, simple, and inexpensive, it has a wide range of stimulation frequencies (20 ~ 400 Hz, at 40 levels) and stimulation intensities (0 ~ 7 V, at 256 levels). The stimulation intensity does not change due to frequency changes. Since the transient response time is a few microseconds, the stimulation time can be controlled on a scale of microseconds. In addition, this actuator has the advantages of providing highly repeatable stimulation, being durable, being able to assume various shapes, and having an adjustable contact area with the skin. The new stimulator operated stably in an MR environment without affecting the MR images. Using functional magnetic resonance imaging, we observed the brain activation changes resulting from stimulation frequency and intensity changes.

Integrated Optics for Planar imaging and Optical Signal Processing

NASA Astrophysics Data System (ADS)

Song, Qi

Silicon photonics is a subject of growing interest with the potential of delivering planar electro-optical devices with chip scale integration. Silicon-on-insulator (SOI) technology has provided a marvelous platform for photonics industry because of its advantages in integration capability in CMOS circuit and countless nonlinearity applications in optical signal processing. This thesis is focused on the investigation of planar imaging techniques on SOI platform and potential applications in ultra-fast optical signal processing. In the first part, a general review and background introduction about integrated photonics circuit and planar imaging technique are provided. In chapter 2, planar imaging platform is realized by a silicon photodiode on SOI chip. Silicon photodiode on waveguide provides a high numerical aperture for an imaging transceiver pixel. An erbium doped Y2O3 particle is excited by 1550nm Laser and the fluorescent image is obtained with assistance of the scanning system. Fluorescence image is reconstructed by using image de-convolution technique. Under photovoltaic mode, we use an on-chip photodiode and an external PIN photodiode to realize similar resolution as 5μm. In chapter 3, a time stretching technique is developed to a spatial domain to realize a 2D imaging system as an ultrafast imaging tool. The system is evaluated based on theoretical calculation. The experimental results are shown for a verification of system capability to imaging a micron size particle or a finger print. Meanwhile, dynamic information for a moving object is also achieved by correlation algorithm. In chapter 4, the optical leaky wave antenna based on SOI waveguide has been utilized for imaging applications and extensive numerical studied has been conducted. and the theoretical explanation is supported by leaky wave theory. The highly directive radiation has been obtained from the broadside with 15.7 dB directivity and a 3dB beam width of ΔØ 3dB ≈ 1.65° in free space environment when β -1 = 2.409 × 105/m, α=4.576 ×103/m. At the end, electronics beam-steering principle has been studied and the comprehensive model has been built to explain carrier transformation behavior in a PIN junction as individual silicon perturbation. Results show that 1019/cm3 is possible obtained with electron injection mechanism. Although the radiation modulation based on carrier injection of 1019/cm3 gives 0.5dB variation, resonant structure, such as Fabry Perrot Cavity, can be integrated with LOWAs to enhance modulation effect.

Percolation effect in thick film superconductors

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

Sali, R.; Harsanyi, G.

1994-12-31

A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to high T{sub c} and advantageous current density properties the base of the paste was chosen to be of Bi(Pb)SrCaCuO system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density atmore » the boiling temperature of the liquid He- was between 200-300 A/cm{sup 2}. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency and the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.« less

Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy.

PubMed

Pan, Jianjun; Sahoo, Prasana K; Dalzini, Annalisa; Hayati, Zahra; Aryal, Chinta M; Teng, Peng; Cai, Jianfeng; Rodriguez Gutierrez, Humberto; Song, Likai

2017-05-18

A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with the membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. A force spectroscopy experiment shows that PrP106-126 reduces Young's modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid atomic vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intrachain conformation, while the interchain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the interchain interaction, while the intrachain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs.

Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy

PubMed Central

Pan, Jianjun; Sahoo, Prasana K.; Dalzini, Annalisa; Hayati, Zahra; Aryal, Chinta M.; Teng, Peng; Cai, Jianfeng; Gutierrez, Humberto Rodriguez; Song, Likai

2018-01-01

A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. Force spectroscopy experiment shows that PrP106-126 reduces Young’s modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intra-chain conformation, while the inter-chain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the inter-chain interaction, while the intra-chain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs. PMID:28459565

Analysis and Synthesis of Leaky-Wave Devices in Planar Technology

NASA Astrophysics Data System (ADS)

Martinez Ros, Alejandro Javier

The work developed along this doctoral thesis has been focused on the analysis and synthesis of microwave devices in planar technology. In particular, several types of devices based on the radiation mechanism of leaky waves have been studied. Typically, the radiation properties in leaky-wave devices are determined by the complex propagation constant of the leaky mode, wherein the phase constant is responsible for the pointing angle and the leakage rate for the intensity of the radiated fields. In this manner, by controlling both amplitude and phase of the leaky mode, an effective control over the device's radiation diagram can be obtained. Moreover, with the purpose of efficiently obtaining the leaky mode's radiation properties as function of the main geometrical parameters of the structure, several modal tools based on the transverse resonance analysis of the structure have been performed. In order to demonstrate this simultaneous control over the complex propagation constant in planar technology, several types of leaky-wave devices, including antennas (LWAs), multiplexors and near-field focusing systems, have been designed and manufactured in the technology of substrate integrated waveguide (SIW). This recently proposed technology, allows the design of devices based on classical waveguide technology with standard manufacturing techniques used for printed circuit board (PCB) designs. In this way, most of the parts that form a communication system can be integrated into a single substrate, thus reducing its cost and providing a more robust and compact device, which has less losses compared to other planar technologies such as the microstrip. El trabajo llevado a cabo durante la realizacion de esta tesis doctoral, se ha centrado en el analisis y sintesis de dispositivos de microondas en tecnologia planar. En concreto, se han estudiado diferentes tipos de dispositivos basados en radiacion por ondas de fuga "leaky waves", en los cuales las propiedades de radiacion estan determinadas por la constante de fase del modo "leaky" que es el que determina el angulo de apuntamiento y por la tasa de radiacion que es la que determina la intensidad de los campos radiados. De esta manera, controlando en amplitud y fase el modo "leaky" se puede obtener un control efectivo sobre el diagrama de radiacion del dispositivo. Ademas, con el objetivo de poder obtener de una manera mas eficiente las caracteristicas de propagacion de los modos de fuga "leaky" en funcion de los principales parametros geometricos de la estructura, se han desarrollado diversas herramientas de analisis modal basadas en la tecnica de resonancia transversa de la estructura. La capacidad para obtener un control simultaneo de la constante de propagacion compleja del modo "leaky", ha sido demostrada mediante el diseno y fabricacion de varios tipos de antena "leaky wave" (LWA) y de otros dispositivos como multiplexores y sistemas de enfoque en campo cercano. Para ello, se ha utilizado la tecnologia planar de guia de onda integrada en sustrato (susbstrate integrated waveguide, SIW). Esta recientemente desarrollada tecnologia, permite disenar dispositivos de microondas basados en tecnologia clasica de guia de ondas con sistemas de fabricacion estandar usados en tecnologia de circuitos impresos (printed circuit board, PCB). De esta forma, se pueden integrar en un mismo sustrato muchas de las diferentes partes que forman un sistema de comunicaciones, mejorando asi su robustez y compactibilidad, ademas de reducir el coste y de contar con menores perdidas que otras tecnologias planares como la microstrip.

Optimization design and dynamic analysis on the drive mechanisms of flapping-wing air vehicles based on flapping trajectories

NASA Astrophysics Data System (ADS)

Xie, Lingwang; Zhang, Xingwei; Luo, Pan; Huang, Panpan

2017-10-01

The optimization designs and dynamic analysis on the driving mechanism of flapping-wing air vehicles on base of flapping trajectory patterns is carried out in this study. Three different driving mechanisms which are spatial double crank-rocker, plane five-bar and gear-double slider, are systematically optimized and analysed by using the Mat lab and Adams software. After a series debugging on the parameter, the comparatively ideal flapping trajectories are obtained by the simulation of Adams. Present results indicate that different drive mechanisms output different flapping trajectories and have their unique characteristic. The spatial double crank-rocker mechanism can only output the arc flapping trajectory and it has the advantages of small volume, high flexibility and efficient space utilization. Both planar five-bar mechanism and gear-double slider mechanism can output the oval, figure of eight and double eight flapping trajectories. Nevertheless, the gear-double slider mechanism has the advantage of convenient parameter setting and better performance in output double eight flapping trajectory. This study can provide theoretical basis and helpful reference for the design of the drive mechanisms of flapping-wing air vehicles with different output flapping trajectories.

A field-cancellation algorithm for constructing economical planar permanent magnet (PM) multipoles with large high-quality field apertures

NASA Astrophysics Data System (ADS)

Tatchyn, Roman

1997-05-01

In recent years studies have been initiated on a new class of multipole field generators consisting of cuboid planar permanent magnet (PM) pieces arranged in bi-planar arrays of 2-fold rotational symmetry(R. Tatchyn, "Planar Permanent Magnet Multipoles: for Particle Accelerator and Storage Ring Applications ," IEEE Trans. Mag. 30, 5050(1994).)(T. Cremer, R. Tatchyn, "Planar Permanent Magnet Multipoles: Measurements and Configurations," in Proceedings of the 1995 Particle Accelerator Conference, IEEE Catalog No. 95CH35843, paper FAQ-20.). These structures, first introduced for Free Electron Laser (FEL) applications(R. Tatchyn, "Selected applications of planar permanent magnet multipoles in FEL insertion device design," NIM A341, 449(1994).), are based on reducing the rotational symmetry of conventional N-pole field generators from N-fold to 2-fold. One consequence of this reduction is a large higher-multipole content in a planar PM multipole's field at distances relatively close to the structure's axis, making it generally unsuitable for applications requiring a large high-quality field aperture. In this paper we outline an economical field-cancellation algorithm that can substantially decrease the harmonic content of a planar PM's field without breaking its biplanar geometry or 2-fold rotational symmetry. This will enable planar PM multipoles to be employed in a broader range of applications than heretofore possible, in particular as distributed focusing elements installed in insertion device gaps on synchrotron storage rings. This accomplishment is expected to remove the conventional restriction of an insertion device's length to the scale of the local focusing beta, enabling short-period, small-gap undulators to be installed and operated as high-brightness sources on lower-energy storage rings(R. Tatchyn, P. Csonka, A. Toor, "Perspectives on micropole undulators in synchrotron radiation technology," Rev. Sci. Instrum. 60(7), 1796(1989).). Operation as ordinary focusing elements in storage ring magnetic lattices, as well as the performance of other high-quality multipole applications, should also becomes possible with the realization of the proposed structures.

Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water

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

Lau, Gabriel V.; Müller, Erich A.; Jackson, George

2015-03-21

The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derivedmore » for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large system sizes for both the cylindrical and spherical cases. Estimates of the entropic and energetic contributions are also evaluated for the planar and cylindrical geometries and their magnitudes are in line with the expectations of our simple analysis.« less

A magnetic resonance (MR) microscopy system using a microfluidically cryo-cooled planar coil.

PubMed

Koo, Chiwan; Godley, Richard F; Park, Jaewon; McDougall, Mary P; Wright, Steven M; Han, Arum

2011-07-07

We present the development of a microfluidically cryo-cooled planar coil for magnetic resonance (MR) microscopy. Cryogenically cooling radiofrequency (RF) coils for magnetic resonance imaging (MRI) can improve the signal to noise ratio (SNR) of the experiment. Conventional cryostats typically use a vacuum gap to keep samples to be imaged, especially biological samples, at or near room temperature during cryo-cooling. This limits how close a cryo-cooled coil can be placed to the sample. At the same time, a small coil-to-sample distance significantly improves the MR imaging capability due to the limited imaging depth of planar MR microcoils. These two conflicting requirements pose challenges to the use of cryo-cooling in MR microcoils. The use of a microfluidic based cryostat for localized cryo-cooling of MR microcoils is a step towards eliminating these constraints. The system presented here consists of planar receive-only coils with integrated cryo-cooling microfluidic channels underneath, and an imaging surface on top of the planar coils separated by a thin nitrogen gas gap. Polymer microfluidic channel structures fabricated through soft lithography processes were used to flow liquid nitrogen under the coils in order to cryo-cool the planar coils to liquid nitrogen temperature (-196 °C). Two unique features of the cryo-cooling system minimize the distance between the coil and the sample: (1) the small dimension of the polymer microfluidic channel enables localized cooling of the planar coils, while minimizing thermal effects on the nearby imaging surface. (2) The imaging surface is separated from the cryo-cooled planar coil by a thin gap through which nitrogen gas flows to thermally insulate the imaging surface, keeping it above 0 °C and preventing potential damage to biological samples. The localized cooling effect was validated by simulations, bench testing, and MR imaging experiments. Using this cryo-cooled planar coil system inside a 4.7 Tesla MR system resulted in an average image SNR enhancement of 1.47 ± 0.11 times relative to similar room-temperature coils. This journal is © The Royal Society of Chemistry 2011

A Magnetic Resonance (MR) Microscopy System using a Microfluidically Cryo-Cooled Planar Coil

PubMed Central

Koo, Chiwan; Godley, Richard F.; Park, Jaewon; McDougall, Mary P.; Wright, Steven M.; Han, Arum

2011-01-01

We present the development of a microfluidically cryo-cooled planar coil for magnetic resonance (MR) microscopy. Cryogenically cooling radiofrequency (RF) coils for magnetic resonance imaging (MRI) can improve the signal to noise ratio (SNR) of the experiment. Conventional cryostats typically use a vacuum gap to keep samples to be imaged, especially biological samples, at or near room temperature during cryo-cooling. This limits how close a cryo-cooled coil can be placed to the sample. At the same time, a small coil-to-sample distance significantly improves the MR imaging capability due to the limited imaging depth of planar MR microcoils. These two conflicting requirements pose challenges to the use of cryo-cooling in MR microcoils. The use of a microfluidic based cryostat for localized cryo-cooling of MR microcoils is a step towards eliminating these constraints. The system presented here consists of planar receive-only coils with integrated cryo-cooling microfluidic channels underneath, and an imaging surface on top of the planar coils separated by a thin nitrogen gas gap. Polymer microfluidic channel structures fabricated through soft lithography processes were used to flow liquid nitrogen under the coils in order to cryo-cool the planar coils to liquid nitrogen temperature (−196°C). Two unique features of the cryo-cooling system minimize the distance between the coil and the sample: 1) The small dimension of the polymer microfluidic channel enables localized cooling of the planar coils, while minimizing thermal effects on the nearby imaging surface. 2) The imaging surface is separated from the cryo-cooled planar coil by a thin gap through which nitrogen gas flows to thermally insulate the imaging surface, keeping it above 0°C and preventing potential damage to biological samples. The localized cooling effect was validated by simulations, bench testing, and MR imaging experiments. Using this cryo-cooled planar coil system inside a 4.7 Tesla MR system resulted in an average image SNR enhancement of 1.47 ± 0.11 times relative to similar room-temperature coils. PMID:21603723

On the mechanochemical theory of biological pattern formation with application to vasculogenesis.

PubMed

Murray, James D

2003-02-01

We first describe the Murray-Oster mechanical theory of pattern formation, the biological basis of which is experimentally well documented. The model quantifies the interaction of cells and the extracellular matrix via the cell-generated forces. The model framework is described in quantitative detail. Vascular endothelial cells, when cultured on gelled basement membrane matrix, rapidly aggregate into clusters while deforming the matrix into a network of cord-like structures tessellating the planar culture. We apply the mechanical theory of pattern formation to this culture system and show that neither strain-biased anisotropic cell traction nor cell migration are necessary for pattern formation: isotropic, strain-stimulated cell traction is sufficient to form the observed patterns. Predictions from the model were confirmed experimentally.

Seven-pass transmembrane cadherins: roles and emerging mechanisms in axonal and dendritic patterning.

PubMed

Berger-Müller, Sandra; Suzuki, Takashi

2011-12-01

The Flamingo/Celsr seven-transmembrane cadherins represent a conserved subgroup of the cadherin superfamily involved in multiple aspects of development. In the developing nervous system, Fmi/Celsr control axonal blueprint and dendritic morphogenesis from invertebrates to mammals. As expected from their molecular structure, seven-transmembrane cadherins can induce cell-cell homophilic interactions but also intracellular signaling. Fmi/Celsr is known to regulate planar cell polarity (PCP) through interactions with PCP proteins. In the nervous system, Fmi/Celsr can function in collaboration with or independently of other PCP genes. Here, we focus on recent studies which show that seven-transmembrane cadherins use distinct molecular mechanisms to achieve diverse functions in the development of the nervous system.

Mechanism of equivalent electric dipole oscillation for high-order harmonic generation from grating-structured solid-surface by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Wang, Yang; Song, Hai-Ying; Liu, H. Y.; Liu, Shi-Bing

2017-07-01

We theoretically study high-order harmonic generation (HHG) from relativistically driven overdense plasma targets with rectangularly grating-structured surfaces by femtosecond laser pulses. Our particle-in-cell (PIC) simulations show that, under the conditions of low laser intensity and plasma density, the harmonics emit principally along small angles deviating from the target surface. Further investigation of the surface electron dynamics reveals that the electron bunches are formed by the interaction between the laser field and the target surface, giving rise to the oscillation of equivalent electric-dipole (OEED), which enhances specific harmonic orders. Our work helps understand the mechanism of harmonic emissions from grating targets and the distinction from the planar harmonic scheme.

IVUS-Based Computational Modeling and Planar Biaxial Artery Material Properties for Human Coronary Plaque Vulnerability Assessment

PubMed Central

Liu, Haofei; Cai, Mingchao; Yang, Chun; Zheng, Jie; Bach, Richard; Kural, Mehmet H.; Billiar, Kristen L.; Muccigrosso, David; Lu, Dongsi; Tang, Dalin

2012-01-01

Image-based computational modeling has been introduced for vulnerable atherosclerotic plaques to identify critical mechanical conditions which may be used for better plaque assessment and rupture predictions. In vivo patient-specific coronary plaque models are lagging due to limitations on non-invasive image resolution, flow data, and vessel material properties. A framework is proposed to combine intravascular ultrasound (IVUS) imaging, biaxial mechanical testing and computational modeling with fluid-structure interactions and anisotropic material properties to acquire better and more complete plaque data and make more accurate plaque vulnerability assessment and predictions. Impact of pre-shrink-stretch process, vessel curvature and high blood pressure on stress, strain, flow velocity and flow maximum principal shear stress was investigated. PMID:22428362

Vortex structure and breakup mechanism of gaseous jet in supersonic crossflow with laminar boundary layer

NASA Astrophysics Data System (ADS)

Zhao, Yanhui; Liang, Jianhan; Zhao, Yuxin

2016-11-01

Employing nano-particle planar laser scattering and particle image velocimetry technology, underexpanded jet in supersonic crossflow with laminar boundary layer is experimental investigated in a low noise wind tunnel. Instantaneous flow structures and average velocity distribution of jet plume are captured in experimental images. Horseshoe vortex system is dominated by oscillating and coalescing regime, contributing to vortex generation of jet shear layer. The "tilting-stretching-tearing" mechanism dominating in near field raises average fractal dimension. But vortex structures generated on the windward side of jet plume scatter in jet plume and dissipate gradually, which makes the vortexes break up from outside in near field and break down into small turbulence completely in far field.

The properties of Ge quantum rings deposited by pulsed laser deposition.

PubMed

Ma, Xiying

2010-07-01

SiGe ring-shape nanostructures have attracted much research interest because of the interesting morphology, mechanical, and electromagnetic properties. In this paper, we present the planar Ge nanorings with well-defined sharp edges self-assembled on Si (100) matrix prepared with pulsed laser deposition (PLD) in the present of Ar gas. The transforming mechanism of the droplets is discussed, which a dynamic deformation model has been developed to simulate the self-transforming process of the droplets. The rings were found to be formed in two steps: from droplets to cones and from cones to rings via an elastic self-deforming process, which were likely to be driven by the lateral strain of Ge/Si layers and the surface tension.

Nanomechanical resonators based on group IV element monolayers

NASA Astrophysics Data System (ADS)

He, Ji-Dong; Sun, Jia-Sheng; Jiang, Jin-Wu

2018-04-01

We perform molecular dynamics simulations to investigate the energy dissipation of the resonant oscillation for the group IV monolayers of puckered configuration, in which the oscillation is driven with different actuation velocities. We find that, in the moderate actuation velocity regime, the nonlinear coupling between the resonant oscillation mode and other high-frequency modes will lead to the non-resonant motion of the system. For the larger actuation velocity, the effective strain generated during the resonant oscillating causes a structural transition from the puckered configuration into the planar configuration, which is a characteristic energy dissipation mechanism for the resonant oscillation of these group IV puckered monolayers. Our findings shed light on mechanical applications of the group IV monolayers in the nanomechanical resonator field.

Enhanced and tunable electric dipole-dipole interactions near a planar metal film

NASA Astrophysics Data System (ADS)

Zhou, Lei-Ming; Yao, Pei-Jun; Zhao, Nan; Sun, Fang-Wen

2017-08-01

We investigate the enhanced electric dipole-dipole interaction of surface plasmon polaritons (SPPs) supported by a planar metal film waveguide. By taking two nitrogen-vacancy (NV) center electric dipoles in diamond as an example, both the coupling strength and collective relaxation of two dipoles are studied with the numerical Green Function method. Compared to two-dipole coupling on a planar surface, metal film provides stronger and tunable coupling coefficients. Enhancement of the interaction between coupled NV center dipoles could have applications in both quantum information and energy transfer investigation. Our investigation provides systematic results for experimental applications based on a dipole-dipole interaction mediated with SPPs on a planar metal film.

Study of curved and planar frequency-selective surfaces with nonplanar illumination

NASA Technical Reports Server (NTRS)

Caroglanian, Armen; Webb, Kevin J.

1991-01-01

A locally planar technique (LPT) is investigated for determining the forward-scattered field from a generally shaped inductive frequency-selective surface (FSS) with nonplanar illumination. The results of an experimental study are presented to assess the LPT accuracy. The effects of a nonplanar incident field are determined by comparing the LPT numerical results with a series of experiments with the feed source placed at varying distances from the planar FSS. The limitations of the LPT model due to surface curvature are investigated in an experimental study of the scattered fields from a set of hyperbolic cylinders of different curvatures. From these comparisons, guidelines for applying the locally planar technique are developed.

Conservation of Planar Polarity Pathway Function Across the Animal Kingdom.

PubMed

Hale, Rosalind; Strutt, David

2015-01-01

Planar polarity is a well-studied phenomenon resulting in the directional coordination of cells in the plane of a tissue. In invertebrates and vertebrates, planar polarity is established and maintained by the largely independent core and Fat/Dachsous/Four-jointed (Ft-Ds-Fj) pathways. Loss of function of these pathways can result in a wide range of developmental or cellular defects, including failure of gastrulation and problems with placement and function of cilia. This review discusses the conservation of these pathways across the animal kingdom. The lack of vital core pathway components in basal metazoans suggests that the core planar polarity pathway evolved shortly after, but not necessarily alongside, the emergence of multicellularity.

On the origin of planarity in Al5- and Al5 clusters: The importance of a four-center peripheral bond

NASA Astrophysics Data System (ADS)

Geske, Grant D.; Boldyrev, Alexander I.; Li, Xi; Wang, Lai-Sheng

2000-10-01

Ab initio calculations were combined with anion photoelectron spectroscopy to unravel the structural origin of Al5 and Al5-. Well-resolved photoelectron spectra of Al5- were obtained and compared to theoretical calculations performed at various levels of theory. It was shown that the best agreement between the experimental and theoretical data is for a planar C2v structure. Analyses of the electronic structure and molecular orbitals revealed that the planarity in Al5 and Al5- are due to the presence of a four-center peripheral bond that is common in a whole family of planar pentaatomic species recently uncovered.

Summing Feynman graphs by Monte Carlo: Planar ϕ3-theory and dynamically triangulated random surfaces

NASA Astrophysics Data System (ADS)

Boulatov, D. V.; Kazakov, V. A.

1988-12-01

New combinatorial identities are suggested relating the ratio of (n - 1)th and nth orders of (planar) perturbation expansion for any quantity to some average over the ensemble of all planar graphs of the nth order. These identities are used for Monte Carlo calculation of critical exponents γstr (string susceptibility) in planar ϕ3-theory and in the dynamically triangulated random surface (DTRS) model near the convergence circle for various dimensions. In the solvable case D = 1 the exact critical properties of the theory are reproduced numerically. After August 3, 1988 the address will be: Cybernetics Council, Academy of Science, ul. Vavilova 40, 117333 Moscow, USSR.

Apparatus for checking the direction of polarization of shear-wave ultrasonic transducers

DOEpatents

Karplus, Henry H. B.

1980-01-01

An apparatus for checking the direction of polarization of shear-wave ultrasonic transducers comprises a first planar surface for mounting the shear-wave transducer, a second planar surface inclined at a predetermined angle to the first surface to generate longitudinal waves by mode conversion, and a third planar surface disposed at a second predetermined angle to the first for mounting a longitudinal-wave ultrasonic transducer. In an alternate embodiment, two second planar surfaces at the predetermined angle are placed at an angle to each other. The magnitude of the shear wave is a function of the angle between the direction of polarization of the transducer and the mode-conversion surface.

Apparatus for checking the direction of polarization of shear-wave ultrasonic transducers

DOEpatents

Karplus, H.H.B.; Forster, G.A.

An apparatus for checking the direction of polarization of shear-wave ultrasonic transducers comprises a first planar surface for mounting the shear-wave transducer, a second planar surface inclined at a predetermined angle to the first surface to generate longitudinal waves by mode conversion, and a third planar surface disposed at a second predetermined angle to the first for mounting a longitudinal-wave ultransonic transducer. In an alternate embodiment, two second planar surfaces at the predetermined angle are placed at an angle to each other. The magnitude of the shear wave is a function of the angle between the direction of polarization of the transducer and the mode-conversion surface.

Non-planar one-loop Parke-Taylor factors in the CHY approach for quadratic propagators

NASA Astrophysics Data System (ADS)

Ahmadiniaz, Naser; Gomez, Humberto; Lopez-Arcos, Cristhiam

2018-05-01

In this work we have studied the Kleiss-Kuijf relations for the recently introduced Parke-Taylor factors at one-loop in the CHY approach, that reproduce quadratic Feynman propagators. By doing this, we were able to identify the non-planar one-loop Parke-Taylor factors. In order to check that, in fact, these new factors can describe non-planar amplitudes, we applied them to the bi-adjoint Φ3 theory. As a byproduct, we found a new type of graphs that we called the non-planar CHY-graphs. These graphs encode all the information for the subleading order at one-loop, and there is not an equivalent of these in the Feynman formalism.

Arabidopsis  SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity

PubMed Central

Pietra, Stefano; Gustavsson, Anna; Kiefer, Christian; Kalmbach, Lothar; Hörstedt, Per; Ikeda, Yoshihisa; Stepanova, Anna N.; Alonso, Jose M.; Grebe, Markus

2013-01-01

The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes. PMID:24240534

Revealing the planar chemistry of two-dimensional heterostructures at the atomic level.

PubMed

Chou, Harry; Ismach, Ariel; Ghosh, Rudresh; Ruoff, Rodney S; Dolocan, Andrei

2015-06-23

Two-dimensional (2D) atomic crystals and their heterostructures are an intense area of study owing to their unique properties that result from structural planar confinement. Intrinsically, the performance of a planar vertical device is linked to the quality of its 2D components and their interfaces, therefore requiring characterization tools that can reveal both its planar chemistry and morphology. Here, we propose a characterization methodology combining (micro-) Raman spectroscopy, atomic force microscopy and time-of-flight secondary ion mass spectrometry to provide structural information, morphology and planar chemical composition at virtually the atomic level, aimed specifically at studying 2D vertical heterostructures. As an example system, a graphene-on-h-BN heterostructure is analysed to reveal, with an unprecedented level of detail, the subtle chemistry and interactions within its layer structure that can be assigned to specific fabrication steps. Such detailed chemical information is of crucial importance for the complete integration of 2D heterostructures into functional devices.

Hydrogenated arsenenes as planar magnet and Dirac material

NASA Astrophysics Data System (ADS)

Zhang, Shengli; Hu, Yonghong; Hu, Ziyu; Cai, Bo; Zeng, Haibo

2015-07-01

Arsenene and antimonene are predicted to have 2.49 and 2.28 eV band gaps, which have aroused intense interest in the two-dimensional (2D) semiconductors for nanoelectronic and optoelectronic devices. Here, the hydrogenated arsenenes are reported to be planar magnet and 2D Dirac materials based on comprehensive first-principles calculations. The semi-hydrogenated (SH) arsenene is found to be a quasi-planar magnet, while the fully hydrogenated (FH) arsenene is a planar Dirac material. The buckling height of pristine arsenene is greatly decreased by the hydrogenation, resulting in a planar and relatively low-mass-density sheet. The electronic structures of arsenene are also evidently altered after hydrogenating from wide-band-gap semiconductor to metallic material for SH arsenene, and then to Dirac material for FH arsenene. The SH arsenene has an obvious magnetism, mainly contributed by the p orbital of the unsaturated As atom. Such magnetic and Dirac materials modified by hydrogenation of arsenene may have potential applications in future optoelectronic and spintronic devices.

Planar micromixer

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

Fiechtner, Gregory J; Singh, Anup K; Wiedenman, Boyd J

2008-03-18

The present embodiment describes a laminar-mixing embodiment that utilizes simple, three-dimensional injection. Also described is the use of the embodiment in combination with wide and shallow sections of channel to affect rapid mixing in microanalytical systems. The shallow channel sections are constructed using all planar micromachining techniques, including those based on isotropic etching. The planar construction enables design using minimum dispersion concepts that, in turn, enable simultaneous mixing and injection into subsequent chromatography channels.

Photovoltaic Cell Having A P-Type Polycrystalline Layer With Large Crystals

DOEpatents

Albright, Scot P.; Chamberlin, Rhodes R.

1996-03-26

A photovoltaic cell has an n-type polycrystalline layer and a p-type polycrystalline layer adjoining the n-type polycrystalline layer to form a photovoltaic junction. The p-type polycrystalline layer comprises a substantially planar layer portion having relatively large crystals adjoining the n-type polycrystalline layer. The planar layer portion includes oxidized impurities which contribute to obtainment of p-type electrical properties in the planar layer portion.

Planar photovoltaic solar concentrator module

DOEpatents

Chiang, Clement J.

1992-01-01

A planar photovoltaic concentrator module for producing an electrical signal from incident solar radiation includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor.

Planar photovoltaic solar concentrator module

DOEpatents

Chiang, C.J.

1992-12-01

A planar photovoltaic concentrator module for producing an electrical signal from incident solar radiation includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor. 5 figs.

Enhanced ionic conductivity in planar sodium-β"-alumina electrolyte for electrochemical energy storage applications.

PubMed

La Rosa, Daniela; Monforte, Giuseppe; D'Urso, Claudia; Baglio, Vincenzo; Antonucci, Vincenzo; Aricò, Antonino S

2010-12-17

Solid Na-β"-Al₂O₃ electrolyte is prepared by a simple chemical route involving a pseudo-boehmite precursor and thermal treatment. Boehmite powder is used for manufacturing the planar electrolyte with appropriate bulk density after firing at 1500 °C. The structure, morphology, and surface properties of precursor powders and sintered electrolytes are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). As shown by XRD and TEM analyses, nanometer-sized particles are obtained for the boehmite precursor and a pure crystallographic phase is achieved for the sintered electrolyte. SEM analysis of the cross-section indicates good sintering characteristics. XPS shows a higher Na/Al atomic ratio on the surface for the planar electrolyte compared to a commercial tubular electrolyte (0.57 vs. 0.46). Energy-dispersive X-ray microanalysis (EDX) shows an Na/Al ratio in the bulk of 0.16, similar in the two samples. The ionic conductivity of the planar electrolyte is larger than that measured on a commercial tube of sodium-β"-alumina in a wide temperature range. At 350 °C, conductivity values of 0.5 S cm⁻¹ and 0.26 S cm⁻¹ are obtained for the planar electrolyte and the commercial tube, respectively. AC-impedance spectra show smaller grain boundary effects in the planar electrolyte than in the tubular electrolyte. These favorable properties may increase the perspectives for applying planar Na-β"-Al₂O₃ electrolytes in high-temperature batteries.

Stress concentration factors at saddle and crown positions on the central brace of two-planar welded CHS DKT-connections

NASA Astrophysics Data System (ADS)

Ahmadi, Hamid; Lotfollahi-Yaghin, Mohammad Ali; Aminfar, Mohammad H.

2012-03-01

A set of parametric stress analyses was carried out for two-planar tubular DKT-joints under different axial loading conditions. The analysis results were used to present general remarks on the effects of the geometrical parameters on stress concentration factors (SCFs) at the inner saddle, outer saddle, and crown positions on the central brace. Based on results of finite element (FE) analysis and through nonlinear regression analysis, a new set of SCF parametric equations was established for fatigue design purposes. An assessment study of equations was conducted against the experimental data and original SCF database. The satisfaction of acceptance criteria proposed by the UK Department of Energy (UK DoE) was also checked. Results of parametric study showed that highly remarkable differences exist between the SCF values in a multi-planar DKT-joint and the corresponding SCFs in an equivalent uni-planar KT-joint having the same geometrical properties. It can be clearly concluded from this observation that using the equations proposed for uni-planar KT-connections to compute the SCFs in multi-planar DKT-joints will lead to either considerably under-predicting or over-predicting results. Hence, it is necessary to develop SCF formulae specially designed for multi-planar DKT-joints. Good results of equation assessment according to UK DoE acceptance criteria, high values of correlation coefficients, and the satisfactory agreement between the predictions of the proposed equations and the experimental data guarantee the accuracy of the equations. Therefore, the developed equations can be reliably used for fatigue design of offshore structures.

Study of noise propagation and the effects of insufficient numbers of projection angles and detector samplings for iterative reconstruction using planar-integral data

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

Zhang, B.; Zeng, G. L.

2006-09-15

A rotating slat collimator can be used to acquire planar-integral data. It achieves higher geometric efficiency than a parallel-hole collimator by accepting more photons, but the planar-integral data contain less tomographic information that may result in larger noise amplification in the reconstruction. Lodge evaluated the rotating slat system and the parallel-hole system based on noise behavior for an FBP reconstruction. Here, we evaluate the noise propagation properties of the two collimation systems for iterative reconstruction. We extend Huesman's noise propagation analysis of the line-integral system to the planar-integral case, and show that approximately 2.0(D/dp) SPECT angles, 2.5(D/dp) self-spinning angles atmore » each detector position, and a 0.5dp detector sampling interval are required in order for the planar-integral data to be efficiently utilized. Here, D is the diameter of the object and dp is the linear dimension of the voxels that subdivide the object. The noise propagation behaviors of the two systems are then compared based on a least-square reconstruction using the ratio of the SNR in the image reconstructed using a planar-integral system to that reconstructed using a line-integral system. The ratio is found to be proportional to {radical}(F/D), where F is a geometric efficiency factor. This result has been verified by computer simulations. It confirms that for an iterative reconstruction, the noise tradeoff of the two systems is not only dependent on the increase of the geometric efficiency afforded by the planar projection method, but also dependent on the size of the object. The planar-integral system works better for small objects, while the line-integral system performs better for large ones. This result is consistent with Lodge's results based on the FBP method.« less

Investigation of short-circuit failure mechanisms of SiC MOSFETs by varying DC bus voltage

NASA Astrophysics Data System (ADS)

Namai, Masaki; An, Junjie; Yano, Hiroshi; Iwamuro, Noriyuki

2018-07-01

In this study, the experimental evaluation and numerical analysis of short-circuit mechanisms of 1200 V SiC planar and trench MOSFETs were conducted at various DC bus voltages from 400 to 800 V. Investigation of the impact of DC bus voltage on short-circuit capability yielded results that are extremely useful for many existing power electronics applications. Three failure mechanisms were identified in this study: thermal runaway, MOS channel current following device turn-off, and rupture of the gate oxide layer (gate oxide layer damage). The SiC MOSFETs experienced lattice temperatures exceeding 1000 K during the short-circuit transient; as Si insulated gate bipolar transistors (IGBTs) are not typically subject to such temperatures, the MOSFETs experienced distinct failure modes, and the mode experienced was significantly influenced by the DC bus voltage. In conclusion, suggestions regarding the SiC MOSFET design and operation methods that would enhance device robustness are proposed.

Mechanics of active surfaces

NASA Astrophysics Data System (ADS)

Salbreux, Guillaume; Jülicher, Frank

2017-09-01

We derive a fully covariant theory of the mechanics of active surfaces. This theory provides a framework for the study of active biological or chemical processes at surfaces, such as the cell cortex, the mechanics of epithelial tissues, or reconstituted active systems on surfaces. We introduce forces and torques acting on a surface, and derive the associated force balance conditions. We show that surfaces with in-plane rotational symmetry can have broken up-down, chiral, or planar-chiral symmetry. We discuss the rate of entropy production in the surface and write linear constitutive relations that satisfy the Onsager relations. We show that the bending modulus, the spontaneous curvature, and the surface tension of a passive surface are renormalized by active terms. Finally, we identify active terms which are not found in a passive theory and discuss examples of shape instabilities that are related to active processes in the surface.

Numerical and experimental analysis of an in-scale masonry cross-vault prototype up to failure

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

Rossi, Michela; Calderini, Chiara; Lagomarsino, Sergio

2015-12-31

A heterogeneous full 3D non-linear FE approach is validated against experimental results obtained on an in-scale masonry cross vault assembled with dry joints, and subjected to various loading conditions consisting on imposed displacement combinations to the abutments. The FE model relies into a discretization of the blocks by means of few rigid-infinitely resistant parallelepiped elements interacting by means of planar four-noded interfaces, where all the deformation (elastic and inelastic) occurs. The investigated response mechanisms of vault are the shear in-plane distortion and the longitudinal opening and closing mechanism at the abutments. After the validation of the approach on the experimentallymore » tested cross-vault, a sensitivity analysis is conducted on the same geometry, but in real scale, varying mortar joints mechanical properties, in order to furnish useful hints for safety assessment, especially in presence of seismic action.« less

Establishment of neurovascular congruency in the mouse whisker system by an independent patterning mechanism.

PubMed

Oh, Won-Jong; Gu, Chenghua

2013-10-16

Nerves and vessels often run parallel to one another, a phenomenon that reflects their functional interdependency. Previous studies have suggested that neurovascular congruency in planar tissues such as skin is established through a "one-patterns-the-other" model, in which either the nervous system or the vascular system precedes developmentally and then instructs the other system to form using its established architecture as a template. Here, we find that, in tissues with complex three-dimensional structures such as the mouse whisker system, neurovascular congruency does not follow the previous model but rather is established via a mechanism in which nerves and vessels are patterned independently. Given the diversity of neurovascular structures in different tissues, guidance signals emanating from a central organizer in the specific target tissue may act as an important mechanism to establish neurovascular congruency patterns that facilitate unique target tissue function. Copyright © 2013 Elsevier Inc. All rights reserved.

Geometric mechanics of periodic pleated origami.

PubMed

Wei, Z Y; Guo, Z V; Dudte, L; Liang, H Y; Mahadevan, L

2013-05-24

Origami structures are mechanical metamaterials with properties that arise almost exclusively from the geometry of the constituent folds and the constraint of piecewise isometric deformations. Here we characterize the geometry and planar and nonplanar effective elastic response of a simple periodically folded Miura-ori structure, which is composed of identical unit cells of mountain and valley folds with four-coordinated ridges, defined completely by two angles and two lengths. We show that the in-plane and out-of-plane Poisson's ratios are equal in magnitude, but opposite in sign, independent of material properties. Furthermore, we show that effective bending stiffness of the unit cell is singular, allowing us to characterize the two-dimensional deformation of a plate in terms of a one-dimensional theory. Finally, we solve the inverse design problem of determining the geometric parameters for the optimal geometric and mechanical response of these extreme structures.

Optimal trajectory generation for mechanical arms. M.S. Thesis

NASA Technical Reports Server (NTRS)

Iemenschot, J. A.

1972-01-01

A general method of generating optimal trajectories between an initial and a final position of an n degree of freedom manipulator arm with nonlinear equations of motion is proposed. The method is based on the assumption that the time history of each of the coordinates can be expanded in a series of simple time functions. By searching over the coefficients of the terms in the expansion, trajectories which minimize the value of a given cost function can be obtained. The method has been applied to a planar three degree of freedom arm.

Q factor of megahertz LC circuits based on thin films of YBaCuO high-temperature superconductor

NASA Astrophysics Data System (ADS)

Masterov, D. V.; Pavlov, S. A.; Parafin, A. E.

2008-05-01

High-frequency properties of resonant structures based on thin films of YBa2Cu3O7 δ high-temperature superconductor are studied experimentally in the frequency range 30 100 MHz. The structures planar induction coils with a self-capacitance fabricated on neodymium gallate and lanthanum aluminate substrates. The unloaded Q factor of the circuits exceeds 2 × 105 at 77 K and 40 MHz. Possible loss mechanisms that determine the Q factor of the superconducting resonant structures in the megahertz range are considered.

The mathematical modeling of rapid solidification processing. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Gutierrez-Miravete, E.

1986-01-01

The detailed formulation of and the results obtained from a continuum mechanics-based mathematical model of the planar flow melt spinning (PFMS) rapid solidification system are presented and discussed. The numerical algorithm proposed is capable of computing the cooling and freezing rates as well as the fluid flow and capillary phenomena which take place inside the molten puddle formed in the PFMS process. The FORTRAN listings of some of the most useful computer programs and a collection of appendices describing the basic equations used for the modeling are included.

Regulation of PCP by the Fat signaling pathway

PubMed Central

Matis, Maja; Axelrod, Jeffrey D.

2013-01-01

Planar cell polarity (PCP) in epithelia, orthogonal to the apical–basal axis, is essential for numerous developmental events and physiological functions. Drosophila model systems have been at the forefront of studies revealing insights into mechanisms regulating PCP and have revealed distinct signaling modules. One of these, involving the atypical cadherins Fat and Dachsous and the ectokinase Four-jointed, appears to link the direction of cell polarization to the tissue axes. We discuss models for the function of this signaling module as well as several unanswered questions that may guide future investigations. PMID:24142873