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Sample records for active twist control

  1. Acoustic Aspects of Active-Twist Rotor Control

    NASA Technical Reports Server (NTRS)

    Booth, Earl R., Jr.; Wilbur, Matthew L.

    2002-01-01

    The use of an Active Twist Rotor system to provide both vibration reduction and performance enhancement has been explored in recent analytical and experimental studies. Effects of active-twist control on rotor noise, however, had not been determined. During a recent wind tunnel test of an active-twist rotor system, a set of acoustic measurements were obtained to assess the effects of active-twist control on noise produced by the rotor, especially blade-vortex interaction (BVI) noise. It was found that for rotor operating conditions where BVI noise is dominant, active-twist control provided a reduction in BVI noise level. This BVI noise reduction was almost, but not quite, as large as that obtained in a similar test using HHC. However, vibration levels were usually adversely affected at operating conditions favoring minimum BVI noise. Conversely, operating conditions favoring minimum vibration levels affected BVI noise levels, but not always adversely.

  2. Active-Twist Rotor Control Applications for UAVs

    NASA Technical Reports Server (NTRS)

    Wilbur, Matthew L.; Wilkie, W. Keats

    2004-01-01

    The current state-of-the-art in active-twist rotor control is discussed using representative examples from analytical and experimental studies, and the application to rotary-wing UAVs is considered. Topics include vibration and noise reduction, rotor performance improvement, active blade tracking, stability augmentation, and rotor blade de-icing. A review of the current status of piezoelectric fiber composite actuator technology, the class of piezoelectric actuators implemented in active-twist rotor systems, is included.

  3. A Computational Study of BVI Noise Reduction Using Active Twist Control

    NASA Technical Reports Server (NTRS)

    Fogarty, David E.; Wilbur, Matthew L.; Sekula, Martin K.

    2010-01-01

    The results of a computational study examining the effects of active-twist control on blade-vortex interaction (BVI) noise using the Apache Active Twist Rotor are presented. The primary goal of this activity is to reduce BVI noise during a low-speed descent flight condition using active-twist control. Rotor aeroelastic behavior was modeled using the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics code and the rotor noise was predicted using the acoustics code PSU-WOPWOP. The accuracy of the analysis was validated through comparisons with experimental acoustic data for the first generation Active Twist Rotor at an advance ratio of mu=0.14. The application of active-twist to the main rotor blade system consisted of harmonic actuation frequencies ranging from 2P to 5P, control phase angles from 0' to 360 , and tip-twist amplitudes ranging from 0.5 to 4.0 . The acoustic analysis was conducted for a single low-speed flight condition of advance ratio =0.14 and shaft angle-of-attack, c^=+6 , with BVI noise levels predicted on a flat plane of observers located 1.1 rotor diameters beneath the rotor. The results indicated reductions of up to 11dB in BVI noise using 1.25 tip-twist amplitude with negligible effects on 4P vertical hub shear.

  4. Active twist control methodology for vibration reduction of a helicopter with dissimilar rotor system

    NASA Astrophysics Data System (ADS)

    Pawar, Prashant M.; Jung, Sung Nam

    2009-03-01

    In this work, an active vibration reduction of hingeless composite rotor blades with dissimilarity is investigated using the active twist concept and the optimal control theory. The induced shear strain on the actuation mechanism by the piezoelectric constant d15 from the PZN-8% PT-based single-crystal material is used to achieve more active twisting to suppress the extra vibrations. The optimal control algorithm is based on the minimization of an objective function comprised of quadratic functions of vibratory hub loads and voltage control harmonics. The blade-to-blade dissimilarity is modeled using the stiffness degradation of composite blades. The optimal controller is applied to various possible dissimilarities arising from different damage patterns of composite blades. The governing equations of motion are derived using Hamilton's principle. The effects of composite materials and smart actuators are incorporated into the comprehensive aeroelastic analysis system. Numerical results showing the impact of addressing the blade dissimilarities on hub vibrations and voltage inputs required to suppress the vibrations are demonstrated. It is observed that all vibratory shear forces are reduced considerably and the major harmonics of moments are reduced significantly. However, the controller needs further improvement to suppress 1/rev moment loads. A mechanism to achieve vibration reduction for the dissimilar rotor system has also been identified.

  5. The control of twisting somersaults.

    PubMed

    Yeadon, Maurice R; Hiley, Michael J

    2014-04-11

    In the takeoff and early flight phase of a twisting somersault, joint coordination is based on feed-forward control whereas in the late stages of the flight phase configuration adjustments are made using feedback control to ensure accurate completion of the movement and appropriate landing orientation. The aim of this study was to use a computer simulation model of aerial movement to investigate the extent to which arm and hip movements can control twist and somersault rotation in the flight phase of a twisting somersault. Two mechanisms were considered for the control of twist in simulated target trampoline movements with flight times of 1.4s. In the first case a single symmetrical arm adduction correction was made using delayed feedback control based on the difference between the twist rate in a perturbed simulation and the twist rate in a target movement comprising a forward somersault with 1½ twists. Final corrections were made using symmetrical arm abduction and hip flexion to adjust the twist and somersault angles. In the second case continual asymmetrical arm adduction/abduction adjustments were used to remove the tilt from a perturbed full twisting backward somersault using delayed feedback control based on twist angle and angular velocity. The first method was able to cope with perturbations to a forward somersault with 1½ twists providing the feedback time delay was less than 200 ms. The second method was able to correct a perturbed full twisting backward somersault providing the feedback time delay was less than 125 ms. PMID:24576588

  6. Means for controlling aerodynamically induced twist

    NASA Technical Reports Server (NTRS)

    Elber, W. (Inventor)

    1982-01-01

    A control mechanism which provides active compensation for aerodynamically induced twist deformation of high aspect ratio wings consists of a torque tube, internal to each wing and rigidly attached near the tip of each wing, which is moved by an actuator located in the aircraft fuselage. As changes in the aerodynamic loads on the wings occur the torque tube is rotated to compensate for the induced wing twist.

  7. The Twist Limit for Bipolar Active Regions

    NASA Technical Reports Server (NTRS)

    Moore, Ron; Falconer, David; Gary, Allen

    2008-01-01

    We present new evidence that further supports the standard idea that active regions are emerged magnetic-flux-rope omega loops. When the axial magnetic twist of a cylindrical flux rope exceeds a critical amount, the flux rope becomes unstable to kinking, and the excess axial twist is converted into writhe twist by the kinking. This suggests that, if active regions are emerged omega loops, then (1) no active region should have magnetic twist much above the limit set by kinking, (2) active regions having twist near the limit should often arise from kinked omega loops, and (3) since active regions having large delta sunspots are outstandingly twisted, these arise from kinked omega loops and should have twist near the limit for kinking. From each of 36 vector magnetograms of bipolar active regions, we have measured (1) the total flux of the vertical field above 100 G, (2) the area covered by this flux, and (3) the net electric current that arches over the polarity inversion line. These three quantities yield an estimate of the axial magnetic twist in a simple model cylindrical flux rope that corresponds to the top of the active region s hypothetical omega loop prior to emergence. In all 36 cases, the estimated twist is below the critical limit for kinking. The 11 most twisted active regions (1) have estimated twist within a factor of approx.3 of the limit, and (2) include all of our 6 active regions having large delta sunspots. Thus, our observed twist limit for bipolar active regions is in good accord with active regions being emerged omega loops.

  8. Aerodynamic Design Study of an Advanced Active Twist Rotor

    NASA Technical Reports Server (NTRS)

    Sekula, Martin K.; Wilbur, Matthew L.; Yeager, William T., Jr.

    2003-01-01

    An Advanced Active Twist Rotor (AATR) is currently being developed by the U.S. Army Vehicle Technology Directorate at NASA Langley Research Center. As a part of this effort, an analytical study was conducted to determine the impact of blade geometry on active-twist performance and, based on those findings, propose a candidate aerodynamic design for the AATR. The process began by creating a baseline design which combined the dynamic design of the original Active Twist Rotor and the aerodynamic design of a high lift rotor concept. The baseline model was used to conduct a series of parametric studies to examine the effect of linear blade twist and blade tip sweep, droop, and taper on active-twist performance. Rotor power requirements and hub vibration were also examined at flight conditions ranging from hover to advance ratio = 0.40. A total of 108 candidate designs were analyzed using the second-generation version of the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II) code. The study concluded that the vibration reduction capabilities of a rotor utilizing controlled, strain-induced twisting are enhanced through the incorporation of blade tip sweep, droop, and taper into the blade design, while they are degraded by increasing the nose-down linear blade twist. Based on the analysis of rotor power, hub vibration, and active-twist response, a candidate aerodynamic design for the AATR consisting of a blade with approximately 10 degrees of linear blade twist and a blade tip design with 30 degree sweep, 10 degree droop, and 2.5:1 taper ratio over the outer five percent of the blade is proposed.

  9. Dynamic response of active twist rotor blades

    NASA Astrophysics Data System (ADS)

    Cesnik, Carlos E. S.; Shin, Sang Joon; Wilbur, Matthew L.

    2001-02-01

    Dynamic characteristics of active twist rotor (ATR) blades are investigated analytically and experimentally in this paper. The ATR system is intended for vibration and potentially for noise reductions in helicopters through individual blade control. An aeroelastic model is developed to identify frequency response characteristics of the ATR blade with integral, generally anisotropic, strain actuators embedded in its composite construction. An ATR prototype blade was designed and manufactured to experimentally study the vibration reduction capabilities of such systems. Several bench and hover tests were conducted and those results are presented and discussed here. Selected results on sensitivity of the ATR system to collective setting (i.e. blade loading), blade rpm (i.e. centrifugal force and blade station velocity), and media density (i.e. altitude) are presented. They indicated that the twist actuation authority of the ATR blade is independent of the collective setting up to approximately 10P, and dependent on rotational speed and altitude near the torsional resonance frequency due to its dependency on the aerodynamic damping. The proposed model captures very well the physics and sensitivities to selected test parameters of the ATR system. The numerical result of the blade torsional loads show an average error of 20% in magnitude and virtually no difference in phase for the blade frequency response. Overall, the active blade model is in very good agreement with the experiments and can be used to analyze and design future active helicopter blade systems.

  10. A demonstration of passive blade twist control using extension-twist coupling

    NASA Technical Reports Server (NTRS)

    Lake, R. C.; Nixon, M. W.; Wilbur, M. L.; Singleton, J. D.; Mirick, P. H.

    1992-01-01

    The feasibility of passive blade twist control using an extension-twist-coupled composite rotor blade design has been demonstrated. A set of low-twist model-scale helicopter rotor blades has been manufactured from existing molds with the objective of demonstrating this control concept. Hover testing of the set of blades demonstrated maximum twist changes of 5.24 deg for the ballasted blade configuration, and 2.54 deg for the unballasted configurations in the atmospheric test condition. These results compared well with those obtained from a detailed FEM analysis of the rotor blade. Aerodynamic-induced effects on the blade elastic twist were found to be minimal.

  11. A demonstration of passive blade twist control using extension-twist coupling

    NASA Technical Reports Server (NTRS)

    Lake, Renee C.; Nixon, Mark W.; Wilbur, Matthew L.; Singleton, Jeffrey D.; Mirick, Paul H.

    1992-01-01

    The results from a study aimed at improving the dynamic and aerodynamic characteristics of composite rotor blades through the use of extension-twist coupling are presented. A set of low twist model-scale helicopter rotor blades was manufactured with a view towards demonstrating the passive blade twist control concept. Hover testing of the blades was conducted to measure the change in blade twist as a function of rotor speed. The blades were spun through the 0-800 rpm range, with a corresponding sweep of collective pitch to determine the effect on the blade elastic twist. Hover data were obtained for both a ballasted and unballasted blade configuration in atmospheric conditions, where maximum twist changes of 2.54 and 5.24 degrees were respectively observed. These results compared well with those from a finite element analysis of the blade, which yielded maximum twists of 3.01 and 5.61 degrees for the unballasted and ballasted blade configurations, respectively. The aerodynamic-induced effects on the blade elastic twist, determined by testing a ballasted blade configuration in a near-vacuum condition, were found to be minimal with a maximum twist difference of 0.17 degrees observed between the two test environments. The effect of collective pitch sweep on the elastic twist was minimal.

  12. Improvements to tilt rotor performance through passive blade twist control

    NASA Technical Reports Server (NTRS)

    Nixon, Mark W.

    1988-01-01

    A passive blade twist control is presented in which the twist distribution of a tilt rotor blade is elastically changed as a function of rotor speed. The elastic twist deformation is used to achieve two different blade twist distributions corresponding to the two rotor speeds used on conventional tilt rotors in hover and forward flight. By changing the blade twist distribution, the aerodynamic performance can be improved in both modes of flight. The concept presented obtains a change in twist distribution with extension-twist-coupled composite blade structure. This investigation first determines the linear twists which are optimum for each flight mode. Based on the optimum linear twist distributions, three extension-twist-coupled blade designs are developed using coupled-beam and laminate analyses integrated with an optimization analysis. The designs are optimized for maximum twist deformation subject to material strength limitations. The aerodynamic performances of the final designs are determined which show that the passive blade twist control concept is viable, and can enhance conventional tilt rotor performance.

  13. Design optimization for active twist rotor blades

    NASA Astrophysics Data System (ADS)

    Mok, Ji Won

    This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to

  14. Aeroelastic Analysis of the NASA/ARMY/MIT Active Twist Rotor

    NASA Technical Reports Server (NTRS)

    Wilkie, W. Keats; Wilbur, Matthew L.; Mirick, Paul H.; Cesnik, Carlos E. S.; Shin, Sangloon

    1999-01-01

    Aeroelastic modeling procedures used in the design of a piezoelectric controllable twist helicopter rotor wind tunnel model are described. Two aeroelastic analysis methods developed for active twist rotor studies, and used in the design of the model blade, are described in this paper. The first procedure uses a simple flap-torsion dynamic representation of the active twist blade, and is intended for rapid and efficient control law and design optimization studies. The second technique employs a commercially available comprehensive rotor analysis package, and is used for more detailed analytical studies. Analytical predictions of hovering flight twist actuation frequency responses are presented for both techniques. Forward flight fixed system nP vibration suppression capabilities of the model active twist rotor system are also presented. Frequency responses predicted using both analytical procedures agree qualitatively for all design cases considered, with best correlation for cases where uniform blade properties are assumed.

  15. Aeromechanical Evaluation of Smart-Twisting Active Rotor

    NASA Technical Reports Server (NTRS)

    Lim, Joon W.; Boyd, D. Douglas, Jr.; Hoffman, Frauke; van der Wall, Berend G.; Kim, Do-Hyung; Jung, Sung N.; You, Young H.; Tanabe, Yasutada; Bailly, Joelle; Lienard, Caroline; Delrieux, Yves

    2014-01-01

    An investigation of Smart-Twisting Active Rotor (STAR) was made to assess potential benefits of the current active twist rotor concept for performance improvement, vibration reduction, and noise alleviation. The STAR rotor is a 40% Mach-scaled, Bo105 rotor with an articulated flap-lag hinge at 3.5%R and no pre-cone. The 0-5 per rev active twist harmonic inputs were applied for various flight conditions including hover, descent, moderate to high speed level flights, and slowed rotor high advance ratio. For the analysis, the STAR partners used multiple codes including CAMRAD II, S4, HOST, rFlow3D, elsA, and their associated software. At the high thrust level in hover, the 0 per rev active twist with 80% amplitude increased figure of merit (FM) by 0.01-0.02 relative to the baseline. In descent, the largest BVI noise reduction was on the order of 2 to 5 dB at the 3 per rev active twist. In the high speed case (mu = 0.35), the 2 per rev actuation was found to be the most effective in achieving a power reduction as well as a vibration reduction. At the 2 per rev active twist, total power was reduced by 0.65% at the 60 deg active twist phase, and vibration was reduced by 47.6% at the 45 deg active twist phase. The use of the 2 per rev active twist appears effective for vibration reduction. In the high advance ratio case (mu = 0.70), the 0 per rev actuation appeared to have negligible impact on performance improvement. In summary, computational simulations successfully demonstrated that the current active twist concept provided a significant reduction of the maximum BVI noise in descent, a significant reduction of the vibration in the high speed case, a small improvement on rotor performance in hover, and a negligible impact on rotor performance in forward flight.

  16. Twist1 Is a TNF-Inducible Inhibitor of Clock Mediated Activation of Period Genes

    PubMed Central

    Meier, Daniel; Lopez, Martin; Franken, Paul; Fontana, Adriano

    2015-01-01

    Background Activation of the immune system affects the circadian clock. Tumor necrosis factor (TNF) and Interleukin (IL)-1β inhibit the expression of clock genes including Period (Per) genes and the PAR-bZip clock-controlled gene D-site albumin promoter-binding protein (Dbp). These effects are due to cytokine-induced interference of E-box mediated transcription of clock genes. In the present study we have assessed the two E-box binding transcriptional regulators Twist1 and Twist2 for their role in cytokine induced inhibition of clock genes. Methods The expression of the clock genes Per1, Per2, Per3 and of Dbp was assessed in NIH-3T3 mouse fibroblasts and the mouse hippocampal neuronal cell line HT22. Cells were treated for 4h with TNF and IL-1β. The functional role of Twist1 and Twist2 was assessed by siRNAs against the Twist genes and by overexpression of TWIST proteins. In luciferase (luc) assays NIH-3T3 cells were transfected with reporter gene constructs, which contain a 3xPer1 E-box or a Dbp E-box. Quantitative chromatin immunoprecipitation (ChIP) was performed using antibodies to TWIST1 and CLOCK, and the E-box consensus sequences of Dbp (CATGTG) and Per1 E-box (CACGTG). Results We report here that siRNA against Twist1 protects NIH-3T3 cells and HT22 cells from down-regulation of Period and Dbp by TNF and IL-1β. Overexpression of Twist1, but not of Twist2, mimics the effect of the cytokines. TNF down-regulates the activation of Per1-3xE-box-luc, the effect being prevented by siRNA against Twist1. Overexpression of Twist1, but not of Twist2, inhibits Per1-3xE-box-luc or Dbp-E-Box-luc activity. ChIP experiments show TWIST1 induction by TNF to compete with CLOCK binding to the E-box of Period genes and Dbp. Conclusion Twist1 plays a pivotal role in the TNF mediated suppression of E-box dependent transactivation of Period genes and Dbp. Thereby Twist1 may provide a link between the immune system and the circadian timing system. PMID:26361389

  17. Optimization of an Active Twist Rotor Blade Planform for Improved Active Response and Forward Flight Performance

    NASA Technical Reports Server (NTRS)

    Sekula, Martin K; Wilbur, Matthew L.

    2014-01-01

    A study was conducted to identify the optimum blade tip planform for a model-scale active twist rotor. The analysis identified blade tip design traits which simultaneously reduce rotor power of an unactuated rotor while leveraging aeromechanical couplings to tailor the active response of the blade. Optimizing the blade tip planform for minimum rotor power in forward flight provided a 5 percent improvement in performance compared to a rectangular blade tip, but reduced the vibration control authority of active twist actuation by 75 percent. Optimizing for maximum blade twist response increased the vibration control authority by 50 percent compared to the rectangular blade tip, with little effect on performance. Combined response and power optimization resulted in a blade tip design which provided similar vibration control authority to the rectangular blade tip, but with a 3.4 percent improvement in rotor performance in forward flight.

  18. Twist1 activity thresholds define multiple functions in limb development

    PubMed Central

    Krawchuk, Dayana; Weiner, Shoshana J.; Chen, You-Tzung; Lu, Benson; Costantini, Frank; Behringer, Richard R.; Laufer, Ed

    2010-01-01

    Summary The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1−/− embryos die at midgestation. However, studies on early limb buds found that Twist1−/− mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional alleles to generate a Twist1 allelic series that survives to birth. As Twist1 activity is reduced, limb skeletal defects progress from preaxial polydactyly to girdle reduction combined with hypoplasia, aplasia or mirror symmetry of all limb segments. With reduced Twist1 activity there is striking and progressive upregulation of ectopic Shh expression in the anterior of the limb, combined with an anterior shift in the posterior Shh domain, which is expressed at normal intensity, and loss of the posterior AER. Consequently limb outgrowth is initially impaired, before an ectopic anterior Shh domain expands the AER, promoting additional growth and repatterning. Reducing the dosage of FGF targets of the Etv gene family, which are known repressors of Shh expression in the anterior limb mesenchyme, strongly enhances the anterior skeletal phenotype. Conversely this and other phenotypes are suppressed by reducing the dosage of the Twist1 antagonist Hand2. Our data support a model whereby multiple Twist1 activity thresholds contribute to early limb bud patterning, and suggest how particular combinations of skeletal defects result from differing amounts of Twist1 activity. PMID:20732316

  19. High-Precision Twist-Controlled Bilayer and Trilayer Graphene.

    PubMed

    Chen, Xu-Dong; Xin, Wei; Jiang, Wen-Shuai; Liu, Zhi-Bo; Chen, Yongsheng; Tian, Jian-Guo

    2016-04-01

    Twist-controlled bilayer graphene (tBLG) and double-twisted trilayer graphene (DTTG) with high precision are fabricated and their controllable optoelectronic properties are investigated for the first time. The successful fabrication of tBLG and DTTG with designated θ provides an attractive starting point for systematic studies of interlayer coupling in misoriented few-layer graphene systems with well-defined geometry. PMID:26822255

  20. The control of non-twisting somersaults using configuration changes.

    PubMed

    Yeadon, M R; Mikulcik, E C

    1996-10-01

    Theoretical analyses have shown that rotations of a rigid body about the principal axis corresponding to the intermediate principal moment of inertia are unstable. This poses a potential problem for gymnasts who perform double somersaults without twist in a layout configuration. A computer simulation model is used to investigate configurational strategies for controlling such movements. It is shown that the build up of twist is not reduced by abduction of the arms but can be controlled by adopting a configuration with sufficient body flexion. For somersaults with a straight body, control in the form of asymmetrical arm abduction accelerations, based upon twist angular velocity and angular acceleration, is capable of preventing a build up of twist providing that the feedback time delay is less than a quarter somersault. PMID:8884479

  1. Supramolecular sensing: Enzyme activity with a twist

    NASA Astrophysics Data System (ADS)

    Amabilino, David B.

    2015-04-01

    A supramolecular polymer comprising stacked artificial chromophores to which zinc(II) complexes are appended is able to respond to enzymatic hydrolysis in aqueous solution. The assembly of molecules can twist reversibly and quickly in response to changes in the type of adenosine phosphate present.

  2. Projection Moire Interferometry for Rotorcraft Applications: Deformation Measurements of Active Twist Rotor Blades

    NASA Technical Reports Server (NTRS)

    Fleming, Gary A.; Soto, Hector L.; South, Bruce W.

    2002-01-01

    Projection Moire Interferometry (PMI) has been used during wind tunnel tests to obtain azimuthally dependent blade bending and twist measurements for a 4-bladed Active Twist Rotor (ATR) system in simulated forward flight. The ATR concept offers a means to reduce rotor vibratory loads and noise by using piezoelectric active fiber composite actuators embedded in the blade structure to twist each blade as they rotate throughout the rotor azimuth. The twist imparted on the blades for blade control causes significant changes in blade loading, resulting in complex blade deformation consisting of coupled bending and twist. Measurement of this blade deformation is critical in understanding the overall behavior of the ATR system and the physical mechanisms causing the reduction in rotor loads and noise. PMI is a non-contacting, video-based optical measurement technique capable of obtaining spatially continuous structural deformation measurements over the entire object surface within the PMI system field-of-view. When applied to rotorcraft testing, PMI can be used to measure the azimuth-dependent blade bending and twist along the full span of the rotor blade. This paper presents the PMI technique as applied to rotorcraft testing, and provides results obtained during the ATR tests demonstrating the PMI system performance. PMI measurements acquired at select blade actuation conditions generating minimum and maximum rotor loads are provided to explore the interrelationship between rotor loads, blade bending, and twist.

  3. Campylobacter jejuni adenosine triphosphate phosphoribosyltransferase is an active hexamer that is allosterically controlled by the twisting of a regulatory tail.

    PubMed

    Mittelstädt, Gerd; Moggré, Gert-Jan; Panjikar, Santosh; Nazmi, Ali Reza; Parker, Emily J

    2016-08-01

    Adenosine triphosphate phosphoribosyltransferase (ATP-PRT) catalyzes the first committed step of the histidine biosynthesis in plants and microorganisms. Here, we present the functional and structural characterization of the ATP-PRT from the pathogenic ε-proteobacteria Campylobacter jejuni (CjeATP-PRT). This enzyme is a member of the long form (HisGL ) ATP-PRT and is allosterically inhibited by histidine, which binds to a remote regulatory domain, and competitively inhibited by AMP. In the crystalline form, CjeATP-PRT was found to adopt two distinctly different hexameric conformations, with an open homohexameric structure observed in the presence of substrate ATP, and a more compact closed form present when inhibitor histidine is bound. CjeATP-PRT was observed to adopt only a hexameric quaternary structure in solution, contradicting previous hypotheses favoring an allosteric mechanism driven by an oligomer equilibrium. Instead, this study supports the conclusion that the ATP-PRT long form hexamer is the active species; the tightening of this structure in response to remote histidine binding results in an inhibited enzyme. PMID:27191057

  4. Hover Testing of the NASA/Army/MIT Active Twist Rotor Prototype Blade

    NASA Technical Reports Server (NTRS)

    Wilbur, Matthew L.; Yeager, William T., Jr.; Wilkie, W. Keats; Cesnik, Carlos E. S.; Shin, Sangloon

    2000-01-01

    Helicopter rotor individual blade control promises to provide a mechanism for increased rotor performance and reduced rotorcraft vibrations and noise. Active material methods, such as piezoelectrically actuated trailing-edge flaps and strain-induced rotor blade twisting, provide a means of accomplishing individual blade control without the need for hydraulic power in the rotating system. Recent studies have indicated that controlled strain induced blade twisting can be attained using piezoelectric active fiber composite technology. In order to validate these findings experimentally, a cooperative effort between NASA Langley Research Center, the Army Research Laboratory, and the MIT Active Materials and Structures Laboratory has been developed. As a result of this collaboration an aeroelastically-scaled active-twist model rotor blade has been designed and fabricated for testing in the heavy gas environment of the Langley Transonic Dynamics Tunnel (TDT). The results of hover tests of the active-twist prototype blade are presented in this paper. Comparisons with applicable analytical predictions of active-twist frequency response in hovering flight are also presented.

  5. Carbon Nanotube-Induced Pulmonary Granulomatous Disease: Twist1 and Alveolar Macrophage M1 Activation

    PubMed Central

    Barna, Barbara P.; Huizar, Isham; Malur, Anagha; McPeek, Matthew; Marshall, Irene; Jacob, Mark; Dobbs, Larry; Kavuru, Mani S.; Thomassen, Mary Jane

    2013-01-01

    Sarcoidosis, a chronic granulomatous disease of unknown cause, has been linked to several environmental risk factors, among which are some that may favor carbon nanotube formation. Using gene array data, we initially observed that bronchoalveolar lavage (BAL) cells from sarcoidosis patients displayed elevated mRNA of the transcription factor, Twist1, among many M1-associated genes compared to healthy controls. Based on this observation we hypothesized that Twist1 mRNA and protein expression might become elevated in alveolar macrophages from animals bearing granulomas induced by carbon nanotube instillation. To address this hypothesis, wild-type and macrophage-specific peroxisome proliferator-activated receptor gamma (PPARγ) knock out mice were given oropharyngeal instillation of multiwall carbon nanotubes (MWCNT). BAL cells obtained 60 days later exhibited significantly elevated Twist1 mRNA expression in granuloma-bearing wild-type or PPARγ knock out alveolar macrophages compared to sham controls. Overall, Twist1 expression levels in PPARγ knock out mice were higher than those of wild-type. Concurrently, BAL cells obtained from sarcoidosis patients and healthy controls validated gene array data: qPCR and protein analysis showed significantly elevated Twist1 in sarcoidosis compared to healthy controls. In vitro studies of alveolar macrophages from healthy controls indicated that Twist1 was inducible by classical (M1) macrophage activation stimuli (LPS, TNFα) but not by IL-4, an inducer of alternative (M2) macrophage activation. Findings suggest that Twist1 represents a PPARγ-sensitive alveolar macrophage M1 biomarker which is induced by inflammatory granulomatous disease in the MWCNT model and in human sarcoidosis. PMID:24322444

  6. Load Mitigation with Bending/Twist-coupled Blades on Rotors using Modern Control Strategies

    NASA Astrophysics Data System (ADS)

    Lobitz, Don W.; Veers, Paul S.

    2003-04-01

    The prospect of installing blades that twist as they bend and/or extend on horizontal axis wind turbines provides opportunities for enhanced energy capture and/or load mitigation. Although this coupling could be achieved in either an active or a passive manner, the passive approach is much more attractive owing to its simplicity and economy. As an example, a blade design might employ coupling between bending and twisting, so that as the blade bends owing to the action of the aerodynamic loads, it also twists, modifying the aerodynamic performance in some way. For reducing loads the blades are designed to twist towards feather as they bend. For variable-speed pitch-controlled rotors, dynamic computer simulations with turbulent inflow show that twist coupling substantially decreases fatigue damage over all wind speeds, without reducing average power. Maximum loads also decrease modestly. For constant-speed stall-controlled and variable-speed stall-controlled rotors, significant decreases in fatigue damage are observed at the lower wind speeds and smaller decreases at the higher wind speeds. Maximum loads also decrease slightly. As a general observation, whenever a rotor is operating in the linear aerodynamic range (lower wind speeds for stall control and all wind speeds for pitch control), substantial reductions in fatigue damage are realized.

  7. Development of an active twist rotor blade with distributed actuation and orthotropic material

    NASA Astrophysics Data System (ADS)

    Wierach, Peter; Riemenschneider, Johannes; Keye, Stefan

    2005-05-01

    Individual blade control (IBC) as well as higher harmonic control (HHC) for helicopter rotors promises to be a method to increase flight performance and to reduce vibration and noise. For those controls, an additional twist actuation of the rotor blade is needed. The developed concept comprises the implementation of distributed piezoelectric actuation into the rotor blade skin. In order to maximize the twist within given constraints, as torsional rigidity and given actuator design, the concept takes advantage of an orthotropic rotor blade skin. That way, a combination of shear actuation with orthotropic coupling generates more twist than each one of these effects alone. Previous approaches with distributed actuation used actuators operating in +/-45° direction with quasi-isotropic composites. A FE-Model of the blade was developed and validated using a simplified demonstrator. The objective of this study was to identify the effects of various geometric and material parameters to optimize the active twist performance of the blades. The whole development was embedded in an iterative process followed by an objective assessment. For this purpose a detailed structural model on the basis of the BO105 model rotor blade was developed, to predict the performance with respect to rotor dynamics, stability, aerodynamics and acoustics. Rotor dynamic simulations provided an initial overview of the active twist rotor performance. In comparison to the BO105 baseline rotor a noise reduction of 3 dB was predicted for an active twist of 0.8° at the blade tip. Additionally, a power reduction of 2.3% at 87m/s based on a 2.5 to BO105 was computed. A demonstrator blade with a rotor radius of 2m has been designed and manufactured. This blade will be tested to prove, that the calculated maximum twist can also be achieved under centrifugal loads.

  8. Multicyclic Controllable Twist Rotor Data Analysis

    NASA Technical Reports Server (NTRS)

    Wei, F. S.; Weisbrich, A. L.

    1979-01-01

    Rsults provide functional relationship between rotor performance, blade vibratory loads and dual control settings and indicate that multicyclic control produced significant reductions in blade flatwise bending moments and blade root actuator control loads. Higher harmonic terms of servo flap deflection were found to be most pronounced in flatwise bending moment, transmission vertical vibration and pitch link vibratory load equations. The existing test hardware represents a satisfactory configuration for demonstrating MCTR technology and defining a data base for additional wind tunnel testing.

  9. Unwinding motion of a twisted active region filament

    SciTech Connect

    Yan, X. L.; Xue, Z. K.; Kong, D. F.; Liu, J. H.; Xu, C. L.

    2014-12-10

    To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5π obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.

  10. The Effect of Tip Geometry on Active-Twist Rotor Response

    NASA Technical Reports Server (NTRS)

    Wilbur, Matthew L.; Sekula, Martin K.

    2005-01-01

    A parametric examination of the effect of tip geometry on active-twist rotor system response is conducted. Tip geometry parameters considered include sweep, taper, anhedral, nonlinear twist, and the associated radial initiation location for each of these variables. A detailed study of the individual effect of each parameter on active-twist response is presented, and an assessment offered of the effect of combining multiple tip shape parameters. Tip sweep is shown to have the greatest affect on active-twist response, significantly decreasing the response available. Tip taper and anhedral are shown to increase moderately the active-twist response, while nonlinear twist is shown to have a minimal effect. A candidate tip shape that provides active-twist response equivalent to or greater than a rectangular planform blade is presented.

  11. Twist1 Controls a Cell-Specification Switch Governing Cell Fate Decisions within the Cardiac Neural Crest

    PubMed Central

    Vincentz, Joshua W.; Firulli, Beth A.; Lin, Andrea; Spicer, Douglas B.; Howard, Marthe J.; Firulli, Anthony B.

    2013-01-01

    Neural crest cells are multipotent progenitor cells that can generate both ectodermal cell types, such as neurons, and mesodermal cell types, such as smooth muscle. The mechanisms controlling this cell fate choice are not known. The basic Helix-loop-Helix (bHLH) transcription factor Twist1 is expressed throughout the migratory and post-migratory cardiac neural crest. Twist1 ablation or mutation of the Twist-box causes differentiation of ectopic neuronal cells, which molecularly resemble sympathetic ganglia, in the cardiac outflow tract. Twist1 interacts with the pro-neural factor Sox10 via its Twist-box domain and binds to the Phox2b promoter to repress transcriptional activity. Mesodermal cardiac neural crest trans-differentiation into ectodermal sympathetic ganglia-like neurons is dependent upon Phox2b function. Ectopic Twist1 expression in neural crest precursors disrupts sympathetic neurogenesis. These data demonstrate that Twist1 functions in post-migratory neural crest cells to repress pro-neural factors and thereby regulate cell fate determination between ectodermal and mesodermal lineages. PMID:23555309

  12. Proximal Blade Twist Feedback Control for Heliogyro Solar Sails

    NASA Astrophysics Data System (ADS)

    Smith, Sarah Mitchell

    A heliogyro spacecraft is a specific type of solar sail that generates thrust from the reflection of solar photons. It consists of multiple long (200 to 600 meters), thin blades, similar to a helicopter. The heliogyro's blades remain in tension by spinning around the central hub of the spacecraft. The individual blades are pitched collectively or cyclically to produce the desired maneuver profile. The propellant-free heliogyro is a long-duration sustainable spacecraft whose maneuverability allows it to attain previously inaccessible orbits for traditional spacecraft. The blades are constructed from thin Mylar sheets, approximately 2.5 ?m thick, which have very little inherent damping making it necessary to include some other way of attenuating blade vibration caused by maneuvering. The most common approach is to incorporate damping through the root pitch actuator. However, due to the small root pitch control torques required, on the order of 2 ?Nm, compared to the large friction torques associated with a root pitch actuator, it is challenging to design a root control system that takes friction into account and can still add damping to the blade. The purpose of this research is to address the limitations of current control designs for a heliogyro spacecraft and to develop a physically realizable root pitch controller that effectively damps the torsional structural modes of a single heliogyro blade. Classical control theory in conjunction with impedance control techniques are used to design a position-source root pitch controller to dominate friction with high gains, wrapped with an outer loop that adds damping to the blade by sensing differential twist outboard of the blade root. First, modal parameter characterization experiments were performed on a small-scale heliogyro blade in a high vacuum chamber to determine a damping constant to be used in the membrane ladder finite element model of the blade. The experimental damping ratio of the lowest frequency torsional

  13. Strong optical activity from twisted-cross photonic metamaterials.

    PubMed

    Decker, M; Ruther, M; Kriegler, C E; Zhou, J; Soukoulis, C M; Linden, S; Wegener, M

    2009-08-15

    Following a recent theoretical suggestion and microwave experiments, we fabricate photonic metamaterials composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric. The resulting two effective resonances of the coupled system lie in the 1-2 microm wavelength regime and exhibit pronounced circular dichroism, while the circular polarization conversion is very small. In between the two resonances, we find a fairly broad spectral regime with strong optical activity, i.e., with a pure rotation of incident linear polarization. The measured optical transmittance spectra agree well with theory. PMID:19684829

  14. Further Examination of the Vibratory Loads Reduction Results from the NASA/ARMY/MIT Active Twist Rotor Test

    NASA Technical Reports Server (NTRS)

    Wilbur, Matthew L.; Yeager, William T., Jr.; Sekula, Martin K.

    2002-01-01

    The vibration reduction capabilities of a model rotor system utilizing controlled, strain-induced blade twisting are examined. The model rotor blades, which utilize piezoelectric active fiber composite actuators, were tested in the NASA Langley Transonic Dynamics Tunnel using open-loop control to determine the effect of active-twist on rotor vibratory loads. The results of this testing have been encouraging, and have demonstrated that active-twist rotor designs offer the potential for significant load reductions in future helicopter rotor systems. Active twist control was found to use less than 1% of the power necessary to operate the rotor system and had a pronounced effect on both rotating- and fixed-system loads, offering reductions in individual harmonic loads of up to 100%. A review of the vibration reduction results obtained is presented, which includes a limited set of comparisons with results generated using the second-generation version of the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II) rotorcraft comprehensive analysis.

  15. Demonstration of an elastically coupled twist control concept for tilt rotor blade application

    NASA Technical Reports Server (NTRS)

    Lake, R. C.; Nixon, M. W.; Wilbur, M. L.; Singleton, J. D.; Mirick, P. H.

    1994-01-01

    This study demonstrated the feasibility of passive blade twist control for composite rotor blades. Hover testing of the set of blades produced maximum twist changes of 2.54 degrees for the unballasted blade configuration and 5.24 degrees for the ballasted blade configuration. These results compared well with those obtained from a detailed finite element analysis model of the rotor blade, which yielded maximum twists of 3.02 and 5.61 degrees for the unballasted and ballasted blade configurations, respectively.

  16. Electrically controllable Fresnel lens in 90° twisted nematic liquid crystals.

    PubMed

    Kuo, Chie-Tong; Li, Chien-Yu; Lin, Shih-Hung; Yeh, Hui-Chen

    2015-10-01

    This study presents a theoretical analysis and experimental demonstration of an electrically controllable Fresnel lens in a 90° twisted nematic liquid crystal cell. The cell gap was chosen to satisfy the Gooch-Tarry conditions, and therefore, the polarization rotation effect was valid regardless of the incident polarization direction. The polarization sensitivity of the diffraction efficiency of the 90° twisted nematic Fresnel lens was dependent on the applied voltage regime. Theoretical calculations effectively explain the experimental results. PMID:26480119

  17. Coupled CFD/CSD Computation of Airloads of an Active-Twist Rotor

    NASA Technical Reports Server (NTRS)

    Massey, Steven J.; Kreshock, Andrew R.; Sekula, Martin K

    2013-01-01

    An unsteady Reynolds averaged Navier-Stokes analysis loosely coupled with a comprehensive rotorcraft code for blade trim and aeroelastic effects is presented for a second-generation Active-Twist Rotor. Mesh and temporal sensitives of computed airloads are evaluated. In the final paper, computed airloads will be compared with wind tunnel data for the Active-Twist Rotor test that is currently underway.

  18. Twist Model Development and Results From the Active Aeroelastic Wing F/A-18 Aircraft

    NASA Technical Reports Server (NTRS)

    Lizotte, Andrew; Allen, Michael J.

    2005-01-01

    Understanding the wing twist of the active aeroelastic wing F/A-18 aircraft is a fundamental research objective for the program and offers numerous benefits. In order to clearly understand the wing flexibility characteristics, a model was created to predict real-time wing twist. A reliable twist model allows the prediction of twist for flight simulation, provides insight into aircraft performance uncertainties, and assists with computational fluid dynamic and aeroelastic issues. The left wing of the aircraft was heavily instrumented during the first phase of the active aeroelastic wing program allowing deflection data collection. Traditional data processing steps were taken to reduce flight data, and twist predictions were made using linear regression techniques. The model predictions determined a consistent linear relationship between the measured twist and aircraft parameters, such as surface positions and aircraft state variables. Error in the original model was reduced in some cases by using a dynamic pressure-based assumption and by using neural networks. These techniques produced excellent predictions for flight between the standard test points and accounted for nonlinearities in the data. This report discusses data processing techniques and twist prediction validation, and provides illustrative and quantitative results.

  19. Twist Model Development and Results from the Active Aeroelastic Wing F/A-18 Aircraft

    NASA Technical Reports Server (NTRS)

    Lizotte, Andrew M.; Allen, Michael J.

    2007-01-01

    Understanding the wing twist of the active aeroelastic wing (AAW) F/A-18 aircraft is a fundamental research objective for the program and offers numerous benefits. In order to clearly understand the wing flexibility characteristics, a model was created to predict real-time wing twist. A reliable twist model allows the prediction of twist for flight simulation, provides insight into aircraft performance uncertainties, and assists with computational fluid dynamic and aeroelastic issues. The left wing of the aircraft was heavily instrumented during the first phase of the active aeroelastic wing program allowing deflection data collection. Traditional data processing steps were taken to reduce flight data, and twist predictions were made using linear regression techniques. The model predictions determined a consistent linear relationship between the measured twist and aircraft parameters, such as surface positions and aircraft state variables. Error in the original model was reduced in some cases by using a dynamic pressure-based assumption. This technique produced excellent predictions for flight between the standard test points and accounted for nonlinearities in the data. This report discusses data processing techniques and twist prediction validation, and provides illustrative and quantitative results.

  20. Active-Region Twist Derived from Magnetic Tongues and Linear Force-Free Extrapolations

    NASA Astrophysics Data System (ADS)

    Poisson, Mariano; López Fuentes, Marcelo; Mandrini, Cristina H.; Démoulin, Pascal

    2015-11-01

    The main aim of this study is to compare the amount of twist present in emerging active regions (ARs) from photospheric and coronal data. We use linear force-free field models of the observed coronal structure of ARs to determine the global twist. The coronal twist is derived, on one hand, from the force-free parameter [α] of the model and, on the other, from the computed coronal magnetic helicity normalized by the magnetic flux squared. We compare our results, for the same set of ARs, with those of Poisson et al. ( Solar Phys. 290, 727, 2015), in which the twist was estimated using the so-called magnetic tongues observed in line-of-sight magnetograms during AR emergence. We corroborate the agreement between the photospheric and coronal twist-sign and the presence of magnetic tongues as an early proxy of the AR non-potentiality. We find a globally linear relationship between the coronal twist and the one previously deduced for the emerging AR flux rope at the photospheric level. The coronal-twist value is typically lower by a factor of six than the one deduced for the emerging flux rope. We interpret this result as due to the partial emergence of the flux rope that forms the region.

  1. Initial Aerodynamic and Acoustic Study of an Active Twist Rotor Using a Loosely Coupled CFD/CSD Method

    NASA Technical Reports Server (NTRS)

    Boyd, David D. Jr.

    2009-01-01

    Preliminary aerodynamic and performance predictions for an active twist rotor for a HART-II type of configuration are performed using a computational fluid dynamics (CFD) code, OVERFLOW2, and a computational structural dynamics (CSD) code, CAMRAD -II. These codes are loosely coupled to compute a consistent set of aerodynamics and elastic blade motions. Resultant aerodynamic and blade motion data are then used in the Ffowcs-Williams Hawkins solver, PSU-WOPWOP, to compute noise on an observer plane under the rotor. Active twist of the rotor blade is achieved in CAMRAD-II by application of a periodic torsional moment couple (of equal and opposite sign) at the blade root and tip at a specified frequency and amplitude. To provide confidence in these particular active twist predictions for which no measured data is available, the rotor system geometry and computational set up examined here are identical to that used in a previous successful Higher Harmonic Control (HHC) computational study. For a single frequency equal to three times the blade passage frequency (3P), active twist is applied across a range of control phase angles at two different amplitudes. Predicted results indicate that there are control phase angles where the maximum mid-frequency noise level and the 4P non -rotating hub vibrations can be reduced, potentially, both at the same time. However, these calculated reductions are predicted to come with a performance penalty in the form of a reduction in rotor lift-to-drag ratio due to an increase in rotor profile power.

  2. Development of an Active Twist Rotor for Wind: Tunnel Testing (NLPN97-310

    NASA Technical Reports Server (NTRS)

    Cesnik, Carlos E. S.; Shin, SangJoon; Hagood, Nesbitt W., IV

    1998-01-01

    The development of the Active Twist Rotor prototype blade for hub vibration and noise reduction studies is presented in this report. Details of the modeling, design, and manufacturing are explored. The rotor blade is integrally twisted by direct strain actuation. This is accomplished by distributing embedded piezoelectric fiber composites along the span of the blade. The development of the analysis framework for this type of active blade is presented. The requirements for the prototype blade, along with the final design results are also presented. A detail discussion on the manufacturing aspects of the prototype blade is described. Experimental structural characteristics of the prototype blade compare well with design goals, and preliminary bench actuation tests show lower performance than originally predicted. Electrical difficulties with the actuators are also discussed. The presented prototype blade is leading to a complete fully articulated four-blade active twist rotor system for future wind tunnel tests.

  3. Deep Tunnel's twists and turns -- CSO control in metro Chicago

    SciTech Connect

    Farnan, J.C.; Lue-Hing, C.; O'Connor, T.K.; Rakoczy, J.R.

    1998-07-01

    Metro-Chicago began its search for a comprehensive solution to its severe and then-worsening combined sewer overflow (CSO) pollution and flooding problems even before enactment of the 1972 Federal Clean Water Act. Many studies and extensive interagency cooperation singled out the Tunnel and Reservoir Plan (TARP) as the best means of cost-effectively achieving three anti-pollution and anti-flooding objectives: protect Chicagoland's main drinking water supply--Lake Michigan--from raw sewage backflows; clean up polluted streams; and alleviated basement sewage backups. Owing to TARP's uniqueness, initially there was little or no design, construction or operations experience to draw upon to help implement the project. But since TARP's four systems operate independently, and new tunnel segments are placed into operation as soon as completed, the District has been able to continuously monitor performance and obtain operations feedback. This has enabled ongoing refinement of design, construction, and operational strategy on successive TARP tunnel contracts. Herein is a brief discussion of TARP's development--an evolutionary process with many twists and turns--and of problems and opportunities encountered which resulted in design or operations changes.

  4. Aggregation-Induced-Emission-Active Macrocycle Exhibiting Analogous Triply and Singly Twisted Möbius Topologies.

    PubMed

    Wang, Erjing; He, Zikai; Zhao, Engui; Meng, Luming; Schütt, Christian; Lam, Jacky W Y; Sung, Herman H Y; Williams, Ian D; Huang, Xuhui; Herges, Rainer; Tang, Ben Zhong

    2015-08-10

    Molecules with Möbius topology have drawn increasing attention from scientists in a variety of fields, such as organic chemistry, inorganic chemistry, and material science. However, synthetic difficulties and the lack of functionality impede their fundamental understanding and practical applications. Here, we report the facile synthesis of an aggregation-induced-emission (AIE)-active macrocycle (TPE-ET) and investigate its analogous triply and singly twisted Möbius topologies. Because of the twisted and flexible nature of the tetraphenylethene units, the macrocycle adjusts its conformations so as to accommodate different guest molecules in its crystals. Moreover, theoretical studies including topological and electronic calculations reveal the energetically favorable interconversion process between triply and singly twisted topologies. PMID:26177730

  5. Material characterization of active fiber composites for integral twist-actuated rotor blade application

    NASA Astrophysics Data System (ADS)

    Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

    2004-10-01

    The primary objective of this work was to perform material characterization of the active fiber composite (AFC) actuator system for the Boeing active material rotor (AMR) blade application. The purpose of the AMR was to demonstrate active vibration control in helicopters through integral twist-actuation of the blade. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to enhance actuation performance. These conformable actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural control. Therefore, extensive electromechanical material characterization was required to evaluate AFCs both as actuators and as structural components of the blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included nominal actuation tests, stress-strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing procedure developed to evaluate the relevant properties of the AFCs for structural application. The material characterization tests provided an invaluable insight into the behavior of the AFCs under various electromechanical conditions. The results from this comprehensive material characterization of the AFC actuator system supported the design and operation of the AMR blades scheduled for wind tunnel tests.

  6. Application of Out-of-Plane Warping to Control Rotor Blade Twist

    NASA Technical Reports Server (NTRS)

    VanWeddingen, Yannick; Bauchau, Olivier; Kottapalli, Sesi; Ozbay, Serkan; Mehrotra, Yogesh

    2012-01-01

    The goal of this ongoing study is to develop and demonstrate the feasibility of a blade actuation system to dynamically change the twist, and/or the camber, of an airfoil section and, consequently, alter the in-flight aerodynamic loading on the blade for efficient flight control. The required analytical and finite element tools are under development to enable an accurate and comprehensive aeroelastic assessment of the current Full-Blade Warping and 3D Warping Actuated Trailing Edge Flap concepts. The feasibility of the current concepts for swashplateless rotors and higher harmonic blade control is also being investigated. In particular, the aim is to complete the following objectives, some of which have been completed (as noted below) and others that are currently ongoing: i) Develop a Vlasov finite element model and validate against the ABAQUS shell models (completed). ii) Implement the 3D warping actuation concept within the comprehensive analysis code DYMORE. iii) Perform preliminary aeroelastic simulations of blades using DYMORE with 3D warping actuation: a) Investigate the blade behavior under 1 per/rev actuation. Determine whether sufficient twist can be generated and sustained to achieve primary blade control. b) Investigate the behavior of a trailing edge flap configuration under higher harmonic excitations. Determine how much twist can be obtained at the harmonics 2-5 per/rev. iv) Determine actuator specifications such as the power required, load and displacements, and identify the stress and strain distributions in the actuated blades. In general, the completion of Item ii) above will give an additional research capability in rotorcraft dynamics analyses, i.e., the capability to calculate the rotor blade twist due to warping, something that is not currently available in any of the existing comprehensive rotorcraft analyses.

  7. Drag-based composite super-twisting sliding mode control law design for Mars entry guidance

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenhua; Yang, Jun; Li, Shihua; Guo, Lei

    2016-06-01

    In this paper, the drag-based trajectory tracking guidance problem is investigated for Mars entry vehicle subject to uncertainties. A composite super twisting sliding mode control method based on finite-time disturbance observer is proposed for guidance law design. The proposed controller not only eliminates the effects of matched and mismatched disturbances due to uncertainties of atmospheric models and vehicle aerodynamics but also guarantees the continuity of control action. Numerical simulations are carried out on the basis of Mars Science Laboratory mission, where the results show that the proposed methods can improve the Mars entry guidance precision as compared with some existing guidance methods including PID and ADRC.

  8. Active twist rotor blade modelling using particle-wake aerodynamics and geometrically exact beam structural dynamics

    NASA Astrophysics Data System (ADS)

    Cesnik, C. E. S.; Opoku, D. G.; Nitzsche, F.; Cheng, T.

    2004-06-01

    An active aeroelastic and aeroacoustic analysis of helicopter rotor systems is presented in this paper. It is a tightly coupled computational aeroelastic code that interfaces a particle-wake panel method code with an active nonlinear mixed variational intrinsic beam element code. In addition, a Ffowcs-Williams-Hawkings equation-based acoustic component is incorporated to complete the numerical implementation. The theory behind each component is summarized here as well as the method for coupling the aerodynamic and structural components. Sample acoustic and aeroelastic results are given for different model-scale rotors. Comparisons with available (passive) results show very good agreement. Preliminary study with an active twist rotor is also shown.

  9. Evaluations of bit sleeve and twisted-body bit designs for controlling roof bolter dust

    PubMed Central

    Beck, T.W.

    2015-01-01

    Drilling into coal mine roof strata to install roof bolts has the potential to release substantial quantities of respirable dust. Due to the proximity of drill holes to the breathing zone of roof bolting personnel, dust escaping the holes and avoiding capture by the dust collection system pose a potential respiratory health risk. Controls are available to complement the typical dry vacuum collection system and minimize harmful exposures during the initial phase of drilling. This paper examines the use of a bit sleeve in combination with a dust-hog-type bit to improve dust extraction during the critical initial phase of drilling. A twisted-body drill bit is also evaluated to determine the quantity of dust liberated in comparison with the dust-hog-type bit. Based on the results of our laboratory tests, the bit sleeve may reduce dust emissions by one-half during the initial phase of drilling before the drill bit is fully enclosed by the drill hole. Because collaring is responsible for the largest dust liberations, overall dust emission can also be substantially reduced. The use of a twisted-body bit has minimal improvement on dust capture compared with the commonly used dust-hog-type bit. PMID:26257435

  10. Prediction of BVI Noise for an Active Twist Rotor Using a Loosely Coupled CFD/CSD Method and Comparison to Experimental Data

    NASA Technical Reports Server (NTRS)

    Fogarty, David E.; Wilbur, Matthew L.; Sekula, Martin K.; Boyd, David Douglas, Jr.

    2012-01-01

    Numerical predictions of the acoustic characteristics of an Active Twist Rotor (ATR), using two methods to compute the rotor blade aerodynamics and elastic blade motion are compared to experimental data from a wind tunnel test in the NASA Langley Transonic Dynamics Tunnel (TDT) in 2000. The first method, a loosely coupled iterative method, utilizes the Computational Fluid Dynamics (CFD) code OVERFLOW 2 and the Computational Structural Dynamics (CSD) code CAMRAD II. The second method utilizes the CAMRAD II free-wake model only. The harmonic active-twist control to the main rotor blade system is identified with three parameters - harmonic actuation frequency, actuation amplitude, and control phase angle. The resulting aerodynamics and blade motion data from the two methods are then used in the acoustics code PSU-WOPWOP to predict acoustic pressure on a spherical array of equally spaced observers surrounding the rotor. This spherical distribution of pressure is used to compute the sound power level representing baseline and actuated conditions. Sound power levels for three categories of noise are defined as - blade-vortex interaction sound power level (BVIPWL), low frequency sound power level (LFPWL), and overall sound power level, OAPWL. Comparisons with measured data indicate the CFD/CSD analysis successfully captures the trends in sound power levels and the effects of active-twist control at advance ratios of 0.14 and 0.17. The free-wake model predictions show inconsistent sound power levels relative to the trends in the experimental and CFD data. This paper presents the first ever comparison between CFD/CSD acoustic predictions for an active-twist rotor and experimental measurements.

  11. EGF Receptor Promotes Prostate Cancer Bone Metastasis by Downregulating miR-1 and Activating TWIST1

    PubMed Central

    Chang, Yung-Sheng; Chen, Wei-Yu; Yin, Juan Juan; Sheppard-Tillman, Heather; Huang, Jiaoti; Liu, Yen-Nien

    2016-01-01

    Dysregulation of the EGFR signaling axis enhances bone metastases in many solid cancers. However, the relevant downstream effector signals in this axis are unclear. miR-1 was recently shown to function as a tumor suppressor in prostate cancer cells, where its expression correlated with reduced metastatic potential. In this study, we demonstrated a role for EGFR translocation in regulating transcription of miR-1-1, which directly targets expression of TWIST1. Consistent with these findings, we observed decreased miR-1 levels that correlated with enhanced expression of activated EGFR and TWIST1 in a cohort of human prostate cancer specimens and additional datasets. Our findings support a model in which nuclear EGFR acts as a transcriptional repressor to constrain the tumor-suppressive role of miR-1 and sustain oncogenic activation of TWIST1, thereby leading to accelerated bone metastasis. PMID:26071255

  12. Demonstration of an elastically coupled twist control concept for tilt rotor blade application

    NASA Technical Reports Server (NTRS)

    Lake, R. C.; Nixon, M. W.; Wilbur, M. L.; Singleton, J. D.; Mirick, P. H.

    1994-01-01

    The purpose of this Note is to present results from an analytic/experimental study that investigated the potential for passively changing blade twist through the use of extension-twist coupling. A set of composite model rotor blades was manufactured from existing blade molds for a low-twist metal helicopter rotor blade, with a view toward establishing a preliminary proof concept for extension-twist-coupled rotor blades. Data were obtained in hover for both a ballasted and unballasted blade configuration in sea-level atmospheric conditions. Test data were compared with results obtained from a geometrically nonlinear analysis of a detailed finite element model of the rotor blade developed in MSC/NASTRAN.

  13. Nitrogen-Doped Graphene and Twisted Bilayer Graphene via Hyperthermal Ion Implantation with Depth Control.

    PubMed

    Cress, Cory D; Schmucker, Scott W; Friedman, Adam L; Dev, Pratibha; Culbertson, James C; Lyding, Joseph W; Robinson, Jeremy T

    2016-03-22

    We investigate hyperthermal ion implantation (HyTII) as a means for substitutionally doping layered materials such as graphene. In particular, this systematic study characterizes the efficacy of substitutional N-doping of graphene using HyTII over an N(+) energy range of 25-100 eV. Scanning tunneling microscopy results establish the incorporation of N substituents into the graphene lattice during HyTII processing. We illustrate the differences in evolution of the characteristic Raman peaks following incremental doses of N(+). We use the ratios of the integrated D and D' peaks, I(D)/I(D') to assess the N(+) energy-dependent doping efficacy, which shows a strong correlation with previously reported molecular dynamics (MD) simulation results and a peak doping efficiency regime ranging between approximately 30 and 50 eV. We also demonstrate the inherent monolayer depth control of the HyTII process, thereby establishing a unique advantage over other less-specific methods for doping. We achieve this by implementing twisted bilayer graphene (TBG), with one layer of isotopically enriched (13)C and one layer of natural (12)C graphene, and modify only the top layer of the TBG sample. By assessing the effects of N-HyTII processing, we uncover dose-dependent shifts in the transfer characteristics consistent with electron doping and we find dose-dependent electronic localization that manifests in low-temperature magnetotransport measurements. PMID:26910346

  14. Twisting solar coronal jet launched at the boundary of an active region

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Guo, Y.; Moreno-Insertis, F.; Aulanier, G.; Yelles Chaouche, L.; Nishizuka, N.; Harra, L. K.; Thalmann, J. K.; Vargas Dominguez, S.; Liu, Y.

    2013-11-01

    Aims: A broad jet was observed in a weak magnetic field area at the edge of active region NOAA 11106 that also produced other nearby recurring and narrow jets. The peculiar shape and magnetic environment of the broad jet raised the question of whether it was created by the same physical processes of previously studied jets with reconnection occurring high in the corona. Methods: We carried out a multi-wavelength analysis using the EUV images from the Atmospheric Imaging Assembly (AIA) and magnetic fields from the Helioseismic and Magnetic Imager (HMI) both on-board the Solar Dynamics Observatory, which we coupled to a high-resolution, nonlinear force-free field extrapolation. Local correlation tracking was used to identify the photospheric motions that triggered the jet, and time-slices were extracted along and across the jet to unveil its complex nature. A topological analysis of the extrapolated field was performed and was related to the observed features. Results: The jet consisted of many different threads that expanded in around 10 minutes to about 100 Mm in length, with the bright features in later threads moving faster than in the early ones, reaching a maximum speed of about 200 km s-1. Time-slice analysis revealed a striped pattern of dark and bright strands propagating along the jet, along with apparent damped oscillations across the jet. This is suggestive of a (un)twisting motion in the jet, possibly an Alfvén wave. Bald patches in field lines, low-altitude flux ropes, diverging flow patterns, and a null point were identified at the basis of the jet. Conclusions: Unlike classical λ or Eiffel-tower-shaped jets that appear to be caused by reconnection in current sheets containing null points, reconnection in regions containing bald patches seems to be crucial in triggering the present jet. There is no observational evidence that the flux ropes detected in the topological analysis were actually being ejected themselves, as occurs in the violent phase of

  15. Analytical development of single crystal Macro Fiber Composite actuators for active twist rotor blades

    NASA Astrophysics Data System (ADS)

    Park, Jae-Sang; Kim, Ji-Hwan

    2005-08-01

    A Macro Fiber Composite (MFC) is a piezoelectric fiber composite which has an interdigitated electrode, rectangular cross-section and unidirectional polycrystalline piezoceramic (PZT) fibers embedded in the polymer matrix. A MFC actuator has much higher actuation performance and flexibility than a monolithic piezoceramic actuator. Moreover, the single crystal piezoelectric material exhibits much higher induced strain levels, energy density and coupling than those of polycrystalline piezoceramic materials. Thus, the performance of an MFC can be improved by using single crystal piezoelectric fiber instead of polycrystalline piezoceramic fiber. This study investigates the analytical modeling, material properties and actuation performance of an MFC using single crystal piezoelectric material (single crystal MFC). For single crystal MFC, the mechanical properties are calculated by the classical lamination theory, and the uniform fields model (UFM) is adopted to predict piezoelectric strain constants. In addition, the actuation performance of the single crystal MFC with the active twist rotor blade is studied. The material properties and actuation performance of single crystal MFC are compared with those of standard MFC.

  16. Light's twist

    PubMed Central

    Padgett, Miles

    2014-01-01

    That light travels in straight lines is a statement of the obvious. However, the energy and momentum flow within light beams can twist to form vortices such as eddies in a stream. These twists carry angular momentum, which can make microscopic objects spin, be used to encode extra information in communication systems, enable the design of novel imaging systems and allow new tests of quantum mechanics. PMID:25484612

  17. Prp19 facilitates invasion of hepatocellular carcinoma via p38 mitogen-activated protein kinase/Twist1 pathway

    PubMed Central

    Zhu, Ji-Min; Yu, Qian; Xue, Ru-Yi; Fang, Ying; Zhang, Yi-An; Chen, Yan-Jie; Liu, Tao-Tao; Dong, Ling; Shen, Xi-Zhong

    2016-01-01

    Pre-mRNA processing factor 19 (Prp19) is involved in many cellular events including pre-mRNA processing and DNA damage response. However, the pathological role of Prp19 in hepatocellular carcinoma (HCC) is still elusive. Here, we reported that Prp19 was increased in most HCC tissues and HCC cell lines, and its overexpression in HCC tissues was positively correlated with vascular invasion, tumor capsule breakthrough and poor prognosis. Prp19 potentiated migratory and invasive abilities of HCC cells in vitro and in vivo. Furthermore Prp19 facilitated Twist1-induced epithelial-mesenchymal transition. Mechanistic insights revealed that Prp19 directly binded with TGF-β-activated kinase1 (TAK1) and promoted the activation of p38 mitogen-activated protein kinase (MAPK), preventing Twist1 from degradation. Finally Prp19/p38 MAPK/Twist1 axis was attested in nude mice xenografts and HCC patient specimens. This work implies that the gain of Prp19 is a critical event during the progression of HCC, making it a promising target for malignancies with aberrant Prp19 expression. PMID:26959880

  18. Discrete Levels of Twist Activity Are Required to Direct Distinct Cell Functions during Gastrulation and Somatic Myogenesis

    PubMed Central

    Wong, Ming-Ching; Dobi, Krista C.; Baylies, Mary K.

    2014-01-01

    Twist (Twi), a conserved basic helix-loop-helix transcriptional regulator, directs the epithelial-to-mesenchymal transition (EMT), and regulates changes in cell fate, cell polarity, cell division and cell migration in organisms from flies to humans. Analogous to its role in EMT, Twist has been implicated in metastasis in numerous cancer types, including breast, pancreatic and prostate. In the Drosophila embryo, Twist is essential for discrete events in gastrulation and mesodermal patterning. In this study, we derive a twi allelic series by examining the various cellular events required for gastrulation in Drosophila. By genetically manipulating the levels of Twi activity during gastrulation, we find that coordination of cell division is the most sensitive cellular event, whereas changes in cell shape are the least sensitive. Strikingly, we show that by increasing levels of Snail expression in a severe twi hypomorphic allelic background, but not a twi null background, we can reconstitute gastrulation and produce viable adult flies. Our results demonstrate that the level of Twi activity determines whether the cellular events of ventral furrow formation, EMT, cell division and mesodermal migration occur. PMID:24915423

  19. Correction of contrast in projection systems by means of phase-controlled prism coatings and band-shifted twist compensators

    NASA Astrophysics Data System (ADS)

    Rosenbluth, Alan E.; Lu, Minhua; Yang, Kei H.; Ho, Kenneth; Singh, Rama N.; Nakasogi, Teruhiro

    2000-04-01

    Projectors that use LCOS lightvalves face special contrast requirements. Most configurations for reflective light valves employ tilted beam-dividing coatings that see both bright and dark polarization states. The optics must then be designed to eliminate polarization mixing at these coatings, which ordinarily arises when the S and P planes for different rays are non-parallel. We show how phase- controlled coatings can exploit the double-pass symmetry of the Plumbicon tri-prism geometry to correct this effect, reducing cross-polarized reflectivity to approximately 1E-3 when the light valve is mirror-like in black-state. Though contrast in different rays varies as a function of both ray skew component and coating angle of incidence, we show that for NA control in the optics. Scatter depolarization at the edges of pixel electrodes is enhanced in these light valves, because the inherent twist causes the backplane polarization to be rotated out of alignment with pixel edges. We show that all of these contrast degradation mechanisms can be addressed by incorporating into the light valve a compensating layer having opposite birefringence to the black-state TN active layer. Moreover, when the compensating layer and driven layer are blue-shifted to a shorter LC thickness than would ordinarily be appropriate for the wavelength band of interest, a highly achromatic response is obtained at all gray levels.

  20. Passive approach of controlling twist in composite tilt-rotor blades

    NASA Astrophysics Data System (ADS)

    Kosmatka, John B.; Lake, Renee C.

    1996-05-01

    This paper examines the static and dynamic behavior of initially twisted composite spars for tilt-rotor applications, as well as documenting the fabrication of five pairs of initially twisted advanced composite single-cell spars. Spars having five different material stacking sequences were fabricated for a given geometric and pretwist definition so as to determine the maximum and minimum spar untwist for a given unit load (stiffness approach) and a given maximum load (strength approach). Analytical static stiffness and strength results are presented using a detailed shell-type finite element model, along with a two-dimensional elasticity approach to show how the maximum elastic beam untwist varies as a function of the composite spar geometric parameters and material ply orientation. Experimentally measured free-free and cantilevered natural frequencies and damping levels of the spars are presented along with a correlation to a highly refined shell-type finite element model. These vibration results reveal that both ply angle orientation and initial twist significantly alter the spar natural frequencies, where the effects are largest in the higher bending and torsion modes. Damping level changes were clearly observed with ply orientation changes (i.e. increases in extension-torsion coupling produced bending mode damping increases and torsion mode damping decreases).

  1. PAQR3 enhances Twist1 degradation to suppress epithelial-mesenchymal transition and metastasis of gastric cancer cells.

    PubMed

    Guo, Weiwei; You, Xue; Xu, Daqian; Zhang, Yuxue; Wang, Zheng; Man, Kaiyang; Wang, Zhenzhen; Chen, Yan

    2016-04-01

    Twist1 is an essential transcription factor required to initiate epithelial-mesenchymal transition (EMT) and promote tumor metastasis. PAQR3 is a newly found tumor suppressor that is frequently downregulated in many types of human cancers. Downregulation of PAQR3 is associated with accelerated metastasis and poor prognosis of the patients with gastric cancers. In this study, we demonstrate that PAQR3 is actively involved in the degradation of Twist1 and whereby regulates EMT and metastasis of gastric cancer cells. PAQR3 overexpression reduces the protein level but not the mRNA level of Twist1. The protein stability and polyubiquitination of Twist1 are altered by PAQR3. PAQR3 forms a complex with Twist1 and BTRC, an E3 ubiquitin ligase. PAQR3 enhances the interaction between Twist1 and BTRC. Twist1 is mobilized from the nucleus to a proteasome-containing structure in the cytoplasm upon overexpression of PAQR3 and BTRC, which is required for PAQR3-induced degradation of Twist1. The Twist1 box domain of the Twist1 protein is required for the interaction of Twist1 with both PAQR3 and BTRC, indispensable for PAQR3-mediated degradation of Twist1. Both BTRC and Twist1 are required for the inhibitory effects of PAQR3 on migration and EMT phenotype of gastric cancers cells. Importantly, Twist1 is indispensable for the inhibitory effect of PAQR3 on metastasis of gastric cancer cellsin vivo Collectively, these findings not only pinpoint that Twist1 mediates the modulatory function of PAQR3 on EMT and metastasis but also suggest that targeting Twist1 is a promising strategy to control metastasis of tumors with downregulation of PAQR3. PMID:26905590

  2. An unexpected twist to the activation of IKKβ: TAK1 primes IKKβ for activation by autophosphorylation

    PubMed Central

    Zhang, Jiazhen; Clark, Kristopher; Lawrence, Toby; Peggie, Mark W.; Cohen, Philip

    2014-01-01

    IKKβ {IκB [inhibitor of NF-κB (nuclear factor κB)] kinase β} is required to activate the transcription factor NF-κB, but how IKKβ itself is activated in vivo is still unclear. It was found to require phosphorylation by one or more ‘upstream’ protein kinases in some reports, but by autophosphorylation in others. In the present study, we resolve this contro-versy by demonstrating that the activation of IKKβ induced by IL-1 (interleukin-1) or TNF (tumour necrosis factor) in embryonic fibroblasts, or by ligands that activate Toll-like receptors in macrophages, requires two distinct phosphorylation events: first, the TAK1 [TGFβ (transforming growth factor β)-activated kinase-1]-catalysed phosphorylation of Ser177 and, secondly, the IKKβ-catalysed autophosphorylation of Ser181. The phosphorylation of Ser177 by TAK1 is a priming event required for the subsequent autophosphorylation of Ser181, which enables IKKβ to phosphorylate exogenous substrates. We also provide genetic evidence which indicates that the IL-1-stimulated, LUBAC (linear ubiquitin chain assembly complex)-catalysed formation of linear ubiquitin chains and their interaction with the NEMO (NF-κB essential modulator) component of the canonical IKK complex permits the TAK1-catalysed priming phosphorylation of IKKβ at Ser177 and IKKα at Ser176. These findings may be of general significance for the activation of other protein kinases. PMID:24911653

  3. Theoretical stability and control characteristics of wings with various amounts of taper and twist

    NASA Technical Reports Server (NTRS)

    Pearson, Henry A; Jones, Robert T

    1938-01-01

    Stability derivatives have been computed for twisted wings of different plan forms that include variations in both the wing taper and the aspect ratio. Taper ratios of 1.0, 0,50, and 0.25 are considered for each of three aspect ratios: 6, 10, and 16. The specific derivatives for which results are given are the rolling-moment and the yawing-moment derivatives with respect to (a) rolling velocity, (b) yawing velocity, and (c) angle of sideslip. These results are given in such a form that the effect of any initial symmetrical wing twist (such as may be produced by flaps) on the derivatives may easily be taken into account. In addition to the stability derivatives, results are included for determining the theoretical rolling moment due to aileron deflection and a series of influence lines is given by which the loading across the span may be determined for any angle-of-attack distribution that may occur on the wing plan forms considered. The report also includes incidental references to the application of the results.

  4. a New X-Actuator Design for Dual Bending/twisting Control of Wings

    NASA Astrophysics Data System (ADS)

    TZOU, H. S.; YE, R.; DING, J. H.

    2001-03-01

    Recent development of smart structures and structronic systems has demonstrated the technology in many engineering applications. Active structural control of aircraft wings or helicopter blades (e.g., shapes, flaps, leading and/or trailing edges) can significantly enhance the aerodynamic efficiency and flight maneuverability of high-performance airplanes and helicopters. This paper is to evaluate the dual bending and torsion vibration control effects of an X-actuator configuration reconfigured from a parallel configuration. The finite element (FE) formulation of a new FE using the layerwise constant shear angle theory is reviewed and the derived governing equations are discussed. Bending and torsion control effects of plates are studied using the FE method and also demonstrated via laboratory experiments. The FE and experimental results both suggest the X-actuator is effective for both bending and torsion control of plates.

  5. A method for controlling the synthesis of stable twisted two-dimensional conjugated molecules.

    PubMed

    Li, Yongjun; Jia, Zhiyu; Xiao, Shengqiang; Liu, Huibiao; Li, Yuliang

    2016-01-01

    Thermodynamic stabilization (π-electron delocalization through effective conjugation) and kinetic stabilization (blocking the most-reactive sites) are important considerations when designing stable polycyclic aromatic hydrocarbons displaying tunable optoelectronic properties. Here, we demonstrate an efficient method for preparing a series of stable two-dimensional (2D) twisted dibenzoterrylene-acenes. We investigated their electronic structures and geometries in the ground state through various experiments assisted by calculations using density functional theory. We find that the length of the acene has a clear effect on the photophysical, electrochemical, and magnetic properties. These molecules exhibit tunable ground-state structures, in which a stable open-shell quintet tetraradical can be transferred to triplet diradicals. Such compounds are promising candidates for use in nonlinear optics, field effect transistors and organic spintronics; furthermore, they may enable broader applications of 2D small organic molecules in high-performance electronic and optical devices. PMID:27181692

  6. A method for controlling the synthesis of stable twisted two-dimensional conjugated molecules

    PubMed Central

    Li, Yongjun; Jia, Zhiyu; Xiao, Shengqiang; Liu, Huibiao; Li, Yuliang

    2016-01-01

    Thermodynamic stabilization (π-electron delocalization through effective conjugation) and kinetic stabilization (blocking the most-reactive sites) are important considerations when designing stable polycyclic aromatic hydrocarbons displaying tunable optoelectronic properties. Here, we demonstrate an efficient method for preparing a series of stable two-dimensional (2D) twisted dibenzoterrylene-acenes. We investigated their electronic structures and geometries in the ground state through various experiments assisted by calculations using density functional theory. We find that the length of the acene has a clear effect on the photophysical, electrochemical, and magnetic properties. These molecules exhibit tunable ground-state structures, in which a stable open-shell quintet tetraradical can be transferred to triplet diradicals. Such compounds are promising candidates for use in nonlinear optics, field effect transistors and organic spintronics; furthermore, they may enable broader applications of 2D small organic molecules in high-performance electronic and optical devices. PMID:27181692

  7. Twisted baskets.

    PubMed

    Hermann, Keith; Pratumyot, Yaowalak; Polen, Shane; Hardin, Alex M; Dalkilic, Erdin; Dastan, Arif; Badjić, Jovica D

    2015-02-23

    A preparative procedure for obtaining a pair of twisted molecular baskets, each comprising a chiral framework with either right ((P)-1syn) or left ((M)-1syn) sense of twist and six ester groups at the rim has been developed and optimized. The racemic (P/M)-1syn can be obtained in three synthetic steps from accessible starting materials. The resolution of (P/M)-1syn is accomplished by its transesterification with (1R,2S,5R)-(-)-menthol in the presence of a Ti(IV) catalyst to give diastereomeric 8(P) and 8(M). It was found that dendritic-like cavitands 8(P) and 8(M), in CD2Cl2, undergo self-inclusion ((1)H NMR spectroscopy) with a menthol moiety occupying the cavity of each host. Importantly, the degree of inclusion of the menthol group was ((1)H NMR spectroscopy) found to be greater in the case of 8(P) than 8(M). Accordingly, it is suggested that different folding characteristic of 8(P) and 8(M) ought to affect the physicochemical characteristics of the hosts to permit their effective separation by column chromatography. The absolute configuration of 8(P)/8(M), encompassing right- and left-handed "cups", was determined with the exciton chirality method and also verified in silico (DFT: B3LYP/TZVP). Finally, the twisted baskets are strongly fluorescent due to three naphthalene chromophores, having a high fluorescence quantum yield within the rigid framework of 8(P)/8(M). PMID:25604262

  8. Generalizing twisted gauge invariance

    SciTech Connect

    Duenas-Vidal, Alvaro; Vazquez-Mozo, Miguel A.

    2009-05-01

    We discuss the twisting of gauge symmetry in noncommutative gauge theories and show how this can be generalized to a whole continuous family of twisted gauge invariances. The physical relevance of these twisted invariances is discussed.

  9. Twisted intramolecular charge transfer and its contribution to the NLO activity of Diglycine Picrate: A vibrational spectroscopic study

    NASA Astrophysics Data System (ADS)

    Alen, S.; Sajan, D.; Umadevi, T.; Němec, Ivan; Baburaj, M. S.; Bena Jothy, V.; Selin Joy, B. H.

    2015-01-01

    Single crystals of Diglycine Picrate (DGLP) were grown by slow evaporation technique and the vibrational spectral analysis is carried out using FT Raman and FT-IR spectroscopy, supported by Density Functional Theoretical (DFT) computations to derive equilibrium geometry, vibrational wavenumbers and first hyperpolarizability. The vibrational spectra confirm the existence of NH3+ in DGLP. The influence of Twisted Intramolecular Charge Transfer (TICT) caused by the strong ionic ground state hydrogen bonding between charged species making DGLP crystal to have the non-centrosymmetric structure has been discussed. The Natural Bond Orbital (NBO) analysis confirms the occurrence of strong intermolecular Nsbnd H⋯O hydrogen bond. The HOMO-LUMO energy gap and the first order hyperpolarizability were calculated and it supports the nonlinear optical activity of the Diglycine Picrate crystal.

  10. Twisted intramolecular charge transfer and its contribution to the NLO activity of Diglycine Picrate: a vibrational spectroscopic study.

    PubMed

    Alen, S; Sajan, D; Umadevi, T; Němec, Ivan; Baburaj, M S; Bena Jothy, V; Selin Joy, B H

    2015-01-25

    Single crystals of Diglycine Picrate (DGLP) were grown by slow evaporation technique and the vibrational spectral analysis is carried out using FT Raman and FT-IR spectroscopy, supported by Density Functional Theoretical (DFT) computations to derive equilibrium geometry, vibrational wavenumbers and first hyperpolarizability. The vibrational spectra confirm the existence of NH3(+) in DGLP. The influence of Twisted Intramolecular Charge Transfer (TICT) caused by the strong ionic ground state hydrogen bonding between charged species making DGLP crystal to have the non-centrosymmetric structure has been discussed. The Natural Bond Orbital (NBO) analysis confirms the occurrence of strong intermolecular N-H⋯O hydrogen bond. The HOMO-LUMO energy gap and the first order hyperpolarizability were calculated and it supports the nonlinear optical activity of the Diglycine Picrate crystal. PMID:25137250

  11. Anisotropic piezoelectric twist actuation of helicopter rotor blades: Aeroelastic analysis and design optimization

    NASA Astrophysics Data System (ADS)

    Wilkie, William Keats

    1997-12-01

    An aeroelastic model suitable for control law and preliminary structural design of composite helicopter rotor blades incorporating embedded anisotropic piezoelectric actuator laminae is developed. The aeroelasticity model consists of a linear, nonuniform beam representation of the blade structure, including linear piezoelectric actuation terms, coupled with a nonlinear, finite-state unsteady aerodynamics model. A Galerkin procedure and numerical integration in the time domain are used to obtain a soluti An aeroelastic model suitable for control law and preliminary structural design of composite helicopter rotor blades incorporating embedded anisotropic piezoelectric actuator laminae is developed. The aeroelasticity model consists of a linear, nonuniform beam representation of the blade structure, including linear piezoelectric actuation terms, coupled with a nonlinear, finite-state unsteady aerodynamics model. A Galerkin procedure and numerical integration in the time domain are used to obtain amited additional piezoelectric material mass, it is shown that blade twist actuation approaches which exploit in-plane piezoelectric free-stain anisotropies are capable of producing amplitudes of oscillatory blade twisting sufficient for rotor vibration reduction applications. The second study examines the effectiveness of using embedded piezoelectric actuator laminae to alleviate vibratory loads due to retreating blade stall. A 10 to 15 percent improvement in dynamic stall limited forward flight speed, and a 5 percent improvement in stall limited rotor thrust were numerically demonstrated for the active twist rotor blade relative to a conventional blade design. The active twist blades are also demonstrated to be more susceptible than the conventional blades to dynamic stall induced vibratory loads when not operating with twist actuation. This is the result of designing the active twist blades with low torsional stiffness in order to maximize piezoelectric twist authority

  12. [Twisted noses].

    PubMed

    Thomassin, J-M; Radulesco, T; Bardot, J

    2014-12-01

    Correction of a twisted or crooked nose can be very complex and require the use of a broad range of surgical techniques. Patient needs are often mixed--aesthetic and functional--particularly in post-trauma cases. The quality of postoperative breathing is therefore as important as correction of the nasal deviation. Extracorporeal septoplasty or spreader grafts are very effective not only in correction of the nasal pyramid deformation, but also in resolution of functional respiratory issues. Reconstruction and proper support of the septum are necessary components for a straight nose. Aesthetic deformation can be difficult to correct owing to the memory of the bone and cartilage. Although minor deformations can be corrected with simple techniques, a more aggressive procedure is often necessary in the most complex cases. Despite attempts to correct deformation thanks to the various techniques described here, a postoperative deviation can persist. Preoperative discussion is very important and enables the surgeon to explain to the patient that it is very difficult to obtain a perfectly straight nose. PMID:25174875

  13. Adaptive flight control surfaces, wings, rotors, and active aerodynamics

    NASA Astrophysics Data System (ADS)

    Barrett, Ronald M.; Brozoski, Fred

    1996-05-01

    This study outlines active flight control materials, structural arrangements, and several new active flight control methods for rotorcraft, airplanes and missiles. A system-level comparison shows that flight control actuator systems using materials like piezoceramics have approximately double the mass-specific energy and 4 to 6 times the volume specific energy of conventional actuators. New fabrication techniques centered on the principal of directional attachment allow wings and rotor blades to become twist active. Using these new methods, directionally attached piezoelectric (DAP) actuator elements were built into graphite-epoxy sandwich structures. When compared to conventionally attached piezoelectric (CAP) elements, twist deflections (important for flight control) of DAP plates were an order of magnitude greater. By using such twist-active elements in a torque-plate configuration, an active helicopter rotor was built. This Froude-scaled solid state rotor was whirl-stand tested and showed steady blade pitch deflections in excess of plus or minus 8 degrees with good correlation between theory and experiment rates up to 42 Hz (which corresponded to 2.5/rev) and no degradation in deflection as RPM was increased. DAP elements were also used in high aspect ratio subsonic and supersonic wings, demonstrating static twist deflections of plus or minus 2 degrees and plus or minus 6 degrees respectively, with good correlation between experiment and finite element results. The final section compares all-moving active stabilator structural arrangements and pitch deflections, which range up to plus or minus 12 degrees, generating lift coefficient changes in excess of plus or minus 0.8.

  14. Twisted supersymmetry: Twisted symmetry versus renormalizability

    SciTech Connect

    Dimitrijevic, Marija; Nikolic, Biljana; Radovanovic, Voja

    2011-03-15

    We discuss a deformation of superspace based on a Hermitian twist. The twist implies a *-product that is noncommutative, Hermitian and finite when expanded in a power series of the deformation parameter. The Leibniz rule for the twisted supersymmetry transformations is deformed. A minimal deformation of the Wess-Zumino action is proposed and its renormalizability properties are discussed. There is no tadpole contribution, but the two-point function diverges. We speculate that the deformed Leibniz rule, or more generally the twisted symmetry, interferes with renormalizability properties of the model. We discuss different possibilities to render a renormalizable model.

  15. Super-twisting sliding mode differentiation for improving PD controllers performance of second order systems.

    PubMed

    Salgado, Ivan; Chairez, Isaac; Camacho, Oscar; Yañez, Cornelio

    2014-07-01

    Designing a proportional derivative (PD) controller has as main problem, to obtain the derivative of the output error signal when it is contaminated with high frequency noises. To overcome this disadvantage, the supertwisting algorithm (STA) is applied in closed-loop with a PD structure for multi-input multi-output (MIMO) second order nonlinear systems. The stability conditions were analyzed in terms of a strict non-smooth Lyapunov function and the solution of Riccati equations. A set of numerical test was designed to show the advantages of implementing PD controllers that used STA as a robust exact differentiator. The first numerical example showed the stabilization of an inverted pendulum. The second example was designed to solve the tracking problem of a two-link robot manipulator. PMID:24856778

  16. Coupled CFD/CSD Analysis of an Active-Twist Rotor in a Wind Tunnel with Experimental Validation

    NASA Technical Reports Server (NTRS)

    Massey, Steven J.; Kreshock, Andrew R.; Sekula, Martin K.

    2015-01-01

    An unsteady Reynolds averaged Navier-Stokes analysis loosely coupled with a comprehensive rotorcraft code is presented for a second-generation active-twist rotor. High fidelity Navier-Stokes results for three configurations: an isolated rotor, a rotor with fuselage, and a rotor with fuselage mounted in a wind tunnel, are compared to lifting-line theory based comprehensive rotorcraft code calculations and wind tunnel data. Results indicate that CFD/CSD predictions of flapwise bending moments are in good agreement with wind tunnel measurements for configurations with a fuselage, and that modeling the wind tunnel environment does not significantly enhance computed results. Actuated rotor results for the rotor with fuselage configuration are also validated for predictions of vibratory blade loads and fixed-system vibratory loads. Varying levels of agreement with wind tunnel measurements are observed for blade vibratory loads, depending on the load component (flap, lag, or torsion) and the harmonic being examined. Predicted trends in fixed-system vibratory loads are in good agreement with wind tunnel measurements.

  17. Sterically-controlled intermolecular Friedel-Crafts acylation with twisted amides via selective N-C cleavage under mild conditions.

    PubMed

    Liu, Yongmei; Meng, Guangrong; Liu, Ruzhang; Szostak, Michal

    2016-05-21

    Highly chemoselective Friedel-Crafts acylation with twisted amides under mild conditions is reported for the first time. The reaction shows high functional group tolerance, obviating the need for preformed sensitive organometallic reagents and expensive transition metal catalysts. The high reactivity of amides is switched on by ground-state steric distortion to disrupt the amide bond nN→πCO* resonance as a critical design feature. Conceptually, this new acid-promoted mechanism of twisted amides provides direct access to bench-stable acylating reagents under mild, metal-free conditions. PMID:27139813

  18. Polarization twist in perovskite ferrielectrics.

    PubMed

    Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2016-01-01

    Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of 'polarization twist', which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms. PMID:27586824

  19. Twisted split-ring-resonator photonic metamaterial with huge optical activity.

    PubMed

    Decker, M; Zhao, R; Soukoulis, C M; Linden, S; Wegener, M

    2010-05-15

    Coupled split-ring-resonator metamaterials have previously been shown to exhibit large coupling effects, which are a prerequisite for obtaining large effective optical activity. By a suitable lateral arrangement of these building blocks, we completely eliminate linear birefringence and obtain pure optical activity and connected circular optical dichroism. Experiments around a 100 THz frequency and corresponding modeling are in good agreement. Rotation angles of about 30 degrees for 205 nm sample thickness are derived. PMID:20479819

  20. Twist-controlled resonant tunnelling in graphene/boron nitride/graphene heterostructures

    NASA Astrophysics Data System (ADS)

    Mishchenko, A.; Tu, J. S.; Cao, Y.; Gorbachev, R. V.; Wallbank, J. R.; Greenaway, M. T.; Morozov, V. E.; Morozov, S. V.; Zhu, M. J.; Wong, S. L.; Withers, F.; Woods, C. R.; Kim, Y.-J.; Watanabe, K.; Taniguchi, T.; Vdovin, E. E.; Makarovsky, O.; Fromhold, T. M.; Fal'Ko, V. I.; Geim, A. K.; Eaves, L.; Novoselov, K. S.

    2014-10-01

    Recent developments in the technology of van der Waals heterostructures made from two-dimensional atomic crystals have already led to the observation of new physical phenomena, such as the metal-insulator transition and Coulomb drag, and to the realization of functional devices, such as tunnel diodes, tunnel transistors and photovoltaic sensors. An unprecedented degree of control of the electronic properties is available not only by means of the selection of materials in the stack, but also through the additional fine-tuning achievable by adjusting the built-in strain and relative orientation of the component layers. Here we demonstrate how careful alignment of the crystallographic orientation of two graphene electrodes separated by a layer of hexagonal boron nitride in a transistor device can achieve resonant tunnelling with conservation of electron energy, momentum and, potentially, chirality. We show how the resonance peak and negative differential conductance in the device characteristics induce a tunable radiofrequency oscillatory current that has potential for future high-frequency technology.

  1. The twisted top

    NASA Astrophysics Data System (ADS)

    Thiffeault, Jean-Luc; Morrison, P. J.

    2001-05-01

    We describe a new type of top, the twisted top, obtained by appending a cocycle to the Lie-Poisson bracket for the charged heavy top, thus breaking its semidirect product structure. The twisted top has an integrable case that corresponds to the Lagrange (symmetric) top. We give a canonical description of the twisted top in terms of Euler angles. We also show by a numerical calculation of the largest Lyapunov exponent that the Kovalevskaya case of the twisted top is chaotic.

  2. Twist within a somersault.

    PubMed

    Mikl, Joanne; Rye, David C

    2016-02-01

    The twisting somersault is a key skill in diving and gymnastics. The components of twist and somersault are defined with respect to anatomical axes, and combinations of multiples of half rotations of twist and somersault define specific twisting somersault skills. To achieve a twisting somersault skill twist must be continuous; otherwise oscillations in twist while somersaulting may be observed. The posture-dependent inertial properties of the athlete and the initial conditions determine if continuous or oscillating twist is observed. The paper derives equations for the amount of somersault required per half twist, or per twist oscillation, without making assumptions about the relative magnitudes of the moments of inertia. From these equations the skills achievable may be determined. The error associated with the common assumption that the medial and transverse principal moments of inertia are equal is explored. It is concluded that the error grows as the number of twists per somersault decreases, when the medial and transverse moments of inertia diverge, and when the longitudinal moment of inertia approaches either the medial or transverse moment of inertia. Inertial property data for an example athlete are used to illustrate the various rotational states that can occur. PMID:26583967

  3. MACC-1 Promotes Endothelium-Dependent Angiogenesis in Gastric Cancer by Activating TWIST1/VEGF-A Signal Pathway

    PubMed Central

    Zhao, Yang; Dong, Shaoting; Zhang, Jingwen; Luo, Yuhao; Huang, Na; Shi, Min; Bin, Jianping; Liao, Yulin; Liao, Wangjun

    2016-01-01

    Endothelium-dependent angiogenesis is thought to be a crucial step in cancer progression. We previously reported that metastasis-associated in colon cancer-1 (MACC1) contributed to the vasculogenic mimicry in gastric cancer (GC), but it remains unknown whether MACC1 promotes endothelium-dependent angiogenesis of GC and whether TWIST1 is involved in this process. In the present study, we detected MACC1 expression and microvessel density (MVD) by immunohistochemistry in 159 patients with stage I-III GC, and investigated the role of TWIST1 and vascular endothelial growth factor A (VEGF-A) in MACC1-induced endothelium-dependent angiogenesis using nude mice with GC xenografts, and human umbilical vein endothelial cells (HUVECs) that were co-cultured with conditioned media from overexpression and interference MACC1 GC cells. We found that MACC1 expression was positively correlated with an increased MVD and tumor recurrence in GC patients. In GC xenograft models, MACC1 elevated MVD and upregulated the expression of VEGF-A as well as accelerated tumor growth. In addition, MACC1 obviously increased the expression of TWIST1 and induced tube-like formation of HUVECs, whereas attenuation of TWIST1 suppressed the protein expression of VEGF-A and repealed the effect of MACC1 on tube formation. Our findings shed light on the function of MACC1 in endothelium-dependent angiogenesis of GC and suggest potential prognostic and therapeutic value. PMID:27280289

  4. The Invariant Twist of Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes; Gabuzda, Denise C.

    2009-01-01

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in Active Galactic Nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1 %. This lends support to the hypothesis that the Universe is seeded by B fields that are generated in AGN via this mechanism

  5. THE INVARIANT TWIST OF MAGNETIC FIELDS IN THE RELATIVISTIC JETS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes E-mail: dimitris_christodoulou@uml.edu E-mail: gabuzda@physics.ucc.ie

    2009-09-10

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in active galactic nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1%. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.

  6. Down regulation of Akirin-2 increases chemosensitivity in human glioblastomas more efficiently than Twist-1.

    PubMed

    Krossa, Sebastian; Schmitt, Anne Dorothée; Hattermann, Kirsten; Fritsch, Jürgen; Scheidig, Axel J; Mehdorn, Hubertus Maximilian; Held-Feindt, Janka

    2015-08-28

    The Twist-1 transcription factor and its interacting protein Akirin-2 regulate apoptosis. We found that in glioblastomas, highly malignant brain tumors, Akirin-2 and Twist-1 were expressed in glial fibrillary acidic protein positive tumor regions as well as in tumor endothelial cells and infiltrating macrophages / microglia. Temozolomide (TMZ) induced the expression of both molecules, partly shifting their nuclear to cytosolic localization. The knock-down (kd) of Akirin-2 increased the activity of cleaved (c)Caspase-3/-7, the amounts of cCaspases-3, -7 and cPARP-1 and resulted in an increased number of apoptotic cells after TMZ exposure. Glioblastoma cells containing decreased amounts of Akirin-2 after kd contained increased amounts of cCaspase-3 as determined by the ImageStreamx Mark II technology. For Twist-1, similar results were obtained with the exception that the combination of TMZ treatment and Twist-1 kd failed to significantly reduce chemoresistance compared with controls. This could be attributed to a cell population containing only slightly increased cCaspase-3 together with decreased Twist-1 levels, which was clearly larger than the respective population observed under Akirin-2 kd. Our results showed that, compared with Twist-1, Akirin-2 is the more promising target for RNAi strategies antagonizing Twist-1/Akirin-2 facilitated glioblastoma cell survival. PMID:26036627

  7. Down regulation of Akirin-2 increases chemosensitivity in human glioblastomas more efficiently than Twist-1

    PubMed Central

    Krossa, Sebastian; Schmitt, Anne Dorothée; Hattermann, Kirsten; Fritsch, Jürgen; Scheidig, Axel J.; Mehdorn, Hubertus Maximilian; Held-Feindt, Janka

    2015-01-01

    The Twist-1 transcription factor and its interacting protein Akirin-2 regulate apoptosis. We found that in glioblastomas, highly malignant brain tumors, Akirin-2 and Twist-1 were expressed in glial fibrillary acidic protein positive tumor regions as well as in tumor endothelial cells and infiltrating macrophages / microglia. Temozolomide (TMZ) induced the expression of both molecules, partly shifting their nuclear to cytosolic localization. The knock-down (kd) of Akirin-2 increased the activity of cleaved (c)Caspase-3/-7, the amounts of cCaspases-3, -7 and cPARP-1 and resulted in an increased number of apoptotic cells after TMZ exposure. Glioblastoma cells containing decreased amounts of Akirin-2 after kd contained increased amounts of cCaspase-3 as determined by the ImageStreamx Mark II technology. For Twist-1, similar results were obtained with the exception that the combination of TMZ treatment and Twist-1 kd failed to significantly reduce chemoresistance compared with controls. This could be attributed to a cell population containing only slightly increased cCaspase-3 together with decreased Twist-1 levels, which was clearly larger than the respective population observed under Akirin-2 kd. Our results showed that, compared with Twist-1, Akirin-2 is the more promising target for RNAi strategies antagonizing Twist-1/Akirin-2 facilitated glioblastoma cell survival. PMID:26036627

  8. "Oliver Twist": A Teacher's Guide.

    ERIC Educational Resources Information Center

    Cashion, Carol; Fischer, Diana

    This teacher's guide for public television's 3-part adaptation of Charles Dickens's "Oliver Twist" provides information that will help enrich students' viewing of the series, whether or not they read the novel. The guide includes a wide range of discussion and activity ideas; there is also a series Web site and a list of Web resources.…

  9. Twist1-induced invadopodia formation promotes tumor metastasis

    PubMed Central

    Eckert, Mark A.; Lwin, Thinzar M.; Chang, Andrew T.; Kim, Jihoon; Danis, Etienne; Ohno-Machado, Lucila; Yang, Jing

    2011-01-01

    Summary The Twist1 transcription factor is known to promote tumor metastasis and induce Epithelial-Mesenchymal Transition (EMT). Here, we report that Twist1 is capable of promoting the formation of invadopodia, specialized membrane protrusions for extracellular matrix degradation. Twist1 induces PDGFRα expression, which in turn activates Src, to promote invadopodia formation. We show that Twist1 and PDGFRα are central mediators of invadopodia formation in response to various EMT-inducing signals. Induction of PDGFRα and invadopodia is essential for Twist1 to promote tumor metastasis. Consistent with PDGFRα being a direct transcriptional target of Twist1, coexpression of Twist1 and PDGFRα predicts poor survival in breast tumor patients. Therefore, invadopodia-mediated matrix degradation is a key function of Twist1 in promoting tumor metastasis. PMID:21397860

  10. Ribozyme Catalysis with a Twist: Active State of the Twister Ribozyme in Solution Predicted from Molecular Simulation.

    PubMed

    Gaines, Colin S; York, Darrin M

    2016-03-01

    We present results from molecular dynamics simulations and free energy calculations of the twister ribozyme at different stages along the reaction path to gain insight into its mechanism. The results, together with recent biochemical experiments, provide support for a mechanism involving general-acid catalysis by a conserved adenine residue in the active site. Although adenine has been previously implicated as a general acid acting through the N1 position in other ribozymes such as the hairpin and VS ribozymes, in the twister ribozyme there may be a twist. Biochemical experiments suggest that general acid catalysis may occur through the N3 position, which has never before been implicated in this role; however, currently, there is a lack of a detailed structural model for the active state of the twister ribozyme in solution that is consistent with these and other experiments. Simulations in a crystalline environment reported here are consistent with X-ray crystallographic data, and suggest that crystal packing contacts trap the RNA in an inactive conformation with U-1 in an extruded state that is incompatible with an in-line attack to the scissile phosphate. Simulations in solution, on the other hand, reveal this region to be dynamic and able to adopt a conformation where U-1 is stacked with G33. In this state, the nucleophile is in line with the scissile phosphate, and the N1 position of G33 and N3 position of A1 are poised to act as a general base and acid, respectively, as supported by mutational experiments. Free energy calculations further predict the electrostatic environment causes a shift of the microscopic pKa at the N3 position of A1 toward neutrality by approximately 5 pKa units. These results offer a unified interpretation of a broad range of currently available experimental data that points to a novel mode of general acid catalysis through the N3 position of an adenine nucleobase, thus expanding the repertoire of known mechanistic strategies employed by

  11. Active multistable twisting device

    NASA Technical Reports Server (NTRS)

    Schultz, Marc R. (Inventor)

    2008-01-01

    Two similarly shaped, such as rectangular, shells are attached to one another such that they form a resulting thin airfoil-like structure. The resulting device has at least two stable equilibrium shapes. The device can be transformed from one shape to another with a snap-through action. One or more actuators can be used to effect the snap-through; i.e., transform the device from one stable shape to another. Power to the actuators is needed only to transform the device from one shape to another.

  12. Cord blood stem cells revert glioma stem cell EMT by down regulating transcriptional activation of Sox2 and Twist1

    PubMed Central

    Velpula, Kiran Kumar; Dasari, Venkata Ramesh; Tsung, Andrew J.; Dinh, Dzung H.; Rao, Jasti S.

    2011-01-01

    The dynamic nature of cancer stem cells that underlie metastasis or their ability to switch between different cellular identities, as in EMT and MET, has profound implications for cancer therapy. The functional relationship between molecules involved in cancer cell stemness and metastasis is not clear. In this regard, our studies on hGBM tissue grade IV specimens showed significant expression of Twist1 and Sox2, known mesenchymal and stemness related markers, respectively, indicating their association with glial tumor genesis and metastasis. The glioma stem cells obtained from CD133+ cells demonstrated increased expression of Twist1 and Sox2 accompanied by significant increase in the mesenchymal markers such as N-cadherin, vimentin and β-catenin. Our studies on glioma stem cells treatment with human umbilical cord blood derived- mesenchymal stem cells, showed down regulation of Twist1 and Sox2 proteins, apart from other mesenchymal stem cell markers. Based on the in vitro experiments and in vivo intracranial xenograft mouse model studies, we elucidated the potential therapeutic role of hUCBSC in suppressing glioma cancer stemness by the induction of MET. PMID:22184289

  13. Cord blood stem cells revert glioma stem cell EMT by down regulating transcriptional activation of Sox2 and Twist1.

    PubMed

    Velpula, Kiran Kumar; Dasari, Venkata Ramesh; Tsung, Andrew J; Dinh, Dzung H; Rao, Jasti S

    2011-12-01

    The dynamic nature of cancer stem cells that underlie metastasis or their ability to switch between different cellular identities, as in EMT and MET, has profound implications for cancer therapy. The functional relationship between molecules involved in cancer cell stemness and metastasis is not clear. In this regard, our studies on hGBM tissue grade IV specimens showed significant expression of Twist1 and Sox2, known mesenchymal and stemness related markers, respectively, indicating their association with glial tumor genesis and metastasis. The glioma stem cells obtained from CD133+ cells demonstrated increased expression of Twist1 and Sox2 accompanied by significant increase in the mesenchymal markers such as N-cadherin, vimentin and β-catenin. Our studies on glioma stem cells treatment with human umbilical cord blood derived- mesenchymal stem cells, showed down regulation of Twist1 and Sox2 proteins, apart from other mesenchymal stem cell markers. Based on the in vitro experiments and in vivo intracranial xenograft mouse model studies, we elucidated the potential therapeutic role of hUCBSC in suppressing glioma cancer stemness by the induction of MET. PMID:22184289

  14. Perversions with a twist

    PubMed Central

    Silva, Pedro E. S.; Trigueiros, Joao L.; Trindade, Ana C.; Simoes, Ricardo; Dias, Ricardo G.; Godinho, Maria Helena; de Abreu, Fernao Vistulo

    2016-01-01

    Perversions connecting two helices with symmetric handedness are a common occurrence in nature, for example in tendrils. These defects can be found in our day life decorating ribbon gifts or when plants use tendrils to attach to a support. Perversions arise when clamped elastic filaments coil into a helical shape but have to conserve zero overall twist. We investigate whether other types of perversions exist and if they display different properties. Here we show mathematically and experimentally that a continuous range of different perversions can exist and present different geometries. Experimentally, different perversions were generated using micro electrospun fibres. Our experimental results also confirm that these perversions behave differently upon release and adopt different final configurations. These results also demonstrate that it is possible to control on demand the formation and shape of microfilaments, in particular, of electrospun fibres by using ultraviolet light. PMID:27025549

  15. Perversions with a twist

    NASA Astrophysics Data System (ADS)

    Silva, Pedro E. S.; Trigueiros, Joao L.; Trindade, Ana C.; Simoes, Ricardo; Dias, Ricardo G.; Godinho, Maria Helena; de Abreu, Fernao Vistulo

    2016-03-01

    Perversions connecting two helices with symmetric handedness are a common occurrence in nature, for example in tendrils. These defects can be found in our day life decorating ribbon gifts or when plants use tendrils to attach to a support. Perversions arise when clamped elastic filaments coil into a helical shape but have to conserve zero overall twist. We investigate whether other types of perversions exist and if they display different properties. Here we show mathematically and experimentally that a continuous range of different perversions can exist and present different geometries. Experimentally, different perversions were generated using micro electrospun fibres. Our experimental results also confirm that these perversions behave differently upon release and adopt different final configurations. These results also demonstrate that it is possible to control on demand the formation and shape of microfilaments, in particular, of electrospun fibres by using ultraviolet light.

  16. Perversions with a twist.

    PubMed

    Silva, Pedro E S; Trigueiros, Joao L; Trindade, Ana C; Simoes, Ricardo; Dias, Ricardo G; Godinho, Maria Helena; de Abreu, Fernao Vistulo

    2016-01-01

    Perversions connecting two helices with symmetric handedness are a common occurrence in nature, for example in tendrils. These defects can be found in our day life decorating ribbon gifts or when plants use tendrils to attach to a support. Perversions arise when clamped elastic filaments coil into a helical shape but have to conserve zero overall twist. We investigate whether other types of perversions exist and if they display different properties. Here we show mathematically and experimentally that a continuous range of different perversions can exist and present different geometries. Experimentally, different perversions were generated using micro electrospun fibres. Our experimental results also confirm that these perversions behave differently upon release and adopt different final configurations. These results also demonstrate that it is possible to control on demand the formation and shape of microfilaments, in particular, of electrospun fibres by using ultraviolet light. PMID:27025549

  17. Polarization twist in perovskite ferrielectrics

    PubMed Central

    Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2016-01-01

    Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms. PMID:27586824

  18. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    NASA Astrophysics Data System (ADS)

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-05-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating.

  19. Supramolecular block copolymers by kinetically controlled co-self-assembly of planar and core-twisted perylene bisimides

    PubMed Central

    Görl, Daniel; Zhang, Xin; Stepanenko, Vladimir; Würthner, Frank

    2015-01-01

    New synthetic methodologies for the formation of block copolymers have revolutionized polymer science within the last two decades. However, the formation of supramolecular block copolymers composed of alternating sequences of larger block segments has not been realized yet. Here we show by transmission electron microscopy (TEM), 2D NMR and optical spectroscopy that two different perylene bisimide dyes bearing either a flat (A) or a twisted (B) core self-assemble in water into supramolecular block copolymers with an alternating sequence of (AmBB)n. The highly defined ultralong nanowire structure of these supramolecular copolymers is entirely different from those formed upon self-assembly of the individual counterparts, that is, stiff nanorods (A) and irregular nanoworms (B), respectively. Our studies further reveal that the as-formed supramolecular block copolymer constitutes a kinetic self-assembly product that transforms into thermodynamically more stable self-sorted homopolymers upon heating. PMID:25959777

  20. A twist of insight - the role of Twist-family bHLH factors in development

    PubMed Central

    BARNES, RALSTON M.; FIRULLI, ANTHONY B.

    2009-01-01

    Members of the Twist-family of bHLH proteins play a pivotal role in a number of essential developmental programs. Twist-family bHLH proteins function by dimerizing with other bHLH members and binding to cis- regulatory elements, called E-boxes. While Twist-family members may simply exhibit a preference in terms of high-affinity binding partners, a complex, multilevel cascade of regulation creates a dynamic role for these bHLH proteins. We summarize in this review information on each Twist-family member concerning expression pattern, function, regulation, downstream targets, and interactions with other bHLH proteins. Additionally, we focus on the phospho-regulatory mechanisms that tightly control posttranslational modification of Twist-family member bHLH proteins. PMID:19378251

  1. Twist effect and sensing of few mode polymer fibre Bragg gratings

    NASA Astrophysics Data System (ADS)

    Yan, Binbin; Luo, Yanhua; Bhowmik, Kishore; Rajan, Ginu; Ji, Minning; Wen, Jianxiang; Peng, Gang-Ding

    2016-01-01

    For the development of the twist sensor based on few mode polymer optical fibre (POF) gratings, we investigated the twist effect of few mode (FM) POF Bragg gratings with large twist, and found the twist effect on reflection is highly mode dependent-insignificant on the fundamental mode and considerable on higher order modes, which seems closely related to the symmetry of modal field. In addition, Bragg wavelengths of both the fundamental mode and higher modes red-shift with the twisting and blue-shift with the twist releasing, and they almost display the similar response trend without any mode dependence. Further analysis found that the red-shift of the Bragg wavelength should be attributed to the redistribution of the pre-strain applied upon the POF, activated by twist. Finally, based on the reflection response to the twist, one kind of twist sensing scheme with few mode POF gratings has been demonstrated, showing great potential as a twist sensor.

  2. Integral Twist Actuation of Helicopter Rotor Blades for Vibration Reduction

    NASA Technical Reports Server (NTRS)

    Shin, SangJoon; Cesnik, Carlos E. S.

    2001-01-01

    Active integral twist control for vibration reduction of helicopter rotors during forward flight is investigated. The twist deformation is obtained using embedded anisotropic piezocomposite actuators. An analytical framework is developed to examine integrally-twisted blades and their aeroelastic response during different flight conditions: frequency domain analysis for hover, and time domain analysis for forward flight. Both stem from the same three-dimensional electroelastic beam formulation with geometrical-exactness, and axe coupled with a finite-state dynamic inflow aerodynamics model. A prototype Active Twist Rotor blade was designed with this framework using Active Fiber Composites as the actuator. The ATR prototype blade was successfully tested under non-rotating conditions. Hover testing was conducted to evaluate structural integrity and dynamic response. In both conditions, a very good correlation was obtained against the analysis. Finally, a four-bladed ATR system is built and tested to demonstrate its concept in forward flight. This experiment was conducted at NASA Langley Tansonic Dynamics Tunnel and represents the first-of-a-kind Mach-scaled fully-active-twist rotor system to undergo forward flight test. In parallel, the impact upon the fixed- and rotating-system loads is estimated by the analysis. While discrepancies are found in the amplitude of the loads under actuation, the predicted trend of load variation with respect to its control phase correlates well. It was also shown, both experimentally and numerically, that the ATR blade design has the potential for hub vibratory load reduction of up to 90% using individual blade control actuation. Using the numerical framework, system identification is performed to estimate the harmonic transfer functions. The linear time-periodic system can be represented by a linear time-invariant system under the three modes of blade actuation: collective, longitudinal cyclic, and lateral cyclic. A vibration

  3. Twisting Neutron Waves

    NASA Astrophysics Data System (ADS)

    Pushin, Dmitry

    Most waves encountered in nature can be given a ``twist'', so that their phase winds around an axis parallel to the direction of wave propagation. Such waves are said to possess orbital angular momentum (OAM). For quantum particles such as photons, atoms, and electrons, this corresponds to the particle wavefunction having angular momentum of Lℏ along its propagation axis. Controlled generation and detection of OAM states of photons began in the 1990s, sparking considerable interest in applications of OAM in light and matter waves. OAM states of photons have found diverse applications such as broadband data multiplexing, massive quantum entanglement, optical trapping, microscopy, quantum state determination and teleportation, and interferometry. OAM states of electron beams have been used to rotate nanoparticles, determine the chirality of crystals and for magnetic microscopy. Here I discuss the first demonstration of OAM control of neutrons. Using neutron interferometry with a spatially incoherent input beam, we show the addition and conservation of quantum angular momenta, entanglement between quantum path and OAM degrees of freedom. Neutron-based quantum information science heretofore limited to spin, path, and energy degrees of freedom, now has access to another quantized variable, and OAM modalities of light, x-ray, and electron beams are extended to a massive, penetrating neutral particle. The methods of neutron phase imprinting demonstrated here expand the toolbox available for development of phase-sensitive techniques of neutron imaging. Financial support provided by the NSERC Create and Discovery programs, CERC and the NIST Quantum Information Program is acknowledged.

  4. Twisted Quantum Toroidal Algebras

    NASA Astrophysics Data System (ADS)

    Jing, Naihuan; Liu, Rongjia

    2014-09-01

    We construct a principally graded quantum loop algebra for the Kac-Moody algebra. As a special case a twisted analog of the quantum toroidal algebra is obtained together with the quantum Serre relations.

  5. Twisted partially pure spinors

    NASA Astrophysics Data System (ADS)

    Herrera, Rafael; Tellez, Ivan

    2016-08-01

    Motivated by the relationship between orthogonal complex structures and pure spinors, we define twisted partially pure spinors in order to characterize spinorially subspaces of Euclidean space endowed with a complex structure.

  6. Twisted Radio Waves and Twisted Thermodynamics

    PubMed Central

    Kish, Laszlo B.; Nevels, Robert D.

    2013-01-01

    We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momenta ‘twisted wave’ mode, to the far field in free space is therefore not possible. PMID:23424647

  7. 1Application of Fluorescence Resonance Energy Transfer and Magnetic Twisting Cytometry to Quantitate Mechano-Chemical Signaling Activities in a Living Cell

    PubMed Central

    Na, Sungsoo; Wang, Ning

    2009-01-01

    Mechanotransduction is the process by which living cells sense mechanical forces and then convert them into biochemical signaling. Recently we showed that mechanical stress is transduced from the cell surface to remote cytoplasmic sites within 0.3 s, which is at least 40 to 50 times faster than soluble factor-induced signal transduction, and the sites of mechanotransduction colocalize with sites where mechanical stress causes microtubule displacement. These results suggest that mechanotransduction employs mechanisms different from those of soluble factor-induced signal transduction. Here we describe a protocol that utilizes fluorescence resonance energy transfer (FRET) and a magnetic twisting cytometry (MTC) device to capture rapid mechano-chemical signaling activities in living cells. PMID:18728305

  8. A multiple-shape memory polymer-metal composite actuator capable of programmable control, creating complex 3D motion of bending, twisting, and oscillation

    PubMed Central

    Shen, Qi; Trabia, Sarah; Stalbaum, Tyler; Palmre, Viljar; Kim, Kwang; Oh, Il-Kwon

    2016-01-01

    Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. Here, we report an ionic polymer-metal composite actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, this capability only could be realized with existing actuator technologies by using multiple actuators or another robotic system. This paper introduces a soft multiple-shape-memory polymer-metal composite (MSMPMC) actuator having multiple degrees-of-freedom that demonstrates high maneuverability when controlled by two external inputs, electrical and thermal. These multiple inputs allow for complex motions that are routine in nature, but that would be otherwise difficult to obtain with a single actuator. To the best of the authors’ knowledge, this MSMPMC actuator is the first solitary actuator capable of multiple-input control and the resulting deformability and maneuverability. PMID:27080134

  9. A multiple-shape memory polymer-metal composite actuator capable of programmable control, creating complex 3D motion of bending, twisting, and oscillation.

    PubMed

    Shen, Qi; Trabia, Sarah; Stalbaum, Tyler; Palmre, Viljar; Kim, Kwang; Oh, Il-Kwon

    2016-01-01

    Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. Here, we report an ionic polymer-metal composite actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, this capability only could be realized with existing actuator technologies by using multiple actuators or another robotic system. This paper introduces a soft multiple-shape-memory polymer-metal composite (MSMPMC) actuator having multiple degrees-of-freedom that demonstrates high maneuverability when controlled by two external inputs, electrical and thermal. These multiple inputs allow for complex motions that are routine in nature, but that would be otherwise difficult to obtain with a single actuator. To the best of the authors' knowledge, this MSMPMC actuator is the first solitary actuator capable of multiple-input control and the resulting deformability and maneuverability. PMID:27080134

  10. A multiple-shape memory polymer-metal composite actuator capable of programmable control, creating complex 3D motion of bending, twisting, and oscillation

    NASA Astrophysics Data System (ADS)

    Shen, Qi; Trabia, Sarah; Stalbaum, Tyler; Palmre, Viljar; Kim, Kwang; Oh, Il-Kwon

    2016-04-01

    Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. Here, we report an ionic polymer-metal composite actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, this capability only could be realized with existing actuator technologies by using multiple actuators or another robotic system. This paper introduces a soft multiple-shape-memory polymer-metal composite (MSMPMC) actuator having multiple degrees-of-freedom that demonstrates high maneuverability when controlled by two external inputs, electrical and thermal. These multiple inputs allow for complex motions that are routine in nature, but that would be otherwise difficult to obtain with a single actuator. To the best of the authors’ knowledge, this MSMPMC actuator is the first solitary actuator capable of multiple-input control and the resulting deformability and maneuverability.

  11. The Small C-terminal Domain Phosphatase 1 Inhibits Cancer Cell Migration and Invasion by Dephosphorylating Ser(P)68-Twist1 to Accelerate Twist1 Protein Degradation.

    PubMed

    Sun, Tong; Fu, Junjiang; Shen, Tao; Lin, Xia; Liao, Lan; Feng, Xin-Hua; Xu, Jianming

    2016-05-27

    Twist1 is a basic helix-loop-helix transcription factor that strongly promotes epithelial-to-mesenchymal transition, migration, invasion, and metastasis of cancer cells. The MAPK-phosphorylated Twist1 on its serine 68 (Ser(P)(68)-Twist1) has a significantly enhanced stability and function to drive cancer cell invasion and metastasis. However, the phosphatase that dephosphorylates Ser(P)(68)-Twist1 and destabilizes Twist1 has not been identified and characterized. In this study, we screened a serine/threonine phosphatase cDNA expression library in HEK293T cells with ectopically coexpressed Twist1. We found that the small C-terminal domain phosphatase 1 (SCP1) specifically dephosphorylates Ser(P)(68)-Twist1 in both cell-free reactions and living cells. SCP1 uses its amino acid residues 43-63 to interact with the N terminus of Twist1. Increased SCP1 expression in cells decreased Ser(P)(68)-Twist1 and total Twist1 proteins, whereas knockdown of SCP1 increased Ser(P)(68)-Twist1 and total Twist1 proteins. Furthermore, the levels of SCP1 are negatively correlated with Twist1 protein levels in several cancer cell lines. SCP1-dephosphorylated Twist1 undergoes fast degradation via the ubiquitin-proteasome pathway. Importantly, an increase in SCP1 expression in breast cancer cells with either endogenous or ectopically expressed Twist1 largely inhibits the Twist1-induced epithelial-to-mesenchymal transition phenotype and the migration and invasion capabilities of these cells. These results indicate that SCP1 is the phosphatase that counterregulates the MAPK-mediated phosphorylation of Ser(68)-Twist1. Thus, an increase in SCP1 expression and activity may be a useful strategy for eliminating the detrimental roles of Twist1 in cancer cells. PMID:26975371

  12. Significance of Heterogeneous Twist2 Expression in Human Breast Cancers

    PubMed Central

    Mao, Yubin; Zhang, Nini; Xu, Jinfei; Ding, Zhijie; Zong, Rongrong; Liu, Zuguo

    2012-01-01

    Background Twist2 (Dermo1) has been shown to mediate the epithelial-mesenchymal transition (EMT) to promote tumor invasion and even metastasis. However, the involvement of EMT in breast cancer progression is highly debated, partially due to clinical observations showing that the majority of human breast carcinoma metastases express E-cadherin and maintain their epithelial morphology. The molecular mechanism by which Twist2 participates in EMT of breast cancer in vivo remains poorly understood. Methods We examined Twist2 expression pattern in human breast carcinomas by western blot and tissue microarray, and analyzed Twist2 cellular localization by confocal microscopy, cell fractionation and other approaches. Results Twist2 expression was significantly increased in breast cancer. Cytoplasmic Twist2 positive cancer cells expressing E-cadherin on the cellular membrane were mainly located at tumor center of primary carcinomas and lymph metastases, while cancer cells with nuclear Twist2 clearly showed loss of E-cadherin and were detected at the invasive front in ductal breast carcinomas. In addition, ectopically stable-expressed Twist2 was found to localize in the cytoplasm of cancer cells. Collectively, these data indicate that upregulation of cytoplasmic Twist2 is correlated with tumor histological type and tumor metastasis in human breast cancers. Conclusion The differential cellular distribution of Twist2 may be associated with tumor progression. The cytoplasmic Twist2 in cancer cells at tumor center of primary carcinomas and lymph metastases contributes to the maintenance of epithelial cancer characteristics expressing E-cadherin in a noninvasive state, while the nuclear Twist2 at the cancer invasion front activates EMT to deprive epithelial property of neoplastic cells, thus facilitating invasion and metastasis. These findings suggest that heterogeneous expression of Twist2 in tumors may have a functional link to tumor progression. PMID:23133563

  13. Formation of chiral branched nanowires by the Eshelby Twist.

    PubMed

    Zhu, Jia; Peng, Hailin; Marshall, A F; Barnett, D M; Nix, W D; Cui, Yi

    2008-08-01

    Manipulating the morphology of inorganic nanostructures, such as their chirality and branching structure, has been actively pursued as a means of controlling their electrical, optical and mechanical properties. Notable examples of chiral inorganic nanostructures include carbon nanotubes, gold multishell nanowires, mesoporous nanowires and helical nanowires. Branched nanostructures have also been studied and been shown to have interesting properties for energy harvesting and nanoelectronics. Combining both chiral and branching motifs into nanostructures might provide new materials properties. Here we show a chiral branched PbSe nanowire structure, which is formed by a vapour-liquid-solid branching from a central nanowire with an axial screw dislocation. The chirality is caused by the elastic strain of the axial screw dislocation, which produces a corresponding Eshelby Twist in the nanowires. In addition to opening up new opportunities for tailoring the properties of nanomaterials, these chiral branched nanowires also provide a direct visualization of the Eshelby Twist. PMID:18685634

  14. Gain-Scheduled Approximations to H-Infinity Controllers for the F/A-18 Active Aeroelastic Wing

    NASA Technical Reports Server (NTRS)

    Lind, Rick

    1999-01-01

    The Active Aeroelastic Wing will demonstrate technologies related to aeroservoelastic effects such as wing twist and load minimization. This paper presents a control design based on H-infinity synthesis that simultaneously considers the multiple objectives associated with handling qualities, actuator limitations, and loads. The controller is realized as a filter and gain set approximation to a state-space H-infinity controller. This approximation allows scheduling of the controller over a flight envelope.

  15. Twisted waveguide accelerating structure.

    SciTech Connect

    Kang, Y. W.

    2000-08-15

    A hollow waveguide with a uniform cross section may be used for accelerating charged particles if the phase velocity of an accelerating mode is equal to or less than the free space speed of light. Regular straight hollow waveguides have phase velocities of propagating electromagnetic waves greater than the free-space speed of light. if the waveguide is twisted, the phase velocities of the waveguide modes become slower. The twisted waveguide structure has been modeled and computer simulated in 3-D electromagnetic solvers to show the slow-wave properties for the accelerating mode.

  16. Twisted Yangians of small rank

    NASA Astrophysics Data System (ADS)

    Guay, Nicolas; Regelskis, Vidas; Wendlandt, Curtis

    2016-04-01

    We study quantized enveloping algebras called twisted Yangians associated with the symmetric pairs of types CI, BDI, and DIII (in Cartan's classification) when the rank is small. We establish isomorphisms between these twisted Yangians and the well known Olshanskii's twisted Yangians of types AI and AII, and also with the Molev-Ragoucy reflection algebras associated with symmetric pairs of type AIII. We also construct isomorphisms with twisted Yangians in Drinfeld's original presentation.

  17. Twisted mass finite volume effects

    SciTech Connect

    Colangelo, Gilberto; Wenger, Urs; Wu, Jackson M. S.

    2010-08-01

    We calculate finite-volume effects on the pion masses and decay constant in twisted mass lattice QCD at finite lattice spacing. We show that the lighter neutral pion in twisted mass lattice QCD gives rise to finite-volume effects that are exponentially enhanced when compared to those arising from the heavier charged pions. We demonstrate that the recent two flavor twisted mass lattice data can be better fitted when twisted mass effects in finite-volume corrections are taken into account.

  18. Craniofacial shape variation in Twist1+/- mutant mice.

    PubMed

    Parsons, Trish E; Weinberg, Seth M; Khaksarfard, Kameron; Howie, R Nicole; Elsalanty, Mohammed; Yu, Jack C; Cray, James J

    2014-05-01

    Craniosynostosis (CS) is a relatively common birth defect resulting from the premature fusion of one or more cranial sutures. Human genetic studies have identified several genes in association with CS. One such gene that has been implicated in both syndromic (Saethre-Chotzen syndrome) and nonsyndromic forms of CS in humans is TWIST1. In this study, a heterozygous Twist1 knock out (Twist1(+/-) ) mouse model was used to study the craniofacial shape changes associated with the partial loss of function. A geometric morphometric approach was used to analyze landmark data derived from microcomputed tomography scans to compare craniofacial shape between 17 Twist1(+/-) mice and 26 of their Twist1(+/+) (wild type) littermate controls at 15 days of age. The results show that despite the purported wide variation in synostotic severity, Twist1(+/-) mice have a consistent pattern of craniofacial dysmorphology affecting all major regions of the skull. Similar to Saethre-Chotzen, the calvarium is acrocephalic and wide with an overall brachycephalic shape. Mutant mice also exhibited a shortened cranial base and a wider and shorted face, consistent with coronal CS associated phenotypes. The results suggest that these differences are at least partially the direct result of the Twist1 haploinsufficiency on the developing craniofacial skeleton. This study provides a quantitative phenotype complement to the developmental and molecular genetic research previously done on Twist1. These results can be used to generate further hypotheses about the effect of Twist1 and premature suture fusion on the entire craniofacial skeleton. PMID:24585549

  19. Self-Portraits with a Twist

    ERIC Educational Resources Information Center

    DeMarco, Frederick

    2010-01-01

    This article describes an art activity on self-portraiture inspired by artist Tim Hawkinson. Hawkinson created a sculpture titled "Emoter" in which his face, moved by motors, twisted and contorted based on random signals from a TV. This art activity incorporates technology into the art room, brings the work of practicing artists alive, and is a…

  20. Structure-Function Studies of the bHLH Phosphorylation Domain of TWIST1 in Prostate Cancer Cells12

    PubMed Central

    Gajula, Rajendra P.; Chettiar, Sivarajan T.; Williams, Russell D.; Nugent, Katriana; Kato, Yoshinori; Wang, Hailun; Malek, Reem; Taparra, Kekoa; Cades, Jessica; Annadanam, Anvesh; Yoon, A-Rum; Fertig, Elana; Firulli, Beth A.; Mazzacurati, Lucia; Burns, Timothy F.; Firulli, Anthony B.; An, Steven S.; Tran, Phuoc T.

    2015-01-01

    The TWIST1 gene has diverse roles in development and pathologic diseases such as cancer. TWIST1 is a dimeric basic helix-loop-helix (bHLH) transcription factor existing as TWIST1-TWIST1 or TWIST1-E12/47. TWIST1 partner choice and DNA binding can be influenced during development by phosphorylation of Thr125 and Ser127 of the Thr-Gln-Ser (TQS) motif within the bHLH of TWIST1. The significance of these TWIST1 phosphorylation sites for metastasis is unknown. We created stable isogenic prostate cancer cell lines overexpressing TWIST1 wild-type, phospho-mutants, and tethered versions. We assessed these isogenic lines using assays that mimic stages of cancer metastasis. In vitro assays suggested the phospho-mimetic Twist1-DQD mutation could confer cellular properties associated with pro-metastatic behavior. The hypo-phosphorylation mimic Twist1-AQA mutation displayed reduced pro-metastatic activity compared to wild-type TWIST1 in vitro, suggesting that phosphorylation of the TWIST1 TQS motif was necessary for pro-metastatic functions. In vivo analysis demonstrates that the Twist1-AQA mutation exhibits reduced capacity to contribute to metastasis, whereas the expression of the Twist1-DQD mutation exhibits proficient metastatic potential. Tethered TWIST1-E12 heterodimers phenocopied the Twist1-DQD mutation for many in vitro assays, suggesting that TWIST1 phosphorylation may result in heterodimerization in prostate cancer cells. Lastly, the dual phosphatidylinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) inhibitor BEZ235 strongly attenuated TWIST1-induced migration that was dependent on the TQS motif. TWIST1 TQS phosphorylation state determines the intensity of TWIST1-induced pro-metastatic ability in prostate cancer cells, which may be partly explained mechanistically by TWIST1 dimeric partner choice. PMID:25622896

  1. A Transformation Called "Twist"

    ERIC Educational Resources Information Center

    Hwang, Daniel

    2010-01-01

    The transformations found in secondary mathematics curriculum are typically limited to stretches and translations (e.g., ACARA, 2010). Advanced students may find the transformation, twist, to be of further interest. As most available resources are written for professional-level readers, this article is intended to be an introduction accessible to…

  2. An H-Infinity Approach to Control Synthesis with Load Minimization for the F/A-18 Active Aeroelastic Wing

    NASA Technical Reports Server (NTRS)

    Lind, Rick

    1999-01-01

    The F/A-18 Active Aeroelastic Wing research aircraft will demonstrate technologies related to aeroservoelastic effects such as wing twist and load minimization. This program presents several challenges for control design that are often not considered for traditional aircraft. This paper presents a control design based on H-infinity synthesis that simultaneously considers the multiple objectives associated with handling qualities, actuator limitations, and loads. A point design is presented to demonstrate a controller and the resulting closed-loop properties.

  3. An H-infinity Approach to Control Synthesis with Load Minimization for the F/A-18 Active Aeroelastic Wing

    NASA Technical Reports Server (NTRS)

    Lind, Rick

    1999-01-01

    The F/A-18 Active Aeroelastic Wing research aircraft will demonstrate technologies related to aeroservoelastic effects such as wing twist and load minimization. This program presents several challenges for control design that are often not considered for traditional aircraft. This paper presents a control design based on H(sub infinity) synthesis that simultaneously considers the multiple objectives associated with handling qualities, actuator limitations, and loads. A point design is presented to demonstrate a controller and the resulting closed-loop properties.

  4. Active control of convection

    SciTech Connect

    Bau, H.H.

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  5. Active weld control

    NASA Technical Reports Server (NTRS)

    Powell, Bradley W.; Burroughs, Ivan A.

    1994-01-01

    Through the two phases of this contract, sensors for welding applications and parameter extraction algorithms have been developed. These sensors form the foundation of a weld control system which can provide action weld control through the monitoring of the weld pool and keyhole in a VPPA welding process. Systems of this type offer the potential of quality enhancement and cost reduction (minimization of rework on faulty welds) for high-integrity welding applications. Sensors for preweld and postweld inspection, weld pool monitoring, keyhole/weld wire entry monitoring, and seam tracking were developed. Algorithms for signal extraction were also developed and analyzed to determine their application to an adaptive weld control system. The following sections discuss findings for each of the three sensors developed under this contract: (1) weld profiling sensor; (2) weld pool sensor; and (3) stereo seam tracker/keyhole imaging sensor. Hardened versions of these sensors were designed and built under this contract. A control system, described later, was developed on a multiprocessing/multitasking operating system for maximum power and flexibility. Documentation for sensor mechanical and electrical design is also included as appendices in this report.

  6. Twisted aspirin crystals.

    PubMed

    Cui, Xiaoyan; Rohl, Andrew L; Shtukenberg, Alexander; Kahr, Bart

    2013-03-01

    Banded spherulites of aspirin have been crystallized from the melt in the presence of salicylic acid either generated from aspirin decomposition or added deliberately (2.6-35.9 mol %). Scanning electron microscopy, X-ray diffraction analysis, and optical polarimetry show that the spherulites are composed of helicoidal crystallites twisted along the <010> growth directions. Mueller matrix imaging reveals radial oscillations in not only linear birefringence, but also circular birefringence, whose origin is explained through slight (∼1.3°) but systematic splaying of individual lamellae in the film. Strain associated with the replacement of aspirin molecules by salicylic acid molecules in the crystal structure is computed to be large enough to work as the driving force for the twisting of crystallites. PMID:23425247

  7. Twisted Split Fermions

    SciTech Connect

    Grossman, Yuval; Harnik, Roni; Perez, Gilad; Schwartz, MatthewD.; Surujon, Ze'ev

    2004-07-30

    The observed flavor structure of the standard model arises naturally in ''split fermion'' models which localize fermions at different places in an extra dimension. It has, until now, been assumed that the bulk masses for such fermions can be chosen to be flavor diagonal simultaneously at every point in the extra dimension, with all the flavor violation coming from the Yukawa couplings to the Higgs. We consider the more natural possibility in which the bulk masses cannot be simultaneously diagonalized, that is, that they are twisted in flavor space. We show that, in general, this does not disturb the natural generation of hierarchies in the flavor parameters. Moreover, it is conceivable that all the flavor mixing and CP-violation in the standard model may come only from twisting, with the five-dimensional Yukawa couplings taken to be universal.

  8. Twisted Split Fermions

    SciTech Connect

    Grossman, Y

    2004-07-24

    The observed flavor structure of the standard model arises naturally in ''split fermion'' models which localize fermions at different places in an extra dimension. It has, until now, been assumed that the bulk masses for such fermions can be chosen to be flavor diagonal simultaneously at every point in the extra dimension, with all the flavor violation coming from the Yukawa couplings to the Higgs. We consider the more natural possibility in which the bulk masses cannot be simultaneously diagonalized, that is, that they are twisted in flavor space. We show that, in general, this does not disturb the natural generation of hierarchies in the flavor parameters. Moreover, it is conceivable that all the flavor mixing and CP-violation in the standard model may come only from twisting, with the five-dimensional Yukawa couplings taken to be universal.

  9. Twisting Graphene into Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Kit, Oleg O.; Tallinen, Tuomas; Mahadevan, L.; Timonen, Jussi; Koskinen, Pekka

    2012-02-01

    Carbon nanotubes are usually described as being rolled up from graphene sheets; this process, however, have never been realized experimentally. We showed that graphene can indeed be transformed into nanotube by twisting [1]. Further, we showed that tube formation can be well-explained within classical theory of elasticity---in fact the very mechanism of tube formation can be observed by twisting a strap from one's backpack (try now!). Furthermore, we showed that nanotube chirality may not only be predicted, but can also be controlled externally. The quantum molecular dynamic simulations at T=300K were achieved thanks to the revised periodic boundary conditions (RPBC) approach [2-3]. The structures similar to simulated have been recently observed experimentally [4]. This novel rote for nanotube formation opens new opportunities in nanomaterial manipulation not restricted to carbon alone. In the presentation, I will describe tube formation, as well as outline the easy and efficient technique for distorted nanostructures simulation, the RPBC approach. [4pt] [1] O. O. Kit et al. arXiv:1108.0048[0pt] [2] P. Koskinen & O. O. Kit PRL 105, 106401 (2010)[0pt] [3] O. O. Kit, L. Pastewka, P. Koskinen PRB 84, 155431 (2011)[0pt] [4] A. Chuvilin et al. Nature Materials 10, 687 (2011)

  10. Active Control of Engine Dynamics

    NASA Astrophysics Data System (ADS)

    2002-11-01

    Active control can alleviate design constraints and improve the response to operational requirements in gas turbines. The Course presented the state-of-the-art including experimental, theoretical knowledge and practical information. Topics treated: stability characteristics; active control approaches; robustness and fundamental limits; combustion systems processes; combustor dynamics; compression system dynamics models; diagnostics and control of compression instabilities; sensor and actuator architectures; R&D needs of future prospects. The course has shown that for combustion systems, as well as in actuator and sensor technologies the active control approach is a viable option even at full scale with potential for aero engines and air breathing missiles.

  11. Twisting of sheet metals

    NASA Astrophysics Data System (ADS)

    Pham, C. H.; Thuillier, S.; Manach, P. Y.

    2013-12-01

    Twisting of metallic sheets is one particular mode of springback that occurs after drawing of elongated parts, i.e. with one dimension much larger than the two others. In this study, a dedicated device for drawing of elongated part with a U-shaped section has been designed on purpose, in order to obtain reproducible data. Very thin metallic sheet, of thickness 0.15 mm, has been used, so that the maximum length of the part is 100 mm. Two different orientations of the part with respect to the tools have been chosen: either aligned with the tools, or purposefully misaligned by 2°. Several samples were drawn for each configuration, leading to the conclusion that almost no twisting occurs in the first case whereas a significant one can be measured for the second one. In a second step, 2D and 3D numerical simulations within the implicit framework for drawing and springback were carried out. A mixed hardening law associated to von Mises yield criterion represents accurately the mechanical behavior of the material. This paper highlights a comparison of numerical predictions with experiments, e.g. the final shape of the part and the twisting parameter.

  12. Twist planet drive

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1996-01-01

    A planetary gear system includes a sun gear coupled to an annular ring gear through a plurality of twist-planet gears, a speeder gear, and a ground structure having an internal ring gear. Each planet gear includes a solid gear having a first half portion in the form of a spur gear which includes vertical gear teeth and a second half portion in the form of a spur gear which includes helical gear teeth that are offset from the vertical gear teeth and which contact helical gear teeth on the speeder gear and helical gear teeth on the outer ring gear. One half of the twist planet gears are preloaded downward, while the other half are preloaded upwards, each one alternating with the other so that each one twists in a motion opposite to its neighbor when rotated until each planet gear seats against the sun gear, the outer ring gear, the speeder gear, and the inner ring gear. The resulting configuration is an improved stiff anti-backlash gear system.

  13. Tamoxifen Inhibits ER-negative Breast Cancer Cell Invasion and Metastasis by Accelerating Twist1 Degradation

    PubMed Central

    Ma, Gang; He, Jianjun; Yu, Yang; Xu, Yixiang; Yu, Xiaobin; Martinez, Jarrod; Lonard, David M.; Xu, Jianming

    2015-01-01

    Twist1 is a transcription factor driving epithelial-mesenchymal transition, invasion and metastasis of breast cancer cells. Mice with germ-line Twist1 knockout are embryonic lethal, while adult mice with inducible Twist1 knockout have no obvious health problems, suggesting that Twist1 is a viable therapeutic target for the inhibition of invasion and metastasis of breast cancer in adult patients. In this study, we expressed a luciferase protein or a Twist1-luciferase fusion protein in HeLa cells as part of a high throughput system to screen 1280 compounds in the Library of Pharmacologically Active Compounds (LOPAC) from Sigma-Aldrich for their effects on Twist1 protein expression. One of the most interesting compounds identified is tamoxifen, a selective estrogen receptor (ER) modulator used to treat ER-positive breast cancer. Tamoxifen treatment significantly accelerated Twist1 degradation in multiple cell lines including HEK293 human kidney cells, 4T1 and 168FARN mouse mammary tumor cells with either ectopically or endogenously expressed Twist1. Tamoxifen-induced Twist1 degradation could be blocked by the MG132 proteasome inhibitor, suggesting that tamoxifen induces Twist1 degradation through the ubiquitination-proteasome pathway. However, tamoxifen-induced Twist1 degradation was independent of Twist1 mRNA expression, estrogen signaling and MAPK-mediated Twist1 phosphorylation in these cells. Importantly, tamoxifen also significantly inhibited invasive behavior in Matrigel and lung metastasis in SCID-bg mice of ER-negative 4T1 mammary tumor cells, which depend on endogenous Twist1 to invade and metastasize. These results indicate that tamoxifen can significantly accelerate Twist1 degradation to suppress cancer cell invasion and metastasis, suggesting that tamoxifen can be used not only to treat ER-positive breast cancers but also to reduce Twist1-mediated invasion and metastasis in ER-negative breast cancers. PMID:25892968

  14. Tamoxifen inhibits ER-negative breast cancer cell invasion and metastasis by accelerating Twist1 degradation.

    PubMed

    Ma, Gang; He, Jianjun; Yu, Yang; Xu, Yixiang; Yu, Xiaobin; Martinez, Jarrod; Lonard, David M; Xu, Jianming

    2015-01-01

    Twist1 is a transcription factor driving epithelial-mesenchymal transition, invasion and metastasis of breast cancer cells. Mice with germ-line Twist1 knockout are embryonic lethal, while adult mice with inducible Twist1 knockout have no obvious health problems, suggesting that Twist1 is a viable therapeutic target for the inhibition of invasion and metastasis of breast cancer in adult patients. In this study, we expressed a luciferase protein or a Twist1-luciferase fusion protein in HeLa cells as part of a high throughput system to screen 1280 compounds in the Library of Pharmacologically Active Compounds (LOPAC) from Sigma-Aldrich for their effects on Twist1 protein expression. One of the most interesting compounds identified is tamoxifen, a selective estrogen receptor (ER) modulator used to treat ER-positive breast cancer. Tamoxifen treatment significantly accelerated Twist1 degradation in multiple cell lines including HEK293 human kidney cells, 4T1 and 168FARN mouse mammary tumor cells with either ectopically or endogenously expressed Twist1. Tamoxifen-induced Twist1 degradation could be blocked by the MG132 proteasome inhibitor, suggesting that tamoxifen induces Twist1 degradation through the ubiquitination-proteasome pathway. However, tamoxifen-induced Twist1 degradation was independent of Twist1 mRNA expression, estrogen signaling and MAPK-mediated Twist1 phosphorylation in these cells. Importantly, tamoxifen also significantly inhibited invasive behavior in Matrigel and lung metastasis in SCID-bg mice of ER-negative 4T1 mammary tumor cells, which depend on endogenous Twist1 to invade and metastasize. These results indicate that tamoxifen can significantly accelerate Twist1 degradation to suppress cancer cell invasion and metastasis, suggesting that tamoxifen can be used not only to treat ER-positive breast cancers but also to reduce Twist1-mediated invasion and metastasis in ER-negative breast cancers. PMID:25892968

  15. Controls Considerations for Turbine Active Clearance Control

    NASA Technical Reports Server (NTRS)

    Melcher, Kevin J.

    2004-01-01

    This presentation discusses active control of turbine tip clearance from a control systems perspective. It is a subset of charts that were presented at the 2003 meeting of the International Society of Air Breathing Engines which was held August 31 through September 5 in Cleveland, Ohio. The associated reference paper is cited at the end of the presentation. The presentation describes active tip clearance control research being conducted by NASA to improve turbine engine systems. The target application for this effort is commercial aircraft engines. However, it is believed that the technologies developed as part of this research will benefit a broad spectrum of current and future turbomachinery. The first part of the presentation discusses the concept of tip clearance, problems associated with it, and the benefits of controlling it. It lays out a framework for implementing tip clearance controls that enables the implementation to progress from purely analytical to hardware-in-the-loop to fully experimental. And it briefly discusses how the technologies developed will be married to the previously described ACC Test Rig for hardware-in-the-loop demonstrations. The final portion of the presentation, describes one of the key technologies in some detail by presenting equations and results for a functional dynamic model of the tip clearance phenomena. As shown, the model exhibits many of the clearance dynamics found in commercial gas turbine engines. However, initial attempts to validate the model identified limitations that are being addressed to make the model more realistic.

  16. Effect of torsional twist on 2nd order non-linear optical activity of anthracene and pyrene tricyanofuran derivatives.

    PubMed

    Planells, Miquel; Pizzotti, Maddalena; Nichol, Gary S; Tessore, Francesca; Robertson, Neil

    2014-11-14

    Tricyanofuran (TCF) derivatives attached to both anthracene and pyrene moieties were synthesised and characterised by optical, electrochemical and computational techniques. Both compounds exhibited similar absorption profile as well as electrochemical behaviour, however the pyrene derivative showed 20-fold higher non-linear optical activity measured by the EFISH technique. This huge difference has been assigned to (i) a lower molar absorption and (ii) a higher torsion angle for the anthracene derivative, confirmed by both experimental X-ray diffraction and DFT calculations. Furthermore, we note that the μβ1.907 value of -1700 × 10(-48) esu recorded for the pyrene derivative in CHCl3/pyridine is remarkable for a NLO chromophore lacking a classical push-pull structure. PMID:25264846

  17. The design of fibre-reinforced composite blades for passive and active wind turbine rotor aerodynamic control

    NASA Astrophysics Data System (ADS)

    Karaolis, Nicos M.

    An alternative method of varying the pitch of wind turbine rotor blades is examined, which relies on the use of fiber reinforced composite materials to design the blades so as to develop elastic coupling between an applied load of a generally twisting and non-twisting nature. With such an approach, twist can be obtained either by using one of the forces experienced by the blade during operation to alter passively the blade pitch, or by internal pressurization to control actively the blade pitch by varying the pressure. The passive control option is considered in detail. First the relevant composite construction geometries that produce the desired coupling effect are identified and then a theoretical model is developed. This is also used to explore the variation in coupling and stiffness properties with the fiber orientation. Various materials are considered including glass, aramid, and carbon fiber epoxy composites. Subsequently, the structural model is confirmed experimentally by a series of tests on composite, foam-cored beams specially designed and manufactured for this purpose. It is then combined with existing aerodynamic theories in order to model the performance of horizontal and vertical axis rotors employing such blades. The effect of passively induced twist on the aerodynamic performance is examined both theoretically and experimentally. Additionally, a simplified dynamic model is developed to obtain a general idea on how built-in elastic coupling may affect the dynamic stability of a horizontal axis rotor system. The active control option is considered in general as an alternative mechanism of inducing twist. The relevant theory is derived and illustrated with examples, and the realistic practicability of this concept is discussed. To validate the theory, a composite cylindrical shell has been designed, manufactured and tested under pressure.

  18. TWIST1 Integrates Endothelial Responses to Flow in Vascular Dysfunction and Atherosclerosis

    PubMed Central

    Mahmoud, Marwa M.; Kim, Hyejeong Rosemary; Xing, Rouyu; Hsiao, Sarah; Mammoto, Akiko; Chen, Jing; Serbanovic-Canic, Jovana; Feng, Shuang; Bowden, Neil P.; Maguire, Richard; Ariaans, Markus; Francis, Sheila E.; Weinberg, Peter D.; van der Heiden, Kim; Jones, Elizabeth A.; Chico, Timothy J.A.; Ridger, Victoria

    2016-01-01

    Rationale: Blood flow–induced shear stress controls endothelial cell (EC) physiology during atherosclerosis via transcriptional mechanisms that are incompletely understood. The mechanosensitive transcription factor TWIST is expressed during embryogenesis, but its role in EC responses to shear stress and focal atherosclerosis is unknown. Objective: To investigate whether TWIST regulates endothelial responses to shear stress during vascular dysfunction and atherosclerosis and compare TWIST function in vascular development and disease. Methods and Results: The expression and function of TWIST1 was studied in EC in both developing vasculature and during the initiation of atherosclerosis. In zebrafish, twist was expressed in early embryonic vasculature where it promoted angiogenesis by inducing EC proliferation and migration. In adult porcine and murine arteries, TWIST1 was expressed preferentially at low shear stress regions as evidenced by quantitative polymerase chain reaction and en face staining. Moreover, studies of experimental murine carotid arteries and cultured EC revealed that TWIST1 was induced by low shear stress via a GATA4-dependent transcriptional mechanism. Gene silencing in cultured EC and EC-specific genetic deletion in mice demonstrated that TWIST1 promoted atherosclerosis by inducing inflammation and enhancing EC proliferation associated with vascular leakiness. Conclusions: TWIST expression promotes developmental angiogenesis by inducing EC proliferation and migration. In addition to its role in development, TWIST is expressed preferentially at low shear stress regions of adult arteries where it promotes atherosclerosis by inducing EC proliferation and inflammation. Thus, pleiotropic functions of TWIST control vascular disease and development. PMID:27245171

  19. The Heterodimeric TWIST1-E12 Complex Drives the Oncogenic Potential of TWIST1 in Human Mammary Epithelial Cells.

    PubMed

    Jacqueroud, Laurent; Bouard, Charlotte; Richard, Geoffrey; Payen, Léa; Devouassoux-Shisheboran, Mojgan; Spicer, Douglas B; Caramel, Julie; Collin, Guillaume; Puisieux, Alain; Tissier, Agnès; Ansieau, Stéphane

    2016-05-01

    The TWIST1 embryonic transcription factor displays biphasic functions during the course of carcinogenesis. It facilitates the escape of cells from oncogene-induced fail-safe programs (senescence, apoptosis) and their consequent neoplastic transformation. Additionally, it promotes the epithelial-to-mesenchymal transition and the initiation of the metastatic spread of cancer cells. Interestingly, cancer cells recurrently remain dependent on TWIST1 for their survival and/or proliferation, making TWIST1 their Achilles' heel. TWIST1 has been reported to form either homodimeric or heterodimeric complexes mainly in association with the E bHLH class I proteins. These complexes display distinct, sometimes even antagonistic, functions during development and unequal prometastatic functions in prostate cancer cells. Using a tethered dimer strategy, we successively assessed the ability of TWIST1 dimers to cooperate with an activated version of RAS in human mammary epithelial cell transformation, to provide mice with the ability to spontaneously develop breast tumors, and lastly to maintain a senescence program at a latent state in several breast cancer cell lines. We demonstrate that the TWIST1-E12 complex, unlike the homodimer, is an oncogenic form of TWIST1 in mammary epithelial cells and that efficient binding of both partners is a prerequisite for its activity. The detection of the heterodimer in human premalignant lesions by a proximity ligation assay, at a stage preceding the initiation of the metastatic cascade, is coherent with such an oncogenic function. TWIST1-E protein heterodimeric complexes may thus constitute the main active forms of TWIST1 with regard to senescence inhibition over the time course of breast tumorigenesis. PMID:27237323

  20. Optical control of antibacterial activity

    NASA Astrophysics Data System (ADS)

    Velema, Willem A.; van der Berg, Jan Pieter; Hansen, Mickel J.; Szymanski, Wiktor; Driessen, Arnold J. M.; Feringa, Ben L.

    2013-11-01

    Bacterial resistance is a major problem in the modern world, stemming in part from the build-up of antibiotics in the environment. Novel molecular approaches that enable an externally triggered increase in antibiotic activity with high spatiotemporal resolution and auto-inactivation are highly desirable. Here we report a responsive, broad-spectrum, antibacterial agent that can be temporally activated with light, whereupon it auto-inactivates on the scale of hours. The use of such a ‘smart’ antibiotic might prevent the build-up of active antimicrobial material in the environment. Reversible optical control over active drug concentration enables us to obtain pharmacodynamic information. Precisely localized control of activity is achieved, allowing the growth of bacteria to be confined to defined patterns, which has potential for the development of treatments that avoid interference with the endogenous microbial population in other parts of the organism.

  1. Demonstration of Active Combustion Control

    NASA Technical Reports Server (NTRS)

    Lovett, Jeffrey A.; Teerlinck, Karen A.; Cohen, Jeffrey M.

    2008-01-01

    The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.

  2. Active Flow Control Activities at NASA Langley

    NASA Technical Reports Server (NTRS)

    Anders, Scott G.; Sellers, William L., III; Washburn, Anthony E.

    2004-01-01

    NASA Langley continues to aggressively investigate the potential advantages of active flow control over more traditional aerodynamic techniques. This paper provides an update to a previous paper and describes both the progress in the various research areas and the significant changes in the NASA research programs. The goals of the topics presented are focused on advancing the state of knowledge and understanding of controllable fundamental mechanisms in fluids as well as to address engineering challenges. An organizational view of current research activities at NASA Langley in active flow control as supported by several projects is presented. On-center research as well as NASA Langley funded contracts and grants are discussed at a relatively high level. The products of this research are to be demonstrated either in bench-top experiments, wind-tunnel investigations, or in flight as part of the fundamental NASA R&D program and then transferred to more applied research programs within NASA, DOD, and U.S. industry.

  3. Fractional active disturbance rejection control.

    PubMed

    Li, Dazi; Ding, Pan; Gao, Zhiqiang

    2016-05-01

    A fractional active disturbance rejection control (FADRC) scheme is proposed to improve the performance of commensurate linear fractional order systems (FOS) and the robust analysis shows that the controller is also applicable to incommensurate linear FOS control. In FADRC, the traditional extended states observer (ESO) is generalized to a fractional order extended states observer (FESO) by using the fractional calculus, and the tracking differentiator plus nonlinear state error feedback are replaced by a fractional proportional-derivative controller. To simplify controller tuning, the linear bandwidth-parameterization method has been adopted. The impacts of the observer bandwidth ωo and controller bandwidth ωc on system performance are then analyzed. Finally, the FADRC stability and frequency-domain characteristics for linear single-input single-output FOS are analyzed. Simulation results by FADRC and ADRC on typical FOS are compared to demonstrate the superiority and effectiveness of the proposed scheme. PMID:26928516

  4. Unique CCT repeats mediate transcription of the TWIST1 gene in mesenchymal cell lines

    SciTech Connect

    Ohkuma, Mizue; Funato, Noriko; Higashihori, Norihisa; Murakami, Masanori; Ohyama, Kimie; Nakamura, Masataka . E-mail: naka.gene@cmn.tmd.ac.jp

    2007-01-26

    TWIST1, a basic helix-loop-helix transcription factor, plays critical roles in embryo development, cancer metastasis and mesenchymal progenitor differentiation. Little is known about transcriptional regulation of TWIST1 expression. Here we identified DNA sequences responsible for TWIST1 expression in mesenchymal lineage cell lines. Reporter assays with TWIST1 promoter mutants defined the -102 to -74 sequences that are essential for TWIST1 expression in human and mouse mesenchymal cell lines. Tandem repeats of CCT, but not putative CREB and NF-{kappa}B sites in the sequences substantially supported activity of the TWIST1 promoter. Electrophoretic mobility shift assay demonstrated that the DNA sequences with the CCT repeats formed complexes with nuclear factors, containing, at least, Sp1 and Sp3. These results suggest critical implication of the CCT repeats in association with Sp1 and Sp3 factors in sustaining expression of the TWIST1 gene in mesenchymal cells.

  5. Development and Testing of Control Laws for the Active Aeroelastic Wing Program

    NASA Technical Reports Server (NTRS)

    Dibley, Ryan P.; Allen, Michael J.; Clarke, Robert; Gera, Joseph; Hodgkinson, John

    2005-01-01

    The Active Aeroelastic Wing research program was a joint program between the U.S. Air Force Research Laboratory and NASA established to investigate the characteristics of an aeroelastic wing and the technique of using wing twist for roll control. The flight test program employed the use of an F/A-18 aircraft modified by reducing the wing torsional stiffness and adding a custom research flight control system. The research flight control system was optimized to maximize roll rate using only wing surfaces to twist the wing while simultaneously maintaining design load limits, stability margins, and handling qualities. NASA Dryden Flight Research Center developed control laws using the software design tool called CONDUIT, which employs a multi-objective function optimization to tune selected control system design parameters. Modifications were made to the Active Aeroelastic Wing implementation in this new software design tool to incorporate the NASA Dryden Flight Research Center nonlinear F/A-18 simulation for time history analysis. This paper describes the design process, including how the control law requirements were incorporated into constraints for the optimization of this specific software design tool. Predicted performance is also compared to results from flight.

  6. Right handed chiral superstructures from achiral molecules: self-assembly with a twist

    NASA Astrophysics Data System (ADS)

    Anuradha; La, Duong Duc; Al Kobaisi, Mohammad; Bhosale, Sheshanath V.

    2015-10-01

    The induction and development of chiral supramolecular structures from hierarchical self-assembly of achiral compounds is closely related to the evolution of life and the chiral amplification found in nature. Here we show that the combination of achiral tetraphenylethene (TPE) an AIE-active luminophore bearing four long alkyl chains via amide linkage allows the entire process of induction and control of supramolecular chirality into well-defined uniform right-handed twisted superstructures via solvent composition and polarity, i.e. solvophobic effect. We showed that the degree of twist and the pitch of the ribbons can be controlled to one-handed helical structure via solvophobic effects. The twisted superstructure assembly was visualised by scanning electron microscope (SEM) and transmission electron microscopy (TEM), furthermore, circular dichroism (CD) confirms used to determine controlled right-handed assembly. This controlled assembly of an AIE-active molecule can be of practical value; for example, as templates for helical crystallisation, catalysis and a chiral mechanochromic luminescent superstructure formation.

  7. Right handed chiral superstructures from achiral molecules: self-assembly with a twist

    PubMed Central

    Anuradha, A; La, Duong Duc; Al Kobaisi, Mohammad; Bhosale, Sheshanath V.

    2015-01-01

    The induction and development of chiral supramolecular structures from hierarchical self-assembly of achiral compounds is closely related to the evolution of life and the chiral amplification found in nature. Here we show that the combination of achiral tetraphenylethene (TPE) an AIE-active luminophore bearing four long alkyl chains via amide linkage allows the entire process of induction and control of supramolecular chirality into well-defined uniform right-handed twisted superstructures via solvent composition and polarity, i.e. solvophobic effect. We showed that the degree of twist and the pitch of the ribbons can be controlled to one-handed helical structure via solvophobic effects. The twisted superstructure assembly was visualised by scanning electron microscope (SEM) and transmission electron microscopy (TEM), furthermore, circular dichroism (CD) confirms used to determine controlled right-handed assembly. This controlled assembly of an AIE-active molecule can be of practical value; for example, as templates for helical crystallisation, catalysis and a chiral mechanochromic luminescent superstructure formation. PMID:26493294

  8. Extended Active Disturbance Rejection Controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2016-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  9. Extended Active Disturbance Rejection Controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2014-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  10. Extended active disturbance rejection controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2012-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  11. Dual control active superconductive devices

    DOEpatents

    Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

    1993-07-20

    A superconducting active device has dual control inputs and is constructed such that the output of the device is effectively a linear mix of the two input signals. The device is formed of a film of superconducting material on a substrate and has two main conduction channels, each of which includes a weak link region. A first control line extends adjacent to the weak link region in the first channel and a second control line extends adjacent to the weak link region in the second channel. The current flowing from the first channel flows through an internal control line which is also adjacent to the weak link region of the second channel. The weak link regions comprise small links of superconductor, separated by voids, through which the current flows in each channel. Current passed through the control lines causes magnetic flux vortices which propagate across the weak link regions and control the resistance of these regions. The output of the device taken across the input to the main channels and the output of the second main channel and the internal control line will constitute essentially a linear mix of the two input signals imposed on the two control lines. The device is especially suited to microwave applications since it has very low input capacitance, and is well suited to being formed of high temperature superconducting materials since all of the structures may be formed coplanar with one another on a substrate.

  12. Active Interior Noise Control Studies

    NASA Technical Reports Server (NTRS)

    Park, J.; Veeramani, S.; Sampath, A.; Balachandran, B.; Wereley, N.

    1996-01-01

    Analytical and experimental investigations into the control of noise in the interior of a three-dimensional enclosure with a flexible boundary are presented. The rigid boundaries are constructed from acrylic material, and in the different cases considered the flexible boundary is constructed from either aluminum or composite material. Noise generated by an external speaker is transmitted into the enclosure through the flexible boundary and active control is realized by using Lead Zirconate Titanate (PZT) piezoelectric actuators bonded to the flexible boundary. Condenser microphones are used for noise measurements inside and outside the enclosure. Minimization schemes for global and local noise control in the presence of a harmonic disturbance are developed and discussed. In the experiments, analog feedforward control is implemented by using the harmonic disturbance as a reference signal.

  13. Adaptive feedback active noise control

    NASA Astrophysics Data System (ADS)

    Kuo, Sen M.; Vijayan, Dipa

    Feedforward active noise control (ANC) systems use a reference sensor that senses a reference input to the controller. This signal is assumed to be unaffected by the secondary source and is a good measure of the undesired noise to be cancelled by the system. The reference sensor may be acoustic (e.g., microphone) or non-acoustic (e.g., tachometer, optical transducer). An obvious problem when using acoustic sensors is that the reference signal may be corrupted by the canceling signal generated by the secondary source. This problem is known as acoustic feedback. One way of avoiding this is by using a feedback active noise control (FANC) system which dispenses with the reference sensor. The FANC technique originally proposed by Olson and May employs a high gain negative feedback amplifier. This system suffered from the drawback that the error microphone had to be placed very close to the loudspeaker. The operation of the system was restricted to low frequency range and suffered from instability due to the possibility of positive feedback. Feedback systems employing adaptive filtering techniques for active noise control were developed. This paper presents the FANC system modeled as an adaptive prediction scheme.

  14. Twist Helicity in Classical Vortices

    NASA Astrophysics Data System (ADS)

    Scheeler, Martin W.; Kedia, Hridesh; Kleckner, Dustin; Irvine, William T. M.

    2015-11-01

    Recent experimental work has demonstrated that a partial measure of fluid Helicity (the sum of linking and writhing of vortex tubes) is conserved even as those vortices undergo topology changing reconnections. Measuring the total Helicity, however, requires additional information about how the vortex lines are locally twisted inside the vortex core. To bridge this gap, we have developed a novel technique for experimentally measuring twist Helicity. Using this method, we are able to measure the production and eventual decay of twist for a variety of vortex evolutions. Remarkably, we observe twist dynamics capable of conserving total Helicity even in the presence of rapidly changing writhe. This work was supported by the NSF MRSEC shared facilities at the University of Chicago (DMR-0820054) and an NSF CAREER award (DMR-1351506). W.T.M.I. further acknowledges support from the A.P. Sloan Foundation and the Packard Foundation.

  15. Twisting of the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Slavin, J. A.; Smith, E. J.; Tsurutani, B. T.

    1986-01-01

    Theory and models indicate that the IMF causes the magnetotail to produce an observable twist, predicting that the torque should bring the north lobe south of the GSM xy plane on one flank of the magnetotail, and the south lobe north of the plane on the other flank. In this paper, ISEE-3 geotail observations are compared with simultaneously made IMP 8 IMF observations supplemented by inferred IMF B(y) polarities to demonstrate the IMF-induced magnetotail twist. The results indicate that twisting is the single most important factor accounting for observations of the north lobe south of the GSM xy plane and the south lobe north of the plane. The value of the observed magnetotail twist about its aberrated axis is about 18 deg.

  16. Novel Active Combustion Control Valve

    NASA Technical Reports Server (NTRS)

    Caspermeyer, Matt

    2014-01-01

    This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

  17. Loops: Twisting and Scaling

    NASA Astrophysics Data System (ADS)

    Walsh, R. W.

    2004-01-01

    Loop-like structures are the fundamental magnetic building blocks of the solar atmosphere. Recent space-based EUV and X-ray satellite observations (from Yohkoh SOHO and TRACE) have challenged the view that these features are simply static gravitationally stratified plasma pipes. Rather it is now surmised that each loop may consist of a bundle of fine plasma threads that are twisted around one another and can brighten independently. This invited review will outline the latest developments in ""untangling"" the topology of these features through three dimensional magnetohydrodynamic modelling and how their properties are being deduced through spectroscopic observations coupled to theoretical scaling laws. In particular recent interest has centred on how the observed thermal profile along loops can be employed as a tool to diagnose any localised energy input to the structure and hence constrain the presence of a particular coronal heating mechanism. The dynamic nature of loops will be highlighted and the implications of superior resolution plasma thread observations (whether spatial temporal or spectral) from future space missions (SolarB STEREO SDO and Solar Orbiter) will be discussed.

  18. Twisted and tubular silica structures by anionic surfactant fibers encapsulation.

    PubMed

    Chekini, Mahshid; Guénée, Laure; Marchionni, Valentina; Sharma, Manish; Bürgi, Thomas

    2016-09-01

    Organic molecules imprinting can be used for introducing specific properties and functionalities such as chirality to mesoporous materials. Particularly organic self-assemblies can work as a scaffold for templating inorganic materials such as silica. During recent years chiral imprinting of anionic surfactant for fabrication of twisted rod-like silica structures assisted by co-structuring directing agent were thoroughly investigated. The organic self-assemblies of anionic surfactants can also be used for introducing other shapes in rod-like silica structures. Here we report the formation of amphiphilic N-miristoyl-l-alanine self-assemblies in aqueous solution upon stirring and at presence of l-arginine. These anionic surfactant self-assemblies form fibers that grow by increasing the stirring duration. The fibers were studied using transmission electron microscopy, infra-red spectroscopy and vibrational circular dichroism. Addition of silica precursor 1,2-bis(triethoxysilyl)ethylene and co-structuring directing agent N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride at different stages of fibers' growth leads to formation of different silica structures. By controlling stirring duration, we obtained twisted tubular silica structures as a result of fibers encapsulation. We decorated these structures with gold nanoparticles by different methods and measured their optical activity. PMID:27267039

  19. Aeroelastic behavior of twist-coupled HAWT blades

    SciTech Connect

    Lobitz, D.W.; Veers, P.S.

    1998-12-31

    As the technology for horizontal axis wind turbines (HAWT) development matures, more novel techniques are required for the capture of additional amounts of energy, alleviation of loads and control of the rotor. One such technique employs the use of an adaptive blade that could sense the wind velocity or rotational speed in some fashion and accordingly modify its aerodynamic configuration to meet a desired objective. This could be achieved in either an active or passive manner, although the passive approach is much more attractive due to its simplicity and economy. As an example, a blade design might employ coupling between bending and/or extension, and twisting so that, as it bends and extends due to the action of the aerodynamic and inertial loads, it also twists modifying the aerodynamic performance in some way. These performance modifications also have associated aeroelastic effects, including effects on aeroelastic instability. To address the scope and magnitude of these effects a tool has been developed for investigating classical flutter and divergence of HAWT blades. As a starting point, an adaptive version of the uniform Combined Experiment Blade will be investigated. Flutter and divergence airspeeds will be reported as a function of the strength of the coupling and also be compared to those of generic blade counterparts.

  20. Twist-induced Magnetosphere Reconfiguration for Intermittent Pulsars

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Yu, Cong; Tong, Hao

    2016-08-01

    We propose that the magnetosphere reconfiguration induced by magnetic twists in the closed field line region can account for the mode switching of intermittent pulsars. We carefully investigate the properties of axisymmetric force-free pulsar magnetospheres with magnetic twists in closed field line regions around the polar caps. The magnetosphere with twisted closed lines leads to enhanced spin-down rates. The enhancement in spin-down rate depends on the size of the region with twisted closed lines. Typically, it is increased by a factor of ∼2, which is consistent with the intermittent pulsars’ spin-down behavior during the “off” and “on” states. We find that there is a threshold of maximal twist angle {{Δ }}{φ }{{thres}}∼ 1. The magnetosphere is stable only if the closed line twist angle is less than {{Δ }}{φ }{{thres}}. Beyond this value, the magnetosphere becomes unstable and gets untwisted. The spin-down rate would reduce to its off-state value. The quasi-periodicity in spin-down rate change can be explained by long-term activities in the star’s crust and the untwisting induced by MHD instability. The estimated duration of on-state is about 1 week, consistent with observations. Due to the MHD instability, there exists an upper limit for the spin-down ratio (f∼ 3) between the on-state and the off-state, if the Y-point remains at the light cylinder.

  1. Twist-induced Magnetosphere Reconfiguration for Intermittent Pulsars

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Yu, Cong; Tong, Hao

    2016-08-01

    We propose that the magnetosphere reconfiguration induced by magnetic twists in the closed field line region can account for the mode switching of intermittent pulsars. We carefully investigate the properties of axisymmetric force-free pulsar magnetospheres with magnetic twists in closed field line regions around the polar caps. The magnetosphere with twisted closed lines leads to enhanced spin-down rates. The enhancement in spin-down rate depends on the size of the region with twisted closed lines. Typically, it is increased by a factor of ˜2, which is consistent with the intermittent pulsars’ spin-down behavior during the “off” and “on” states. We find that there is a threshold of maximal twist angle {{Δ }}{φ }{{thres}}˜ 1. The magnetosphere is stable only if the closed line twist angle is less than {{Δ }}{φ }{{thres}}. Beyond this value, the magnetosphere becomes unstable and gets untwisted. The spin-down rate would reduce to its off-state value. The quasi-periodicity in spin-down rate change can be explained by long-term activities in the star’s crust and the untwisting induced by MHD instability. The estimated duration of on-state is about 1 week, consistent with observations. Due to the MHD instability, there exists an upper limit for the spin-down ratio (f˜ 3) between the on-state and the off-state, if the Y-point remains at the light cylinder.

  2. Artery Remodeling Under Axial Twist in Three Days Organ Culture.

    PubMed

    Wang, Guo-Liang; Xiao, Yangming; Voorhees, Andrew; Qi, Ying-Xin; Jiang, Zong-Lai; Han, Hai-Chao

    2015-08-01

    Arteries often endure axial twist due to body movement and surgical procedures, but how arteries remodel under axial twist remains unclear. The objective of this study was to investigate early stage arterial wall remodeling under axial twist. Porcine carotid arteries were twisted axially and maintained for three days in ex vivo organ culture systems while the pressure and flow remained the same as untwisted controls. Cell proliferation, internal elastic lamina (IEL) fenestrae shape and size, endothelial cell (EC) morphology and orientation, as well as the expression of matrix metalloproteinases (MMPs), MMP-2 and MMP-9, and tissue inhibitor of metalloproteinase-2 (TIMP-2) were quantified using immunohistochemistry staining and immunoblotting. Our results demonstrated that cell proliferation in both the intima and media were significantly higher in the twisted arteries compared to the controls. The cell proliferation in the intima increased from 1.33 ± 0.21% to 7.63 ± 1.89%, and in the media from 1.93 ± 0.84% to 8.27 ± 2.92% (p < 0.05). IEL fenestrae total area decreased from 26.07 ± 2.13% to 14.74 ± 0.61% and average size decreased from 169.03 ± 18.85 μm(2) to 80.14 ± 1.96 μm(2) (p < 0.01), but aspect ratio increased in the twist group from 2.39 ± 0.15 to 2.83 ± 0.29 (p < 0.05). MMP-2 expression significantly increased (p < 0.05) while MMP-9 and TIMP-2 showed no significant difference in the twist group. The ECs in the twisted arteries were significantly elongated compared to the controls after three days. The angle between the major axis of the ECs and blood flow direction under twist was 7.46 ± 2.44 degrees after 3 days organ culture, a decrease from the initial 15.58 ± 1.29 degrees. These results demonstrate that axial twist can stimulate artery remodeling. These findings complement our understanding of arterial wall remodeling under mechanical stress resulting from pressure and flow variations. PMID:25503524

  3. Neuronal activity controls transsynaptic geometry.

    PubMed

    Glebov, Oleg O; Cox, Susan; Humphreys, Lawrence; Burrone, Juan

    2016-01-01

    The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792

  4. Neuronal activity controls transsynaptic geometry

    PubMed Central

    Glebov, Oleg O.; Cox, Susan; Humphreys, Lawrence; Burrone, Juan

    2016-01-01

    The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792

  5. Twist-1, a novel regulator of hematopoietic stem cell self-renewal and myeloid lineage development.

    PubMed

    Dong, Cheng-Ya; Liu, Xiao-Yan; Wang, Nan; Wang, Li-Na; Yang, Bin-Xia; Ren, Qian; Liang, Hao-Yue; Ma, Xiao-Tong

    2014-12-01

    Transcription factor Twist-1 plays essential roles in specification and differentiation of mesoderm-derived tissues. Growing evidences now link Twist-1 to the acquisition of stem-cell-like properties. However, the role of Twist-1 in hematopoietic stem cell (HSC) remains largely uncharacterized. We report that Twist-1 is more highly expressed in murine HSC and its expression declines with differentiation. To investigate Twist-1 gene function, retroviral-mediated overexpression or removal experiments are performed. Competitive repopulation studies demonstrate that enforced expression of Twist-1 in HSC-enriched Lin(-) c-Kit(+) Sca-1(+) (LKS) cells results in an increase in the size of the G(0) population, and in their reconstitution ability after the first and a second transplantation. Conversely, removal of Twist-1 in LKS cells impairs their ability to repopulate. In addition, increased Twist-1 expression causes a shift toward production of myeloid cells. Twist-1 transduction in LKS cells activates myeloid lineage-determining factors PU.1 and GATA-1 and downregulates lymphoid factor GATA-3 in vitro, suggesting that Twist-1-mediated myeloid skewing occurs in hematopoietic stem and progenitor cells (HSPCs). These findings indicate that Twist-1 is not only involved in the maintenance of HSC dormancy and self-renewal capacity but also implicated in the myeloid lineage fate choice of HSPCs. Exploration of the underlying mechanisms reveals that Runx1/c-Mpl/Tie2 regulatory pathway could possibly account for the observed effects caused by Twist-1 overexpression. Our study provides the first evidence supporting a role for Twist-1 in hematopoiesis. PMID:25100001

  6. To twist or poke? A method for identifying usability issues with the rotary controller and touch screen for control of in-vehicle information systems.

    PubMed

    Harvey, Catherine; Stanton, Neville A; Pickering, Carl A; McDonald, Mike; Zheng, Pengjun

    2011-07-01

    In-vehicle information systems (IVIS) can be controlled by the user via direct or indirect input devices. In order to develop the next generation of usable IVIS, designers need to be able to evaluate and understand the usability issues associated with these two input types. The aim of this study was to investigate the effectiveness of a set of empirical usability evaluation methods for identifying important usability issues and distinguishing between the IVIS input devices. A number of usability issues were identified and their causal factors have been explored. These were related to the input type, the structure of the menu/tasks and hardware issues. In particular, the translation between inputs and on-screen actions and a lack of visual feedback for menu navigation resulted in lower levels of usability for the indirect device. This information will be useful in informing the design of new IVIS, with improved usability. STATEMENT OF RELEVANCE: This paper examines the use of empirical methods for distinguishing between direct and indirect IVIS input devices and identifying usability issues. Results have shown that the characteristics of indirect input devices produce more serious usability issues, compared with direct devices and can have a negative effect on the driver-vehicle interaction. PMID:21770749

  7. DNA Methylation in the Exon 1 Region and Complex Regulation of Twist1 Expression in Gastric Cancer Cells

    PubMed Central

    Sakamoto, Ayuna; Akiyama, Yoshimitsu; Shimada, Shu; Zhu, Wei-Guo; Yuasa, Yasuhito; Tanaka, Shinji

    2015-01-01

    Twist1 overexpression is frequently observed in various cancers including gastric cancer (GC). Although DNA methylation of the Twist1 gene has been reported in cancer cells, the mechanisms underlying transcriptional activation remain uncertain. In this study, we first examined epigenetic alterations of the Twist1 using Twist1 transcription-positive and -negative cell lines that are derived from our established diffuse-type GC mouse model. Treatment with a DNA demethylation agent 5-aza-dC re-activated Twist1 expression in Twist1 expression-negative GC cells. According to methylation-specific PCR and bisulfite sequencing analysis, methylation at the CpG-rich region within Twist1 coding exon 1, rather than its promoter region, was tightly linked to transcriptional silencing of the Twist1 expression in mouse GC cells. Chromatin immunoprecipitation assays revealed that active histone mark H3K4me3 was enriched in Twist1 expression-positive cells, and inactive histone mark H3K9me3 was enriched in Twist1 expression-negative cells. The expression levels of Suv39h1 and Suv39h2, histone methyltransferases for H3K9me3, were inversely correlated with Twist1 expression, and knockdown of Suv39h1 or Suv39h2 induced Twist1 expression. Moreover, Sp1 transcription factor bound to the exon 1 CpG-rich region in Twist1 expression-positive cell lines, and Twist1 expression was diminished by mithramycin, which that interferes with Sp1 binding to CpG-rich regulatory sequences. Our studies suggested that the Twist1 transcription in GC cells might be regulated through potential cooperation of DNA methylation, histone modification in complex with Sp1 binding to CpG-rich regions within the exon 1 region. PMID:26695186

  8. Evaluation of innovative concepts for semi-active and active rotorcraft control

    NASA Astrophysics Data System (ADS)

    Van Weddingen, Yannick

    2011-12-01

    Lead-lag dampers are present in most rotor systems to provide the desired level of damping for all flight conditions. These dampers are critical components of the rotor system, and the performance of semi-active Coulomb friction-based lead-lag dampers is examined for the UH-60 aircraft. The concept of adaptive damping, or "damping on demand," is discussed for both ground resonance and forward flight. The concept of selective damping is also assessed, and shown to face many challenges. In rotorcraft flight dynamics, optimized warping twist change is a potentially enabling technology to improve overall rotorcraft performance. Research efforts in recent years have led to the application of active materials for rotorcraft blade actuation. An innovative concept is proposed wherein the typically closed section blade is cut open to create a torsionally compliant structure that acts as its own amplification device; deformation of the blade is dynamically controlled by out-of-plane warping. Full-blade warping is shown to have the potential for great design flexibility. Recent advances in rotorcraft blade design have also focused on variable-camber airfoils, particularly concepts involving "truss-core" configurations. One promising concept is the use of hexagonal chiral lattice structures in continuously deformable helicopter blades. The static behavior of passive and active chiral networks using piezoelectric actuation strategies is investigated, including under typical aerodynamic load levels. The analysis is then extended to the dynamic response of active chiral networks in unsteady aerodynamic environments.

  9. Performance of twist-coupled blades on variable speed rotors

    SciTech Connect

    Lobitz, D.W.; Veers, P.S.; Laino, D.J.

    1999-12-07

    The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.

  10. Selected advanced aerodynamics and active controls technology concepts development on a derivative B-747

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The feasibility of applying wing tip extensions, winglets, and active control wing load alleviation to the Boeing 747 is investigated. Winglet aerodynamic design methods and high speed wind tunnel test results of winglets and of symmetrically deflected ailerons are presented. Structural resizing analyses to determine weight and aeroelastic twist increments for all the concepts and flutter model test results for the wing with winglets are included. Control law development, system mechanization/reliability studies, and aileron balance tab trade studies for active wing load alleviation systems are discussed. Results are presented in the form of incremental effects on L/D, structural weight, block fuel savings, stability and control, airplane price, and airline operating economics.

  11. Berry phase transition in twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.

    2016-09-01

    The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.

  12. Active control technology and the use of multiple control surfaces

    NASA Technical Reports Server (NTRS)

    Hart, J. E.

    1976-01-01

    Needed criteria for active control technology applications in commercial transports are lacking. Criteria for redundancy requirements, believed to be consistent with certification philosophy, are postulated to afford a discussion of the relative value of multiple control surfaces. The control power and frequency bandpass requirements of various active control technology applications are shown to be such that multiple control surfaces offer advantages in minimizing the hydraulic or auxiliary power for the control surface actuators.

  13. Active Spacecraft Potential Control Investigation

    NASA Astrophysics Data System (ADS)

    Torkar, K.; Nakamura, R.; Tajmar, M.; Scharlemann, C.; Jeszenszky, H.; Laky, G.; Fremuth, G.; Escoubet, C. P.; Svenes, K.

    2016-03-01

    In tenuous plasma the floating potential of sunlit spacecraft reaches tens of volts, positive. The corresponding field disturbs measurements of the ambient plasma by electron and ion sensors and can reduce micro-channel plate lifetime in electron detectors owing to large fluxes of attracted photoelectrons. Also the accuracy of electric field measurements may suffer from a high spacecraft potential. The Active Spacecraft Potential Control (ASPOC) neutralizes the spacecraft potential by releasing positive charge produced by indium ion emitters. The method has been successfully applied on other spacecraft such as Cluster and Double Star. Two ASPOC units are present on each spacecraft. Each unit contains four ion emitters, whereby one emitter per instrument is operated at a time. ASPOC for the Magnetospheric Multiscale (MMS) mission includes new developments in the design of the emitters and the electronics. New features include the use of capillaries instead of needles, new materials for the emitters and their internal thermal insulators, an extended voltage and current range of the electronics, both for ion emission and heating purposes, and a more capable control software. This enables lower spacecraft potentials, higher reliability, and a more uniform potential structure in the spacecraft's sheath compared to previous missions. Results from on-ground testing demonstrate compliance with requirements. Model calculations confirm the findings from previous applications that the plasma measurements will not be affected by the beam's space charge. Finally, the various operating modes to adapt to changing boundary conditions are described along with the main data products.

  14. Extension-twist coupling optimization in composite rotor blades

    NASA Astrophysics Data System (ADS)

    Ozbay, Serkan

    2005-07-01

    For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different. Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass. A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept

  15. Normal and disease-related biological functions of Twist1 and underlying molecular mechanisms

    PubMed Central

    Qin, Qian; Xu, Young; He, Tao; Qin, Chunlin; Xu, Jianming

    2012-01-01

    This article reviews the molecular structure, expression pattern, physiological function, pathological roles and molecular mechanisms of Twist1 in development, genetic disease and cancer. Twist1 is a basic helix-loop-helix domain-containing transcription factor. It forms homo- or hetero-dimers in order to bind the Nde1 E-box element and activate or repress its target genes. During development, Twist1 is essential for mesoderm specification and differentiation. Heterozygous loss-of-function mutations of the human Twist1 gene cause several diseases including the Saethre-Chotzen syndrome. The Twist1-null mouse embryos die with unclosed cranial neural tubes and defective head mesenchyme, somites and limb buds. Twist1 is expressed in breast, liver, prostate, gastric and other types of cancers, and its expression is usually associated with invasive and metastatic cancer phenotypes. In cancer cells, Twist1 is upregulated by multiple factors including SRC-1, STAT3, MSX2, HIF-1α, integrin-linked kinase and NF-κB. Twist1 significantly enhances epithelial-mesenchymal transition (EMT) and cancer cell migration and invasion, hence promoting cancer metastasis. Twist1 promotes EMT in part by directly repressing E-cadherin expression by recruiting the nucleosome remodeling and deacetylase complex for gene repression and by upregulating Bmi1, AKT2, YB-1, etc. Emerging evidence also suggests that Twist1 plays a role in expansion and chemotherapeutic resistance of cancer stem cells. Further understanding of the mechanisms by which Twist1 promotes metastasis and identification of Twist1 functional modulators may hold promise for developing new strategies to inhibit EMT and cancer metastasis. PMID:21876555

  16. Notch inhibits chondrogenic differentiation of mesenchymal progenitor cells by targeting Twist1.

    PubMed

    Tian, Ye; Xu, Ying; Fu, Qin; Chang, Martin; Wang, Yongjun; Shang, Xifu; Wan, Chao; Marymont, John V; Dong, Yufeng

    2015-03-01

    While Notch signaling plays a critical role in the regulation of cartilage formation, its downstream targets are unknown. To address this we performed gain and losses of function experiments and demonstrate that Notch inhibition of chondrogenesis acts via up-regulation of the transcription factor Twist1. Upon Notch activation, murine limb bud mesenchymal progenitor cells in micromass culture displayed an inhibition of chondrogenesis. Twist1 was found to be exclusively expressed in mesenchymal progenitor cells at the onset stage of chondrogenesis during Notch activation. Inhibition of Notch signaling in these cells significantly reduced protein expression of Twist1. Furthermore, the inhibition effect of NICD1 on MPC chondrogenesis was markedly reduced by knocking down of Twist1. Constitutively active Notch signaling significantly enhanced Twist1 promoter activity; whereas mutation studies indicated that a putative NICD/RBPjK binding element in the promoter region is required for the Notch-responsiveness of the Twist1 promoter. Finally, chromatin immunoprecipitation assays further confirmed that the Notch intracellular domain influences Twist1 by directly binding to the Twist1 promoter. These data provide a novel insight into understanding the molecular mechanisms behind Notch inhibition of the onset of chondrogenesis. PMID:25596548

  17. Suppression of fibrogenic signaling in hepatic stellate cells by Twist1-dependent microRNA-214 expression: Role of exosomes in horizontal transfer of Twist1.

    PubMed

    Chen, Li; Chen, Ruju; Kemper, Sherri; Charrier, Alyssa; Brigstock, David R

    2015-09-15

    A hallmark of liver fibrosis is the activation of hepatic stellate cells (HSC), which results in their production of fibrotic molecules, a process that is largely regulated by connective tissue growth factor (CCN2). CCN2 is increasingly expressed during HSC activation because of diminished expression of microRNA-214 (miR-214), a product of dynamin 3 opposite strand (DNM3os) that directly suppresses CCN2 mRNA. We show that an E-box in the miR-214 promoter binds the basic helix-loop-helix transcription factor, Twist1, which drives miR-214 expression and results in CCN2 suppression. Twist1 expression was suppressed in HSC of fibrotic livers or in cultured HSC undergoing activation in vitro or after treatment with ethanol. Furthermore, Twist1 decreasingly interacted with DNM3os as HSC underwent activation in vitro. Nanovesicular exosomes secreted by quiescent but not activated HSC contained high levels of Twist1, thus reflecting the suppression of cellular Twist1 during HSC activation. Exosomal Twist1 was intercellularly shuttled between HSC and stimulated expression of miR-214 in the recipient cells, causing expression of CCN2 and its downstream effectors to be suppressed. Additionally, the miR-214 E-box in HSC was also regulated by hepatocyte-derived exosomes, showing that functional transfer of exosomal Twist1 occurs between different cell types. Finally, the levels of Twist1, miR-214, or CCN2 in circulating exosomes from fibrotic mice reflected fibrosis-induced changes in the liver itself, highlighting the potential utility of these and other constituents in serum exosomes as novel circulating biomarkers for liver fibrosis. These findings reveal a unique function for cellular or exosomal Twist1 in CCN2-dependent fibrogenesis. PMID:26229009

  18. Interfacial Atomic Structure of Twisted Few-Layer Graphene

    PubMed Central

    Ishikawa, Ryo; Lugg, Nathan R.; Inoue, Kazutoshi; Sawada, Hidetaka; Taniguchi, Takashi; Shibata, Naoya; Ikuhara, Yuichi

    2016-01-01

    A twist in bi- or few-layer graphene breaks the local symmetry, introducing a number of intriguing physical properties such as opening new bandgaps. Therefore, determining the twisted atomic structure is critical to understanding and controlling the functional properties of graphene. Combining low-angle annular dark-field electron microscopy with image simulations, we directly determine the atomic structure of twisted few-layer graphene in terms of a moiré superstructure which is parameterized by a single twist angle and lattice constant. This method is shown to be a powerful tool for accurately determining the atomic structure of two-dimensional materials such as graphene, even in the presence of experimental errors. Using coincidence-site-lattice and displacement-shift-complete theories, we show that the in-plane translation state between layers is not a significant structure parameter, explaining why the present method is adequate not only for bilayer graphene but also a few-layered twisted graphene. PMID:26888259

  19. Twinning and twisting of tri- and bilayer graphene.

    PubMed

    Brown, Lola; Hovden, Robert; Huang, Pinshane; Wojcik, Michal; Muller, David A; Park, Jiwoong

    2012-03-14

    The electronic, optical, and mechanical properties of bilayer and trilayer graphene vary with their structure, including the stacking order and relative twist, providing novel ways to realize useful characteristics not available to single layer graphene. However, developing controlled growth of bilayer and trilayer graphene requires efficient large-scale characterization of multilayer graphene structures. Here, we use dark-field transmission electron microscopy for rapid and accurate determination of key structural parameters (twist angle, stacking order, and interlayer spacing) of few-layer CVD graphene. We image the long-range atomic registry for oriented bilayer and trilayer graphene, find that it conforms exclusively to either Bernal or rhombohedral stacking, and determine their relative abundances. In contrast, our data on twisted multilayers suggest the absence of such long-range atomic registry. The atomic registry and its absence are consistent with the two different strain-induced deformations we observe; by tilting the samples to break mirror symmetry, we find a high density of twinned domains in oriented multilayer graphene, where multiple domains of two different stacking configurations coexist, connected by discrete twin boundaries. In contrast, individual layers in twisted regions continuously stretch and shear independently, forming elaborate Moiré patterns. These results, and the twist angle distribution in our CVD graphene, can be understood in terms of an angle-dependent interlayer potential model. PMID:22329410

  20. Interfacial Atomic Structure of Twisted Few-Layer Graphene.

    PubMed

    Ishikawa, Ryo; Lugg, Nathan R; Inoue, Kazutoshi; Sawada, Hidetaka; Taniguchi, Takashi; Shibata, Naoya; Ikuhara, Yuichi

    2016-01-01

    A twist in bi- or few-layer graphene breaks the local symmetry, introducing a number of intriguing physical properties such as opening new bandgaps. Therefore, determining the twisted atomic structure is critical to understanding and controlling the functional properties of graphene. Combining low-angle annular dark-field electron microscopy with image simulations, we directly determine the atomic structure of twisted few-layer graphene in terms of a moiré superstructure which is parameterized by a single twist angle and lattice constant. This method is shown to be a powerful tool for accurately determining the atomic structure of two-dimensional materials such as graphene, even in the presence of experimental errors. Using coincidence-site-lattice and displacement-shift-complete theories, we show that the in-plane translation state between layers is not a significant structure parameter, explaining why the present method is adequate not only for bilayer graphene but also a few-layered twisted graphene. PMID:26888259

  1. "Twisted Beam" SEE Observations of Ionospheric Heating from HAARP

    NASA Astrophysics Data System (ADS)

    Briczinski, S. J.; Bernhardt, P. A.; Siefring, C. L.; Han, S.-M.; Pedersen, T. R.; Scales, W. A.

    2015-10-01

    Nonlinear interactions of high power HF radio waves in the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska is the world's largest heating facility, yielding effective radiated powers in the gigawatt range. New results are present from HAARP experiments using a "twisted beam" excitation mode. Analysis of twisted beam heating shows that the SEE results obtained are identical to more traditional patterns. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional "solid spot" region from a pencil beam. The ring heating pattern may be more conducive to the creation of stable artificial airglow layers because of the horizontal structure of the ring. The results of these runs include artificial layer creation and evolution as pertaining to the twisted beam pattern. The SEE measurements aid the interpretation of the twisted beam interactions in the ionosphere.

  2. Observation of Low Energy Raman Modes in Twisted Bilayer Graphene

    NASA Astrophysics Data System (ADS)

    He, Rui; Chung, Ting-Fung; Delaney, Conor; Keiser, Courtney; Jauregui, Luis A.; Shand, Paul M.; Chancey, C. C.; Wang, Yanan; Bao, Jiming; Chen, Yong P.

    2013-08-01

    Two new Raman modes below 100 cm^-1 are observed in twisted bilayer graphene grown by chemical vapor deposition. The two modes are observed in a small range of twisting angle at which the intensity of the G Raman peak is strongly enhanced, indicating that these low energy modes and the G Raman mode share the same resonance enhancement mechanism, as a function of twisting angle. The 94 cm^-1 mode (measured with a 532 nm laser excitation) is assigned to the fundamental layer breathing vibration (ZO (prime) mode) mediated by the twisted bilayer graphene lattice, which lacks long-range translational symmetry. The dependence of this modes frequency and linewidth on the rotational angle can be explained by the double resonance Raman process which is different from the previously-identified Raman processes activated by twisted bilayer graphene superlattice. The dependence also reveals the strong impact of electronic-band overlaps of the two graphene layers. Another new mode at 52 cm^-1, not observed previously in the bilayer graphene system, is tentatively attributed to a torsion mode in which the bottom and top graphene layers rotate out-of-phase in the plane.

  3. Active thermal control system evolution

    NASA Technical Reports Server (NTRS)

    Petete, Patricia A.; Ames, Brian E.

    1991-01-01

    The 'restructured' baseline of the Space Station Freedom (SSF) has eliminated many of the growth options for the Active Thermal Control System (ATCS). Modular addition of baseline technology to increase heat rejection will be extremely difficult. The system design and the available real estate no longer accommodate this type of growth. As the station matures during its thirty years of operation, a demand of up to 165 kW of heat rejection can be expected. The baseline configuration will be able to provide 82.5 kW at Eight Manned Crew Capability (EMCC). The growth paths necessary to reach 165 kW have been identified. Doubling the heat rejection capability of SSF will require either the modification of existing radiator wings or the attachment of growth structure to the baseline truss for growth radiator wing placement. Radiator performance can be improved by enlarging the surface area or by boosting the operating temperature with a heat pump. The optimal solution will require both modifications. The addition of growth structure would permit the addition of a parallel ATCS using baseline technology. This growth system would simplify integration. The feasibility of incorporating these growth options to improve the heat rejection capacity of SSF is under evaluation.

  4. Active control of combustion instability

    SciTech Connect

    Lang, W.; Poinsot, T.; Candel, S.

    1987-12-01

    The principle of 'antisound' is used to construct a method for the suppression of combustion instabilities. This active instability control (AIC) method uses external acoustic excitation by a loudspeaker to suppress the oscillations of a flame. The excitation signal is provided by a microphone located upstream of the flame. This signal is filtered, processed, amplified, and sent to the loudspeaker. The AIC method is validated on a laboratory combustor. It allows the suppression of all unstable modes of the burner for any operating ratio. The influence of the microphone and loudspeaker locations on the performance of the AIC system is described. For a given configuration, domains of stability, i.e., domains where the AIC system parameters provide suppression of the oscillation, are investigated. Measurements of the electric input of the loudspeaker show that the energy consumption of the AIC system is almost negligible and suggest that this method could be used for industrial combustor stabilization. Finally, a simple model describing the effects of the AIC system is developed and its results compared to the experiment.

  5. The myogenic repressor gene Holes in muscles is a direct transcriptional target of Twist and Tinman in the Drosophila embryonic mesoderm

    PubMed Central

    Elwell, Jennifer A.; Lovato, TyAnna L.; Adams, Melanie M.; Baca, Erica M.; Lee, Thai; Cripps, Richard M.

    2015-01-01

    Understanding the regulatory circuitry controlling myogenesis is critical to understanding developmental mechanisms and developmentally-derived diseases. We analyzed the transcriptional regulation of a Drosophila myogenic repressor gene, Holes in muscles (Him). Previously, Him was shown to inhibit Myocyte enhancer factor-2 (MEF2) activity, and is expressed in myoblasts but not differentiating myotubes. We demonstrate that different phases of Him embryonic expression arise through the actions of different enhancers, and we characterize the enhancer required for its early mesoderm expression. This Him early mesoderm enhancer contains two conserved binding sites for the basic helix-loop-helix regulator Twist, and one binding site for the NK homeodomain protein Tinman. The sites for both proteins are required for enhancer activity in early embryos. Twist and Tinman activate the enhancer in tissue culture assays, and ectopic expression of either factor is sufficient to direct ectopic expression of a Him-lacZ reporter, or of the endogenous Him gene. Moreover, sustained expression of twist expression in the mesoderm up-regulates mesodermal Him expression in late embryos. Our findings provide a model to define mechanistically how Twist can both promotes myogenesis through direct activation of Mef2, and can place a brake on myogenesis, through direct activation of Him. PMID:25704510

  6. Electrically Induced Twist in Smectic Liquid-Crystalline Elastomers.

    PubMed

    Spillmann, Christopher M; Naciri, Jawad; Ratna, B R; Selinger, Robin L B; Selinger, Jonathan V

    2016-07-01

    As an approach for electrically controllable actuators, we prepare elastomers of chiral smectic-A liquid crystals, which have an electroclinic effect, i.e., molecular tilt induced by an applied electric field. Surprisingly, our experiments find that an electric field causes a rapid and reversible twisting of the film out of the plane, with a helical sense that depends on the sign of the field. To explain this twist, we develop a continuum elastic theory based on an asymmetry between the front and back of the film. We further present finite-element simulations, which show the dynamic shape change. PMID:27096378

  7. Folding DNA into Twisted and Curved Nanoscale Shapes

    PubMed Central

    Dietz, Hendrik; Douglas, Shawn M.; Shih, William M.

    2009-01-01

    We demonstrate the ability to engineer complex shapes that twist and curve at the nanoscale from DNA. Through programmable self-assembly, strands of DNA are directed to form a custom-shaped bundle of tightly crosslinked double helices, arrayed in parallel to their helical axes. Targeted insertions and deletions of base pairs cause the DNA bundles to develop twist of either handedness or to curve. The degree of curvature could be quantitatively controlled, and a radius of curvature as tight as 6 nanometers was achieved. We also combined multiple curved elements to build several different types of intricate nanostructures, such as a wireframe beach ball or square-toothed gears. PMID:19661424

  8. Status and trends in active control technology

    NASA Technical Reports Server (NTRS)

    Rediess, H. A.; Szalai, K. J.

    1975-01-01

    The emergence of highly reliable fly-by-wire flight control systems makes it possible to consider a strong reliance on automatic control systems in the design optimization of future aircraft. This design philosophy has been referred to as the control configured vehicle approach or the application of active control technology. Several studies and flight tests sponsored by the Air Force and NASA have demonstrated the potential benefits of control configured vehicles and active control technology. The present status and trends of active control technology are reviewed and the impact it will have on aircraft designs, design techniques, and the designer is predicted.

  9. Twisting and Writhing with George Ellery Hale

    NASA Astrophysics Data System (ADS)

    Canfield, Richard C.

    2013-06-01

    Early in his productive career in astronomy, George Ellery Hale developed innovative solar instrumentation that allowed him to make narrow-band images. Among the solar phenomena he discovered were sunspot vortices, which he attributed to storms akin to cyclones in our own atmosphere. Using the concept of magnetic helicity, physicists and mathematicians describe the topology of magnetic fields, including twisting and writhing. Our contemporary understanding of Hale's vortices as a consequence of large-scale twist in sunspot magnetic fields hinges on a key property of helicity: conservation. I will describe the critical role that this property plays, when applied to twist and writhe, in a fundamental aspect of global solar magnetism: the hemispheric and solar cycle dependences of active region electric currents with respect to magnetic fields. With the advent of unbroken sequences of high-resolution magnetic images, such as those presently available from the Helioseismic and Magnetic Imager on Solar Dynamics Observatory, the flux of magnetic helicity through the photosphere can be observed quantitatively. As magnetic flux tubes buoy up through the convection zone, buffeted and shredded by turbulence, they break up into fragments by repeated random bifurcation. We track these rising flux fragments in the photosphere, and calculate the flux of energy and magnetic helicity there. Using a quantitative model of coronal currents, we also track connections between these fragments to calculate the energy and magnetic helicity stored at topological interfaces that are in some ways analogous to the storage of stress at faults in the Earth's crust. Comparison of these values to solar flares and interplanetary coronal mass ejections implies that this is the primary storage mechanism for energy and magnetic helicity released in those phenomena, and suggests a useful tool for quantitative prediction of geomagnetic storms.

  10. Chiral power change upon photoisomerization in twisted nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Simoncelli, Sabrina; Aramendía, Pedro F.

    2015-05-01

    In this work, we use the photoisomerization of azobenzenes, a phenanthrospirooxazine, and a fulgide in a twisted nematic liquid crystalline phase to change the chiral twisting power of the system. The changes are probed by the rotatory power of linearly polarized light. Time resolved and steady state experiments are carried out. The chiral change and the photoisomerization process have similar characteristic recovery times and activation energy, thus probing that the change is induced by the modification in the chemical composition of the photochromic dopant system. The amplitude of the light twisting power change correlates with the order change in the liquid crystal (LC) but not with the modification in the absorption characteristics of the system. This indicates that the driving force of the chiral change is the microscopic order modification in the LC phase that affects the helical pitch of the phase.

  11. Chiral power change upon photoisomerization in twisted nematic liquid crystals.

    PubMed

    Simoncelli, Sabrina; Aramendía, Pedro F

    2015-05-01

    In this work, we use the photoisomerization of azobenzenes, a phenanthrospirooxazine, and a fulgide in a twisted nematic liquid crystalline phase to change the chiral twisting power of the system. The changes are probed by the rotatory power of linearly polarized light. Time resolved and steady state experiments are carried out. The chiral change and the photoisomerization process have similar characteristic recovery times and activation energy, thus probing that the change is induced by the modification in the chemical composition of the photochromic dopant system. The amplitude of the light twisting power change correlates with the order change in the liquid crystal (LC) but not with the modification in the absorption characteristics of the system. This indicates that the driving force of the chiral change is the microscopic order modification in the LC phase that affects the helical pitch of the phase. PMID:25699698

  12. Overview of Langley activities in active controls research

    NASA Technical Reports Server (NTRS)

    Abel, I.; Newsom, J. R.

    1981-01-01

    The application of active controls technology to reduce aeroelastic response of aircraft structures offers a potential for significant payoffs in terms of aerodynamic efficiency and weight savings. The activities of the Langley Research Center (laRC) in advancing active controls technology. Activities are categorized into the development of appropriate analysis tools, control law synthesis methodology, and experimental investigations aimed at verifying both analysis and synthesis methodology.

  13. Endothelial TWIST1 Promotes Pathological Ocular Angiogenesis

    PubMed Central

    Li, Jie; Liu, Chi-Hsiu; Sun, Ye; Gong, Yan; Fu, Zhongjie; Evans, Lucy P.; Tian, Katherine T.; Juan, Aimee M.; Hurst, Christian G.; Mammoto, Akiko; Chen, Jing

    2014-01-01

    Purpose. Pathological neovessel formation impacts many blinding vascular eye diseases. Identification of molecular signatures distinguishing pathological neovascularization from normal quiescent vessels is critical for developing new interventions. Twist-related protein 1 (TWIST1) is a transcription factor important in tumor and pulmonary angiogenesis. This study investigated the potential role of TWIST1 in modulating pathological ocular angiogenesis in mice. Methods. Twist1 expression and localization were analyzed in a mouse model of oxygen-induced retinopathy (OIR). Pathological ocular angiogenesis in Tie2-driven conditional Twist1 knockout mice were evaluated in both OIR and laser-induced choroidal neovascularization models. In addition, the effects of TWIST1 on angiogenesis and endothelial cell function were analyzed in sprouting assays of aortic rings and choroidal explants isolated from Twist1 knockout mice, and in human retinal microvascular endothelial cells treated with TWIST1 small interfering RNA (siRNA). Results. TWIST1 is highly enriched in pathological neovessels in OIR retinas. Conditional Tie2-driven depletion of Twist1 significantly suppressed pathological neovessels in OIR without impacting developmental retinal angiogenesis. In a laser-induced choroidal neovascularization model, Twist1 deficiency also resulted in significantly smaller lesions with decreased vascular leakage. In addition, loss of Twist1 significantly decreased vascular sprouting in both aortic ring and choroid explants. Knockdown of TWIST1 in endothelial cells led to dampened expression of vascular endothelial growth factor receptor 2 (VEGFR2) and decreased endothelial cell proliferation. Conclusions. Our study suggests that TWIST1 is a novel regulator of pathologic ocular angiogenesis and may represent a new molecular target for developing potential therapeutic treatments to suppress pathological neovascularization in vascular eye diseases. PMID:25414194

  14. Renormalization constants for 2-twist operators in twisted mass QCD

    SciTech Connect

    Alexandrou, C.; Constantinou, M.; Panagopoulos, H.; Stylianou, F.; Korzec, T.

    2011-01-01

    Perturbative and nonperturbative results on the renormalization constants of the fermion field and the twist-2 fermion bilinears are presented with emphasis on the nonperturbative evaluation of the one-derivative twist-2 vector and axial-vector operators. Nonperturbative results are obtained using the twisted mass Wilson fermion formulation employing two degenerate dynamical quarks and the tree-level Symanzik improved gluon action. The simulations have been performed for pion masses in the range of about 450-260 MeV and at three values of the lattice spacing a corresponding to {beta}=3.9, 4.05, 4.20. Subtraction of O(a{sup 2}) terms is carried out by performing the perturbative evaluation of these operators at 1-loop and up to O(a{sup 2}). The renormalization conditions are defined in the RI{sup '}-MOM scheme, for both perturbative and nonperturbative results. The renormalization factors, obtained for different values of the renormalization scale, are evolved perturbatively to a reference scale set by the inverse of the lattice spacing. In addition, they are translated to MS at 2 GeV using 3-loop perturbative results for the conversion factors.

  15. MIT Middeck Active Control Experiment (MACE): noncollocated payload pointing control

    NASA Astrophysics Data System (ADS)

    MacMartin, Douglas G.; Miller, David W.

    1993-09-01

    The Middeck Active Control Experiment is a space shuttle flight experiment intended to demonstrate high authority active structural control in zero gravity conditions. The prediction of on-orbit closed-loop dynamics is based on analysis and ground testing. The MACE test article is representative of multiple payload platforms, and includes two 2-axis gimballing payloads connected by a flexible bus. The goal of active control is to maintain pointing accuracy of one payload, while the remaining payload is moving independently. Current control results on the ground test article are presented. Multiple input, multiple output controllers are designed based on high order measurement based models. Linear Quadratic Gaussian controllers yield reasonable performance. At high authority, however, these controllers destabilize the actual structure, due to parametric errors in the control design model. A robust control design procedure is required to yield high performance in the presence of these errors.

  16. Would You Rather (WYR), with a Sexual Health Twist!

    ERIC Educational Resources Information Center

    Rosen, Brittany; McNeill, Elisa Beth; Wilson, Kelly

    2014-01-01

    Would You Rather (WYR), with a Sexual Health Twist! teaching technique uses two youth games, "Would you rather…" and Twister®, to actively engage students in developing decision-making skills regarding human sexuality. Utilizing the "Would you rather" choices, the teacher provides a short scenario with two difficult choices.…

  17. Higher level twisted Zhu algebras

    SciTech Connect

    Ekeren, Jethro van

    2011-05-15

    The study of twisted representations of graded vertex algebras is important for understanding orbifold models in conformal field theory. In this paper, we consider the general setup of a vertex algebra V, graded by {Gamma}/Z for some subgroup {Gamma} of R containing Z, and with a Hamiltonian operator H having real (but not necessarily integer) eigenvalues. We construct the directed system of twisted level p Zhu algebras Zhu{sub p,{Gamma}}(V), and we prove the following theorems: For each p, there is a bijection between the irreducible Zhu{sub p,{Gamma}}(V)-modules and the irreducible {Gamma}-twisted positive energy V-modules, and V is ({Gamma}, H)-rational if and only if all its Zhu algebras Zhu{sub p,{Gamma}}(V) are finite dimensional and semisimple. The main novelty is the removal of the assumption of integer eigenvalues for H. We provide an explicit description of the level p Zhu algebras of a universal enveloping vertex algebra, in particular of the Virasoro vertex algebra Vir{sup c} and the universal affine Kac-Moody vertex algebra V{sup k}(g) at non-critical level. We also compute the inverse limits of these directed systems of algebras.

  18. Reynolds number effects on flow over twisted cylinder with drag reduction and vortex suppression

    NASA Astrophysics Data System (ADS)

    Jung, Jae Hwan; Yoon, Hyun Sik

    2015-11-01

    We investigated the Reynolds number effects on the flow over a twisted cylinder in the range of 3×103 <= Re <=1×104. To analyze the effect of the twisted cylinder, a large eddy simulation (LES) with a dynamic subgrid model was employed. A simulation of the smooth cylinder was also carried out to compare the results with those of the twisted cylinder. As Re increased, the mean drag and lift coefficient of the twisted cylinder increased with the same tendency as those of the smooth cylinder. However, the increases in the mean drag and lift coefficient of the twisted cylinder were much smaller than those of the smooth. Furthermore, elongated shear layer and suppressed vortex shedding from the twisted cylinder occurred compared to those of the smooth cylinder, resulting in a drag reduction and suppression of the vortex-induced vibration (VIV). In particular, the twisted cylinder achieved a significant reduction of over 96% in VIV compared with that of the smooth cylinder, regardless of increasing Re. As a result, we concluded that the twisted cylinder effectively controlled the flow structures with reductions in the drag and VIV compared with the smooth cylinder, irrespective of increasing Re. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) through GCRC-SOP (No. 2011-0030013) and (NRF-2015R1D1A3A01020867).

  19. Orbiter active thermal control system description

    NASA Technical Reports Server (NTRS)

    Laubach, G. E.

    1975-01-01

    A brief description of the Orbiter Active Thermal Control System (ATCS) including (1) major functional requirements of heat load, temperature control and heat sink utilization, (2) the overall system arrangement, and (3) detailed description of the elements of the ATCS.

  20. Developing Internal Controls through Activities

    ERIC Educational Resources Information Center

    Barnes, F. Herbert

    2009-01-01

    Life events can include the Tuesday afternoon cooking class with the group worker or the Saturday afternoon football game, but in the sense that Fritz Redl thought of them, these activities are only threads in a fabric of living that includes all the elements of daily life: playing, working, school-based learning, learning through activities,…

  1. "Twisted Beam" SEE Observations of Ionospheric Heating from HAARP

    NASA Astrophysics Data System (ADS)

    Briczinski, S. J.; Bernhardt, P. A.; Pedersen, T. R.; Rodriguez, S.; SanAntonio, G.

    2012-12-01

    High power HF radio waves exciting the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaksa is the world's largest heating facility, providing effective radiated powers in the gigawatt range. Experiments performed at HAARP have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emission (SEE) is of interest to the ionospheric community for its diagnostic purposes. Typical SEE experiments at HAARP have focused on characterizing the parametric decay of the electromagnetic pump wave into several different wave modes such as upper and lower hybrid, ion acoustic, ion-Bernstein and electron-Bernstein. These production modes have been extensively studied at HAARP using traditional beam heating patterns and SEE detection. New results are present from HAARP experiments using a "twisted beam" excitation mode. Unlike traditional heating beams used at HAARP or other heating facilities, the twisted beam attempts to impart orbital angular momentum (OAM) into the heating region. Analysis of twisted beam heating shows that the SEE results obtained are nearly identical to the modes without OAM. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional "solid spot" region. The ring heating pattern may be more conducive to the creation of artificial airglow layers. The results of these runs include artificial layer creation and evolution as pertaining to the twisted beam pattern. The SEE measurements aid the interpretation of the twisted beam interactions in the ionosphere.

  2. Active Compliance And Damping In Telemanipulator Control

    NASA Technical Reports Server (NTRS)

    Kim, Won S.; Bejczy, Antal K.; Hannaford, Blake

    1991-01-01

    Experimental telemanipulator system of force-reflecting-hand-controller type provides for active compliance and damping in remote, robotic manipulator hand. Distributed-computing and -control system for research in various combinations of force-reflecting and active-compliance control regimes. Shared compliance control implemented by low-pass-filtered force/torque feedback. Variable simulated springs and shock absorbers soften collisions and increase dexterity.

  3. The Middeck Active Control Experiment (MACE)

    NASA Technical Reports Server (NTRS)

    Miller, David W.

    1992-01-01

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: program objectives; program features; flight experiment features; current activities; MACE development model lab testing; MACE test article deployed on STS middeck; and development model testing.

  4. The Middeck Active Control Experiment (MACE)

    NASA Astrophysics Data System (ADS)

    Miller, David W.

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: program objectives; program features; flight experiment features; current activities; MACE development model lab testing; MACE test article deployed on STS middeck; and development model testing.

  5. Twist plays an essential role in FGF and SHH signal transduction during mouse limb development.

    PubMed

    O'Rourke, Meredith P; Soo, Kenneth; Behringer, Richard R; Hui, Chi-Chung; Tam, Patrick P L

    2002-08-01

    Loss of Twist gene function arrests the growth of the limb bud shortly after its formation. In the Twist(-/-) forelimb bud, Fgf10 expression is reduced, Fgf4 is not expressed, and the domain of Fgf8 and Fgfr2 expression is altered. This is accompanied by disruption of the expression of genes (Shh, Gli1, Gli2, Gli3, and Ptch) associated with SHH signalling in the limb bud mesenchyme, the down-regulation of Bmp4 in the apical ectoderm, the absence of Alx3, Alx4, Pax1, and Pax3 activity in the mesenchyme, and a reduced potency of the limb bud tissues to differentiate into osteogenic and myogenic tissues. Development of the hindlimb buds in Twist(-/-) embryos is also retarded. The overall activity of genes involved in SHH signalling is reduced.Fgf4 and Fgf8 expression is lost or reduced in the apical ectoderm, but other genes (Fgf10, Fgfr2) involved with FGF signalling are expressed in normal patterns. Twist(+/-);Gli3(+/XtJ) mice display more severe polydactyly than that seen in either Twist(+/-) or Gli3(+/XtJ) mice, suggesting that there is genetic interaction between Twist and Gli3 activity. Twist activity is therefore essential for the growth and differentiation of the limb bud tissues as well as regulation of tissue patterning via the modulation of SHH and FGF signal transduction. PMID:12142027

  6. The Middeck Active Control Experiment (MACE): Identification for robust control

    NASA Astrophysics Data System (ADS)

    Karlov, Valery I.

    Viewgraphs on identification for robust control for the Middeck Active Control Experiment (MACE) are presented. Topics covered include: identification for robust control; three levels of identification; basic elements of the approach; advantages of 'post-ID' model of uncertainty; advantages of optimization; and practical realization.

  7. The Middeck Active Control Experiment (MACE): Identification for robust control

    NASA Technical Reports Server (NTRS)

    Karlov, Valery I.

    1992-01-01

    Viewgraphs on identification for robust control for the Middeck Active Control Experiment (MACE) are presented. Topics covered include: identification for robust control; three levels of identification; basic elements of the approach; advantages of 'post-ID' model of uncertainty; advantages of optimization; and practical realization.

  8. Regulation of the Mechanism of TWIST1 Transcription by BHLHE40 and BHLHE41 in Cancer Cells.

    PubMed

    Asanoma, Kazuo; Liu, Ge; Yamane, Takako; Miyanari, Yoko; Takao, Tomoka; Yagi, Hiroshi; Ohgami, Tatsuhiro; Ichinoe, Akimasa; Sonoda, Kenzo; Wake, Norio; Kato, Kiyoko

    2015-12-01

    BHLHE40 and BHLHE41 (BHLHE40/41) are basic helix-loop-helix type transcription factors that play key roles in multiple cell behaviors. BHLHE40/41 were recently shown to be involved in an epithelial-to-mesenchymal transition (EMT). However, the precise mechanism of EMT control by BHLHE40/41 remains unclear. In the present study, we demonstrated that BHLHE40/41 expression was controlled in a pathological stage-dependent manner in human endometrial cancer (HEC). Our in vitro assays showed that BHLHE40/41 suppressed tumor cell invasion. BHLHE40/41 also suppressed the transcription of the EMT effectors SNAI1, SNAI2, and TWIST1. We identified the critical promoter regions of TWIST1 for its basal transcriptional activity. We elucidated that the transcription factor SP1 was involved in the basal transcriptional activity of TWIST1 and that BHLHE40/41 competed with SP1 for DNA binding to regulate gene transcription. This study is the first to report the detailed functions of BHLHE40 and BHLHE41 in the suppression of EMT effectors in vitro. Our results suggest that BHLHE40/41 suppress tumor cell invasion by inhibiting EMT in tumor cells. We propose that BHLHE40/41 are promising markers to predict the aggressiveness of each HEC case and that molecular targeting strategies involving BHLHE40/41 and SP1 may effectively regulate HEC progression. PMID:26391953

  9. Twisted complex superfluids in optical lattices

    NASA Astrophysics Data System (ADS)

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-09-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid.

  10. Twisted complex superfluids in optical lattices.

    PubMed

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-01-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose-Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721

  11. Twisted complex superfluids in optical lattices

    PubMed Central

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-01-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721

  12. Analysis of twisted supercharge families on product manifolds

    NASA Astrophysics Data System (ADS)

    Harju, Antti J.

    2015-04-01

    Twisted supercharge families on product manifolds 𝕋 × M have been applied in the analysis of the odd twisted K-theory. We shall suspend these families to the even twisted K-theory and solve their twisted families index problem. This is applied to give analytic representatives of the twisted K-theory classes on tori—including all the torsion classes.

  13. Twisted Logarithmic Modules of Vertex Algebras

    NASA Astrophysics Data System (ADS)

    Bakalov, Bojko

    2016-07-01

    Motivated by logarithmic conformal field theory and Gromov-Witten theory, we introduce a notion of a twisted module of a vertex algebra under an arbitrary (not necessarily semisimple) automorphism. Its main feature is that the twisted fields involve the logarithm of the formal variable. We develop the theory of such twisted modules and, in particular, derive a Borcherds identity and commutator formula for them. We investigate in detail the examples of affine and Heisenberg vertex algebras.

  14. Student Activity Funds: Procedures & Controls.

    ERIC Educational Resources Information Center

    Cuzzetto, Charles E.

    Student activity funds may create educational opportunities for students, but they frequently create problems for business administrators. The first part of this work reviews the types of organizational issues and transactions an organized student group is likely to encounter, including establishing a constitution, participant roles,…

  15. DVCS amplitude with kinematical twist-3 terms

    SciTech Connect

    Radyushkin, A.V.; Weiss, C.

    2000-08-01

    The authors compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude they include the operators of twist-3 which appear as total derivatives of twist-2 operators. The results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. They find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.

  16. Active-member control of precision structures

    NASA Technical Reports Server (NTRS)

    Fanson, J. L.; Blackwood, G. H.; Chu, C. C.

    1989-01-01

    This paper presents the results of closed loop experiments that use piezoelectric active-members to control the flexible motion of a precision truss structure. These experiments are directed toward the development of high performance structural systems as part of the Control/Structure Interaction program at JPL. Order of magnitude reductions in dynamic response are achieved with relatively simple control techniques. The practical implementation of high stiffness, high bandwidth active-members in a precision structure highlights specific issues of importance relating to the modelling and implementation of active-member control.

  17. Actively controlled shaft seals for aerospace applications

    NASA Technical Reports Server (NTRS)

    Salant, Richard F.

    1991-01-01

    Actively controlled mechanical seals have recently been developed for industrial use. This study investigates the feasibility of using such seals for aerospace applications. In a noncontacting mechanical seal, the film thickness depends on the geometry of the seal interface. The amount of coning, which is a measure of the radial convergence or divergence of the seal interface, has a primary effect on the film thickness. Active control of the film thickness is established by controlling the coning with a piezoelectric material. A mathematical model has been formulated to predict the performance of an actively controlled mechanical seal.

  18. Active Control Of Structure-Borne Noise

    NASA Astrophysics Data System (ADS)

    Elliott, S. J.

    1994-11-01

    The successful practical application of active noise control requires an understanding of both its acoustic limitations and the limitations of the electrical control strategy used. This paper is concerned with the active control of sound in enclosures. First, a review is presented of the fundamental physical limitations of using loudspeakers to achieve either global or local control. Both approaches are seen to have a high frequency limit, due to either the acoustic modal overlap, or the spatial correlation function of the pressure field. These physical performance limits could, in principle, be achieved with either a feedback or a feedforward control strategy. These strategies are reviewed and the use of adaptive digital filters is discussed for both approaches. The application of adaptive feedforward control in the control of engine and road noise in cars is described. Finally, an indirect approach to the active control of sound is discussed, in which the vibration is suppressed in the structural paths connecting the source of vibration to the enclosure. Two specific examples of this strategy are described, using an active automotive engine mount and the incorporation of actuators into helicopter struts to control gear-meshing tones. In both cases good passive design can minimize the complexity of the active controller.

  19. Field Test Results from a 10 kW Wind Turbine with Active Flow Control

    NASA Astrophysics Data System (ADS)

    Rice, Thomas; Bychkova, Veronika; Taylor, Keith; Clingman, Dan; Amitay, Michael

    2015-11-01

    Active flow control devices including synthetic jets and dynamic vortex generators were tested on a 10 kW wind turbine at RPI. Previous work has shown that load oscillations caused by dynamic stall could be modified through the use of active flow control by injecting momentum into the flow field near the leading edge of a dynamically pitching model. In this study, this work has been extended to its logical conclusion, field-testing active flow control on a real wind turbine. The blades in the current study have a 0.28m chord and 3.05m span, no twist or taper, and were retrofitted with six synthetic jets on one blade and ten dynamic vortex generators on a second blade. The third blade of this turbine was not modified, in order to serve as a control. Strain gauges were installed on each blade to measure blades' deflection. A simple closed loop control was demonstrated and preliminary results indicate reduced vibrational amplitude. Future testing will be conducted on a larger scale, 600kW machine at NREL, incorporating information collected during this study.

  20. Thymoquinone inhibits cancer metastasis by downregulating TWIST1 expression to reduce epithelial to mesenchymal transition

    PubMed Central

    Khan, Md. Asaduzzaman; Tania, Mousumi; Wei, Chunli; Mei, Zhiqiang; Fu, Shelly; Cheng, Jingliang; Xu, Jianming; Fu, Junjiang

    2015-01-01

    Proteins that promote epithelial to mesenchymal transition (EMT) are associated with cancer metastasis. Inhibition of EMT regulators may be a promising approach in cancer therapy. In this study, Thymoquinone (TQ) was used to treat cancer cell lines to investigate its effects on EMT-regulatory proteins and cancer metastasis. We show that TQ inhibited cancer cell growth, migration and invasion in a dose-dependent manner. At the molecular level, TQ treatment decreased the transcriptional activity of the TWIST1 promoter and the mRNA expression of TWIST1, an EMT-promoting transcription factor. Accordingly, TQ treatment also decreased the expression of TWIST1-upregulated genes such as N-Cadherin and increased the expression of TWIST1-repressed genes such as E-Cadherin, resulting in a reduction of cell migration and invasion. TQ treatment also inhibited the growth and metastasis of cancer cell-derived xenograft tumors in mice but partially attenuated the migration and invasion in TWIST1-overexpressed cell lines. Furthermore, we found that TQ treatment enhanced the promoter DNA methylation of the TWIST1 gene in BT 549 cells. Together, these results demonstrate that TQ treatment inhibits TWIST1 promoter activity and decreases its expression, leading to the inhibition of cancer cell migration, invasion and metastasis. These findings suggest TQ as a potential small molecular inhibitor of cancer growth and metastasis. PMID:26023736

  1. Active vibration control of lightweight floor systems

    NASA Astrophysics Data System (ADS)

    Baader, J.; Fontana, M.

    2016-04-01

    Wide-span and lightweight floors are often prone to structural vibrations due to their low resonance frequency and poor material damping. Their dynamic behaviour can be improved using passive, semi-active or active vibration control devices. The following article proposes a novel method for the controller synthesis for active vibration control. An existing passive TMD (tuned mass damper) is modelled and equipped with an actuator in order to provide more efficient damping. Using an iterative optimization approach under constraints, an optimal controller is found which minimizes a quadratic cost function in frequency domain. A simulation of an existing test bench shows that the active vibration control device is able to provide increased damping compared to the passive TMD.

  2. Twisted liquid crystal pi cell stabilized by polymer-sustained alignment

    SciTech Connect

    Chen, T.-J.; Cheng, Y.-H.; Wu, S.-M.

    2008-12-01

    A uniform {pi}-twist liquid crystal (LC) alignment was stabilized in a pi cell by photopolymerization of a minute amount of monomers without using any chiral material. Controlling UV exposure time can vary the LC pretilt angle to achieve a stabilized {pi}-twist state. This type of {pi}-twisted LC cell made using the polymer-sustained alignment has a pretilt angle estimated to be {approx}20 deg. This cell can quickly transform into a bend state at a low driving voltage and shows excellent brightness and optical contrast, as compared with a conventional pi cell and a chiral-doped cell.

  3. Reliable and Affordable Control Systems Active Combustor Pattern Factor Control

    NASA Technical Reports Server (NTRS)

    McCarty, Bob; Tomondi, Chris; McGinley, Ray

    2004-01-01

    Active, closed-loop control of combustor pattern factor is a cooperative effort between Honeywell (formerly AlliedSignal) Engines and Systems and the NASA Glenn Research Center to reduce emissions and turbine-stator vane temperature variations, thereby enhancing engine performance and life, and reducing direct operating costs. Total fuel flow supplied to the engine is established by the speed/power control, but the distribution to individual atomizers will be controlled by the Active Combustor Pattern Factor Control (ACPFC). This system consist of three major components: multiple, thin-film sensors located on the turbine-stator vanes; fuel-flow modulators for individual atomizers; and control logic and algorithms within the electronic control.

  4. Deciphering the molecular mechanisms underlying the binding of the TWIST1/E12 complex to regulatory E-box sequences.

    PubMed

    Bouard, Charlotte; Terreux, Raphael; Honorat, Mylène; Manship, Brigitte; Ansieau, Stéphane; Vigneron, Arnaud M; Puisieux, Alain; Payen, Léa

    2016-06-20

    The TWIST1 bHLH transcription factor controls embryonic development and cancer processes. Although molecular and genetic analyses have provided a wealth of data on the role of bHLH transcription factors, very little is known on the molecular mechanisms underlying their binding affinity to the E-box sequence of the promoter. Here, we used an in silico model of the TWIST1/E12 (TE) heterocomplex and performed molecular dynamics (MD) simulations of its binding to specific (TE-box) and modified E-box sequences. We focused on (i) active E-box and inactive E-box sequences, on (ii) modified active E-box sequences, as well as on (iii) two box sequences with modified adjacent bases the AT- and TA-boxes. Our in silico models were supported by functional in vitro binding assays. This exploration highlighted the predominant role of protein side-chain residues, close to the heart of the complex, at anchoring the dimer to DNA sequences, and unveiled a shift towards adjacent ((-1) and (-1*)) bases and conserved bases of modified E-box sequences. In conclusion, our study provides proof of the predictive value of these MD simulations, which may contribute to the characterization of specific inhibitors by docking approaches, and their use in pharmacological therapies by blocking the tumoral TWIST1/E12 function in cancers. PMID:27151200

  5. Deciphering the molecular mechanisms underlying the binding of the TWIST1/E12 complex to regulatory E-box sequences

    PubMed Central

    Bouard, Charlotte; Terreux, Raphael; Honorat, Mylène; Manship, Brigitte; Ansieau, Stéphane; Vigneron, Arnaud M.; Puisieux, Alain; Payen, Léa

    2016-01-01

    The TWIST1 bHLH transcription factor controls embryonic development and cancer processes. Although molecular and genetic analyses have provided a wealth of data on the role of bHLH transcription factors, very little is known on the molecular mechanisms underlying their binding affinity to the E-box sequence of the promoter. Here, we used an in silico model of the TWIST1/E12 (TE) heterocomplex and performed molecular dynamics (MD) simulations of its binding to specific (TE-box) and modified E-box sequences. We focused on (i) active E-box and inactive E-box sequences, on (ii) modified active E-box sequences, as well as on (iii) two box sequences with modified adjacent bases the AT- and TA-boxes. Our in silico models were supported by functional in vitro binding assays. This exploration highlighted the predominant role of protein side-chain residues, close to the heart of the complex, at anchoring the dimer to DNA sequences, and unveiled a shift towards adjacent ((-1) and (-1*)) bases and conserved bases of modified E-box sequences. In conclusion, our study provides proof of the predictive value of these MD simulations, which may contribute to the characterization of specific inhibitors by docking approaches, and their use in pharmacological therapies by blocking the tumoral TWIST1/E12 function in cancers. PMID:27151200

  6. Symmetry fractionalization and twist defects

    NASA Astrophysics Data System (ADS)

    Tarantino, Nicolas; Lindner, Netanel H.; Fidkowski, Lukasz

    2016-03-01

    Topological order in two-dimensions can be described in terms of deconfined quasiparticle excitations—anyons—and their braiding statistics. However, it has recently been realized that this data does not completely describe the situation in the presence of an unbroken global symmetry. In this case, there can be multiple distinct quantum phases with the same anyons and statistics, but with different patterns of symmetry fractionalization—termed symmetry enriched topological order. When the global symmetry group G, which we take to be discrete, does not change topological superselection sectors—i.e. does not change one type of anyon into a different type of anyon—one can imagine a local version of the action of G around each anyon. This leads to projective representations and a group cohomology description of symmetry fractionalization, with the second cohomology group {H}2(G,{{ A }}{{abelian}}) being the relevant group. In this paper, we treat the general case of a symmetry group G possibly permuting anyon types. We show that despite the lack of a local action of G, one can still make sense of a so-called twisted group cohomology description of symmetry fractionalization, and show how this data is encoded in the associativity of fusion rules of the extrinsic ‘twist’ defects of the symmetry. Furthermore, building on work of Hermele (2014 Phys. Rev. B 90 184418), we construct a wide class of exactly-solvable models which exhibit this twisted symmetry fractionalization, and connect them to our formal framework.

  7. Active Control by Conservation of Energy Concept

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio

    2000-01-01

    Three unrelated experiments are discussed; each was extremely sensitive to initial conditions. The initial conditions are the beginnings of the origins of the information that nonlinearity displays. Initial conditions make the phenomenon unstable and unpredictable. With the knowledge of the initial conditions, active control requires far less power than that present in the system response. The first experiment is on the control of shocks from an axisymmetric supersonic jet; the second, control of a nonlinear panel response forced by turbulent boundary layer and sound; the third, control of subharmonic and harmonics of a panel forced by sound. In all three experiments, control is achieved by redistribution of periodic energy response such that the energy is nearly preserved from a previous uncontrolled state. This type of active control improves the performance of the system being controlled.

  8. Twisting of glycosidic bonds by hydrolases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Patterns of scissile bond twisting have been found in crystal structures of glycoside hydrolases (GHs) that are complexed with substrates and inhibitors. To estimate the increased potential energy in the substrates that results from this twisting, we have plotted torsion angles for the scissile bond...

  9. Optical angular properties of twisted-nematic liquid-crystal cells with twist angles of less than 90 degrees

    NASA Astrophysics Data System (ADS)

    Palmer, Stephen

    1996-05-01

    I analyze the optical angular properties of twisted-nematic liquid-crystal cells that operate in the normally white mode with twist angles of less than 90 degrees. It is demonstrated that, although a reduction of the twist angle produces an increase in the asymmetry of the birefringence generated by a single cell when in the active phase, the positioning of two cells such that the face-to-face rub directions are crossed gives rise to a large amount of cell compensation, giving an enhanced field of view. The effect of the polarizer arrangement is investigated, and it is shown that the configuration required in order to maximize the overall optical transmittance when in the inactive phase also maintains the asymmetry displayed by the single cell when stimulated by voltages lying below that of the saturation voltage. Although employment of this polarizer design together with a lowering of the twist angle degrades cell contrast, a fast optical shutter from the light to the dark state based on a double-cell construction possessing improved optical angular properties is introduced. Such systems find applications in automatically darkening welding filter visors for which it is critical to combine both a fast response time to the protective state together with a large viewing cone.

  10. STOUT SMEARING FOR TWISTED FERMIONS.

    SciTech Connect

    SCHOLZ,W.; JANSEN, K.; McNEILE, C.; MONTVAY, I.; RICHARDS, C.; URBACH, C.; WENGER, U.

    2007-07-30

    The effect of Stout smearing is investigated in numerical simulations with twisted mass Wilson quarks. The phase transition near zero quark mass is studied on 12{sup 3} x 24, 16{sup 3} x 32 and 24{sup 3} x 48 lattices at lattice spacings a {approx_equal} 0.1-0.125 fm. The phase structure of Wilson fermions with twisted mass ({mu}) has been investigated in [1,2]. As it is explained there, the observed first order phase transition limits the minimal pion mass which can be reached in simulations at a given lattice spacing: m{sub k}{sup min} {approx_equal} {theta}(a). The phase structure is schematically depicted in the left panel of Fig. I . The phase transition can be observed in simulations with twisted mass fermions, for instance, as a ''jump'' or even metastabilities in the average plaquette value as a function of the hopping parameter ({kappa}). One possibility to weaken the phase transition and therefore allow for lighter pion masses at a given lattice spacing is to use an improved gauge action like the DBW2, Iwasaki, or tree-level Symanzik (tlSym) improved gauge action instead of the simple Wilson gauge action. This has been successfully demonstrated in [3,4,5]. Here we report on our attempts to use a smeared gauge field in the fermion lattice Dirac operator to further reduce the strength of the phase transition. This is relevant in simulations with N{sub f} = 2 + 1 + 1 (u,d,s,c) quark flavors [6] where the first order phase transition becomes stronger compared to N{sub f} = 2 simulations. The main impact of the above mentioned improved gauge actions on the gauge fields occurring in simulations is to suppress short range fluctuations (''dislocations'') and the associated ''exceptionally small'' eigenvalues of the fermion matrix. The same effect is expected from smearing the gauge field links in the fermion action. The cumulated effect of the improved gauge action and smeared links should allow for a smaller pion mass at a given lattice spacing and volume. Our

  11. Active control of buildings during earthquakes

    NASA Technical Reports Server (NTRS)

    Vance, Vicki L.

    1993-01-01

    The objective of this report is to provide an overview of the different types of control systems used in buildings, to discuss the problems associated with current active control mechanisms, and to show the cost-effectiveness of applying active control to buildings. In addition, a small case study investigates the feasibility and benefits of using embedded actuators in buildings. Use of embedded actuators could solve many of the current problems associated with active control by providing a wider bandwidth of control, quicker speed of response, increased reliability and reduced power requirement. Though embedded actuators have not been developed for buildings, they have previously been used in space structures. Many similarities exist between large civil and aerospace structures indicating that direct transfer of concepts between the two disciplines may be possible. In particular, much of the Controls-Structures Interaction (CSI) technology currently being developed could be beneficially applied to civil structures. While several buildings with active control systems have been constructed in Japan, additional research and experimental verification are necessary before active control systems become widely accepted and implemented.

  12. Manually controlled neutron-activation system

    NASA Astrophysics Data System (ADS)

    Johns, R. A.; Carothers, G. A.

    1982-01-01

    A manually controlled neutron activation system, the Manual Reactor Activation System, was designed and built and has been operating at one of the Savannah River Plant's production reactors. With this system, samples can be irradiated for up to 24 hours and pneumatically transferred to a shielded repository for decay until their activity is low enough for them to be handled at a radiobench. The Manual Reactor Activation System was built to provide neutron activation of solid waste forms for the Alternative Waste Forms Leach Testing Program. Neutron activation of the bulk sample prior to leaching permits sensitive multielement radiometric analyses of the leachates.

  13. Controls on fire activity over the Holocene

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Brucher, T.; Brovkin, V.; Wilkenskjeld, S.

    2015-05-01

    Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed, which react differently to changes in climate. Disentangling these controlling factors helps in understanding the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP, with larger regional changes compensating nearly evening out on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental-scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia monsoon, Central America tropics/subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such, observed changes in fire activity cannot be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help in understanding the climate control on fire activity, which is essential to project future fire

  14. MyoD transcription factor induces myogenesis by inhibiting Twist-1 through miR-206.

    PubMed

    Koutalianos, Demetris; Koutsoulidou, Andrie; Mastroyiannopoulos, Nikilaos P; Furling, Denis; Phylactou, Leonidas A

    2015-10-01

    Twist-1 is mostly expressed during development and has been previously shown to control myogenesis. Because its regulation in muscle has not been fully exploited, the aim of this project was to identify micro (mi)RNAs in muscle that regulate Twist-1. miR-206, one of the most important muscle-specific miRNAs (myomiRs), was identified as a possible regulator of Twist-1 mRNA. Luciferase assays and transfections in human foetal myoblasts showed that Twist-1 is a direct target of miR-206 and that through this pathway muscle cell differentiation is promoted. We next investigated whether MyoD, a major myogenic transcription factor, regulates Twist-1 because it is known that MyoD induces expression of the miR-206 gene. We found that forced MyoD expression induced miR-206 upregulation and Twist-1 downregulation through binding to the miR-206 promoter, followed by increased muscle cell differentiation. Finally, experiments were performed in muscle cells from subjects with congenital myotonic dystrophy type 1, in which myoblasts fail to differentiate into myotubes. MyoD overexpression inhibited Twist-1 through miR-206 induction, which was followed by an increase in muscle cell differentiation. These results reveal a previously unidentified mechanism of myogenesis that might also play an important role in muscle disease. PMID:26272918

  15. ACTIVELY CONTROLLED AFTERBURNER FOR COMPACT WASTE INCINERATION

    EPA Science Inventory

    In a continuing research program directed at developing technology for compact shipboard incinerators, active control of fluid dynamics has been used to enhance mixing in incinerator afterburner (AB) experiments and increase the DRE for a waste surrogate. Experiments were conduc...

  16. The Middeck Active Control Experiment (MACE)

    NASA Astrophysics Data System (ADS)

    Miller, David W.

    1991-07-01

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: science program objectives and rationale; science requirements; capturing the essential physics; science development approach; development model hardware; development model test plan; and flight hardware and operations.

  17. The Middeck Active Control Experiment (MACE)

    NASA Technical Reports Server (NTRS)

    Miller, David W.

    1991-01-01

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: science program objectives and rationale; science requirements; capturing the essential physics; science development approach; development model hardware; development model test plan; and flight hardware and operations.

  18. Active control of turbomachine discrete tones

    NASA Astrophysics Data System (ADS)

    Fleeter, Sanford

    This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.

  19. Active Polymer Microfiber with Controlled Polarization Sensitivity

    PubMed Central

    Xia, Hongyan; Wang, Ruxue; Liu, Yingying; Cheng, Junjie; Zou, Gang; Zhang, Qijin; Zhang, Douguo; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

    2016-01-01

    Controlled Polarization Sensitivity of an active polymer microfiber has been proposed and realized with the electrospun method. The fluorescence intensity guiding through this active polymer microfiber shows high sensitivity to the polarization state of the excitation light. What is more, the fluorescence out-coupled from tip of the microfiber can be of designed polarization state. Principle of these phenomena lies on the ordered and controlled orientation of the polydiacetylene (PDA) main chains inside polymer microfiber. PMID:27099828

  20. Active control of helicopter transmission noise

    NASA Astrophysics Data System (ADS)

    Spencer, R. H.; Burke, M. J.; Tye, G. W.

    An account is given of an effort to reduce helicopter transmission noise by 10 dB, using active methods, as part of the NASA-Lewis/U.S. Army Propulsion Directorate Advanced Rotorcraft Transmission technology integration and demonstration program. The transmission used as a test stand is that of the CH-47C forward rotor. Attention is presently given to the active control system's actuators, sensors, and control algorithms.

  1. Active control of helicopter transmission noise

    NASA Technical Reports Server (NTRS)

    Spencer, R. H.; Burke, M. J.; Tye, G. W.

    1991-01-01

    An account is given of an effort to reduce helicopter transmission noise by 10 dB, using active methods, as part of the NASA-Lewis/U.S. Army Propulsion Directorate Advanced Rotorcraft Transmission technology integration and demonstration program. The transmission used as a test stand is that of the CH-47C forward rotor. Attention is presently given to the active control system's actuators, sensors, and control algorithms.

  2. Vector control activities, fiscal year 1983

    SciTech Connect

    Pickard, E.; Cooney, J.C.; McDuff, B.R.

    1984-07-01

    The goal of the Vector Control Program is to safeguard public health and well-being in the Tennessee Valley region by controlling arthropod pests of medical importance that are propagated on TVA lands or waters or that are produced as a result of TVA activities. To achieve this goal the program is divided into two major categories consisting of operations and support studies. The latter is geared to improving the operational effectiveness and efficiency of the control program and to identify additional vector control problems requiring TVA attention and study. Nonchemical methods of control are emphasized and are supplemented with chemical measures as needed.

  3. Twisting integrin receptors increases endothelin-1 gene expression in endothelial cells

    NASA Technical Reports Server (NTRS)

    Chen, J.; Fabry, B.; Schiffrin, E. L.; Wang, N.; Ingber, D. E. (Principal Investigator)

    2001-01-01

    A magnetic twisting stimulator was developed based on the previously published technique of magnetic twisting cytometry. Using ligand-coated ferromagnetic microbeads, this device can apply mechanical stresses with varying amplitudes, duration, frequencies, and waveforms to specific cell surface receptors. Biochemical and biological responses of the cells to the mechanical stimulation can be assayed. Twisting integrin receptors with RGD (Arg-Gly-Asp)-containing peptide-coated beads increased endothelin-1 (ET-1) gene expression by >100%. In contrast, twisting scavenger receptors with acetylated low-density lipoprotein-coated beads or twisting HLA antigen with anti-HLA antibody-coated beads did not lead to alterations in ET-1 gene expression. In situ hybridization showed that the increase in ET-1 mRNA was localized in the cells that were stressed with the RGD-coated beads. Blocking stretch-activated ion channels with gadolinium, chelating Ca2+ with EGTA, or inhibiting tyrosine phosphorylation with genistein abolished twist-induced ET-1 mRNA elevation. Abolishing cytoskeletal tension with an inhibitor of the myosin ATPase, with an inhibitor of myosin light chain kinase, or with an actin microfilament disrupter blocked twisted-induced increases in ET-1 expression. Our results are consistent with the hypothesis that the molecular structural linkage of integrin-cytoskeleton is an important pathway for stress-induced ET-1 gene expression.

  4. Transitioning Active Flow Control to Applications

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.; Horta, Lucas G.; Chen, Fang-Jenq

    1999-01-01

    Active Flow Control Programs at NASA, the U.S. Air Force, and DARPA have been initiated with the goals of obtaining revolutionary advances in aerodynamic performance and maneuvering compared to conventional approaches. These programs envision the use of actuators, sensors, and controllers on applications such as aircraft wings/tails, engine nacelles, internal ducts, nozzles, projectiles, weapons bays, and hydrodynamic vehicles. Anticipated benefits of flow control include reduced weight, part count, and operating cost and reduced fuel burn (and emissions), noise and enhanced safety if the sensors serve a dual role of flow control and health monitoring. To get from the bench-top or laboratory test to adaptive distributed control systems on realistic applications, reliable validated design tools are needed in addition to sub- and large-scale wind-tunnel and flight experiments. This paper will focus on the development of tools for active flow control applications.

  5. Active load control techniques for wind turbines.

    SciTech Connect

    van Dam, C.P.; Berg, Dale E.; Johnson, Scott J.

    2008-07-01

    This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

  6. Student Activity Funds: Procedures and Controls.

    ERIC Educational Resources Information Center

    Cuzzetto, Charles E.

    2000-01-01

    An effective internal-control system can help school business administrators meet the challenges of accounting for student activity funds. Such a system should include appropriate policies and procedures, identification of key control points, self-assessments, audit trails, and internal and external audits. (MLH)

  7. Optimal active control for Burgers equations

    NASA Technical Reports Server (NTRS)

    Ikeda, Yutaka

    1994-01-01

    A method for active fluid flow control based on control theory is discussed. Dynamic programming and fixed point successive approximations are used to accommodate the nonlinear control problem. The long-term goal of this project is to establish an effective method applicable to complex flows such as turbulence and jets. However, in this report, the method is applied to stochastic Burgers equation as an intermediate step towards this goal. Numerical results are compared with those obtained by gradient search methods.

  8. Methods and apparatus for twist bend coupled (TCB) wind turbine blades

    DOEpatents

    Moroz, Emilian Mieczyslaw; LeMieux, David Lawrence; Pierce, Kirk Gee

    2006-10-10

    A method for controlling a wind turbine having twist bend coupled rotor blades on a rotor mechanically coupled to a generator includes determining a speed of a rotor blade tip of the wind turbine, measuring a current twist distribution and current blade loading, and adjusting a torque of a generator to change the speed of the rotor blade tip to thereby increase an energy capture power coefficient of the wind turbine.

  9. Active and adaptive flow control of twin-tail buffet and applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhi

    2002-01-01

    Modern fighter aircraft with dual vertical tails are operated at high angles of attack. The vortex generated by leading edge extension (LEX) breaks down before reaching the two vertical tails. The wake of highly unsteady, turbulent flow causes unbalanced broadband aerodynamic loading on the tails and may produce severe buffet on the tails and lead to tail fatigue failure. Flow suction along the vortex cores (FSVC) is investigated as an active control method for tail-buffet alleviation. Suction tubes have been tilted at different angles to study the control effectiveness of suction tubes orientation. Flow field response, aerodynamic loading and aeroelastic results are compared with the no-control case. These flow modifications produce lower tip bending and rotation angle deflections and accelerations. Moreover, the root bending and twisting moments are reduced in comparison with the no-control case. However, there was no shift in the frequencies at which the peaks of the power spectral density (PSD) responses occurred. The primary effect of the FSVC methods is the amplitude reduction of the aeroelastic responses up to 30%. A parametric investigation is conducted and the best control effectiveness is obtained with the suction tubes tilted at -10°. Next, the twin-tail buffet alleviation is addressed by using adaptive flow control, and an adaptive active control method is developed. Control ports, whose locations are determined according to the locations of a range of high-pressure difference, are placed within a small area on the tail surfaces. Flow suction and blowing are applied through these control ports in order to equalize the pressures on the two surfaces of the tail. Mass flow rate through each port is proportional to the pressure difference across the tail at the location of this port. Comparing the flow field and aeroelastic response with the no-control case, the normal-force and twisting-moment distributions are substantially decreased along with the

  10. Block Copolymers with a Twist

    SciTech Connect

    Ho, R.; Chiang, Y; Chen, C; Wang, H; Hasegawa, H; Akasaka, S; Thomas, E; Burger, C; Hsiao, B

    2009-01-01

    Chiral block copolymers (BCPs*) comprising chiral entities were designed to fabricate helical architectures (i.e., twisted morphologies) from self-assembly. A new helical phase (H*) with P622 symmetry was discovered in the self-assembly of poly(styrene)-b-poly(l-lactide) (PS-PLLA) BCPs*. Hexagonally packed, interdigitated PLLA helical microdomains in a PS matrix were directly visualized by electron tomography. The phase diagram of the PS-PLLA BCPs* was also established. Phase transitions from the H* phase to the stable cylinder and gyroid phases were found after long-time annealing, suggesting that the H* is a long-lived metastable phase. In contrast to racemic poly(styrene)-b-poly(d,l-lactide) BCPs, chiral interaction significantly enhances the incompatibility between achiral PS and chiral PLLA blocks in the PS-PLLA BCPs* and can be estimated through the determination of the interaction parameter.

  11. Folded supersymmetry with a twist

    NASA Astrophysics Data System (ADS)

    Cohen, Timothy; Craig, Nathaniel; Lou, Hou Keong; Pinner, David

    2016-03-01

    Folded supersymmetry ( f-SUSY) stabilizes the weak scale against radiative corrections from the top sector via scalar partners whose gauge quantum numbers differ from their Standard Model counterparts. This non-trivial pairing of states can be realized in extra-dimensional theories with appropriate supersymmetry-breaking boundary conditions. We present a class of calculable f-SUSY models that are parametrized by a non-trivial twist in 5D boundary conditions and can accommodate the observed Higgs mass and couplings. Although the distinctive phenomenology associated with the novel folded states should provide strong evidence for this mechanism, the most stringent constraints are currently placed by conventional supersymmetry searches. These models remain minimally fine-tuned in light of LHC8 data and provide a range of both standard and exotic signatures accessible at LHC13.

  12. Active vibration control of civil structures

    SciTech Connect

    Farrar, C.; Baker, W.; Fales, J.; Shevitz, D.

    1996-11-01

    This is a final report of a one year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Active vibration control (AVC) of structural and mechanical systems is one of the rapidly advancing areas of engineering research. The multifaceted nature of AVC covers many disciplines, such as sensors and instrumentation, numerical modeling, experimental mechanics, and advanced power systems. This work encompassed a review of the literature on active control of structures focusing both on active control hardware and on control algorithms, a design of an isolation systems using magneto-rheological fluid-filled (MRF) dampers and numerical simulations to study the enhanced vibration mitigation effects of this technology.

  13. Vector control activities: Fiscal Year, 1986

    SciTech Connect

    Not Available

    1987-04-01

    The program is divided into two major components - operations and support studies. The support studies are designed to improve the operational effectiveness and efficiency of the control program and to identify other vector control problems requiring TVA attention and study. Nonchemical methods of control are emphasized and are supplemented with chemical measures as needed. TVA also cooperates with various concerned municipalities in identifying blood-sucking arthropod pest problems and demonstrating control techniques useful in establishing abatement programs, and provides technical assistance to other TVA programs and organizations. The program also helps Land Between The Lakes (LBL) plan and conduct vector control operations and tick control research. Specific program control activities and support studies are discussed.

  14. CFD Modeling for Active Flow Control

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.

    2001-01-01

    This presentation describes current work under UEET Active Flow Control CFD Research Tool Development. The goal of this work is to develop computational tools for inlet active flow control design. This year s objectives were to perform CFD simulations of fully gridded vane vortex generators, micro-vortex genera- tors, and synthetic jets, and to compare flowfield results with wind tunnel tests of simple geometries with flow control devices. Comparisons are shown for a single micro-vortex generator on a flat plate, and for flow over an expansion ramp with sidewall effects. Vortex core location, pressure gradient and oil flow patterns are compared between experiment and computation. This work lays the groundwork for evaluating simplified modeling of arrays of devices, and provides the opportunity to test simple flow control device/sensor/ control loop interaction.

  15. Cable twisting due to atmospheric icing

    SciTech Connect

    McComber, P.; Druez, J.; Savadjiev, K.

    1995-12-31

    Samples of ice accretions collected on cables of overhead transmission lines have shown evidence of twisting of the cable during atmospheric icing. Previous work has attributed cable twisting to the torque created by the weight of an eccentric ice shape and by wind forces. However, testing of stranded cables and conductors has shown that such cables also twist when there is a change in tension in the cable span. This phenomenon is related to the interaction of the different strand layers under tension. When a cable is subjected to atmospheric icing, cable tension increases and this type of twisting should also be considered. In order to determine how the two types of twisting would compare on transmission lines, a numerical simulation was made using characteristics of a typical 35-mm stranded conductor. The twist angle was computed as a function of cable span, sag to span ratio and increasing ice loads. The simulation shows that for transmission lines, twisting due to varying tension will be significant. Since cable tension is influenced by wind speed and ambient temperature as well as ice load, this phenomenon, unless prevented, results in ice accretion more circular in shape and hence eventually in larger ice loads.

  16. Simulating Topological Defects in Twisted Fiber Bundles

    NASA Astrophysics Data System (ADS)

    Bruss, Isaac R.; Grason, Gregory M.

    2012-02-01

    Twisted bundles are a common motif found in naturally occurring structures of self-assembled fibers, such as collagen and fibrin. By understanding the general principles governing such organizations, new synthetic materials--from the nano to the macroscale--may also be realized. Recently, continuum elasticity theory has been applied to describe generic twisted fiber bundles. This has revealed a relation between a bundle's twist and the presence of topological defects in the cross-sectional packing of the fibers. Here we employ numerical simulations to examine this interdependence. We model a bundle's cross-section as beads confined to a plane. The interactions between beads is governed by a modified Lennard-Jones potential that accounts for the effects of twist. We observe configurations that range from perfect hexagonal packing for cases of no twist, to defect populated structures above a critical amount of twist. For small bundles of less than ˜100 beads, there exists a discrete spectrum of energy ground states corresponding to integer numbers of five-fold disclinations. For larger bundles, we hope to uncover what types of defect arrangements effectively screen the stresses caused by twist, and compare these to current predictions of the internal organization of collagen fibrils.

  17. DYNAMICS OF STRONGLY TWISTED RELATIVISTIC MAGNETOSPHERES

    SciTech Connect

    Parfrey, Kyle; Beloborodov, Andrei M.; Hui, Lam

    2013-09-10

    Magnetar magnetospheres are believed to be strongly twisted due to shearing of the stellar crust by internal magnetic stresses. We present time-dependent axisymmetric simulations showing in detail the evolution of relativistic force-free magnetospheres subjected to slow twisting through large angles. When the twist amplitude is small, the magnetosphere moves quasi-statically through a sequence of equilibria of increasing free energy. At some twist amplitude the magnetosphere becomes tearing-mode unstable to forming a resistive current sheet, initiating large-scale magnetic reconnection in which a significant fraction of the magnetic free energy can be dissipated. This ''critical'' twist angle is insensitive to the resistive length scale. Rapid shearing temporarily stabilizes the magnetosphere beyond the critical angle, allowing the magnetosphere of a rapidly differentially rotating star to store and dissipate more free energy. In addition to these effects, shearing the surface of a rotating star increases the spindown torque applied to the star. If shearing is much slower than rotation, the resulting spikes in spindown rate can occur on timescales anywhere from the long twisting timescale to the stellar spin period or shorter, depending both on the stellar shear distribution and the existing distribution of magnetospheric twists. A model in which energy is stored in the magnetosphere and released by a magnetospheric instability therefore predicts large changes in the measured spindown rate before soft gamma repeater giant flares.

  18. Active control of robot manipulator compliance

    NASA Technical Reports Server (NTRS)

    Nguyen, C. C.; Pooran, F. J.

    1986-01-01

    Work performed at Catholic University on the research grant entitled Active Control of Robot Manipulator Compliance, supported by NASA/Goddard space Flight Center during the period of May 15th, 1986 to November 15th, 1986 is described. The modelling of the two-degree-of-freedom robot is first presented. Then the complete system including the robot and the hybrid controller is simulated on an IBM-XT Personal Computer. Simulation results showed that proper adjustments of controller gains enable the robot to perform successful operations. Further research should focus on developing a guideline for the controller gain design to achieve system stability.

  19. Optimal control techniques for active noise suppression

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Keeling, S. L.; Silcox, R. J.

    1988-01-01

    Active suppression of noise in a bounded enclosure is considered within the framework of optimal control theory. A sinusoidal pressure field due to exterior offending noise sources is assumed to be known in a neighborhood of interior sensors. The pressure field due to interior controlling sources is assumed to be governed by a nonhomogeneous wave equation within the enclosure and by a special boundary condition designed to accommodate frequency-dependent reflection properties of the enclosure boundary. The form of the controlling sources is determined by considering the steady-state behavior of the system, and it is established that the control strategy proposed is stable and asymptotically optimal.

  20. An equilibrium double-twist model for the radial structure of collagen fibrils.

    PubMed

    Brown, Aidan I; Kreplak, Laurent; Rutenberg, Andrew D

    2014-11-14

    Mammalian tissues contain networks and ordered arrays of collagen fibrils originating from the periodic self-assembly of helical 300 nm long tropocollagen complexes. The fibril radius is typically between 25 to 250 nm, and tropocollagen at the surface appears to exhibit a characteristic twist-angle with respect to the fibril axis. Similar fibril radii and twist-angles at the surface are observed in vitro, suggesting that these features are controlled by a similar self-assembly process. In this work, we propose a physical mechanism of equilibrium radius control for collagen fibrils based on a radially varying double-twist alignment of tropocollagen within a collagen fibril. The free-energy of alignment is similar to that of liquid crystalline blue phases, and we employ an analytic Euler-Lagrange and numerical free energy minimization to determine the twist-angle between the molecular axis and the fibril axis along the radial direction. Competition between the different elastic energy components, together with a surface energy, determines the equilibrium radius and twist-angle at the fibril surface. A simplified model with a twist-angle that is linear with radius is a reasonable approximation in some parameter regimes, and explains a power-law dependence of radius and twist-angle at the surface as parameters are varied. Fibril radius and twist-angle at the surface corresponding to an equilibrium free-energy minimum are consistent with existing experimental measurements of collagen fibrils. Remarkably, in the experimental regime, all of our model parameters are important for controlling equilibrium structural parameters of collagen fibrils. PMID:25238208

  1. Active control of buckling of flexible beams

    NASA Technical Reports Server (NTRS)

    Baz, A.; Tampe, L.

    1989-01-01

    The feasibility of using the rapidly growing technology of the shape memory alloys actuators in actively controlling the buckling of large flexible structures is investigated. The need for such buckling control systems is becoming inevitable as the design trends of large space structures have resulted in the use of structural members that are long, slender, and very flexible. In addition, as these truss members are subjected mainly to longitudinal loading they become susceptible to structural instabilities due to buckling. Proper control of such instabilities is essential to the effective performance of the structures as stable platforms for communication and observation. Mathematical models are presented that simulate the dynamic characteristics of the shape memory actuator, the compressive structural members, and the associated active control system. A closed-loop computer-controlled system is designed, based on the developed mathematical models, and implemented to control the buckling of simple beams. The performance of the computer-controlled system is evaluated experimentally and compared with the theoretical predictions to validate the developed models. The obtained results emphasize the importance of buckling control and suggest the potential of the shape memory actuators as attractive means for controlling structural deformation in a simple and reliable way.

  2. Rotor Flapping Response to Active Control

    NASA Technical Reports Server (NTRS)

    Nguyen, Khanh; Johnson, Wayne

    2004-01-01

    Rotor active control using higher harmonic blade pitch has been proposed as a means to reduce both rotor radiated noise and airframe vibration and to enhance rotor performance. The higher harmonic input, however, can affect rotor thrust and cyclic flapping - the basic trim characteristics of the rotor. Some of the trim changes can negate the active control benefits. For example, wind tunnel test results of a full scale BO-105 rotor with individual-blade control indicate some rotor performance improvements, accompanied with changes in rotor trim, using two-per-rev blade pitch input. The observed performance benefits could therefore be a simple manifestation of the trim change rather than an efficient redistribution of the rotor airloads. More recently, the flight test of the BO-105 helicopter equip,ped with individual-blade-control actuators also reported trim changes whenever the two-per-rev blade pitch for noise reduction was activated. The pilot had to adjust the trim control to maintain the aircraft under a constant flight path. These two cases highlight the, importance of trim considerations in the application of active control to rotorcraft.

  3. Nanomechanical Energy Storage in Twisted Nanotube Ropes

    NASA Astrophysics Data System (ADS)

    Teich, David; Fthenakis, Zacharias G.; Seifert, Gotthard; Tománek, David

    2012-12-01

    We determine the deformation energetics and energy density of twisted carbon nanotubes and nanotube ropes that effectively constitute a torsional spring. Using ab initio and parametrized density functional calculations, we identify structural changes in these systems and determine their elastic limits. The deformation energy of twisted nanotube ropes contains contributions associated not only with twisting but also with stretching, bending, and compression of individual nanotubes. We quantify these energy contributions and show that their relative role changes with the number of nanotubes in the rope.

  4. Twisted spectral geometry for the standard model

    NASA Astrophysics Data System (ADS)

    Martinetti, Pierre

    2015-07-01

    In noncommutative geometry, the spectral triple of a manifold does not generate bosonic fields, for fluctuations of the Dirac operator vanish. A Connes-Moscovici twist forces the commutative algebra to be multiplied by matrices. Keeping the space of spinors untouched, twisted-fluctuations then yield perturbations of the spin connection. Applied to the spectral triple of the Standard Model, a similar twist yields the scalar field needed to stabilize the vacuum and to make the computation of the Higgs mass compatible with its experimental value.

  5. [Inactivation of failsafe programs by Twist oncoproteins and tumor progression].

    PubMed

    Puisieux, A

    2008-01-01

    Multicellular organisms have developed innate defense mechanisms to prevent the expansion of abnormal cells with significant proliferative potential. The two major safeguard mechanisms are premature senescence, which is characterized by definitive cell cycle arrest, and apoptosis, the most common form of programmed cell death. In normal and premalignant cells, the control of these processes is coupled to the regulation of cell proliferation, mainly through the p16 (Ink4A) -Rb and ARF-p53 intracellular signaling pathways. Hence, in benign tumors, aberrant mitogenic activity is counterbalanced by the induction of these oncosuppressive pathways, leading to either apoptosis or senescence which both limit tumor outgrowth. Progression towards malignant and potentially metastatic tumors requires the inhibition of these failsafe programs. Based on our work on Twist oncoproteins, we propose a presentation of recent data on cellular mechanisms by which cancer cells override the surveillance machinery and escape senescence and apoptosis, and we will describe the biological impact of this process on tumor metastasis. PMID:19061727

  6. Twisted Gastrulation, a BMP Antagonist, Exacerbates Podocyte Injury

    PubMed Central

    Yamada, Sachiko; Nakamura, Jin; Asada, Misako; Takase, Masayuki; Matsusaka, Taiji; Iguchi, Taku; Yamada, Ryo; Tanaka, Mari; Higashi, Atsuko Y.; Okuda, Tomohiko; Asada, Nariaki; Fukatsu, Atsushi; Kawachi, Hiroshi; Graf, Daniel; Muso, Eri; Kita, Toru; Kimura, Takeshi; Pastan, Ira; Economides, Aris N.; Yanagita, Motoko

    2014-01-01

    Podocyte injury is the first step in the progression of glomerulosclerosis. Previous studies have demonstrated the beneficial effect of bone morphogenetic protein 7 (Bmp7) in podocyte injury and the existence of native Bmp signaling in podocytes. Local activity of Bmp7 is controlled by cell-type specific Bmp antagonists, which inhibit the binding of Bmp7 to its receptors. Here we show that the product of Twisted gastrulation (Twsg1), a Bmp antagonist, is the central negative regulator of Bmp function in podocytes and that Twsg1 null mice are resistant to podocyte injury. Twsg1 was the most abundant Bmp antagonist in murine cultured podocytes. The administration of Bmp induced podocyte differentiation through Smad signaling, whereas the simultaneous administration of Twsg1 antagonized the effect. The administration of Bmp also inhibited podocyte proliferation, whereas simultaneous administration of Twsg1 antagonized the effect. Twsg1 was expressed in the glomerular parietal cells (PECs) and distal nephron of the healthy kidney, and additionally in damaged glomerular cells in a murine model of podocyte injury. Twsg1 null mice exhibited milder hypoalbuminemia and hyperlipidemia, and milder histological changes while maintaining the expression of podocyte markers during podocyte injury model. Taken together, our results show that Twsg1 plays a critical role in the modulation of protective action of Bmp7 on podocytes, and that inhibition of Twsg1 is a promising means of development of novel treatment for podocyte injury. PMID:24586548

  7. Actively controlled shaft seals for aerospace applications

    NASA Technical Reports Server (NTRS)

    Salant, Richard F.

    1994-01-01

    This study experimentally investigates an actively controlled mechanical seal for aerospace applications. The seal of interest is a gas seal, which is considerably more compact than previous actively controlled mechanical seals that were developed for industrial use. In a mechanical seal, the radial convergence of the seal interface has a primary effect on the film thickness. Active control of the film thickness is established by controlling the radial convergence of the seal interface with piezoelectric actuator. An actively controlled mechanical seal was initially designed and evaluated using a mathematical model. Based on these results, a seal was fabricated and tested under laboratory conditions. The seal was tested with both helium and air, at rotational speeds up to 3770 rad/sec, and at sealed pressures as high as 1.48 x 10(exp 6) Pa. The seal was operated with both manual control and with a closed-loop control system that used either the leakage rate or face temperature as the feedback. The output of the controller was the voltage applied to the piezoelectric actuator. The seal operated successfully for both short term tests (less than one hour) and for longer term tests (four hours) with a closed-loop control system. The leakage rates were typically 5-15 slm (standard liters per minute), and the face temperatures were generally maintained below 100 C. When leakage rate was used as the feedback signal, the setpoint leakage rate was typically maintained within 1 slm. However, larger deviations occurred during sudden changes in sealed pressure. When face temperature was used as the feedback signal, the setpoint face temperature was generally maintained within 3 C, with larger deviations occurring when the sealed pressure changed suddenly.

  8. Vector control activities. Fiscal year, 1982

    SciTech Connect

    Pickard, E.; Cooney, J.C.; McDuff, B.R.

    1983-06-01

    The goal of the TVA Vector Control Program is to protect the public from potential vectors of disease by controlling medically-important arthropod pests that are propagated on TVA lands or waters. In addition, freedom from annoying mosquitoes and other blood-sucking pests permits the development, use, and full enjoyment of the vast recreational opportunities offered by the many miles of freshwater lakes. To attain this goal the program is divided into operations and support studies. The support studies are designed to improve the operational effectiveness and efficiency of the control program and to identify other vector control problems that require TVA attention and study. Specifically, activities concerning water level management of TVA lakes, dewatering projects, plant growth control, drainage and insect control programs are detailed. Further, report is made of post-impoundment surveys, soil sampling studies of Mosquite larvae and ecological mosquito management studies.

  9. A Significantly Twisted Spirocyclic Phosphine Oxide as a Universal Host for High-Efficiency Full-Color Thermally Activated Delayed Fluorescence Diodes.

    PubMed

    Li, Jing; Ding, Dongxue; Tao, Youtian; Wei, Ying; Chen, Runfeng; Xie, Linghai; Huang, Wei; Xu, Hui

    2016-04-01

    A universal thermally activated delayed fluorescence (TADF) host, 4'-diphenylphosphinoylspiro[fluorene-9,9'-xanthene] (SFXSPO), is constructed with a highly distorted and asymmetric configuration and disordered molecular packing in its solid state. SFXSPO successfully endows its full-color TADF diodes with state-of-the-art performance, e.g., the record external quantum efficiency of 22.5% and 19.1% and internal quantum efficiency of ≈100% for its yellow TADF diodes and single-host full-TADF nearly-white-emitting devices, respectively. PMID:26923460

  10. Twist1 Is Essential for Tooth Morphogenesis and Odontoblast Differentiation.

    PubMed

    Meng, Tian; Huang, Yanyu; Wang, Suzhen; Zhang, Hua; Dechow, Paul C; Wang, Xiaofang; Qin, Chunlin; Shi, Bing; D'Souza, Rena N; Lu, Yongbo

    2015-12-01

    Twist1 is a basic helix-loop-helix-containing transcription factor that is expressed in the dental mesenchyme during the early stages of tooth development. To better delineate its roles in tooth development, we generated Twist1 conditional knockout embryos (Twist2(Cre) (/+);Twist1(fl/fl)) by breeding Twist1 floxed mice (Twist1(fl/fl)) with Twist2-Cre recombinase knockin mice (Twist2(Cre) (/+)). The Twist2(Cre) (/+);Twist1(fl/fl) embryos formed smaller tooth germs and abnormal cusps during early tooth morphogenesis. Molecular and histological analyses showed that the developing molars of the Twist2(Cre) (/+);Twist1(fl/fl) embryos had reduced cell proliferation and expression of fibroblast growth factors 3, 4, 9, and 10 and FGF receptors 1 and 2 in the dental epithelium and mesenchyme. In addition, 3-week-old renal capsular transplants of embryonic day 18.5 Twist2(Cre) (/+);Twist1(fl/fl) molars showed malformed crowns and cusps with defective crown dentin and enamel. Immunohistochemical analyses revealed that the implanted mutant molars had defects in odontoblast differentiation and delayed ameloblast differentiation. Furthermore, in vitro ChIP assays demonstrated that Twist1 was able to bind to a specific region of the Fgf10 promoter. In conclusion, our findings suggest that Twist1 plays crucial roles in regulating tooth development and that it may exert its functions through the FGF signaling pathway. PMID:26487719

  11. Actively Controlling Buffet-Induced Excitations

    NASA Technical Reports Server (NTRS)

    Moses, Robert W.; Pototzky, Anthony S.; Henderson, Douglas A.; Galea, Stephen C.; Manokaran, Donald S.; Zimcik, David G.; Wickramasinghe, Viresh; Pitt, Dale M.; Gamble, Michael A.

    2005-01-01

    High performance aircraft, especially those with twin vertical tails, encounter unsteady buffet loads when flying at high angles of attack. These loads result in significant random stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. An international collaborative research activity among Australia, Canada and the United States, conducted under the auspices of The Technical Cooperation Program (TTCP) contributed resources toward a program that coalesced a broad range of technical knowledge and expertise into a single investigation to demonstrate the enhanced performance and capability of the advanced active BLA control system in preparation for a flight test demonstration. The research team investigated the use of active structural control to alleviate the damaging structural response to these loads by applying advanced directional piezoelectric actuators, the aircraft rudder, switch mode amplifiers, and advanced control strategies on an F/A-18 aircraft empennage. Some results of the full-scale investigation are presented herein.

  12. Rolling Maneuver Load Alleviation using active controls

    NASA Technical Reports Server (NTRS)

    Woods-Vedeler, Jessica A.; Pototzky, Anthony S.

    1992-01-01

    Rolling Maneuver Load Alleviation (RMLA) has been demonstrated on the Active Flexible Wing (AFW) wind tunnel model in the NASA Langley Transonic Dynamics Tunnel. The design objective was to develop a systematic approach for developing active control laws to alleviate wing incremental loads during roll maneuvers. Using linear load models for the AFW wind-tunnel model which were based on experimental measurements, two RMLA control laws were developed based on a single-degree-of-freedom roll model. The RMLA control laws utilized actuation of outboard control surface pairs to counteract incremental loads generated during rolling maneuvers and actuation of the trailing edge inboard control surface pairs to maintain roll performance. To evaluate the RMLA control laws, roll maneuvers were performed in the wind tunnel at dynamic pressures of 150, 200, and 250 psf and Mach numbers of 0.33, .38 and .44, respectively. Loads obtained during these maneuvers were compared to baseline maneuver loads. For both RMLA controllers, the incremental torsion moments were reduced by up to 60 percent at all dynamic pressures and performance times. Results for bending moment load reductions during roll maneuvers varied. In addition, in a multiple function test, RMLA and flutter suppression system control laws were operated simultaneously during roll maneuvers at dynamic pressures 11 percent above the open-loop flutter dynamic pressure.

  13. Feedback controllers for broadband active noise reduction

    NASA Astrophysics Data System (ADS)

    Petitjean, Benoit; Legrain, Isabelle

    1994-09-01

    The aim of the present paper is to demonstrate the efficiency of an LQG-based controller for the active control of the acoustic field radiated by a rectangular panel. This topic has been of interest for numerous researchers in the past 10 or 15 years, but very little attention has been paid to broadband disturbances occurring in a relatively high frequency range. These are unfortunately common features of noise perturbations in realistic structures such as airplanes or helicopters. The few articles that deal with this problem provide very scarce experimental results and are related to frequency bands where the structure dynamics is rather poor. From the outset, the problem at hand involves numerous difficulties, such as the modeling of the active structure itself and the possible large size of the controller. In the following, the experimental setup is described, then the controller design procedure is developed and finally some experimental results are shown that prove the efficiency of the method.

  14. Simultaneous investigation of magnetoresistance (MR) and twisted angle of twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Hong, Sung Ju; Manzo, Julio; Kim, Kyung Ho; Park, Min; Baek, Seung Jae; Kholin, Dmitry; Lee, Min Woo; Choi, Eun Sang; Jeong, Dae Hong; Yurgens, August; Drndic, Maria; Johnson, Alan; Park, Yung Woo

    2013-03-01

    We have measured magnetoresistance (MR) and twisted angle of twisted bilayer graphene, simultaneously. Twisted angle was measured by transmission electron microscopy (TEM) diffraction experiment on SiNx substrate. We performed Raman spectroscopy experiment and observed enhanced G mode which results from double resonance scattering process near van Hove singularity (vHs). MR shows superposition of two Shubnikov de Haas (SdH) oscillations and is analyzed by Landau fan diagram.

  15. Active Flow Control Stator With Coanda Surface

    NASA Technical Reports Server (NTRS)

    Guendogdu; Vorreiter; Seume

    2010-01-01

    Active Flow Control increases the permissible aerodynamic loading. Curved surface near the trailing edge ("Coanda surface"): a) increases turning -> higher pressure ratio. b) controls boundary layer separation -> increased surge margin. Objective: Reduce the number of vanes or compressor stages. Constraints: 1. In a real compressor, the vane must still function entirely without blowing. 2. Maintain the flow exit angle of the reference stator despite the resulting increase in stator loading.

  16. Mathematical Modeling of Yarn Dynamics in a Generalized Twisting System

    PubMed Central

    Yin, R.; Tao, X. M.; Xu, B. G.

    2016-01-01

    Twisting is an important process to form a continuous yarn from short fibres and to determine the structure and properties of the resultant yarn. This paper proposes a new theoretical model of yarn dynamics in a generalized twisting system, which deals with two important phenomena simultaneously, that is, twist generation and twist propagation. Equations of yarn motion are established and the boundary value problems are numerically solved by Newton-Raphson method. The simulation results are validated by experiments and a good agreement has been demonstrated for the system with a moving rigid cylinder as the twisting element. For the first time, influences of several parameters on the twisting process have been revealed in terms of twist efficiency of the moving rigid cylinder, propagation coefficients of twist trapping and congestion. It was found that the wrap angle and yarn tension have large influence on the twisting process, and the yarn torsional rigidity varies with the twisting parameters. PMID:27079187

  17. Mathematical Modeling of Yarn Dynamics in a Generalized Twisting System

    NASA Astrophysics Data System (ADS)

    Yin, R.; Tao, X. M.; Xu, B. G.

    2016-04-01

    Twisting is an important process to form a continuous yarn from short fibres and to determine the structure and properties of the resultant yarn. This paper proposes a new theoretical model of yarn dynamics in a generalized twisting system, which deals with two important phenomena simultaneously, that is, twist generation and twist propagation. Equations of yarn motion are established and the boundary value problems are numerically solved by Newton-Raphson method. The simulation results are validated by experiments and a good agreement has been demonstrated for the system with a moving rigid cylinder as the twisting element. For the first time, influences of several parameters on the twisting process have been revealed in terms of twist efficiency of the moving rigid cylinder, propagation coefficients of twist trapping and congestion. It was found that the wrap angle and yarn tension have large influence on the twisting process, and the yarn torsional rigidity varies with the twisting parameters.

  18. Mathematical Modeling of Yarn Dynamics in a Generalized Twisting System.

    PubMed

    Yin, R; Tao, X M; Xu, B G

    2016-01-01

    Twisting is an important process to form a continuous yarn from short fibres and to determine the structure and properties of the resultant yarn. This paper proposes a new theoretical model of yarn dynamics in a generalized twisting system, which deals with two important phenomena simultaneously, that is, twist generation and twist propagation. Equations of yarn motion are established and the boundary value problems are numerically solved by Newton-Raphson method. The simulation results are validated by experiments and a good agreement has been demonstrated for the system with a moving rigid cylinder as the twisting element. For the first time, influences of several parameters on the twisting process have been revealed in terms of twist efficiency of the moving rigid cylinder, propagation coefficients of twist trapping and congestion. It was found that the wrap angle and yarn tension have large influence on the twisting process, and the yarn torsional rigidity varies with the twisting parameters. PMID:27079187

  19. Twist promotes reprogramming of glucose metabolism in breast cancer cells through PI3K/AKT and p53 signaling pathways.

    PubMed

    Yang, Li; Hou, Yixuan; Yuan, Jie; Tang, Shifu; Zhang, Hailong; Zhu, Qing; Du, Yan-e; Zhou, Mingli; Wen, Siyang; Xu, Liyun; Tang, Xi; Cui, Xiaojiang; Liu, Manran

    2015-09-22

    Twist, a key regulator of epithelial-mesenchymal transition (EMT), plays an important role in the development of a tumorigenic phenotype. Energy metabolism reprogramming (EMR), a newly discovered hallmark of cancer cells, potentiates cancer cell proliferation, survival, and invasion. Currently little is known about the effects of Twist on tumor EMR. In this study, we found that glucose consumption and lactate production were increased and mitochondrial mass was decreased in Twist-overexpressing MCF10A mammary epithelial cells compared with vector-expressing MCF10A cells. Moreover, these Twist-induced phenotypic changes were augmented by hypoxia. The expression of some glucose metabolism-related genes such as PKM2, LDHA, and G6PD was also found to be upregulated. Mechanistically, activated β1-integrin/FAK/PI3K/AKT/mTOR and suppressed P53 signaling were responsible for the observed EMR. Knockdown of Twist reversed the effects of Twist on EMR in Twist-overexpressing MCF10A cells and Twist-positive breast cancer cells. Furthermore, blockage of the β1-integrin/FAK/PI3K/AKT/mTOR pathway by siRNA or specific chemical inhibitors, or rescue of p53 activation can partially reverse the switch of glucose metabolism and inhibit the migration of Twist-overexpressing MCF10A cells and Twist-positive breast cancer cells. Thus, our data suggest that Twist promotes reprogramming of glucose metabolism in MCF10A-Twist cells and Twist-positive breast cancer cells via activation of the β1-integrin/FAK/PI3K/AKT/mTOR pathway and inhibition of the p53 pathway. Our study provides new insight into EMR. PMID:26342198

  20. Active Vibration Control For Lasers And Spacecraft

    NASA Astrophysics Data System (ADS)

    Pearson, Jerome

    1983-12-01

    The Active Control of Space Structures (ACOSS) program of the Defense Advanced Research Projects Agency has identified problems in active vibration control of structural modes in extremely flexible space structures and in precisely pointed optics. The Air Force Wright Aeronautical Laboratories programs are an outgrowth of the ACOSS program. They are aimed at the problems of sensors, actuators, and their dynamic interactions with the structure to be controlled, and at the problem of system identification by one-g laboratory experiments. The VCOSS-1 and VCOSS-2 programs (Vibration Control of Space Structures) address the dynamic interactions of the sensor-actuator-structure; the Benchless Laser program and the Airborne Laser Mirror-Control program address the active control of HEL mirrors; the Experimental Modal Analysis and Component Synthesis and the Large Space Structure Dynamics programs address the problems of system identification and testing. Closer coordination with NASA and DARPA is being sought in support of on-orbit dynamic testing using the Space Shuttle and in the development of a national facility for one-g dynamics testing of large space structures.

  1. Active disturbance rejection controller for chemical reactor

    SciTech Connect

    Both, Roxana; Dulf, Eva H.; Muresan, Cristina I.

    2015-03-10

    In the petrochemical industry, the synthesis of 2 ethyl-hexanol-oxo-alcohols (plasticizers alcohol) is of high importance, being achieved through hydrogenation of 2 ethyl-hexenal inside catalytic trickle bed three-phase reactors. For this type of processes the use of advanced control strategies is suitable due to their nonlinear behavior and extreme sensitivity to load changes and other disturbances. Due to the complexity of the mathematical model an approach was to use a simple linear model of the process in combination with an advanced control algorithm which takes into account the model uncertainties, the disturbances and command signal limitations like robust control. However the resulting controller is complex, involving cost effective hardware. This paper proposes a simple integer-order control scheme using a linear model of the process, based on active disturbance rejection method. By treating the model dynamics as a common disturbance and actively rejecting it, active disturbance rejection control (ADRC) can achieve the desired response. Simulation results are provided to demonstrate the effectiveness of the proposed method.

  2. Active Control of Cryogenic Propellants in Space

    NASA Technical Reports Server (NTRS)

    Notardonato, William

    2011-01-01

    A new era of space exploration is being planned. Exploration architectures under consideration require the long term storage of cryogenic propellants in space. This requires development of active control systems to mitigate the effect of heat leak. This work summarizes current state of the art, proposes operational design strategies and presents options for future architectures. Scaling and integration of active systems will be estimated. Ideal long range spacecraft systems will be proposed with Exploration architecture benefits considered.

  3. Seismic active control by neural networks.

    SciTech Connect

    Tang, Y.

    1998-01-01

    A study on the application of artificial neural networks (ANNs) to activate structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feed-forward neural network architecture and an adaptive back-propagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the back-propagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator's capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  4. Seismic active control by neutral networks

    SciTech Connect

    Tang, Yu

    1995-12-31

    A study on the application of artificial neural networks (ANNs) to active structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feedforward neural network architecture and an adaptive backpropagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the backpropagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator`s capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  5. Akirin Links Twist-Regulated Transcription with the Brahma Chromatin Remodeling Complex during Embryogenesis

    PubMed Central

    Nowak, Scott J.; Aihara, Hitoshi; Gonzalez, Katie; Nibu, Yutaka; Baylies, Mary K.

    2012-01-01

    The activities of developmentally critical transcription factors are regulated via interactions with cofactors. Such interactions influence transcription factor activity either directly through protein–protein interactions or indirectly by altering the local chromatin environment. Using a yeast double-interaction screen, we identified a highly conserved nuclear protein, Akirin, as a novel cofactor of the key Drosophila melanogaster mesoderm and muscle transcription factor Twist. We find that Akirin interacts genetically and physically with Twist to facilitate expression of some, but not all, Twist-regulated genes during embryonic myogenesis. akirin mutant embryos have muscle defects consistent with altered regulation of a subset of Twist-regulated genes. To regulate transcription, Akirin colocalizes and genetically interacts with subunits of the Brahma SWI/SNF-class chromatin remodeling complex. Our results suggest that, mechanistically, Akirin mediates a novel connection between Twist and a chromatin remodeling complex to facilitate changes in the chromatin environment, leading to the optimal expression of some Twist-regulated genes during Drosophila myogenesis. We propose that this Akirin-mediated link between transcription factors and the Brahma complex represents a novel paradigm for providing tissue and target specificity for transcription factor interactions with the chromatin remodeling machinery. PMID:22396663

  6. Akirin links twist-regulated transcription with the Brahma chromatin remodeling complex during embryogenesis.

    PubMed

    Nowak, Scott J; Aihara, Hitoshi; Gonzalez, Katie; Nibu, Yutaka; Baylies, Mary K

    2012-01-01

    The activities of developmentally critical transcription factors are regulated via interactions with cofactors. Such interactions influence transcription factor activity either directly through protein-protein interactions or indirectly by altering the local chromatin environment. Using a yeast double-interaction screen, we identified a highly conserved nuclear protein, Akirin, as a novel cofactor of the key Drosophila melanogaster mesoderm and muscle transcription factor Twist. We find that Akirin interacts genetically and physically with Twist to facilitate expression of some, but not all, Twist-regulated genes during embryonic myogenesis. akirin mutant embryos have muscle defects consistent with altered regulation of a subset of Twist-regulated genes. To regulate transcription, Akirin colocalizes and genetically interacts with subunits of the Brahma SWI/SNF-class chromatin remodeling complex. Our results suggest that, mechanistically, Akirin mediates a novel connection between Twist and a chromatin remodeling complex to facilitate changes in the chromatin environment, leading to the optimal expression of some Twist-regulated genes during Drosophila myogenesis. We propose that this Akirin-mediated link between transcription factors and the Brahma complex represents a novel paradigm for providing tissue and target specificity for transcription factor interactions with the chromatin remodeling machinery. PMID:22396663

  7. Deformed and twisted black holes with NUTs

    NASA Astrophysics Data System (ADS)

    Krtouš, Pavel; Kubizňák, David; Frolov, Valeri P.; Kolář, Ivan

    2016-06-01

    We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by ‘unspinning’ the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of a deformed and/or twisted sphere, with the deformation and twist characterized by the ‘Euclidean NUT’ parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.

  8. New twisted intermetallic compound superconductor: A concept

    NASA Technical Reports Server (NTRS)

    Coles, W. D.; Brown, G. V.; Laurence, J. C.

    1972-01-01

    Method for processing Nb3Sn and other intermetallic compound superconductors produces a twisted, stabilized wire or tube which can be used to wind electromagnetics, armatures, rotors, and field windings for motors and generators as well as other magnetic devices.

  9. Theory of twisted nonuniformly heated bars

    NASA Technical Reports Server (NTRS)

    Shorr, B. F.

    1980-01-01

    Nonlineary distributed stresses in twisted nonuniformly heated bars of arbitrary cross section are calculated taking into account various elasticity parameters. The approximate theory is shown to be sufficiently general and accurate by comparison with experimental data.

  10. A smart soft actuator using a single shape memory alloy for twisting actuation

    NASA Astrophysics Data System (ADS)

    Shim, Jae-Eul; Quan, Ying-Jun; Wang, Wei; Rodrigue, Hugo; Song, Sung-Hyuk; Ahn, Sung-Hoon

    2015-12-01

    Recently, robots have become a topic of interest with regard to their functionality as they need to complete a large number of diverse tasks in a variety of environments. When using traditional mechanical components, many parts are needed to realize complex deformations, such as motors, hinges, and cranks. To produce complex deformations, this work introduces a smart soft composite torsional actuator using a single shape memory alloy (SMA) wire without any additional elements. The proposed twisting actuator is composed of a torsionally prestrained SMA wire embedded at the center of a polydimethylsiloxane matrix that twists by applying an electric current upon joule heating of the SMA wire. This report shows the actuator design, fabrication method, and results for the twisting angle and actuation moment. Results show that a higher electric current helps reach the maximum twisting angle faster, but that if the current is too low or too high, it will not be able to reach its maximum deformation. Also, both the twisting angle and the twisting moment increase with a large applied twisting prestrain, but this increase has an asymptotic behavior. However, results for both the width and the thickness of the actuator show that a larger width and thickness reduce the maximum actuation angle of the actuator. This paper also presents a new mechanism for an SMA-actuated active catheter using only two SMA wires with a total length of 170 mm to bend the tip of the catheter in multiple directions. The fabricated active catheter’s maximum twisting angle is 270°, and the maximum bending curvature is 0.02 mm-1.

  11. Digitally controlling the 'twist' of light

    NASA Astrophysics Data System (ADS)

    Dudley, A.; Forbes, A.

    2014-08-01

    An overview of the work done within the Mathematical Optics group at the CSIR's National Laser Centre will be presented. We will focus on our work done in laser beam shaping with the use of digital holograms for the generation of superimposed optical fields which carry orbital angular momentum (OAM) and the development of OAM measurement techniques. Since OAM offers a potentially infinite-dimensional state space, much interest has been generated in its measurement for higher-dimensional quantum information processing to be realised. We generate superpositions of higher-order Bessel beams and show that even though we can create a field which carries no overall OAM, we can still witness an angular rotation in the intensity profile of the beam. We also develop a new OAM measurement technique by means of digital holograms.

  12. Rolling maneuver load alleviation using active controls

    NASA Technical Reports Server (NTRS)

    Woods-Vedeler, Jessica A.; Pototzky, Anthony S.

    1992-01-01

    Rolling Maneuver Load Alleviation (RMLA) was demonstrated on the Active Flexible Wing (AFW) wind tunnel model in the LaRC Transonic Dynamics Tunnel. The design objective was to develop a systematic approach for developing active control laws to alleviate wing incremental loads during roll maneuvers. Using linear load models for the AFW wind-tunnel model which were based on experimental measurements, two RMLA control laws were developed based on a single-degree-of-freedom roll model. The RMLA control laws utilized actuation of outboard control surface pairs to counteract incremental loads generated during rolling maneuvers and roll performance. To evaluate the RMLA control laws, roll maneuvers were performed in the wind tunnel at dynamic pressures of 150, 200, and 250 psf and Mach numbers of .33, .38, and .44, respectively. Loads obtained during these maneuvers were compared to baseline maneuver loads. For both RMLA controllers, the incremental torsion moments were reduced by up to 60 percent at all dynamic pressures and performance times. Results for bending moment load reductions during roll maneuvers varied. In addition, in a multiple function test, RMLA and flutter suppression system control laws were operated simultaneously during roll maneuvers at dynamic pressures 11 percent above the open-loop flutter dynamic pressure.

  13. Dielectric elastomers for active vibration control applications

    NASA Astrophysics Data System (ADS)

    Herold, S.; Kaal, W.; Melz, T.

    2011-04-01

    Dielectric elastomers (DE) have proved to have high potential for smart actuator applications in many laboratory setups and also in first commercially available components. Because of their large deformation capability and the inherent fast response to external stimulation they proffer themselves to applications in the field of active vibration control, especially for lightweight structures. These structures typically tend to vibrate with large amplitudes even at low excitation forces. Here, DE actuators seem to be ideal components for setting up control loops to suppress unwanted vibrations. Due to the underlying physical effect DE actuators are generally non-linear elements with an approximately quadratic relationship between in- and output. Consequently, they automatically produce higher-order frequencies. This can cause harmful effects for vibration control on structures with high modal density. Therefore, a linearization technique is required to minimize parasitic effects. This paper shows and quantifies the nonlinearity of a commercial DE actuator and demonstrates the negative effects it can have in technical applications. For this purpose, two linearization methods are developed. Subsequently, the actuator is used to implement active vibration control for two different mechanical systems. In the first case a concentrated mass is driven with the controlled actuator resulting in a tunable oscillator. In the second case a more complex mechanical structure with multiple resonances is used. Different control approaches are applied likewise and their impact on the whole system is demonstrated. Thus, the potential of DE actuators for vibration control applications is highlighted.

  14. Piezoelectric Power Requirements for Active Vibration Control

    NASA Technical Reports Server (NTRS)

    Brennan, Matthew C.; McGowan, Anna-Maria Rivas

    1997-01-01

    This paper presents a method for predicting the power consumption of piezoelectric actuators utilized for active vibration control. Analytical developments and experimental tests show that the maximum power required to control a structure using surface-bonded piezoelectric actuators is independent of the dynamics between the piezoelectric actuator and the host structure. The results demonstrate that for a perfectly-controlled system, the power consumption is a function of the quantity and type of piezoelectric actuators and the voltage and frequency of the control law output signal. Furthermore, as control effectiveness decreases, the power consumption of the piezoelectric actuators decreases. In addition, experimental results revealed a non-linear behavior in the material properties of piezoelectric actuators. The material non- linearity displayed a significant increase in capacitance with an increase in excitation voltage. Tests show that if the non-linearity of the capacitance was accounted for, a conservative estimate of the power can easily be determined.

  15. A Dynamic Absorber With Active Vibration Control

    NASA Astrophysics Data System (ADS)

    Huang, S.-J.; Lian, R.-J.

    1994-12-01

    The design and construction of a dynamic absorber incorporating active vibration control is described. The absorber is a two-degrees-of-freedom spring — lumped mass system sliding on a guide pillar, with two internal vibration disturbance sources. Both the main mass and the secondary absorber mass are acted on by DC servo motors, respectively, to suppress the vibration amplitude. The state variable technique is used to model this dynamic system and a decoupling PID control method is used. First, the discrete time state space model is identified by using the commercial software MATLAB. Then the decoupling controller of this multi-input/multi-output system is derived from the identified model. Finally the results of some experiments are presented. The experimental results show that the system is effective in suppressing vibration. Also, the performance of this control strategy for position tracking control is evaluated based on experimental data.

  16. Neural predictive control for active buffet alleviation

    NASA Astrophysics Data System (ADS)

    Pado, Lawrence E.; Lichtenwalner, Peter F.; Liguore, Salvatore L.; Drouin, Donald

    1998-06-01

    The adaptive neural control of aeroelastic response (ANCAR) and the affordable loads and dynamics independent research and development (IRAD) programs at the Boeing Company jointly examined using neural network based active control technology for alleviating undesirable vibration and aeroelastic response in a scale model aircraft vertical tail. The potential benefits of adaptive control includes reducing aeroelastic response associated with buffet and atmospheric turbulence, increasing flutter margins, and reducing response associated with nonlinear phenomenon like limit cycle oscillations. By reducing vibration levels and thus loads, aircraft structures can have lower acquisition cost, reduced maintenance, and extended lifetimes. Wind tunnel tests were undertaken on a rigid 15% scale aircraft in Boeing's mini-speed wind tunnel, which is used for testing at very low air speeds up to 80 mph. The model included a dynamically scaled flexible fail consisting of an aluminum spar with balsa wood cross sections with a hydraulically powered rudder. Neural predictive control was used to actuate the vertical tail rudder in response to strain gauge feedback to alleviate buffeting effects. First mode RMS strain reduction of 50% was achieved. The neural predictive control system was developed and implemented by the Boeing Company to provide an intelligent, adaptive control architecture for smart structures applications with automated synthesis, self-optimization, real-time adaptation, nonlinear control, and fault tolerance capabilities. It is designed to solve complex control problems though a process of automated synthesis, eliminating costly control design and surpassing it in many instances by accounting for real world non-linearities.

  17. Actively Controlled Shaft Seals for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Salant, Richard F.; Wolff, Paul

    1995-01-01

    This study experimentally investigates an actively controlled mechanical seal for aerospace applications. The seal of interest is a gas seal, which is considerably more compact than previous actively controlled mechanical seals that were developed for industrial use. In a mechanical seal, the radial convergence of the seal interface has a primary effect on the film thickness. Active control of the film thickness is established by controlling the radial convergence of the seal interface with a piezoelectric actuator. An actively controlled mechanical seal was initially designed and evaluated using a mathematical model. Based on these results, a seal was fabricated and tested under laboratory conditions. The seal was tested with both helium and air, at rotational speeds up to 3770 rad/sec, and at sealed pressures as high as 1.48 x 10(exp 6) Pa. The seal was operated with both manual control and with a closed-loop control system that used either the leakage rate or face temperature as the feedback. The output of the controller was the voltage applied to the piezoelectric actuator. The seal operated successfully for both short term tests (less than one hour) and for longer term tests (four hours) with a closed-loop control system. The leakage rates were typically 5-15 slm (standard liters per minute), and the face temperatures were generally maintained below 100C. When leakage rate was used as the feedback signal, the setpoint leakage rate was typically maintained within 1 slm. However, larger deviations occurred during sudden changes in sealed pressure. When face temperature was used as the feedback signal, the setpoint face temperature was generally maintained within 3 C, with larger deviations occurring when the sealed pressure changes suddenly. the experimental results were compared to the predictions from the mathematical model. The model was successful in predicting the trends in leakage rate that occurred as the balance ratio and sealed pressure changed

  18. Active control of near-field coupling in conductively coupled microelectromechanical system metamaterial devices

    NASA Astrophysics Data System (ADS)

    Pitchappa, Prakash; Manjappa, Manukumara; Ho, Chong Pei; Qian, You; Singh, Ranjan; Singh, Navab; Lee, Chengkuo

    2016-03-01

    We experimentally report a structurally reconfigurable metamaterial for active switching of near-field coupling in conductively coupled, orthogonally twisted split ring resonators (SRRs) operating in the terahertz spectral region. Out-of-plane reconfigurable microcantilevers integrated into the dark SRR geometry are used to provide active frequency tuning of dark SRR resonance. The geometrical parameters of individual SRRs are designed to have identical inductive-capacitive resonant frequency. This allows for the excitation of classical analogue of electromagnetically induced transparency (EIT) due to the strong conductive coupling between the SRRs. When the microcantilevers are curved up, the resonant frequency of dark SRR blue-shifts and the EIT peak is completely modulated while the SRRs are still conductively connected. EIT modulation contrast of ˜50% is experimentally achieved with actively switchable group delay of ˜2.5 ps. Electrical control, miniaturized size, and readily integrable fabrication process of the proposed structurally reconfigurable metamaterial make it an ideal candidate for the realization of various terahertz communication devices such as electrically controllable terahertz delay lines, buffers, and tunable data-rate channels.

  19. Dielectric elastomer actuators for active microfluidic control

    NASA Astrophysics Data System (ADS)

    McCoul, David; Murray, Coleman; Di Carlo, Dino; Pei, Qibing

    2013-04-01

    Dielectric elastomers with low modulus and large actuation strain have been investigated for applications in which they serve as "active" microfluidic channel walls. Anisotropically prestrained acrylic elastomer membranes are bonded to cover open trenches formed on a silicone elastomer substrate. Actuation of the elastomer membranes increases the cross-sectional area of the resulting channels, in turn controlling hydraulic flow rate and pressure. Bias voltage increases the active area of the membranes, allowing intrachannel pressure to alter channel geometry. The channels have also demonstrated the ability to actively clear a blockage. Applications may include adaptive microfilters, micro-peristaltic pumps, and reduced-complexity lab-on-a-chip devices.

  20. Cellular Mechanisms Controlling Caspase Activation and Function

    PubMed Central

    Parrish, Amanda B.; Freel, Christopher D.; Kornbluth, Sally

    2013-01-01

    Caspases are the primary drivers of apoptotic cell death, cleaving cellular proteins that are critical for dismantling the dying cell. Initially translated as inactive zymogenic precursors, caspases are activated in response to a variety of cell death stimuli. In addition to factors required for their direct activation (e.g., dimerizing adaptor proteins in the case of initiator caspases that lie at the apex of apoptotic signaling cascades), caspases are regulated by a variety of cellular factors in a myriad of physiological and pathological settings. For example, caspases may be modified posttranslationally (e.g., by phosphorylation or ubiquitylation) or through interaction of modulatory factors with either the zymogenic or active form of a caspase, altering its activation and/or activity. These regulatory events may inhibit or enhance enzymatic activity or may affect activity toward particular cellular substrates. Finally, there is emerging literature to suggest that caspases can participate in a variety of cellular processes unrelated to apoptotic cell death. In these settings, it is particularly important that caspases are maintained under stringent control to avoid inadvertent cell death. It is likely that continued examination of these processes will reveal new mechanisms of caspase regulation with implications well beyond control of apoptotic cell death. PMID:23732469

  1. MODELING MERCURY CONTROL WITH POWDERED ACTIVATED CARBON

    EPA Science Inventory

    The paper presents a mathematical model of total mercury removed from the flue gas at coal-fired plants equipped with powdered activated carbon (PAC) injection for Mercury control. The developed algorithms account for mercury removal by both existing equipment and an added PAC in...

  2. Active controls technology to maximize structural efficiency

    NASA Technical Reports Server (NTRS)

    Hoy, J. M.; Arnold, J. M.

    1978-01-01

    The implication of the dependence on active controls technology during the design phase of transport structures is considered. Critical loading conditions are discussed along with probable ways of alleviating these loads. Why fatigue requirements may be critical and can only be partially alleviated is explained. The significance of certain flutter suppression system criteria is examined.

  3. Spacecraft active thermal control technology status

    NASA Technical Reports Server (NTRS)

    Ellis, W. E.

    1978-01-01

    Four advanced space radiator concepts that were pursued in an integrated effort to develop multi-mission-use and low cost heat rejection systems which can overcome the limitations of current radiator systems are briefly discussed and described. Also, in order to establish a firm background to compare the advanced space radiator concepts, the Orbiter active thermal control system is also briefly described.

  4. DNA-based control of protein activity

    PubMed Central

    Engelen, W.; Janssen, B. M. G.

    2016-01-01

    DNA has emerged as a highly versatile construction material for nanometer-sized structures and sophisticated molecular machines and circuits. The successful application of nucleic acid based systems greatly relies on their ability to autonomously sense and act on their environment. In this feature article, the development of DNA-based strategies to dynamically control protein activity via oligonucleotide triggers is discussed. Depending on the desired application, protein activity can be controlled by directly conjugating them to an oligonucleotide handle, or expressing them as a fusion protein with DNA binding motifs. To control proteins without modifying them chemically or genetically, multivalent ligands and aptamers that reversibly inhibit their function provide valuable tools to regulate proteins in a noncovalent manner. The goal of this feature article is to give an overview of strategies developed to control protein activity via oligonucleotide-based triggers, as well as hurdles yet to be taken to obtain fully autonomous systems that interrogate, process and act on their environments by means of DNA-based protein control. PMID:26812623

  5. DNA-based control of protein activity.

    PubMed

    Engelen, W; Janssen, B M G; Merkx, M

    2016-03-01

    DNA has emerged as a highly versatile construction material for nanometer-sized structures and sophisticated molecular machines and circuits. The successful application of nucleic acid based systems greatly relies on their ability to autonomously sense and act on their environment. In this feature article, the development of DNA-based strategies to dynamically control protein activity via oligonucleotide triggers is discussed. Depending on the desired application, protein activity can be controlled by directly conjugating them to an oligonucleotide handle, or expressing them as a fusion protein with DNA binding motifs. To control proteins without modifying them chemically or genetically, multivalent ligands and aptamers that reversibly inhibit their function provide valuable tools to regulate proteins in a noncovalent manner. The goal of this feature article is to give an overview of strategies developed to control protein activity via oligonucleotide-based triggers, as well as hurdles yet to be taken to obtain fully autonomous systems that interrogate, process and act on their environments by means of DNA-based protein control. PMID:26812623

  6. Active control of vibration transmission through struts

    NASA Astrophysics Data System (ADS)

    Pelinescu, Ion; Balachandran, Balakumar

    1998-07-01

    In this work, analytical investigations into active control of longitudinal and flexural vibrations transmitted through a cylindrical strut are conducted. A mechanics based model for a strut fitted with a piezoelectric actuator is developed. For harmonic disturbances, a linear dynamic formulation describing the motion of the actuator is integrated with the formulation describing wave transmission through the strut, and the resulting system is studied in the frequency domain. Open-loop studies are conducted with the aid of numerical simulations, and the potential of active control schemes to attenuate the transmitted vibrations over the frequency range of 10 Hz to 6000 Hz is examined. The relevance of the current work to control of helicopter cabin interior noise is also discussed.

  7. Twisted Cucurbit[n]urils.

    PubMed

    Li, Qing; Qiu, Sheng-Chao; Zhang, Jing; Chen, Kai; Huang, Ying; Xiao, Xin; Zhang, Yingjie; Li, Feng; Zhang, Yun-Qian; Xue, Sai-Feng; Zhu, Qian-Jiang; Tao, Zhu; Lindoy, Leonard F; Wei, Gang

    2016-08-19

    Two new twisted cucurbiturils, cucurbit[13]uril (tQ[13]) and cucurbit[15]uril (tQ[15]), have been synthesized and separated, and their structures have been confirmed by NMR spectroscopy and MALDI-TOF mass spectrometry together with the X-ray structures of two new complexes, {Dy(H2O)4Cd(H2O)4tQ[13]}·2.5[CdCl4]·65H2O and {Cd0.5(H2O)2tQ[15]}·[CdCl4]·47H2O. tQ[15] is the largest cucurbit[n]uril (Q[n]) in the Q[n] family reported to date. The X-ray diffraction studies of both complexes indicated that these large tQ[n]s effectively exhibit two different cavities-a central cavity and two side cavities. Preliminary host-guest behavior by each of the new systems was investigated by NMR studies. PMID:27499014

  8. Bubble Divergences from Twisted Cohomology

    NASA Astrophysics Data System (ADS)

    Bonzom, Valentin; Smerlak, Matteo

    2012-06-01

    We consider a class of lattice topological field theories, among which are the weak-coupling limit of 2d Yang-Mills theory and 3d Riemannian quantum gravity, whose dynamical variables are flat discrete connections with compact structure group on a cell 2-complex. In these models, it is known that the path integral measure is ill-defined because of a phenomenon known as `bubble divergences'. In this paper, we extend recent results of the authors to the cases where these divergences cannot be understood in terms of cellular cohomology. We introduce in its place the relevant twisted cohomology, and use it to compute the divergence degree of the partition function. We also relate its dominant part to the Reidemeister torsion of the complex, thereby generalizing previous results of Barrett and Naish-Guzman. The main limitation to our approach is the presence of singularities in the representation variety of the fundamental group of the complex; we illustrate this issue in the well-known case of two-dimensional manifolds.

  9. Active control of transmitted sound in buildings

    NASA Astrophysics Data System (ADS)

    Thompsett, Russell Harvey George

    The problem of noise from neighbours has increased dramatically over the last few years. Many of the noise complaints are due to the high level, low frequency noise from modern stereo equipment, and are often described in terms of the low frequency characteristics of the music; the repetitive, booming, bass beat. The objective of this research was to establish the feasibility of applying active noise control to alleviate this problem. The initial approach was to evaluate the possibility of exploiting the dominance of individual modes in the response of rooms at low frequency to effect global control. However, initial investigations using a modal model of the sound field revealed that this would be difficult due to the contribution of many acoustic modes excited off resonance. This conclusion was supported by measurements of acoustic room responses in typical buildings, illustrating a non-resonant characteristic. Consequently, attention was turned to the feasibility of using local active control systems to create zones of quiet by concentrating control at a specific location near the observers ears, for example in a seat headrest, or near the pillows of a bed. The lack of a reference signal in either approach requires the use of a feedback control strategy. With a typically non-resonant system, the predictability in the disturbance necessary for successful feedback control must be contained in the primary excitation, namely the music. Examples of different music styles were investigated and of those with the potential to be a nuisance surprisingly few were significantly more predictable than a random disturbance. As expected the most encouraging control performance simulations were found for modern dance music, with a strong repetitive beat. A real-time, local controller was demonstrated in the laboratory with such a disturbance signal and the properties of the quiet zone were measured. The subjective response when hearing the controller in operation was found to be

  10. Modeling piston-ring dynamics, blowby, and ring-twist effects

    SciTech Connect

    Tian, T.; Noordzij, L.B.; Wong, V.W.; Heywood, J.B.

    1996-12-31

    A ring-dynamics and gas-flow model has been developed to study ring/groove contact, blowby, and the influence of ring static twist, keystone ring/groove configurations, and other piston and ring parameters. The model is developed for a ring pack with three rings. The dynamics of the top two rings and the gas pressures in the regions above the oil control ring are simulated. Distributions of oil film thickness and surface roughness on the groove and ring surfaces are assumed in the model to calculate the forces generated by the ring/groove contact. Ring static and dynamic twists are considered as well as different keystone ring/groove configurations. Ring dynamics and gas flows are coupled in the formulation and an implicit scheme is implemented, enabling the model to resolve detailed events such as ring flutter. Studies on a spark ignition engine found that static twist or, more generally speaking, the relative angle between rings and their grooves, has great influence on ring/groove contact characteristics, ring stability, and blowby. Ring flutter is found to occur for the second ring with a negative static twist under normal operating conditions and for the top ring with a negative static twist under high-speed/low-load operating conditions. Studies on a diesel engine show that different keystone ring/groove configurations result in different twist behaviors of the ring that may affect the wear pattern of the keystone ring running surfaces.

  11. Wrinkles, loops, and topological defects in twisted ribbons

    NASA Astrophysics Data System (ADS)

    Chopin, Julien

    Nature abounds with elastic ribbon like shapes including double-stranded semiflexible polymers, graphene and metal oxide nanoribbons which are examples of elongated elastic structures with a strongly anisotropic cross-section. Due to this specific geometry, it is far from trivial to anticipate if a ribbon should be considered as a flat flexible filament or a narrow thin plate. We thus perform an experiment in which a thin elastic ribbon is loaded using a twisting and traction device coupled with a micro X-ray computed tomography machine allowing a full 3D shape reconstruction. A wealth of morphological behaviors can be observed including wrinkled helicoids, curled and looped configurations, and faceted ribbons. In this talk, I will show that most morphologies can be understood using a far-from-threshold approach and simple scaling arguments. Further, we find that the various shapes can be organized in a phase diagram using the twist, the tension, and the geometry of the ribbon as control parameters. Finally, I will discuss the spontaneous formation of topological defects with negatively-signed Gaussian charge at large twist and small but finite stretch.

  12. Highly twisted double-helix carbon nanotube yarns.

    PubMed

    Shang, Yuanyuan; Li, Yibin; He, Xiaodong; Du, Shanyi; Zhang, Luhui; Shi, Enzheng; Wu, Shiting; Li, Zhen; Li, Peixu; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai; Cao, Anyuan

    2013-02-26

    The strength and flexibility of carbon nanotubes (CNTs) allow them to be constructed into a variety of innovated architectures with fascinating properties. Here, we show that CNTs can be made into a highly twisted yarn-derived double-helix structure by a conventional twist-spinning process. The double-helix is a stable and hierarchical configuration consisting of two single-helical yarn segments, with controlled pitch and unique mechanical properties. While one of the yarn components breaks early under tension due to the highly twisted state, the second yarn produces much larger tensile strain and significantly prolongs the process until ultimate fracture. In addition, these elastic and conductive double-helix yarns show simultaneous and reversible resistance change in response to a wide range of input sources (mechanical, photo, and thermal) such as applied strains or stresses, light illumination, and environmental temperature. Our results indicate that it is possible to create higher-level, more complex architectures from CNT yarns and fabricate multifunctional nanomaterials with potential applications in many areas. PMID:23289799

  13. van Hove Singularity Enhanced Photochemical Reactivity of Twisted Bilayer Graphene.

    PubMed

    Liao, Lei; Wang, Huan; Peng, Han; Yin, Jianbo; Koh, Ai Leen; Chen, Yulin; Xie, Qin; Peng, Hailin; Liu, Zhongfan

    2015-08-12

    Twisted bilayer graphene (tBLG) exhibits van Hove singularities (VHSs) in the density of states that can be tuned by changing the twist angle (θ), sparking various novel physical phenomena. Much effort has been devoted to investigate the θ-dependent physical properties of tBLG. Yet, the chemical properties of tBLG with VHSs, especially the chemical reactivity, remain unexplored. Here we report the first systematic study on the chemistry of tBLG through the photochemical reaction between graphene and benzoyl peroxide. Twisted bilayer graphene exhibits θ-dependent reactivity, and remarkably enhanced reactivity is obtained when the energy of incident laser matches with the energy interval of the VHSs of tBLG. This work provides an insight on the chemistry of tBLG, and the successful enhancement of chemical reactivity derived from VHS is highly beneficial for the controllable chemical modification of tBLG as well as the development of tBLG based devices. PMID:26151687

  14. Controlling Contagion Processes in Activity Driven Networks

    NASA Astrophysics Data System (ADS)

    Liu, Suyu; Perra, Nicola; Karsai, Márton; Vespignani, Alessandro

    2014-03-01

    The vast majority of strategies aimed at controlling contagion processes on networks consider the connectivity pattern of the system either quenched or annealed. However, in the real world, many networks are highly dynamical and evolve, in time, concurrently with the contagion process. Here, we derive an analytical framework for the study of control strategies specifically devised for a class of time-varying networks, namely activity-driven networks. We develop a block variable mean-field approach that allows the derivation of the equations describing the coevolution of the contagion process and the network dynamic. We derive the critical immunization threshold and assess the effectiveness of three different control strategies. Finally, we validate the theoretical picture by simulating numerically the spreading process and control strategies in both synthetic networks and a large-scale, real-world, mobile telephone call data set.

  15. Control Systems Cyber Security Standards Support Activities

    SciTech Connect

    Robert Evans

    2009-01-01

    The Department of Homeland Security’s Control Systems Security Program (CSSP) is working with industry to secure critical infrastructure sectors from cyber intrusions that could compromise control systems. This document describes CSSP’s current activities with industry organizations in developing cyber security standards for control systems. In addition, it summarizes the standards work being conducted by organizations within the sector and provides a brief listing of sector meetings and conferences that might be of interest for each sector. Control systems cyber security standards are part of a rapidly changing environment. The participation of CSSP in the development effort for these standards has provided consistency in the technical content of the standards while ensuring that information developed by CSSP is included.

  16. Actively controlled vibration welding system and method

    SciTech Connect

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  17. Optogenetic feedback control of neural activity

    PubMed Central

    Newman, Jonathan P; Fong, Ming-fai; Millard, Daniel C; Whitmire, Clarissa J; Stanley, Garrett B; Potter, Steve M

    2015-01-01

    Optogenetic techniques enable precise excitation and inhibition of firing in specified neuronal populations and artifact-free recording of firing activity. Several studies have suggested that optical stimulation provides the precision and dynamic range requisite for closed-loop neuronal control, but no approach yet permits feedback control of neuronal firing. Here we present the ‘optoclamp’, a feedback control technology that provides continuous, real-time adjustments of bidirectional optical stimulation in order to lock spiking activity at specified targets over timescales ranging from seconds to days. We demonstrate how this system can be used to decouple neuronal firing levels from ongoing changes in network excitability due to multi-hour periods of glutamatergic or GABAergic neurotransmission blockade in vitro as well as impinging vibrissal sensory drive in vivo. This technology enables continuous, precise optical control of firing in neuronal populations in order to disentangle causally related variables of circuit activation in a physiologically and ethologically relevant manner. DOI: http://dx.doi.org/10.7554/eLife.07192.001 PMID:26140329

  18. Vibrating surface actuators for active flow control

    NASA Astrophysics Data System (ADS)

    Calkins, Frederick T.; Clingman, Dan J.

    2002-07-01

    Current research has shown that aircraft can gain significant aerodynamic performance benefits from active flow control (AFC). AFC seeks to control large scale flows by exploiting natural response triggered by small energy inputs. The principal target application is download alleviation of the V-22 Osprey under the DARPA sponsored Boeing Active Flow Control System program. One method of injecting energy into the flow over the V22 wings is to use an active vibrating surface on the passive seal between the wing and flapperon. The active surface is an oscillating cantilevered beam which injects fluid into the flow, similar to a synthetic jet, and interacts with the flow field. Two types of actuators, or flipperons, are explored. The first is a multilayer piezoelectric polyvinylidene fluoride cantilevered bender. The second is a single crystal piezoelectric (SCP)d31 poled wafer mounted on a cantilevered spring steel substrate. This paper details the development effort including fabrication, mechanical and electrical testing, and modeling for both types of actuators. Both flipperons were mounted on the passive seal between a 1/10th scale V22 wing and flapperon and the aerodynamic performance evaluated in low speed wind tunnel. The SCP flipperon demonstrated significant cruise benefits, with increase of 10 percent lift and 20 percent angle of attack capability. The PVDF flipperon provided a 16 percent drag reduction in the hover mode.

  19. Market-based control of active surfaces

    NASA Astrophysics Data System (ADS)

    Berlin, Andrew A.; Hogg, Tad; Jackson, Warren B.

    1998-12-01

    This paper describes a market-based approach to controlling a smart matter-based object transport system, in which an array of distributed air jets applies forces to levitate and control the motion of a planar object. In the smart matter regime, the effects of spatial and temporal variation of operating parameters among a multiplicity of sensor, actuators, and controllers make it desirable for a control strategy to exhibit a minimal dependence on system models, and to be able to arbitrate among conflicting goals. A market-based strategy is introduced that aggregates the control requirements of multiple relatively simple local controllers, each of which seeks to optimize the performance of the system within a limited spatial and temporal range. These local controllers act as the market's consumers, and two sets of distributed air jets act as the producers. Experiments are performed comparing the performance of the market-based strategy to a near-optimal model-derived benchmark, as well as to a hand-tuned PD controller. Results indicate that even though the local controllers in the market are not based on a detailed model of the system dynamics, the market is able to effectively approximate the performance of the model-based benchmark. In certain specialized cases, such as tracking a step trajectory, the performance of the market surpasses the performance of the model-based benchmark by balancing the needs of conflicting control goals. A brief overview of the active surface smart matter prototype being developed at Xerox PARC that is the motivation behind this work is also presented.

  20. Active control of chirality in nonlinear metamaterials

    SciTech Connect

    Zhu, Yu; Chai, Zhen; Yang, Hong; Hu, Xiaoyong Gong, Qihuang

    2015-03-02

    An all-optical tunabe chirality is realized in a photonic metamaterial, the metamolecule of which consists of a nonlinear nano-Au:polycrystalline indium-tin oxide layer sandwiched between two L-shaped gold nano-antennas twisted 90° with each other. The maximum circular dichroism reached 30%. Under excitation of a 40 kW/cm{sup 2} weak pump light, the peak in the circular dichroism shifts 45 nm in the short-wavelength direction. An ultrafast response time of 35 ps is maintained. This work not only opens up the possibility for the realization of ultralow-power and ultrafast all-optical tunable chirality but also offers a way to construct ultrahigh-speed on-chip biochemical sensors.

  1. Hybrid dampers for active vibration control

    SciTech Connect

    Gordaninejad, F.; Ray, A.

    1994-12-31

    In the present investigation feasibility of using hybrid electrorheological (ER) fluid dampers for active vibration control is examined. Small-scale, three-electrode hybrid dampers were designed and built such that they have two separate compartments to contain a viscous oil and an ER fluid. The results were compared to those obtained using a three-electrode ER fluid damper. It was shown that the use of hybrid ER fluid damper can enhance the damping. It was also found that the bang-bang and linear proportional control algorithms have similar effects on the amplitude-time response obtained from hybrid and ER fluid dampers.

  2. Distributed Energy Communications & Controls, Lab Activities - Summary

    SciTech Connect

    Rizy, D Tom

    2010-01-01

    The purpose is to develop controls for inverter-based renewable and non-renewable distributed energy systems to provide local voltage, power and power quality support for loads and the power grid. The objectives are to (1) develop adaptive controls for inverter-based distributed energy (DE) systems when there are multiple inverters on the same feeder and (2) determine the impact of high penetration high seasonal energy efficiency ratio (SEER) air conditioning (A/C) units on power systems during sub-transmission faults which can result in an A/C compressor motor stall and assess how inverter-based DE can help to mitigate the stall event. The Distributed Energy Communications & Controls Laboratory (DECC) is a unique facility for studying dynamic voltage, active power (P), non-active power (Q) and power factor control from inverter-based renewable distributed energy (DE) resources. Conventionally, inverter-based DE systems have been designed to provide constant, close to unity power factor and thus not provide any voltage support. The DECC Lab interfaces with the ORNL campus distribution system to provide actual power system testing of the controls approach. Using mathematical software tools and the DECC Lab environment, we are developing and testing local, autonomous and adaptive controls for local voltage control and P & Q control for inverter-based DE. We successfully tested our active and non-active power (P,Q) controls at the DECC laboratory along with voltage regulation controls. The new PQ control along with current limiter controls has been tested on our existing inverter test system. We have tested both non-adaptive and adaptive control modes for the PQ control. We have completed several technical papers on the approaches and results. Electric power distribution systems are experiencing outages due to a phenomenon known as fault induced delayed voltage recovery (FIDVR) due to air conditioning (A/C) compressor motor stall. Local voltage collapse from FIDVR is

  3. Design and analysis of variable-twist tiltrotor blades using shape memory alloy hybrid composites

    NASA Astrophysics Data System (ADS)

    Park, Jae-Sang; Kim, Seong-Hwan; Jung, Sung Nam; Lee, Myeong-Kyu

    2011-01-01

    The tiltrotor blade, or proprotor, acts as a rotor in the helicopter mode and as a propeller in the airplane mode. For a better performance, the proprotor should have different built-in twist distributions along the blade span, suitable for each operational mode. This paper proposes a new variable-twist proprotor concept that can adjust the built-in twist distribution for given flight modes. For a variable-twist control, the present proprotor adopts shape memory alloy hybrid composites (SMAHC) containing shape memory alloy (SMA) wires embedded in the composite matrix. The proprotor of the Korea Aerospace Research Institute (KARI) Smart Unmanned Aerial Vehicle (SUAV), which is based on the tiltrotor concept, is used as a baseline proprotor model. The cross-sectional properties of the variable-twist proprotor are designed to maintain the cross-sectional properties of the original proprotor as closely as possible. However, the torsion stiffness is significantly reduced to accommodate the variable-twist control. A nonlinear flexible multibody dynamic analysis is employed to investigate the dynamic characteristics of the proprotor such as natural frequency and damping in the whirl flutter mode, the blade structural loads in a transition flight and the rotor performance in hover. The numerical results show that the present proprotor is designed to have a strong similarity to the baseline proprotor in dynamic and load characteristics. It is demonstrated that the present proprotor concept could be used to improve the hover performance adaptively when the variable-twist control using the SMAHC is applied appropriately.

  4. Exotic Twisted Equivariant Cohomology of Loop Spaces, Twisted Bismut-Chern Character and T-Duality

    NASA Astrophysics Data System (ADS)

    Han, Fei; Mathai, Varghese

    2015-07-01

    We define exotic twisted - equivariant cohomology for the loop space LZ of a smooth manifold Z via the invariant differential forms on LZ with coefficients in the (typically non-flat) holonomy line bundle of a gerbe, with differential an equivariantly flat superconnection. We introduce the twisted Bismut-Chern character form, a loop space refinement of the twisted Chern character form in Bouwknegt et al. (Commun Math Phys 228:17-49, 2002) and Mathai and Stevenson (Commun Math Phys 236:161-186, 2003), which represents classes in the completed periodic exotic twisted -equivariant cohomology of LZ.We establish a localisation theorem for the completed periodic exotic twisted -equivariant cohomology for loop spaces and apply it to establish T-duality in a background flux in type II String Theory from a loop space perspective.

  5. Unsteady aerodynamic modeling and active aeroelastic control

    NASA Technical Reports Server (NTRS)

    Edwards, J. W.

    1977-01-01

    Unsteady aerodynamic modeling techniques are developed and applied to the study of active control of elastic vehicles. The problem of active control of a supercritical flutter mode poses a definite design goal stability, and is treated in detail. The transfer functions relating the arbitrary airfoil motions to the airloads are derived from the Laplace transforms of the linearized airload expressions for incompressible two dimensional flow. The transfer function relating the motions to the circulatory part of these loads is recognized as the Theodorsen function extended to complex values of reduced frequency, and is termed the generalized Theodorsen function. Inversion of the Laplace transforms yields exact transient airloads and airfoil motions. Exact root loci of aeroelastic modes are calculated, providing quantitative information regarding subcritical and supercritical flutter conditions.

  6. Advanced Active Thermal Control Systems Architecture Study

    NASA Technical Reports Server (NTRS)

    Hanford, Anthony J.; Ewert, Michael K.

    1996-01-01

    The Johnson Space Center (JSC) initiated a dynamic study to determine possible improvements available through advanced technologies (not used on previous or current human vehicles), identify promising development initiatives for advanced active thermal control systems (ATCS's), and help prioritize funding and personnel distribution among many research projects by providing a common basis to compare several diverse technologies. Some technologies included were two-phase thermal control systems, light-weight radiators, phase-change thermal storage, rotary fluid coupler, and heat pumps. JSC designed the study to estimate potential benefits from these various proposed and under-development thermal control technologies for five possible human missions early in the next century. The study compared all the technologies to a baseline mission using mass as a basis. Each baseline mission assumed an internal thermal control system; an external thermal control system; and aluminum, flow-through radiators. Solar vapor compression heat pumps and light-weight radiators showed the greatest promise as general advanced thermal technologies which can be applied across a range of missions. This initial study identified several other promising ATCS technologies which offer mass savings and other savings compared to traditional thermal control systems. Because the study format compares various architectures with a commonly defined baseline, it is versatile and expandable, and is expected to be updated as needed.

  7. Active Thermal Control System Development for Exploration

    NASA Technical Reports Server (NTRS)

    Westheimer, David

    2007-01-01

    All space vehicles or habitats require thermal management to maintain a safe and operational environment for both crew and hardware. Active Thermal Control Systems (ATCS) perform the functions of acquiring heat from both crew and hardware within a vehicle, transporting that heat throughout the vehicle, and finally rejecting that energy into space. Almost all of the energy used in a space vehicle eventually turns into heat, which must be rejected in order to maintain an energy balance and temperature control of the vehicle. For crewed vehicles, Active Thermal Control Systems are pumped fluid loops that are made up of components designed to perform these functions. NASA has been actively developing technologies that will enable future missions or will provide significant improvements over the state of the art technologies. These technologies have are targeted for application on the Crew Exploration Vehicle (CEV), or Orion, and a Lunar Surface Access Module (LSAM). The technologies that have been selected and are currently under development include: fluids that enable single loop ATCS architectures, a gravity insensitive vapor compression cycle heat pump, a sublimator with reduced sensitivity to feedwater contamination, an evaporative heat sink that can operate in multiple ambient pressure environments, a compact spray evaporator, and lightweight radiators that take advantage of carbon composites and advanced optical coatings.

  8. Active control of electric potential of spacecraft

    NASA Technical Reports Server (NTRS)

    Goldstein, R.

    1977-01-01

    Techniques are discussed for controlling the potential of a spacecraft by means of devices which release appropriate charged particles from the spacecraft to the environment. Attention is given to electron emitters, ion emitters, a basic electron emitter arrangement, techniques for sensing electric field or potential, and flight experiments on active potential control. It is recommended to avoid differential charging on spacecraft surfaces because it can severely affect the efficacy of emitters. Discharging the frame of a spacecraft with dielectric surfaces involves the risk of stressing the dielectric material excessively. The spacecraft should, therefore, be provided with grounded conductive surfaces. It is pointed out that particles released by control systems can return to the spacecraft.

  9. Active control of combustion for optimal performance

    SciTech Connect

    Jackson, M.D.; Agrawal, A.K.

    1999-07-01

    Combustion-zone stoichiometry and fuel-air premixing were actively controlled to optimize the combustor performance over a range of operating conditions. The objective was to maximize the combustion temperature, while maintaining NO{sub x} within a specified limit. The combustion system consisted of a premixer located coaxially near the inlet of a water-cooled shroud. The equivalence ratio was controlled by a variable-speed suction fan located downstream. The split between the premixing air and diffusion air was governed by the distance between the premixer and shroud. The combustor performance was characterized by a cost function evaluated from time-averaged measurements of NO{sub x} and oxygen concentrations in products. The cost function was minimized by downhill simplex algorithm employing closed-loop feedback. Experiments were conducted at different fuel flow rates to demonstrate that the controller optimized the performance without prior knowledge of the combustor behavior.

  10. Distributed control system for active mirrors

    NASA Astrophysics Data System (ADS)

    Rodriguez-Ramos, Luis F.; Williams, Mark R.; Castro, Javier; Cruz, A.; Gonzalez, Juan C.; Mack, Brian; Martin, Carlos; Pescador, German; Sanchez, Vicente; Sosa, Nicolas A.

    1994-06-01

    This paper presents the IAC (Instituto de Astrofisica de Canaries, Spain) proposal of a distributed control system intended for the active support of a 8 m mirror. The system incorporates a large number of compact `smart' force actuators, six force definers, and a mirror support computer (MSC) for interfacing with the telescope control system and for general housekeeping. We propose the use of a network for the interconnection of the actuators, definers and the MSC, which will minimize the physical complexity of the interface between the mirror support system and the MSC. The force actuator control electronics are described in detail, as is the system software architecture of the actuator and the MSC. As the network is a key point for the system, we also detail the evaluation of three candidates, before electing the CAN bus.

  11. The Middeck Active Control Experiment (MACE)

    NASA Technical Reports Server (NTRS)

    Miller, David W.; Sepe, Raymond B.; Rey, Daniel; Saarmaa, Erik; Crawley, Edward F.

    1993-01-01

    The Middeck Active Control Experiment (MACE) is a NASA In-Step and Control Structure Interaction (CSI) Office funded Shuttle middeck experiment. The objective is to investigate the extent to which closed-loop behavior of flexible spacecraft in zero-gravity (0-g) can be predicted. This prediction becomes particularly difficult when dynamic behavior during ground testing exhibits extensive suspension and direct gravity coupling. On-orbit system identification and control reconfiguration is investigated to improve performance which would otherwise be limited due to errors in prediction. The program is presently in its preliminary design phase with launch expected in the summer of 1994. The MACE test article consists of three attitude control torque wheels, a two axis gimballing payload, inertial sensors and a flexible support structure. With the acquisition of a second payload, this will represent a multiple payload platform with significant structural flexibility. This paper presents on-going work in the areas of modelling and control of the MACE test article in the zero and one-gravity environments. Finite element models, which include suspension and gravity effects, and measurement models, derived from experimental data, are used as the basis for Linear Quadratic Gaussian controller designs. Finite element based controllers are analytically used to study the differences in closed-loop performance as the test article transitions between the 0-g and 1-g environments. Measurement based controllers are experimentally applied to the MACE test article in the 1-g environment and achieve over an order of magnitude improvement in payload pointing accuracy when disturbed by a broadband torque disturbance. The various aspects of the flight portion of the experiment are also discussed.

  12. The Middeck Active Control Experiment (MACE)

    NASA Astrophysics Data System (ADS)

    Miller, David W.; Sepe, Raymond B.; Rey, Daniel; Saarmaa, Erik; Crawley, Edward F.

    1993-02-01

    The Middeck Active Control Experiment (MACE) is a NASA In-Step and Control Structure Interaction (CSI) Office funded Shuttle middeck experiment. The objective is to investigate the extent to which closed-loop behavior of flexible spacecraft in zero-gravity (0-g) can be predicted. This prediction becomes particularly difficult when dynamic behavior during ground testing exhibits extensive suspension and direct gravity coupling. On-orbit system identification and control reconfiguration is investigated to improve performance which would otherwise be limited due to errors in prediction. The program is presently in its preliminary design phase with launch expected in the summer of 1994. The MACE test article consists of three attitude control torque wheels, a two axis gimballing payload, inertial sensors and a flexible support structure. With the acquisition of a second payload, this will represent a multiple payload platform with significant structural flexibility. This paper presents on-going work in the areas of modelling and control of the MACE test article in the zero and one-gravity environments. Finite element models, which include suspension and gravity effects, and measurement models, derived from experimental data, are used as the basis for Linear Quadratic Gaussian controller designs. Finite element based controllers are analytically used to study the differences in closed-loop performance as the test article transitions between the 0-g and 1-g environments. Measurement based controllers are experimentally applied to the MACE test article in the 1-g environment and achieve over an order of magnitude improvement in payload pointing accuracy when disturbed by a broadband torque disturbance. The various aspects of the flight portion of the experiment are also discussed.

  13. Mesoscale mechanics of twisting carbon nanotube yarns.

    PubMed

    Mirzaeifar, Reza; Qin, Zhao; Buehler, Markus J

    2015-03-12

    Fabricating continuous macroscopic carbon nanotube (CNT) yarns with mechanical properties close to individual CNTs remains a major challenge. Spinning CNT fibers and ribbons for enhancing the weak interactions between the nanotubes is a simple and efficient method for fabricating high-strength and tough continuous yarns. Here we investigate the mesoscale mechanics of twisting CNT yarns using full atomistic and coarse grained molecular dynamics simulations, considering concurrent mechanisms at multiple length-scales. To investigate the mechanical response of such a complex structure without losing insights into the molecular mechanism, we applied a multiscale strategy. The full atomistic results are used for training a coarse grained model for studying larger systems consisting of several CNTs. The mesoscopic model parameters are updated as a function of the twist angle, based on the full atomistic results, in order to incorporate the atomistic scale deformation mechanisms in larger scale simulations. By bridging across two length scales, our model is capable of accurately predicting the mechanical behavior of twisted yarns while the atomistic level deformations in individual nanotubes are integrated into the model by updating the parameters. Our results focused on studying a bundle of close packed nanotubes provide novel mechanistic insights into the spinning of CNTs. Our simulations reveal how twisting a bundle of CNTs improves the shear interaction between the nanotubes up to a certain level due to increasing the interaction surface. Furthermore, twisting the bundle weakens the intertube interactions due to excessive deformation in the cross sections of individual CNTs in the bundle. PMID:25732328

  14. Mesoscale mechanics of twisting carbon nanotube yarns

    NASA Astrophysics Data System (ADS)

    Mirzaeifar, Reza; Qin, Zhao; Buehler, Markus J.

    2015-03-01

    Fabricating continuous macroscopic carbon nanotube (CNT) yarns with mechanical properties close to individual CNTs remains a major challenge. Spinning CNT fibers and ribbons for enhancing the weak interactions between the nanotubes is a simple and efficient method for fabricating high-strength and tough continuous yarns. Here we investigate the mesoscale mechanics of twisting CNT yarns using full atomistic and coarse grained molecular dynamics simulations, considering concurrent mechanisms at multiple length-scales. To investigate the mechanical response of such a complex structure without losing insights into the molecular mechanism, we applied a multiscale strategy. The full atomistic results are used for training a coarse grained model for studying larger systems consisting of several CNTs. The mesoscopic model parameters are updated as a function of the twist angle, based on the full atomistic results, in order to incorporate the atomistic scale deformation mechanisms in larger scale simulations. By bridging across two length scales, our model is capable of accurately predicting the mechanical behavior of twisted yarns while the atomistic level deformations in individual nanotubes are integrated into the model by updating the parameters. Our results focused on studying a bundle of close packed nanotubes provide novel mechanistic insights into the spinning of CNTs. Our simulations reveal how twisting a bundle of CNTs improves the shear interaction between the nanotubes up to a certain level due to increasing the interaction surface. Furthermore, twisting the bundle weakens the intertube interactions due to excessive deformation in the cross sections of individual CNTs in the bundle.

  15. Application of active controls to civil transport aircraft

    NASA Technical Reports Server (NTRS)

    Taylor, L. W., Jr.

    1975-01-01

    The impact of active controls on civil transport aircraft and some of the complex problems involved are described. The approach taken by NASA as part of the Active Control Technology Program is discussed to integrate active controls in the conceptual design phase. It is shown that when handled correctly, active controls improve aircraft performance.

  16. Local flow control for active building facades

    NASA Astrophysics Data System (ADS)

    Kaligotla, Srikar; Chen, Wayne; Glauser, Mark

    2010-11-01

    Existing building facade designs are for a passive and an impermeable shell to prevent migration of outdoor air into the building and to control heat transfers between the exterior environment and the building interior. An active facade that can respond in real time to changing environmental conditions like wind speed and direction, pollutant load, temperature, humidity and light can lower energy use and maximize occupant comfort. With an increased awareness of cost and environmental effects of energy use, cross or natural ventilation has become an attractive method to lower energy use. Separated flow regions around such buildings are undesirable due to high concentration of pollutants, especially if the vents or dynamic windows for cross ventilation are situated in these regions. Outside pollutant load redistribution through vents can be regulated via flow separation control to minimize transport of pollutants into the building. Flow separation has been substantially reduced with the application of intelligent flow control tools developed at Syracuse University for flow around "silo" (turret) like structures. Similar flow control models can be introduced into buildings with cross ventilation for local external flow separation control. Initial experiments will be performed for turbulent flow over a rectangular block (scaled to be a mid-rise building) that has been configured with dynamic vents and unsteady suction actuators in a wind tunnel at various wind speeds.

  17. Middeck Active Control Experiment (MACE), phase A

    NASA Technical Reports Server (NTRS)

    Crawley, Edward F.; Deluis, Javier; Miller, David W.

    1989-01-01

    A rationale to determine which structural experiments are sufficient to verify the design of structures employing Controlled Structures Technology was derived. A survey of proposed NASA missions was undertaken to identify candidate test articles for use in the Middeck Active Control Experiment (MACE). The survey revealed that potential test articles could be classified into one of three roles: development, demonstration, and qualification, depending on the maturity of the technology and the mission the structure must fulfill. A set of criteria was derived that allowed determination of which role a potential test article must fulfill. A review of the capabilities and limitations of the STS middeck was conducted. A reference design for the MACE test article was presented. Computing requirements for running typical closed-loop controllers was determined, and various computer configurations were studied. The various components required to manufacture the structure were identified. A management plan was established for the remainder of the program experiment development, flight and ground systems development, and integration to the carrier. Procedures for configuration control, fiscal control, and safety, reliabilty, and quality assurance were developed.

  18. Nanoparticle Mediated Remote Control of Enzymatic Activity

    PubMed Central

    Knecht, Leslie D.; Ali, Nur; Wei, Yinan; Hilt, J. Zach; Daunert, Sylvia

    2012-01-01

    Nanomaterials have found numerous applications as tunable, remotely controlled platforms for drug delivery, hyperthermia cancer treatment, and various other biomedical applications. The basis for the interest lies in their unique properties achieved at the nanoscale that can be accessed via remote stimuli. These properties could then be exploited to simultaneously activate secondary systems that are not remotely actuatable. In this work, iron oxide nanoparticles are encapsulated in a bisacrylamide-crosslinked polyacrylamide hydrogel network along with a model dehalogenase enzyme, L-2-HADST. This thermophilic enzyme is activated at elevated temperatures and has been shown to have optimal activity at 70 °C. By exposing the Fe3O4 nanoparticles to a remote stimulus, an alternating magnetic field (AMF), enhanced system heating can be achieved, thus remotely activating the enzyme. The internal heating of the nanocomposite hydrogel network in the AMF results in a 2-fold increase in enzymatic activity as compared to the same hydrogel heated externally in a water bath, suggesting that the internal heating of the nanoparticles is more efficient than the diffusion limited heating of the water bath. This system may prove useful for remote actuation of biomedical and environmentally relevant enzymes and find applications in a variety of fields. PMID:22989219

  19. Method of fabricating a twisted composite superconductor

    NASA Technical Reports Server (NTRS)

    Brown, G. V.; Coles, W. D.; Laurence, J. C. (Inventor)

    1973-01-01

    A method of producing a twisted, stabilized wire or tube superconductor which can be used to wind electromagnets, armatures, rotors, field windings for motors and generators, and other magnetic devices which use a solenoid, toroidal, or other type winding is reported. At least one groove is formed along the length of a wire substrate which is then twisted into a helix and a layer of intermetallic superconducting material is formed in the groove. This layer can be formed by depositing the desired intermetallic compound into the groove or by diffusing one component of the superconductor into the groove formed in a substrate composed of the other component. The superconductor prepared by this method comprises a non-superconductor wire twisted into the shape of a helix, having at least one groove containing a layer of superconductor material along the length of the wire.

  20. Twist transition of nematic hyperbolic hedgehogs.

    PubMed

    James, Richard; Fukuda, Jun-ichi

    2014-04-01

    Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999)], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell. PMID:24827263

  1. Twisted bi-layer graphene: microscopic rainbows.

    PubMed

    Campos-Delgado, J; Algara-Siller, G; Santos, C N; Kaiser, U; Raskin, J-P

    2013-10-11

    Blue, pink, and yellow colorations appear from twisted bi-layer graphene (tBLG) when transferred to a SiO2 /Si substrate (SiO2 = 100 nm-thick). Raman and electron microscope studies reveal that these colorations appear for twist angles in the 9-15° range. Optical contrast simulations confirm that the observed colorations are related to the angle-dependent electronic properties of tBLG combined with the reflection that results from the layered structure tBLG/100 nm-thick SiO2 /Si. PMID:23606323

  2. Active Displacement Control of Active Magnetic Bearing System

    NASA Astrophysics Data System (ADS)

    Kertész, Milan; Kozakovič, Radko; Magdolen, Luboš; Masaryk, Michal

    2014-12-01

    The worldwide energy production nowadays is over 3400 GW while storage systems have a capacity of only 90 GW [1]. There is a good solution for additional storage capacity in flywheel energy storage systems (FES). The main advantage of FES is its relatively high efficiency especially with using the active magnetic bearing system. Therefore there exist good reasons for appropriate simulations and for creating a suitable magneto-structural control system. The magnetic bearing, including actuation, is simulated in the ANSYS parametric design language (APDL). APDL is used to create the loops of transient simulations where boundary conditions (BC) are updated based upon a "gap sensor" which controls the nodal position values of the centroid of the shaft and the current density inputs onto the copper windings.

  3. Understanding the brain by controlling neural activity

    PubMed Central

    Krug, Kristine; Salzman, C. Daniel; Waddell, Scott

    2015-01-01

    Causal methods to interrogate brain function have been employed since the advent of modern neuroscience in the nineteenth century. Initially, randomly placed electrodes and stimulation of parts of the living brain were used to localize specific functions to these areas. Recent technical developments have rejuvenated this approach by providing more precise tools to dissect the neural circuits underlying behaviour, perception and cognition. Carefully controlled behavioural experiments have been combined with electrical devices, targeted genetically encoded tools and neurochemical approaches to manipulate information processing in the brain. The ability to control brain activity in these ways not only deepens our understanding of brain function but also provides new avenues for clinical intervention, particularly in conditions where brain processing has gone awry. PMID:26240417

  4. Control concepts for active magnetic bearings

    NASA Technical Reports Server (NTRS)

    Siegwart, Roland; Vischer, D.; Larsonneur, R.; Herzog, R.; Traxler, Alfons; Bleuler, H.; Schweitzer, G.

    1992-01-01

    Active Magnetic Bearings (AMB) are becoming increasingly significant for various industrial applications. Examples are turbo-compressors, centrifuges, high speed milling and grinding spindles, vibration isolation, linear guides, magnetically levitated trains, vacuum and space applications. Thanks to the rapid progress and drastic cost reduction in power- and micro-electronics, the number of AMB applications is growing very rapidly. Industrial uses of AMBs leads to new requirements for AMB-actuators, sensor systems, and rotor dynamics. Especially desirable are new and better control concepts to meet demand such as low cost AMB, high stiffness, high performance, high robustness, high damping up to several kHz, vibration isolation, force-free rotation, and unbalance cancellation. This paper surveys various control concepts for AMBs and discusses their advantages and disadvantages. Theoretical and experimental results are presented.

  5. Gas turbine engine active clearance control

    NASA Technical Reports Server (NTRS)

    Deveau, Paul J. (Inventor); Greenberg, Paul B. (Inventor); Paolillo, Roger E. (Inventor)

    1985-01-01

    Method for controlling the clearance between rotating and stationary components of a gas turbine engine are disclosed. Techniques for achieving close correspondence between the radial position of rotor blade tips and the circumscribing outer air seals are disclosed. In one embodiment turbine case temperature modifying air is provided in flow rate, pressure and temperature varied as a function of engine operating condition. The modifying air is scheduled from a modulating and mixing valve supplied with dual source compressor air. One source supplies relatively low pressure, low temperature air and the other source supplies relatively high pressure, high temperature air. After the air has been used for the active clearance control (cooling the high pressure turbine case) it is then used for cooling the structure that supports the outer air seal and other high pressure turbine component parts.

  6. Resonant tunneling and intrinsic bistability in twisted graphene structures

    NASA Astrophysics Data System (ADS)

    Rodriguez-Nieva, J. F.; Dresselhaus, M. S.; Levitov, L. S.

    2016-08-01

    We predict that vertical transport in heterostructures formed by twisted graphene layers can exhibit a unique bistability mechanism. Intrinsically bistable I -V characteristics arise from resonant tunneling and interlayer charge coupling, enabling multiple stable states in the sequential tunneling regime. We consider a simple trilayer architecture, with the outer layers acting as the source and drain and the middle layer floating. Under bias, the middle layer can be either resonant or nonresonant with the source and drain layers. The bistability is controlled by geometric device parameters easily tunable in experiments. The nanoscale architecture can enable uniquely fast switching times.

  7. Active Aircraft Pylon Noise Control System

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H. (Inventor); Czech, Michael J (Inventor); Elmiligui, Alaa A. (Inventor)

    2015-01-01

    An active pylon noise control system for an aircraft includes a pylon structure connecting an engine system with an airframe surface of the aircraft and having at least one aperture to supply a gas or fluid therethrough, an intake portion attached to the pylon structure to intake a gas or fluid, a regulator connected with the intake portion via a plurality of pipes, to regulate a pressure of the gas or fluid, a plenum chamber formed within the pylon structure and connected with the regulator, and configured to receive the gas or fluid as regulated by the regulator, and a plurality of injectors in communication with the plenum chamber to actively inject the gas or fluid through the plurality of apertures of the pylon structure.

  8. Chern-Weil Construction for Twisted K-Theory

    NASA Astrophysics Data System (ADS)

    Gomi, Kiyonori; Terashima, Yuji

    2010-10-01

    We give a finite-dimensional and geometric construction of a Chern character for twisted K-theory, introducing a notion of connection on a twisted vectorial bundle which can be considered as a finite-dimensional approximation of a twisted family of Fredholm operators. Our construction is applicable to the case of any classes giving the twisting, and agrees with the Chern character of bundle gerbe modules in the case of torsion classes.

  9. The basic helix loop helix transcription factor Twist1 is a novel regulator of ATF4 in osteoblasts.

    PubMed

    Danciu, Theodora E; Li, Yan; Koh, Amy; Xiao, Guozhi; McCauley, Laurie K; Franceschi, Renny T

    2012-01-01

    Parathyroid hormone (PTH) is an essential regulator of endochondral bone formation and an important anabolic agent for the reversal of bone loss. PTH mediates its functions in part by regulating binding of the bone-related activating transcription factor 4 (ATF4) to the osteoblast-specific gene, osteocalcin. The basic helix-loop-helix (bHLH) factors Twist1 and Twist2 also regulate osteocalcin transcription in part through the interaction of the C-terminal "box" domain in these factors and Runx2. In this study, we discovered a novel function of PTH: its ability to dramatically decrease Twist1 transcription. Since ATF4 is a major regulator of the PTH response in osteoblasts, we assessed the mutual regulation between these factors and determined that Twist proteins and ATF4 physically interact in a manner that affects ATF4 DNA binding function. We mapped the interaction domain of Twist proteins to the C-terminal "box" domain and of ATF4, to the N-terminus. Furthermore, we demonstrate that Twist1 overexpression in osteoblasts attenuates ATF4 binding to the osteocalcin promoter in response to PTH. This study thus identifies Twist proteins as novel inhibitory binding partners of ATF4 and explores the functional significance of this interaction. PMID:21866569

  10. The basic helix loop helix transcription factor Twist1 is a novel regulator of ATF4 in osteoblasts

    PubMed Central

    Danciu, Theodora E.; Li, Yan; Koh, Amy; Xiao, Guozhi; McCauley, Laurie K.; Franceschi, Renny T.

    2011-01-01

    Parathyroid hormone (PTH) is an essential regulator of endochondral bone formation and an important anabolic agent for the reversal of bone loss. PTH mediates its functions in part by regulating binding of the bone-related activating transcription factor 4 (ATF4) to the osteoblast-specific gene, osteocalcin. The basic helix-loop-helix (bHLH) factors Twist1 and Twist2 also regulate osteocalcin transcription in part through the interaction of the C-terminal “box” domain in these factors and Runx2. In this study, we discovered a novel function of PTH: its ability to dramatically decrease Twist1 transcription. Since ATF4 is a major regulator of the PTH response in osteoblasts, we assessed the mutual regulation between these factors and determined that Twist proteins and ATF4 physically interact in a manner that affects ATF4 DNA binding function. We mapped the interaction domain of Twist proteins to the C-terminal “box” domain and of ATF4, to the N-terminus. Furthermore, we demonstrate that Twist1 overexpression in osteoblasts attenuates ATF4 binding to the osteocalcin promoter in response to PTH. This study thus identifies Twist proteins as novel inhibitory binding partners of ATF4 and explores the functional significance of this interaction. PMID:21866569

  11. Missile flight control using active flexspar actuators

    NASA Astrophysics Data System (ADS)

    Barrett, Ronald M.; Gross, R. Steven; Brozoski, Fred

    1995-05-01

    A new type of subsonic missile flight control surface using piezoelectric flexspar actuators is presented. The flexspar design uses an aerodynamic shell which is pivoted at the quarter-chord about a graphite main spar. The shell is pitched up and down by a piezoelectric bender element which is rigidly attached to a base mount and allowed to rotate freely at the tip. The element curvature, shell pitch deflection and torsional stiffness are modeled using laminated plate theory. A one-third scale TOW 2B missile model was used as a demonstration platform. A static wing of the missile was replaced with an active flexspar wing. The 1' X 2.7' active flight control surface was powered by a bi-morph bender with 5-mil PZT-5H sheets. Bench and wind tunnel testing showed good correlation between theory and experiment and static pitch deflections in excess of +/- 14 degree(s). A natural frequency of 78.5 rad/s with a break frequency of 157 rad/s was measured. Wind tunnel tests revealed no flutter or divergence tendencies. Maximum changes in lift coefficient were measured at (Delta) CL equals +/- .73 which indicates that terminal and initial missile load factors may be increased by approximately 3.1 and 12.6 g's respectively, leading to a greatly reduced turn radius of only 2,400 ft.

  12. Twist induces epithelial-mesenchymal transition and cell motility in breast cancer via ITGB1-FAK/ILK signaling axis and its associated downstream network.

    PubMed

    Yang, Jiajia; Hou, Yixuan; Zhou, Mingli; Wen, Siyang; Zhou, Jian; Xu, Liyun; Tang, Xi; Du, Yan-e; Hu, Ping; Liu, Manran

    2016-02-01

    Twist, a highly conserved basic Helix-Loop-Helix transcription factor, functions as a major regulator of epithelial-mesenchymal transition (EMT) and tumor metastasis. In different cell models, signaling pathways such as TGF-β, MAPK/ERK, WNT, AKT, JAK/STAT, Notch, and P53 have also been shown to play key roles in the EMT process, yet little is known about the signaling pathways regulated by Twist in tumor cells. Using iTRAQ-labeling combined with 2D LC-MS/MS analysis, we identified 194 proteins with significant changes of expression in MCF10A-Twist cells. These proteins reportedly play roles in EMT, cell junction organization, cell adhesion, and cell migration and invasion. ECM-receptor interaction, MAPK, PI3K/AKT, P53 and WNT signaling were found to be aberrantly activated in MCF10A-Twist cells. Ingenuity Pathways Analysis showed that integrin β1 (ITGB1) acts as a core regulator in linking integrin-linked kinase (ILK), Focal-adhesion kinase (FAK), MAPK/ERK, PI3K/AKT, and WNT signaling. Increased Twist and ITGB1 are associated with breast tumor progression. Twist transcriptionally regulates ITGB1 expression. Over-expression of ITGB1 or Twist in MCF10A led to EMT, activation of FAK/ILK, MAPK/ERK, PI3K/AKT, and WNT signaling. Knockdown of Twist or ITGB1 in BT549 and Hs578T cells decreased activity of FAK, ILK, and their downstream signaling, thus specifically impeding EMT and cell invasion. Knocking down ILK or inhibiting FAK, MAPK/ERK, or PI3K/AKT signaling also suppressed Twist-driven EMT and cell invasion. Thus, the Twist-ITGB1-FAK/ILK pathway and their downstream signaling network dictate the Twist-induced EMT process in human mammary epithelial cells and breast cancer cells. PMID:26693891

  13. Twist-mediated Epithelial-mesenchymal Transition Promotes Breast Tumor Cell Invasion via Inhibition of Hippo Pathway

    PubMed Central

    Wang, Yifan; Liu, Jingyi; Ying, Xuhua; Lin, Pengnian Charles; Zhou, Binhua P.

    2016-01-01

    Twist is a key transcription factor for Epithelial-mesenchymal transition (EMT), which is a cellular de-differentiation program that promotes invasion and metastasis, confers tumor cells with cancer stem cell (CSC)-like characteristics, and increases therapeutic resistance. However, the mechanisms that facilitate the functions of Twist remain unclear. Here we report that Twist overexpression increased expression of PAR1, an upstream regulator of the Hippo pathway; PAR1 promotes invasion, migration, and CSC-like properties in breast cancer by activating the transcriptional co-activator TAZ. Our study indicates that Hippo pathway inhibition is required for the increased migratory and invasiveness ability of breast cancer cells in Twist-mediated EMT. PMID:27094683

  14. Twist-mediated Epithelial-mesenchymal Transition Promotes Breast Tumor Cell Invasion via Inhibition of Hippo Pathway.

    PubMed

    Wang, Yifan; Liu, Jingyi; Ying, Xuhua; Lin, Pengnian Charles; Zhou, Binhua P

    2016-01-01

    Twist is a key transcription factor for Epithelial-mesenchymal transition (EMT), which is a cellular de-differentiation program that promotes invasion and metastasis, confers tumor cells with cancer stem cell (CSC)-like characteristics, and increases therapeutic resistance. However, the mechanisms that facilitate the functions of Twist remain unclear. Here we report that Twist overexpression increased expression of PAR1, an upstream regulator of the Hippo pathway; PAR1 promotes invasion, migration, and CSC-like properties in breast cancer by activating the transcriptional co-activator TAZ. Our study indicates that Hippo pathway inhibition is required for the increased migratory and invasiveness ability of breast cancer cells in Twist-mediated EMT. PMID:27094683

  15. Scattering of twisted relativistic electrons by atoms

    NASA Astrophysics Data System (ADS)

    Serbo, V.; Ivanov, I. P.; Fritzsche, S.; Seipt, D.; Surzhykov, A.

    2015-07-01

    The Mott scattering of high-energetic twisted electrons by atoms is investigated within the framework of the first Born approximation and Dirac's relativistic equation. Special emphasis is placed on the angular distribution and longitudinal polarization of the scattered electrons. In order to evaluate these angular and polarization properties we consider two experimental setups in which the twisted electron beam collides with either a single well-localized atom or macroscopic atomic target. Detailed relativistic calculations have been performed for both setups and for the electrons with kinetic energy from 10 to 1000 keV. The results of these calculations indicate that the emission pattern and polarization of outgoing electrons differ significantly from the scattering of plane-wave electrons and can be very sensitive to the parameters of the incident twisted beam. In particular, it is shown that the angular- and polarization-sensitive Mott measurements may reveal valuable information about both the transverse and longitudinal components of the linear momentum and the projection of the total angular momentum of twisted electron states. Thus, the Mott scattering emerges as a diagnostic tool for the relativistic vortex beams.

  16. Twisted Cyclic Cohomology and Modular Fredholm Modules

    NASA Astrophysics Data System (ADS)

    Rennie, Adam; Sitarz, Andrzej; Yamashita, Makoto

    2013-07-01

    Connes and Cuntz showed in [Comm. Math. Phys. 114 (1988), 515-526] that suitable cyclic cocycles can be represented as Chern characters of finitely summable semifinite Fredholm modules. We show an analogous result in twisted cyclic cohomology using Chern characters of modular Fredholm modules. We present examples of modular Fredholm modules arising from Podleś spheres and from SUq(2).

  17. Twisted Pair Of Insulated Wires Senses Moisture

    NASA Technical Reports Server (NTRS)

    Laue, Eric G.; Stephens, James B.

    1989-01-01

    Sensitivity of electronic moisture sensor to low levels of moisture increased by new electrode configuration. Moisture-sensing circuit described in "Low-Cost Humidity Sensor" (NPO-16544). New twisted pair of wires takes place of flat-plate capacitor in circuit. Configuration allows for thermal expansion and contraction of polymer while maintaining nearly constant area of contact between polymer and wires.

  18. The Physics of Somersaulting and Twisting.

    ERIC Educational Resources Information Center

    Frohlich, Cliff

    1980-01-01

    This is a discussion of the conservation of angular momentum of the human body engaged in somersaults and twists. The principle is also applied to a cat turning over in midair. The events occur in the absence of torques. Application of the maneuvers are suggested for astronauts. (SA)

  19. Operator constraints for twist-3 functions and Lorentz invariance properties of twist-3 observables

    DOE PAGESBeta

    Kanazawa, Koichi; Pitonyak, Daniel; Koike, Yuji; Metz, Andreas; Schlegel, Marc

    2016-03-14

    We investigate the behavior under Lorentz transformations of perturbative coefficient functions in a collinear twist-3 formalism relevant for high-energy observables including transverse polarization of hadrons. We argue that those perturbative coefficient functions can, a priori, acquire quite different yet Lorentz-invariant forms in various frames. This somewhat surprising difference can be traced back to a general dependence of the perturbative coefficient functions on light cone vectors which are introduced by the twist-3 factorization formulas and which are frame-dependent. One can remove this spurious frame dependence by invoking so-called Lorentz invariance relations (LIRs) between twist-3 parton correlation functions. Some of those relationsmore » for twist-3 distribution functions were discussed in the literature before. In this paper we derive the corresponding LIRs for twist-3 fragmentation functions. We explicitly demonstrate that these LIRs remove the light cone vector dependence by considering transverse spin observables in the single-inclusive production of hadrons in lepton-nucleon collisions, ℓN→hX. Furthermore, with the LIRs in hand, we also show that twist-3 observables in general can be written solely in terms of three-parton correlation functions.« less

  20. Operator constraints for twist-3 functions and Lorentz invariance properties of twist-3 observables

    NASA Astrophysics Data System (ADS)

    Kanazawa, Koichi; Koike, Yuji; Metz, Andreas; Pitonyak, Daniel; Schlegel, Marc

    2016-03-01

    We investigate the behavior under Lorentz transformations of perturbative coefficient functions in a collinear twist-3 formalism relevant for high-energy observables including transverse polarization of hadrons. We argue that those perturbative coefficient functions can, a priori, acquire quite different yet Lorentz-invariant forms in various frames. This somewhat surprising difference can be traced back to a general dependence of the perturbative coefficient functions on light cone vectors which are introduced by the twist-3 factorization formulas and which are frame-dependent. One can remove this spurious frame dependence by invoking so-called Lorentz invariance relations (LIRs) between twist-3 parton correlation functions. Some of those relations for twist-3 distribution functions were discussed in the literature before. In this paper we derive the corresponding LIRs for twist-3 fragmentation functions. We explicitly demonstrate that these LIRs remove the light cone vector dependence by considering transverse spin observables in the single-inclusive production of hadrons in lepton-nucleon collisions, ℓN →h X . With the LIRs in hand, we also show that twist-3 observables in general can be written solely in terms of three-parton correlation functions.

  1. Amplitude Scaling of Active Separation Control

    NASA Technical Reports Server (NTRS)

    Stalnov, Oksana; Seifert, Avraham

    2010-01-01

    Three existing and two new excitation magnitude scaling options for active separation control at Reynolds numbers below one Million. The physical background for the scaling options was discussed and their relevance was evaluated using two different sets of experimental data. For F+ approx. 1, 2D excitation: a) The traditional VR and C(mu) - do not scale the data. b) Only the Re*C(mu) is valid. This conclusion is also limited for positive lift increment.. For F+ > 10, 3D excitation, the Re corrected C(mu), the St corrected velocity ratio and the vorticity flux coefficient, all scale the amplitudes equally well. Therefore, the Reynolds weighted C(mu) is the preferred choice, relevant to both excitation modes. Incidence also considered, using Ue from local Cp.

  2. Torque correlation length and stochastic twist dynamics of DNA.

    PubMed

    Banigan, Edward J; Marko, John F

    2014-06-01

    We introduce a short correlation length for torque in twisting-stiff biomolecules, which is necessary for the physical property that torque fluctuations be finite in amplitude. We develop a nonequilibrium theory of dynamics of DNA twisting which predicts two crossover time scales for temporal torque correlations in single-molecule experiments. Bending fluctuations can be included, and at linear order we find that they do not affect the twist dynamics. However, twist fluctuations affect bending, and we predict the spatial inhomogeneity of twist, torque, and buckling arising in nonequilibrium "rotor-bead" experiments. PMID:25019813

  3. Ribosome-dependent activation of stringent control.

    PubMed

    Brown, Alan; Fernández, Israel S; Gordiyenko, Yuliya; Ramakrishnan, V

    2016-06-01

    In order to survive, bacteria continually sense, and respond to, environmental fluctuations. Stringent control represents a key bacterial stress response to nutrient starvation that leads to rapid and comprehensive reprogramming of metabolic and transcriptional patterns. In general, transcription of genes for growth and proliferation is downregulated, while those important for survival and virulence are upregulated. Amino acid starvation is sensed by depletion of the aminoacylated tRNA pools, and this results in accumulation of ribosomes stalled with non-aminoacylated (uncharged) tRNA in the ribosomal A site. RelA is recruited to stalled ribosomes and activated to synthesize a hyperphosphorylated guanosine analogue, (p)ppGpp, which acts as a pleiotropic secondary messenger. However, structural information about how RelA recognizes stalled ribosomes and discriminates against aminoacylated tRNAs is missing. Here we present the cryo-electron microscopy structure of RelA bound to the bacterial ribosome stalled with uncharged tRNA. The structure reveals that RelA utilizes a distinct binding site compared to the translational factors, with a multi-domain architecture that wraps around a highly distorted A-site tRNA. The TGS (ThrRS, GTPase and SpoT) domain of RelA binds the CCA tail to orient the free 3' hydroxyl group of the terminal adenosine towards a β-strand, such that an aminoacylated tRNA at this position would be sterically precluded. The structure supports a model in which association of RelA with the ribosome suppresses auto-inhibition to activate synthesis of (p)ppGpp and initiate the stringent response. Since stringent control is responsible for the survival of pathogenic bacteria under stress conditions, and contributes to chronic infections and antibiotic tolerance, RelA represents a good target for the development of novel antibacterial therapeutics. PMID:27279228

  4. Active Control of Wind Tunnel Noise

    NASA Technical Reports Server (NTRS)

    Hollis, Patrick (Principal Investigator)

    1991-01-01

    The need for an adaptive active control system was realized, since a wind tunnel is subjected to variations in air velocity, temperature, air turbulence, and some other factors such as nonlinearity. Among many adaptive algorithms, the Least Mean Squares (LMS) algorithm, which is the simplest one, has been used in an Active Noise Control (ANC) system by some researchers. However, Eriksson's results, Eriksson (1985), showed instability in the ANC system with an ER filter for random noise input. The Restricted Least Squares (RLS) algorithm, although computationally more complex than the LMS algorithm, has better convergence and stability properties. The ANC system in the present work was simulated by using an FIR filter with an RLS algorithm for different inputs and for a number of plant models. Simulation results for the ANC system with acoustic feedback showed better robustness when used with the RLS algorithm than with the LMS algorithm for all types of inputs. Overall attenuation in the frequency domain was better in the case of the RLS adaptive algorithm. Simulation results with a more realistic plant model and an RLS adaptive algorithm showed a slower convergence rate than the case with an acoustic plant as a delay plant. However, the attenuation properties were satisfactory for the simulated system with the modified plant. The effect of filter length on the rate of convergence and attenuation was studied. It was found that the rate of convergence decreases with increase in filter length, whereas the attenuation increases with increase in filter length. The final design of the ANC system was simulated and found to have a reasonable convergence rate and good attenuation properties for an input containing discrete frequencies and random noise.

  5. Missile flight control using active flexspar actuators

    NASA Astrophysics Data System (ADS)

    Barrett, Ron; Gross, R. Steven; Brozoski, Fred

    1996-04-01

    A new type of subsonic missile flight control surface using piezoelectric flexspar actuators is presented. The flexspar design uses an aerodynamic shell which is pivoted at the quarter-chord about a graphite main spar. The shell is pitched up and down by a piezoelectric bender element which is rigidly attached to a base mount and allowed to rotate freely at the tip. The element curvature, shell pitch deflection and torsional stiffness are modeled using laminated plate theory. A one-third scale TOW 2B missile model was used as a demonstration platform. A static wing of the missile was replaced with an active flexspar wing. The 1 in 0964-1726/5/2/002/img1 2.7 in active flight control surface was powered by a bimorph bender with 5 mil PZT-5H sheets. Bench and wind tunnel testing showed good correlation between theory and experiment and static pitch deflections in excess of 0964-1726/5/2/002/img2. A natural frequency of 78.5 rad 0964-1726/5/2/002/img3 with a break frequency of 157 rad 0964-1726/5/2/002/img3 was measured. Wind tunnel tests revealed no flutter or divergence tendencies. Maximum changes in lift coefficient were measured at 0964-1726/5/2/002/img5 which indicates that terminal and initial missile load factors may be increased by approximately 3.1 and 12.6 g respectively, leading to a greatly reduced turn radius of only 2400 ft.

  6. Active Shielding and Control of Environmental Noise

    NASA Technical Reports Server (NTRS)

    Tsynkov, S. V.

    2001-01-01

    In the framework of the research project supported by NASA under grant # NAG-1-01064, we have studied the mathematical aspects of the problem of active control of sound, i.e., time-harmonic acoustic disturbances. The foundations of the methodology are described in our paper [1]. Unlike. many other existing techniques, the approach of [1] provides for the exact volumetric cancellation of the unwanted noise on a given predetermined region airspace, while leaving unaltered those components of the total acoustic field that are deemed as friendly. The key finding of the work is that for eliminating the unwanted component of the acoustic field in a given area, one needs to know relatively little; in particular, neither the locations nor structure nor strength of the exterior noise sources need to be known. Likewise, there is no need to know the volumetric properties of the supporting medium across which the acoustic signals propagate, except, maybe, in a narrow area of space near the perimeter of the protected region. The controls are built based solely on the measurements performed on the perimeter of the domain to be shielded; moreover, the controls themselves (i.e., additional sources) are concentrated also only on or near this perimeter. Perhaps as important, the measured quantities can refer to the total acoustic field rather than to its unwanted component only, and the methodology can automatically distinguish between the two. In [1], we have constructed the general solution for controls. The apparatus used for deriving this general solution is closely connected to the concepts of generalized potentials and boundary projections of Calderon's type. For a given total wave field, the application of a Calderon's projection allows one to definitively tell between its incoming and outgoing components with respect to a particular domain of interest, which may have arbitrary shape. Then, the controls are designed so that they suppress the incoming component for the domain

  7. Phase twisted modes and current reversals in a lattice model of waveguide arrays with nonlinear coupling

    SciTech Connect

    Oester, Michael; Johansson, Magnus

    2005-02-01

    We consider a lattice model for waveguide arrays embedded in nonlinear Kerr media. Inclusion of nonlinear coupling results in many phenomena involving complex, phase-twisted, stationary modes. The norm (Poynting power) current of stable plane-wave solutions can be controlled in magnitude and direction, and may be reversed without symmetry-breaking perturbations. Also stable localized phase-twisted modes with zero current exist, which for particular parameter values may be compact and expressed analytically. The model also describes coupled Bose-Einstein condensates.

  8. Prediction and measurement of composite tube twist and bending due to thermal loading

    NASA Astrophysics Data System (ADS)

    Bluth, A. Marcel; Tucker, James R.; Thompson, Troy

    2013-09-01

    Composite materials are applied in precision optical metering structures because of their low thermal expansion properties in concert with high specific stiffness. Twisting and bending of long composite tubes, such as the secondary mirror support structure for the JWST telescope, requires control and verification. A stochastic modeling method was applied that simulates the manufacturing process variability and estimates ranges for expected twist and bend over the tube length from ambient to cryogenic temperatures. A development strut for the JWST secondary mirror support structure was fabricated and a metrology system was designed and implemented that measured the bend and twist response from ambient to 30 K. Modeling methods and predictions are outlined. The test metrology and results are summarized, along with a comparison between test and prediction.

  9. Actively controlled thin-shell space optics

    NASA Astrophysics Data System (ADS)

    Denoyer, Keith K.; Flint, Eric M.; Main, John A.; Lindler, Jason E.

    2003-08-01

    Increasingly, scientific and military missions require the use of space-based optical systems. For example, new capabilities are required for imaging terrestrial like planets, for surveillance, and for directed energy applications. Given the difficulties in producing and launching large optics, it is doubtful that refinements of conventional technology will meet future needs, particularly in a cost-effective manner. To meet this need, recent research has been investigating the feasibility of a new class of ultra-lightweight think-skin optical elements that combine recent advances in lightweight thermally formed materials, active materials, and novel sensing and control architectures. If successful, the approach may lead to an order of magnitude reduction in space optics areal density, improved large scale manufacturing capability, and dramatic reductions in manufacturing and launch costs. In a recent effort, a one meter thin-film mirror like structure was fabricated. This paper provides an overview of tools used to model and simulate this structure as well as results from structural dynamic testing. In addition, progress in the area of non-contact global shape control using smart materials is presented.

  10. High performance composites with active stiffness control.

    PubMed

    Tridech, Charnwit; Maples, Henry A; Robinson, Paul; Bismarck, Alexander

    2013-09-25

    High performance carbon fiber reinforced composites with controllable stiffness could revolutionize the use of composite materials in structural applications. Here we describe a structural material, which has a stiffness that can be actively controlled on demand. Such a material could have applications in morphing wings or deployable structures. A carbon fiber reinforced-epoxy composite is described that can undergo an 88% reduction in flexural stiffness at elevated temperatures and fully recover when cooled, with no discernible damage or loss in properties. Once the stiffness has been reduced, the required deformations can be achieved at much lower actuation forces. For this proof-of-concept study a thin polyacrylamide (PAAm) layer was electrocoated onto carbon fibers that were then embedded into an epoxy matrix via resin infusion. Heating the PAAm coating above its glass transition temperature caused it to soften and allowed the fibers to slide within the matrix. To produce the stiffness change the carbon fibers were used as resistance heating elements by passing a current through them. When the PAAm coating had softened, the ability of the interphase to transfer load to the fibers was significantly reduced, greatly lowering the flexural stiffness of the composite. By changing the moisture content in PAAm fiber coating, the temperature at which the PAAm softens and the composites undergo a reduction in stiffness can be tuned. PMID:23978266

  11. A twist in zygotic reprogramming.

    PubMed

    Messerschmidt, Daniel M

    2016-02-01

    The first hours of mammalian embryogenesis are devoted to extensive epigenetic reprogramming. One hallmark is active demethylation of the paternal genome by Tet (ten-eleven translocation) enzymes. However, the process is now shown to be Tet-independent at first, with Tet enzymes only counteracting hitherto underappreciated de novo DNA methylation activity in later zygotic stages. PMID:26820436

  12. Current sensing using circularly birefringent twisted solid-core photonic crystal fiber.

    PubMed

    Beravat, R; Wong, G K L; Xi, X M; Frosz, M H; St J Russell, P

    2016-04-01

    Continuously twisted solid-core photonic crystal fiber (PCF) exhibits pure circular birefringence (optical activity), making it ideal for current sensors based on the Faraday effect. By numerical analysis, we identify the PCF geometry for which the circular birefringence (which scales linearly with twist rate) is a maximum. For silica-air PCF, this occurs at a shape parameter (diameter-to-spacing ratio of the hollow channels) of 0.37 and a scale parameter (spacing-to-wavelength) of 1.51. This result is confirmed experimentally by testing a range of different structures. To demonstrate the effectiveness of twisted PCF as a current sensor, a length of fiber is placed on the axis of a 7.6 cm long solenoid, and the Faraday rotation is measured at different values of dc current. The system is then used to chart the wavelength dependence of the Verdet constant. PMID:27192315

  13. Robust controllers for the Middeck Active Control Experiment using Popov controller synthesis

    NASA Technical Reports Server (NTRS)

    How, Jonathan P.; Hall, Steven R.

    1993-01-01

    Recent work in robust control with real parameter uncertainties has focused on absolute stability and its connections to real mu theory. In particular, the research has investigated the Popov stability criterion and its associated Lur'e-Postnikov Liapunov functions. State space representations of this Popov stability analysis tests are included in an H2 design formulation to provide a powerful technique for robust controller synthesis. This synthesis approach uses a state space optimization procedure to design controllers that minimize an overbound of an H2 cost functional and satisfy stability analysis tests based on the Popov multiplier. The controller and stability multiplier coefficients are optimized simultaneously, which avoids the iteration and curve-fitting procedures required by the D-K algorithm of mu synthesis. While previous work has demonstrated this synthesis approach on benchmark control problems, the purpose of this paper is to use Popov controller synthesis to design robust compensators for the Middeck Active Control Experiment (MACE).

  14. Open architecture controller activities in Technology Enabling Agile Manufacturing (TEAM)

    NASA Astrophysics Data System (ADS)

    McCue, Howard K.

    1997-01-01

    As part of its manufacturing initiative, TEAM is actively involved in open architecture controller activities. WIthin the TEAM community of members, TEAM is developing an open architecture controller requirements document and an open architecture controller application programming interface document. In addition, TEAM is also evaluating early open architecture controllers in a shop floor environment.

  15. Twisted, multifilament Nb3Sn superconductive ribbon

    NASA Technical Reports Server (NTRS)

    Coles, W. D.

    1972-01-01

    An experimental study of superconductor stabilization has resulted in the successful application of the concepts of filamentary structure and conductor twist to Nb3Sn ribbon. The Nb3Sn is formed in parallel, helical paths, which are continuous around the ribbon. Short lengths (12-18cm) of 1.27 cm wide superconductive ribbon were produced. The filamentary and twist characteristics are incorporated in the ribbon by means of an inert mask formed on the ribbon surface early in the fabrication process. Diffusion reaction of the niobium and tin is prevented at the filament boundaries. Described are the conductor methods of fabrication, and test results obtained. The technology required to adapt the processes for the production of long lengths of ribbon is available.

  16. HREM of general and twist grain boundaries.

    SciTech Connect

    Merkle, K. L.; Thompson, L. J.

    1999-03-10

    The observation of atomic-scale structures of grain boundaries (GBs) via axial illumination HREM has been largely restricted to tilt GBs, due to the requirement that the electron beam be parallel to a low-index zone axis on both sides of the interface. This condition can be fulfilled for all tilt GBs with disorientation about a low-index direction. The information obtained through HREM studies in many materials has brought important insights concerning the atomic-scale structure of such boundaries. However, it is well known that tilt GBs occupy only an infinitesimally small fraction of the 5-dimensional phase space which describes the macroscopic geometry of all GBs. Therefore, although tilt GBs are very important due to their low energy, it would be useful to also study twist GBs and general GBs that contain twist and tilt components.

  17. TWISTING, RECONNECTING MAGNETOSPHERES AND MAGNETAR SPINDOWN

    SciTech Connect

    Parfrey, Kyle; Beloborodov, Andrei M.; Hui, Lam

    2012-07-20

    We present the first simulations of evolving, strongly twisted magnetar magnetospheres. Slow shearing of the magnetar crust is seen to lead to a series of magnetospheric expansion and reconnection events, corresponding to X-ray flares and bursts. The axisymmetric simulations include rotation of the neutron star and the magnetic wind through the light cylinder. We study how the increasing twist affects the spindown rate of the star, finding that a dramatic increase in spindown occurs. Particularly spectacular are explosive events caused by the sudden opening of large amounts of overtwisted magnetic flux, which may be associated with the observed giant flares. These events are accompanied by a short period of ultrastrong spindown, resulting in an abrupt increase in spin period, such as was observed in the giant flare of SGR 1900+14.

  18. Terahertz conductivity of twisted bilayer graphene.

    PubMed

    Zou, Xingquan; Shang, Jingzhi; Leaw, Jianing; Luo, Zhiqiang; Luo, Liyan; La-o-Vorakiat, Chan; Cheng, Liang; Cheong, S A; Su, Haibin; Zhu, Jian-Xin; Liu, Yanpeng; Loh, Kian Ping; Castro Neto, A H; Yu, Ting; Chia, Elbert E M

    2013-02-01

    Using terahertz time-domain spectroscopy, the real part of optical conductivity [σ(1)(ω)] of twisted bilayer graphene was obtained at different temperatures (10-300 K) in the frequency range 0.3-3 THz. On top of a Drude-like response, we see a strong peak in σ(1)(ω) at ~2.7 THz. We analyze the overall Drude-like response using a disorder-dependent (unitary scattering) model, then attribute the peak at 2.7 THz to an enhanced density of states at that energy, which is caused by the presence of a van Hove singularity arising from a commensurate twisting of the two graphene layers. PMID:23432306

  19. A Pentacene with a 144 Twist

    SciTech Connect

    Lu,J.; Ho, D.; Vogelaar, N.; Krami, C.; Pascal, R.

    2004-01-01

    9, 10, 11, 20, 21, 22-Hexaphenyltetrabenzo[a, c, l, n]pentacene (1) was prepared by the reaction of 1, 3-diphenylphenanthro[9, 10-c]furan with the bisaryne equivalent generated from 1, 2, 4, 5-tetrabromo-3, 6-diphenylbenzene in the presence of n-butyllithium, followed by deoxygenation of the double adduct with low-valent titanium. The X-ray structure of 1 shows it to be the most highly twisted polycyclic aromatic hydrocarbon known, with an end-to-end twist of 143.6 degrees. Compound 1 was resolved by chromatography on a chiral support, and the pure enantiomers have specific rotations in excess of 7000 degrees, but the molecule racemizes slowly at 25 C (t{sub 1/2} = 9.3 h, {Delta}G{sup {double_dagger}}{sub rac} = 23.8 kcal/mol).

  20. An IPMC-enabled bio-inspired bending/twisting fin for underwater applications

    NASA Astrophysics Data System (ADS)

    Palmre, Viljar; Hubbard, Joel J.; Fleming, Maxwell; Pugal, David; Kim, Sungjun; Kim, Kwang J.; Leang, Kam K.

    2013-01-01

    This paper discusses the design, fabrication, and characterization of an ionic polymer-metal composite (IPMC) actuator-based bio-inspired active fin capable of bending and twisting motion. It is pointed out that IPMC strip actuators are used in the simple cantilever configuration to create simple bending (flapping-like) motion for propulsion in underwater autonomous systems. However, the resulting motion is a simple 1D bending and performance is rather limited. To enable more complex deformation, such as the flapping (pitch and heaving) motion of real pectoral and caudal fish fins, a new approach which involves molding or integrating IPMC actuators into a soft boot material to create an active control surface (called a ‘fin’) is presented. The fin can be used to realize complex deformation depending on the orientation and placement of the actuators. In contrast to previously created IPMCs with patterned electrodes for the same purpose, the proposed design avoids (1) the more expensive process of electroless plating platinum all throughout the surface of the actuator and (2) the need for specially patterning the electrodes. Therefore, standard shaped IPMC actuators such as those with rectangular dimensions with varying thicknesses can be used. One unique advantage of the proposed structural design is that custom shaped fins and control surfaces can be easily created without special materials processing. The molding process is cost effective and does not require functionalizing or ‘activating’ the boot material similar to creating IPMCs. For a prototype fin (90 mm wide × 60 mm long × 1.5 mm thick), the measured maximum tip displacement was approximately 44 mm and the twist angle of the fin exceeded 10°. Lift and drag measurements in water where the prototype fin with an airfoil profile was dragged through water at a velocity of 21 cm s-1 showed that the lift and drag forces can be affected by controlling the IPMCs embedded into the fin structure. These

  1. Aerodynamic Control using Distributed Active Bleed

    NASA Astrophysics Data System (ADS)

    Kearney, John; Glezer, Ari

    2015-11-01

    The global aerodynamic loads on a stationary and pitching airfoil at angles of attack beyond the static and dynamic stall margins, respectively are controlled in wind tunnel experiments using regulated distributed bleed driven by surface pressure differences. High-speed PIV and proper orthogonal decomposition of the vorticity flux on the static airfoil show that the bleed engenders trains of discrete vortices that advect along the surface and are associated with a local instability that is manifested by a time-averaged bifurcation of the vorticity layer near the bleed outlets and alters the vorticity flux over the airfoil and thereby the aerodynamic loads. Active bleed is used on a dynamically pitching airfoil (at reduced frequencies up to k = 0.42) to modulate the evolution of vorticity concentrations during dynamic stall. Time-periodic bleed improved the pitch stability by reducing adverse pitching moment (``negative damping'') that can precipitate structural instabilities. At the same time, the maintains the cycle-average loads to within 5% of the base flow levels by segmenting the vorticity layer during upstroke and promoting early flow attachment during downstroke segments of the pitch cycle. Supported by Georgia Tech VLRCOE.

  2. Probing transmembrane mechanical coupling and cytomechanics using magnetic twisting cytometry

    NASA Technical Reports Server (NTRS)

    Wang, N.; Ingber, D. E.

    1995-01-01

    We recently developed a magnetic twisting cytometry technique that allows us to apply controlled mechanical stresses to specific cell surface receptors using ligand-coated ferromagnetic microbeads and to simultaneously measure the mechanical response in living cells. Using this technique, we have previously shown the following: (i) beta 1 integrin receptors mediate mechanical force transfer across the cell surface and to the cytoskeleton, whereas other transmembrane receptors (e.g., scavenger receptors) do not; (ii) cytoskeletal stiffness increases in direct proportion to the level of stress applied to integrins; and (iii) the slope of this linear stiffening response differs depending on the shape of the cell. We now show that different integrins (beta 1, alpha V beta 3, alpha V, alpha 5, alpha 2) and other transmembrane receptors (scavenger receptor, platelet endothelial cell adhesion molecule) differ in their ability to mediate force transfer across the cell surface. In addition, the linear stiffening behavior previously observed in endothelial cells was found to be shared by other cell types. Finally, we demonstrate that dynamic changes in cell shape that occur during both cell spreading and retraction are accompanied by coordinate changes in cytoskeletal stiffness. Taken together, these results suggest that the magnetic twisting cytometry technique may be a powerful and versatile tool for studies analyzing the molecular basis of transmembrane mechanical coupling to the cytoskeleton as well as dynamic relations between changes in cytoskeletal structure and alterations in cell form and function.

  3. Twisted toroidal vortex solitons in inhomogeneous media with repulsive nonlinearity.

    PubMed

    Kartashov, Yaroslav V; Malomed, Boris A; Shnir, Yasha; Torner, Lluis

    2014-12-31

    Toroidal modes in the form of so-called Hopfions, with two independent winding numbers, a hidden one (twist s), which characterizes a circular vortex thread embedded into a three-dimensional soliton, and the vorticity around the vertical axis (m), appear in many fields, including field theory, ferromagnetics, and semi- and superconductors. Such topological states are normally generated in multicomponent systems, or as trapped quasilinear modes in toroidal potentials. We uncover that stable solitons with this structure can be created, without any linear potential, in the single-component setting with the strength of repulsive nonlinearity growing fast enough from the center to the periphery, for both steep and smooth modulation profiles. Toroidal modes with s=1 and vorticity m=0, 1, 2 are produced. They are stable for m≤1, and do not exist for s>1. An approximate analytical solution is obtained for the twisted ring with s=1, m=0. Under the application of an external torque, it rotates like a solid ring. The setting can be implemented in a Bose-Einstein condensate (BEC) by means of the Feshbach resonance controlled by inhomogeneous magnetic fields. PMID:25615341

  4. Ferromagnetic nanoparticles suspensions in twisted nematic

    NASA Astrophysics Data System (ADS)

    Cîrtoaje, Cristina; Petrescu, Emil; Stan, Cristina; Creangă, Dorina

    2016-05-01

    Ferromagnetic nanoparticles insertions in nematic liquid crystals (NLC) in twisted configuration are studied and a theoretical model is proposed to explain the results. Experimental observation revealed that nanoparticles tend to overcrowd in long strings parallel to the rubbing direction of the alignment substrate of the LC cell. Their behavior under external field was studied and their interaction with their nematic host is described using elastic continuum theory.

  5. TWISTED MAGNETIC FLUX TUBES IN THE SOLAR WIND

    SciTech Connect

    Zaqarashvili, Teimuraz V.; Vörös, Zoltán; Narita, Yasuhito; Bruno, Roberto

    2014-03-01

    Magnetic flux tubes in the solar wind can be twisted as they are transported from the solar surface, where the tubes are twisted due to photospheric motions. It is suggested that the twisted magnetic tubes can be detected as the variation of total (thermal+magnetic) pressure during their passage through the observing satellite. We show that the total pressure of several observed twisted tubes resembles the theoretically expected profile. The twist of the isolated magnetic tube may explain the observed abrupt changes of magnetic field direction at tube walls. We have also found some evidence that the flux tube walls can be associated with local heating of the plasma and elevated proton and electron temperatures. For the tubes aligned with the Parker spiral, the twist angle can be estimated from the change of magnetic field direction. Stability analysis of twisted tubes shows that the critical twist angle of the tube with a homogeneous twist is 70°, but the angle can further decrease due to the motion of the tube with respect to the solar wind stream. The tubes with a stronger twist are unstable to the kink instability, therefore they probably cannot reach 1 AU.

  6. Active control of buckling of flexible beams

    NASA Technical Reports Server (NTRS)

    Baz, A.; Tampe, L.

    1989-01-01

    Mathematical models are presented that simulate the dynamic characteristics of shape memory alloy actuators made of nickel-titanium alloy (Nitinol) controlling the buckling of compressive structural members. A closed-loop computer-controlled system has been designed, based on the proposed mathematical models, and has been implemented to control the buckling of simple beams. The performance of the computer-controlled system is evaluated experimentally and compared with the theoretical predictions to validate the developed models. The results emphasized the importance of buckling control and suggest the potential of shape memory alloy actuators as attractive means for controlling structural deformation in a simple and reliable way.

  7. Twisted bilayer graphene with interlayer potential asymmetry

    NASA Astrophysics Data System (ADS)

    Moon, Pilkyung; Son, Young-Woo; Koshino, Mikito

    A twisted stack of two graphene layers (twisted bilayer graphene) exhibits an extremely long potential period arising from the moiré interference between the layers. We investigate the band structure and optical absorption spectrum of twisted bilayer graphenes with changing interlayer bias and Fermi energy simultaneously. We show that the interlayer bias lifts the degeneracy of the superlattice Dirac point, while the amount of the Dirac point shift is significantly suppressed in small rotation angles, and even becomes opposite to the applied bias, by the interlayer interaction. In addition, we show that the spectroscopic features are highly sensitive to the interlayer bias and the Fermi energy, and widely tunable by the external field effect. P.M. acknowledges the support of NYU Shanghai and the NYU-ECNU Institute of Physics at NYU Shanghai. Y.-W.S. was supported by the NRF of Korea grant funded by the MSIP. M.K. was funded by JSPS Grantin-Aid for Scientific Research.

  8. Twist transition of nematic hyperbolic hedgehogs

    NASA Astrophysics Data System (ADS)

    James, Richard; Fukuda, Jun-ichi

    2014-04-01

    Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999), 10.1080/026782999204840], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell.

  9. Active controllers and the time duration to learn a task

    NASA Technical Reports Server (NTRS)

    Repperger, D. W.; Goodyear, C.

    1986-01-01

    An active controller was used to help train naive subjects involved in a compensatory tracking task. The controller is called active in this context because it moves the subject's hand in a direction to improve tracking. It is of interest here to question whether the active controller helps the subject to learn a task more rapidly than the passive controller. Six subjects, inexperienced to compensatory tracking, were run to asymptote root mean square error tracking levels with an active controller or a passive controller. The time required to learn the task was defined several different ways. The results of the different measures of learning were examined across pools of subjects and across controllers using statistical tests. The comparison between the active controller and the passive controller as to their ability to accelerate the learning process as well as reduce levels of asymptotic tracking error is reported here.

  10. Quasi-modal vibration control by means of active control bearings

    NASA Technical Reports Server (NTRS)

    Nonami, K.; Fleming, D. P.

    1986-01-01

    This paper investigates a design method of an active control bearing system with only velocity feedback. The study provides a new quasi-modal control method for a control system design of an active control bearing system in which feedback coefficients are determined on the basis of a modal analysis. Although the number of sensors and actuators is small, this quasi-modal control method produces a control effect close to an ideal modal control.

  11. Enhanced Generation of Myeloid Lineages in Hematopoietic Differentiation from Embryonic Stem Cells by Silencing Transcriptional Repressor Twist-2

    PubMed Central

    Sharabi, Andrew B.; Lee, Sung-Hyung; Goodell, Margaret A.; Huang, Xue F.

    2009-01-01

    Abstract The self-renewal and multilineage differentiation of embryonic stem cells (ESC) is largely governed by transcription factors or repressors. Extensive efforts have focused on elucidating critical factors that control the differentiation of specific cell lineages, for instance, myeloid lineages in hematopoietic development. In this study, we found that Twist-2, a basic helix-loop-helix (bHLH) transcription factor, plays a critical role in inhibiting the differentiation of ESC. Murine ES cells, in which Twist-2 expression is silenced by lentivirally delivered shRNA, exhibit an enhanced formation of primary embryoid bodies (EB) and enhanced differentiation into mesodermally derived hematopoietic colonies. Furthermore, Twist-2 silenced (LV-siTwist-2) ESC display significantly increased generation of myeloid lineages (Gr-1+ and F4/80+ cells) during in vitro hematopoietic differentiation. Treatment with the Toll-like receptor (TLR) 4 ligand synergistically stimulates the generation of primary EB formation as well as of hematopoietic progenitors differentiated from LV-siTwist-2 ES cells. Thus, this study reveals the critical role of the transcriptional repressor Twist-2 in regulating the development of myeloid lineage in hematopoietic differentiation from ESC. This study also suggests a potential strategy for directional differentiation of ESC by inhibiting a transcriptional repressor. PMID:20025523

  12. Low Activity Waste Feed Process Control Strategy

    SciTech Connect

    STAEHR, T.W.

    2000-06-14

    The primary purpose of this document is to describe the overall process control strategy for monitoring and controlling the functions associated with the Phase 1B high-level waste feed delivery. This document provides the basis for process monitoring and control functions and requirements needed throughput the double-shell tank system during Phase 1 high-level waste feed delivery. This document is intended to be used by (1) the developers of the future Process Control Plan and (2) the developers of the monitoring and control system.

  13. A twist in the tale

    PubMed Central

    Malhotra, Rishi; Daniel, Rejoo; Besarovic, Sanja

    2013-01-01

    A 4-year-old girl presented with retching and abdominal colic and was initially diagnosed with gastroenteritis. However, progressive pain and epigastric distension led to a surgical review and she was discovered on CT scanning to have a gastric volvulus. She required urgent laparotomy to decompress the stomach and repair a perforation on the lesser curvature. Her recovery was complicated by sepsis and reperforation necessitating further laparotomy, at which time she also underwent gastropexy. The patient required long-term jejunal feeding in the hospital and at home before finally returning to normal diet and activity. PMID:24163405

  14. Active flutter control for flexible vehicles, volume 1

    NASA Technical Reports Server (NTRS)

    Mahesh, J. K.; Garrard, W. L.; Stones, C. R.; Hausman, P. D.

    1979-01-01

    An active flutter control methodology based on linear quadratic gaussian theory and its application to the control of a super critical wing is presented. Results of control surface and sensor position optimization are discussed. Both frequency response matching and residualization used to obtain practical flutter controllers are examined. The development of algorithms and computer programs for flutter modeling and active control design procedures is reported.

  15. Thermally induced twist in graphite-epoxy tubes

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.; Rousseau, C. Q.; Tompkins, S. S.

    1988-01-01

    This paper discusses an analytical and experimental study to investigate the thermally induced twist in laminated angle-ply graphite-epoxy tubes. Attention is focused on balanced laminates which, contrary to intuition, exhibit twist when the temperature is changed. The twisting is due to the fact that a lamina with ( a + phi) orientation and a lamina with (a - phi) orientation must be at slightly different radial positions in the twist. The lamina with the greater radial position determines the sense of the twist. Classical lamination theory does not predict this phenomenon, and so as more sophisticated theory must be employed. This paper outlines such as theory, which is based on an generalized plane-deformation elasticity analysis, and presents experimental data to confirm the predictions of the theory. A brief description of the experimental apparatus and procedure used to measure twist is presented.

  16. Measuring mechanical strain and twist using helical photonic crystal fiber.

    PubMed

    Xi, Xiaoming; Wong, Gordon K L; Weiss, Thomas; Russell, Philip St J

    2013-12-15

    Solid-core photonic crystal fiber (PCF) with a permanent helical twist exhibits dips in its transmission spectrum at certain wavelengths. These are associated with the formation of orbital angular momentum states in the cladding. Here we investigate the tuning of these states with mechanical torque and axial tension. The dip wavelengths are found to scale linearly with both axial strain and mechanical twist rate. Analysis shows that the tension-induced shift in resonance wavelength is determined both by the photoelastic effect and by the change in twist rate, while the torsion-induced wavelength shift depends only on the change in twist rate. Twisted PCF can act as an effective optically monitored torque-tension transducer, twist sensor, or strain gauge. PMID:24322268

  17. Active parallel redundancy for electronic integrator-type control circuits

    NASA Technical Reports Server (NTRS)

    Peterson, R. A.

    1971-01-01

    Circuit extends concept of redundant feedback control from type-0 to type-1 control systems. Inactive channels are slaves to the active channel, if latter fails, it is rejected and slave channel is activated. High reliability and elimination of single-component catastrophic failure are important in closed-loop control systems.

  18. Student Activity Funds: Creating a System of Controls That Work.

    ERIC Educational Resources Information Center

    Cuzzetto, Charles

    1995-01-01

    Although student-activity funds usually represent a small portion of school-system monies, their very nature makes them a high risk. Outlines three steps for maintaining an efficient and effective system of controls over student-activity funds: (1) identifying control issues; (2) designing a control system; and (3) using checks and balances.…

  19. Attitude control with active actuator saturation prevention

    NASA Astrophysics Data System (ADS)

    Forbes, James Richard

    2015-02-01

    Spacecraft attitude control in the presence of actuator saturation is considered. The attitude controller developed has two components: a proportional component and an angular velocity component. The proportional control has a special form that depends on the attitude parameterization. The angular velocity control is realized by a strictly positive real system with its own input nonlinearity. The strictly positive real system can filter noise in the angular velocity measurement. With this control architecture the torques applied to the body are guaranteed to be below a predetermined value, thus preventing saturation of the actuators. The closed-loop equilibrium point corresponding to the desired attitude is shown to be asymptotically stable. Additionally, the control law does not require specific knowledge of the body's inertia properties, and is therefore robust to such modelling errors.

  20. Coherent control of birefringence and optical activity

    NASA Astrophysics Data System (ADS)

    Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

    2014-07-01

    We show that polarization effects due to anisotropy and chirality affecting a wave propagating through a thin slab of material can be controlled by another electromagnetic wave. No nonlinearity of the metamaterial slab is required and the control can be exercised at arbitrarily low intensities. In proof-of-principle experiments with anisotropic and chiral microwave metamaterials, we show that manifestations of linear and circular birefringence and dichroism can be modulated by the control wave from their maximum value to zero.

  1. Modeling the Benchmark Active Control Technology Wind-Tunnel Model for Active Control Design Applications

    NASA Technical Reports Server (NTRS)

    Waszak, Martin R.

    1998-01-01

    This report describes the formulation of a model of the dynamic behavior of the Benchmark Active Controls Technology (BACT) wind tunnel model for active control design and analysis applications. The model is formed by combining the equations of motion for the BACT wind tunnel model with actuator models and a model of wind tunnel turbulence. The primary focus of this report is the development of the equations of motion from first principles by using Lagrange's equations and the principle of virtual work. A numerical form of the model is generated by making use of parameters obtained from both experiment and analysis. Comparisons between experimental and analytical data obtained from the numerical model show excellent agreement and suggest that simple coefficient-based aerodynamics are sufficient to accurately characterize the aeroelastic response of the BACT wind tunnel model. The equations of motion developed herein have been used to aid in the design and analysis of a number of flutter suppression controllers that have been successfully implemented.

  2. Tuning of active vibration controllers for ACTEX by genetic algorithm

    NASA Astrophysics Data System (ADS)

    Kwak, Moon K.; Denoyer, Keith K.

    1999-06-01

    This paper is concerned with the optimal tuning of digitally programmable analog controllers on the ACTEX-1 smart structures flight experiment. The programmable controllers for each channel include a third order Strain Rate Feedback (SRF) controller, a fifth order SRF controller, a second order Positive Position Feedback (PPF) controller, and a fourth order PPF controller. Optimal manual tuning of several control parameters can be a difficult task even though the closed-loop control characteristics of each controller are well known. Hence, the automatic tuning of individual control parameters using Genetic Algorithms is proposed in this paper. The optimal control parameters of each control law are obtained by imposing a constraint on the closed-loop frequency response functions using the ACTEX mathematical model. The tuned control parameters are then uploaded to the ACTEX electronic control electronics and experiments on the active vibration control are carried out in space. The experimental results on ACTEX will be presented.

  3. Position dependent rate dampening in any active hand controller

    NASA Technical Reports Server (NTRS)

    Gregory, William W. (Inventor); Kauffman, James W. (Inventor)

    1994-01-01

    A control system for an active hand controller, for example, uses a control stick connected to and controlled by a motor. Electronics are provided to control the motor to eliminate oscillations due to motor torque and high gain due to breakout at the control stick when the control stick is at about its null position. Both hardware as well as software implementations can provide position dependent dampening to the control sticks such that when the control stick is located about a null position, a higher rate of dampening is provided than when the control stick is located outside the null position, when a lower rate of dampening is provided. The system provides a stable active hand controller control stick without degraded force and feel characteristics of the system.

  4. Optimal cooperative control synthesis of active displays

    NASA Technical Reports Server (NTRS)

    Garg, S.; Schmidt, D. K.

    1986-01-01

    The utility of augmenting displays to aid the human operator in controlling high order complex systems is well known. Analytical evaluation of various display designs for a simple k/s sup 2 plant in a compensatory tracking task using an optimal Control Model (OCM) of human behavior is carried out. This analysis reveals that significant improvement in performance should be obtained by skillful integration of key information into the display dynamics. The cooperative control synthesis technique previously developed to design pilot-optimal control augmentation is extended to incorporate the simultaneous design of performance enhancing augmented displays. The application of the cooperative control synthesis technique to the design of augmented displays is discussed for the simple k/s sup 2 plant. This technique is intended to provide a systematic approach to design optimally augmented displays tailored for specific tasks.

  5. Optimal cooperative control synthesis of active displays

    NASA Technical Reports Server (NTRS)

    Garg, S.; Schmidt, D. K.

    1985-01-01

    A technique is developed that is intended to provide a systematic approach to synthesizing display augmentation for optimal manual control in complex, closed-loop tasks. A cooperative control synthesis technique, previously developed to design pilot-optimal control augmentation for the plant, is extended to incorporate the simultaneous design of performance enhancing displays. The technique utilizes an optimal control model of the man in the loop. It is applied to the design of a quickening control law for a display and a simple K/s(2) plant, and then to an F-15 type aircraft in a multi-channel task. Utilizing the closed loop modeling and analysis procedures, the results from the display design algorithm are evaluated and an analytical validation is performed. Experimental validation is recommended for future efforts.

  6. Optimal cooperative control synthesis of active displays

    NASA Technical Reports Server (NTRS)

    Gary, Sanjay; Schmidt, David K.

    1987-01-01

    A technique is developed that is intended to provide a systematic approach to synthesizing display augmentation for optimal manual control in complex, closed-loop tasks. A cooperative control synthesis technique, previously developed to design pilot-optimal control augmentation for the plant, is extended to incorporate the simultaneous design of performance enhancing displays. The technique utilizes an optimal control model of the man in the loop. It is applied to the design of a quickening control law for a display and a simple K/(s squared) plant, and then to an F-15 type aircraft in a multichannel task. Utilizing the closed-loop modeling and analysis procedures, the results from the display design algorithm are evaluated and an analytical validation is performed. Experimental validation is recommended for future efforts.

  7. Optimal cooperative control synthesis of active displays

    NASA Technical Reports Server (NTRS)

    Garg, S.; Schmidt, D. K.

    1985-01-01

    The utility of augmenting displays to aid the human operator in controlling high order complex systems is well known. Analytical evaluations of various display designs for a simple k/s-squared plant in a compensatory tracking task using an Optimal Control Model (OCM) of human behavior is carried out. This analysis reveals that significant improvement in performance should be obtained by skillful integration of key information into the display dynamics. The cooperative control synthesis technique previously developed to design pilot-optimal control augmentation is extended to incorporate the simultaneous design of performance enhancing augmented displays. The application of the cooperative control synthesis technique to the design of augmented displays is discussed for the simple k/s-squared plant. This technique is intended to provide a systematic approach to design optimally augmented displays tailored for specific tasks.

  8. Twisted rudder for reducing fuel-oil consumption

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hun; Choi, Jung-Eun; Choi, Bong-Jun; Chung, Seok-Ho

    2014-09-01

    Three twisted rudders fit for large container ships have been developed; 1) the Z-twisted rudder that is an asymmetry type taking into consideration incoming flow angles of the propeller slipstream, 2) the ZB-twisted rudder with a rudder bulb added onto the Z-twisted rudder, and 3) the ZB-F twisted rudder with a rudder fin attached to the ZB-twisted rudder. The twisted rudders have been designed computationally with the hydrodynamic characteristics in a self-propulsion condition in mind. The governing equation is the Navier-Stokes equations in an unsteady turbulent flow. The turbulence model applied is the Reynolds stress. The calculation was carried out in towing and self-propulsion conditions. The sliding mesh technique was employed to simulate the flow around the propeller. The speed performances of the ship with the twisted rudders were verified through model tests in a towing tank. The twisted versions showed greater performance driven by increased hull efficiency from less thrust deduction fraction and more effective wake fraction and decreased propeller rotating speed

  9. Bound states on the lattice with partially twisted boundary conditions

    NASA Astrophysics Data System (ADS)

    Agadjanov, D.; Guo, F.-K.; Ríos, G.; Rusetsky, A.

    2015-01-01

    We propose a method to study the nature of exotic hadrons by determining the wave function renormalization constant Z from lattice simulations. It is shown that, instead of studying the volume-dependence of the spectrum, one may investigate the dependence of the spectrum on the twisting angle, imposing twisted boundary conditions on the fermion fields on the lattice. In certain cases, e.g., the case of the DK bound state which is addressed in detail, it is demonstrated that the partial twisting is equivalent to the full twisting up to exponentially small corrections.

  10. Modelling of Nonthermal Microwave Emission from Twisted Magnetic Loops

    NASA Astrophysics Data System (ADS)

    Sharykin, I. N.; Kuznetsov, A. A.

    2016-05-01

    Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand the impact of a twisted magnetic field topology on radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with a particular polarisation distribution. The polarisation sign inversion line is inclined relatively to the axis of the loop. The radio emission source is more compact in the case of a less twisted loop, assuming an anisotropic pitch-angle distribution of nonthermal electrons.

  11. Modelling of Nonthermal Microwave Emission from Twisted Magnetic Loops

    NASA Astrophysics Data System (ADS)

    Sharykin, I. N.; Kuznetsov, A. A.

    2016-06-01

    Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand the impact of a twisted magnetic field topology on radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with a particular polarisation distribution. The polarisation sign inversion line is inclined relatively to the axis of the loop. The radio emission source is more compact in the case of a less twisted loop, assuming an anisotropic pitch-angle distribution of nonthermal electrons.

  12. Active Combustion Control for Aircraft Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    DeLaat, John C.; Breisacher, Kevin J.; Saus, Joseph R.; Paxson, Daniel E.

    2000-01-01

    Lean-burning combustors are susceptible to combustion instabilities. Additionally, due to non-uniformities in the fuel-air mixing and in the combustion process, there typically exist hot areas in the combustor exit plane. These hot areas limit the operating temperature at the turbine inlet and thus constrain performance and efficiency. Finally, it is necessary to optimize the fuel-air ratio and flame temperature throughout the combustor to minimize the production of pollutants. In recent years, there has been considerable activity addressing Active Combustion Control. NASA Glenn Research Center's Active Combustion Control Technology effort aims to demonstrate active control in a realistic environment relevant to aircraft engines. Analysis and experiments are tied to aircraft gas turbine combustors. Considerable progress has been shown in demonstrating technologies for Combustion Instability Control, Pattern Factor Control, and Emissions Minimizing Control. Future plans are to advance the maturity of active combustion control technology to eventual demonstration in an engine environment.

  13. Acceleration-Augmented LQG Control of an Active Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Feeley, Joseph J.

    1993-01-01

    A linear-quadratic-gaussian (LQG) regulator controller design for an acceleration-augmented active magnetic bearing (AMB) is outlined. Acceleration augmentation is a key feature in providing improved dynamic performance of the controller. The optimal control formulation provides a convenient method of trading-off fast transient response and force attenuation as control objectives.

  14. Actively controlled shaft seals for aerospace applications

    NASA Technical Reports Server (NTRS)

    Salant, Richard F.

    1991-01-01

    The main objective is to determine the feasibility of utilizing controllable mechanical seals for aerospace applications. A potential application was selected as a demonstration case: the buffer gas seal in a LOX (liquid oxygen) turbopump. Currently, floating ring seals are used in this application. Their replacement with controllable mechanical seals would result in substantially reduced leakage rates. This would reduce the required amount of stored buffer gas, and therefore increase the vehicle payload. For such an application, a suitable controllable mechanical seal was designed and analyzed.

  15. PARTICULATE EMISSION MEASUREMENTS FROM CONTROLLED CONSTRUCTION ACTIVITIES

    EPA Science Inventory

    The report summarized the results of field testing of the effectiveness of control measures for sources of fugitive particulate emissions found at construction sites. The effectiveness of watering temporary, unpaved travel surfaces on emissions of particulate matter with aerodyna...

  16. Let's twist again: elasto-capillary assembly of parallel ribbons.

    PubMed

    Legrain, Antoine; Berenschot, Erwin J W; Abelmann, Leon; Bico, José; Tas, Niels R

    2016-09-14

    We show the self-assembly through twisting and bending of side by side ribbons under the action of capillary forces. Micro-ribbons made of silicon nitride are batch assembled at the wafer scale. We study their assembly as a function of their dimensions and separating distance. Model experiments are carried out at the macroscopic scale where the tension in ribbons can easily be tuned. The process is modeled considering the competition between capillary, elastic and tension forces. Theory shows a good agreement for macroscale assemblies, while the accuracy is within 30% at the micrometer scale. This simple self-assembly technique yields highly symmetric and controllable structures which could be used for batch fabrication of functional 3D micro-structures. PMID:27501147

  17. The DRG shift: a new twist for ICD-10 preparation.

    PubMed

    Long, Peri L

    2012-06-01

    Analysis of your specific business is a key component of ICD-10 implementation. An understanding of your organization's current reimbursement trends will go a long way to assessing and preparing for the impact of ICD-10 in your environment. If you cannot be prepared for each detailed scenario, remember that much of the analysis and resolution requires familiar coding, DRG analysis, and claims processing best practices. Now, they simply have the new twist of researching new codes and some new concepts. The news of a delay in the implementation compliance date, along with the release of grouper Version 29, should encourage your educational and business analysis efforts. This is a great opportunity to maintain open communication with the Centers for Medicare & Medicaid Services, Department of Health and Human Services, and Centers for Disease Control. This is also a key time to report any unusual or discrepant findings in order to provide input to the final rule. PMID:22741518

  18. Twisted geometries, twistors, and conformal transformations

    NASA Astrophysics Data System (ADS)

    Lângvik, Miklos; Speziale, Simone

    2016-07-01

    The twisted geometries of spin network states are described by simple twistors, isomorphic to null twistors with a timelike direction singled out. The isomorphism depends on the Immirzi parameter γ and reduces to the identity for γ =∞ . Using this twistorial representation, we study the action of the conformal group SU(2,2) on the classical phase space of loop quantum gravity, described by twisted geometry. The generators of translations and conformal boosts do not preserve the geometric structure, whereas the dilatation generator does. It corresponds to a one-parameter family of embeddings of T*SL(2,C) in twistor space, and its action preserves the intrinsic geometry while changing the extrinsic one—that is the boosts among polyhedra. We discuss the implication of this action from a dynamical point of view and compare it with a discretization of the dilatation generator of the continuum phase space, given by the Lie derivative of the group character. At leading order in the continuum limit, the latter reproduces the same transformation of the extrinsic geometry, while also rescaling the areas and volumes and preserving the angles associated with the intrinsic geometry. Away from the continuum limit, its action has an interesting nonlinear structure but is in general incompatible with the closure constraint needed for the geometric interpretation. As a side result, we compute the precise relation between the extrinsic geometry used in twisted geometries and the one defined in the gauge-invariant parametrization by Dittrich and Ryan and show that the secondary simplicity constraints they posited coincide with those dynamically derived in the toy model of [Classical Quantum Gravity 32, 195015 (2015)].

  19. Active control of flexural vibrations in beams

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.

    1987-01-01

    The feasibility of using piezoelectric actuators to control the flexural oscillations of large structures in space is investigated. Flexural oscillations are excited by impulsive loads. The vibratory response can degrade the pointing accuracy of cameras and antennae, and can cause high stresses at structural node points. Piezoelectric actuators have the advantage of exerting localized bending moments. In this way, vibration is controlled without exciting rigid body modes. The actuators are used in collocated sensor/driver pairs to form a feedback control system. The sensor produces a voltage that is proportional to the dynamic stress at the sensor location, and the driver produces a force that is proportional to the voltage applied to it. The analog control system amplifies and phase shifts the sensor signal to produce the voltage signal that is applied to the driver. The feedback control is demonstrated to increase the first mode damping in a cantilever beam by up to 100 percent, depending on the amplifier gain. The damping efficiency of the control system when the piezoelectrics are not optimally positioned at points of high stress in the beam is evaluated.

  20. Colloidal entanglement in highly twisted chiral nematic colloids: twisted loops, Hopf links, and trefoil knots.

    PubMed

    Jampani, V S R; Škarabot, M; Ravnik, M; Čopar, S; Žumer, S; Muševič, I

    2011-09-01

    The topology and geometry of closed defect loops is studied in chiral nematic colloids with variable chirality. The colloidal particles with perpendicular surface anchoring of liquid crystalline molecules are inserted in a twisted nematic cell with the thickness that is only slightly larger than the diameter of the colloidal particle. The total twist of the chiral nematic structure in cells with parallel boundary conditions is set to 0, π, 2π, and 3π, respectively. We use the laser tweezers to discern the number and the topology of the -1/2 defect loops entangling colloidal particles. For a single colloidal particle, we observe that a single defect loop is winding around the particle, with the winding pattern being more complex in cells with higher total twist. We observe that colloidal dimers and colloidal clusters are always entangled by one or several -1/2 defect loops. For colloidal pairs in π-twisted cells, we identify at least 17 different entangled structures, some of them exhibiting linked defect loops-Hopf link. Colloidal entanglement is even richer with a higher number of colloidal particles, where we observe not only linked, but also colloidal clusters knotted into the trefoil knot. The experiments are in good agreement with numerical modeling using Landau-de Gennes theory coupled with geometrical and topological considerations using the method of tetrahedral rotation. PMID:22060386

  1. Active chatter control in a milling machine

    SciTech Connect

    Dohner, J.L.; Hinnerichs, T.D.; Lauffer, J.P.

    1997-08-01

    The use of active feedback compensation to mitigate cutting instabilities in an advanced milling machine is discussed in this paper. A linear structural model delineating dynamics significant to the onset of cutting instabilities was combined with a nonlinear cutting model to form a dynamic depiction of an existing milling machine. The model was validated with experimental data. Modifications made to an existing machine model were used to predict alterations in dynamics due to the integration of active feedback compensation. From simulations, subcomponent requirements were evaluated and cutting enhancements were predicted. Active compensation was shown to enable more than double the metal removal rate over conventional milling machines. 25 refs., 10 figs., 1 tab.

  2. Superlubricity in quasicrystalline twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Koren, Elad; Duerig, Urs

    2016-05-01

    The unique atomic positions in quasicrystals lead to peculiar self-similarity and fractal-like structural morphology. Accordingly, many of the material properties are supposed to manifest exceptional characteristics. In this Rapid Communication, we explain through numerical simulations the fundamental and peculiar aspects of quasicrystals wearless friction manifested in a 30° twisted bilayer graphene system. In particular, the sliding force exhibits a fractal structure with distinct area correlations due to the natural mixture between both periodic and aperiodic lateral modulations. In addition, zero power scaling of the sliding force with respect to the contact area is demonstrated for a geometric sequence of dodecagonal elements.

  3. Non-destructive identification of twisted light.

    PubMed

    Li, Pengyun; Wang, Bo; Song, Xinbing; Zhang, Xiangdong

    2016-04-01

    The non-destructive identification of the orbital angular momentum (OAM) is essential to various applications in the optical information processing. Here, we propose and demonstrate experimentally an efficient method to identify non-destructively the OAM by using a modified Mach-Zehnder interferometer. Our schemes are applicable not only to the case with integer charges, but also to optical vortices with noninteger charges. Our Letter presents the first experimental demonstration of the non-destructive identification of twisted light with integer or noninteger topological charges, which has potential applications in the OAM-based data transmission for optical communications. PMID:27192290

  4. Bounds on tensor wave and twisted inflation

    NASA Astrophysics Data System (ADS)

    Panda, Sudhakar; Sami, M.; Ward, John

    2010-11-01

    We study the bounds on tensor wave in a class of twisted inflation models, where D(4+2k)-branes are wrapped on cycles in the compact manifold and wrap the Kaluza-Klein direction in the corresponding effective field theory. While the lower bound is found to be analogous to that in type IIB models of brane inflation, the upper bound turns out to be significantly different. This is argued for a range of values for the parameter gsM satisfying the self-consistency relation and the WMAP data. Further, we observe that the wrapped D8-brane appears to be the most attractive from a cosmological perspective.

  5. Modes of a twisted optical cavity

    SciTech Connect

    Habraken, Steven J. M.; Nienhuis, Gerard

    2007-03-15

    An astigmatic optical resonator consists of two astigmatic mirrors facing each other. The resonator is twisted when the symmetry axes of the mirrors are nonparallel. We present an algebraic method to obtain the complete set of the paraxial eigenmodes of such a resonator. Basic ingredients are the complex eigenvectors of the four-dimensional transfer matrix that describes the transformation of a ray of light over a roundtrip of the resonator. The relation between the fundamental mode and the higher-order modes is expressed in terms of raising operators in the spirit of the ladder operators of the quantum harmonic oscillator.

  6. Surgical Treatment of the Twisted Nose.

    PubMed

    Menger, Dirk Jan

    2016-01-01

    The twisted nose is a challenging procedure in rhinoplasty. The goal of surgery is to realign the nasal skeleton to create symmetry in the face and restore nasal patency. Key in the surgical procedure is that all structures of the nasal skeleton be dissected free, mobilized, repositioned, and stabilized. Important surgical steps are intermediate osteotomies on the contralateral side of the deviation for the upper nasal third; for the mid nasal third, a unilateral spreader graft or splint on the nondeviated side, and for the lower nasal third, fixation of the caudal septum to the anterior nasal spine. PMID:26616698

  7. [The use of twist drill craniostomy in stereotactic surgery for brain tumors].

    PubMed

    Matsumoto, K; Tomita, S; Nakagawa, M; Adachi, H; Tada, E; Maeda, Y; Furuta, T; Ohmoto, T

    1995-12-01

    A twist drill craniostomy is a rapid and relatively simple technique for perforating the skull in order to gain access to the epidural and subdural spaces and the brain. Fifty-eight patients underwent 173 twist drill craniostomies in the stereotactic procedures for the diagnosis and the treatment of brain tumors (brain tumor biopsy, implanting radioactive sources and placement of the catheters for navigation surgery) from September, 1992, through to May, 1995, at our institute. The technique was compared with standard burr hole craniostomy used in 42 patients with brain tumor. In the twist drill craniostomy, the scalp was penetrated directly by hand twist drill (2.7 mm in diameter) and scalp bleeding was able to be be controlled by injecting local anesthetic with epinephrine subcutaneously. The safety stop on the drill was set in advance based on the expected thickness of the skull at its penetration point to provide control of penetration depth as it passed through the skull hole and dura. A hole in the skull was made as the drill was advanced until a change in resistance indicated that the inner table of the skull had been penetrated and the dura lacerated. The cannula with stylet was then inserted through the guide tube to assure the penetration of the skull and dura. As the cannula penetrated the dura, a loss of resistance was noted as it proceeded through the dura toward the pial surface, The time needed in this procedure was less than 3 minutes. Associated with this procedure, there were no complications such as bleeding, or infection in 173 twist drill craniostomies in the 58 patients. Our experience with this procedure proved it to be simple, efficient, safe and superior to conventional burr hole craniostomy. PMID:8927216

  8. Localized topological states in Bragg multihelicoidal fibers with twist defects

    NASA Astrophysics Data System (ADS)

    Alexeyev, C. N.; Lapin, B. P.; Milione, G.; Yavorsky, M. A.

    2016-06-01

    We have studied the influence of a twist defect in multihelicoidal Bragg fibers on the emerging of localized defect modes. We have shown that if such a fiber is excited with a Gaussian beam this leads to the appearance of a defect-localized topological state, whose topological charge coincides with the order of rotational symmetry of the fiber's refractive index. We have shown that this effect has a pronounced crossover behavior. We have also formulated a principle of creating the systems that can nestle defect-localized topologically charged modes. According to this principle, such systems have to possess topological activity, that is, the ability to change the topological charge of the incoming field, and operate in the Bragg regime.

  9. Experimental investigation of active machine tool vibration control

    NASA Astrophysics Data System (ADS)

    Rojas, J.; Liang, Chen; Geng, Zheng J.

    1996-05-01

    The successful vibration reduction of machine tools during machining process can improve productivity, increase quality, and reduce tool wear. This paper will present our initial investigation in the application of smart material technologies in machine tool vibration control using magnetostrictive actuators and electrorheological elastomer dampers on an industrial Sheldon horizontal lathe. The dynamics of the machining process are first studied, which reveals the complexity in the machine tool vibration response and the challenge to the active control techniques. The active control experiment shows encouraging results. The use of electrorheological elastomer damping device for active/passive vibration control provides significant vibration reduction in the high frequency range and great improvement in the workpiece surface finishing. The research presented in this paper demonstrates that the combination of active and active/passive vibration control techniques is very promising for successful machine tool vibration control.

  10. Observation of the intrinsic bandgap behaviour in as-grown epitaxial twisted graphene.

    PubMed

    Park, Jeongho; Mitchel, William C; Elhamri, Said; Grazulis, Lawrence; Hoelscher, John; Mahalingam, Krishnamurthy; Hwang, Choongyu; Mo, Sung-Kwan; Lee, Jonghoon

    2015-01-01

    Twisted graphene is of particular interest due to several intriguing characteristics, such as its the Fermi velocity, van Hove singularities and electronic localization. Theoretical studies recently suggested the possible bandgap opening and tuning. Here, we report a novel approach to producing epitaxial twisted graphene on SiC (0001) and the observation of its intrinsic bandgap behaviour. The direct deposition of C60 on pre-grown graphene layers results in few-layer twisted graphene confirmed by angular resolved photoemission spectroscopy and Raman analysis. The strong enhanced G band in Raman and sp(3) bonding characteristic in X-ray photoemission spectroscopy suggests the existence of interlayer interaction between adjacent graphene layers. The interlayer spacing between graphene layers measured by transmission electron microscopy is 0.352 ± 0.012 nm. Thermal activation behaviour and nonlinear current-voltage characteristics conclude that an intrinsic bandgap is opened in twisted graphene. Low sheet resistance (~ 160 Ω □(-1) at 10 K) and high mobility (~2,000 cm(2) V(-1) s(-1) at 10 K) are observed. PMID:25562285

  11. Ion-triggered spring-like motion of a double helicate accompanied by anisotropic twisting.

    PubMed

    Miwa, Kazuhiro; Furusho, Yoshio; Yashima, Eiji

    2010-06-01

    Molecules that extend and contract under external stimuli are used to build molecular machines with nanomechanical functions. But although common in biological systems, such extension and contraction motions with helical molecules have rarely been accompanied by unidirectional twisting in synthetic systems. Here we show that sodium ions can trigger the reversible anisotropic twisting of an enantiomeric double-stranded helicate, without racemization. An optically active helicate consisting of two tetraphenol strands bridged by two spiroborate groups sandwiches a sodium ion. On removal of the central sodium-through addition of a cryptand [2.2.1] in solution-the double helicate extends. Crystallographic and nuclear magnetic resonance studies reveal that the extended helicate is over twice as long as the initial molecule, and is twisted in the right-handed direction. Circular dichroism analysis suggests that the twisting doesn't affect the helicate's handedness. This anisotropic extension-contraction process is reversibly triggered by the successive addition and removal of sodium ions in solution. PMID:20489711

  12. Formal Verification of Effectiveness of Control Activities in Business Processes

    NASA Astrophysics Data System (ADS)

    Arimoto, Yasuhito; Iida, Shusaku; Futatsugi, Kokichi

    It has been an important issue to deal with risks in business processes for achieving companies' goals. This paper introduces a method for applying a formal method to analysis of risks and control activities in business processes in order to evaluate control activities consistently, exhaustively, and to give us potential to have scientific discussion on the result of the evaluation. We focus on document flows in business activities and control activities and risks related to documents because documents play important roles in business. In our method, document flows including control activities are modeled and it is verified by OTS/CafeOBJ Method that risks about falsification of documents are avoided by control activities in the model. The verification is done by interaction between humans and CafeOBJ system with theorem proving, and it raises potential to discuss the result scientifically because the interaction gives us rigorous reasons why the result is derived from the verification.

  13. Active Control of Magnetically Levitated Bearings

    SciTech Connect

    BARNEY, PATRICK S.; LAUFFER, JAMES P.; REDMOND, JAMES M.; SULLIVAN, WILLIAM N.

    2001-03-01

    This report summarizes experimental and test results from a two year LDRD project entitled Real Time Error Correction Using Electromagnetic Bearing Spindles. This project was designed to explore various control schemes for levitating magnetic bearings with the goal of obtaining high precision location of the spindle and exceptionally high rotational speeds. As part of this work, several adaptive control schemes were devised, analyzed, and implemented on an experimental magnetic bearing system. Measured results, which indicated precision positional control of the spindle was possible, agreed reasonably well with simulations. Testing also indicated that the magnetic bearing systems were capable of very high rotational speeds but were still not immune to traditional structural dynamic limitations caused by spindle flexibility effects.

  14. Actively controlled shaft seals for aerospace applications

    NASA Technical Reports Server (NTRS)

    Salant, Richard F.

    1993-01-01

    An electronically controlled mechanical seal for use as the purge gas seal in a liquid oxygen turbo pump has been fabricated and tested under transient operating conditions. The thickness of the lubricating film is controlled by adjusting the coning of the carbon face. This is accomplished by applying a voltage to a piezoelectric actuator to which the carbon face is bonded. The seal has been operated with a closed-loop control system that utilizes either the leakage rate or the seal face temperature as the feedback. Both speed and pressure transients have been imposed on the seal. The transient tests have demonstrated that the seal is capable of maintaining low leakage rates while limiting the face temperatures.

  15. Numerical Investigation of Plasma Active Flow Control

    NASA Astrophysics Data System (ADS)

    Sun, Baigang; Li, Feng; Zhang, Shanshan; Wang, Jingyu; Zhang, Lijuan; Zhao, Erlei

    2010-12-01

    Based on the theory of EHD (electronhydrodynamic), a simplified volume force model is applied to simulation to analyze the traits of plasma flow control in flow field, in which the cold plasma is generated by a DBD (dielectric-barrier-discharge) actuator. With the para-electric action of volume force in electric field, acceleration characteristics of the plasma flow are investigated for different excitation intensities of RF (radio frequency) power for the actuator. Furthermore, the plasma acceleration leads to an asymmetric distribution of flow field, and hence induces the deflection of jet plume, then results in a significant deflection angle of 6.26° thrust-vectoring effect. It appears that the plasma flow control technology is a new tentative method for the thrust-vectoring control of a space vehicle.

  16. Active Flap Control of the SMART Rotor for Vibration Reduction

    NASA Technical Reports Server (NTRS)

    Hall, Steven R.; Anand, R. Vaidyanathan; Straub, Friedrich K.; Lau, Benton H.

    2009-01-01

    Active control methodologies were applied to a full-scale active flap rotor obtained during a joint Boeing/ DARPA/NASA/Army test in the Air Force National Full-Scale Aerodynamic Complex 40- by 80-foot anechoic wind tunnel. The active flap rotor is a full-scale MD 900 helicopter main rotor with each of its five blades modified to include an on-blade piezoelectric actuator-driven flap with a span of 18% of radius, 25% of chord, and located at 83% radius. Vibration control demonstrated the potential of active flaps for effective control of vibratory loads, especially normal force loads. Active control of normal force vibratory loads using active flaps and a continuous-time higher harmonic control algorithm was very effective, reducing harmonic (1-5P) normal force vibratory loads by 95% in both cruise and approach conditions. Control of vibratory roll and pitch moments was also demonstrated, although moment control was less effective than normal force control. Finally, active control was used to precisely control blade flap position for correlation with pretest predictions of rotor aeroacoustics. Flap displacements were commanded to follow specific harmonic profiles of 2 deg or more in amplitude, and the flap deflection errors obtained were less than 0.2 deg r.m.s.

  17. Recent advances in active control of aircraft cabin noise

    NASA Astrophysics Data System (ADS)

    Mathur, Gopal; Fuller, Christopher

    2002-11-01

    Active noise control techniques can provide significant reductions in aircraft interior noise levels without the structural modifications or weight penalties usually associated with passive techniques, particularly for low frequency noise. Our main objective in this presentation is to give a review of active control methods and their applications to aircraft cabin noise reduction with an emphasis on recent advances and challenges facing the noise control engineer in the practical application of these techniques. The active noise control method using secondary acoustic sources, e.g., loudspeakers, as control sources for tonal noise reduction is first discussed with results from an active noise control flight test demonstration. An innovative approach of applying control forces directly to the fuselage structure using piezoelectric actuators, known as active structural acoustic control (ASAC), to control cabin noise is then presented. Experimental results from laboratory ASAC tests conducted on a full-scale fuselage and from flight tests on a helicopter will be discussed. Finally, a hybrid active/passive noise control approach for achieving significant broadband noise reduction will be discussed. Experimental results of control of broadband noise transmission through an aircraft structure will be presented.

  18. Pulley With Active Antifriction Actuator And Control

    NASA Technical Reports Server (NTRS)

    Ih, Che-Hang C.; Vivian, Howard C.

    1994-01-01

    Torque actuator and associated control system minimizes effective friction of rotary bearing. Motor exerts compensating torque in response to feedback from external optical sensor. Compensation torque nearly cancels frictional torque of shaft bearings. Also useful in reducing bearing friction in gyro-scopes, galvanometers, torquemeters, accelerometers, earth-motion detectors, and balances.

  19. Selective Activation and Disengagement of Moral Control.

    ERIC Educational Resources Information Center

    Bandura, Albert

    1990-01-01

    Analyzes psychological mechanisms by which moral control is selectively disengaged from inhumane conduct in ordinary and unusual circumstances. Explores the symptoms of moral exclusion as described in the literature. Presents categories that unify theory on moral exclusion and contribute practical classifications for use in empirical studies. (JS)

  20. Active control of cantilever-beam vibration

    NASA Astrophysics Data System (ADS)

    Serbyn, M. Roman

    2002-11-01

    A bang-bang control system previously developed for the stabilization of a rigid platform [ISA Trans. 21, 55-59 (1982)] has been adapted to the problem of reducing flexural vibrations of a beam. The electromechanical system develops an appropriate control signal for the actuator from samples of the disturbance by analog and digital signal processing using integrated circuits. The effectiveness of this approach is predicated upon the sampling rate being much higher than the maximum vibration frequency to be silenced. It is also robust with respect to the waveform of the disturbance. Noise reductions of 10-20 dB have been achieved, depending on the bandwidth of the noise. The cantilever, chosen because of its mechanical and theoretical simplicity, provides a good foundation for the study of more complex structures, like airfoils and nonrigid platforms. In both experimental and analytical investigations the emphasis has been on the optimization of control parameters, particularly with regard to the application of the cancellation signal. Reduction in size and cost of the control unit is possible by incorporating the latest technological advances in electronic and electromechanical devices, such as FPGA boards and MEMS components.

  1. Incoherent interlayer conduction in twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Kim, Youngwook; Nam, S.-G.; Lee, H.-J.; Kim, Jun Sung; Yun, H.; Lee, S. W.; Son, M.; Choi, H. C.; Lee, D. S.; Kim, D. C.; Seo, S.

    2014-03-01

    Coherent motion of the electrons in the Bloch states often breaks down for the interlayer conduction in layered materials where the interlayer coupling is significantly reduced by e.g. large interlayer separation. Here, we report complete suppression of coherent conduction in twisted bilayer graphene even with an atomic length scale of layer separation. The interlayer conduction were investigated using a cross junction of monolayer graphene layers. The interlayer resistivity is much higher than the c-axis resistivity of Bernal-stacked graphite and exhibits strong dependence on temperature as well as on external electric fields. These results suggest that the graphene layers are significantly decoupled by rotation, and the incoherent electron tunneling is the main interlayer conduction channel. In this regime, the interlayer conduction is determined by the overlap of the Dirac Fermi surfaces (FS) from each layer. The angle dependence of the interlayer resistivity is found to be relatively strong at low temperatures, while it becomes moderate and monotonous at high temperatures. This demonstrates the importance of phonon-mediated conduction at high temperatures, which enhances the overlap between the momentum-mismatched FS's in twisted bilayer graphene.

  2. Holographic generation of highly twisted electron beams.

    PubMed

    Grillo, Vincenzo; Gazzadi, Gian Carlo; Mafakheri, Erfan; Frabboni, Stefano; Karimi, Ebrahim; Boyd, Robert W

    2015-01-23

    Free electrons can possess an intrinsic orbital angular momentum, similar to those in an electron cloud, upon free-space propagation. The wave front corresponding to the electron's wave function forms a helical structure with a number of twists given by the angular speed. Beams with a high number of twists are of particular interest because they carry a high magnetic moment about the propagation axis. Among several different techniques, electron holography seems to be a promising approach to shape a conventional electron beam into a helical form with large values of angular momentum. Here, we propose and manufacture a nanofabricated phase hologram for generating a beam of this kind with an orbital angular momentum up to 200ℏ. Based on a novel technique the value of orbital angular momentum of the generated beam is measured and then compared with simulations. Our work, apart from the technological achievements, may lead to a way of generating electron beams with a high quanta of magnetic moment along the propagation direction and, thus, may be used in the study of the magnetic properties of materials and for manipulating nanoparticles. PMID:25659003

  3. Needleless electrospinning with twisted wire spinneret

    NASA Astrophysics Data System (ADS)

    Holopainen, Jani; Penttinen, Toni; Santala, Eero; Ritala, Mikko

    2015-01-01

    A needleless electrospinning setup named ‘Needleless Twisted Wire Electrospinning’ was developed. The polymer solution is electrospun from the surface of a twisted wire set to a high voltage and collected on a cylindrical collector around the wire. Multiple Taylor cones are simultaneously self-formed on the downward flowing solution. The system is robust and simple with no moving parts aside from the syringe pump used to transport the solution to the top of the wire. The structure and process parameters of the setup and the results on the preparation of polyvinyl pyrrolidone (PVP), hydroxyapatite (HA) and bioglass fibers with the setup are presented. PVP fiber sheets with areas of 40 × 120 cm2 and masses up to 1.15 g were prepared. High production rates of 5.23 g h-1 and 1.40 g h-1 were achieved for PVP and HA respectively. The major limiting factor of the setup is drying of the polymer solution on the wire during the electrospinning process which will eventually force to interrupt the process for cleaning of the wire. Possible solutions to this problem and other ways to develop the setup are discussed. The presented system provides a simple way to increase the production rate and area of fiber sheet as compared with the conventional needle electrospinning.

  4. Action for twisted self-duality

    NASA Astrophysics Data System (ADS)

    Bunster, Claudio; Henneaux, Marc

    2011-06-01

    One may write the Maxwell equations in terms of two gauge potentials, one electric and one magnetic, by demanding that their field strengths should be dual to each other. This requirement is the condition of twisted self-duality. It can be extended to p-forms in spacetime of D dimensions, and it survives the introduction of a variety of couplings among forms of different rank, and also to spinor and scalar fields, which emerge naturally from supergravity. In this paper we provide a systematic derivation of the action principle, whose equations of motion are the condition of twisted self-duality. The derivation starts from the standard Maxwell action, extended to include the aforementioned couplings, and proceeds via the Hamiltonian formalism through the resolution of Gauss’s law. In the pure Maxwell case we recover in this way an action that had been postulated by other authors, through an ansatz based on an action given earlier by us for untwisted self-duality. When Chern-Simons couplings are included, our action is, however, new. The derivation from the standard extended Maxwell action implies of course that the theory is Lorentz invariant and can be locally coupled to gravity. Nevertheless we include a direct compact Hamiltonian proof of these properties, which is based on the surface-deformation algebra. The symmetry in the dependence of the action on the electric and magnetic variables is manifest, since they appear as canonical conjugates. Spacetime covariance, although present, is not manifest.

  5. How the embryonic brain tube twists

    NASA Astrophysics Data System (ADS)

    Chen, Zi; Guo, Qiaohang; Forsch, Nickolas; Taber, Larry

    2014-03-01

    During early development, the tubular brain of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This deformation is one of the major organ-level symmetry-breaking events in development. Available evidence suggests that bending is caused by differential growth, but the mechanism for torsion remains poorly understood. Since the heart almost always loops in the same direction that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is virtually nonexistent, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. In addition, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model is used to interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''.

  6. Strong CP, Flavor, and Twisted Split Fermions

    SciTech Connect

    Harnik, Roni; Perez, Gilad; Schwartz, Matthew D.; Shirman, Yuri

    2004-11-10

    We present a natural solution to the strong CP problem in the context of split fermions. By assuming CP is spontaneously broken in the bulk, a weak CKM phase is created in the standard model due to a twisting in flavor space of the bulk fermion wavefunctions. But the strong CP phase remains zero, being essentially protected by parity in the bulk and CP on the branes. As always in models of spontaneous CP breaking, radiative corrections to theta bar from the standard model are tiny, but even higher dimension operators are not that dangerous. The twisting phenomenon was recently shown to be generic, and not to interfere with the way that split fermions naturally weaves small numbers into the standard model. It follows that out approach to strong CP is compatible with flavor, and we sketch a comprehensive model. We also look at deconstructed version of this setup which provides a viable 4D model of spontaneous CP breaking which is not in the Nelson-Barr class.

  7. Terahertz conductivity of twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Chia, Elbert E. M.; Zou, Xingquan; Shang, Jingzhi; Leaw, Jianing; Luo, Zhiqiang; Luo, Liyan; Cheong, Siew Ann; Su, Haibin; Zhu, Jian-Xin; Castro Neto, A. H.; Yu, Ting

    2013-03-01

    Using terahertz time-domain spectroscopy, the real part of optical conductivity [σ1 (ω) ] of twisted bilayer graphene was obtained at different temperatures (10 - 300 K) in the frequency range 0.3 - 3 THz. On top of a Drude-like response, we see a strong and narrow peak in σ1 (ω) at ~2.7 THz. We analyze the overall Drude-like response using a disorder-dependent (unitary scattering) model, then attribute the peak at 2.7 THz to an enhanced density of states at that energy, that is caused by the presence of van Hove singularities arising from a commensurate twisting of the two graphene layers. Singapore MOE AcRF Tier 2 (ARC 23/08), NRF-CRP (NRF-CRP4-2008-04), NNSA of the U.S. DOE at LANL (DE-AC52-06NA25396), LANL LDRD Program, NRF-CRP (R-144-000-295-281), DOE DE-FG02-08ER46512, ONR MURI N00014-09-1-1063.

  8. Widely tunable LP11 cladding-mode resonance in a twisted mechanically induced long-period fiber grating.

    PubMed

    Nair, Anitha S; Sudeep Kumar, V P; Joe, Hubert

    2015-03-10

    A record tunability of 35 nm for the LP(11) cladding-mode resonance in a twisted mechanically induced long-period fiber grating using standard single-mode communication fiber is demonstrated. By forming the LP(11) resonance far away from its cut-off wavelength and modifying the grooves of the grating in the form of smooth semicircular humps, a high twist sensitivity of 8.75 nm/(rad/cm) and a controlled tunability of 35 nm is achieved. The fiber with its lacquer coating is not broken even at a severe twist rate of 5.44 rad/cm. The present design can be used as a novel variable optical selective wavelength attenuator since the bandwidth, rejection efficiency, and center wavelength can be controlled by changing the grating length, pressure over the grating, and fiber twist, respectively. Using the results, a cost-effective tunable variable optical attenuator for selective channel-blanking applications is also demonstrated. A fine tunability of 1.5 nm is achieved for a twist rate change of 0.1 rad/cm. PMID:25968376

  9. Advanced Study for Active Noise Control in Aircraft (ASANCA)

    NASA Technical Reports Server (NTRS)

    Borchers, Ingo U.; Emborg, Urban; Sollo, Antonio; Waterman, Elly H.; Paillard, Jacques; Larsen, Peter N.; Venet, Gerard; Goeransson, Peter; Martin, Vincent

    1992-01-01

    Aircraft interior noise and vibration measurements are included in this paper from ground and flight tests. In addition, related initial noise calculations with and without active noise control are conducted. The results obtained to date indicate that active noise control may be an effective means for reducing the critical low frequency aircraft noise.

  10. Twisted K-Theory and Finite-Dimensional Approximation

    NASA Astrophysics Data System (ADS)

    Gomi, Kiyonori

    2010-03-01

    We provide a finite-dimensional model of the twisted K-group twisted by any degree three integral cohomology class of a CW complex. One key to the model is Furuta’s generalized vector bundle, and the other is a finite-dimensional approximation of Fredholm operators.

  11. Heat transfer and fluid friction in bundles of twisted tubes

    NASA Astrophysics Data System (ADS)

    Dzyubenko, B. V.; Dreitser, G. A.

    1986-06-01

    The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.

  12. Beyond the classical Rayleigh limit with twisted light.

    PubMed

    Tong, Zhisong; Korotkova, Olga

    2012-07-01

    It is shown that twisted stochastic light can serve as illumination that may produce images with a resolution overcoming the Rayleigh limit by an order of magnitude. This finding is illustrated for an isoplanatic axially symmetric system with low angular aperture and twisted scalar Gaussian Schell-model illumination. PMID:22743466

  13. An electronic control for an electrohydraulic active control landing gear for the F-4 aircraft

    NASA Technical Reports Server (NTRS)

    Ross, I.

    1982-01-01

    A controller for an electrohydraulic active control landing gear was developed for the F-4 aircraft. A controller was modified for this application. Simulation results indicate that during landing and rollout over repaired bomb craters the active gear effects a force reduction, relative to the passive gear, or approximately 70%.

  14. Hybrid Architecture Active Wavefront Sensing and Control

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee; Dean, Bruce; Hyde, Tupper

    2010-01-01

    A method was developed for performing relatively high-speed wavefront sensing and control to overcome thermal instabilities in a segmented primary mirror telescope [e.g., James Webb Space Telescope (JWST) at L2], by using the onboard fine guidance sensor (FGS) to minimize expense and complexity. This FGS performs centroiding on a bright star to feed the information to the pointing and control system. The proposed concept is to beam split the image of the guide star (or use a single defocused guide star image) to perform wavefront sensing using phase retrieval techniques. Using the fine guidance sensor star image for guiding and fine phasing eliminates the need for other, more complex ways of achieving very accurate sensing and control that is needed for UV-optical applications. The phase retrieval occurs nearly constantly, so passive thermal stability over fourteen days is not required. Using the FGS as the sensor, one can feed segment update information to actuators on the primary mirror that can update the primary mirror segment fine phasing with this frequency. Because the thermal time constants of the primary mirror are very slow compared to this duration, the mirror will appear extremely stable during observations (to the level of accuracy of the sensing and control). The sensing can use the same phase retrieval techniques as the JWST by employing an additional beam splitter, and having each channel go through a weak lens (one positive and one negative). The channels can use common or separate detectors. Phase retrieval can be performed onboard. The actuation scheme would include a coarse stage able to achieve initial alignment of several millimeters of range (similar to JWST and can use a JWST heritage sensing approach in the science camera) and a fine stage capable of continual updates.

  15. Active control for turbulent premixed flame simulations

    SciTech Connect

    Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.

    2004-03-26

    Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.

  16. Implementation and application of a novel 2D magnetic twisting cytometry based on multi-pole electromagnet

    NASA Astrophysics Data System (ADS)

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2016-06-01

    We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model.

  17. Implementation and application of a novel 2D magnetic twisting cytometry based on multi-pole electromagnet.

    PubMed

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2016-06-01

    We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model. PMID:27370475

  18. Elements of active vibration control for rotating machinery

    NASA Technical Reports Server (NTRS)

    Ulbrich, Heinz

    1990-01-01

    The success or failure of active vibration control is determined by the availability of suitable actuators, modeling of the entire system including all active elements, positioning of the actuators and sensors, and implementation of problem-adapted control concepts. All of these topics are outlined and their special problems are discussed in detail. Special attention is given to efficient modeling of systems, especially for considering the active elements. Finally, design methods for and the application of active vibration control on rotating machinery are demonstrated by several real applications.

  19. A Hybrid Nonlinear Control Scheme for Active Magnetic Bearings

    NASA Technical Reports Server (NTRS)

    Xia, F.; Albritton, N. G.; Hung, J. Y.; Nelms, R. M.

    1996-01-01

    A nonlinear control scheme for active magnetic bearings is presented in this work. Magnet winding currents are chosen as control inputs for the electromechanical dynamics, which are linearized using feedback linearization. Then, the desired magnet currents are enforced by sliding mode control design of the electromagnetic dynamics. The overall control scheme is described by a multiple loop block diagram; the approach also falls in the class of nonlinear controls that are collectively known as the 'integrator backstepping' method. Control system hardware and new switching power electronics for implementing the controller are described. Various experiments and simulation results are presented to demonstrate the concepts' potentials.

  20. Effect of DNA hairpin loops on the twist of planar DNA origami tiles.

    PubMed

    Li, Zhe; Wang, Lei; Yan, Hao; Liu, Yan

    2012-01-31

    The development of scaffolded DNA origami, a technique in which a long single-stranded viral genome is folded into arbitrary shapes by hundreds of short synthetic oligonucleotides, represents an important milestone in DNA nanotechnology. Recent findings have revealed that two-dimensional (2D) DNA origami structures based on the original design parameters adopt a global twist with respect to the tile plane, which may be because the conformation of the constituent DNA (10.67 bp/turn) deviates from the natural B-type helical twist (10.4 bp/turn). Here we aim to characterize the effects of DNA hairpin loops on the overall curvature of the tile and explore their ability to control, and ultimately eliminate any unwanted curvature. A series of dumbbell-shaped DNA loops were selectively displayed on the surface of DNA origami tiles with the expectation that repulsive interactions among the neighboring dumbbell loops and between the loops and the DNA origami tile would influence the structural features of the underlying tiles. A systematic, atomic force microscopy (AFM) study of how the number and position of the DNA loops influenced the global twist of the structure was performed, and several structural models to explain the results were proposed. The observations unambiguously revealed that the first generation of rectangular shaped origami tiles adopt a conformation in which the upper right (corner 2) and bottom left (corner 4) corners bend upward out of the plane, causing linear superstructures attached by these corners to form twisted ribbons. Our experimental observations are consistent with the twist model predicted by the DNA mechanical property simulation software CanDo. Through the systematic design and organization of various numbers of dumbbell loops on both surfaces of the tile, a nearly planar rectangular origami tile was achieved. PMID:22126326

  1. Landau damping of Langmuir twisted waves with kappa distributed electrons

    SciTech Connect

    Arshad, Kashif Aman-ur-Rehman; Mahmood, Shahzad

    2015-11-15

    The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].

  2. A twisted disk equation that describes warped galaxy disks

    NASA Technical Reports Server (NTRS)

    Barker, K.

    1994-01-01

    Warped H1 gas layers in the outer regions of spiral galaxies usually display a noticeably twisted structure. This structure is thought to arise primarily as a result of differential precession in the H1 disk as it settles toward a 'preferred orientation' in an underlying dark halo potential well that is not spherically symmetric. In an attempt to better understand the structure and evolution of these twisted, warped disk structures, we have utilized the 'twist-equation' formalism. Specifically, we have generalized the twist equation to allow the treatment of non-Keplerian disks and from it have derived the steady-state structure of twisted disks that develop from free precession in a nonspherical, logarithmic halo potential. This generalized equation can also be used to examine the time-evolutionary behavior of warped galaxy disks.

  3. Landau damping of Langmuir twisted waves with kappa distributed electrons

    NASA Astrophysics Data System (ADS)

    Arshad, Kashif; Aman-ur-Rehman, Mahmood, Shahzad

    2015-11-01

    The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].

  4. Colloquium: Geometry and optimal packing of twisted columns and filaments

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    2015-04-01

    This Colloquium presents recent progress in understanding constraints and consequences of close-packing geometry of filamentous or columnar materials possessing nontrivial textures, focusing, in particular, on the common motifs of twisted and toroidal structures. The mathematical framework is presented that relates spacing between linelike, filamentous elements to their backbone orientations, highlighting the explicit connection between the interfilament metric properties and the geometry of non-Euclidean surfaces. The consequences of the hidden connection between packing in twisted filament bundles and packing on positively curved surfaces, like the Thomson problem, are demonstrated for the defect-riddled ground states of physical models of twisted filament bundles. The connection between the "ideal" geometry of fibrations of curved three-dimensional space, including the Hopf fibration, and the non-Euclidean constraints of filament packing in twisted and toroidal bundles is presented, with a focus on the broader dependence of metric geometry on the simultaneous twisting and folding of multifilament bundles.

  5. An active control synchronization for two modified Chua circuits

    NASA Astrophysics Data System (ADS)

    Li, Guo-Hui

    2005-03-01

    From modern control theory, an active control method to synchronize two modified Chua circuits with each other, which exhibit chaos, is presented. Some sufficient conditions of linear stability of the chaotic synchronization are obtained from rigorous mathematic justification. On the basis of the state-observer, the controller is analytically deduced using the active control. It is shown that this technique can be applied to achieve synchronization of the two systems with each other, whether they are identical or not. Finally, numerical simulations show the effectiveness of the proposed control scheme.

  6. Thermal and non-thermal emission from reconnecting twisted coronal loops

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Gordovskyy, M.; Browning, P. K.; Vilmer, N.

    2016-01-01

    Context. Twisted magnetic fields should be ubiquitous in the solar corona, particularly in flare-producing active regions where the magnetic fields are strongly non-potential. The magnetic energy contained in such twisted fields can be released during solar flares and other explosive phenomena. It has recently been shown that reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops. Hence, the magnetic reconnection and particle acceleration scenario involving magnetic helicity can be a viable alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. Aims: The key goal of this study is to investigate the links and observational signatures of plasma heating and particle acceleration in kink-unstable twisted coronal loops. Methods: We used a combination of magnetohydrodynamic (MHD) simulations and test-particle methods. These simulations describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us estimate thermal X-ray emission intensities. With the electric and magnetic fields we obtained, we calculated electron trajectories using the guiding-centre approximation. These trajectories combined with the MHD plasma density distributions let us deduce synthetic hard X-ray bremsstrahlung intensities. Results: Our simulations emphasise that the geometry of the emission patterns produced by hot plasma in flaring twisted coronal loops can differ from the actual geometry of the underlying magnetic fields. In particular, the twist angles revealed by the emission threads (soft X-ray thermal emission; SXR) are consistently lower than the field-line twist present at the onset of the

  7. Active control of compressible flows on a curved surface

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Parikh, P.; Bayliss, A.; Turkel, E.

    1985-01-01

    The effect of localized, time periodic surface heating and cooling over a curved surface is studied. This is a mechanism for the active control of unstable disturbances by phase cancellation and reinforcement. It is shown that the pressure gradient induced by the curvature significantly enhances the effectiveness of this form of active control. In particular, by appropriate choice of phase, active surface heating can completely stabilize and unstable wave.

  8. Generalized internal model robust control for active front steering intervention

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Zhao, Youqun; Ji, Xuewu; Liu, Yahui; Zhang, Lipeng

    2015-03-01

    Because of the tire nonlinearity and vehicle's parameters' uncertainties, robust control methods based on the worst cases, such as H ∞, µ synthesis, have been widely used in active front steering control, however, in order to guarantee the stability of active front steering system (AFS) controller, the robust control is at the cost of performance so that the robust controller is a little conservative and has low performance for AFS control. In this paper, a generalized internal model robust control (GIMC) that can overcome the contradiction between performance and stability is used in the AFS control. In GIMC, the Youla parameterization is used in an improved way. And GIMC controller includes two sections: a high performance controller designed for the nominal vehicle model and a robust controller compensating the vehicle parameters' uncertainties and some external disturbances. Simulations of double lane change (DLC) maneuver and that of braking on split- µ road are conducted to compare the performance and stability of the GIMC control, the nominal performance PID controller and the H ∞ controller. Simulation results show that the high nominal performance PID controller will be unstable under some extreme situations because of large vehicle's parameters variations, H ∞ controller is conservative so that the performance is a little low, and only the GIMC controller overcomes the contradiction between performance and robustness, which can both ensure the stability of the AFS controller and guarantee the high performance of the AFS controller. Therefore, the GIMC method proposed for AFS can overcome some disadvantages of control methods used by current AFS system, that is, can solve the instability of PID or LQP control methods and the low performance of the standard H ∞ controller.

  9. Controlling interneuron activity in Caenorhabditis elegans to evoke chemotactic behaviour.

    PubMed

    Kocabas, Askin; Shen, Ching-Han; Guo, Zengcai V; Ramanathan, Sharad

    2012-10-11

    Animals locate and track chemoattractive gradients in the environment to find food. With its small nervous system, Caenorhabditis elegans is a good model system in which to understand how the dynamics of neural activity control this search behaviour. Extensive work on the nematode has identified the neurons that are necessary for the different locomotory behaviours underlying chemotaxis through the use of laser ablation, activity recording in immobilized animals and the study of mutants. However, we do not know the neural activity patterns in C. elegans that are sufficient to control its complex chemotactic behaviour. To understand how the activity in its interneurons coordinate different motor programs to lead the animal to food, here we used optogenetics and new optical tools to manipulate neural activity directly in freely moving animals to evoke chemotactic behaviour. By deducing the classes of activity patterns triggered during chemotaxis and exciting individual neurons with these patterns, we identified interneurons that control the essential locomotory programs for this behaviour. Notably, we discovered that controlling the dynamics of activity in just one interneuron pair (AIY) was sufficient to force the animal to locate, turn towards and track virtual light gradients. Two distinct activity patterns triggered in AIY as the animal moved through the gradient controlled reversals and gradual turns to drive chemotactic behaviour. Because AIY neurons are post-synaptic to most chemosensory and thermosensory neurons, it is probable that these activity patterns in AIY have an important role in controlling and coordinating different taxis behaviours of the animal. PMID:23000898

  10. Active laser system for sea ice control

    NASA Astrophysics Data System (ADS)

    Evtikhiev, Nickolay N.; Gaponov, Alexandr E.; Kuluba, Yury N.; Matous, Vladislav I.; Radominov, Oleg E.; Tuzikov, Vladimir Z.; Vargaftic, Vasiliy N.

    1997-01-01

    The airborne systems are used for complex investigations of coastline very successfully, for example it can be used to measure the depth of the sea, to discover the reefs and so on. Such information may be used in navigation too. The specific conditions of navigation in the North and Pole seas defines the necessity of exact knowledge about the ice cracks in order to find the possible direction of the ship movement. The active optical system, working in the near IR region, has many advantages before the passive one, especially if it is necessary to work during the polar night and at bad weather conditions. In this article we discuss the demands to the laser active airborne systems, that given the accurate picture of the ice with high resolution in the daytime and nighttime conditions. Such system based on the laser, mechanical scanner and avalanche photodiode is very compact, reliable and informative. The picture of the ice surface can be shown on the TV monitor, can be written to the memory and can be delivered to the processing center by the radiochannel. The experimental results are shown together with results of this system probing in the conditions of the North Pole Ocean.

  11. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy.

    PubMed

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-01-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order. PMID:26530779

  12. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy

    PubMed Central

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-01-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order. PMID:26530779

  13. Double-twist cylinders in liquid crystalline cholesteric blue phases observed by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Tanaka, Shu; Yoshida, Hiroyuki; Kawata, Yuto; Kuwahara, Ryusuke; Nishi, Ryuji; Ozaki, Masanori

    2015-11-01

    Cholesteric blue phases are liquid crystalline phases in which the constituent rod-like molecules spontaneously form three-dimensional, helical structures. Despite theoretical predictions that they are composed of cylindrical substructures within which the liquid crystal molecules are doubly twisted, real space observation of the arrangement of such structures had not been performed. Through transmission electron microscopy of photopolymerized blue phases with controlled lattice plane orientations, we report real space observation and comparison of the lattice structures of blue phases I and II. The two systems show distinctly different contrasts, reflecting the theoretically predicted, body centred and simple cubic arrangement of the double-twist cylinders. Transmission electron microscopy also reveals different tendencies of the two blue phases to align on unidirectionally rubbed surfaces. We thus show that TEM observation of alignment-controlled, photopolymerized liquid crystals can be a powerful tool to investigate complex liquid crystalline order.

  14. Study of tethered satellite active attitude control

    NASA Technical Reports Server (NTRS)

    Colombo, G.

    1982-01-01

    Existing software was adapted for the study of tethered subsatellite rotational dynamics, an analytic solution for a stable configuration of a tethered subsatellite was developed, the analytic and numerical integrator (computer) solutions for this "test case' was compared in a two mass tether model program (DUMBEL), the existing multiple mass tether model (SKYHOOK) was modified to include subsatellite rotational dynamics, the analytic "test case,' was verified, and the use of the SKYHOOK rotational dynamics capability with a computer run showing the effect of a single off axis thruster on the behavior of the subsatellite was demonstrated. Subroutines for specific attitude control systems are developed and applied to the study of the behavior of the tethered subsatellite under realistic on orbit conditions. The effect of all tether "inputs,' including pendular oscillations, air drag, and electrodynamic interactions, on the dynamic behavior of the tether are included.

  15. Combustion diagnostic for active engine feedback control

    DOEpatents

    Green, Jr., Johney Boyd; Daw, Charles Stuart; Wagner, Robert Milton

    2007-10-02

    This invention detects the crank angle location where combustion switches from premixed to diffusion, referred to as the transition index, and uses that location to define integration limits that measure the portions of heat released during the combustion process that occur during the premixed and diffusion phases. Those integrated premixed and diffusion values are used to develop a metric referred to as the combustion index. The combustion index is defined as the integrated diffusion contribution divided by the integrated premixed contribution. As the EGR rate is increased enough to enter the low temperature combustion regime, PM emissions decrease because more of the combustion process is occurring over the premixed portion of the heat release rate profile and the diffusion portion has been significantly reduced. This information is used to detect when the engine is or is not operating in a low temperature combustion mode and provides that feedback to an engine control algorithm.

  16. Active control system for high speed windmills

    DOEpatents

    Avery, D.E.

    1988-01-12

    A pump stroke is matched to the operating speed of a high speed windmill. The windmill drives a hydraulic pump for a control. Changes in speed of a wind driven shaft open supply and exhaust valves to opposite ends of a hydraulic actuator to lengthen and shorten an oscillating arm thereby lengthening and shortening the stroke of an output pump. Diminishing wind to a stall speed causes the valves to operate the hydraulic cylinder to shorten the oscillating arm to zero. A pressure accumulator in the hydraulic system provides the force necessary to supply the hydraulic fluid under pressure to drive the actuator into and out of the zero position in response to the windmill shaft speed approaching and exceeding windmill stall speed. 4 figs.

  17. Active control system for high speed windmills

    DOEpatents

    Avery, Don E.

    1988-01-01

    A pump stroke is matched to the operating speed of a high speed windmill. The windmill drives a hydraulic pump for a control. Changes in speed of a wind driven shaft open supply and exhaust valves to opposite ends of a hydraulic actuator to lengthen and shorten an oscillating arm thereby lengthening and shortening the stroke of an output pump. Diminishing wind to a stall speed causes the valves to operate the hydraulic cylinder to shorten the oscillating arm to zero. A pressure accumulator in the hydraulic system provides the force necessary to supply the hydraulic fluid under pressure to drive the actuator into and out of the zero position in response to the windmill shaft speed approaching and exceeding windmill stall speed.

  18. Do twisted laser beams evoke nuclear hyperpolarization?

    NASA Astrophysics Data System (ADS)

    Schmidt, A. B.; Andrews, D. L.; Rohrbach, A.; Gohn-Kreuz, C.; Shatokhin, V. N.; Kiselev, V. G.; Hennig, J.; von Elverfeldt, D.; Hövener, J.-B.

    2016-07-01

    The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5 nm and various topological charges. We acquired 1H and 19F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5 mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be

  19. Do twisted laser beams evoke nuclear hyperpolarization?

    PubMed

    Schmidt, A B; Andrews, D L; Rohrbach, A; Gohn-Kreuz, C; Shatokhin, V N; Kiselev, V G; Hennig, J; von Elverfeldt, D; Hövener, J-B

    2016-07-01

    The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5nm and various topological charges. We acquired (1)H and (19)F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be

  20. Identification and characterization of a twist ortholog in the polychaete annelid Platynereis dumerilii reveals mesodermal expression of Pdu-twist.

    PubMed

    Pfeifer, Kathrin; Schaub, Christoph; Wolfstetter, Georg; Dorresteijn, Adriaan

    2013-09-01

    The basic helix-loop-helix transcription factor twist plays a key role during mesoderm development in Bilateria. In this study, we identified a twist ortholog in the polychaete annelid Platynereis dumerilii and analyze its expression during larval development, postlarval growth up to the adult stage, and caudal regeneration after amputation of posterior segments. At late larval stages, Pdu-twist is expressed in the mesodermal anlagen and in developing muscles. During adulthood and caudal regeneration, Pdu-twist is expressed in the posterior growth zone, in mesodermal cells within the newly forming segments and budding parapodia. Our results indicate that Pdu-twist is involved in mesoderm formation during larval development, posterior growth, and caudal regeneration. PMID:23817621

  1. Control of sound radiation with active/adaptive structures

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Rogers, C. A.; Robertshaw, H. H.

    1992-01-01

    Recent research is discussed in the area of active structural acoustic control with active/adaptive structures. Progress in the areas of structural acoustics, actuators, sensors, and control approaches is presented. Considerable effort has been given to the interaction of these areas with each other due to the coupled nature of the problem. A discussion is presented on actuators bonded to or embedded in the structure itself. The actuators discussed are piezoceramic actuators and shape memory alloy actuators. The sensors discussed are optical fiber sensors, Nitinol fiber sensors, piezoceramics, and polyvinylidene fluoride sensors. The active control techniques considered are state feedback control techniques and least mean square adaptive algorithms. Results presented show that significant progress has been made towards controlling structurally radiated noise by active/adaptive means applied directly to the structure.

  2. Numerical evaluation of the performance of active noise control systems

    NASA Technical Reports Server (NTRS)

    Mollo, C. G.; Bernhard, R. J.

    1990-01-01

    This paper presents a generalized numerical technique for evaluating the optimal performance of active noise controllers. In this technique, the indirect BEM numerical procedures are used to derive the active noise controllers for optimal control of enclosed harmonic sound fields where the strength of the noise sources or the description of the enclosure boundary may not be known. The performance prediction for a single-input single-output system is presented, together with the analysis of the stability and observability of an active noise-control system employing detectors. The numerical procedures presented can be used for the design of both the physical configuration and the electronic components of the optimal active noise controller.

  3. Wireless sensor networks for active vibration control in automobile structures

    NASA Astrophysics Data System (ADS)

    Mieyeville, Fabien; Ichchou, Mohamed; Scorletti, Gérard; Navarro, David; Du, Wan

    2012-07-01

    Wireless sensor networks (WSNs) are nowadays widely used in monitoring and tracking applications. This paper presents the feasibility of using WSNs in active vibration control strategies. The method employed here involves active-structural acoustic control using piezoelectric sensors distributed on a car structure. This system aims at being merged with a WSN whose head node collects data and processes control laws so as to command piezoelectric actuators wisely placed on the structure. We will study the feasibility of implementing WSNs in active vibration control and introduce a complete design methodology to optimize hardware/software and control law synergy in mechatronic systems. A design space exploration will be conducted so as to identify the best WSN platform and the resulting impact on control.

  4. Imprinted control of gene activity in Drosophila.

    PubMed

    Golic, K G; Golic, M M; Pimpinelli, S

    1998-11-19

    Genetic imprinting is defined as a reversible, differential marking of genes or chromosomes that is determined by the sex of the parent from whom the genetic material is inherited [1]. Imprinting was first observed in insects where, in some species, most notably among the coccoids (scale insects and allies), the differential marking of paternally and maternally transmitted chromosome sets leads to inactivation or elimination of paternal chromosomes [2]. Imprinting is also widespread in plants and mammals [3,4], in which paternally and maternally inherited alleles may be differentially expressed. Despite imprinting having been discovered in insects, clear examples of parental imprinting are scarce in the model insect species Drosophila melanogaster. We describe a case of imprint-mediated control of gene expression in Drosophila. The imprinted gene - the white+ eye-color gene - is expressed at a low level when transmitted by males, and at a high level when transmitted by females. Thus, in common with coccoids, Drosophila is capable of generating an imprint, and can respond to that imprint by silencing the paternal allele. PMID:9822579

  5. Various applications of Active Field Control (AFC)

    NASA Astrophysics Data System (ADS)

    Watanabe, Takayuki; Miyazaki, Hideo; Kishinaga, Shinji; Kawakami, Fukushi

    2003-10-01

    AFC is an electro-acoustic enhancement system, which has been under development at Yamaha Corporation. In this paper, several types of various AFC applications are discussed, while referring to representative projects for each application in Japan. (1) Realization of acoustics in a huge hall to classical music program, e.g., Tokyo International Forum. This venue is a multipurpose hall with approximately 5000 seats. AFC achieves loudness and reverberance equivalent to those of a hall with 2500 seats or fewer. (2) Optimization of acoustics for a variety of programs, e.g., Arkas Sasebo. AFC is used to create the optimum acoustics for each program, such as reverberance for classical concerts, acoustical support for opera singers, uniformity throughout the hall from the stage to under-balcony area, etc. (3) Control of room shape acoustical effect, e.g., Osaka Central Public Hall: In this renovation project, preservation of historically important architecture in the original form is required. AFC is installed to vary only the acoustical environment without architectural changes. (4) Assistance with crowd enthusiasm for sports entertainment, e.g., Tokyo Metropolitan Gymnasium. In this venue, which is designed as a very absorptive space for speech intelligibility, AFC is installed to enhance the atmosphere of live sports entertainment.

  6. An evolutionarily conserved DNA architecture determines target specificity of the TWIST family bHLH transcription factors

    PubMed Central

    Chang, Andrew T.; Liu, Yuanjie; Ayyanathan, Kasirajan; Benner, Chris; Jiang, Yike; Prokop, Jeremy W.; Paz, Helicia; Wang, Dong; Li, Hai-Ri; Fu, Xiang-Dong

    2015-01-01

    Basic helix–loop–helix (bHLH) transcription factors recognize the canonical E-box (CANNTG) to regulate gene transcription; however, given the prevalence of E-boxes in a genome, it has been puzzling how individual bHLH proteins selectively recognize E-box sequences on their targets. TWIST is a bHLH transcription factor that promotes epithelial–mesenchymal transition (EMT) during development and tumor metastasis. High-resolution mapping of TWIST occupancy in human and Drosophila genomes reveals that TWIST, but not other bHLH proteins, recognizes a unique double E-box motif with two E-boxes spaced preferentially by 5 nucleotides. Using molecular modeling and binding kinetic analyses, we found that the strict spatial configuration in the double E-box motif aligns two TWIST–E47 dimers on the same face of DNA, thus providing a high-affinity site for a highly stable intramolecular tetramer. Biochemical analyses showed that the WR domain of TWIST dimerizes to mediate tetramer formation, which is functionally required for TWIST-induced EMT. These results uncover a novel mechanism for a bHLH transcription factor to recognize a unique spatial configuration of E-boxes to achieve target specificity. The WR–WR domain interaction uncovered here sets an example of target gene specificity of a bHLH protein being controlled allosterically by a domain outside of the bHLH region. PMID:25762439

  7. Optical Twist Induced by Plasmonic Resonance

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Wang, Neng; Cui, Liyong; Li, Xiao; Lin, Zhifang; Ng, Jack

    2016-06-01

    Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster.

  8. Twists and turns: a scientific journey.

    PubMed

    Tilghman, Shirley M

    2014-01-01

    In this perspective I look back on the twists and turns that influenced the direction of my scientific career over the past 40 years. From my early ambition to be a chemist to my training in Philadelphia and Bethesda as a molecular biologist, I benefited enormously from generous and valuable mentoring. In my independent career in Philadelphia and Princeton, I was motivated by a keen interest in the changes in gene expression that direct the development of the mammalian embryo and inspired by the creativity and energy of my students, fellows, and research staff. After twelve years as President of Princeton University, I have happily returned to the faculty of the Department of Molecular Biology. PMID:25288111

  9. Twisting of light around rotating black holes

    NASA Astrophysics Data System (ADS)

    Tamburini, Fabrizio; Thidé, Bo; Molina-Terriza, Gabriel; Anzolin, Gabriele

    2011-03-01

    Kerr black holes are among the most intriguing predictions of Einstein's general relativity theory. These rotating massive astrophysical objects drag and intermix their surrounding space and time, deflecting and phase-modifying light emitted near them. We have found that this leads to a new relativistic effect that imprints orbital angular momentum on such light. Numerical experiments, based on the integration of the null geodesic equations of light from orbiting point-like sources in the Kerr black hole equatorial plane to an asymptotic observer, indeed identify the phase change and wavefront warping and predict the associated light-beam orbital angular momentum spectra. Setting up the best existing telescopes properly, it should be possible to detect and measure this twisted light, thus allowing a direct observational demonstration of the existence of rotating black holes. As non-rotating objects are more an exception than a rule in the Universe, our findings are of fundamental importance.

  10. The twisted diversion: a paralyzing complication

    PubMed Central

    Hiew, Kenneth; Glendinning, Richard; Parr, Nigel; Kumar, Manal

    2013-01-01

    Ileal conduit remains a widely used urinary diversion performed after radical cystectomy. However, complications of ileal conduits remain an important concern in urological surgery. We report a rare case of an ileal conduit stricture, which can have grim complications if unobserved during the operation. Following an initial operation of radical cystectomy and ileal conduit formation in France in 2011, an 80-year-old male travelled back to the UK after 4 months of general weakness and limb paralysis. Initial blood test shows life-threatening hyperkalemia and worsened renal function. Subsequent ultrasound KUB scan and loopogram revealed obstructive uropathy. The initial management includes intravenous antibiotics and bilateral nephrostomies were inserted to aid diversion of urine. A thorough surgical exploration revealed a twisted, fibrous mesenteric band adhered to the proximal part of the ileal conduit. Only one case report of ileal conduit stenosis was described many years after the procedure. PMID:24963928

  11. Optical Twist Induced by Plasmonic Resonance

    PubMed Central

    Chen, Jun; Wang, Neng; Cui, Liyong; Li, Xiao; Lin, Zhifang; Ng, Jack

    2016-01-01

    Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster. PMID:27291860

  12. Bounds on tensor wave and twisted inflation

    SciTech Connect

    Panda, Sudhakar; Sami, M.; Ward, John

    2010-11-15

    We study the bounds on tensor wave in a class of twisted inflation models, where D(4+2k)-branes are wrapped on cycles in the compact manifold and wrap the Kaluza-Klein direction in the corresponding effective field theory. While the lower bound is found to be analogous to that in type IIB models of brane inflation, the upper bound turns out to be significantly different. This is argued for a range of values for the parameter g{sub s}M satisfying the self-consistency relation and the WMAP data. Further, we observe that the wrapped D8-brane appears to be the most attractive from a cosmological perspective.

  13. Optical Twist Induced by Plasmonic Resonance.

    PubMed

    Chen, Jun; Wang, Neng; Cui, Liyong; Li, Xiao; Lin, Zhifang; Ng, Jack

    2016-01-01

    Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster. PMID:27291860

  14. Twisting algebraically special solutions in five dimensions

    NASA Astrophysics Data System (ADS)

    Bernardi de Freitas, Gabriel; Godazgar, Mahdi; Reall, Harvey S.

    2016-05-01

    We determine the general form of the solutions of the five-dimensional vacuum Einstein equations with cosmological constant for which (i) the Weyl tensor is everywhere type II or more special in the null alignment classification of Coley et al, and (ii) the 3 × 3 matrix encoding the expansion, shear and twist of the aligned null direction has rank 2. The dependence of the solution on two coordinates is determined explicitly, so the Einstein equation reduces to PDEs in the three remaining coordinates, just as for four-dimensional (4d) algebraically special solutions. The solutions fall into several families. One of these consists of warped products of 4d algebraically special solutions. The others are new.

  15. On-line Monitoring and Active Control for Transformer Noise

    NASA Astrophysics Data System (ADS)

    Liang, Jiabi; Zhao, Tong; Tian, Chun; Wang, Xia; He, Zhenhua; Duan, Lunfeng

    This paper introduces the system for on-line monitoring and active noise control towards the transformer noise based on LabVIEW and the hardware equipment including the hardware and software. For the hardware part, it is mainly focused on the composition and the role of hardware devices, as well as the mounting location in the active noise control experiment. And the software part introduces the software flow chats, the measurement and analysis module for the sound pressure level including A, B, C weighting methods, the 1/n octave spectrum and the power spectrum, active noise control module and noise data access module.

  16. [Actuator placement for active sound and vibration control

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Two refereed journal publications and ten talks given at conferences, seminars, and colloquia resulted from research supported by NASA. They are itemized in this report. The two publications were entitled "Reactive Tabu and Search Sensor Selection in Active Structural Acoustic Control Problems" and "Quelling Cabin Noise in Turboprop Aircraft via Active Control." The conference presentations covered various aspects of actuator placement, including location problems, for active sound and vibration control of cylinders, of commuter jets, of propeller driven or turboprop aircraft, and for quelling aircraft cabin or interior noise.

  17. Active airborne contamination control using electrophoresis

    SciTech Connect

    Veatch, B.D.

    1994-06-01

    In spite of our best efforts, radioactive airborne contamination continues to be a formidable problem at many of the Department of Energy (DOE) weapons complex sites. For workers that must enter areas with high levels of airborne contamination, personnel protective equipment (PPE) can become highly restrictive, greatly diminishing productivity. Rather than require even more restrictive PPE for personnel in some situations, the Rocky Flats Plant (RFP) is actively researching and developing methods to aggressively combat airborne contamination hazards using electrophoretic technology. With appropriate equipment, airborne particulates can be effectively removed and collected for disposal in one simple process. The equipment needed to implement electrophoresis is relatively inexpensive, highly reliable, and very compact. Once airborne contamination levels are reduced, less PPE is required and a significant cost savings may be realized through decreased waste and maximized productivity. Preliminary ``cold,`` or non-radioactive, testing results at the RFP have shown the technology to be effective on a reasonable scale, with several potential benefits and an abundance of applications.

  18. The Twisting Jet from the Vela Pulsar

    NASA Astrophysics Data System (ADS)

    Teter, M. A.; Pavlov, G. G.; Sanwal, D.; Kargaltsev, O.

    2002-05-01

    Observations of the Vela pulsar-wind nebula (PWN) with Chandra have revealed a long, thin filament -- an extension of the pulsar's jet beyond the bright outer arc confining the PWN in the direction of the pulsar's proper motion. This curved external jet terminates in a region of enhanced emission (a blob) at a distance of about 100'' (0.15 pc) from the pulsar, larger than the size of the PWN. The shape of the jet and its brightness are seen to vary on a timescale as short as a few days, its remote parts move in the sky plane with apparent velocities of up to 0.2 c. The X-ray spectrum of the external jet, including the termination blob, shows no spectral features. It is well described by a power-law model with a photon-index of γ ~= 1.2 (slightly harder than the average spectrum of the PWN, γ ~= 1.5). This indicates that the jet's radiation is due to synchrotron emission of relativistic particles in a magnetic field. The fact that the jet remains confined, although it twists at large distances from the pulsar, suggests a self-confining structure of its magnetic field. The varying shape and intensity of this stream of relativistic particles can be associated with varying local conditions in the Vela SNR and/or large-scale MHD instabilities and internal variations of the magnetic field within the jet. We will present a movie with a sequence of 12 Chandra images over past two years, demonstrating the structure of the twisting jet, and discuss various interpretations of these observations. The work was partially supported by SAO grant GO2-3091X and NASA grant NAG5-10865.

  19. The aircraft energy efficiency active controls technology program

    NASA Technical Reports Server (NTRS)

    Hood, R. V., Jr.

    1977-01-01

    Broad outlines of the NASA Aircraft Energy Efficiency Program for expediting the application of active controls technology to civil transport aircraft are presented. Advances in propulsion and airframe technology to cut down on fuel consumption and fuel costs, a program for an energy-efficient transport, and integrated analysis and design technology in aerodynamics, structures, and active controls are envisaged. Fault-tolerant computer systems and fault-tolerant flight control system architectures are under study. Contracts with leading manufacturers for research and development work on wing-tip extensions and winglets for the B-747, a wing load alleviation system, elastic mode suppression, maneuver-load control, and gust alleviation are mentioned.

  20. Active controls: A look at analytical methods and associated tools

    NASA Technical Reports Server (NTRS)

    Newsom, J. R.; Adams, W. M., Jr.; Mukhopadhyay, V.; Tiffany, S. H.; Abel, I.

    1984-01-01

    A review of analytical methods and associated tools for active controls analysis and design problems is presented. Approaches employed to develop mathematical models suitable for control system analysis and/or design are discussed. Significant efforts have been expended to develop tools to generate the models from the standpoint of control system designers' needs and develop the tools necessary to analyze and design active control systems. Representative examples of these tools are discussed. Examples where results from the methods and tools have been compared with experimental data are also presented. Finally, a perspective on future trends in analysis and design methods is presented.