Rigidity of transmembrane proteins determines their cluster shape

NASA Astrophysics Data System (ADS)

Jafarinia, Hamidreza; Khoshnood, Atefeh; Jalali, Mir Abbas

2016-01-01

Protein aggregation in cell membrane is vital for the majority of biological functions. Recent experimental results suggest that transmembrane domains of proteins such as α -helices and β -sheets have different structural rigidities. We use molecular dynamics simulation of a coarse-grained model of protein-embedded lipid membranes to investigate the mechanisms of protein clustering. For a variety of protein concentrations, our simulations under thermal equilibrium conditions reveal that the structural rigidity of transmembrane domains dramatically affects interactions and changes the shape of the cluster. We have observed stable large aggregates even in the absence of hydrophobic mismatch, which has been previously proposed as the mechanism of protein aggregation. According to our results, semiflexible proteins aggregate to form two-dimensional clusters, while rigid proteins, by contrast, form one-dimensional string-like structures. By assuming two probable scenarios for the formation of a two-dimensional triangular structure, we calculate the lipid density around protein clusters and find that the difference in lipid distribution around rigid and semiflexible proteins determines the one- or two-dimensional nature of aggregates. It is found that lipids move faster around semiflexible proteins than rigid ones. The aggregation mechanism suggested in this paper can be tested by current state-of-the-art experimental facilities.

Structural Crashworthiness and Failure

DTIC Science & Technology

1993-04-16

body motion occurs. This rigid -plastic idealization for dynamically loaded structures is based upon the fact that the plastic deformation of a...in general, for any tensor variable x, i represents the convective derivative. It should be noted that the rigid body rotation is included in the...clamped, impulsively loaded, rigid - plastic beam.’ (a) First phase of motion with stationary transverse plastic hinges at A and E and stationary plastic

Characterization of Physical Structure from Measurements of Sound Velocity in Aqueous Solutions of Various Saccharides and Alditols.

NASA Astrophysics Data System (ADS)

Smith, David Eugene

Little basic research has been reported on the physical structure of aqueous solutions of saccharides. Sound velocimeters can be used to study physical structure of solutions, non-destructively. The La Place relationship was used to calculate adiabatic compressibility values for solutions from experimentally determined values for sound velocity and density. Using a sound velocimeter, aqueous solutions of twelve alditols and saccharides were studied at various concentrations and temperatures. Data indicated that over most of the temperature range employed (20 to 70 C) adiabatic compressibility of the solutions was the dominant factor in defining sound velocity through and structural rigidity of solution. As concentration of solute increased, more rigid structures were formed in solution, which caused sound velocity values to increase with increasing concentrations of solute; maximum sound velocity values were obtained at progressively lower temperatures. Analysis of data for sound velocity, density and adiabatic compressibility of various solutions provided partial insight into effects of each solute molecule on structure of solutions. A furanose form in a monosaccharide contributed to a more rigid structure than did a pyranose ring when below 30C. At higher temperatures the pyranose ring provided more rigidity than did the furanose ring. Hydroxyl groups in the equatorial position generally contributed more to rigidity of structure than did OH groups in axial positions. Disaccharides contributed differences from the inherent monosaccharides. A (beta) glycosidic linkage provided more structural rigidity of solution than did a linkage. Among the alditols, mannitol and sorbitol contributed very similar characteristics to solutions. Xylitol, in solution provided less rigidity, density and sound velocity than did mannitol-sorbitol in proportion to the lower molecular weight or xylitol. From the data for velocity of sound through single sugar solutions values for solutions of mixtures of these sugars at concentrations to 0.9m could be calculated with accuracy. Each sugar contributed independently to structure of solution and sound velocity values. At solute concentrations greater than 0.9m, there appeared to be some interaction among mixed solute molecules in solution.

Nonlinear mechanics of non-rigid origami: an efficient computational approach

NASA Astrophysics Data System (ADS)

Liu, K.; Paulino, G. H.

2017-10-01

Origami-inspired designs possess attractive applications to science and engineering (e.g. deployable, self-assembling, adaptable systems). The special geometric arrangement of panels and creases gives rise to unique mechanical properties of origami, such as reconfigurability, making origami designs well suited for tunable structures. Although often being ignored, origami structures exhibit additional soft modes beyond rigid folding due to the flexibility of thin sheets that further influence their behaviour. Actual behaviour of origami structures usually involves significant geometric nonlinearity, which amplifies the influence of additional soft modes. To investigate the nonlinear mechanics of origami structures with deformable panels, we present a structural engineering approach for simulating the nonlinear response of non-rigid origami structures. In this paper, we propose a fully nonlinear, displacement-based implicit formulation for performing static/quasi-static analyses of non-rigid origami structures based on `bar-and-hinge' models. The formulation itself leads to an efficient and robust numerical implementation. Agreement between real models and numerical simulations demonstrates the ability of the proposed approach to capture key features of origami behaviour.

Nonlinear mechanics of non-rigid origami: an efficient computational approach.

PubMed

Liu, K; Paulino, G H

2017-10-01

Origami-inspired designs possess attractive applications to science and engineering (e.g. deployable, self-assembling, adaptable systems). The special geometric arrangement of panels and creases gives rise to unique mechanical properties of origami, such as reconfigurability, making origami designs well suited for tunable structures. Although often being ignored, origami structures exhibit additional soft modes beyond rigid folding due to the flexibility of thin sheets that further influence their behaviour. Actual behaviour of origami structures usually involves significant geometric nonlinearity, which amplifies the influence of additional soft modes. To investigate the nonlinear mechanics of origami structures with deformable panels, we present a structural engineering approach for simulating the nonlinear response of non-rigid origami structures. In this paper, we propose a fully nonlinear, displacement-based implicit formulation for performing static/quasi-static analyses of non-rigid origami structures based on 'bar-and-hinge' models. The formulation itself leads to an efficient and robust numerical implementation. Agreement between real models and numerical simulations demonstrates the ability of the proposed approach to capture key features of origami behaviour.

Handedness in shearing auxetics creates rigid and compliant structures

NASA Astrophysics Data System (ADS)

Lipton, Jeffrey Ian; MacCurdy, Robert; Manchester, Zachary; Chin, Lillian; Cellucci, Daniel; Rus, Daniela

2018-05-01

In nature, repeated base units produce handed structures that selectively bond to make rigid or compliant materials. Auxetic tilings are scale-independent frameworks made from repeated unit cells that expand under tension. We discovered how to produce handedness in auxetic unit cells that shear as they expand by changing the symmetries and alignments of auxetic tilings. Using the symmetry and alignment rules that we developed, we made handed shearing auxetics that tile planes, cylinders, and spheres. By compositing the handed shearing auxetics in a manner inspired by keratin and collagen, we produce both compliant structures that expand while twisting and deployable structures that can rigidly lock. This work opens up new possibilities in designing chemical frameworks, medical devices like stents, robotic systems, and deployable engineering structures.

The Seismic Design of Waterfront Retaining Structures

DTIC Science & Technology

1993-01-01

of elastic backfill behind a rigid wall .... .......... .. 134 5.2 Pressure distributions on smooth rigid wall for l-g static horizontal body force...135 5.3 Resultant force and resultant moment on smooth rigid wall for l-g static horizontal body force...distributions on smooth rigid wall for 1-g static horizontal body force clearly showed the limitations of Woods simplified procedure when this condi- tion is not

Thin structured rigid body for acoustic absorption

NASA Astrophysics Data System (ADS)

Starkey, T. A.; Smith, J. D.; Hibbins, A. P.; Sambles, J. R.; Rance, H. J.

2017-01-01

We present a thin acoustic metamaterial absorber, comprised of only rigid metal and air, that gives rise to near unity absorption of airborne sound on resonance. This simple, easily fabricated, robust structure comprising a perforated metal plate separated from a rigid wall by a deeply subwavelength channel of air is an ideal candidate for a sound absorbing panel. The strong absorption in the system is attributed to the thermo-viscous losses arising from a sound wave guided between the plate and the wall, defining the subwavelength channel.

Influence of carbon nanotubes on mechanical properties and structure of rigid polyurethane foam

NASA Astrophysics Data System (ADS)

Ciecierska, E.; Jurczyk-Kowalska, M.; Bazarnik, P.; Kulesza, M.; Lewandowska, M.; Kowalski, M.; Krauze, S.

2014-08-01

In this work, the influence of carbon nanotubes addition on foam structure and mechanical properties of rigid polyurethane foam/nanotube composites was investigated. Scanning electron microscopy was performed to reveal the foam porous structure and distribution of carbon nanotubes. To determine the mechanical properties, three point bending tests were carried out.

Analysis on mechanics response of long-life asphalt pavement at moist hot heavy loading area

NASA Astrophysics Data System (ADS)

Xu, Xinquan; Li, Hao; Wu, Chuanhai; Li, Shanqiang

2018-04-01

Based on the durability of semi-rigid base asphalt pavement test road in Guangdong Yunluo expressway, by comparing the mechanics response of modified semi-rigid base, RCC base and inverted semi-rigid base with the state of continuous, using four unit five parameter model to evaluate rut depth of asphalt pavement structure, and through commonly used fatigue life prediction model to evaluate fatigue performance of three types of asphalt pavement structure. Theoretical calculation and four years tracking observation results of test road show that rut depth of modified semi-rigid base asphalt pavement is the minimum, the road performance is the best, and the fatigue performance is the optimal.

Advanced Pavement Design: Finite Element Modeling for Rigid Pavement Joints, Report II: Model Development

DOT National Transportation Integrated Search

1998-03-01

The contribution of a cement-stabilized base course to the strength of the rigid pavement structure is poorly understood. The objective of this research was to obtain data on the response of the rigid pavement slab-joint-foundation system by conducti...

CHEMICAL RIGIDIZATION OF EXPANDABLE STRUCTURES.

DTIC Science & Technology

The objective of this program was to develop a chemical rigidization process that could be activated by an on-command mechanism and be capable of...and rigidized in the high vacuum facilities atWright-Patterson AFB, Ohio and were delivered to the Air Force. A fail-safe chemical rigidization system...have been varied from fifteen minutes to two hours. The chemical system, a vinyl-type monomer, has exhibited a sustained shelf-life, under ambient

Designing of self-deploying origami structures using geometrically misaligned crease patterns

PubMed Central

Saito, Kazuya; Tsukahara, Akira; Okabe, Yoji

2016-01-01

Usually, origami-based morphing structures are designed on the premise of ‘rigid folding’, i.e. the facets and fold lines of origami can be replaced with rigid panels and ideal hinges, respectively. From a structural mechanics viewpoint, some rigid-foldable origami models are overconstrained and have negative degrees of freedom (d.f.). In these cases, the singularity in crease patterns guarantees their rigid foldability. This study presents a new method for designing self-deploying origami using the geometrically misaligned creases. In this method, some facets are replaced by ‘holes’ such that the systems become a 1-d.f. mechanism. These perforated origami models can be folded and unfolded similar to rigid-foldable (without misalignment) models because of their d.f. focusing on the removed facets, the holes will deform according to the motion of the frame of the remaining parts. In the proposed method, these holes are filled with elastic parts and store elastic energy for self-deployment. First, a new extended rigid-folding simulation technique is proposed to estimate the deformation of the holes. Next, the proposed method is applied on arbitrary-size quadrilateral mesh origami. Finally, by using the finite-element method, the authors conduct numerical simulations and confirm the deployment capabilities of the models. PMID:26997884

Designing of self-deploying origami structures using geometrically misaligned crease patterns.

PubMed

Saito, Kazuya; Tsukahara, Akira; Okabe, Yoji

2016-01-01

Usually, origami-based morphing structures are designed on the premise of 'rigid folding', i.e. the facets and fold lines of origami can be replaced with rigid panels and ideal hinges, respectively. From a structural mechanics viewpoint, some rigid-foldable origami models are overconstrained and have negative degrees of freedom (d.f.). In these cases, the singularity in crease patterns guarantees their rigid foldability. This study presents a new method for designing self-deploying origami using the geometrically misaligned creases. In this method, some facets are replaced by 'holes' such that the systems become a 1-d.f. mechanism. These perforated origami models can be folded and unfolded similar to rigid-foldable (without misalignment) models because of their d.f. focusing on the removed facets, the holes will deform according to the motion of the frame of the remaining parts. In the proposed method, these holes are filled with elastic parts and store elastic energy for self-deployment. First, a new extended rigid-folding simulation technique is proposed to estimate the deformation of the holes. Next, the proposed method is applied on arbitrary-size quadrilateral mesh origami. Finally, by using the finite-element method, the authors conduct numerical simulations and confirm the deployment capabilities of the models.

Rigidity of lattice domes

NASA Technical Reports Server (NTRS)

Savelyev, V. A.

1979-01-01

The means of ensuring total rigidity of lattice domes, using comparison with solid shells of 1-3 layers are discussed. Irregularities of manufacture, processing, and other factors are considered, as they relate to diminution of rigidity. The discussion uses the concepts of upper and lower critical loads on the structure in question.

Identification and control of structures in space

NASA Technical Reports Server (NTRS)

Meirovitch, L.; Quinn, R. D.; Norris, M. A.

1984-01-01

The derivation of the equations of motion for the Spacecraft Control Laboratory Experiment (SCOLE) is reported and the equations of motion of a similar structure orbiting the earth are also derived. The structure is assumed to undergo large rigid-body maneuvers and small elastic deformations. A perturbation approach is proposed whereby the quantities defining the rigid-body maneuver are assumed to be relatively large, with the elastic deformations and deviations from the rigid-body maneuver being relatively small. The perturbation equations have the form of linear equations with time-dependent coefficients. An active control technique can then be formulated to permit maneuvering of the spacecraft and simultaneously suppressing the elastic vibration.

Offshore platform structure intended to be installed in arctic waters, subjected to drifting icebergs

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

Kure, G.; Jenssen, D.N.; Naesje, K.

1984-09-11

An offshore platform structure, particularly intended to be installed in waters where drifting iceberg frequently appear, the platform structure being intended to be founded in a sea bed and comprises a substructure, a superstructure rigidly affixed to the substructure and extending vertically up above the sea level supporting a deck superstructure at its upper end. The horizontal cross-sectional area of the substructure is substantially greater than tath of the superstructure. The substructure rigidly supports a fender structure, the fender structure comprising an outer peripherally arranged wall and an inner cylindrical wall the inner and outer wall being rigidly interconnected bymore » means of a plurality of vertical and/or horizontal partition walls, dividing the fender structure into a plurality of cells or compartlents. The fender structure is arranged in spaced relation with respect to the superstructure.« less

Noncovalent Interactions in the Asymmetric Synthesis of Rigid, Conjugated Helical Structures

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

Miyasaka, Makoto; Pink, Maren; Rajca, Suchada

Tetrakis({beta}-trithiophene) 1 folds into a helical conformation (RRR) that facilitates double ring annelation, with high diastereoselectivity and modest enantioselectivity, to provide bis[7]helicene 2 (MRM). This rigid, helically locked structure has enhanced chiroptical properties similar to the corresponding [15]helicene.

Analysis of Progressive Collapse of Complex Structures.

DTIC Science & Technology

1982-12-01

tions of wing spar roots, although developed from experimental measure- ments, did not produce purely rigid body motions for reasons explained in...support structures in the same manner as the wings had been attached to aircraft fuselages. The support structures were extremely rigid compared to the...support structures and pinned into place within small tolerance; however, some motion of the wing spar roots with respect to the supports was

Deformable image registration for adaptive radiotherapy with guaranteed local rigidity constraints.

PubMed

König, Lars; Derksen, Alexander; Papenberg, Nils; Haas, Benjamin

2016-09-20

Deformable image registration (DIR) is a key component in many radiotherapy applications. However, often resulting deformations are not satisfying, since varying deformation properties of different anatomical regions are not considered. To improve the plausibility of DIR in adaptive radiotherapy in the male pelvic area, this work integrates a local rigidity deformation model into a DIR algorithm. A DIR framework is extended by constraints, enforcing locally rigid deformation behavior for arbitrary delineated structures. The approach restricts those structures to rigid deformations, while surrounding tissue is still allowed to deform elastically. The algorithm is tested on ten CT/CBCT male pelvis datasets with active rigidity constraints on bones and prostate and compared to the Varian SmartAdapt deformable registration (VSA) on delineations of bladder, prostate and bones. The approach with no rigid structures (REG0) obtains an average dice similarity coefficient (DSC) of 0.87 ± 0.06 and a Hausdorff-Distance (HD) of 8.74 ± 5.95 mm. The new approach with rigid bones (REG1) yields a DSC of 0.87 ± 0.07, HD 8.91 ± 5.89 mm. Rigid deformation of bones and prostate (REG2) obtains 0.87 ± 0.06, HD 8.73 ± 6.01 mm, while VSA yields a DSC of 0.86 ± 0.07, HD 10.22 ± 6.62 mm. No deformation grid foldings are observed for REG0 and REG1 in 7 of 10 cases; for REG2 in 8 of 10 cases, with no grid foldings in prostate, an average of 0.08 % in bladder (REG2: no foldings) and 0.01 % inside the body contour. VSA exhibits grid foldings in each case, with an average percentage of 1.81 % for prostate, 1.74 % for bladder and 0.12 % for the body contour. While REG1 and REG2 keep bones rigid, elastic bone deformations are observed with REG0 and VSA. An average runtime of 26.2 s was achieved with REG1; 31.1 s with REG2, compared to 10.5 s with REG0 and 10.7 s with VMS. With accuracy in the range of VSA, the new approach with constraints delivers physically more plausible deformations in the pelvic area with guaranteed rigidity of arbitrary structures. Although the algorithm uses an advanced deformation model, clinically feasible runtimes are achieved.

Reduction of stresses on buried rigid highway structures using the imperfect ditch method and expanded polysterene : geofoam.

DOT National Transportation Integrated Search

2009-01-01

This study provides strong evidences from both numerical model analysis and in-situ test data to indicate that geofoam is an ideal elasto-plastic material to reduce vertical load on top of rigid culvert resting on a rigid foundation. The load on the ...

Can deformation of a polymer film with a rigid coating model geophysical processes?

NASA Astrophysics Data System (ADS)

Volynskii, A. L.; Bazhenov, S. L.

2007-12-01

The structural and mechanical behavior of polymer films with a thin rigid coating is analyzed. The behavior of such systems under applied stress is accompanied by the formation of a regular wavy surface relief and by regular fragmentation of the coating. The above phenomena are shown to be universal. Both phenomena (stress-induced development of a regular wavy surface relief and regular fragmentation of the coating) are provided by the specific features of mechanical stress transfer from a compliant soft support to a rigid thin coating. The above phenomena are associated with a specific structure of the system, which is referred to as “a rigid coating on a soft substratum” system (RCSS). Surface microrelief in RCSS systems is similar to the ocean floor relief in the vicinity of mid-oceanic ridges. Thus, the complex system composed of a young oceanic crust and upper Earth's mantle may be considered as typically “a solid coating on a soft substratum” system. Specific features of the ocean floor relief are analyzed in terms of the approach advanced for the description of the structural mechanical behavior of polymer films with a rigid coating. This analysis allowed to estimate the strength of an ocean floor.

Dielectric elastomer bending tube actuators with rigid electrode structures

NASA Astrophysics Data System (ADS)

Wehrheim, F.; Schlaak, H. F.; Meyer, J.-U.

2010-04-01

The common approach for dielectric elastomer actuators (DEA) is based on the assumption that compliant electrodes are a fundamental design requirement. For tube-like applications compliant electrodes cause a change of the actuator diameter during actuation and would require additional support-structures. Focused on thinwalled actuator-tube geometries room consumption and radial stabilityr epresent crucial criteria. Following the ambition of maximum functional integration, the concept of using a rigid electrode structure arises. This structure realizes both, actuation and support characteristics. The intended rigid electrode structure is based on a stacked DEA with a non-compressible dielectric. Byactu ation, the displaced dielectric causes an overlap. This overlap serves as an indicator for geometrical limitations and has been used to extract design rules regarding the electrode size, electrode distance and maximum electrode travel. Bycons idering the strain in anydir ection, the mechanical efficiencyhas been used to define further design aspects. To verifyt he theoretic analysis, a test for determination of the compressive stress-strain-characteristics has been applied for different electrode setups. As result the geometrydep ending elastic pressure module has been formulated by implementation of a shape factor. The presented investigations consider exclusive the static behavior of a DEA-setup with rigid electrodes.

Flexibility Considerations on the Hydrodynamic Loading on a Vertical Wedge Drop

NASA Astrophysics Data System (ADS)

Ren, Zhongshu; Wang, Zhaoyuan; Judge, Carolyn; Stern, Fred; Ikeda, Christine

2017-11-01

High-speed craft operating at in waves frequently become airborne and slam into the water surface. This fluid-structure interaction problem is important to understand in order to increase the operating envelope of these craft. The goals of the current work are to investigate both the hydrodynamic loads and the resulting structural response on a planing hull. A V-shaped wedge is dropped vertically into calm water. The hydrodynamic pressure is measured using pressure sensors at discrete points on the hull. Two hulls are studied: one is rigid and one is flexible. Predictions of the hydrodynamic loading are made using Wagner's theory, Vorus's theory, and simulations in CFDShip Iowa. These predictions assume the structure is completely rigid. These predictions of the pressure coefficient match well with the rigid hull, as expected. The spray root is tracked in the rigid experimental set and compared with the theoretical and computational models. The pressure coefficient measured on the flexible hull shows discrepancies with the predictions due to the fluid-structure interaction. These discrepancies are quantified and interpreted in light of the structural flexibility. Funding for this work is from the Office of Naval Research Grant Number N00014-16-1-3188.

LTA structures and materials technology

NASA Technical Reports Server (NTRS)

Mayer, N. J.

1975-01-01

The state-of-the-art concerning structures and materials technology is reviewed. It is shown that many present materials developments resulting from balloon and aircraft research programs can be applied to new concepts in LTA vehicles. Both buoyant and semi-buoyant vehicles utilize similar approaches to solving structural problems and could involve pressurized non-rigid and unpressurized rigid structures. System designs common to both and vital to structural integrity include much of the past technology as well. Further research is needed in determination of structural loads, especially in future design concepts.

Finite Element Modeling of Deployment, and Foam Rigidization of Struts and Quarter Scale Shooting Star Experiment

NASA Technical Reports Server (NTRS)

Leigh, Larry, Jr.

2002-01-01

Inflated cylindrical struts constructed of kapton polyimide film and rigidized with foam have considerable practical application and potential for use as components of inflatable concentrator assemblies, antenna structures and space power systems, Because of their importance, it is of great interest to characterize the dynamic behavior of these components and structures both experimentally and analytically. It is very helpful to take a building-block approach to modeling and understanding inflatable assemblies by first investigating in detail the behavior of the components such as the struts. The foam material used for rigidization of such cylinders has varying modulus, which is a function of different factors, such as density of the foam. Thus, the primary motivation of the tests and analytical modeling efforts was to determine and understand the response of foam-rigidized cylinders for different densities, sizes, and construction methods, In recent years, inflatable structures have been the subject of renewed interest for space applications such as communications antennae, solar thermal propulsion, and space solar power. A major advantage of using inflatable structures in space is that they are extremely lightweight. This makes inflatables a perfect match for solar thermal propulsion because of the low thrust levels available. An obvious second advantage is on-orbit deployability and subsequent space savings in launch configuration. It can be seen that inflatable cylindrical struts and torus are critical components of structural assemblies. In view of this importance, structural dynamic and static behaviors of typical rigidized polyimide struts are investigated in this paper. The paper will focus on the finite element models that were used to model the behavior of the complete solar collector structure, and the results that they provided, as compared to test data.

The effects of rigid motions on elastic network model force constants

PubMed Central

Lezon, Timothy R.

2012-01-01

Elastic network models provide an efficient way to quickly calculate protein global dynamics from experimentally determined structures. The model’s single parameter, its force constant, determines the physical extent of equilibrium fluctuations. The values of force constants can be calculated by fitting to experimental data, but the results depend on the type of experimental data used. Here we investigate the differences between calculated values of force constants _t to data from NMR and X-ray structures. We find that X-ray B factors carry the signature of rigid-body motions, to the extent that B factors can be almost entirely accounted for by rigid motions alone. When fitting to more refined anisotropic temperature factors, the contributions of rigid motions are significantly reduced, indicating that the large contribution of rigid motions to B factors is a result of over-fitting. No correlation is found between force constants fit to NMR data and those fit to X-ray data, possibly due to the inability of NMR data to accurately capture protein dynamics. PMID:22228562

Extracting a Purely Non-rigid Deformation Field of a Single Structure

NASA Astrophysics Data System (ADS)

Demirci, Stefanie; Manstad-Hulaas, Frode; Navab, Nassir

During endovascular aortic repair (EVAR) treatment, the aortic shape is subject to severe deformation that is imposed by medical instruments such as guide wires, catheters, and the stent graft. The problem definition of deformable registration of images covering the entire abdominal region, however, is highly ill-posed. We present a new method for extracting the deformation of an aneurysmatic aorta. The outline of the procedure includes initial rigid alignment of two abdominal scans, segmentation of abdominal vessel trees, and automatic reduction of their centerline structures to one specified region of interest around the aorta. Our non-rigid registration procedure then only computes local non-rigid deformation and leaves out all remaining global rigid transformations. In order to evaluate our method, experiments for the extraction of aortic deformation fields are conducted on 15 patient datasets from endovascular aortic repair (EVAR) treatment. A visual assessment of the registration results were performed by two vascular surgeons and one interventional radiologist who are all experts in EVAR procedures.

Steady state solutions to dynamically loaded periodic structures

NASA Technical Reports Server (NTRS)

Kalinowski, A. J.

1980-01-01

The general problem of solving for the steady state (time domain) dynamic response (i.e., NASTRAN rigid format-8) of a general elastic periodic structure subject to a phase difference loading of the type encountered in traveling wave propagation problems was studied. Two types of structural configurations were considered; in the first type, the structure has a repeating pattern over a span that is long enough to be considered, for all practical purposes, as infinite; in the second type, the structure has structural rotational symmetry in the circumferential direction. The theory and a corresponding set of DMAP instructions which permits the NASTRAN user to automatically alter the rigid format-8 sequence to solve the intended class of problems are presented. Final results are recovered as with any ordinary rigid format-8 solution, except that the results are only printed for the typical periodic segment of the structure. A simple demonstration problem having a known exact solution is used to illustrate the implementation of the procedure.

The Effect of Structural Curvings on the Stress Distribution in a Rigidly Fixed Composite Plate under Forced Vibration

NASA Astrophysics Data System (ADS)

Zamanov, A. D.

2002-01-01

Based on the exact three-dimensional equations of continuum mechanics and the Akbarov-Guz' continuum theory, the problem on forced vibrations of a rectangular plate made of a composite material with a periodically curved structure is formulated. The plate is rigidly fixed along the Ox 1 axis. Using the semi-analytic method of finite elements, a numerical procedure is elaborated for investigating this problem. The numerical results on the effect of structural curvings on the stress distribution in the plate under forced vibrations are analyzed. It is shown that the disturbances of the stress σ22 in a hinge-supported plate are greater than in a rigidly fixed one. Also, it is found that the structural curvings considerably affect the stress distribution in plates both under static and dynamic loading.

Control-structure interaction/mirror motion compensation

NASA Technical Reports Server (NTRS)

Mclaren, Mark; Chu, Peter; Price, Xen

1992-01-01

Space Systems/Loral (formerly Ford Aerospace, Space Systems Division) has implemented a rigid-body Mirror Motion Compensation (MMC) scheme for the GOES-I/M spacecraft currently being built for NASA and NOAA. This has resulted in a factor of 15 reduction in pointing error due to rigid-body spacecraft motion induced by the periodic black-body calibration maneuvers required for the instruments. For GOES the spacecraft and the payload mirrors are considered as rigid bodies. The structural flexibility effects are small and are included in the total pointing budget as a separate item. This paper extends the MMC technique to include structural flexibility. For large multi-payload platforms, the structural flexibility effects can be more important in sensor pointing jitter as the result of payload motion. Sensitivity results are included to show the importance of the dynamic model fidelity.

Vision-based stress estimation model for steel frame structures with rigid links

NASA Astrophysics Data System (ADS)

Park, Hyo Seon; Park, Jun Su; Oh, Byung Kwan

2017-07-01

This paper presents a stress estimation model for the safety evaluation of steel frame structures with rigid links using a vision-based monitoring system. In this model, the deformed shape of a structure under external loads is estimated via displacements measured by a motion capture system (MCS), which is a non-contact displacement measurement device. During the estimation of the deformed shape, the effective lengths of the rigid link ranges in the frame structure are identified. The radius of the curvature of the structural member to be monitored is calculated using the estimated deformed shape and is employed to estimate stress. Using MCS in the presented model, the safety of a structure can be assessed gauge-freely. In addition, because the stress is directly extracted from the radius of the curvature obtained from the measured deformed shape, information on the loadings and boundary conditions of the structure are not required. Furthermore, the model, which includes the identification of the effective lengths of the rigid links, can consider the influences of the stiffness of the connection and support on the deformation in the stress estimation. To verify the applicability of the presented model, static loading tests for a steel frame specimen were conducted. By comparing the stress estimated by the model with the measured stress, the validity of the model was confirmed.

Non-rigid, but not rigid, motion interferes with the processing of structural face information in developmental prosopagnosia.

PubMed

Maguinness, Corrina; Newell, Fiona N

2015-04-01

There is growing evidence to suggest that facial motion is an important cue for face recognition. However, it is poorly understood whether motion is integrated with facial form information or whether it provides an independent cue to identity. To provide further insight into this issue, we compared the effect of motion on face perception in two developmental prosopagnosics and age-matched controls. Participants first learned faces presented dynamically (video), or in a sequence of static images, in which rigid (viewpoint) or non-rigid (expression) changes occurred. Immediately following learning, participants were required to match a static face image to the learned face. Test face images varied by viewpoint (Experiment 1) or expression (Experiment 2) and were learned or novel face images. We found similar performance across prosopagnosics and controls in matching facial identity across changes in viewpoint when the learned face was shown moving in a rigid manner. However, non-rigid motion interfered with face matching across changes in expression in both individuals with prosopagnosia compared to the performance of control participants. In contrast, non-rigid motion did not differentially affect the matching of facial expressions across changes in identity for either prosopagnosics (Experiment 3). Our results suggest that whilst the processing of rigid motion information of a face may be preserved in developmental prosopagnosia, non-rigid motion can specifically interfere with the representation of structural face information. Taken together, these results suggest that both form and motion cues are important in face perception and that these cues are likely integrated in the representation of facial identity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Active vibration control techniques for flexible space structures

NASA Technical Reports Server (NTRS)

Parlos, Alexander G.; Jayasuriya, Suhada

1990-01-01

Two proposed control system design techniques for active vibration control in flexible space structures are detailed. Control issues relevant only to flexible-body dynamics are addressed, whereas no attempt was made to integrate the flexible and rigid-body spacecraft dynamics. Both of the proposed approaches revealed encouraging results; however, further investigation of the interaction of the flexible and rigid-body dynamics is warranted.

A new pre-loaded beam geometric stiffness matrix with full rigid body capabilities

NASA Astrophysics Data System (ADS)

Bosela, P. A.; Fertis, D. G.; Shaker, F. J.

1992-09-01

Space structures, such as the Space Station solar arrays, must be extremely light-weight, flexible structures. Accurate prediction of the natural frequencies and mode shapes is essential for determining the structural adequacy of components, and designing a controls system. The tension pre-load in the 'blanket' of photovoltaic solar collectors, and the free/free boundary conditions of a structure in space, causes serious reservations on the use of standard finite element techniques of solution. In particular, a phenomenon known as 'grounding', or false stiffening, of the stiffness matrix occurs during rigid body rotation. The authors have previously shown that the grounding phenomenon is caused by a lack of rigid body rotational capability, and is typical in beam geometric stiffness matrices formulated by others, including those which contain higher order effects. The cause of the problem was identified as the force imbalance inherent in the formulations. In this paper, the authors develop a beam geometric stiffness matrix for a directed force problem, and show that the resultant global stiffness matrix contains complete rigid body mode capabilities, and performs very well in the diagonalization methodology customarily used in dynamic analysis.

Army Helicopter Crashworthiness

DTIC Science & Technology

1983-10-01

protect the structure surrounding the occupied Cabin volume. Components. An important part of this program was to evaluate analysis methods that could...rigid (nonstroking) seats and the production BLACK HAWK helicopter crashworthy crewseat. Tests of three embalmed cadavers in the rigid seat gave mixed...CONDITIONS FOR RIGID SEAT TESTS WITH EMBALMED CADAVERS 1 CADAVER WEIGHT PEAK TEST NO. NO. AGE HEIGHT (LB) SEX ACCEL. (G) FRACTURE CONDITION SERIES #1

Self-Deployable Membrane Structures

NASA Technical Reports Server (NTRS)

Sokolowski, Witold M.; Willis, Paul B.; Tan, Seng C.

2010-01-01

Currently existing approaches for deployment of large, ultra-lightweight gossamer structures in space rely typically upon electromechanical mechanisms and mechanically expandable or inflatable booms for deployment and to maintain them in a fully deployed, operational configuration. These support structures, with the associated deployment mechanisms, launch restraints, inflation systems, and controls, can comprise more than 90 percent of the total mass budget. In addition, they significantly increase the stowage volume, cost, and complexity. A CHEM (cold hibernated elastic memory) membrane structure without any deployable mechanism and support booms/structure is deployed by using shape memory and elastic recovery. The use of CHEM micro-foams reinforced with carbon nanotubes is considered for thin-membrane structure applications. In this advanced structural concept, the CHEM membrane structure is warmed up to allow packaging and stowing prior to launch, and then cooled to induce hibernation of the internal restoring forces. In space, the membrane remembers its original shape and size when warmed up. After the internal restoring forces deploy the structure, it is then cooled to achieve rigidization. For this type of structure, the solar radiation could be utilized as the heat energy used for deployment and space ambient temperature for rigidization. The overall simplicity of the CHEM self-deployable membrane is one of its greatest assets. In present approaches to space-deployable structures, the stow age and deployment are difficult and challenging, and introduce a significant risk, heavy mass, and high cost. Simple procedures provided by CHEM membrane greatly simplify the overall end-to-end process for designing, fabricating, deploying, and rigidizing large structures. The CHEM membrane avoids the complexities associated with other methods for deploying and rigidizing structures by eliminating deployable booms, deployment mechanisms, and inflation and control systems that can use up the majority of the mass budget

Method of assembling an electric power

DOEpatents

Rinehart, Lawrence E [Lake Oswego, OR; Romero, Guillermo L [Phoenix, AZ

2007-05-03

A method of assembling and providing an electric power apparatus. The method uses a heat resistant housing having a structure adapted to accommodate and retain a power circuit card and also including a bracket adapted to accommodate and constrain a rigid conductive member. A power circuit card having an electrical terminal is placed into the housing and a rigid conductive member into the bracket. The rigid conductive member is flow soldered to the electrical terminal, thereby exposing the heat resistant housing to heat and creating a solder bond. Finally, the rigid conductive member is affirmatively connected to the housing. The bracket constrains the rigid conductive member so that the act of affirmatively connecting does not weaken the solder bond.

Total absorption peak by use of a rigid frame porous layer backed by a rigid multi-irregularities grating.

PubMed

Groby, J-P; Lauriks, W; Vigran, T E

2010-05-01

The acoustic properties of a low resistivity porous layer backed by a rigid plate containing periodic rectangular irregularities, creating a multicomponent diffraction gratings, are investigated. Numerical and experimental results show that the structure possesses a total absorption peak at the frequency of the modified mode of the layer, when designed as proposed in the article. These results are explained by an analysis of the acoustic response of the whole structure and especially by the modal analysis of the configuration. When more than one irregularity per spatial period is considered, additional higher frequency peaks are observed.

A structural dynamics study of a wing-pylon-tiltrotor system

NASA Astrophysics Data System (ADS)

Khader, N.; Abu-Mallouh, R.

1992-12-01

A simple structural model for a three-bladed tiltrotor-pylon-wing assembly is presented, which accounts for chordwise, transverse, and torsional wing deformations, rigid pylon pitching motion with respect to the wing tip cross-section in its deformed position, lead-lag, flap, and torsional deformations of rotor blades. The model considers equivalent viscous damping associated with blade and wing elastic deformations and with rigid pylon pitching motion. It is established that blade-to wing bending rigidity ratio, pylon pitching frequency, equivalent viscous damping associated with blade elastic deformations, and rotational speed, are the most important design parameters, whose effect on system frequencies and stability boundaries is evaluated.

Hydrodynamics of a flexible plate between pitching rigid plates

NASA Astrophysics Data System (ADS)

Kim, Junyoung; Kim, Daegyoum

2017-11-01

The dynamics of a flexible plate have been studied as a model problem in swimming and flying of animals and fluid-structure interaction of plants and flags. Motivated by fish schooling and an array of sea grasses, we investigate the dynamics of a flexible plate closely placed between two pitching rigid plates. In most studies on passive deformation of the flexible plate, the plate is immersed in a uniform flow or a wavy flow. However, in this study, the flexible plate experiences periodic deformation by the oscillatory flow generated by the prescribed pitching motion of the rigid plates. In our model, the pitching axes of the rigid plates and the clamping position of the flexible plate are aligned on the same line. The flexible plate shows various responses depending on length and pitching frequency of rigid plates, thickness of a flexible plate, and free-stream velocity. To find the effect of each variable on the response of the flexible plate, amplitude of a trailing edge and modal contribution of a flapping motion are compared, and flow structure around the flexible plate is examined.

The effects of rigid motions on elastic network model force constants.

PubMed

Lezon, Timothy R

2012-04-01

Elastic network models provide an efficient way to quickly calculate protein global dynamics from experimentally determined structures. The model's single parameter, its force constant, determines the physical extent of equilibrium fluctuations. The values of force constants can be calculated by fitting to experimental data, but the results depend on the type of experimental data used. Here, we investigate the differences between calculated values of force constants and data from NMR and X-ray structures. We find that X-ray B factors carry the signature of rigid-body motions, to the extent that B factors can be almost entirely accounted for by rigid motions alone. When fitting to more refined anisotropic temperature factors, the contributions of rigid motions are significantly reduced, indicating that the large contribution of rigid motions to B factors is a result of over-fitting. No correlation is found between force constants fit to NMR data and those fit to X-ray data, possibly due to the inability of NMR data to accurately capture protein dynamics. Copyright © 2011 Wiley Periodicals, Inc.

Aspects concerning verification methods and rigidity increment of complex technological systems

NASA Astrophysics Data System (ADS)

Casian, M.

2016-11-01

Any technological process and technology aims a quality and precise product, something almost impossible without high rigidity machine tools, equipment and components. Therefore, from the design phase, it is very important to create structures and machines with high stiffness characteristics. At the same time, increasing the stiffness should not raise the material costs. Searching this midpoint between high rigidity and minimum expenses leads to investigations and checks in structural components through various methods and techniques and sometimes quite advanced methods. In order to highlight some aspects concerning the significance of the mechanical equipment rigidity, the finite element method and an analytical method based on the use Mathcad software were used, by taking into consideration a subassembly of a grinding machine. Graphical representations were elaborated, offering a more complete image about the stresses and deformations able to affect the considered mechanical subassembly.

Investigation of Liquid Sloshing in Spin-Stabilized Satellites.

DTIC Science & Technology

1993-01-31

deformation of the spinning structure in addition to the rigid body motion . A Lagrangian approach was used to develop the equations of motion which include...nonlinear relationships for the unknown rigid body motions and linear terms for the relatively small elastic deformations of the members. Appendix F...the rigid body motion of the test assembly. A pendulum analogy was used to model the sloshing liquid in that early program. Several numerical

A geometrically controlled rigidity transition in a model for confluent 3D tissues

NASA Astrophysics Data System (ADS)

Merkel, Matthias; Manning, M. Lisa

2018-02-01

The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Previously, a class of 2D cellular models has been shown to undergo a rigidity transition controlled by a mechanical parameter that specifies cell shapes. Here, we generalize this model to 3D and find a rigidity transition that is similarly controlled by the preferred surface area S 0: the model is solid-like below a dimensionless surface area of {s}0\\equiv {S}0/{\\bar{V}}2/3≈ 5.413 with \\bar{V} being the average cell volume, and fluid-like above this value. We demonstrate that, unlike jamming in soft spheres, residual stresses are necessary to create rigidity. These stresses occur precisely when cells are unable to obtain their desired geometry, and we conjecture that there is a well-defined minimal surface area possible for disordered cellular structures. We show that the behavior of this minimal surface induces a linear scaling of the shear modulus with the control parameter at the transition point, which is different from the scaling observed in particulate matter. The existence of such a minimal surface may be relevant for biological tissues and foams, and helps explain why cell shapes are a good structural order parameter for rigidity transitions in biological tissues.

Ocean Engineering Studies Compiled 1991. Volume 9. External Pressure Housing - Conrete

DTIC Science & Technology

1991-01-01

by inserts of different rigidities would thus be obtained. Table 1. Description of Concrete Sphere Models and Test...relationship between the insert’s rigidity and the strain increase in its vicinity. Planned investigation by NCEL employing photoelastic analysis of models of ... structural , in which only the load -carrying ability of the structure was checked. In the operational tests, the small-scale model habitat

Moving-Bank Multiple Model Adaptive Estimation and Control Applied to a Large Flexible Space Structure

DTIC Science & Technology

1990-12-01

was determined from the difference between the 24-state matrix product, HtP (t’)HT, and the six-state matrix product, HfPf (tT)HT’. For this...The true position for node 7, which represents the rigid body position of the structure, is not damped and can be interpreted as a rigid body...application, considering the same issues as explored in this research. Continue with a physical interpretation of the structure positions for determining the

IFACEwat: the interfacial water-implemented re-ranking algorithm to improve the discrimination of near native structures for protein rigid docking

PubMed Central

2014-01-01

Background Protein-protein docking is an in silico method to predict the formation of protein complexes. Due to limited computational resources, the protein-protein docking approach has been developed under the assumption of rigid docking, in which one of the two protein partners remains rigid during the protein associations and water contribution is ignored or implicitly presented. Despite obtaining a number of acceptable complex predictions, it seems to-date that most initial rigid docking algorithms still find it difficult or even fail to discriminate successfully the correct predictions from the other incorrect or false positive ones. To improve the rigid docking results, re-ranking is one of the effective methods that help re-locate the correct predictions in top high ranks, discriminating them from the other incorrect ones. In this paper, we propose a new re-ranking technique using a new energy-based scoring function, namely IFACEwat - a combined Interface Atomic Contact Energy (IFACE) and water effect. The IFACEwat aims to further improve the discrimination of the near-native structures of the initial rigid docking algorithm ZDOCK3.0.2. Unlike other re-ranking techniques, the IFACEwat explicitly implements interfacial water into the protein interfaces to account for the water-mediated contacts during the protein interactions. Results Our results showed that the IFACEwat increased both the numbers of the near-native structures and improved their ranks as compared to the initial rigid docking ZDOCK3.0.2. In fact, the IFACEwat achieved a success rate of 83.8% for Antigen/Antibody complexes, which is 10% better than ZDOCK3.0.2. As compared to another re-ranking technique ZRANK, the IFACEwat obtains success rates of 92.3% (8% better) and 90% (5% better) respectively for medium and difficult cases. When comparing with the latest published re-ranking method F2Dock, the IFACEwat performed equivalently well or even better for several Antigen/Antibody complexes. Conclusions With the inclusion of interfacial water, the IFACEwat improves mostly results of the initial rigid docking, especially for Antigen/Antibody complexes. The improvement is achieved by explicitly taking into account the contribution of water during the protein interactions, which was ignored or not fully presented by the initial rigid docking and other re-ranking techniques. In addition, the IFACEwat maintains sufficient computational efficiency of the initial docking algorithm, yet improves the ranks as well as the number of the near native structures found. As our implementation so far targeted to improve the results of ZDOCK3.0.2, and particularly for the Antigen/Antibody complexes, it is expected in the near future that more implementations will be conducted to be applicable for other initial rigid docking algorithms. PMID:25521441

Associative memory through rigid origami

NASA Astrophysics Data System (ADS)

Murugan, Arvind; Brenner, Michael

2015-03-01

Mechanisms such as Miura Ori have proven useful in diverse contexts since they have only one degree of freedom that is easily controlled. We combine the theory of rigid origami and associative memory in frustrated neural networks to create structures that can ``learn'' multiple generic folding mechanisms and yet can be robustly controlled. We show that such rigid origami structures can ``recall'' a specific learned mechanism when induced by a physical impulse that only need resemble the desired mechanism (i.e. robust recall through association). Such associative memory in matter, seen before in self-assembly, arises due to a balance between local promiscuity (i.e., many local degrees of freedom) and global frustration which minimizes interference between different learned behaviors. Origami with associative memory can lead to a new class of deployable structures and kinetic architectures with multiple context-dependent behaviors.

A novel colorimetric fluoride sensor based on a semi-rigid chromophore controlled by hydrogen bonding.

PubMed

Li, Jiling; Xu, Xiaoyong; Shao, Xusheng; Li, Zhong

2015-12-01

A novel semi-rigid latent chromophore E1, containing an amide subunit activated by an adjacent semi-rigid intramolecular hydrogen-bonding (IHB) unit, was designed for the detection of fluoride ion by the 'naked-eye' in CH3CN. Comparative studies on structural analogs (E2, E3, and E4) provided significant insight into the structural and functional role of the amide N-H and IHB segment in the selective recognition of fluoride ions. The deprotonation of the amide N-H followed by the enhancement of intramolecular charge transfer (ICT) induced the colorimetric detection of E1 for fluoride ion. Copyright © 2015 John Wiley & Sons, Ltd.

Hierarchical Structure in Polymeric Solids and Its Influence on Properties

DTIC Science & Technology

1989-05-01

consequences for the systematic design of phase behaviour. Also it is one of the several illustrations that the ’rigid’ group in itself need not...identified the factors controlling mesogen (or in general, rigid group ) packing in segmented LCP forming polymers and its influence on layer formation at...molecules in solution and controlled preparation of model systems" in Rigid Rod Polymers, Materials Research Publication, Ed. W. Adams, in the press

Performance determination of precast concrete slabs used for the repair of rigid pavements.

DOT National Transportation Integrated Search

2014-10-01

The safety of civilians is of paramount importance during the construction and repair of concrete pavements. : A complete understanding of the pavement distresses that compromise the structural stability and performance : of rigid pavements are requi...

Ultrafast and Wide Range Analysis of DNA Molecules Using Rigid Network Structure of Solid Nanowires

PubMed Central

Rahong, Sakon; Yasui, Takao; Yanagida, Takeshi; Nagashima, Kazuki; Kanai, Masaki; Klamchuen, Annop; Meng, Gang; He, Yong; Zhuge, Fuwei; Kaji, Noritada; Kawai, Tomoji; Baba, Yoshinobu

2014-01-01

Analyzing sizes of DNA via electrophoresis using a gel has played an important role in the recent, rapid progress of biology and biotechnology. Although analyzing DNA over a wide range of sizes in a short time is desired, no existing electrophoresis methods have been able to fully satisfy these two requirements. Here we propose a novel method using a rigid 3D network structure composed of solid nanowires within a microchannel. This rigid network structure enables analysis of DNA under applied DC electric fields for a large DNA size range (100 bp–166 kbp) within 13 s, which are much wider and faster conditions than those of any existing methods. The network density is readily varied for the targeted DNA size range by tailoring the number of cycles of the nanowire growth only at the desired spatial position within the microchannel. The rigid dense 3D network structure with spatial density control plays an important role in determining the capability for analyzing DNA. Since the present method allows the spatial location and density of the nanostructure within the microchannels to be defined, this unique controllability offers a new strategy to develop an analytical method not only for DNA but also for other biological molecules. PMID:24918865

Ultrafast and Wide Range Analysis of DNA Molecules Using Rigid Network Structure of Solid Nanowires

NASA Astrophysics Data System (ADS)

Rahong, Sakon; Yasui, Takao; Yanagida, Takeshi; Nagashima, Kazuki; Kanai, Masaki; Klamchuen, Annop; Meng, Gang; He, Yong; Zhuge, Fuwei; Kaji, Noritada; Kawai, Tomoji; Baba, Yoshinobu

2014-06-01

Analyzing sizes of DNA via electrophoresis using a gel has played an important role in the recent, rapid progress of biology and biotechnology. Although analyzing DNA over a wide range of sizes in a short time is desired, no existing electrophoresis methods have been able to fully satisfy these two requirements. Here we propose a novel method using a rigid 3D network structure composed of solid nanowires within a microchannel. This rigid network structure enables analysis of DNA under applied DC electric fields for a large DNA size range (100 bp-166 kbp) within 13 s, which are much wider and faster conditions than those of any existing methods. The network density is readily varied for the targeted DNA size range by tailoring the number of cycles of the nanowire growth only at the desired spatial position within the microchannel. The rigid dense 3D network structure with spatial density control plays an important role in determining the capability for analyzing DNA. Since the present method allows the spatial location and density of the nanostructure within the microchannels to be defined, this unique controllability offers a new strategy to develop an analytical method not only for DNA but also for other biological molecules.

Verification of the Seismic Performance of a Rigidly Connected Modular System Depending on the Shape and Size of the Ceiling Bracket.

PubMed

Lee, Seungjae; Park, Jaeseong; Kwak, Euishin; Shon, Sudeok; Kang, Changhoon; Choi, Hosoon

2017-03-06

Modular systems have been mostly researched in relatively low-rise structures but, lately, their applications to mid- to high-rise structures began to be reviewed, and research interest in new modularization subjects has increased. The application of modular systems to mid- to high-rise structures requires the structural stability of the frame and connections that consist of units, and the evaluation of the stiffness of structures that are combined in units. However, the combination of general units causes loss of the cross-section of columns or beams, resulting in low seismic performance and hindering installation works in the field. In addition, the evaluation of a frame considering such a cross-sectional loss is not easy. Therefore, it is necessary to develop a joint that is stable and easy to install. In the study, a rigidly connected modular system was proposed as a moment-resisting frame for a unit modular system, and their joints were developed and their performances were compared. The proposed system changed the ceiling beam into a bracket type to fasten bolts. It can be merged with other seismic force-resisting systems. To verify the seismic performance of the proposed system, a cyclic loading test was conducted, and the rigidly connected joint performance and integrated behavior at the joint of modular units were investigated. From the experimental results, the maximum resisting force of the proposed connection exceeded the theoretical parameters, indicating that a rigid joint structural performance could be secured.

Polydopamine Inter-Fiber Networks: New Strategy for Producing Rigid, Sticky, 3D Fluffy Electrospun Fibrous Polycaprolactone Sponges.

PubMed

Choi, Wuyong; Lee, Slgirim; Kim, Seung-Hyun; Jang, Jae-Hyung

2016-06-01

Designing versatile 3D interfaces that can precisely represent a biological environment is a prerequisite for the creation of artificial tissue structures. To this end, electrospun fibrous sponges, precisely mimicking an extracellular matrix and providing highly porous interfaces, have capabilities that can function as versatile physical cues to regenerate various tissues. However, their intrinsic features, such as sheet-like, thin, and weak structures, limit the design of a number of uses in tissue engineering applications. Herein, a highly facile methodology capable of fabricating rigid, sticky, spatially expanded fluffy electrospun fibrous sponges is proposed. A bio-inspired adhesive material, poly(dopamine) (pDA), is employed as a key mediator to provide rigidity and stickiness to the 3D poly(ε-caprolactone) (PCL) fibrous sponges, which are fabricated using a coaxial electrospinning with polystyrene followed by a selective leaching process. The iron ion induced oxidation of dopamine into pDA networks interwoven with PCL fibers results in significant increases in the rigidity of 3D fibrous sponges. Furthermore, the exposure of catecholamine groups on the fiber surfaces promotes the stable attachment of the sponges on wet organ surfaces and triggers the robust immobilization of biomolecules (e.g., proteins and gene vectors), demonstrating their potential for 3D scaffolds as well as drug delivery vehicles. Because fibrous structures are ubiquitous in the human body, these rigid, sticky, 3D fibrous sponges are good candidates for powerful biomaterial systems that functionally mimic a variety of tissue structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

IFACEwat: the interfacial water-implemented re-ranking algorithm to improve the discrimination of near native structures for protein rigid docking.

PubMed

Su, Chinh; Nguyen, Thuy-Diem; Zheng, Jie; Kwoh, Chee-Keong

2014-01-01

Protein-protein docking is an in silico method to predict the formation of protein complexes. Due to limited computational resources, the protein-protein docking approach has been developed under the assumption of rigid docking, in which one of the two protein partners remains rigid during the protein associations and water contribution is ignored or implicitly presented. Despite obtaining a number of acceptable complex predictions, it seems to-date that most initial rigid docking algorithms still find it difficult or even fail to discriminate successfully the correct predictions from the other incorrect or false positive ones. To improve the rigid docking results, re-ranking is one of the effective methods that help re-locate the correct predictions in top high ranks, discriminating them from the other incorrect ones. Our results showed that the IFACEwat increased both the numbers of the near-native structures and improved their ranks as compared to the initial rigid docking ZDOCK3.0.2. In fact, the IFACEwat achieved a success rate of 83.8% for Antigen/Antibody complexes, which is 10% better than ZDOCK3.0.2. As compared to another re-ranking technique ZRANK, the IFACEwat obtains success rates of 92.3% (8% better) and 90% (5% better) respectively for medium and difficult cases. When comparing with the latest published re-ranking method F2Dock, the IFACEwat performed equivalently well or even better for several Antigen/Antibody complexes. With the inclusion of interfacial water, the IFACEwat improves mostly results of the initial rigid docking, especially for Antigen/Antibody complexes. The improvement is achieved by explicitly taking into account the contribution of water during the protein interactions, which was ignored or not fully presented by the initial rigid docking and other re-ranking techniques. In addition, the IFACEwat maintains sufficient computational efficiency of the initial docking algorithm, yet improves the ranks as well as the number of the near native structures found. As our implementation so far targeted to improve the results of ZDOCK3.0.2, and particularly for the Antigen/Antibody complexes, it is expected in the near future that more implementations will be conducted to be applicable for other initial rigid docking algorithms.

How the morphology of dusts influences packing density in small solar system bodies

NASA Astrophysics Data System (ADS)

Zangmeister, C.; Radney, J. G.; Zachariah, M. R.

2014-12-01

Large planetary seedlings, comets, and nanoscale soot particles are made from rigid, aggregated subunits that are compacted under low compression into larger structures spanning over 10 orders of magnitude in dimensional space. Here, we demonstrate that the packing density (Φf) of compacted rigid aggregates is independent of spatial scale for systems under weak compaction, a regime that includes small solar system bodies. The Φf of rigid aggregated structures across 6 orders of magnitude were measured using nanoscale spherical soot aerosol composed of aggregates with ≈ 17 nm monomeric subunits and aggregates made from uniform monomeric 6 mm spherical subunits at the macroscale. We find Φf = 0.36 ± 0.02 at both the nano- and macroscale. These values are remarkably similar to qf observed for comet nuclei and measured values of other rigid aggregated systems across a wide variety of spatial and formative conditions. We present a packing model that incorporates the aggregate morphology and show that Φf is independent of both monomer and aggregate size. These observations suggest thatqf of rigid aggregates is independent of spatial dimension across varied formative conditions ranging from interstellar space to pharmaceutical manufacturing.

Structural rigidity in the capsid assembly of cowpea chlorotic mottle virus

NASA Astrophysics Data System (ADS)

Hespenheide, B. M.; Jacobs, D. J.; Thorpe, M. F.

2004-11-01

The cowpea chlorotic mottle virus (CCMV) has a protein cage, or capsid, which encloses its genetic material. The structure of the capsid consists of 180 copies of a single protein that self-assemble inside a cell to form a complete capsid with icosahedral symmetry. The icosahedral surface can be naturally divided into pentagonal and hexagonal faces, and the formation of either of these faces has been proposed to be the first step in the capsid assembly process. We have used the software FIRST to analyse the rigidity of pentameric and hexameric substructures of the complete capsid to explore the viability of certain capsid assembly pathways. FIRST uses the 3D pebble game to determine structural rigidity, and a brief description of this algorithm, as applied to body-bar networks, is given here. We find that the pentameric substructure, which corresponds to a pentagonal face on the icosahedral surface, provides the best structural properties for nucleating the capsid assembly process, consistent with experimental observations.

Reflections on the mechanical structure of the base of the skull and on the face. Part 1: Classical theories, observed structures.

PubMed

Ferré, J C; Chevalier, C; Robert, R; Degrez, J; Le Cloarec, A Y; Legoux, R; Orio, E; Barbin, J Y

1989-01-01

Using thick sections of the base of the skull and face their mechanical structure is viewed from the engineering aspect and the anatomic solutions evolved are compared with those selected by Aerospatiale engineers for the concept and development of the Airbus. It is concluded that the anterior and middle cranial fossae, together with the face, constitute an inseparable mechanical assembly each of whose component units participate in the rigidity of the others. Since this mechanical assembly must provide maximal rigidity for minimal weight, this suggests that aeronautical solutions should throw much light on the detail of construction of the skull and face. Indeed, the rigidity and lightness of the latter are obtained by means of solutions familiar in aeronautics: the reliance on thin-shelled beams with a honeycomb filling, the diploe analogous to a preconstrained composite or sandwich structure, a system of frames, struts and stiffeners, and the use of fillets at the sites of junction of struts.

Development of a model of space station solar array

NASA Technical Reports Server (NTRS)

Bosela, Paul A.

1990-01-01

Space structures, such as the space station solar arrays, must be extremely lightweight, flexible structures. Accurate prediction of the natural frequencies and mode shapes is essential for determining the structural adequacy of components, and designing a control system. The tension preload in the blanket of photovoltaic solar collectors, and the free/free boundary conditions of a structure in space, causes serious reservations on the use of standard finite element techniques of solution. In particular, a phenomena known as grounding, or false stiffening, of the stiffness matrix occurs during rigid body rotation. The grounding phenomena is examined in detail. Numerous stiffness matrices developed by others are examined for rigid body rotation capability, and found lacking. Various techniques are used for developing new stiffness matrices from the rigorous solutions of the differential equations, including the solution of the directed force problem. A new directed force stiffness matrix developed by the author provides all the rigid body capabilities for the beam in space.

Estimation of payload loads using rigid body interface accelerations. [in structural design of launch vehicle systems

NASA Technical Reports Server (NTRS)

Chen, J. C.; Garba, J. A.; Wada, B. K.

1978-01-01

In the design/analysis process of a payload structural system, the accelerations at the payload/launch vehicle interface obtained from a system analysis using a rigid payload are often used as the input forcing function to the elastic payload to obtain structural design loads. Such an analysis is at best an approximation since the elastic coupling effects are neglected. This paper develops a method wherein the launch vehicle/rigid payload interface accelerations are modified to account for the payload elasticity. The advantage of the proposed method, which is exact to the extent that the physical system can be described by a truncated set of generalized coordinates, is that the complete design/analysis process can be performed within the organization responsible for the payload design. The method requires the updating of the system normal modes to account for payload changes, but does not require a complete transient solution using the composite system model. An application to a real complex structure, the Viking Spacecraft System, is given.

A rigid and thermally stable all ceramic optical support bench assembly for the LSST Camera

NASA Astrophysics Data System (ADS)

Kroedel, Matthias; Langton, J. Brian; Wahl, Bill

2017-09-01

This paper will present the ceramic design, fabrication and metrology results and assembly plan of the LSST camera optical bench structure which is using the unique manufacturing features of the HB-Cesic technology. The optical bench assembly consists of a rigid "Grid" fabrication supporting individual raft plates mounting sensor assemblies by way of a rigid kinematic support system to meet extreme stringent requirements for focal plane planarity and stability.

Mechanical Properties for the Grasp of a Robotic Hand

DTIC Science & Technology

1984-09-01

qf. The object is treated as a rigid body and consequently, a small motion , db, of the object in the (x.yz) system produces a displacement of the...several fingers, Asada addresses the problem of choosing a suitable finger configuration, He treats the held object as a rigid body and models the...modcled as elastic structures and the object as a rigid body . This is usually a good approximation for robots assembling parts or holding tools since

Control of large space structures

NASA Technical Reports Server (NTRS)

Gran, R.; Rossi, M.; Moyer, H. G.; Austin, F.

1979-01-01

The control of large space structures was studied to determine what, if any, limitations are imposed on the size of spacecraft which may be controlled using current control system design technology. Using a typical structure in the 35 to 70 meter size category, a control system design that used actuators that are currently available was designed. The amount of control power required to maintain the vehicle in a stabilized gravity gradient pointing orientation that also damped various structural motions was determined. The moment of inertia and mass properties of this structure were varied to verify that stability and performance were maintained. The study concludes that the structure's size is required to change by at least a factor of two before any stability problems arise. The stability margin that is lost is due to the scaling of the gravity gradient torques (the rigid body control) and as such can easily be corrected by changing the control gains associated with the rigid body control. A secondary conclusion from the study is that the control design that accommodates the structural motions (to damp them) is a little more sensitive than the design that works on attitude control of the rigid body only.

Flexibility and rigidity of cross-linked Straight Fibrils under axial motion constraints.

PubMed

Nagy Kem, Gyula

2016-09-01

The Straight Fibrils are stiff rod-like filaments and play a significant role in cellular processes as structural stability and intracellular transport. Introducing a 3D mechanical model for the motion of braced cylindrical fibrils under axial motion constraint; we provide some mechanism and a graph theoretical model for fibril structures and give the characterization of the flexibility and the rigidity of this bar-and-joint spatial framework. The connectedness and the circuit of the bracing graph characterize the flexibility of these structures. In this paper, we focus on the kinematical properties of hierarchical levels of fibrils and evaluate the number of the bracing elements for the rigidity and its computational complexity. The presented model is a good characterization of the frameworks of bio-fibrils such as microtubules, cellulose, which inspired this work. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural modulation and luminescent properties of four Cd{sup II} coordination architectures based on 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole and flexible/rigid dicarboxylate ligands

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

Xia, Liang; Dong, Wen-Wen, E-mail: dongww1@126.com; Ye, Xiao

To systematically investigate the influence of the flexible or rigid auxiliary ligands on the structures and properties of transition metal compounds, we synthesized four new d{sup 10} coordination polymers (CPs) from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) and flexible/rigid dicarboxylate ligands, [Cd(4-pzpt){sub 2}]{sub n} (1), [Cd{sub 3}(4-pzpt){sub 2}(suc){sub 2}]{sub n} (2), [Cd{sub 2}(4-Hpzpt)(nbc){sub 2}(H{sub 2}O)]{sub n} (3) and ([Cd{sub 2}(4-pzpt){sub 2}(tfbdc)(H{sub 2}O){sub 4}]·H{sub 2}O){sub n} (4) (H{sub 2}suc=1,2-ethanedicarboxylic acid, H{sub 2}nbc=hthalene-1,4-dicarboxylic acid, H{sub 2}tfbdc =2,3,5,6-tetrafluoroterephthalic acid). Single crystal X-ray analysis indicates that compound 1 shows a 4{sup 4}-sql layer, which is extended to a 3D network via nonclassical C–H{sup …}N hydrogen bonds. Compound 2more » possesses a 6-connected pcu-4{sup 12}0.6{sup 3} net composed of trinuclear Cd{sup II}-clusters. Compound 3 represents a rare 3D (3,4,4,5)-connected topology with a Schläfli symbol of (4·6·7)(4·5{sup 3}·7{sup 2})(5{sup 3}·6·7·9)(4{sup 2}·5{sup 5}·6·7{sup 2}). Compound 4 exhibits a 2D+2D→2D parallel interpenetrated 6{sup 3}-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting 3D supramolecular architecture through classical O–H{sup …}N and O–H{sup …}O hydrogen bonds. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. Moreover, the luminescent properties of them have been briefly investigated. - Graphical abstract: Four new Cd{sup II} coordination architectures constructed from the primary ligand 4-Hpzpt and flexible/rigid dicarboxylate coligands. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. And more, the thermal stability and luminescence are discussed. - Highlights: • Four new Cd{sup II} compounds with 4-Hpzpt and flexible/rigid dicarboxylate coligands. • Structural analysis of all compounds. • luminescent property of all compounds.« less

Stiffness-generated rigid-body mode shapes for Lanczos eigensolution with SUPORT DOF by way of a MSC/NASTRAN DMAP alter

NASA Technical Reports Server (NTRS)

Abdallah, Ayman A.; Barnett, Alan R.; Widrick, Timothy W.; Manella, Richard T.; Miller, Robert P.

1994-01-01

When using all MSC/NASTRAN eigensolution methods except Lanczos, the analyst can replace the coupled system rigid-body modes calculated within DMAP module READ with mass orthogonalized and normalized rigid-body modes generated from the system stiffness. This option is invoked by defining MSC/NASTRAN r-set degrees of freedom via the SUPORT bulk data card. The newly calculated modes are required if the rigid-body modes calculated by the eigensolver are not 'clean' due to numerical roundoffs in the solution. When performing transient structural dynamic load analysis, the numerical roundoffs can result in inaccurate rigid-body accelerations which affect steady-state responses. Unfortunately, when using the Lanczos method and defining r-set degrees of freedom, the rigid-body modes calculated within DMAP module REIGL are retained. To overcome this limitation and to allow MSC/NASTRAN to handle SUPORT degrees of freedom identically for all eigensolvers, a DMAP Alter has been written which replaces Lanczos-calculated rigid-body modes with stiffness-generated rigid-body modes. The newly generated rigid-body modes are normalized with respect to the system mass and orthogonalized using the Gram-Schmidt technique. This algorithm has been implemented as an enhancement to an existing coupled loads methodology.

Duration of bubble rearrangements in a coarsening foam probed by time-resolved diffusing-wave spectroscopy: Impact of interfacial rigidity

NASA Astrophysics Data System (ADS)

Le Merrer, Marie; Cohen-Addad, Sylvie; Höhler, Reinhard

2013-08-01

In aqueous foams, the diffusive gas transfer among neighboring bubbles drives a coarsening process which is accompanied by intermittent rearrangements of the structure. Using time-resolved diffusing-wave spectroscopy, we probe the dynamics of these events as a function of the rigidity of the gas-liquid interfaces, liquid viscosity, bubble size, and confinement pressure. We present in detail two independent techniques for analyzing the light scattering data, from which we extract the rearrangement duration. Our results show that interfacial rheology has a major impact on this duration. In the case of low interfacial rigidity, the rearrangements strongly slow down as the pressure is decreased close to the value zero where the bubble packing unjams. In contrast, if the interfaces are rigid, rearrangement durations are independent of the confinement pressure in the same investigated range. Using scaling arguments, we discuss dissipation mechanisms that may explain the observed dependency of the rearrangement dynamics on foam structure, pressure, and physicochemical solution properties.

Large Angle Transient Dynamics (LATDYN) user's manual

NASA Technical Reports Server (NTRS)

Abrahamson, A. Louis; Chang, Che-Wei; Powell, Michael G.; Wu, Shih-Chin; Bingel, Bradford D.; Theophilos, Paula M.

1991-01-01

A computer code for modeling the large angle transient dynamics (LATDYN) of structures was developed to investigate techniques for analyzing flexible deformation and control/structure interaction problems associated with large angular motions of spacecraft. This type of analysis is beyond the routine capability of conventional analytical tools without simplifying assumptions. In some instances, the motion may be sufficiently slow and the spacecraft (or component) sufficiently rigid to simplify analyses of dynamics and controls by making pseudo-static and/or rigid body assumptions. The LATDYN introduces a new approach to the problem by combining finite element structural analysis, multi-body dynamics, and control system analysis in a single tool. It includes a type of finite element that can deform and rotate through large angles at the same time, and which can be connected to other finite elements either rigidly or through mechanical joints. The LATDYN also provides symbolic capabilities for modeling control systems which are interfaced directly with the finite element structural model. Thus, the nonlinear equations representing the structural model are integrated along with the equations representing sensors, processing, and controls as a coupled system.

Stresses in Circular Plates with Rigid Elements

NASA Astrophysics Data System (ADS)

Velikanov, N. L.; Koryagin, S. I.; Sharkov, O. V.

2018-05-01

Calculations of residual stress fields are carried out by numerical and static methods, using the flat cross-section hypothesis. The failure of metal when exposed to residual stresses is, in most cases, brittle. The presence in the engineering structures of rigid elements often leads to the crack initiation and structure failure. This is due to the fact that rigid elements under the influence of external stresses are stress concentrators. In addition, if these elements are fixed by welding, the residual welding stresses can lead to an increase in stress concentration and, ultimately, to failure. The development of design schemes for such structures is a very urgent task for complex technical systems. To determine the stresses in a circular plate with a welded circular rigid insert under the influence of an external load, one can use the solution of the plane stress problem for annular plates in polar coordinates. The polar coordinates of the points are the polar radius and the polar angle, and the stress state is determined by normal radial stresses, tangential and shearing stresses. The use of the above mentioned design schemes, formulas, will allow more accurate determination of residual stresses in annular welded structures. This will help to establish the most likely directions of failure and take measures at the stages of designing, manufacturing and repairing engineering structures to prevent these failures. However, it must be taken into account that the external load, the presence of insulation can lead to a change in the residual stress field.

Control of Low Reynolds Number Flows with Fluid Structure Interactions

DTIC Science & Technology

2014-02-02

remote sensing and mineral exploration. MAVs have similar dimensions to birds and insects, and similar Reynolds numbers. Mini Unmanned Air Vehicles...that we are interested in are very different from biologically inspired flows, we note that the flexibility of the wings in insects and birds has...the rigid wing can be taken as: λ = 639.7. For sAR = 1.5, one rigid (t = 1.5 mm) and four flexible (t = 1 mm) wings are considered. The rigid wind

Verification of the Seismic Performance of a Rigidly Connected Modular System Depending on the Shape and Size of the Ceiling Bracket

PubMed Central

Lee, Seungjae; Park, Jaeseong; Kwak, Euishin; Shon, Sudeok; Kang, Changhoon; Choi, Hosoon

2017-01-01

Modular systems have been mostly researched in relatively low-rise structures but, lately, their applications to mid- to high-rise structures began to be reviewed, and research interest in new modularization subjects has increased. The application of modular systems to mid- to high-rise structures requires the structural stability of the frame and connections that consist of units, and the evaluation of the stiffness of structures that are combined in units. However, the combination of general units causes loss of the cross-section of columns or beams, resulting in low seismic performance and hindering installation works in the field. In addition, the evaluation of a frame considering such a cross-sectional loss is not easy. Therefore, it is necessary to develop a joint that is stable and easy to install. In the study, a rigidly connected modular system was proposed as a moment-resisting frame for a unit modular system, and their joints were developed and their performances were compared. The proposed system changed the ceiling beam into a bracket type to fasten bolts. It can be merged with other seismic force-resisting systems. To verify the seismic performance of the proposed system, a cyclic loading test was conducted, and the rigidly connected joint performance and integrated behavior at the joint of modular units were investigated. From the experimental results, the maximum resisting force of the proposed connection exceeded the theoretical parameters, indicating that a rigid joint structural performance could be secured. PMID:28772622

A combinatorial approach to protein docking with flexible side chains.

PubMed

Althaus, Ernst; Kohlbacher, Oliver; Lenhof, Hans-Peter; Müller, Peter

2002-01-01

Rigid-body docking approaches are not sufficient to predict the structure of a protein complex from the unbound (native) structures of the two proteins. Accounting for side chain flexibility is an important step towards fully flexible protein docking. This work describes an approach that allows conformational flexibility for the side chains while keeping the protein backbone rigid. Starting from candidates created by a rigid-docking algorithm, we demangle the side chains of the docking site, thus creating reasonable approximations of the true complex structure. These structures are ranked with respect to the binding free energy. We present two new techniques for side chain demangling. Both approaches are based on a discrete representation of the side chain conformational space by the use of a rotamer library. This leads to a combinatorial optimization problem. For the solution of this problem, we propose a fast heuristic approach and an exact, albeit slower, method that uses branch-and-cut techniques. As a test set, we use the unbound structures of three proteases and the corresponding protein inhibitors. For each of the examples, the highest-ranking conformation produced was a good approximation of the true complex structure.

Considerations for the application of finite element beam modeling to vibration analysis of flight vehicle structures. Ph.D. Thesis - Case Western Reserve Univ.

NASA Technical Reports Server (NTRS)

Kvaternik, R. G.

1976-01-01

The manner of representing a flight vehicle structure as an assembly of beam, spring, and rigid-body components for vibration analysis is described. The development is couched in terms of a substructures methodology which is based on the finite-element stiffness method. The particular manner of employing beam, spring, and rigid-body components to model such items as wing structures, external stores, pylons supporting engines or external stores, and sprung masses associated with launch vehicle fuel slosh is described by means of several simple qualitative examples. A detailed numerical example consisting of a tilt-rotor VTOL aircraft is included to provide a unified illustration of the procedure for representing a structure as an equivalent system of beams, springs, and rigid bodies, the manner of forming the substructure mass and stiffness matrices, and the mechanics of writing the equations of constraint which enforce deflection compatibility at the junctions of the substructures. Since many structures, or selected components of structures, can be represented in this manner for vibration analysis, the modeling concepts described and their application in the numerical example shown should prove generally useful to the dynamicist.

Competition between crystallization and vitrification of the rigid amorphous fraction in poly(3-hydroxybutyrate)

NASA Astrophysics Data System (ADS)

Di Lorenzo, Maria Laura; Righetti, Maria Cristina; Gazzano, Massimo

2012-07-01

Semicrystalline polymers have a metastable nanophase structure, where the various nanophases can be crystal, liquid, glass, or mesophase. This multi-level structure is determined by a competition among self-organization, crystallization, and vitrification of the amorphous segments and is established during material processing. The kinetics of such competition is here determined for poly(3-hydroxybutyrate) (PHB), as vitrification/devitrification of the rigid amorphous fraction strongly affects crystallization kinetics of PHB.

Effect of Ion Rigidity on Physical Properties of Ionic Liquids Studied by Molecular Dynamics Simulation.

PubMed

Ramírez-González, Pedro E; Ren, Gan; Saielli, Giacomo; Wang, Yanting

2016-06-30

In this work, we have performed molecular dynamics (MD) simulations to compare the structural and dynamical properties of three ionic liquids (ILs), 1-ethyl-3-methyl-imidazolium tetrafluorborate ([EMI(+)][BF4(-)]), 1,1'-dimethyl-4,4'-bipyridinium bis(tetrafluorborate) ([VIO(2+)][BF4(-)]2), and 1,1'-dimethyl-4,4'-bipyridinium bis(trifluoromethylsulfonyl)imide (bistriflimide in short) ([VIO(2+)][Tf2N(-)]2), aiming to discover the influence of ion rigidity on the physical properties of ILs. [VIO(2+)] is more rigid than [EMI(+)], and [BF4(-)] is more rigid than [Tf2N(-)]. [VIO(2+)][BF4(-)]2 has an anion distribution different from the other two by the higher and sharper peaks in the cation-anion radial distribution functions, reflecting a close-packed local structure of anions around cations. [VIO(2+)][BF4(-)]2 and [VIO(2+)][Tf2N(-)]2 have similar dynamics much slower than [EMI(+)][BF4(-)], and [VIO(2+)][Tf2N(-)]2 shows a more isotropic molecular distribution than [VIO(2+)][BF4(-)]2 and [EMI(+)][BF4(-)]. Additionally, we have simulated two modified viologen-based ILs to reinforce our interpretations. We conclude from the above simulation results that the rigidity of anions influences the alignment of cations and that the rigidity of cations shows a large obstacle to their rotational capacity. Moreover, we have observed a slower diffusion of [VIO(2+)][BF4(-)]2 due to the electrostatic correlations, which stabilizes the ion-cage effect.

Composite foam structures

NASA Technical Reports Server (NTRS)

Williams, Brian E. (Inventor); Brockmeyer, Jerry (Inventor); Tuffias, Robert H. (Inventor)

2005-01-01

A composite rigid foam structure that has a skin or coating on at least one of its surfaces. The skin is formed in situ by thermal spray techniques. The skin is bonded substantially throughout the surface of the porous substrate to the peripheries of the pores. The skin on the average does not penetrate the surface of the substrate by more than the depth of about 2 to 5 pores. Thus, thermal spraying the skin onto the rigid foam produces a composite that is tightly and uniformly bonded together without unduly increasing the weight of the composite structure. Both thermal conductivity and bonding are excellent.

A π-conjugated system with flexibility and rigidity that shows environment-dependent RGB luminescence.

PubMed

Yuan, Chunxue; Saito, Shohei; Camacho, Cristopher; Irle, Stephan; Hisaki, Ichiro; Yamaguchi, Shigehiro

2013-06-19

We have designed and synthesized a π-conjugated system that consists of a flexible and nonplanar π joint and two emissive rigid and planar wings. This molecular system exhibits respectively red, green, and blue (RGB) emission from a single-component luminophore in different environments, namely in polymer matrix, in solution, and in crystals. The flexible unit gives rise to a dynamic conformational change in the excited state from a nonplanar V-shaped structure to a planar structure, leading to a dual fluorescence of blue and green colors. The rigid and planar moieties favor the formation of a two-fold π-stacked array of the V-shaped molecules in the crystalline state, which produces a red excimer-like emission. These RGB emissions are attained without changing the excitation energy.

Calculating ensemble averaged descriptions of protein rigidity without sampling.

PubMed

González, Luis C; Wang, Hui; Livesay, Dennis R; Jacobs, Donald J

2012-01-01

Previous works have demonstrated that protein rigidity is related to thermodynamic stability, especially under conditions that favor formation of native structure. Mechanical network rigidity properties of a single conformation are efficiently calculated using the integer body-bar Pebble Game (PG) algorithm. However, thermodynamic properties require averaging over many samples from the ensemble of accessible conformations to accurately account for fluctuations in network topology. We have developed a mean field Virtual Pebble Game (VPG) that represents the ensemble of networks by a single effective network. That is, all possible number of distance constraints (or bars) that can form between a pair of rigid bodies is replaced by the average number. The resulting effective network is viewed as having weighted edges, where the weight of an edge quantifies its capacity to absorb degrees of freedom. The VPG is interpreted as a flow problem on this effective network, which eliminates the need to sample. Across a nonredundant dataset of 272 protein structures, we apply the VPG to proteins for the first time. Our results show numerically and visually that the rigidity characterizations of the VPG accurately reflect the ensemble averaged [Formula: see text] properties. This result positions the VPG as an efficient alternative to understand the mechanical role that chemical interactions play in maintaining protein stability.

Curating viscoelastic properties of icosahedral viruses, virus-based nanomaterials, and protein cages.

PubMed

Kant, Ravi; Rayaprolu, Vamseedhar; McDonald, Kaitlyn; Bothner, Brian

2018-06-01

The beauty, symmetry, and functionality of icosahedral virus capsids has attracted the attention of biologists, physicists, and mathematicians ever since they were first observed. Viruses and protein cages assemble into functional architectures in a range of sizes, shapes, and symmetries. To fulfill their biological roles, these structures must self-assemble, resist stress, and are often dynamic. The increasing use of icosahedral capsids and cages in materials science has driven the need to quantify them in terms of structural properties such as rigidity, stiffness, and viscoelasticity. In this study, we employed Quartz Crystal Microbalance with Dissipation technology (QCM-D) to characterize and compare the mechanical rigidity of different protein cages and viruses. We attempted to unveil the relationships between rigidity, radius, shell thickness, and triangulation number. We show that the rigidity and triangulation numbers are inversely related to each other and the comparison of rigidity and radius also follows the same trend. Our results suggest that subunit orientation, protein-protein interactions, and protein-nucleic acid interactions are important for the resistance to deformation of these complexes, however, the relationships are complex and need to be explored further. The QCM-D based viscoelastic measurements presented here help us elucidate these relationships and show the future prospect of this technique in the field of physical virology and nano-biotechnology.

Prediction of air blast mitigation in an array of rigid obstacles using smoothed particle hydrodynamics

NASA Astrophysics Data System (ADS)

Prasanna Kumar, S. S.; Patnaik, B. S. V.; Ramamurthi, K.

2018-04-01

The mitigation of blast waves propagating in air and interacting with rigid barriers and obstacles is numerically investigated using the mesh-free smoothed particle hydrodynamics method. A novel virtual boundary particle procedure with a skewed gradient wall boundary treatment is applied at the interfaces between air and rigid bodies. This procedure is validated with closed-form solutions for strong and weak shock reflection from rigid surfaces, supersonic flows over a wedge, formation of reflected, transverse, and Mach stem shocks, and also earlier experiments on interaction of a blast wave with concrete blocks. The mitigation of the overpressure and impulse transmitted to the protected structure due to an array of rigid obstacles of different shapes placed in the path of the blast wave is thereafter determined and discussed in the context of the existing experimental and numerical studies. It is shown that blockages having the shape of a right facing triangle or square placed in tandem or staggered provide better mitigation. The influence of the distance between the blockage array and protected structure is assessed, and the incorporation of a gap in the blockages is shown to improve the mitigation. The mechanisms responsible for the attenuation of air blast are identified through the simulations.

Steady-state structural fluctuation is a predictor of the necessity of pausing-mediated co-translational folding for small proteins.

PubMed

Huang, Wenxi; Liu, Wanting; Jin, Jingjie; Xiao, Qilan; Lu, Ruibin; Chen, Wei; Xiong, Sheng; Zhang, Gong

2018-03-25

Translational pausing coordinates protein synthesis and co-translational folding. It is a common factor that facilitates the correct folding of large, multi-domain proteins. For small proteins, pausing sites rarely occurs in the gene body, and the 3'-end pausing sites are only essential for the folding of a fraction of proteins. The determinant of the necessity of the pausings remains obscure. In this study, we demonstrated that the steady-state structural fluctuation is a predictor of the necessity of pausing-mediated co-translational folding for small proteins. Validated by experiments with 5 model proteins, we found that the rigid protein structures do not, while the flexible structures do need 3'-end pausings to fold correctly. Therefore, rational optimization of translational pausing can improve soluble expression of small proteins with flexible structures, but not the rigid ones. The rigidity of the structure can be quantitatively estimated in silico using molecular dynamic simulation. Nevertheless, we also found that the translational pausing optimization increases the fitness of the expression host, and thus benefits the recombinant protein production, independent from the soluble expression. These results shed light on the structural basis of the translational pausing and provided a practical tool for industrial protein fermentation. Copyright © 2017. Published by Elsevier Inc.

Structural Analysis Computer Programs for Rigid Multicomponent Pavement Structures with Discontinuities--WESLIQID and WESLAYER. Report 1. Program Development and Numerical Presentations.

DTIC Science & Technology

1981-05-01

represented as a Winkler foundation. The program can treat any number of slabs connected by steel bars or other load trans- fer devices at the joints...dimensional finite element method. The inherent flexibility of such an approach permits the analysis of a rigid pavement with steel bars and stabilized...layers and provides an efficient tool for analyzing stress conditions at the joint. Unfor- tunately, such a procedure would require a tremendously

Introducing a Rigid Loop Structure from Deer into Mouse Prion Protein Increases Its Propensity for Misfolding In Vitro

PubMed Central

Kyle, Leah M.; John, Theodore R.; Schätzl, Hermann M.; Lewis, Randolph V.

2013-01-01

Prion diseases are fatal neurodegenerative disorders characterized by misfolding of the cellular prion protein (PrPc) into the disease-associated isoform (PrPSc) that has increased β-sheet content and partial resistance to proteolytic digestion. Prion diseases from different mammalian species have varying propensities for transmission upon exposure of an uninfected host to the infectious agent. Chronic Wasting Disease (CWD) is a highly transmissible prion disease that affects free ranging and farmed populations of cervids including deer, elk and moose, as well as other mammals in experimental settings. The molecular mechanisms allowing CWD to maintain comparatively high transmission rates have not been determined. Previous work has identified a unique structural feature in cervid PrP, a rigid loop between β-sheet 2 and α-helix 2 on the surface of the protein. This study was designed to test the hypothesis that the rigid loop has a direct influence on the misfolding process. The rigid loop was introduced into murine PrP as the result of two amino acid substitutions: S170N and N174T. Wild-type and rigid loop murine PrP were expressed in E. coli and purified. Misfolding propensity was compared for the two proteins using biochemical techniques and cell free misfolding and conversion systems. Murine PrP with a rigid loop misfolded in cell free systems with greater propensity than wild type murine PrP. In a lipid-based conversion assay, rigid loop PrP converted to a PK resistant, aggregated isoform at lower concentrations than wild-type PrP. Using both proteins as substrates in real time quaking-induced conversion, rigid loop PrP adopted a misfolded isoform more readily than wild type PrP. Taken together, these findings may help explain the high transmission rates observed for CWD within cervids. PMID:23825561

Polymorphism complexity and handedness inversion in serum albumin amyloid fibrils.

PubMed

Usov, Ivan; Adamcik, Jozef; Mezzenga, Raffaele

2013-12-23

Protein-based amyloid fibrils can show a great variety of polymorphic structures within the same protein precursor, although the origins of these structural homologues remain poorly understood. In this work we investigate the fibrillation of bovine serum albumin--a model globular protein--and we follow the polymorphic evolution by a statistical analysis of high-resolution atomic force microscopy images, complemented, at larger length scales, by concepts based on polymer physics formalism. We identify six distinct classes of coexisting amyloid fibrils, including flexible left-handed twisted ribbons, rigid right-handed helical ribbons and nanotubes. We show that the rigid fibrils originate from flexible fibrils through two diverse polymorphic transitions, first, via a single-fibril transformation when the flexible left-handed twisted ribbons turn into the helical left-handed ribbons, to finally evolve into nanotube-like structures, and second, via a double-fibril transformation when two flexible left-handed twisted ribbons wind together resulting in a right-handed twisted ribbon, followed by a rigid right-handed helical ribbon polymorphic conformation. Hence, the change in handedness occurs with an increase in the level of the fibril's structural organization.

Ground level enhancements of cosmic rays in solar cycle 24

NASA Astrophysics Data System (ADS)

Kravtsova, M. V.; Sdobnov, V. E.

2017-07-01

Using data from ground-based observations of cosmic rays (CRs) on the worldwide network of stations and spacecraft, we have investigated the proton spectra and the CR anisotropy during the ground level enhancements of CRs on May 17, 2012 (GLE71) and January 6, 2014 (GLE72) occurred in solar cycle 24 by the spectrographic global survey method. We provide the CR rigidity spectra and the relative changes in the intensity of CRs with a rigidity of 2 GV in the solar-ecliptic geocentric coordinate system in specific periods of these events. We show that the proton acceleration during GLE71 and GLE72 occurred up to rigidities R 2.3-2.5 GV, while the differential rigidity spectra of solar CRs are described neither by a power nor by an exponential function of particle rigidity. At the times of the events considered the Earth was in a loop-like structure of the interplanetary magnetic field.

Three-dimensional water impact at normal incidence to a blunt structure

PubMed Central

Cooker, M. J.; Korobkin, A. A.

2016-01-01

The three-dimensional water impact onto a blunt structure with a spreading rectangular contact region is studied. The structure is mounted on a flat rigid plane with the impermeable curved surface of the structure perpendicular to the plane. Before impact, the water region is a rectangular domain of finite thickness bounded from below by the rigid plane and above by the flat free surface. The front free surface of the water region is vertical, representing the front of an advancing steep wave. The water region is initially advancing towards the structure at a constant uniform speed. We are concerned with the slamming loads acting on the surface of the structure during the initial stage of water impact. Air, gravity and surface tension are neglected. The problem is analysed by using some ideas of pressure-impulse theory, but including the time-dependence of the wetted area of the structure. The flow caused by the impact is three-dimensional and incompressible. The distribution of the pressure-impulse (the time-integral of pressure) over the surface of the structure is analysed and compared with the distributions provided by strip theories. The total impulse exerted on the structure during the impact stage is evaluated and compared with numerical and experimental predictions. An example calculation is presented of water impact onto a vertical rigid cylinder. Three-dimensional effects on the slamming loads are the main concern in this study. PMID:27616912

Deformation behavior of dragonfly-inspired nodus structured wing in gliding flight through experimental visualization approach.

PubMed

Zhang, Sheng; Sunami, Yuta; Hashimoto, Hiromu

2018-04-10

Dragonfly has excellent flight performance and maneuverability due to the complex vein structure of wing. In this research, nodus as an important structural element of the dragonfly wing is investigated through an experimental visualization approach. Three vein structures were fabricated as, open-nodus structure, closed-nodus structure (with a flex-limiter) and rigid wing. The samples were conducted in a wind tunnel with a high speed camera to visualize the deformation of wing structure in order to study the function of nodus structured wing in gliding flight. According to the experimental results, nodus has a great influence on the flexibility of the wing structure. Moreover, the closed-nodus wing (with a flex-limiter) enables the vein structure to be flexible without losing the strength and rigidity of the joint. These findings enhance the knowledge of insect-inspired nodus structured wing and facilitate the application of Micro Air Vehicle (MAV) in gliding flight.

Auxetic behaviour from rotating rigid units

NASA Astrophysics Data System (ADS)

Grima, J. N.; Alderson, A.; Evans, K. E.

2005-03-01

Auxetic materials exhibit the unexpected feature of becoming fatter when stretched and narrower when compressed, in other words, they exhibit a negative Poisson's ratio. This counter-intuitive behaviour imparts many beneficial effects on the material's macroscopic properties that make auxetics superior to conventional materials in many commercial applications. Recent research suggests that auxetic be-haviour generally results from a cooperative effect between the material's internal structure (geometry setup) and the deformation mechanism it undergoes when submitted to a stress. Auxetic behaviour is also known to be scale-independent, and thus, the same geometry/deformation mechanism may operate at the macro-, micro- and nano- (molecular) level. A considerable amount of research has been focused on the re-entrant honeycomb structure which exhibits auxetic behaviour if deformed through hinging at the joints or flexure of the ribs, and it was proposed that this re-entrant geometry plays an impor- tant role in generating auxetic behaviour in various forms of materials ranging from nanostructured polymers to foams. This paper discusses an alternative mode of deformation involving rotating rigid units which also results in negative Poisson's ratios. In its most ideal form, this mechanism may be construc- ted in two dimensions using rigid polygons connected together through hinges at their vertices. On application of uniaxial loads, these rigid polygons rotate with respect to each other to form a more open structure hence giving rise to a negative Poisson's ratio. This paper also discusses the role that rotating rigid units are thought to have in various classes of materials to give rise to negative Poisson's ratios.

Flight dynamics simulation modeling and control of a large flexible tiltrotor aircraft

NASA Astrophysics Data System (ADS)

Juhasz, Ondrej

A high order rotorcraft mathematical model is developed and validated against the XV-15 and a Large Civil Tiltrotor (LCTR) concept. The mathematical model is generic and allows for any rotorcraft configuration, from single main rotor helicopters to coaxial and tiltrotor aircraft. Rigid-body and inflow states, as well as flexible wing and blade states are used in the analysis. The separate modeling of each rotorcraft component allows for structural flexibility to be included, which is important when modeling large aircraft where structural modes affect the flight dynamics frequency ranges of interest, generally 1 to 20 rad/sec. Details of the formulation of the mathematical model are given, including derivations of structural, aerodynamic, and inertial loads. The linking of the components of the aircraft is developed using an approach similar to multibody analyses by exploiting a tree topology, but without equations of constraints. Assessments of the effects of wing flexibility are given. Flexibility effects are evaluated by looking at the nature of the couplings between rigid-body modes and wing structural modes and vice versa. The effects of various different forms of structural feedback on aircraft dynamics are analyzed. A proportional-integral feedback on the structural acceleration is deemed to be most effective at both improving the damping and reducing the overall excitation of a structural mode. A model following control architecture is then implemented on full order flexible LCTR models. For this aircraft, the four lowest frequency structural modes are below 20 rad/sec, and are thus needed for control law development and analysis. The impact of structural feedback on both Attitude-Command, Attitude-Hold (ACAH) and Translational Rate Command (TRC) response types are investigated. A rigid aircraft model has optimistic performance characteristics, and a control system designed for a rigid aircraft could potentially destabilize a flexible one. The various control systems are flown in a fixed-base simulator. Pilot inputs and aircraft performance are recorded and analyzed.

Structures to Resist the Effects of Accidental Explosions. Volume 6. Special Considerations in Explosive Facility Design

DTIC Science & Technology

1985-04-01

mass is taken to be a rigid body . It is assumed that the base of the system is subjected to a periodic sinusoidal motion whose frequency is f. The...Step 9. Verify rigid body motion of the platform. - ■■:’-^V’^’:-’ The natural frequency of the individual members of the platform should be at least...5 times greater than the natural frequency of the system for rigid body motion of the platform to occur. - .’ : To increase the frequency of the

Origami Metamaterial based on Pattern Rigidity

NASA Astrophysics Data System (ADS)

Chen, Yan; You, Zhong

Origami inspired mechanical metamaterials are made from a tessellation of origami units. Their mechanical behaviour is closely related to the behaviour of the origami units used. In this article, we focus on a family of metamaterials that are created by the tessellation of the square twist origami units. Generally a square twist origami unit can have four distinct hill-valley crease arrangements, two of which are rigidly foldable whereas the others are not. The rigidly foldable unit has, in general, lower stiffness than that of the non-rigidly foldable one if the facets can easily rotate about the creases. We shall show that it is possible to put rigidly foldable and non-rigidly foldable units together to form a geometrically compatible tessellation, and the stiffness of the overall structure based on such a tessellation is primarily decided by the number of non-rigid units. By astutely placing such units in a tessellation, we are able to create a metamaterial with a tunable stiffness. Y Chen acknowledges the support of the NSFC (Projects 51290293 and 51422506) and the Ministry of Science and Technology of China (Project 2014DFA70710). Z You wishes to acknowledge the support of Air Force Office of Scientific Research (FA9550-16-1-0339).

MASPROP- MASS PROPERTIES OF A RIGID STRUCTURE

NASA Technical Reports Server (NTRS)

Hull, R. A.

1994-01-01

The computer program MASPROP was developed to rapidly calculate the mass properties of complex rigid structural systems. This program's basic premise is that complex systems can be adequately described by a combination of basic elementary structural shapes. Thirteen widely used basic structural shapes are available in this program. They are as follows: Discrete Mass, Cylinder, Truncated Cone, Torus, Beam (arbitrary cross section), Circular Rod (arbitrary cross section), Spherical Segment, Sphere, Hemisphere, Parallelepiped, Swept Trapezoidal Panel, Symmetric Trapezoidal Panels, and a Curved Rectangular Panel. MASPROP provides a designer with a simple technique that requires minimal input to calculate the mass properties of a complex rigid structure and should be useful in any situation where one needs to calculate the center of gravity and moments of inertia of a complex structure. Rigid body analysis is used to calculate mass properties. Mass properties are calculated about component axes that have been rotated to be parallel to the system coordinate axes. Then the system center of gravity is calculated and the mass properties are transferred to axes through the system center of gravity by using the parallel axis theorem. System weight, moments of inertia about the system origin, and the products of inertia about the system center of mass are calculated and printed. From the information about the system center of mass the principal axes of the system and the moments of inertia about them are calculated and printed. The only input required is simple geometric data describing the size and location of each element and the respective material density or weight of each element. This program is written in FORTRAN for execution on a CDC 6000 series computer with a central memory requirement of approximately 62K (octal) of 60 bit words. The development of this program was completed in 1978.

Kodak AMSD Concept Overview and Status (Semi-Rigid Mirror with Sparse Actuators)

NASA Technical Reports Server (NTRS)

Matthews, Gary; Maji, Arup K. (Technical Monitor)

2001-01-01

This talk will review Kodak's current AMSD technical and schedule status. For AMSD, Kodak is fabricating a semi-rigid closed-back egg-crate glass mirror, a graphite composite reaction structure, and 16 force actuators for figure control. The mirror is currently on schedule for cryotesting in early '02.

Impact of Growth in the Universe of Subjects on Classification.

ERIC Educational Resources Information Center

Ranganathan, Shiyali Ramamritam

The development of the removal of rigidity in library classification is traced from the Enumerative Classification of DC (1876) through the Nearly-Faceted Classification of UDC (1896), the rigidly, though fully faceted version of CC (1933), the generalized faceted structure of version 2 of CC (1949), down to the Freely Faceted Classification of…

Complexity management theory: motivation for ideological rigidity and social conflict.

PubMed

Peterson, Jordan B; Flanders, Joseph L

2002-06-01

We are doomed to formulate conceptual structures that are much simpler than the complex phenomena they are attempting to account for. These simple conceptual structures shield us, pragmatically, from real-world complexity, but also fail, frequently, as some aspect of what we did not take into consideration makes itself manifest. The failure of our concepts dysregulates our emotions and generates anxiety, necessarily, as the unconstrained world is challenging and dangerous. Such dysregulation can turn us into rigid, totalitarian dogmatists, as we strive to maintain the structure of our no longer valid beliefs. Alternatively, we can face the underlying complexity of experience, voluntarily, gather new information, and recast and reconfigure the structures that underly our habitable worlds.

A soft-rigid contact model of MPM for granular flow impact on retaining structures

NASA Astrophysics Data System (ADS)

Li, Xinpo; Xie, Yanfang; Gutierrez, Marte

2018-02-01

Protective measures against hazards associated with rapid debris avalanches include a variety of retaining structures such as rock/boulder fences, gabions, earthfill barriers and retaining walls. However, the development of analytical and numerical methods for the rational assessment of impact force generated by granular flows is still a challenge. In this work, a soft-rigid contact model is built under the coding framework of MPM which is a hybrid method with Eulerian-Lagrangian description. The soft bodies are discretized into particles (material points), and the rigid bodies are presented by rigid node-based surfaces. Coulomb friction model is used to implement the modeled contact mechanics, and a velocity-dependent friction coefficient is coupled into the model. Simulations of a physical experiment show that the peak and residual value of impact forces are well captured by the MPM model. An idealized scenario of debris avalanche flow down a hillslope and impacting on a retaining wall are analyzed using the MPM model. The calculated forces can provide a quantitative estimate from which mound design could proceed for practical implementation in the field.

Effects of dielectric inhomogeneity on electrostatic twist rigidity of a helical biomolecule in Debye-Hückel regime

NASA Astrophysics Data System (ADS)

Rezaie-Dereshgi, Amir; Mohammad-Rafiee, Farshid

2018-04-01

The electrostatic interactions play a crucial role in biological systems. Here we consider an impermeable dielectric molecule in the solvent with a different dielectric constant. The electrostatic free energy in the problem is studied in the Debye-Hückel regime using the analytical Green function that is calculated in the paper. Using this electrostatic free energy, we study the electrostatic contribution to the twist rigidity of a double stranded helical molecule such as a DNA and an actin filament. The dependence of the electrostatic twist rigidity of the molecule to the dielectric inhomogeneity, structural parameters, and the salt concentration is studied. It is shown that, depending on the parameters, the electrostatic twist rigidity could be positive or negative.

Rigid spine reinforced polymer microelectrode array probe and method of fabrication

DOEpatents

Tabada, Phillipe; Pannu, Satinderpall S

2014-05-27

A rigid spine-reinforced microelectrode array probe and fabrication method. The probe includes a flexible elongated probe body with conductive lines enclosed within a polymeric material. The conductive lines connect microelectrodes found near an insertion end of the probe to respective leads at a connector end of the probe. The probe also includes a rigid spine, such as made from titanium, fixedly attached to the probe body to structurally reinforce the probe body and enable the typically flexible probe body to penetrate and be inserted into tissue, such as neural tissue. By attaching or otherwise fabricating the rigid spine to connect to only an insertion section of the probe body, an integrally connected cable section of the probe body may remain flexible.

Rigid-Cluster Models of Conformational Transitions in Macromolecular Machines and Assemblies

PubMed Central

Kim, Moon K.; Jernigan, Robert L.; Chirikjian, Gregory S.

2005-01-01

We present a rigid-body-based technique (called rigid-cluster elastic network interpolation) to generate feasible transition pathways between two distinct conformations of a macromolecular assembly. Many biological molecules and assemblies consist of domains which act more or less as rigid bodies during large conformational changes. These collective motions are thought to be strongly related with the functions of a system. This fact encourages us to simply model a macromolecule or assembly as a set of rigid bodies which are interconnected with distance constraints. In previous articles, we developed coarse-grained elastic network interpolation (ENI) in which, for example, only Cα atoms are selected as representatives in each residue of a protein. We interpolate distance differences of two conformations in ENI by using a simple quadratic cost function, and the feasible conformations are generated without steric conflicts. Rigid-cluster interpolation is an extension of the ENI method with rigid-clusters replacing point masses. Now the intermediate conformations in an anharmonic pathway can be determined by the translational and rotational displacements of large clusters in such a way that distance constraints are observed. We present the derivation of the rigid-cluster model and apply it to a variety of macromolecular assemblies. Rigid-cluster ENI is then modified for a hybrid model represented by a mixture of rigid clusters and point masses. Simulation results show that both rigid-cluster and hybrid ENI methods generate sterically feasible pathways of large systems in a very short time. For example, the HK97 virus capsid is an icosahedral symmetric assembly composed of 60 identical asymmetric units. Its original Hessian matrix size for a Cα coarse-grained model is >(300,000)2. However, it reduces to (84)2 when we apply the rigid-cluster model with icosahedral symmetry constraints. The computational cost of the interpolation no longer scales heavily with the size of structures; instead, it depends strongly on the minimal number of rigid clusters into which the system can be decomposed. PMID:15833998

Rigidity of Glasses and Macromolecules

NASA Astrophysics Data System (ADS)

Thorpe, M. F.

1998-03-01

The simple yet powerful ideas of percolation theory have found their way into many different areas of research. In this talk we show how RIGIDITY PERCOLATION can be studied at a similar level of sophistication, using a powerful new program THE PEBBLE GAME (D. J. Jacobs and M. F. Thorpe, Phys. Rev. E) 53, 3682 (1996). that uses an integer algorithm. This program can analyse the rigidity of two and three dimensional networks containing more than one million bars and joints. We find the total number of floppy modes, and find the critical behavior as the network goes from floppy to rigid as more bars are added. We discuss the relevance of this work to network glasses, and how it relates to experiments that involve the mechanical properties like hardness and elasticity of covalent glassy networks like Ge_xAs_ySe_1-x-y and dicuss recent experiments that suggest that the rigidity transition may be first order (Xingwei Feng, W. J.Bresser and P. Boolchand, Phys. Rev. Lett 78), 4422 (1997).. This approach is also useful in macromolecules and proteins, where detailed information about the rigid domain structure can be obtained.

Rigid collapsible dish structure

NASA Technical Reports Server (NTRS)

Palmer, William B. (Inventor); Giebler, Martin M. (Inventor)

1982-01-01

A collapsible dish structure composed of a plurality of rows of rigid radial petal assemblies concentric with the axis of the dish. The petal assemblies consist of a center petal and two side petals, the center petal hinged on an axis tangent to a circle concentric with the axis of the dish and the side petals hinged to the center petal at their mating edge. The center petal is foldable inwardly and the side petals rotate about their hinges such that the collapsed dish structure occupies a much smaller volume than the deployed dish. Means of controlling the shape of the dish to compensate for differential expansion of the deployed dish are also provided.

Activated carbon fiber composite material and method of making

DOEpatents

Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

2000-01-01

An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

Activated carbon fiber composite material and method of making

DOEpatents

Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

2001-01-01

An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

Indentation versus Rolling: Dependence of Adhesion on Contact Geometry for Biomimetic Structures.

PubMed

Moyle, Nichole; He, Zhenping; Wu, Haibin; Hui, Chung-Yuen; Jagota, Anand

2018-04-03

Numerous biomimetic structures made from elastomeric materials have been developed to produce enhancement in properties such as adhesion, static friction, and sliding friction. As a property, one expects adhesion to be represented by an energy per unit area that is usually sensitive to the combination of shear and normal stresses at the crack front but is otherwise dependent only on the two elastic materials that meet at the interface. More specifically, one would expect that adhesion measured by indentation (a popular and convenient technique) could be used to predict adhesion hysteresis in the more practically important rolling geometry. Previously, a structure with a film-terminated fibrillar geometry exhibited dramatic enhancement of adhesion by a crack-trapping mechanism during indentation with a rigid sphere. Roughly isotropic structures such as the fibrillar geometry show a strong correlation between adhesion enhancement in indentation versus adhesion hysteresis in rolling. However, anisotropic structures, such as a film-terminated ridge-channel geometry, surprisingly show a dramatic divergence between adhesion measured by indentation versus rolling. We study this experimentally and theoretically, first comparing the adhesion of the anisotropic ridge-channel structure to the roughly isotropic fibrillar structure during indentation with a rigid sphere, where only the isotropic structure shows adhesion enhancement. Second, we examine in more detail the anomalous anisotropic film-terminated ridge-channel structure during indentation with a rigid sphere versus rolling to show why these structures show a dramatic adhesion enhancement for the rolling case and no adhesion enhancement for indentation.

Mechanical Response Analysis of Long-life Asphalt Pavement Structure of Yunluo High-speed on the Semi-rigid Base

NASA Astrophysics Data System (ADS)

Liu, Feng; Wu, Chuanhai; Xu, Xinquan; Li, Hao; Wang, Zhixiang

2018-01-01

In order to grasp the rule of the strain change of the semi-rigid asphalt pavement structure under the FWD load and provide a reliable theoretical and practical basis for the design of the pavement structure, based on the test section of Guangdong Yunluo expressway, taking FWD as the loading tool, by using the finite element analysis software ANSYS, the internal variation rules of each pavement structural layer were obtained. Based on the results of the theoretical analysis, the measured strain sensor was set up in the corresponding layer of the pavement structure, and the strain test plan was determined. Based on the analysis of the strain data obtained from several structural layers and field monitoring, the rationality of the type pavement structure and the strain test scheme were verified, so as to provide useful help for the design and the maintenance of the pavement structure.

Non-rigid Reconstruction of Casting Process with Temperature Feature

NASA Astrophysics Data System (ADS)

Lin, Jinhua; Wang, Yanjie; Li, Xin; Wang, Ying; Wang, Lu

2017-09-01

Off-line reconstruction of rigid scene has made a great progress in the past decade. However, the on-line reconstruction of non-rigid scene is still a very challenging task. The casting process is a non-rigid reconstruction problem, it is a high-dynamic molding process lacking of geometric features. In order to reconstruct the casting process robustly, an on-line fusion strategy is proposed for dynamic reconstruction of casting process. Firstly, the geometric and flowing feature of casting are parameterized in manner of TSDF (truncated signed distance field) which is a volumetric block, parameterized casting guarantees real-time tracking and optimal deformation of casting process. Secondly, data structure of the volume grid is extended to have temperature value, the temperature interpolation function is build to generate the temperature of each voxel. This data structure allows for dynamic tracking of temperature of casting during deformation stages. Then, the sparse RGB features is extracted from casting scene to search correspondence between geometric representation and depth constraint. The extracted color data guarantees robust tracking of flowing motion of casting. Finally, the optimal deformation of the target space is transformed into a nonlinear regular variational optimization problem. This optimization step achieves smooth and optimal deformation of casting process. The experimental results show that the proposed method can reconstruct the casting process robustly and reduce drift in the process of non-rigid reconstruction of casting.

Chain Confinement in Electrospun Nanocomposites: using Thermal Analysis to Investigate Polymer-Filler Interactions

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

Q Ma; B Mao; P Cebe

2011-12-31

We investigate the interaction of the polymer matrix and filler in electrospun nanofibers using advanced thermal analysis methods. In particular, we study the ability of silicon dioxide nanoparticles to affect the phase structure of poly(ethylene terephthalate), PET. SiO{sub 2} nanoparticles (either unmodified or modified with silane) ranging from 0 to 2.0 wt% in PET were electrospun from hexafluoro-2-propanol solutions. The morphologies of both the electrospun (ES) nanofibers and the SiO{sub 2} powders were observed by scanning and transmission electron microscopy, while the amorphous or crystalline nature of the fibers was determined by real-time wide-angle X-ray scattering. The fractions of themore » crystal, mobile amorphous, and rigid amorphous phases of the non-woven, nanofibrous composite mats were quantified by using heat capacity measurements. The amount of the immobilized polymer layer, the rigid amorphous fraction, was obtained from the specific reversing heat capacity for both as-spun amorphous fibers and isothermally crystallized fibers. Existence of the rigid amorphous phase in the absence of crystallinity was verified in nanocomposite fibers, and two origins for confinement of the rigid amorphous fraction are proposed. Thermal analysis of electrospun fibers, including quasi-isothermal methods, provides new insights to quantitatively characterize the polymer matrix phase structure and thermal transitions, such as devitrification of the rigid amorphous fraction.« less

Magnetoimpedance effect in the FeNi/Ti-based multilayered structure: A pressure sensor prototype

NASA Astrophysics Data System (ADS)

Chlenova, A. A.; Melnikov, G. Yu.; Svalov, A. V.; Kurlyandskaya, G. V.

2016-09-01

Magnetically soft [Ti/FeNi]5/Ti/Cu/Ti/[FeNi/Ti]4 multilayered structures were obtained by magnetron sputtering. Based on them sensitive elements have been investigated with focus on the design of the giant magnetoimpedance (MI) pressure sensors. Magnetic properties and MI of fabricated sensitive elements were comparatively analyzed for both multilayers deposited both onto rigid and flexible polymer substrates. Structures on a rigid substrate had the highest MI ratio of 140 %. They showed the sensitivity of 0.70 %/Ba suitable for possible applications in pressure sensing. Structures deposited onto flexible Cyclo Olefin Copolymer substrates had slightly lower sensitivity of 0.55 %/Ba. That structures showing linear dependence of MI ratio in the pressure range of 0 to 360 Ba are promising for microfluidic and biosensor applications.

iATTRACT: simultaneous global and local interface optimization for protein-protein docking refinement.

PubMed

Schindler, Christina E M; de Vries, Sjoerd J; Zacharias, Martin

2015-02-01

Protein-protein interactions are abundant in the cell but to date structural data for a large number of complexes is lacking. Computational docking methods can complement experiments by providing structural models of complexes based on structures of the individual partners. A major caveat for docking success is accounting for protein flexibility. Especially, interface residues undergo significant conformational changes upon binding. This limits the performance of docking methods that keep partner structures rigid or allow limited flexibility. A new docking refinement approach, iATTRACT, has been developed which combines simultaneous full interface flexibility and rigid body optimizations during docking energy minimization. It employs an atomistic molecular mechanics force field for intermolecular interface interactions and a structure-based force field for intramolecular contributions. The approach was systematically evaluated on a large protein-protein docking benchmark, starting from an enriched decoy set of rigidly docked protein-protein complexes deviating by up to 15 Å from the native structure at the interface. Large improvements in sampling and slight but significant improvements in scoring/discrimination of near native docking solutions were observed. Complexes with initial deviations at the interface of up to 5.5 Å were refined to significantly better agreement with the native structure. Improvements in the fraction of native contacts were especially favorable, yielding increases of up to 70%. © 2014 Wiley Periodicals, Inc.

Method to estimate center of rigidity using vibration recordings

USGS Publications Warehouse

Safak, Erdal; Çelebi, Mehmet

1990-01-01

A method to estimate the center of rigidity of buildings by using vibration recordings is presented. The method is based on the criterion that the coherence of translational motions with the rotational motion is minimum at the center of rigidity. Since the coherence is a function of frequency, a gross but frequency-independent measure of the coherency is defined as the integral of the coherence function over the frequency. The center of rigidity is determined by minimizing this integral. The formulation is given for two-dimensional motions. Two examples are presented for the method; a rectangular building with ambient-vibration recordings, and a triangular building with earthquake-vibration recordings. Although the examples given are for buildings, the method can be applied to any structure with two-dimensional motions.

Solution structure of an antifreeze protein CfAFP-501 from Choristoneura fumiferana.

PubMed

Li, Congmin; Guo, Xianrong; Jia, Zongchao; Xia, Bin; Jin, Changwen

2005-07-01

Antifreeze proteins (AFPs) are widely employed by various organisms as part of their overwintering survival strategy. AFPs have the unique ability to suppress the freezing point of aqueous solution and inhibit ice recrystallization through binding to the ice seed crystals and restricting their growth. The solution structure of CfAFP-501 from spruce budworm has been determined by NMR spectroscopy. Our result demonstrates that CfAFP-501 retains its rigid and highly regular structure in solution. Overall, the solution structure is similar to the crystal structure except the N- and C-terminal regions. NMR spin-relaxation experiments further indicate the overall rigidity of the protein and identify a collection of residues with greater flexibilities. Furthermore, Pro91 shows a cis conformation in solution instead of the trans conformation determined in the crystal structure.

Composite theory applied to elastomers

NASA Technical Reports Server (NTRS)

Clark, S. K.

1986-01-01

Reinforced elastomers form the basis for most of the structural or load carrying applications of rubber products. Computer based structural analysis in the form of finite element codes was highly successful in refining structural design in both isotropic materials and rigid composites. This has lead the rubber industry to attempt to make use of such techniques in the design of structural cord-rubber composites. While such efforts appear promising, they were not easy to achieve for several reasons. Among these is a distinct lack of a clearly defined set of material property descriptors suitable for computer analysis. There are substantial differences between conventional steel, aluminum, or even rigid composites such as graphite-epoxy, and textile-cord reinforced rubber. These differences which are both conceptual and practical are discussed.

Multi-Conformation Monte Carlo: A Method for Introducing Flexibility in Efficient Simulations of Many-Protein Systems.

PubMed

Prytkova, Vera; Heyden, Matthias; Khago, Domarin; Freites, J Alfredo; Butts, Carter T; Martin, Rachel W; Tobias, Douglas J

2016-08-25

We present a novel multi-conformation Monte Carlo simulation method that enables the modeling of protein-protein interactions and aggregation in crowded protein solutions. This approach is relevant to a molecular-scale description of realistic biological environments, including the cytoplasm and the extracellular matrix, which are characterized by high concentrations of biomolecular solutes (e.g., 300-400 mg/mL for proteins and nucleic acids in the cytoplasm of Escherichia coli). Simulation of such environments necessitates the inclusion of a large number of protein molecules. Therefore, computationally inexpensive methods, such as rigid-body Brownian dynamics (BD) or Monte Carlo simulations, can be particularly useful. However, as we demonstrate herein, the rigid-body representation typically employed in simulations of many-protein systems gives rise to certain artifacts in protein-protein interactions. Our approach allows us to incorporate molecular flexibility in Monte Carlo simulations at low computational cost, thereby eliminating ambiguities arising from structure selection in rigid-body simulations. We benchmark and validate the methodology using simulations of hen egg white lysozyme in solution, a well-studied system for which extensive experimental data, including osmotic second virial coefficients, small-angle scattering structure factors, and multiple structures determined by X-ray and neutron crystallography and solution NMR, as well as rigid-body BD simulation results, are available for comparison.

Swimming of an assembly of rigid spheres at low Reynolds number.

PubMed

Felderhof, B U

2014-11-01

A matrix formulation is derived for the calculation of the swimming speed and the power required for swimming of an assembly of rigid spheres immersed in a viscous fluid of infinite extent. The spheres may have arbitrary radii and may interact with elastic forces. The analysis is based on the Stokes mobility matrix of the set of spheres, defined in low Reynolds number hydrodynamics. For small amplitude, swimming optimization of the swimming speed at given power leads to an eigenvalue problem. The method allows straightforward calculation of the swimming performance of structures modeled as assemblies of interacting rigid spheres.

Metastable Amyloid Phases and their Conversion to Mature Fibrils

NASA Astrophysics Data System (ADS)

Muschol, Martin; Miti, Tatiana; Mulaj, Mentor; Schmit, Jeremy

Self-assembly of proteins into amyloid fibrils plays a key role in both functional biological responses and pathogenic disorders which include Alzheimer's disease and type II diabetes. Amyloid fibril assembly frequently generates compact oligomeric and curvilinear polymeric intermediates which are implicated to be toxic to cells. Yet, the relation between these early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. Our measurements indicate that lysozyme amyloid oligomers and their curvilinear fibrils only form after crossing a salt and protein concentration dependent threshold. These oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. Our experimental transition boundaries match well with colloidal model predictions accounting for salt-modulated charge repulsion. We also report our preliminary findings on the mechanism by which these metastable oligomeric phases are converted into stable amyloid fibrils.

The NASTRAN User's Manual Level 16.0 and Supplement

NASA Technical Reports Server (NTRS)

1976-01-01

The user's manual is restricted to those items related to the use of NASTRAN that are independent of the computing system being used. The features of NASTRAN described include: (1) procedures for defining and loading a structural model and a functional reference for every card that is used for structural modeling; (2) the NASTRAN data deck, including the details for each of the data cards; (3) the NASTRAN control cards that are associated with the use of the program; (4) rigid format procedures, along with specific instructions for the use of each rigid format: (5) procedures for using instructions for the use of each rigid format; (5) procedures for using the NASTRAN plotting capability; (6) procedures governing the creation of DMAP programs; and (7) the NASTRAN diagnostic messages. The NASTRAN dictionary of mnemonics, acronyms, phrases, and other commonly used NASTRAN terms is included along with a limited number of sample problems.

Matching multiple rigid domain decompositions of proteins

PubMed Central

Flynn, Emily; Streinu, Ileana

2017-01-01

We describe efficient methods for consistently coloring and visualizing collections of rigid cluster decompositions obtained from variations of a protein structure, and lay the foundation for more complex setups that may involve different computational and experimental methods. The focus here is on three biological applications: the conceptually simpler problems of visualizing results of dilution and mutation analyses, and the more complex task of matching decompositions of multiple NMR models of the same protein. Implemented into the KINARI web server application, the improved visualization techniques give useful information about protein folding cores, help examining the effect of mutations on protein flexibility and function, and provide insights into the structural motions of PDB proteins solved with solution NMR. These tools have been developed with the goal of improving and validating rigidity analysis as a credible coarse-grained model capturing essential information about a protein’s slow motions near the native state. PMID:28141528

Polymer Architecture Effects in Confined Geometry: Molecular Dynamics Simulation Study

NASA Astrophysics Data System (ADS)

Wijesinghe, Sidath; Perahia, Dvora; Grest, Gary

Luminescent rigid polymers confined into nanoparticles, or polydots, are emerging as a promising tool for nano medicine. The constrained architecture of a rigid backbone trapped in nano-dimensions results in photophysics that differs from that of spontaneously assembled rigid polymers. Incorporating ionizable functionalities in the polymers, often required for therapeutics, impacts the polymer conformation in solution. Here we report fully atomistic molecular dynamics simulations on the structure of dialkyl p-phenylene ethynylene confined into polydots. We find that the structure and thermal stability of polydots are sensitive to both the molecular weight n and the carboxylation fraction f. At room temperature , polydots remain confined regardless of n and f . However, as temperature is increased, polydots with lower n or f rearrange whereas polydots with higher n or fremain confined, though no direct clustering of the ionic groups was observed. NSF CHE 1308298 is acknowledged.

A rigid disc for protection of exposed blood vessels during negative pressure wound therapy.

PubMed

Anesäter, Erik; Borgquist, Ola; Torbrand, Christian; Roupé, K Markus; Ingemansson, Richard; Lindstedt, Sandra; Malmsjö, Malin

2013-02-01

There are increasing reports of serious complications and deaths associated with negative pressure wound therapy (NPWT). Bleeding may occur when NPWT is applied to a wound with exposed blood vessels. Inserting a rigid disc in the wound may protect these structures. The authors examined the effects of rigid discs on wound bed tissue pressure and blood flow through a large blood vessel in the wound bed during NPWT. Wounds were created over the femoral artery in the groin of 8 pigs. Rigid discs were inserted. Wound bed pressures and arterial blood flow were measured during NPWT. Pressure transduction to the wound bed was similar for control wounds and wounds with discs. Blood flow through the femoral artery decreased in control wounds. When a disc was inserted, the blood flow was restored. NPWT causes hypoperfusion in the wound bed tissue, presumably as a result of mechanical deformation. The insertion of a rigid barrier alleviates this effect and restores blood flow.

Green waste cooking oil-based rigid polyurethane foam

NASA Astrophysics Data System (ADS)

Enderus, N. F.; Tahir, S. M.

2017-11-01

Polyurethane is a versatile polymer traditionally prepared using petroleum-based raw material. Petroleum, however, is a non-renewable material and polyurethane produced was found to be non-biodegradable. In quest for a more environmentally friendly alternative, wastecooking oil, a highly abundant domestic waste with easily derivatized structure, is a viable candidate to replace petroleum. In this study,an investigation to determine physical and chemical properties of rigid polyurethane (PU) foam from waste cooking oil (WCO) was carried out. WCO was first adsorbed by using coconut husk activated carbon adsorbent prior to be used for polyol synthesis. The purified WCO was then used to synthesize polyol via transesterification reaction to yield alcohol groups in the WCO chains structure. Finally, the WCO-based polyol was used to prepare rigid PU foam. The optimum formulation for PU formation was found to be 90 polyol: 60 glycerol: 54 water: 40 diethanolamine: 23 diisocyanate. The rigid PU foam has density of 208.4 kg/m3 with maximum compressive strength and capability to receive load at 0.03 MPa and 0.09 kN, respectively. WCO-based PU can potentially be used to replace petroleum-based PU as house construction materials such as insulation panels.

The next generation of solar panel substrates?

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

Gledhill, K.M.; Boswell, R.L.; Paul, J.G.

For over 25 years, satellite power system designers have used rigid honeycomb panels as solar array substrates. Those years have seen very little improvement in the performance of these rigid systems. A new technology under development at the Phillips Laboratory, however, may undo this stagnancy. Composite isogrid panel structures offer a number of potential advantages over honeycomb sandwich structures for solar array applications, including stiffness, weight, and cost improvements. Phillips Laboratory will be performing a series of evaluative tests on the isogrid structure to determine its suitability as a substitute for honeycomb sandwiches in solar panel applications. Testing will includemore » three-point bending, thermal vacuum, and thermal cycling.« less

Porous carbonaceous electrode structure and method for secondary electrochemical cell

DOEpatents

Kaun, Thomas D.

1977-03-08

Positive and negative electrodes are provided as rigid, porous carbonaceous matrices with particulate active material fixedly embedded. Active material such as metal chalcogenides, solid alloys of alkali metal or alkaline earth metals along with other metals and their oxides in particulate form are blended with a thermosetting resin and a solid volatile to form a paste mixture. Various electrically conductive powders or current collector structures can be blended or embedded into the paste mixture which can be molded to the desired electrode shape. The molded paste is heated to a temperature at which the volatile transforms into vapor to impart porosity as the resin begins to cure into a rigid solid structure.

The Galileo Orbiter - Command and telemetry subsystems on their way to Jupiter

NASA Astrophysics Data System (ADS)

Erickson, James K.

1990-09-01

An overview is given of the Galileo command and telemetry subsystems, which exemplify the rigid time-synchronized systems required by TDM (time division multiplexing). The spacecraft clock is examined, along with some of the rationale for the development of the clock structure and timing to give a sense of the design imperatives for rigidly synchronized systems. Additional subjects include the structure of the science and engineering frames, emphasizing the subcommutated structure of the engineering frame and its relationship to the spacecraft clock; ground processing for and basic uses of the telemetry; the various message types used to transmit commands to the spacecraft; and the generation processes for the command message types.

How does symmetry impact the flexibility of proteins?

PubMed

Schulze, Bernd; Sljoka, Adnan; Whiteley, Walter

2014-02-13

It is well known that (i) the flexibility and rigidity of proteins are central to their function, (ii) a number of oligomers with several copies of individual protein chains assemble with symmetry in the native state and (iii) added symmetry sometimes leads to added flexibility in structures. We observe that the most common symmetry classes of protein oligomers are also the symmetry classes that lead to increased flexibility in certain three-dimensional structures-and investigate the possible significance of this coincidence. This builds on the well-developed theory of generic rigidity of body-bar frameworks, which permits an analysis of the rigidity and flexibility of molecular structures such as proteins via fast combinatorial algorithms. In particular, we outline some very simple counting rules and possible algorithmic extensions that allow us to predict continuous symmetry-preserving motions in body-bar frameworks that possess non-trivial point-group symmetry. For simplicity, we focus on dimers, which typically assemble with twofold rotational axes, and often have allosteric function that requires motions to link distant sites on the two protein chains.

Rotational Stiffness of Precast Beam-Column Connection using Finite Element Method

NASA Astrophysics Data System (ADS)

Hashim, N.; Agarwal, J.

2018-04-01

Current design practice in structural analysis is to assume the connection as pinned or rigid, however this cannot be relied upon for safety against collapse because during services the actual connection reacts differently where the connection has rotated in relevance. This situation may lead to different reactions and consequently affect design results and other frame responses. In precast concrete structures, connections play an important part in ensuring the safety of the whole structure. Thus, investigates on the actual connection behavior by construct the moment-rotation relationship is significant. Finite element (FE) method is chosen for modeling a 3-dimensional beam-column connection. The model is built in symmetry to reduce analysis time. Results demonstrate that precast billet connection is categorized as semi-rigid connection with Sini of 23,138kNm/rad. This is definitely different from the assumption of pinned or rigid connection used in design practice. Validation were made by comparing with mathematical equation and small differences were achieved that led to the conclusion where precast billet connection using FE method is acceptable.

Stable, Metastable, and Kinetically Trapped Amyloid Aggregate Phases

PubMed Central

2015-01-01

Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer’s disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid–liquid phase separation of proteins and to surfactant aggregation are discussed. PMID:25469942

Numerical analysis of the cylindrical rigidity of the vertical steel tank shell

NASA Astrophysics Data System (ADS)

Chirkov, Sergey; Tarasenko, Alexander; Chepur, Petr

2017-10-01

The paper deals with the study of rigidity of a vertical steel cylindrical tank and its structural elements with the development of inhomogeneous subsidence in ANSYS software complex. The limiting case is considered in this paper: a complete absence of a base sector that varies along an arc of a circle. The subsidence zone is modeled by the parameter n. A finite-element model of vertical 20000 m3 steel tank has been created, taking into account all structural elements of tank metal structures, including the support ring, beam frame and roof sheets. Various combinations of vertical steel tank loading are analyzed. For operational loads, the most unfavorable combination is considered. Calculations were performed for the filled and emptied tank. Values of the maximum possible deformations of the outer contour of the bottom are obtained with the development of inhomogeneous base subsidence for the given tank size. The obtained parameters of intrinsic rigidity (deformability) of vertical steel tank can be used in the development of new regulatory and technical documentation for tanks.

Stable, metastable, and kinetically trapped amyloid aggregate phases.

PubMed

Miti, Tatiana; Mulaj, Mentor; Schmit, Jeremy D; Muschol, Martin

2015-01-12

Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer's disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid-liquid phase separation of proteins and to surfactant aggregation are discussed.

A rigidity transition and glassy dynamics in a model for confluent 3D tissues

NASA Astrophysics Data System (ADS)

Merkel, Matthias; Manning, M. Lisa

The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Recently, a new type of rigidity transition was discovered in a family of models for 2D biological tissues, but the mechanisms responsible for rigidity remain unclear. This is not just a statistical physics problem, but also relevant for embryonic development, cancer growth, and wound healing. To gain insight into this rigidity transition and make new predictions about biological bulk tissues, we have developed a fully 3D self-propelled Voronoi (SPV) model. The model takes into account shape, elasticity, and self-propelled motion of the individual cells. We find that in the absence of self-propulsion, this model exhibits a rigidity transition that is controlled by a dimensionless model parameter describing the preferred cell shape, with an accompanying structural order parameter. In the presence of self-propulsion, the rigidity transition appears as a glass-like transition featuring caging and aging effects. Given the similarities between this transition and jamming in particulate solids, it is natural to ask if the two transitions are related. By comparing statistics of Voronoi geometries, we show the transitions are surprisingly close but demonstrably distinct. Furthermore, an index theorem used to identify topologically protected mechanical modes in jammed systems can be extended to these vertex-type models. In our model, residual stresses govern the transition and enter the index theorem in a different way compared to jammed particles, suggesting the origin of rigidity may be different between the two.

Grounding of space structures

NASA Astrophysics Data System (ADS)

Bosela, P. A.; Fertis, D. G.; Shaker, F. J.

1992-09-01

Space structures, such as the Space Station solar arrays, must be extremely light-weight, flexible structures. Accurate prediction of the natural frequencies and mode shapes is essential for determining the structural adequacy of components, and designing a controls system. The tension pre-load in the 'blanket' of photovoltaic solar collectors, and the free/free boundary conditions of a structure in space, causes serious reservations on the use of standard finite element techniques of solution. In particular, a phenomenon known as 'grounding', or false stiffening, of the stiffness matrix occurs during rigid body rotation. This paper examines the grounding phenomenon in detail. Numerous stiffness matrices developed by others are examined for rigid body rotation capability, and found lacking. A force imbalance inherent in the formulations examined is the likely cause of the grounding problem, suggesting the need for a directed force formulation.

Measurement of the inertial constants of a rigid or flexible structure of arbitrary share through a vibration test

NASA Technical Reports Server (NTRS)

Engrand, D.; Cortial, J.

1983-01-01

The inertial constants of an aircraft rocket, or of any other structure, are defined without materializing any rotating axis. The necessary equipment is very similar to that used normally for ground vibration tests. An elastic suspension is used to obtain the total natural modes corresponding to the motions of the structure as a solid. From the measurements of the generalized masses of these modes it is possible to compute the inertial constants: (1) center of inertia; (2) tensor of inertia; and (3) mass. When the structure is not strictly rigid a purification process, based on the mean square method makes it possible to rigidify it at the price of some approximations and a few more measurements. Eventual additional masses, that are not parts of the structure, can be taken into account.

Nonlinear model of a rotating hub-beams structure: Equations of motion

NASA Astrophysics Data System (ADS)

Warminski, Jerzy

2018-01-01

Dynamics of a rotating structure composed of a rigid hub and flexible beams is presented in the paper. A nonlinear model of a beam takes into account bending, extension and nonlinear curvature. The influence of geometric nonlinearity and nonconstant angular velocity on dynamics of the rotating structure is presented. The exact equations of motion and associated boundary conditions are derived on the basis of the Hamilton's principle. The simplification of the exact nonlinear mathematical model is proposed taking into account the second order approximation. The reduced partial differential equations of motion together with associated boundary conditions can be used to study natural or forced vibrations of a rotating structure considering constant or nonconstant angular speed of a rigid hub and an arbitrary number of flexible blades.

Substrate Stiffness Regulates the Development of Left-Right Asymmetry in Cell Orientation.

PubMed

Bao, Yuanye; Huang, Yaozhun; Lam, Miu Ling; Xu, Ting; Zhu, Ninghao; Guo, Zhaobin; Cui, Xin; Lam, Raymond H W; Chen, Ting-Hsuan

2016-07-20

Left-right (LR) asymmetry of tissue/organ structure is a morphological feature essential for many tissue functions. The ability to incorporate the LR formation in constructing tissue/organ replacement is important for recapturing the inherent tissue structure and functions. However, how LR asymmetry is formed remains largely underdetermined, which creates significant hurdles to reproduce and regulate the formation of LR asymmetry in an engineering context. Here, we report substrate rigidity functioning as an effective switch that turns on the development of LR asymmetry. Using micropatterned cell-adherent stripes on rigid substrates, we found that cells collectively oriented at a LR-biased angle relative to the stripe boundary. This LR asymmetry was initiated by a LR-biased migration of cells at stripe boundary, which later generated a velocity gradient propagating from stripe boundary to the center. After a series of cell translocations and rotations, ultimately, an LR-biased cell orientation within the micropatterned stripe was formed. Importantly, this initiation and propagation of LR asymmetry was observed only on rigid but not on soft substrates, suggesting that the LR asymmetry was regulated by rigid substrate probably through the organization of actin cytoskeleton. Together, we demonstrated substrate rigidity as a determinant factor that mediates the self-organizing LR asymmetry being unfolded from single cells to multicellular organization. More broadly, we anticipate that our findings would pave the way for rebuilding artificial tissue constructs with inherent LR asymmetry in the future.

Roof-crush strength improvement using rigid polyurethane foam

NASA Astrophysics Data System (ADS)

Lilley, K.; Mani, A.

1998-08-01

Recent bending tests show the effectiveness of rigid, polyurethane foam in improving the strength of automotive body structures. By using foam, it is possible to reduce pillar sections, and to reduce thicknesses or eliminate reinforcements inside the pillars, and thereby offset the mass increase due to the foam filling. Further tests showed that utilizing the foam filling in a B-pillar to reduce section size can save ~20 mm that could be utilized to add energy absorbing structures in order to meet the new interior head impact requirements specified by the federal motor vehicle safety standards (FMVSS) 201 Head Impact Protection upgrade.

Rocket/launcher structural dynamics

NASA Technical Reports Server (NTRS)

Ferragut, N. J.

1976-01-01

The equations of motion describing the interactions between a rocket and a launcher were derived using Lagrange's Equation. A rocket launching was simulated. The motions of both the rocket and the launcher can be considered in detail. The model contains flexible elements and rigid elements. The rigid elements (masses) were judiciously utilized to simplify the derivation of the equations. The advantages of simultaneous shoe release were illustrated. Also, the loading history of the interstage structure of a boosted configuration was determined. The equations shown in this analysis could be used as a design tool during the modification of old launchers and the design of new launchers.

On vibrational imperfection sensitivity of Augusti's model structure in the vicinity of a non-linear static state

NASA Technical Reports Server (NTRS)

Elishakoff, Isaac; Marcus, S.; Starnes, J. H., JR.

1998-01-01

In this paper we present a closed-form solution for vibrational imperfection sensitivity the effect of small imperfections on the vibrational frequencies of perturbed motion around the static equilibrium state of Augusti's model Structure (a rigid link, pinned at one end to a rigid foundation and supported at the other by a linear extensional spring that retains its horizontality, as the system deflects). We also treat a modified version of that model with attendant slightly different dynamics. It is demonstrated that the vibrational frequencies decreases as the initial imperfections increase.

Adhesive plasters

DOEpatents

Holcombe, Jr., Cressie E.; Swain, Ronald L.; Banker, John G.; Edwards, Charlene C.

1978-01-01

Adhesive plaster compositions are provided by treating particles of Y.sub.2 O.sub.3, Eu.sub.2 O.sub.3, Gd.sub.2 O.sub.3 or Nd.sub.2 O.sub.3 with dilute acid solutions. The resulting compositions have been found to spontaneously harden into rigid reticulated masses resembling plaster of Paris. Upon heating, the hardened material is decomposed into the oxide, yet retains the reticulated rigid structure.

A tetrapyridine ligand with a rigid tetrahedral core forms metal-organic frameworks with PtS type architecture.

PubMed

Caputo, Christopher B; Vukotic, V Nicholas; Sirizzotti, Natalie M; Loeb, Stephen J

2011-08-14

A new tetradentate, pyridine ligand with a rigid tetrahedral core can be prepared in good yield by a cross-coupling methodology. Two metal organic framework structures of Cu(II) with PtS-type topology having a carbon atom as the tetrahedral node have been characterized utilising this ligand. This journal is © The Royal Society of Chemistry 2011

Numerical Simulation of Dry Granular Flow Impacting a Rigid Wall Using the Discrete Element Method

PubMed Central

Wu, Fengyuan; Fan, Yunyun; Liang, Li; Wang, Chao

2016-01-01

This paper presents a clump model based on Discrete Element Method. The clump model was more close to the real particle than a spherical particle. Numerical simulations of several tests of dry granular flow impacting a rigid wall flowing in an inclined chute have been achieved. Five clump models with different sphericity have been used in the simulations. By comparing the simulation results with the experimental results of normal force on the rigid wall, a clump model with better sphericity was selected to complete the following numerical simulation analysis and discussion. The calculation results of normal force showed good agreement with the experimental results, which verify the effectiveness of the clump model. Then, total normal force and bending moment of the rigid wall and motion process of the granular flow were further analyzed. Finally, comparison analysis of the numerical simulations using the clump model with different grain composition was obtained. By observing normal force on the rigid wall and distribution of particle size at the front of the rigid wall at the final state, the effect of grain composition on the force of the rigid wall has been revealed. It mainly showed that, with the increase of the particle size, the peak force at the retaining wall also increase. The result can provide a basis for the research of relevant disaster and the design of protective structures. PMID:27513661

Enhanced enzyme kinetic stability by increasing rigidity within the active site.

PubMed

Xie, Yuan; An, Jiao; Yang, Guangyu; Wu, Geng; Zhang, Yong; Cui, Li; Feng, Yan

2014-03-14

Enzyme stability is an important issue for protein engineers. Understanding how rigidity in the active site affects protein kinetic stability will provide new insight into enzyme stabilization. In this study, we demonstrated enhanced kinetic stability of Candida antarctica lipase B (CalB) by mutating the structurally flexible residues within the active site. Six residues within 10 Å of the catalytic Ser(105) residue with a high B factor were selected for iterative saturation mutagenesis. After screening 2200 colonies, we obtained the D223G/L278M mutant, which exhibited a 13-fold increase in half-life at 48 °C and a 12 °C higher T50(15), the temperature at which enzyme activity is reduced to 50% after a 15-min heat treatment. Further characterization showed that global unfolding resistance against both thermal and chemical denaturation also improved. Analysis of the crystal structures of wild-type CalB and the D223G/L278M mutant revealed that the latter formed an extra main chain hydrogen bond network with seven structurally coupled residues within the flexible α10 helix that are primarily involved in forming the active site. Further investigation of the relative B factor profile and molecular dynamics simulation confirmed that the enhanced rigidity decreased fluctuation of the active site residues at high temperature. These results indicate that enhancing the rigidity of the flexible segment within the active site may provide an efficient method for improving enzyme kinetic stability.

Rigidity in routines and the development of resistance to change in individuals with Prader-Willi syndrome.

PubMed

Haig, E L; Woodcock, K A

2017-05-01

Individuals with Prader-Willi syndrome (PWS) commonly show debilitating resistance to change, which has been linked to cognitive deficits in task switching. Anecdotal reports suggest that exposure to flexibility in routines during development may be beneficial for limiting subsequent resistance to change in people with PWS, which is consistent with a beneficial role of such exposure on the development of task switching, highlighted in typical children. Here, we aim to investigate the development of resistance to change in individuals with PWS and hypothesise that exposure to increased rigidity in routines will be associated with increased subsequent resistance to change. An author-compiled informant report interview and two previously validated questionnaires were administered to the caregivers of 10 individuals with PWS (5-23 years). The interview examined rigidity in routines and resistance to change across life stages defined by easily distinguishable events (before school, during primary school, during secondary school, after school, currently), using open-ended and structured yes/no and 5-point Likert questions. Open-ended data were coded using an author-compiled system. Responses from two additional informants and data from the questionnaires were used to assess inter-informant reliability and concurrent validity of the structured questions. The validity of the interview was supported by acceptable inter-rater reliability of the open-ended coding system and inter-informant reliability, internal consistency and concurrent validity of structured questions. Descriptive analyses of ratings of behaviour change showed a pattern of increasing resistance to change over the life course for the four oldest individuals, who had all been exposed to substantial rigidity in routines before and during primary school. Furthermore, only one individual - currently in primary school - was exposed to very little rigidity in routines before and during primary school, and he had showed a decrease in resistance to change after entering primary school. Open-ended data showed that more individuals currently evidencing little resistance to change had been exposed to parent or self-imposed flexibility in routines, than those currently evidencing substantial resistance to change. However, correlational analyses on rigidity and resistance to change ratings highlighted the possibility that rigidity during primary school is most relevant for developing resistance to change. Finally, open-ended data emphasised an important beneficial role of rigidity in routines for limiting the current challenging behaviour of individuals with high resistance to change. Because task switching appears to evidence a period of high developmental sensitivity during early primary school years, we propose that this period may represent a critical time when increasing flexibility in the routines of children with PWS could limit the development of resistance to change. However, a careful balance would need to be struck, given the apparent benefit of rigid routines on current behaviour. Further work in this area is much needed. © 2017 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd.

Compression-bending of multi-component semi-rigid columns in response to axial loads and conjugate reciprocal extension-prediction of mechanical behaviours and implications for structural design.

PubMed

Lau, Ernest W

2013-01-01

The mathematical modelling of column buckling or beam bending under an axial or transverse load is well established. However, the existent models generally assume a high degree of symmetry in the structure of the column and minor longitudinal and transverse displacements. The situation when the column is made of several components with different mechanical properties asymmetrically distributed in the transverse section, semi-rigid, and subjected to multiple axial loads with significant longitudinal and transverse displacements through compression and bending has not been well characterised. A more comprehensive theoretical model allowing for these possibilities and assuming a circular arc contour for the bend is developed, and used to establish the bending axes, balance between compression and bending, and equivalent stiffness of the column. In certain situations, such as with pull cable catheters commonly used for minimally invasive surgical procedures, the compression loads are applied via cables running through channels inside a semi-rigid column. The model predicts the mathematical relationships between the radius of curvature of the bend and the tension in and normal force exerted by such cables. Conjugate extension with reciprocal compression-bending is a special structural arrangement for a semi-rigid column such that extension of one segment is linked to compression-bending of another by inextensible cables running between them. Leads are cords containing insulated electrical conductor coil and cables between the heart muscle and cardiac implantable electronic devices. Leads can behave like pull cable catheters through differential component pulling, providing a possible mechanism for inside-out abrasion and conductor cable externalisation. Certain design features may predispose to this mode of structural failure. Copyright © 2012 Elsevier Ltd. All rights reserved.

Computer program for determining mass properties of a rigid structure

NASA Technical Reports Server (NTRS)

Hull, R. A.; Gilbert, J. L.; Klich, P. J.

1978-01-01

A computer program was developed for the rapid computation of the mass properties of complex structural systems. The program uses rigid body analyses and permits differences in structural material throughout the total system. It is based on the premise that complex systems can be adequately described by a combination of basic elemental shapes. Simple geometric data describing size and location of each element and the respective material density or weight of each element were the only required input data. From this minimum input, the program yields system weight, center of gravity, moments of inertia and products of inertia with respect to mutually perpendicular axes through the system center of gravity. The program also yields mass properties of the individual shapes relative to component axes.

Small-Angle X-Ray Scattering Analysis of the Bifunctional Antibiotic Resistance Enzyme Aminoglycoside (6′) Acetyltransferase-Ie/Aminoglycoside (2″) Phosphotransferase-Ia Reveals a Rigid Solution Structure

PubMed Central

Caldwell, Shane J.

2012-01-01

Aminoglycoside (6′) acetyltransferase-Ie/aminoglycoside (2″) phosphotransferase-Ia [AAC(6′)-Ie/APH(2″)-Ia] is one of the most problematic aminoglycoside resistance factors in clinical pathogens, conferring resistance to almost every aminoglycoside antibiotic available to modern medicine. Despite 3 decades of research, our understanding of the structure of this bifunctional enzyme remains limited. We used small-angle X-ray scattering (SAXS) to model the structure of this bifunctional enzyme in solution and to study the impact of substrate binding on the enzyme. It was observed that the enzyme adopts a rigid conformation in solution, where the N-terminal AAC domain is fixed to the C-terminal APH domain and not loosely tethered. The addition of acetyl-coenzyme A, coenzyme A, GDP, guanosine 5′-[β,γ-imido]triphosphate (GMPPNP), and combinations thereof to the protein resulted in only modest changes to the radius of gyration (RG) of the enzyme, which were not consistent with any large changes in enzyme structure upon binding. These results imply some selective advantage to the bifunctional enzyme beyond coexpression as a single polypeptide, likely linked to an improvement in enzymatic properties. We propose that the rigid structure contributes to improved electrostatic steering of aminoglycoside substrates toward the two active sites, which may provide such an advantage. PMID:22290965

CNA web server: rigidity theory-based thermal unfolding simulations of proteins for linking structure, (thermo-)stability, and function.

PubMed

Krüger, Dennis M; Rathi, Prakash Chandra; Pfleger, Christopher; Gohlke, Holger

2013-07-01

The Constraint Network Analysis (CNA) web server provides a user-friendly interface to the CNA approach developed in our laboratory for linking results from rigidity analyses to biologically relevant characteristics of a biomolecular structure. The CNA web server provides a refined modeling of thermal unfolding simulations that considers the temperature dependence of hydrophobic tethers and computes a set of global and local indices for quantifying biomacromolecular stability. From the global indices, phase transition points are identified where the structure switches from a rigid to a floppy state; these phase transition points can be related to a protein's (thermo-)stability. Structural weak spots (unfolding nuclei) are automatically identified, too; this knowledge can be exploited in data-driven protein engineering. The local indices are useful in linking flexibility and function and to understand the impact of ligand binding on protein flexibility. The CNA web server robustly handles small-molecule ligands in general. To overcome issues of sensitivity with respect to the input structure, the CNA web server allows performing two ensemble-based variants of thermal unfolding simulations. The web server output is provided as raw data, plots and/or Jmol representations. The CNA web server, accessible at http://cpclab.uni-duesseldorf.de/cna or http://www.cnanalysis.de, is free and open to all users with no login requirement.

InterEvDock: a docking server to predict the structure of protein–protein interactions using evolutionary information

PubMed Central

Yu, Jinchao; Vavrusa, Marek; Andreani, Jessica; Rey, Julien; Tufféry, Pierre; Guerois, Raphaël

2016-01-01

The structural modeling of protein–protein interactions is key in understanding how cell machineries cross-talk with each other. Molecular docking simulations provide efficient means to explore how two unbound protein structures interact. InterEvDock is a server for protein docking based on a free rigid-body docking strategy. A systematic rigid-body docking search is performed using the FRODOCK program and the resulting models are re-scored with InterEvScore and SOAP-PP statistical potentials. The InterEvScore potential was specifically designed to integrate co-evolutionary information in the docking process. InterEvDock server is thus particularly well suited in case homologous sequences are available for both binding partners. The server returns 10 structures of the most likely consensus models together with 10 predicted residues most likely involved in the interface. In 91% of all complexes tested in the benchmark, at least one residue out of the 10 predicted is involved in the interface, providing useful guidelines for mutagenesis. InterEvDock is able to identify a correct model among the top10 models for 49% of the rigid-body cases with evolutionary information, making it a unique and efficient tool to explore structural interactomes under an evolutionary perspective. The InterEvDock web interface is available at http://bioserv.rpbs.univ-paris-diderot.fr/services/InterEvDock/. PMID:27131368

CNA web server: rigidity theory-based thermal unfolding simulations of proteins for linking structure, (thermo-)stability, and function

PubMed Central

Krüger, Dennis M.; Rathi, Prakash Chandra; Pfleger, Christopher; Gohlke, Holger

2013-01-01

The Constraint Network Analysis (CNA) web server provides a user-friendly interface to the CNA approach developed in our laboratory for linking results from rigidity analyses to biologically relevant characteristics of a biomolecular structure. The CNA web server provides a refined modeling of thermal unfolding simulations that considers the temperature dependence of hydrophobic tethers and computes a set of global and local indices for quantifying biomacromolecular stability. From the global indices, phase transition points are identified where the structure switches from a rigid to a floppy state; these phase transition points can be related to a protein’s (thermo-)stability. Structural weak spots (unfolding nuclei) are automatically identified, too; this knowledge can be exploited in data-driven protein engineering. The local indices are useful in linking flexibility and function and to understand the impact of ligand binding on protein flexibility. The CNA web server robustly handles small-molecule ligands in general. To overcome issues of sensitivity with respect to the input structure, the CNA web server allows performing two ensemble-based variants of thermal unfolding simulations. The web server output is provided as raw data, plots and/or Jmol representations. The CNA web server, accessible at http://cpclab.uni-duesseldorf.de/cna or http://www.cnanalysis.de, is free and open to all users with no login requirement. PMID:23609541

Molecular dynamics study of the structural and dynamic characteristics of the polyextremophilic short-chain dehydrogenase from the Thermococcus sibiricus archaeon and its homologues

NASA Astrophysics Data System (ADS)

Popinako, Anna V.; Antonov, Mikhail Yu.; Bezsudnova, Ekaterina Yu.; Prokopiev, Georgiy A.; Popov, Vladimir O.

2017-11-01

The study of structural adaptations of proteins from polyextremophilic organisms using computational molecular dynamics method is appealing because the obtained knowledge can be applied to construction of synthetic proteins with high activity and stability in polyextreme media which is useful for many industrial applications. To investigate molecular adaptations to high temperature, we have focused on a superthermostable short-chain dehydrogenase TsAdh319 from the Thermococcus sibiricus polyextremophilic archaeon and its closest structural homologues. Molecular dynamics method is widely used for molecular structure refinement, investigation of biological macromolecules motion, and, consequently, for interpreting the results of certain biophysical experiments. We performed molecular dynamics simulations of the proteins at different temperatures. Comparison of root mean square fluctuations (RMSF) of the atoms in thermophilic alcohol dehydrogenases (ADHs) at 300 K and 358 K revealed the existence of stable residues at 358 K. These residues surround the active site and form a "nucleus of rigidity" in thermophilic ADHs. The results of our studies suggest that the existence of the "nucleus of rigidity" is crucial for the stability of TsAdh319. Absence of the "nucleus of rigidity" in non-thermally stable proteins causes fluctuations throughout the protein, especially on the surface, triggering the process of denaturation at high temperatures.

Hydrodynamic impact of a system with a single elastic mode I : theory and generalized solution with an application to an elastic airframe

NASA Technical Reports Server (NTRS)

Mayo, Wilbur L

1952-01-01

Solutions of impact of a rigid prismatic float connected by a massless spring to a rigid upper mass are presented. The solutions are based on hydrodynamic theory which has been experimentally confirmed for a rigid structure. Equations are given for defining the spring constant and the ratio of the sprung mass to the lower mass so that the two-mass system provides representation of the fundamental mode of an airplane wing. The forces calculated are more accurate than the forces which would be predicted for a rigid airframe since the effect of the fundamental mode on the hydrodynamic force is taken into account. In a comparison of the theoretical data with data for a severe flight-test landing impact, the effect of the fundamental mode on the hydrodynamic force is considered and response data are compared with experimental data.

Structural changes of homodimers in the PDB.

PubMed

Koike, Ryotaro; Amemiya, Takayuki; Horii, Tatsuya; Ota, Motonori

2018-04-01

Protein complexes are involved in various biological phenomena. These complexes are intrinsically flexible, and structural changes are essential to their functions. To perform a large-scale automated analysis of the structural changes of complexes, we combined two original methods. An application, SCPC, compares two structures of protein complexes and decides the match of binding mode. Another application, Motion Tree, identifies rigid-body motions in various sizes and magnitude from the two structural complexes with the same binding mode. This approach was applied to all available homodimers in the Protein Data Bank (PDB). We defined two complex-specific motions: interface motion and subunit-spanning motion. In the former, each subunit of a complex constitutes a rigid body, and the relative movement between subunits occurs at the interface. In the latter, structural parts from distinct subunits constitute a rigid body, providing the relative movement spanning subunits. All structural changes were classified and examined. It was revealed that the complex-specific motions were common in the homodimers, detected in around 40% of families. The dimeric interfaces were likely to be small and flat for interface motion, while large and rugged for subunit-spanning motion. Interface motion was accompanied by a drastic change in contacts at the interface, while the change in the subunit-spanning motion was moderate. These results indicate that the interface properties of homodimers correlated with the type of complex-specific motion. The study demonstrates that the pipeline of SCPC and Motion Tree is useful for the massive analysis of structural change of protein complexes. Copyright © 2017 Elsevier Inc. All rights reserved.

Inclusion of Structural Flexibility in Design Load Analysis for Wave Energy Converters: Preprint

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

Guo, Yi; Yu, Yi-Hsiang; van Rij, Jennifer A

2017-08-14

Hydroelastic interactions, caused by ocean wave loading on wave energy devices with deformable structures, are studied in the time domain. A midfidelity, hybrid modeling approach of rigid-body and flexible-body dynamics is developed and implemented in an open-source simulation tool for wave energy converters (WEC-Sim) to simulate the dynamic responses of wave energy converter component structural deformations under wave loading. A generalized coordinate system, including degrees of freedom associated with rigid bodies, structural modes, and constraints connecting multiple bodies, is utilized. A simplified method of calculating stress loads and sectional bending moments is implemented, with the purpose of sizing and designingmore » wave energy converters. Results calculated using the method presented are verified with those of high-fidelity fluid-structure interaction simulations, as well as low-fidelity, frequency-domain, boundary element method analysis.« less

Load concentration due to missing members in planar faces of a large space truss

NASA Technical Reports Server (NTRS)

Waltz, J. E.

1979-01-01

A large space structure with members missing was investigated using a finite element analysis. The particular structural configuration was the tetrahedral truss, with attention restricted to one of its planar faces. Initially the finite element model of a complete face was verified by comparing it with known results for some basic loadings. Then an analysis was made of the structure with members near the center removed. Some calculations were made on the influence of the mesh size of a structure containing a hexagonal hole, and an analysis was also made of a structure with a rigid hexagonal insert. In general, load concentration effects in these trusses were significantly lower than classical stress concentration effects in an infinitely wide isotropic plate with a circular rigid inclusion, although larger effects were obtained when a hole extended over several rings of elements.

Method and apparatus for minimizing multiple degree of freedom vibration transmission between two regions of a structure

NASA Technical Reports Server (NTRS)

Silcox, Richard J. (Inventor); Fuller, Chris R. (Inventor); Gibbs, Gary P. (Inventor)

1992-01-01

Arrays of actuators are affixed to structural elements to impede the transmission of vibrational energy. A single pair is used to provide control of bending and extensional waves and two pairs are used to control torsional motion. The arrays are applied to a wide variety of structural elements such as a beam structure that is part of a larger framework that may or may not support a rigid or non-rigid skin. Electrical excitation is applied to the actuators that generate forces on the structure. These electrical inputs may be adjusted in their amplitude and phase by a controller in communication with appropriate vibrational wave sensors to impede the flow of vibrational power in all of the above mentioned wave forms beyond the actuator location. Additional sensor elements can be used to monitor the performance and adjust the electrical inputs to maximize the attenuation of vibrational energy.

Effects of semi-rigid arch-support orthotics: an investigation with potential ergonomic implications.

PubMed

Kelaher, D; Mirka, G A; Dudziak, K Q

2000-10-01

For many years, arch-support orthotics have been prescribed for individuals with discomfort and/or abnormal skeletal alignments in the structures of the lower extremity. Recently there has been an increased interest in promoting semi-rigid orthotics as an ergonomic aid for asymptomatic workers who must stand all day at their workplace. A laboratory study was performed to assess the biomechanical impact of prefabricated semi-rigid orthotics on asymptomatic individuals. Ten subjects wore semi-rigid arch-support orthotics (experimental condition) for two months and flexible polyurethane/Sorbothane shoe inserts (control condition) for two months. Throughout this 18-week testing period, the subjects returned to the lab to perform a battery of assessment tests at regularly scheduled intervals. These tests examined subject strength, standing posture, stability, fatigue effects, and body part discomfort. The results of this study showed no significant changes in the strength, posture, or stability as a function of insert type. The subjects reported a reduction in low-back discomfort along with an increase in foot discomfort during a fatiguing exertion task while wearing the semi-rigid orthotics as compared to the control condition.

The Delicate Balance of Preorganisation and Adaptability in Multiply Bonded Host-Guest Complexes.

PubMed

von Krbek, Larissa K S; Achazi, Andreas J; Schoder, Stefan; Gaedke, Marius; Biberger, Tobias; Paulus, Beate; Schalley, Christoph A

2017-02-24

Rigidity and preorganisation are believed to be required for high affinity in multiply bonded supramolecular complexes as they help reduce the entropic penalty of the binding event. This comes at the price that such rigid complexes are sensitive to small geometric mismatches. In marked contrast, nature uses more flexible building blocks. Thus, one might consider putting the rigidity/high-affinity notion to the test. Multivalent crown/ammonium complexes are ideal for this purpose as the monovalent interaction is well understood. A series of divalent complexes with different spacer lengths and rigidities has thus been analysed to correlate chelate cooperativities and spacer properties. Too long spacers reduce chelate cooperativity compared to exactly matching ones. However, in contrast to expectation, flexible guests bind with chelate cooperativities clearly exceeding those of rigid structures. Flexible spacers adapt to small geometric host-guest mismatches. Spacer-spacer interactions help overcome the entropic penalty of conformational fixation during binding and a delicate balance of preorganisation and adaptability is at play in multivalent complexes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The influence of foot orthoses on foot mobility magnitude and arch height index in adults with flexible flat feet.

PubMed

Sheykhi-Dolagh, Roghaye; Saeedi, Hassan; Farahmand, Behshid; Kamyab, Mojtaba; Kamali, Mohammad; Gholizadeh, Hossein; Derayatifar, Amir A; Curran, Sarah

2015-06-01

Flexible flat foot is described as a reduction in the height of the medial longitudinal arch and may occur from abnormal foot pronation. A foot orthosis is thought to modify and control excessive pronation and improve arch height. To compare the immediate effect of three types of orthoses on foot mobility and the arch height index in subjects with flexible flat feet. A quasi-experimental study. The dorsal arch height, midfoot width, foot mobility and arch height index were assessed in 20 participants with flexible flat feet (mean age = 23.2 ± 3 years) for three different foot orthosis conditions: soft, semi-rigid and rigid University of California Biomechanics Laboratory (UCBL). Maximum midfoot width at 90% with arch mobility in the coronal plane was shown in the semi-rigid orthosis condition. The semi-rigid orthosis resulted in the highest mean foot mobility in 90% of weight bearing, and the rigid orthosis (UCBL) had the lowest mean foot mobility. The soft orthosis resulted in foot mobility between that of the rigid and the semi-rigid orthosis. UCBL orthosis showed the highest arch height index, and the semi-rigid orthosis showed the lowest mean arch height index. Due to its rigid structure and long medial-lateral walls, the UCBL orthosis appears to limit foot mobility. Therefore, it is necessary to make an orthosis that facilitates foot mobility in the normal range of the foot arch. Future studies should address the dynamic mobility of the foot with using various types of foot orthoses. Although there are many studies focussed on flat foot and the use of foot orthoses, the mechanism of action is still unclear. This study explored foot mobility and the influence of foot orthoses and showed that a more rigid foot orthosis should be selected based on foot mobility. © The International Society for Prosthetics and Orthotics 2014.

Passive Earth Entry Vehicle Landing Test

NASA Technical Reports Server (NTRS)

Kellas, Sotiris

2017-01-01

Two full-scale passive Earth Entry Vehicles (EEV) with realistic structure, surrogate sample container, and surrogate Thermal Protection System (TPS) were built at NASA Langley Research Center (LaRC) and tested at the Utah Test and Training Range (UTTR). The main test objective was to demonstrate structural integrity and investigate possible impact response deviations of the realistic vehicle as compared to rigid penetrometer responses. With the exception of the surrogate TPS and minor structural differences in the back shell construction, the two test vehicles were identical in geometry and both utilized the Integrated Composite Stiffener Structure (ICoSS) structural concept in the forward shell. The ICoSS concept is a lightweight and highly adaptable composite concept developed at NASA LaRC specifically for entry vehicle TPS carrier structures. The instrumented test vehicles were released from a helicopter approximately 400 m above ground. The drop height was selected such that at least 98% of the vehicles terminal velocity would be achieved. While drop tests of spherical penetrometers and a low fidelity aerodynamic EEV model were conducted at UTTR in 1998 and 2000, this was the first time a passive EEV with flight-like structure, surrogate TPS, and sample container was tested at UTTR for the purpose of complete structural system validation. Test results showed that at a landing vertical speed of approximately 30 m/s, the test vehicle maintained structural integrity and enough rigidity to penetrate the sandy clay surface thus attenuating the landing load, as measured at the vehicle CG, to less than 600 g. This measured deceleration was found to be in family with rigid penetrometer test data from the 1998 and 2000 test campaigns. Design implications of vehicle structure/soil interaction with respect to sample container and sample survivability are briefly discussed.

Simulations of dynamics of plunge and pitch of a three-dimensional flexible wing in a low Reynolds number flow

NASA Astrophysics Data System (ADS)

Qi, Dewei; Liu, Yingming; Shyy, Wei; Aono, Hikaru

2010-09-01

The lattice Boltzmann flexible particle method (LBFPM) is used to simulate fluid-structure interaction and motion of a flexible wing in a three-dimensional space. In the method, a beam with rectangular cross section has been discretized into a chain of rigid segments. The segments are connected through ball and socket joints at their ends and may be bent and twisted. Deformation of flexible structure is treated with a linear elasticity model through bending and twisting. It is demonstrated that the flexible particle method (FPM) can approximate the nonlinear Euler-Bernoulli beam equation without resorting to a nonlinear elasticity model. Simulations of plunge and pitch of flexible wing at Reynolds number Re=136 are conducted in hovering condition by using the LBFPM. It is found that both lift and drag forces increase first, then decrease dramatically as the bending rigidity in spanwise direction decreases and that the lift and drag forces are sensitive to rigidity in a certain range. It is shown that the downwash flows induced by wing tip and trailing vortices in wake area are larger for a flexible wing than for a rigid wing, lead to a smaller effective angle of attack, and result in a larger lift force.

Spirocyclic systems derived from pyroglutamic acid.

PubMed

Cowley, Andrew R; Hill, Thomas J; Kocis, Petr; Moloney, Mark G; Stevenson, Robert D; Thompson, Amber L

2011-10-21

The synthesis and likely conformational structure of rigid spirocyclic bislactams and lactam-lactones derived from pyroglutamic acid, and their suitability as lead structures for applications in drug development programmes using cheminformatic analysis, has been investgated.

Structure-Based Druggability Assessment of the Mammalian Structural Proteome with Inclusion of Light Protein Flexibility

PubMed Central

Loving, Kathryn A.; Lin, Andy; Cheng, Alan C.

2014-01-01

Advances reported over the last few years and the increasing availability of protein crystal structure data have greatly improved structure-based druggability approaches. However, in practice, nearly all druggability estimation methods are applied to protein crystal structures as rigid proteins, with protein flexibility often not directly addressed. The inclusion of protein flexibility is important in correctly identifying the druggability of pockets that would be missed by methods based solely on the rigid crystal structure. These include cryptic pockets and flexible pockets often found at protein-protein interaction interfaces. Here, we apply an approach that uses protein modeling in concert with druggability estimation to account for light protein backbone movement and protein side-chain flexibility in protein binding sites. We assess the advantages and limitations of this approach on widely-used protein druggability sets. Applying the approach to all mammalian protein crystal structures in the PDB results in identification of 69 proteins with potential druggable cryptic pockets. PMID:25079060

Local structure and structural rigidity of the green phosphor β -SiAlON:Eu 2+

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

Brgoch, J.; Gaultois, M. W.; Balasubramanian, M.

Eu2+ inserted in beta-Si3-xAlxOxN4-x is a material that shows exceptional promise as a green-emitting phosphor. Synchrotron X-ray and neutron scattering, in conjunction with first-principles calculations and Eu L-3 X-ray absorption measurements, yield a consistent picture of the composition, and the favorable position for Eu2+ substitution in the crystal structure. The Debye temperature Theta(D), which is a proxy for structural rigidity relating to effectiveness as a phosphor, is very high for the starting beta-Si3N4 framework and is determined to decrease only slightly for the small amounts of Al3+ and O2- co-substitution that are required for charge balance associated with Eu2+ insertion.more » (C) 2014 AIP Publishing LLC.« less

Plane stress problems using hysteretic rigid body spring network models

NASA Astrophysics Data System (ADS)

Christos, Sofianos D.; Vlasis, Koumousis K.

2017-10-01

In this work, a discrete numerical scheme is presented capable of modeling the hysteretic behavior of 2D structures. Rigid Body Spring Network (RBSN) models that were first proposed by Kawai (Nucl Eng Des 48(1):29-207, 1978) are extended to account for hysteretic elastoplastic behavior. Discretization is based on Voronoi tessellation, as proposed specifically for RBSN models to ensure uniformity. As a result, the structure is discretized into convex polygons that form the discrete rigid bodies of the model. These are connected with three zero length, i.e., single-node springs in the middle of their common facets. The springs follow the smooth hysteretic Bouc-Wen model which efficiently incorporates classical plasticity with no direct reference to a yield surface. Numerical results for both static and dynamic loadings are presented, which validate the proposed simplified spring-mass formulation. In addition, they verify the model's applicability on determining primarily the displacement field and plastic zones compared to the standard elastoplastic finite element method.

Control superstructure of rigid polyelectrolytes in oppositely charged hydrogels via programmed internal stress

NASA Astrophysics Data System (ADS)

Takahashi, Riku; Wu, Zi Liang; Arifuzzaman, Md; Nonoyama, Takayuki; Nakajima, Tasuku; Kurokawa, Takayuki; Gong, Jian Ping

2014-08-01

Biomacromolecules usually form complex superstructures in natural biotissues, such as different alignments of collagen fibres in articular cartilages, for multifunctionalities. Inspired by nature, there are efforts towards developing multiscale ordered structures in hydrogels (recognized as one of the best candidates of soft biotissues). However, creating complex superstructures in gels are hardly realized because of the absence of effective approaches to control the localized molecular orientation. Here we introduce a method to create various superstructures of rigid polyanions in polycationic hydrogels. The control of localized orientation of rigid molecules, which are sensitive to the internal stress field of the gel, is achieved by tuning the swelling mismatch between masked and unmasked regions of the photolithographic patterned gel. Furthermore, we develop a double network structure to toughen the hydrogels with programmed superstructures, which deform reversibly under large strain. This work presents a promising pathway to develop superstructures in hydrogels and should shed light on designing biomimetic materials with intricate molecular alignments.

Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station

NASA Astrophysics Data System (ADS)

Aguilar, M.; Ali Cavasonza, L.; Ambrosi, G.; Arruda, L.; Attig, N.; Aupetit, S.; Azzarello, P.; Bachlechner, A.; Barao, F.; Barrau, A.; Barrin, L.; Bartoloni, A.; Basara, L.; Başeǧmez-du Pree, S.; Battarbee, M.; Battiston, R.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo, J.; Bertucci, B.; Bindel, K. F.; Bindi, V.; Boella, G.; de Boer, W.; Bollweg, K.; Bonnivard, V.; Borgia, B.; Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Cadoux, F.; Cai, X. D.; Capell, M.; Caroff, S.; Casaus, J.; Castellini, G.; Cervelli, F.; Chae, M. J.; Chang, Y. H.; Chen, A. I.; Chen, G. M.; Chen, H. S.; Cheng, L.; Chou, H. Y.; Choumilov, E.; Choutko, V.; Chung, C. H.; Clark, C.; Clavero, R.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Creus, W.; Crispoltoni, M.; Cui, Z.; Dai, Y. M.; Delgado, C.; Della Torre, S.; Demakov, O.; Demirköz, M. B.; Derome, L.; Di Falco, S.; Dimiccoli, F.; Díaz, C.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.; D'Urso, D.; Egorov, A.; Eline, A.; Eronen, T.; Feng, J.; Fiandrini, E.; Finch, E.; Fisher, P.; Formato, V.; Galaktionov, Y.; Gallucci, G.; García, B.; García-López, R. J.; Gargiulo, C.; Gast, H.; Gebauer, I.; Gervasi, M.; Ghelfi, A.; Giovacchini, F.; Goglov, P.; Gómez-Coral, D. M.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Guo, K. H.; Haino, S.; Han, K. C.; He, Z. H.; Heil, M.; Hoffman, J.; Hsieh, T. H.; Huang, H.; Huang, Z. C.; Huh, C.; Incagli, M.; Ionica, M.; Jang, W. Y.; Jinchi, H.; Kang, S. C.; Kanishev, K.; Kim, G. N.; Kim, K. S.; Kirn, Th.; Konak, C.; Kounina, O.; Kounine, A.; Koutsenko, V.; Krafczyk, M. S.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.; Leluc, C.; Li, H. S.; Li, J. Q.; Li, J. Q.; Li, Q.; Li, T. X.; Li, W.; Li, Y.; Li, Z. H.; Li, Z. Y.; Lim, S.; Lin, C. H.; Lipari, P.; Lippert, T.; Liu, D.; Liu, Hu; Lordello, V. D.; Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, F.; Luo, J. Z.; Lv, S. S.; Machate, F.; Majka, R.; Mañá, C.; Marín, J.; Martin, T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng, Q.; Mikuni, V. M.; Mo, D. C.; Morescalchi, L.; Mott, P.; Nelson, T.; Ni, J. Q.; Nikonov, N.; Nozzoli, F.; Oliva, A.; Orcinha, M.; Palmonari, F.; Palomares, C.; Paniccia, M.; Pauluzzi, M.; Pensotti, S.; Pereira, R.; Picot-Clemente, N.; Pilo, F.; Pizzolotto, C.; Plyaskin, V.; Pohl, M.; Poireau, V.; Putze, A.; Quadrani, L.; Qi, X. M.; Qin, X.; Qu, Z. Y.; Räihä, T.; Rancoita, P. G.; Rapin, D.; Ricol, J. S.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Sandweiss, J.; Saouter, P.; Schael, S.; Schmidt, S. M.; Schulz von Dratzig, A.; Schwering, G.; Seo, E. S.; Shan, B. S.; Shi, J. Y.; Siedenburg, T.; Son, D.; Song, J. W.; Sun, W. H.; Tacconi, M.; Tang, X. W.; Tang, Z. C.; Tao, L.; Tescaro, D.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Türkoǧlu, C.; Urban, T.; Vagelli, V.; Valente, E.; Vannini, C.; Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Vitale, V.; Vitillo, S.; Wang, L. Q.; Wang, N. H.; Wang, Q. L.; Wang, X.; Wang, X. Q.; Wang, Z. X.; Wei, C. C.; Weng, Z. L.; Whitman, K.; Wienkenhöver, J.; Wu, H.; Wu, X.; Xia, X.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, J.; Yang, M.; Yang, Y.; Yi, H.; Yu, Y. J.; Yu, Z. Q.; Zeissler, S.; Zhang, C.; Zhang, J.; Zhang, J. H.; Zhang, S. D.; Zhang, S. W.; Zhang, Z.; Zheng, Z. M.; Zhu, Z. Q.; Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann, N.; Zuccon, P.; AMS Collaboration

2016-12-01

Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the B /C ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the B /C spectral index is reported for the first time. The B /C ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the B /C ratio is well described by a single power law RΔ with index Δ =-0.333 ±0.014 (fit ) ±0.005 (syst ) , in good agreement with the Kolmogorov theory of turbulence which predicts Δ =-1 /3 asymptotically.

14 CFR 25.629 - Aeroelastic stability requirements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... weights are used, their effectiveness and strength, including supporting structure, must be substantiated... of any single element of the structure supporting any engine, independently mounted propeller shaft... dynamic forces, any single failure of the engine structure that would reduce the rigidity of the...

14 CFR 25.629 - Aeroelastic stability requirements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... weights are used, their effectiveness and strength, including supporting structure, must be substantiated... of any single element of the structure supporting any engine, independently mounted propeller shaft... dynamic forces, any single failure of the engine structure that would reduce the rigidity of the...

14 CFR 25.629 - Aeroelastic stability requirements.

Code of Federal Regulations, 2011 CFR

2011-01-01

... weights are used, their effectiveness and strength, including supporting structure, must be substantiated... of any single element of the structure supporting any engine, independently mounted propeller shaft... dynamic forces, any single failure of the engine structure that would reduce the rigidity of the...

14 CFR 25.629 - Aeroelastic stability requirements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... weights are used, their effectiveness and strength, including supporting structure, must be substantiated... of any single element of the structure supporting any engine, independently mounted propeller shaft... dynamic forces, any single failure of the engine structure that would reduce the rigidity of the...

Interpersonal Dynamics and Organizational Change in Religious Communities.

ERIC Educational Resources Information Center

Barber, William H.; Rock, Leo P.

This paper discusses the organizational structure of religious communities and its effect on interpersonal relations. Religious communities tend to be organized structurally according to the traditional bureaucratic model of (1) relatively rigid structure; (2) carefully defined functional specialization; (3) direction and control implemented…

NASTRAN analysis of Tokamak vacuum vessel using interactive graphics

NASA Technical Reports Server (NTRS)

Miller, A.; Badrian, M.

1978-01-01

Isoparametric quadrilateral and triangular elements were used to represent the vacuum vessel shell structure. For toroidally symmetric loadings, MPCs were employed across model boundaries and rigid format 24 was invoked. Nonsymmetric loadings required the use of the cyclic symmetry analysis available with rigid format 49. NASTRAN served as an important analysis tool in the Tokamak design effort by providing a reliable means for assessing structural integrity. Interactive graphics were employed in the finite element model generation and in the post-processing of results. It was felt that model generation and checkout with interactive graphics reduced the modelling effort and debugging man-hours significantly.

Zinc oxide films chemically grown onto rigid and flexible substrates for TFT applications

NASA Astrophysics Data System (ADS)

Suchea, M.; Kornilios, N.; Koudoumas, E.

2010-10-01

This contribution presents some preliminary results regarding the use of a chemical route for the growth of good quality ZnO thin films that can be used for the fabrication of thin film transistors (TFTs). The films were grown at rather low temperature (60 °C) on glass and PET substrates using non-aqueous (zinc acetate dihydrate in methanol) precursor solution and their surface morphology, crystalline structure, optical transmittance and electrical characteristics were studied. The study indicated that good quality films with desirable ZnO structure onto rigid and flexible substrates can be obtained, using a simple, cheap, low temperature chemical growth method.

Domino structures evolution in strike-slip shear zones; the importance of the cataclastic flow

NASA Astrophysics Data System (ADS)

Moreira, N.; Dias, R.

2018-05-01

The Porto-Tomar-Ferreira do Alentejo dextral Shear Zone is one of the most important structures of the Iberian Variscides. In its vicinity, close to Abrantes (Central Portugal), a localized heterogeneous strain pattern developed in a decimetric metamorphic siliceous multilayer. This complex pattern was induced by the D2 dextral shearing of the early S0//S1 foliation in brittle-ductile conditions, giving rise to three main shear zone families. One of these families, with antithetic kinematics, delimits blocks with rigid clockwise rotation surrounded by coeval cataclasites, generating a local domino structure. The proposed geometrical and kinematic analysis, coupled with statistical studies, highlights the relation between subsidiary shear zones and the main shear zone. Despite the heterogeneous strain pattern, a quantitative approach of finite strain was applied based on the restoration of the initial fracture pattern. This approach shows the importance of the cataclastic flow coupled with the translational displacement of the domino domain in solving space problems related to the rigid block rotation. Such processes are key in allowing the rigid block rotation inside shear zones whenever the simple shear component is a fundamental mechanism.

Mesoscopic Rigid Body Modelling of the Extracellular Matrix Self-Assembly.

PubMed

Wong, Hua; Prévoteau-Jonquet, Jessica; Baud, Stéphanie; Dauchez, Manuel; Belloy, Nicolas

2018-06-11

The extracellular matrix (ECM) plays an important role in supporting tissues and organs. It even has a functional role in morphogenesis and differentiation by acting as a source of active molecules (matrikines). Many diseases are linked to dysfunction of ECM components and fragments or changes in their structures. As such it is a prime target for drugs. Because of technological limitations for observations at mesoscopic scales, the precise structural organisation of the ECM is not well-known, with sparse or fuzzy experimental observables. Based on the Unity3D game and physics engines, along with rigid body dynamics, we propose a virtual sandbox to model large biological molecules as dynamic chains of rigid bodies interacting together to gain insight into ECM components behaviour in the mesoscopic range. We have preliminary results showing how parameters such as fibre flexibility or the nature and number of interactions between molecules can induce different structures in the basement membrane. Using the Unity3D game engine and virtual reality headset coupled with haptic controllers, we immerse the user inside the corresponding simulation. Untrained users are able to navigate a complex virtual sandbox crowded with large biomolecules models in a matter of seconds.

Redistribution of flexibility in stabilizing antibody fragment mutants follows Le Châtelier's principle.

PubMed

Li, Tong; Tracka, Malgorzata B; Uddin, Shahid; Casas-Finet, Jose; Jacobs, Donald J; Livesay, Dennis R

2014-01-01

Le Châtelier's principle is the cornerstone of our understanding of chemical equilibria. When a system at equilibrium undergoes a change in concentration or thermodynamic state (i.e., temperature, pressure, etc.), La Châtelier's principle states that an equilibrium shift will occur to offset the perturbation and a new equilibrium is established. We demonstrate that the effects of stabilizing mutations on the rigidity ⇔ flexibility equilibrium within the native state ensemble manifest themselves through enthalpy-entropy compensation as the protein structure adjusts to restore the global balance between the two. Specifically, we characterize the effects of mutation to single chain fragments of the anti-lymphotoxin-β receptor antibody using a computational Distance Constraint Model. Statistically significant changes in the distribution of both rigidity and flexibility within the molecular structure is typically observed, where the local perturbations often lead to distal shifts in flexibility and rigidity profiles. Nevertheless, the net gain or loss in flexibility of individual mutants can be skewed. Despite all mutants being exclusively stabilizing in this dataset, increased flexibility is slightly more common than increased rigidity. Mechanistically the redistribution of flexibility is largely controlled by changes in the H-bond network. For example, a stabilizing mutation can induce an increase in rigidity locally due to the formation of new H-bonds, and simultaneously break H-bonds elsewhere leading to increased flexibility distant from the mutation site via Le Châtelier. Increased flexibility within the VH β4/β5 loop is a noteworthy illustration of this long-range effect.

Redistribution of Flexibility in Stabilizing Antibody Fragment Mutants Follows Le Châtelier’s Principle

PubMed Central

Li, Tong; Tracka, Malgorzata B.; Uddin, Shahid; Casas-Finet, Jose; Jacobs, Donald J.; Livesay, Dennis R.

2014-01-01

Le Châtelier’s principle is the cornerstone of our understanding of chemical equilibria. When a system at equilibrium undergoes a change in concentration or thermodynamic state (i.e., temperature, pressure, etc.), La Châtelier’s principle states that an equilibrium shift will occur to offset the perturbation and a new equilibrium is established. We demonstrate that the effects of stabilizing mutations on the rigidity ⇔ flexibility equilibrium within the native state ensemble manifest themselves through enthalpy-entropy compensation as the protein structure adjusts to restore the global balance between the two. Specifically, we characterize the effects of mutation to single chain fragments of the anti-lymphotoxin-β receptor antibody using a computational Distance Constraint Model. Statistically significant changes in the distribution of both rigidity and flexibility within the molecular structure is typically observed, where the local perturbations often lead to distal shifts in flexibility and rigidity profiles. Nevertheless, the net gain or loss in flexibility of individual mutants can be skewed. Despite all mutants being exclusively stabilizing in this dataset, increased flexibility is slightly more common than increased rigidity. Mechanistically the redistribution of flexibility is largely controlled by changes in the H-bond network. For example, a stabilizing mutation can induce an increase in rigidity locally due to the formation of new H-bonds, and simultaneously break H-bonds elsewhere leading to increased flexibility distant from the mutation site via Le Châtelier. Increased flexibility within the VH β4/β5 loop is a noteworthy illustration of this long-range effect. PMID:24671209

Effects of Structural Deformations of the Crank-Slider Mechanism on the Estimation of the Instantaneous Engine Friction Torque

NASA Astrophysics Data System (ADS)

CHALHOUB, N. G.; NEHME, H.; HENEIN, N. A.; BRYZIK, W.

1999-07-01

The focus on the current study is to assess the effects of structural deformations of the crankshaft/connecting-rod/piston mechanism on the computation of the instantaneous engine friction torque. This study is performed in a fully controlled environment in order to isolate the effects of structural deformations from those of measurement errors or noise interference. Therefore, a detailed model, accounting for the rigid and flexible motions of the crank-slider mechanism and including engine component friction formulations, is considered in this study. The model is used as a test bed to generate the engine friction torque,Tfa, and to predict the rigid and flexible motions of the system in response to the cylinder gas pressure. The torsional vibrations and the rigid body angular velocity of the crankshaft, as predicted by the detailed model of the crank-slider mechanism, are used along with the engine load torque and the cylinder gas pressure in the (P-ω) method to estimate the engine friction torque,Tfe. This method is well suited for the purpose of this study because its formulation is based on the rigid body model of the crank-slider mechanism. The digital simulation results demonstrate that the exclusion of the structural deformations of the crank-slider mechanism from the formulation of the (P-ω) method leads to an overestimation of the engine friction torque near the top-dead-center (TDC) position of the piston under firing conditions. Moreover, for the remainder of the engine cycle, the estimated friction torque exhibits large oscillations and takes on positive numerical values as if it is inducing energy into the system. Thus, the adverse effects of structural deformations of the crank-slider mechanism on the estimation of the engine friction torque greatly differ in their nature from one phase of the engine cycle to another.

The effects of wing flexibility on the flight performance and stability of flapping wing micro air vehicles

NASA Astrophysics Data System (ADS)

Bluman, James Edward

Insect wings are flexible. However, the influence of wing flexibility on the flight dynamics of insects and flapping wing micro air vehicles is unknown. Most studies in the literature consider rigid wings and conclude that the hover equilibrium is unstable. This dissertation shows that a flapping wing flyer with flexible wings exhibits stable natural modes of the open loop system in hover, never reported before. The free-flight insect flight dynamics is modeled for both flexible and rigid wings. Wing mass and inertia are included in the nonlinear equations of motion. The flapping wing aerodynamics are modeled using a quasi-steady model, a well-validated two dimensional Navier Stokes model, and a coupled, two dimensional Navier Stokes - Euler Bernoulli beam model that accurately models the fluid-structure interaction of flexible wings. Hover equilibrium is systematically and efficiently determined with a coupled quasi-steady and Navier-Stokes equation trimmer. The power and stability are reported at hover while parametrically varying the pitch axis location for rigid wings and the structural stiffness for flexible wings. The results indicate that the rigid wings possess an unstable oscillatory mode mainly due to their pitch sensitivity to horizontal velocity perturbations. The flexible wings stabilize this mode primarily by adjusting their wing shape in the presence of perturbations. The wing's response to perturbations generates significantly more horizontal velocity damping and pitch rate damping than in rigid wings. Furthermore, the flexible wings experience substantially less wing wake interaction, which, for rigid wings, is destabilizing. The power required to hover a fruit fly with actively rotating rigid wings varies between 16.9 and 34.2 W/kg. The optimal power occurs when the pitch axis is located at 30% chord, similar to some biological observations. Flexible wings require 23.1 to 38.5 W/kg. However, flexible wings exhibit more stable system dynamics and allow for simpler and lighter designs since they do not require pitch actuation mechanisms. This study is the first to evaluate the impact of wing flexibility on the hovering stability of flapping flyers, which can explain the ranges of flexibility seen in insects and can inform designs of synthetic flapping wing robots.

A crawling robot driven by multi-stable origami

NASA Astrophysics Data System (ADS)

Pagano, Alexander; Yan, Tongxi; Chien, Brian; Wissa, A.; Tawfick, S.

2017-09-01

Using origami folding to construct and actuate mechanisms and machines offers attractive opportunities from small, scalable, and cheap robots to deployable adaptive structures. This paper presents the design of a bio-inspired origami crawling robot constructed by folding sheets of paper. The origami building block structure is based on the Kresling crease pattern (CP), a chiral tower with a polygonal base, which expands and contracts through coupled longitudinal and rotational motion similar to a screw. We design the origami to have multi-stable structural equilibria which can be tuned by changing the folding CP. Kinematic analysis of these structures based on rigid-plates and hinges at fold lines precludes the shape transformation associated with the bistability of the physical models. To capture the kinematics of the bi-stable origami, the panels’ deformation behavior is modeled utilizing principles of virtual folds. Virtual folds approximate material bending by hinged, rigid panels, which facilitates the development of a kinematic solution via rigid-plate rotation analysis. As such, the kinetics and stability of folded structures are investigated by assigning suitable torsional spring constants to the fold lines. The results presented demonstrate the effect of fold-pattern geometries on the snapping behavior of the bi-stable origami structure based on the Kresling pattern. The crawling robot is presented as a case study for the use of this origami structure to mimic crawling locomotion. The robot is comprised of two origami towers nested inside a paper bellow, and connected by 3D printed end plates. DC motors are used to actuate the expansion and contraction of the internal origami structures to achieve forward locomotion and steering. Beyond locomotion, this simple design can find applications in manipulators, booms, and active structures.

Arginine Kinase. Joint Crystallographic & NMR RDC Analyses link Substrate-Associated Motions to Intrinsic Flexibility

PubMed Central

Niu, Xiaogang; Brüschweiler-Li, Lei; Davulcu, Omar; Skalicky, Jack J.; Brüschweiler, Rafael; Chapman, Michael S.

2010-01-01

The phosphagen kinase family, including creatine and arginine kinases, catalyze the reversible transfer of a “high energy” phosphate between ATP and a phospho-guanidino substrate. They have become a model for the study of both substrate-induced conformational change and intrinsic protein dynamics. Prior crystallographic studies indicated large substrate-induced domain rotations, but differences among a recent set of arginine kinase structures was interpreted as a plastic deformation. Here, the structure of Limulus substrate-free arginine kinase is refined against high resolution crystallographic data and compared quantitatively with NMR chemical shifts and residual dipolar couplings (RDCs). This demonstrates the feasibility of this type of RDC analysis of proteins that are large by NMR standards (42 kDa), and illuminates the solution structure, free from crystal-packing constraints. Detailed comparison of the 1.7 Å resolution substrate-free crystal structure against the 1.2 Å transition state analog complex shows large substrate-induced domain motions which can be broken down into movements of smaller quasi-rigid bodies. The solution state structure of substrate-free arginine kinase is most consistent with an equilibrium of substrate-free and –bound structures, with the substrate-free form dominating, but with varying displacements of the quasi-rigid groups. Rigid-group rotations evident from the crystal structures are about axes previously associated with intrinsic millisecond dynamics using NMR relaxation dispersion. Thus, “substrate-induced” motions are along modes that are intrinsically flexible in the substrate-free enzyme, and likely involve some degree of conformational selection. PMID:21075117

Modular Approach to Structural Simulation for Vehicle Crashworthiness Prediction

DOT National Transportation Integrated Search

1975-03-01

A modular formulation for simulation of the structural deformation and deceleration of a vehicle for crashworthiness and collision compatibility is presented. This formulation includes three dimensional beam elements, various spring elements, rigid b...

Unilateral contact induced blade/casing vibratory interactions in impellers: Analysis for rigid casings

NASA Astrophysics Data System (ADS)

Batailly, Alain; Meingast, Markus; Legrand, Mathias

2015-02-01

This contribution addresses the vibratory analysis of unilateral-contact induced structural interactions between a bladed impeller and its surrounding rigid casing. Such assemblies can be found in helicopter or small aircraft engines for instance and the interactions of interest shall arise due to the always tighter operating clearances between the rotating and stationary components. The investigation is conducted by extending to cyclically symmetric structures an in-house time-marching based tool dedicated to unilateral contact occurrences in turbomachines. The main components of the considered impeller together with the associated assumptions and modelling principles considered in this work are detailed. Typical dynamical features of cyclically symmetric structures, such as the aliasing effect and frequency clustering are explored in this nonlinear framework by means of thorough frequency-domain analyses and harmonic trackings of the numerically predicted impeller displacements. Additional contact maps highlight the existence of critical rotational velocities at which displacements potentially reach high amplitudes due to the synchronization of the bladed assembly vibratory pattern with the shape of the rigid casing. The proposed numerical investigations are also compared to a simpler and (almost) empirical criterion: it is suggested, based on nonlinear numerical simulations with a linear reduced order model of the impeller and a rigid casing, that this criterion may miss important critical velocities emanating from the unfavorable combination of aliasing and contact-induced higher harmonics in the vibratory response of the impeller. Overall, this work suggests a way to enhance guidelines to improve the design of impellers in the context of nonlinear and nonsmooth dynamics.

Effect of replacing polyol by organosolv and kraft lignin on the property and structure of rigid polyurethane foam.

PubMed

Pan, Xuejun; Saddler, Jack N

2013-01-28

Lignin is one of the three major components in plant cell walls, and it can be isolated (dissolved) from the cell wall in pretreatment or chemical pulping. However, there is a lack of high-value applications for lignin, and the commonest proposal for lignin is power and steam generation through combustion. Organosolv ethanol process is one of the effective pretreatment methods for woody biomass for cellulosic ethanol production, and kraft process is a dominant chemical pulping method in paper industry. In the present research, the lignins from organosolv pretreatment and kraft pulping were evaluated to replace polyol for producing rigid polyurethane foams (RPFs). Petroleum-based polyol was replaced with hardwood ethanol organosolv lignin (HEL) or hardwood kraft lignin (HKL) from 25% to 70% (molar percentage) in preparing rigid polyurethane foam. The prepared foams contained 12-36% (w/w) HEL or 9-28% (w/w) HKL. The density, compressive strength, and cellular structure of the prepared foams were investigated and compared. Chain extenders were used to improve the properties of the RPFs. It was found that lignin was chemically crosslinked not just physically trapped in the rigid polyurethane foams. The lignin-containing foams had comparable structure and strength up to 25-30% (w/w) HEL or 19-23% (w/w) HKL addition. The results indicated that HEL performed much better in RPFs and could replace more polyol at the same strength than HKL because the former had a better miscibility with the polyol than the latter. Chain extender such as butanediol could improve the strength of lignin-containing RPFs.

Follow on Researches for X-56A Aircraft at NASA Dryden Flight Research Center (Progress Report)

NASA Technical Reports Server (NTRS)

Pak, Chan-Gi

2012-01-01

A lot of composite materials are used for the modern aircraft to reduce its weight. Aircraft aeroservoelastic models are typically characterized by significant levels of model parameter uncertainty due to composite manufacturing process. Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of X-56A aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes is based on the flutter analysis of X-56A aircraft. It should be noted that for all three Mach number cases rigid body modes and mode numbers seven and nine are participated 89.1 92.4 % of the first flutter mode. Modal participation of the rigid body mode and mode numbers seven and nine for the second flutter mode are 94.6 96.4%. Rigid body mode and the first two anti-symmetric modes, eighth and tenth modes, are participated 93.2 94.6% of the third flutter mode. Therefore, rigid body modes and the first four flexible modes of X-56A aircraft are the primary modes during the model tuning procedure. The ground vibration test-validated structural dynamic finite element model of the X-56A aircraft is to obtain in this study. The structural dynamics finite element model of X-56A aircraft is improved using the parallelized big-bang big-crunch algorithm together with a hybrid optimization technique.

Adhesive plasters. [Patent application; coatings for crucibles, control rods, etc

DOEpatents

Holcombe, C.E. Jr.; Swain, R.L.; Banker, J.G.; Edwards, C.C.

1975-09-26

Adhesive plaster compositions are provided by treating particles of Y/sub 2/O/sub 3/, Eu/sub 2/O/sub 3/, Gd/sub 2/O/sub 3/, or Nd/sub 2/O/sub 3/ with dilute acid solutions. The resulting compositions were found to harden spontaneously into rigid reticulated masses resembling plaster of Paris. Upon heating, the hardened material is decomposed into the oxide, yet retains the reticulated rigid structure. 1 table.

Research on durability of a concrete continuous rigid frame bridge

NASA Astrophysics Data System (ADS)

Shi, Jing-xian; Ran, Zhi-hong

2018-05-01

The research on the durability of concrete structures has also become one of the most important topics for discussion at international academic institutions and conferences. This paper summarizes and reviews the current research on the durability of bridge structure of the bridge at the index relationship between state lifetime and structure durability. According to the actual situation in this paper on a continuous rigid frame bridge China of Yunnan as an example, this bridge was completed and opened to traffic during the first half of the year, a series of tests are carried out for the durability problem. It is found that all the indicators are good within six months after the bridge opened to traffic, but durability issues should be further studied in future monitoring efforts.

Nuclear quantum effects in water clusters: the role of the molecular flexibility.

PubMed

González, Briesta S; Noya, Eva G; Vega, Carlos; Sesé, Luis M

2010-02-25

With the objective of establishing the importance of water flexibility in empirical models which explicitly include nuclear quantum effects, we have carried out path integral Monte Carlo simulations in water clusters with up to seven molecules. Two recently developed models have been used for comparison: the rigid TIP4PQ/2005 and the flexible q-TIP4P/F models, both inspired by the rigid TIP4P/2005 model. To obtain a starting configuration for our simulations, we have located the global minima for the rigid TIP4P/2005 and TIP4PQ/2005 models and for the flexible q-TIP4P/F model. All the structures are similar to those predicted by the rigid TIP4P potential showing that the charge distribution mainly determines the global minimum structure. For the flexible q-TIP4P/F model, we have studied the geometrical distortion upon isotopic substitution by studying tritiated water clusters. Our results show that tritiated water clusters exhibit an r(OT) distance shorter than the r(OH) distance in water clusters, not significant changes in the Phi(HOH) angle, and a lower average dipole moment than water clusters. We have also carried out classical simulations with the rigid TIP4PQ/2005 model showing that the rotational kinetic energy is greatly affected by quantum effects, but the translational kinetic energy is only slightly modified. The potential energy is also noticeably higher than in classical simulations. Finally, as a concluding remark, we have calculated the formation energies of water clusters using both models, finding that the formation energies predicted by the rigid TIP4PQ/2005 model are lower by roughly 0.6 kcal/mol than those of the flexible q-TIP4P/F model for clusters of moderate size, the origin of this difference coming mainly from the geometrical distortion of the water molecule in the clusters that causes an increase in the intramolecular potential energy.

Roles for Cardiac MyBP-C in Maintaining Myofilament Lattice Rigidity and Prolonging Myosin Cross-Bridge Lifetime

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

Palmer, B.M.; Sadayappan, S.; Wang, Y.

2011-10-06

We investigated the influence of cardiac myosin binding protein-C (cMyBP-C) and its constitutively unphosphorylated status on the radial and longitudinal stiffnesses of the myofilament lattice in chemically skinned myocardial strips of the following mouse models: nontransgenic (NTG), effective null for cMyBP-C (t/t), wild-type cMyBP-C expressed into t/t (WT{sub t/t}), and constitutively unphosphorylated cMyBP-C (AllP{sub -t/t}). We found that the absence of cMyBP-C in the t/t and the unphosphorylated cMyBP-C in the AllP{sub -t/t} resulted in a compressible cardiac myofilament lattice induced by rigor not observed in the NTG and WT{sub t/t}. These results suggest that the presence and phosphorylation ofmore » the N-terminus of cMyBP-C provides structural support and radial rigidity to the myofilament lattice. Examination of myofilament longitudinal stiffness under rigor conditions demonstrated a significant reduction in cross-bridge-dependent stiffness in the t/t compared with NTG controls, but not in the AllP{sub -t/t} compared with WT{sub t/t} controls. The absence of cMyBP-C in the t/t and the unphosphorylated cMyBP-C in the AllP{sub -t/t} both resulted in a shorter myosin cross-bridge lifetime when myosin isoform was controlled. These data collectively suggest that cMyBP-C provides radial rigidity to the myofilament lattice through the N-terminus, and that disruption of the phosphorylation of cMyBP-C is sufficient to abolish this structural role of the N-terminus and shorten cross-bridge lifetime. Although the presence of cMyBP-C also provides longitudinal rigidity, phosphorylation of the N-terminus is not necessary to maintain longitudinal rigidity of the lattice, in contrast to radial rigidity.« less

Neutron scattering reveals the dynamic basis of protein adaptation to extreme temperature.

PubMed

Tehei, Moeava; Madern, Dominique; Franzetti, Bruno; Zaccai, Giuseppe

2005-12-09

To explore protein adaptation to extremely high temperatures, two parameters related to macromolecular dynamics, the mean square atomic fluctuation and structural resilience, expressed as a mean force constant, were measured by neutron scattering for hyperthermophilic malate dehydrogenase from Methanococcus jannaschii and a mesophilic homologue, lactate dehydrogenase from Oryctolagus cunniculus (rabbit) muscle. The root mean square fluctuations, defining flexibility, were found to be similar for both enzymes (1.5 A) at their optimal activity temperature. Resilience values, defining structural rigidity, are higher by an order of magnitude for the high temperature-adapted protein (0.15 Newtons/meter for O. cunniculus lactate dehydrogenase and 1.5 Newtons/meter for M. jannaschii malate dehydrogenase). Thermoadaptation appears to have been achieved by evolution through selection of appropriate structural rigidity in order to preserve specific protein structure while allowing the conformational flexibility required for activity.

System definition study of deployable, non-metallic space structures

NASA Technical Reports Server (NTRS)

Stimler, F. J.

1984-01-01

The state of the art for nonmetallic materials and fabrication techniques suitable for future space structures are summarized. Typical subsystems and systems of interest to the space community that are reviewed include: (1) inflatable/rigidized space hangar; (2) flexible/storable acoustic barrier; (3) deployable fabric bulkhead in a space habitat; (4) extendible tunnel for soft docking; (5) deployable space recovery/re-entry systems for personnel or materials; (6) a manned habitat for a space station; (7) storage enclosures external to the space station habitat; (8) attachable work stations; and (9) safe haven structures. Performance parameters examined include micrometeoroid protection; leakage rate prediction and control; rigidization of flexible structures in the space environment; flammability and offgassing; lifetime for nonmetallic materials; crack propagation prevention; and the effects of atomic oxygen and space debris. An expandable airlock for shuttle flight experiments and potential tethered experiments from shuttle are discussed.

Local structure and structural rigidity of the green phosphor β-SiAlON:Eu{sup 2+}

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

Brgoch, J., E-mail: jbrgoch@uh.edu; Gaultois, M. W., E-mail: mgaultois@mrl.ucsb.edu; Seshadri, R.

Eu{sup 2+} inserted in β-Si{sub 3−x}Al{sub x}O{sub x}N{sub 4−x} is a material that shows exceptional promise as a green-emitting phosphor. Synchrotron X-ray and neutron scattering, in conjunction with first-principles calculations and Eu L{sub 3} X-ray absorption measurements, yield a consistent picture of the composition, and the favorable position for Eu{sup 2+} substitution in the crystal structure. The Debye temperature Θ{sub D}, which is a proxy for structural rigidity relating to effectiveness as a phosphor, is very high for the starting β-Si{sub 3}N{sub 4} framework and is determined to decrease only slightly for the small amounts of Al{sup 3+} and O{supmore » 2−} co-substitution that are required for charge balance associated with Eu{sup 2+} insertion.« less

HyBAR: hybrid bone-attached robot for joint arthroplasty.

PubMed

Song, S; Mor, A; Jaramaz, B

2009-06-01

A number of small bone-attached surgical robots have been introduced to overcome some disadvantages of large stand-alone surgical robots. In orthopaedics, increasing demand on minimally invasive joint replacement surgery has also been encouraging small surgical robot developments. Among various technical aspects of such an approach, optimal miniaturization that maintains structural strength for high speed bone removal was investigated. By observing advantages and disadvantages from serial and parallel robot structures, a new hybrid kinematic configuration was designed for a bone-attached robot to perform precision bone removal for cutting the femoral implant cavity during patellofemoral joint arthroplasty surgery. A series of experimental tests were conducted in order to evaluate the performance of the new robot, especially with respect to accuracy of bone preparation. A miniaturized and rigidly-structured robot prototype was developed for minimally invasive bone-attached robotic surgery. A new minimally invasive modular clamping system was also introduced to enhance the robotic procedure. Foam and pig bone experimental results demonstrated a successful implementation of the new robot that eliminated a number of major design problems of a previous prototype. For small bone-attached surgical robots that utilize high speed orthopaedic tools, structural rigidity and clamping mechanism are major design issues. The new kinematic configuration using hinged prismatic joints enabled an effective miniaturization with good structural rigidity. Although minor problems still exist at the prototype stage, the new development would be a significant step towards the practical use of such a robot.

Multiscale multiphysics and multidomain models—Flexibility and rigidity

PubMed Central

Xia, Kelin; Opron, Kristopher; Wei, Guo-Wei

2013-01-01

The emerging complexity of large macromolecules has led to challenges in their full scale theoretical description and computer simulation. Multiscale multiphysics and multidomain models have been introduced to reduce the number of degrees of freedom while maintaining modeling accuracy and achieving computational efficiency. A total energy functional is constructed to put energies for polar and nonpolar solvation, chemical potential, fluid flow, molecular mechanics, and elastic dynamics on an equal footing. The variational principle is utilized to derive coupled governing equations for the above mentioned multiphysical descriptions. Among these governing equations is the Poisson-Boltzmann equation which describes continuum electrostatics with atomic charges. The present work introduces the theory of continuum elasticity with atomic rigidity (CEWAR). The essence of CEWAR is to formulate the shear modulus as a continuous function of atomic rigidity. As a result, the dynamics complexity of a macromolecular system is separated from its static complexity so that the more time-consuming dynamics is handled with continuum elasticity theory, while the less time-consuming static analysis is pursued with atomic approaches. We propose a simple method, flexibility-rigidity index (FRI), to analyze macromolecular flexibility and rigidity in atomic detail. The construction of FRI relies on the fundamental assumption that protein functions, such as flexibility, rigidity, and energy, are entirely determined by the structure of the protein and its environment, although the structure is in turn determined by all the interactions. As such, the FRI measures the topological connectivity of protein atoms or residues and characterizes the geometric compactness of the protein structure. As a consequence, the FRI does not resort to the interaction Hamiltonian and bypasses matrix diagonalization, which underpins most other flexibility analysis methods. FRI's computational complexity is of \\documentclass[12pt]{minimal}\\begin{document}${\\cal O}(N^2)$\\end{document}O(N2) at most, where N is the number of atoms or residues, in contrast to \\documentclass[12pt]{minimal}\\begin{document}${\\cal O}(N^3)$\\end{document}O(N3) for Hamiltonian based methods. We demonstrate that the proposed FRI gives rise to accurate prediction of protein B-Factor for a set of 263 proteins. We show that a parameter free FRI is able to achieve about 95% accuracy of the parameter optimized FRI. An interpolation algorithm is developed to construct continuous atomic flexibility functions for visualization and use with CEWAR. PMID:24320318

Multiscale multiphysics and multidomain models—Flexibility and rigidity

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

Xia, Kelin; Opron, Kristopher; Wei, Guo-Wei, E-mail: wei@math.msu.edu

The emerging complexity of large macromolecules has led to challenges in their full scale theoretical description and computer simulation. Multiscale multiphysics and multidomain models have been introduced to reduce the number of degrees of freedom while maintaining modeling accuracy and achieving computational efficiency. A total energy functional is constructed to put energies for polar and nonpolar solvation, chemical potential, fluid flow, molecular mechanics, and elastic dynamics on an equal footing. The variational principle is utilized to derive coupled governing equations for the above mentioned multiphysical descriptions. Among these governing equations is the Poisson-Boltzmann equation which describes continuum electrostatics with atomicmore » charges. The present work introduces the theory of continuum elasticity with atomic rigidity (CEWAR). The essence of CEWAR is to formulate the shear modulus as a continuous function of atomic rigidity. As a result, the dynamics complexity of a macromolecular system is separated from its static complexity so that the more time-consuming dynamics is handled with continuum elasticity theory, while the less time-consuming static analysis is pursued with atomic approaches. We propose a simple method, flexibility-rigidity index (FRI), to analyze macromolecular flexibility and rigidity in atomic detail. The construction of FRI relies on the fundamental assumption that protein functions, such as flexibility, rigidity, and energy, are entirely determined by the structure of the protein and its environment, although the structure is in turn determined by all the interactions. As such, the FRI measures the topological connectivity of protein atoms or residues and characterizes the geometric compactness of the protein structure. As a consequence, the FRI does not resort to the interaction Hamiltonian and bypasses matrix diagonalization, which underpins most other flexibility analysis methods. FRI's computational complexity is of O(N{sup 2}) at most, where N is the number of atoms or residues, in contrast to O(N{sup 3}) for Hamiltonian based methods. We demonstrate that the proposed FRI gives rise to accurate prediction of protein B-Factor for a set of 263 proteins. We show that a parameter free FRI is able to achieve about 95% accuracy of the parameter optimized FRI. An interpolation algorithm is developed to construct continuous atomic flexibility functions for visualization and use with CEWAR.« less

Bifunctional role of leucine 300 of firefly luciferase in structural rigidity.

PubMed

Yousefi, Farzad; Ataei, Farangis; Mortazavi, Mojtaba; Hosseinkhani, Saman

2017-08-01

Firefly luciferase is susceptible to thermal inactivation, thereby its intracellular half-life decreased. Previous reports indicated that L 300 R mutation (LRR mutant) in E 354 R/Arg 356 double mutant (ERR mutant) from Lampyris turkestanicus luciferase has increased its thermal stability and rigidity through induction of some ionic bonds with Asp 270 and 271. Disruption of the deduced ionic bonds in an ultra-rigid mutant of firefly luciferase did not reverse the flexibility of the protein. In this study, we investigated the effects of this residue to find the truth behind an extraordinary increase in thermal stability and rigidity of luciferase after replacement of leucine 300 by arginine based on previous reports. For this purpose, L 300 R, L 300 K and L 300 E mutations were performed to compare the effects of these mutations on the native firefly luciferase. In spite of increase of intrinsic fluorescence of the mutants a slight increase in thermostability and retention of kinetic properties was observed. Based on our results, we can conclude that L 300 R mutation in LRR mutant accompanying with alteration in a flexible loop (352-359) increased thermostability and rigidity of luciferase. Copyright © 2017 Elsevier B.V. All rights reserved.

Complex vibrations in arsenide skutterudites and oxyskutterudites

NASA Astrophysics Data System (ADS)

Bridges, F.; Car, B.; Sutton, L.; Hoffman-Stapleton, M.; Keiber, T.; Baumbach, R. E.; Maple, M. B.; Henkie, Z.; Wawryk, R.

2015-01-01

The local structure of two skutterudite families—Ce M4As12 (M =Fe , Ru, Os) and L n Cu3Ru4O12 (L n =La , Pr, and Nd)—have been studied using the extended x-ray absorption fine structure (EXAFS) technique with a focus on the lattice vibrations about the rare-earth "rattler atoms" and the extent to which these vibrations can be considered local modes, with the rattler vibrating inside a nearly rigid cage. X-ray absorption data at all the metal edges were collected over a temperature range of 4 to 300 K and analyzed using standard procedures. The pair distances from EXAFS results agree quite well with the average structure obtained from diffraction. The cage structure is formed by the M and As atoms in Ce M4As12 and by Cu, O, and Ru atoms in L n Cu3Ru4O12 . Although some of the bonds within the cage are quite stiff (correlated Debye temperatures, θcD, are ˜500 K for Ce M4As12 and above 800 K for L n Cu3Ru4O12 ), we show that the structure is not completely rigid. For the rattler atom the nearest-neighbor pairs have a relatively low Einstein temperature, θE:˜100 - 120 K for Ce-As and ˜130 K for L n -O . Surprisingly, the behaviors of the second-neighbor pairs are quite different: for Ce M4As12 the second-neighbor pairs (Ce -M ) have a weaker bond while for L n Cu3Ru4O12 the L n -Ru second-neighbor pair has a stiffer effective spring constant than the first-neighbor pair. In addition, we show that the As4 or CuO4 rings are relatively rigid units and that their vibrations are anisotropic within these cubic structures, with stiff restoring forces perpendicular to the rings and much weaker restoring forces in directions parallel to the rings. Consequently vibrations of the rings may also act as "rattlers" and help suppress thermal conductivity. In general neither the rigid-cage approximation nor the simple reduced-mass approximation are sufficient for describing rattler behavior.

Sealed fiber-optic bundle feedthrough

DOEpatents

Tanner, Carol E.

2002-01-01

A sealed fiber-optic bundle feedthrough by which a multitude of fiber-optic elements may be passed through an opening or port in a wall or structure separating two environments at different pressures or temperatures while maintaining the desired pressure or temperature in each environment. The feedthrough comprises a rigid sleeve of suitable material, a bundle of individual optical fibers, and a resin-based sealing material that bonds the individual optical fibers to each other and to the rigid sleeve.

Toward Theoretical Foundations of Resistive Force Theory of Granular-Structural Interaction, with Expansions to Flexible Locomotors

DTIC Science & Technology

2015-05-07

the proper depth-dependent pressure distribution before intruder motion begins. We model the intruder as a rigid surface within the granular body by...assigning corresponding planar nodes to move as a rigid body at a constant rate. This resembles a fully rough surface due to the no-slip condition, no...Stokesian fluids. Despite its remarkable capability to predict experimental locomotion and force distributions on mobile bodies in granular media, there is

Evaluation of the Structural Performance of CTS Rapid Set Concrete Mix

DTIC Science & Technology

2016-08-01

June 2015, research was conducted at the U.S. Army Engineer Research and Development Center (ERDC) in Vicksburg, MS, to develop pavement design curves...using the Department of Defense’s (DoD) rigid pavement design method. Results indicate that the DoD’s rigid pavement design criteria are conservative...1.2 Objective and scope The objective of the research presented in this report was to develop pavement design curves relating CTS Rapid Set

Modeling the Flexural Rigidity of Rod Photoreceptors

PubMed Central

Haeri, Mohammad; Knox, Barry E.; Ahmadi, Aphrodite

2013-01-01

In vertebrate eyes, the rod photoreceptor has a modified cilium with an extended cylindrical structure specialized for phototransduction called the outer segment (OS). The OS has numerous stacked membrane disks and can bend or break when subjected to mechanical forces. The OS exhibits axial structural variation, with extended bands composed of a few hundred membrane disks whose thickness is diurnally modulated. Using high-resolution confocal microscopy, we have observed OS flexing and disruption in live transgenic Xenopus rods. Based on the experimental observations, we introduce a coarse-grained model of OS mechanical rigidity using elasticity theory, representing the axial OS banding explicitly via a spring-bead model. We calculate a bending stiffness of ∼105 nN⋅μm2, which is seven orders-of-magnitude larger than that of typical cilia and flagella. This bending stiffness has a quadratic relation to OS radius, so that thinner OS have lower fragility. Furthermore, we find that increasing the spatial frequency of axial OS banding decreases OS rigidity, reducing its fragility. Moreover, the model predicts a tendency for OS to break in bands with higher spring number density, analogous to the experimental observation that transgenic rods tended to break preferentially in bands of high fluorescence. We discuss how pathological alterations of disk membrane properties by mutant proteins may lead to increased OS rigidity and thus increased breakage, ultimately contributing to retinal degeneration. PMID:23442852

Operational Determination of Physical and Mechanical Properties of Cast Samples of High-Strength Iron by Means of a Magnetic-Mechanical Method

NASA Astrophysics Data System (ADS)

Slyusarev, Yu. K.; Braga, A. V.; Slyusarev, I. Yu.

2017-09-01

The effect of the chemical composition of high-strength cast iron VCh35 on the content, shape and diameter of graphite inclusions and on the presence of structurally-free cementite and defects is studied. A relationship is determined between the structure and metallurgical defects and characteristics of the mechanical and magnetic rigidity of cast samples. Relationships are established in a group of factors and property characteristics: chemical composition - microstructure - mechanical rigidity - magnetic stiffness. The basis of a method is established making it possible to perform operative non-destructive monitoring of the melt quality preparation for high-strength iron casting.

Conformational locking by design: relating strain energy with luminescence and stability in rigid metal-organic frameworks.

PubMed

Shustova, Natalia B; Cozzolino, Anthony F; Dincă, Mircea

2012-12-05

Minimization of the torsional barrier for phenyl ring flipping in a metal-organic framework (MOF) based on the new ethynyl-extended octacarboxylate ligand H(8)TDPEPE leads to a fluorescent material with a near-dark state. Immobilization of the ligand in the rigid structure also unexpectedly causes significant strain. We used DFT calculations to estimate the ligand strain energies in our and all other topologically related materials and correlated these with empirical structural descriptors to derive general rules for trapping molecules in high-energy conformations within MOFs. These studies portend possible applications of MOFs for studying fundamental concepts related to conformational locking and its effects on molecular reactivity and chromophore photophysics.

Asynchronous oscillations of rigid rods drive viscous fluid to swirl

NASA Astrophysics Data System (ADS)

Hayashi, Rintaro; Takagi, Daisuke

2017-12-01

We present a minimal system for generating flow at low Reynolds number by oscillating a pair of rigid rods in silicone oil. Experiments show that oscillating them in phase produces no net flow, but a phase difference alone can generate rich flow fields. Tracer particles follow complex trajectory patterns consisting of small orbital movements every cycle and then drifting or swirling in larger regions after many cycles. Observations are consistent with simulations performed using the method of regularized Stokeslets, which reveal complex three-dimensional flow structures emerging from simple oscillatory actuation. Our findings reveal the basic underlying flow structure around oscillatory protrusions such as hairs and legs as commonly featured on living and nonliving bodies.

Conformational Rigidity and Protein Dynamics at Distinct Timescales Regulate PTP1B Activity and Allostery.

PubMed

Choy, Meng S; Li, Yang; Machado, Luciana E S F; Kunze, Micha B A; Connors, Christopher R; Wei, Xingyu; Lindorff-Larsen, Kresten; Page, Rebecca; Peti, Wolfgang

2017-02-16

Protein function originates from a cooperation of structural rigidity, dynamics at different timescales, and allostery. However, how these three pillars of protein function are integrated is still only poorly understood. Here we show how these pillars are connected in Protein Tyrosine Phosphatase 1B (PTP1B), a drug target for diabetes and cancer that catalyzes the dephosphorylation of numerous substrates in essential signaling pathways. By combining new experimental and computational data on WT-PTP1B and ≥10 PTP1B variants in multiple states, we discovered a fundamental and evolutionarily conserved CH/π switch that is critical for positioning the catalytically important WPD loop. Furthermore, our data show that PTP1B uses conformational and dynamic allostery to regulate its activity. This shows that both conformational rigidity and dynamics are essential for controlling protein activity. This connection between rigidity and dynamics at different timescales is likely a hallmark of all enzyme function. Copyright © 2017 Elsevier Inc. All rights reserved.

Rigid High Temperature Heat-Shrinkable Polyimide Tubes with Functionality as Reducer Couplings

PubMed Central

Kong, Deyan; Xiao, Xinli

2017-01-01

Flexible and semi-rigid heat-shrinkable tubes (HSTs) have been used in thousands of applications, and here rigid high temperature HSTs are reported for the first time. These rigid HSTs are prepared with shape memory polyimides possessing glass transition temperatures (Tgs) from 182 to 295 °C, and the relationships between Tg and their molecular structures are studied. The polyimide HSTs (PIHSTs) can fix expanded diameters and shrink back to original diameters very well, and the mechanisms of their heat-shrinkage performance are discussed. Their differences from commercially available HSTs in heat-shrinkage are also analyzed. They can withstand low temperature of −196 °C, much lower than those of other HSTs. The PIHSTs can also connect subjects of different sizes by heat-shrinkage and then fix them upon cooling like reducer couplings, and the possible mechanisms of their reducer coupling effect are analyzed. With their unique characteristics, PIHSTs will expand the application areas of HSTs enormously. PMID:28317905

Simple models for rope substructure mechanics: application to electro-mechanical lifts

NASA Astrophysics Data System (ADS)

Herrera, I.; Kaczmarczyk, S.

2016-05-01

Mechanical systems modelled as rigid mass elements connected by tensioned slender structural members such as ropes and cables represent quite common substructures used in lift engineering and hoisting applications. Special interest is devoted by engineers and researchers to the vibratory response of such systems for optimum performance and durability. This paper presents simplified models that can be employed to determine the natural frequencies of systems having substructures of two rigid masses constrained by tensioned rope/cable elements. The exact solution for free un-damped longitudinal displacement response is discussed in the context of simple two-degree-of-freedom models. The results are compared and the influence of characteristics parameters such as the ratio of the average mass of the two rigid masses with respect to the rope mass and the deviation ratio of the two rigid masses with respect to the average mass is analyzed. This analysis gives criteria for the application of such simplified models in complex elevator and hoisting system configurations.

Deformable anatomical templates for brachytherapy treatment planning in radiotherapy of cervical cancer

NASA Astrophysics Data System (ADS)

Christensen, Gary E.; Williamson, Jeffrey F.; Chao, K. S. C.; Miller, Michael I.; So, F. B.; Vannier, Michael W.

1997-10-01

This paper describes a new method to register serial, volumetric x-ray computed tomography (CT) data sets for tracking soft-tissue deformation caused by insertion of intracavity brachytherapy applicators to treat cervical cancer. 3D CT scans collected from the same patient with and without a brachytherapy applicator are registered to aid in computation of the radiation dose to tumor and normal tissue. The 3D CT image volume of pelvic anatomy with the applicator. Initial registration is accomplished by rigid alignment of the pelvic bones and non-rigid alignment of gray scale CT data and hand segmentations of the vagina, cervix, bladder, and rectum. A viscous fluid transformation model is used for non-rigid registration to allow for local, non-linear registration of the vagina, cervix, bladder, and rectum without disturbing the rigid registration of the bony pelvis and adjacent structures. Results are presented in which two 3D CT data sets of the same patient - imaged with and without a brachytherapy applicator - are registered.

Coarse grained models, bond orientational order, and the structural characterization of residue networks

NASA Astrophysics Data System (ADS)

Ortiz, Carlos Pompeyo

Rigidity emerges in a broad class of soft matter systems, relevant to many industrial and biological processes. In our experiments, we study a model soft matter system, hard-sphere Brownian suspensions of submicron particles. Brownian suspensions lack rigidity in the absence of external driving, but form flow-stabilized solid-like microsphere heaps under the influence of hydrodynamic forces. The overarching question driving my dissertation is "What is the nature of the rigidity of these microsphere heaps?" Does the rigidity of the heaps follow from mechanical stability driven by a sufficiently interconnected network of particle contacts? Or, does the rigidity of the heaps follow from a kinetic glass transition characterized by a diverging resistance to flow such that the time necessary to observe rearrangements grows prohibitively large? We expect that insights into the mechanism of rigidity of Brownian microsphere heaps are applicable to a wide class of soft matter systems. In this thesis,we have overcome the limitations of previous experimental approaches. Namely, we show that the rigidity of our heaps does not emerge from the effects of gravity, inertia, static friction, or van der Waals sticking. In Chapter 1 of thesis, we review the background literature. In Chapter 2, we present the experimental, analytical, and computational methods used in the remainder of the thesis. In Chapter 3, we investigate the onset of rigidity by characterizing the steady-state size of the heap versus the imposed flow conditions. We show that thermal fluctuations and repulsive interparticle interactions, the dominant forces at the single-particle scale, suppress the development of a rigid phase. These conditions imply that the onset of rigidity in involves many-body collective interactions. In Chapter 4, we measure the response of the heap to external perturbations, which allows us to measure their elastic modulus and compare our results to hard sphere theoretical expectations. We find bulk nonlinear elastic behavior. In Chapter 5, we study the particle displacements in response to external perturbations and quantify the local nonlinear elastic behavior.

Unified control/structure design and modeling research

NASA Technical Reports Server (NTRS)

Mingori, D. L.; Gibson, J. S.; Blelloch, P. A.; Adamian, A.

1986-01-01

To demonstrate the applicability of the control theory for distributed systems to large flexible space structures, research was focused on a model of a space antenna which consists of a rigid hub, flexible ribs, and a mesh reflecting surface. The space antenna model used is discussed along with the finite element approximation of the distributed model. The basic control problem is to design an optimal or near-optimal compensator to suppress the linear vibrations and rigid-body displacements of the structure. The application of an infinite dimensional Linear Quadratic Gaussian (LQG) control theory to flexible structure is discussed. Two basic approaches for robustness enhancement were investigated: loop transfer recovery and sensitivity optimization. A third approach synthesized from elements of these two basic approaches is currently under development. The control driven finite element approximation of flexible structures is discussed. Three sets of finite element basic vectors for computing functional control gains are compared. The possibility of constructing a finite element scheme to approximate the infinite dimensional Hamiltonian system directly, instead of indirectly is discussed.

Understanding geological processes: Visualization of rigid and non-rigid transformations

NASA Astrophysics Data System (ADS)

Shipley, T. F.; Atit, K.; Manduca, C. A.; Ormand, C. J.; Resnick, I.; Tikoff, B.

2012-12-01

Visualizations are used in the geological sciences to support reasoning about structures and events. Research in cognitive sciences offers insights into the range of skills of different users, and ultimately how visualizations might support different users. To understand the range of skills needed to reason about earth processes we have developed a program of research that is grounded in the geosciences' careful description of the spatial and spatiotemporal patterns associated with earth processes. In particular, we are pursuing a research program that identifies specific spatial skills and investigates whether and how they are related to each other. For this study, we focus on a specific question: Is there an important distinction in the geosciences between rigid and non-rigid deformation? To study a general spatial thinking skill we employed displays with non-geological objects that had been altered by rigid change (rotation), and two types of non-rigid change ("brittle" (or discontinuous) and "ductile" (or continuous) deformation). Disciplinary scientists (geosciences and chemistry faculty), and novices (non-science faculty and undergraduate psychology students) answered questions that required them to visualize the appearance of the object before the change. In one study, geologists and chemists were found to be superior to non-science faculty in reasoning about rigid rotations (e.g., what an object would look like from a different perspective). Geologists were superior to chemists in reasoning about brittle deformations (e.g., what an object looked like before it was broken - here the object was a word cut into many fragments displaced in different directions). This finding is consistent with two hypotheses: 1) Experts are good at visualizing the types of changes required for their domain; and 2) Visualization of rigid and non-rigid changes are not the same skill. An additional important finding is that there was a broad range of skill in both rigid and non-rigid reasoning within the panels of science experts. In a second study, individual differences in reasoning about brittle deformations were correlated with reasoning about ductile deformations (e.g., what a bent plastic sheet would look like when unbent). Students who were good at visualizing what something looked like before it was broken were also good at visualizing what something looked like before it was bent, and this skill was not correlated to reasoning about rigid rotations. These findings suggest the cognitive processes that support reasoning about rigid and non-rigid events may differ and thus may require different types of support and training. We do not know if differences between experts and novices result from experience or self-selection, or both. Nevertheless, the range of spatial skill evinced by novices and experts strongly argues for designing visualizations to support a variety of users.

NEUTRON SHIELDING STRUCTURE

DOEpatents

Mattingly, J.T.

1962-09-25

A lightweight neutron shielding structure comprises a honeycomb core which is filled with a neutron absorbing powder. The honeycomb core is faced with parallel planar facing sheets to form a lightweight rigid unit. Suitable absorber powders are selected from among the following: B, B/sub 4/C, B/sub 2/O/ sub 3/, CaB/sub 6/, Li/sub 2/CO3, LiOH, LiBO/sub 2/, Li/s ub 2/O. The facing sheets are constructed of a neutron moderating material, so that fast neutrons will be moderated while traversing the facing sheets, and ultimately be absorbed by the absorber powder in the honeycomb. Beryllium is a preferred moderator material for use in the facing sheets. The advantage of the structure is that it combines the rigidity and light weight of a honeycomb construction with the neutron absorption properties of boron and lithium. (AEC)

Structural Modeling of a Five-Meter Thin Film Inflatable Antenna/Concentrator With Rigidized Support Struts

NASA Technical Reports Server (NTRS)

Smalley, Kurt B.; Tinker, Michael L.

2001-01-01

Dynamic characterization of a non-rigidized thin film inflatable antenna/solar concentrator structure with rigidized composite support struts is described in detail. A two-step finite element modeling approach in MSC/NASTRAN is utilized, consisting of: (1) a nonlinear static pressurization procedure used to obtain the updated stiffness matrix, and (2) a modal "restart" eigen solution that uses the modified stiffness matrix. Unique problems encountered in modeling of this large 5-m lightweight inflatable are identified, including considerable difficulty in obtaining convergence in the nonlinear pressurization solution. It was found that the extremely thin polyimide film material (.001 in or I mil) presents tremendous problems in obtaining a converged solution when internal pressure loading is applied. It was concluded that the ratios of film thickness to other geometric dimensions such as torus cross-sectional and ring diameter and lenticular diameter are the critical parameters for convergence of the pressurization procedure. Comparison of finite element predictions for frequency and mode shapes with experimental results indicated reasonable agreement considering the complexity of the structure, the film-to-air interaction, and the nonlinear material properties of the film. It was also concluded that analysis should be done using different finite element to codes to determine if a more robust and stable solution can be obtained.

Progressive Stereo Locking (PSL): A Residual Dipolar Coupling Based Force Field Method for Determining the Relative Configuration of Natural Products and Other Small Molecules.

PubMed

Cornilescu, Gabriel; Ramos Alvarenga, René F; Wyche, Thomas P; Bugni, Tim S; Gil, Roberto R; Cornilescu, Claudia C; Westler, William M; Markley, John L; Schwieters, Charles D

2017-08-18

Establishing the relative configuration of a bioactive natural product represents the most challenging part in determining its structure. Residual dipolar couplings (RDCs) are sensitive probes of the relative spatial orientation of internuclear vectors. We adapted a force field structure calculation methodology to allow free sampling of both R and S configurations of the stereocenters of interest. The algorithm uses a floating alignment tensor in a simulated annealing protocol to identify the conformations and configurations that best fit experimental RDC and distance restraints (from NOE and J-coupling data). A unique configuration (for rigid molecules) or a very small number of configurations (for less rigid molecules) of the structural models having the lowest chiral angle energies and reasonable magnitudes of the alignment tensor are provided as the best predictions of the unknown configuration. For highly flexible molecules, the progressive locking of their stereocenters into their statistically dominant R or S state dramatically reduces the number of possible relative configurations. The result is verified by checking that the same configuration is obtained by initiating the locking from different regions of the molecule. For all molecules tested having known configurations (with conformations ranging from mostly rigid to highly flexible), the method accurately determined the correct configuration.

Experimental testing of impact force on rigid and flexible barriers - A comparison

NASA Astrophysics Data System (ADS)

Nagl, Georg; Hübl, Johannes; Chiari, Michael

2016-04-01

The Trattenbach endangers the main western railway track of Austria by floods and debris flows. Three check dams for debris retention were built in the proximal fan area several decades ago. With regard to an improvement of the protective function, these structures have to be renewed. The recent concept of the uppermost barrier is a type of an energy dissipation net structure, stopping debris flows with the ability of self-cleaning by subsequent floods or by machinery employment. The access to the basin is achieved through the slit when the net has been removed. This technical structure consists of a rigid open crown dam with a 4m wide slit. This slit is closed with a flexible net. To verify this protective system, 21 small scale experiments were conducted to test and optimize this new type of Slit Net Dam. To determine the forces on the barrier, in a first setup of experiments the impact forces on a rigid wall with 24 load cells were measured. In the second setup the slit barrier with the net was investigated. On four main cables the anchor forces were measured. In a further setup the basal distance between the channel and lowest net was varied. To study the emptying of the basin and the dosing effect on debris flows.

Broadband cross-polarization-based heteronuclear dipolar recoupling for structural and dynamic NMR studies of rigid and soft solids

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

Kharkov, B. B.; Chizhik, V. I.; Dvinskikh, S. V., E-mail: sergeid@kth.se

2016-01-21

Dipolar recoupling is an essential part of current solid-state NMR methodology for probing atomic-resolution structure and dynamics in solids and soft matter. Recently described magic-echo amplitude- and phase-modulated cross-polarization heteronuclear recoupling strategy aims at efficient and robust recoupling in the entire range of coupling constants both in rigid and highly dynamic molecules. In the present study, the properties of this recoupling technique are investigated by theoretical analysis, spin-dynamics simulation, and experimentally. The resonance conditions and the efficiency of suppressing the rf field errors are examined and compared to those for other recoupling sequences based on similar principles. The experimental datamore » obtained in a variety of rigid and soft solids illustrate the scope of the method and corroborate the results of analytical and numerical calculations. The technique benefits from the dipolar resolution over a wider range of coupling constants compared to that in other state-of-the-art methods and thus is advantageous in studies of complex solids with a broad range of dynamic processes and molecular mobility degrees.« less

Boson peak and Ioffe-Regel criterion in amorphous siliconlike materials: The effect of bond directionality.

PubMed

Beltukov, Y M; Fusco, C; Parshin, D A; Tanguy, A

2016-02-01

The vibrational properties of model amorphous materials are studied by combining complete analysis of the vibration modes, dynamical structure factor, and energy diffusivity with exact diagonalization of the dynamical matrix and the kernel polynomial method, which allows a study of very large system sizes. Different materials are studied that differ only by the bending rigidity of the interactions in a Stillinger-Weber modelization used to describe amorphous silicon. The local bending rigidity can thus be used as a control parameter, to tune the sound velocity together with local bonds directionality. It is shown that for all the systems studied, the upper limit of the Boson peak corresponds to the Ioffe-Regel criterion for transverse waves, as well as to a minimum of the diffusivity. The Boson peak is followed by a diffusivity's increase supported by longitudinal phonons. The Ioffe-Regel criterion for transverse waves corresponds to a common characteristic mean-free path of 5-7 Å (which is slightly bigger for longitudinal phonons), while the fine structure of the vibrational density of states is shown to be sensitive to the local bending rigidity.

Effect of wing flexibility in dragonfly hovering flight

NASA Astrophysics Data System (ADS)

Naidu, Vishal; Young, John; Lai, Joseph

2011-11-01

Dragonflies have two pairs of tandem wings, which can be operated independently. Most studies on tandem wings are based on rigid wings, which is in strong contradiction to the natural, flexible dragonfly wings. The effect of wing flexibility in tandem wings is little known. We carry out a comparative, computational study between rigid and flexible, dragonfly shaped wings for hovering flight. In rigid wings during downstroke, a leading edge vortex (LEV) is formed on the upper surface, which forms a low pressure zone. This conical LEV joins the tip vortex and shortly after the mid downstroke when the wing starts to rotate, these vortices are gradually shed resulting in a drop in lift. The vortex system creates a net downwards momentum in the form of a jet. The flexible wings while in motion deform due to aerodynamic and inertial forces. Since there is a strong interaction between wing deformation and air flow around the deformed wings, flexible wing simulations are carried out using a two way fluid structure interaction. The effect of wing flexibility on the flow structure and the subsequent effect on the aerodynamic forces will be studied and presented.

How does symmetry impact the flexibility of proteins?

PubMed Central

Schulze, Bernd; Sljoka, Adnan; Whiteley, Walter

2014-01-01

It is well known that (i) the flexibility and rigidity of proteins are central to their function, (ii) a number of oligomers with several copies of individual protein chains assemble with symmetry in the native state and (iii) added symmetry sometimes leads to added flexibility in structures. We observe that the most common symmetry classes of protein oligomers are also the symmetry classes that lead to increased flexibility in certain three-dimensional structures—and investigate the possible significance of this coincidence. This builds on the well-developed theory of generic rigidity of body–bar frameworks, which permits an analysis of the rigidity and flexibility of molecular structures such as proteins via fast combinatorial algorithms. In particular, we outline some very simple counting rules and possible algorithmic extensions that allow us to predict continuous symmetry-preserving motions in body–bar frameworks that possess non-trivial point-group symmetry. For simplicity, we focus on dimers, which typically assemble with twofold rotational axes, and often have allosteric function that requires motions to link distant sites on the two protein chains. PMID:24379431

Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station.

PubMed

Aguilar, M; Ali Cavasonza, L; Ambrosi, G; Arruda, L; Attig, N; Aupetit, S; Azzarello, P; Bachlechner, A; Barao, F; Barrau, A; Barrin, L; Bartoloni, A; Basara, L; Başeğmez-du Pree, S; Battarbee, M; Battiston, R; Becker, U; Behlmann, M; Beischer, B; Berdugo, J; Bertucci, B; Bindel, K F; Bindi, V; Boella, G; de Boer, W; Bollweg, K; Bonnivard, V; Borgia, B; Boschini, M J; Bourquin, M; Bueno, E F; Burger, J; Cadoux, F; Cai, X D; Capell, M; Caroff, S; Casaus, J; Castellini, G; Cervelli, F; Chae, M J; Chang, Y H; Chen, A I; Chen, G M; Chen, H S; Cheng, L; Chou, H Y; Choumilov, E; Choutko, V; Chung, C H; Clark, C; Clavero, R; Coignet, G; Consolandi, C; Contin, A; Corti, C; Creus, W; Crispoltoni, M; Cui, Z; Dai, Y M; Delgado, C; Della Torre, S; Demakov, O; Demirköz, M B; Derome, L; Di Falco, S; Dimiccoli, F; Díaz, C; von Doetinchem, P; Dong, F; Donnini, F; Duranti, M; D'Urso, D; Egorov, A; Eline, A; Eronen, T; Feng, J; Fiandrini, E; Finch, E; Fisher, P; Formato, V; Galaktionov, Y; Gallucci, G; García, B; García-López, R J; Gargiulo, C; Gast, H; Gebauer, I; Gervasi, M; Ghelfi, A; Giovacchini, F; Goglov, P; Gómez-Coral, D M; Gong, J; Goy, C; Grabski, V; Grandi, D; Graziani, M; Guo, K H; Haino, S; Han, K C; He, Z H; Heil, M; Hoffman, J; Hsieh, T H; Huang, H; Huang, Z C; Huh, C; Incagli, M; Ionica, M; Jang, W Y; Jinchi, H; Kang, S C; Kanishev, K; Kim, G N; Kim, K S; Kirn, Th; Konak, C; Kounina, O; Kounine, A; Koutsenko, V; Krafczyk, M S; La Vacca, G; Laudi, E; Laurenti, G; Lazzizzera, I; Lebedev, A; Lee, H T; Lee, S C; Leluc, C; Li, H S; Li, J Q; Li, J Q; Li, Q; Li, T X; Li, W; Li, Y; Li, Z H; Li, Z Y; Lim, S; Lin, C H; Lipari, P; Lippert, T; Liu, D; Liu, Hu; Lordello, V D; Lu, S Q; Lu, Y S; Luebelsmeyer, K; Luo, F; Luo, J Z; Lv, S S; Machate, F; Majka, R; Mañá, C; Marín, J; Martin, T; Martínez, G; Masi, N; Maurin, D; Menchaca-Rocha, A; Meng, Q; Mikuni, V M; Mo, D C; Morescalchi, L; Mott, P; Nelson, T; Ni, J Q; Nikonov, N; Nozzoli, F; Oliva, A; Orcinha, M; Palmonari, F; Palomares, C; Paniccia, M; Pauluzzi, M; Pensotti, S; Pereira, R; Picot-Clemente, N; Pilo, F; Pizzolotto, C; Plyaskin, V; Pohl, M; Poireau, V; Putze, A; Quadrani, L; Qi, X M; Qin, X; Qu, Z Y; Räihä, T; Rancoita, P G; Rapin, D; Ricol, J S; Rosier-Lees, S; Rozhkov, A; Rozza, D; Sagdeev, R; Sandweiss, J; Saouter, P; Schael, S; Schmidt, S M; Schulz von Dratzig, A; Schwering, G; Seo, E S; Shan, B S; Shi, J Y; Siedenburg, T; Son, D; Song, J W; Sun, W H; Tacconi, M; Tang, X W; Tang, Z C; Tao, L; Tescaro, D; Ting, Samuel C C; Ting, S M; Tomassetti, N; Torsti, J; Türkoğlu, C; Urban, T; Vagelli, V; Valente, E; Vannini, C; Valtonen, E; Vázquez Acosta, M; Vecchi, M; Velasco, M; Vialle, J P; Vitale, V; Vitillo, S; Wang, L Q; Wang, N H; Wang, Q L; Wang, X; Wang, X Q; Wang, Z X; Wei, C C; Weng, Z L; Whitman, K; Wienkenhöver, J; Wu, H; Wu, X; Xia, X; Xiong, R Q; Xu, W; Yan, Q; Yang, J; Yang, M; Yang, Y; Yi, H; Yu, Y J; Yu, Z Q; Zeissler, S; Zhang, C; Zhang, J; Zhang, J H; Zhang, S D; Zhang, S W; Zhang, Z; Zheng, Z M; Zhu, Z Q; Zhuang, H L; Zhukov, V; Zichichi, A; Zimmermann, N; Zuccon, P

2016-12-02

Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the B/C ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the B/C spectral index is reported for the first time. The B/C ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the B/C ratio is well described by a single power law R^{Δ} with index Δ=-0.333±0.014(fit)±0.005(syst), in good agreement with the Kolmogorov theory of turbulence which predicts Δ=-1/3 asymptotically.

Influence of chain rigidity on the conformation of model lipid membranes in the presence of cylindrical nanoparticle inclusions

NASA Astrophysics Data System (ADS)

Diloreto, Chris; Wickham, Robert

2012-02-01

We employ real-space self-consistent field theory to study the conformation of model lipid membranes in the presence of solvent and cylindrical nanoparticle inclusions (''peptides''). Whereas it is common to employ a polymeric Gaussian chain model for the lipids, here we model the lipids as persistent, worm-like chains. Our motivation is to develop a more realistic field theory to describe the action of pore-forming anti-microbial peptides that disrupt the bacterial cell membrane. We employ operator-splitting and a pseudo-spectral algorithm, using SpharmonicKit for the chain tangent degrees of freedom, to solve for the worm-like chain propagator. The peptides, modelled using a mask function, have a surface patterned with hydrophobic and hydrophillic patches, but no charge. We examine the role chain rigidity plays in the hydrophobic mismatch, the membrane-mediated interaction between two peptides, the size and structure of pores formed by peptide aggregates, and the free-energy barrier for peptide insertion into the membrane. Our results suggest that chain rigidity influences both the pore structure and the mechanism of pore formation.

Assessment of frontal lobe sagging after endoscopic endonasal transcribriform resection of anterior skull base tumors: is rigid structural reconstruction of the cranial base defect necessary?

PubMed

Eloy, Jean Anderson; Shukla, Pratik A; Choudhry, Osamah J; Singh, Rahul; Liu, James K

2012-12-01

The endoscopic endonasal transcribriform approach (EETA) is a viable alternative option for resection of selected anterior skull base (ASB) tumors. However, this technique results in the creation of large cribriform defects. Some have reported the use of a rigid substitute for ASB reconstruction to prevent postoperative frontal lobe sagging. We evaluate the degree of frontal lobe sagging using our triple-layer technique [fascia lata, acellular dermal allograft, and pedicled nasoseptal flap (PNSF)] without the use of rigid structural reconstruction for large cribriform defects. Retrospective analysis. Nine patients underwent an EETA for resection of large ASB tumors from August 2010 to November 2011. The degree of frontal lobe displacement after EETA, defined as the ASB position, was calculated based on the most inferior position of the frontal lobe relative to the nasion-sellar line defined on preoperative and postoperative imaging. A positive value signified upward displacement, and a negative value represented inferior displacement of the frontal lobe. The average cribriform defect size was 9.3 cm(2) (range, 5.0-13.8 cm(2) ). The average distance of postoperative frontal lobe displacement was 0.2 mm (range, -3.9 to 2.9 mm) without any cases of significant brain sagging. The mean follow-up period was 10.1 months (range, 4-19 months). There were no postoperative CSF leaks. Rigid structural repair may not be necessary for ASB defect repair after endoscopic endonasal resection of the cribriform plate. Our technique for multilayer cranial base reconstruction appears to be satisfactory in preventing delayed frontal lobe sagging. Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.

Experimental Study on Surrogate Nuclear Fuel Rods under Reversed Cyclic Bending

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

Wang, Hong; Wang, Jy-An John

The mechanical behavior of spent nuclear fuel (SNF) rods under reversed cyclic bending or bending fatigue must be understood to evaluate their vibration integrity in a transportation environment. This is especially important for high-burnup fuels (>45 GWd/MTU), which have the potential for increased structural damage. It has been demonstrated that the bending fatigue of SNF rods can be effectively studied using surrogate rods. In this investigation, surrogate rods made of stainless steel (SS) 304 cladding and aluminum oxide pellets were tested under load or moment control at a variety of amplitude levels at 5 Hz using the Cyclic Integrated Reversible-Bendingmore » Fatigue Tester developed at Oak Ridge National Laboratory. The behavior of the rods was further characterized using flexural rigidity and hysteresis data, and fractography was performed on the failed rods. The proposed surrogate rods captured many of the characteristics of deformation and failure mode observed in SNF, including the linear-to-nonlinear deformation transition and large residual curvature in static tests, PPI and PCMI failure mechanisms, and large variation in the initial structural condition. Rod degradation was measured and characterized by measuring the flexural rigidity; the degradation of the rigidity depended on both the moment amplitude applied and the initial structural condition of the rods. It was also shown that a cracking initiation site can be located on the internal surface or the external surface of cladding. Finally, fatigue damage to the bending rods can be described in terms of flexural rigidity, and the fatigue life of rods can be predicted once damage model parameters are properly evaluated. The developed experimental approach, test protocol, and analysis method can be used to study the vibration integrity of SNF rods in the future.« less

Effect of replacing polyol by organosolv and kraft lignin on the property and structure of rigid polyurethane foam

PubMed Central

2013-01-01

Background Lignin is one of the three major components in plant cell walls, and it can be isolated (dissolved) from the cell wall in pretreatment or chemical pulping. However, there is a lack of high-value applications for lignin, and the commonest proposal for lignin is power and steam generation through combustion. Organosolv ethanol process is one of the effective pretreatment methods for woody biomass for cellulosic ethanol production, and kraft process is a dominant chemical pulping method in paper industry. In the present research, the lignins from organosolv pretreatment and kraft pulping were evaluated to replace polyol for producing rigid polyurethane foams (RPFs). Results Petroleum-based polyol was replaced with hardwood ethanol organosolv lignin (HEL) or hardwood kraft lignin (HKL) from 25% to 70% (molar percentage) in preparing rigid polyurethane foam. The prepared foams contained 12-36% (w/w) HEL or 9-28% (w/w) HKL. The density, compressive strength, and cellular structure of the prepared foams were investigated and compared. Chain extenders were used to improve the properties of the RPFs. Conclusions It was found that lignin was chemically crosslinked not just physically trapped in the rigid polyurethane foams. The lignin-containing foams had comparable structure and strength up to 25-30% (w/w) HEL or 19-23% (w/w) HKL addition. The results indicated that HEL performed much better in RPFs and could replace more polyol at the same strength than HKL because the former had a better miscibility with the polyol than the latter. Chain extender such as butanediol could improve the strength of lignin-containing RPFs. PMID:23356502

Development of a high-density nonwoven structure to improve the stab resistance of protective clothing material.

PubMed

Bao, Limin; Wang, Yanling; Baba, Takeichiro; Fukuda, Yasuhiro; Wakatsuki, Kaoru; Morikawa, Hideaki

2017-12-07

The purpose of this research was to enhance the stab resistance of protective clothing material by developing a new high-density nonwoven structure. Ice picks often injure Japanese police officers due to the strict regulation of swords in the country. Consequently, this study was designed to improve stab resistance against ice picks. Most existing anti-stab protective clothing research has focused on various fabrics impregnated with resin, an approach that brings with it problems of high cost and complicated processing. Seldom has research addressed the potential for improving stab resistance by using nonwoven structures, which exhibit better stab resistance than fabric. In this research, we prepared a series of nonwoven structures with densities ranging from about 0.14 g/cm 3 to 0.46 g/cm 3 by varying the number of stacked layers of Kevlar/polyester nonwoven under a hot press. We then proposed two methods for producing such hot-press nonwovens: the multilayer hot-press method and the monolayer hot-press method. Stab resistance was evaluated according to NIJ Standard-0115.00. We also investigated the relationship among nonwoven density, stab resistance, and flexural rigidity, and here we discuss the respective properties of the two proposed methods. Our results show that stab resistance and flexural rigidity increase with nonwoven density, but flexural rigidity of nonwovens prepared using the monolayer hot-press method only shows a slight change as nonwoven density increases. Though the two methods exhibit little difference in maximum load, the flexural rigidity of nonwovens prepared using the monolayer hot-press method is much lower, which contributes to superior wear comfort. Finally, we investigated the mechanism behind the stabbing process. Stabbing with an ice pick is a complicated process that involves many factors. Our findings indicate that nonwovens stop penetration primarily in two ways: nonwoven deformation and fiber fractures.

Development of a high-density nonwoven structure to improve the stab resistance of protective clothing material

PubMed Central

BAO, Limin; WANG, Yanling; BABA, Takeichiro; FUKUDA, Yasuhiro; WAKATSUKI, Kaoru; MORIKAWA, Hideaki

2017-01-01

The purpose of this research was to enhance the stab resistance of protective clothing material by developing a new high-density nonwoven structure. Ice picks often injure Japanese police officers due to the strict regulation of swords in the country. Consequently, this study was designed to improve stab resistance against ice picks. Most existing anti-stab protective clothing research has focused on various fabrics impregnated with resin, an approach that brings with it problems of high cost and complicated processing. Seldom has research addressed the potential for improving stab resistance by using nonwoven structures, which exhibit better stab resistance than fabric. In this research, we prepared a series of nonwoven structures with densities ranging from about 0.14 g/cm3 to 0.46 g/cm3 by varying the number of stacked layers of Kevlar/polyester nonwoven under a hot press. We then proposed two methods for producing such hot-press nonwovens: the multilayer hot-press method and the monolayer hot-press method. Stab resistance was evaluated according to NIJ Standard-0115.00. We also investigated the relationship among nonwoven density, stab resistance, and flexural rigidity, and here we discuss the respective properties of the two proposed methods. Our results show that stab resistance and flexural rigidity increase with nonwoven density, but flexural rigidity of nonwovens prepared using the monolayer hot-press method only shows a slight change as nonwoven density increases. Though the two methods exhibit little difference in maximum load, the flexural rigidity of nonwovens prepared using the monolayer hot-press method is much lower, which contributes to superior wear comfort. Finally, we investigated the mechanism behind the stabbing process. Stabbing with an ice pick is a complicated process that involves many factors. Our findings indicate that nonwovens stop penetration primarily in two ways: nonwoven deformation and fiber fractures. PMID:28978816

Structural modulation and luminescent properties of four CdII coordination architectures based on 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole and flexible/rigid dicarboxylate ligands

NASA Astrophysics Data System (ADS)

Xia, Liang; Dong, Wen-Wen; Ye, Xiao; Zhao, Jun; Li, Dong-Sheng

2016-10-01

To systematically investigate the influence of the flexible or rigid auxiliary ligands on the structures and properties of transition metal compounds, we synthesized four new d10 coordination polymers (CPs) from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) and flexible/rigid dicarboxylate ligands, [Cd(4-pzpt)2]n (1), [Cd3(4-pzpt)2(suc)2]n (2), [Cd2(4-Hpzpt)(nbc)2(H2O)]n (3) and {[Cd2(4-pzpt)2(tfbdc)(H2O)4]·H2O}n (4) (H2suc=1,2-ethanedicarboxylic acid, H2nbc=hthalene-1,4-dicarboxylic acid, H2tfbdc =2,3,5,6-tetrafluoroterephthalic acid). Single crystal X-ray analysis indicates that compound 1 shows a 44-sql layer, which is extended to a 3D network via nonclassical C-H…N hydrogen bonds. Compound 2 possesses a 6-connected pcu-4120.63 net composed of trinuclear CdII-clusters. Compound 3 represents a rare 3D (3,4,4,5)-connected topology with a Schläfli symbol of (4·6·7)(4·53·72)(53·6·7·9)(42·55·6·72). Compound 4 exhibits a 2D+2D→2D parallel interpenetrated 63-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting 3D supramolecular architecture through classical O-H…N and O-H…O hydrogen bonds. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. Moreover, the luminescent properties of them have been briefly investigated.

Computational Modeling of Allosteric Regulation in the Hsp90 Chaperones: A Statistical Ensemble Analysis of Protein Structure Networks and Allosteric Communications

PubMed Central

Blacklock, Kristin; Verkhivker, Gennady M.

2014-01-01

A fundamental role of the Hsp90 chaperone in regulating functional activity of diverse protein clients is essential for the integrity of signaling networks. In this work we have combined biophysical simulations of the Hsp90 crystal structures with the protein structure network analysis to characterize the statistical ensemble of allosteric interaction networks and communication pathways in the Hsp90 chaperones. We have found that principal structurally stable communities could be preserved during dynamic changes in the conformational ensemble. The dominant contribution of the inter-domain rigidity to the interaction networks has emerged as a common factor responsible for the thermodynamic stability of the active chaperone form during the ATPase cycle. Structural stability analysis using force constant profiling of the inter-residue fluctuation distances has identified a network of conserved structurally rigid residues that could serve as global mediating sites of allosteric communication. Mapping of the conformational landscape with the network centrality parameters has demonstrated that stable communities and mediating residues may act concertedly with the shifts in the conformational equilibrium and could describe the majority of functionally significant chaperone residues. The network analysis has revealed a relationship between structural stability, global centrality and functional significance of hotspot residues involved in chaperone regulation. We have found that allosteric interactions in the Hsp90 chaperone may be mediated by modules of structurally stable residues that display high betweenness in the global interaction network. The results of this study have suggested that allosteric interactions in the Hsp90 chaperone may operate via a mechanism that combines rapid and efficient communication by a single optimal pathway of structurally rigid residues and more robust signal transmission using an ensemble of suboptimal multiple communication routes. This may be a universal requirement encoded in protein structures to balance the inherent tension between resilience and efficiency of the residue interaction networks. PMID:24922508

Computational modeling of allosteric regulation in the hsp90 chaperones: a statistical ensemble analysis of protein structure networks and allosteric communications.

PubMed

Blacklock, Kristin; Verkhivker, Gennady M

2014-06-01

A fundamental role of the Hsp90 chaperone in regulating functional activity of diverse protein clients is essential for the integrity of signaling networks. In this work we have combined biophysical simulations of the Hsp90 crystal structures with the protein structure network analysis to characterize the statistical ensemble of allosteric interaction networks and communication pathways in the Hsp90 chaperones. We have found that principal structurally stable communities could be preserved during dynamic changes in the conformational ensemble. The dominant contribution of the inter-domain rigidity to the interaction networks has emerged as a common factor responsible for the thermodynamic stability of the active chaperone form during the ATPase cycle. Structural stability analysis using force constant profiling of the inter-residue fluctuation distances has identified a network of conserved structurally rigid residues that could serve as global mediating sites of allosteric communication. Mapping of the conformational landscape with the network centrality parameters has demonstrated that stable communities and mediating residues may act concertedly with the shifts in the conformational equilibrium and could describe the majority of functionally significant chaperone residues. The network analysis has revealed a relationship between structural stability, global centrality and functional significance of hotspot residues involved in chaperone regulation. We have found that allosteric interactions in the Hsp90 chaperone may be mediated by modules of structurally stable residues that display high betweenness in the global interaction network. The results of this study have suggested that allosteric interactions in the Hsp90 chaperone may operate via a mechanism that combines rapid and efficient communication by a single optimal pathway of structurally rigid residues and more robust signal transmission using an ensemble of suboptimal multiple communication routes. This may be a universal requirement encoded in protein structures to balance the inherent tension between resilience and efficiency of the residue interaction networks.

Topological classification of the Goryachev integrable case in rigid body dynamics

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

Nikolaenko, S S

2016-01-31

A topological analysis of the Goryachev integrable case in rigid body dynamics is made on the basis of the Fomenko-Zieschang theory. The invariants (marked molecules) which are obtained give a complete description, from the standpoint of Liouville classification, of the systems of Goryachev type on various level sets of the energy. It turns out that on appropriate energy levels the Goryachev case is Liouville equivalent to many classical integrable systems and, in particular, the Joukowski, Clebsch, Sokolov and Kovalevskaya-Yehia cases in rigid body dynamics, as well as to some integrable billiards in plane domains bounded by confocal quadrics -- in othermore » words, the foliations given by the closures of generic solutions of these systems have the same structure. Bibliography: 15 titles.« less

Simulation of vortex-induced vibrations of a cylinder using ANSYS CFX rigid body solver

NASA Astrophysics Data System (ADS)

Izhar, Abubakar; Qureshi, Arshad Hussain; Khushnood, Shahab

2017-03-01

This article simulates the vortex-induced oscillations of a rigid circular cylinder with elastic support using the new ANSYS CFX rigid body solver. This solver requires no solid mesh to setup FSI (Fluid Structure Interaction) simulation. The two-way case was setup in CFX only. Specific mass of the cylinder and flow conditions were similar to previous experimental data with mass damping parameter equal to 0.04, specific mass of 1 and Reynolds number of 3800. Two dimensional simulations were setup. Both one-degree-of-freedom and two-degree-of-freedom cases were run and results were obtained for both cases with reasonable accuracy as compared with experimental results. Eight-figure XY trajectory and lock-in behavior were clearly captured. The obtained results were satisfactory.

40 CFR 165.87 - Design and capacity requirements for existing structures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Design and capacity requirements for... Structures § 165.87 Design and capacity requirements for existing structures. (a) For all existing... concrete or other rigid material capable of withstanding the full hydrostatic head, load and impact of any...

Wood : mechanical fasteners

Treesearch

Douglas R. Rammer

2001-01-01

The strength and stability of any structure depends heavily on the fasteners that hold its parts together. One prime advantage of wood as a structural material is the ease with which wood structural parts can be joined together using a wide variety of fasteners: nails, staples, screws, lag screws, bolts, and various types of metal connectors. For the utmost rigidity,...

Heat treatment stabilizes welded aluminum jigs and tool structures

NASA Technical Reports Server (NTRS)

Mehnert, R. S.

1966-01-01

Heat treatment processes, applied after welding but before machining, imparts above normal stability to welded aluminum jigs and tool structures. Weight saving will not be realized in these tools if rigidity equal to that of a comparable steel tool is required.

Non-Axisymmetric Inflatable Pressure Structure (NAIPS) Full-Scale Pressure Test

NASA Technical Reports Server (NTRS)

Jones, Thomas C.; Doggett, William R.; Warren, Jerry E.; Watson, Judith J.; Shariff, Khadijah; Makino, Alberto; Yount, Bryan C.

2017-01-01

Inflatable space structures have the potential to significantly reduce the required launch volume for large pressure vessels required for exploration applications including habitats, airlocks and tankage. In addition, mass savings can be achieved via the use of high specific strength softgoods materials, and the reduced design penalty from launching the structure in a densely packaged state. Large inclusions however, such as hatches, induce a high mass penalty at the interfaces with the softgoods and in the added rigid structure while reducing the packaging efficiency. A novel, Non-Axisymmetric Inflatable Pressure Structure (NAIPS) was designed and recently tested at NASA Langley Research Center to demonstrate an elongated inflatable architecture that could provide areas of low stress along a principal axis in the surface. These low stress zones will allow the integration of a flexible linear seal that substantially reduces the added mass and volume of a heritage rigid hatch structure. This paper describes the test of the first full-scale engineering demonstration unit (EDU) of the NAIPS geometry and a comparison of the results to finite element analysis.

High-temperature zirconia insulation and method for making same

DOEpatents

Wrenn, G.E. Jr.; Holcombe, C.E. Jr.; Lewis, J. Jr.

1988-05-10

The present invention is directed to a highly pure, partially stabilized, fibrous zirconia composite for use as thermal insulation in environments where temperatures up to about 2,000 C are utilized. The composite of the present invention is fabricated into any suitable configuration such as a cone, cylinder, dome or the like by vacuum molding an aqueous slurry of partially stabilized zirconia fibers into a desired configuration on a suitably shaped mandrel. The molded fibers are infiltrated with zirconyl nitrate and the resulting structure is then dried to form a rigid structure which may be removed and placed in a furnace. The structure is then heated in air to a temperature of about 600 C for driving off the nitrate from the structure and for oxidizing the zirconyl ion to zirconia. Thereafter, the structure is heated to about 950 to 1,250 C to fuse the zirconia fibers at their nexi in a matrix of zirconia. The composite produced by the present invention is self-supporting and can be readily machined to desired final dimensions. Additional heating to about 1,800 to 2,000 C further improves structural rigidity.

Thermally-Induced Structural Disturbances of Rigid Panel Solar Arrays

NASA Technical Reports Server (NTRS)

Johnston, John D.; Thornton, Earl A.

1997-01-01

The performance of a significant number of spacecraft has been impacted negatively by attitude disturbances resulting from thermally-induced motions of flexible structures. Recent examples of spacecraft affected by these disturbances include the Hubble Space Telescope (HST) and the Upper Atmosphere Research Satellite (UARS). Thermally-induced structural disturbances occur as the result of rapid changes in thermal loading typically initiated as a satellite exits or enters the Earth's shadow. Temperature differences in flexible appendages give rise to structural deformations, which in turn result in disturbance torques reacting back on the spacecraft. Structures which have proven susceptible to these disturbances include deployable booms and solar arrays. This paper investigates disturbances resulting from thermally-induced deformations of rigid panel solar arrays. An analytical model for the thermal-structural response of the solar array and the corresponding disturbance torque are presented. The effect of these disturbances on the attitude dynamics of a simple spacecraft is then investigated using a coupled system of governing equations which includes the effects of thermally-induced deformations. Numerical results demonstrate the effect of varying solar array geometry on the dynamic response of the system.

Automatic construction of patient-specific finite-element mesh of the spine from IVDs and vertebra segmentations

NASA Astrophysics Data System (ADS)

Castro-Mateos, Isaac; Pozo, Jose M.; Lazary, Aron; Frangi, Alejandro F.

2016-03-01

Computational medicine aims at developing patient-specific models to help physicians in the diagnosis and treatment selection for patients. The spine, and other skeletal structures, is an articulated object, composed of rigid bones (vertebrae) and non-rigid parts (intervertebral discs (IVD), ligaments and muscles). These components are usually extracted from different image modalities, involving patient repositioning. In the case of the spine, these models require the segmentation of IVDs from MR and vertebrae from CT. In the literature, there exists a vast selection of segmentations methods, but there is a lack of approaches to align the vertebrae and IVDs. This paper presents a method to create patient-specific finite element meshes for biomechanical simulations, integrating rigid and non-rigid parts of articulated objects. First, the different parts are aligned in a complete surface model. Vertebrae extracted from CT are rigidly repositioned in between the IVDs, initially using the IVDs location and then refining the alignment using the MR image with a rigid active shape model algorithm. Finally, a mesh morphing algorithm, based on B-splines, is employed to map a template finite-element (volumetric) mesh to the patient-specific surface mesh. This morphing reduces possible misalignments and guarantees the convexity of the model elements. Results show that the accuracy of the method to align vertebrae into MR, together with IVDs, is similar to that of the human observers. Thus, this method is a step forward towards the automation of patient-specific finite element models for biomechanical simulations.

Rigid Residue Scan Simulations Systematically Reveal Residue Entropic Roles in Protein Allostery

PubMed Central

Liu, Jin

2016-01-01

Intra-protein information is transmitted over distances via allosteric processes. This ubiquitous protein process allows for protein function changes due to ligand binding events. Understanding protein allostery is essential to understanding protein functions. In this study, allostery in the second PDZ domain (PDZ2) in the human PTP1E protein is examined as model system to advance a recently developed rigid residue scan method combining with configurational entropy calculation and principal component analysis. The contributions from individual residues to whole-protein dynamics and allostery were systematically assessed via rigid body simulations of both unbound and ligand-bound states of the protein. The entropic contributions of individual residues to whole-protein dynamics were evaluated based on covariance-based correlation analysis of all simulations. The changes of overall protein entropy when individual residues being held rigid support that the rigidity/flexibility equilibrium in protein structure is governed by the La Châtelier’s principle of chemical equilibrium. Key residues of PDZ2 allostery were identified with good agreement with NMR studies of the same protein bound to the same peptide. On the other hand, the change of entropic contribution from each residue upon perturbation revealed intrinsic differences among all the residues. The quasi-harmonic and principal component analyses of simulations without rigid residue perturbation showed a coherent allosteric mode from unbound and bound states, respectively. The projection of simulations with rigid residue perturbation onto coherent allosteric modes demonstrated the intrinsic shifting of ensemble distributions supporting the population-shift theory of protein allostery. Overall, the study presented here provides a robust and systematic approach to estimate the contribution of individual residue internal motion to overall protein dynamics and allostery. PMID:27115535

Structures of BmrR-Drug Complexes Reveal a Rigid Multidrug Binding Pocket And Transcription Activation Through Tyrosine Expulsion

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

Newberry, K.J.; Huffman, J.L.; Miller, M.C.

2009-05-22

BmrR is a member of the MerR family and a multidrug binding transcription factor that up-regulates the expression of the bmr multidrug efflux transporter gene in response to myriad lipophilic cationic compounds. The structural mechanism by which BmrR binds these chemically and structurally different drugs and subsequently activates transcription is poorly understood. Here, we describe the crystal structures of BmrR bound to rhodamine 6G (R6G) or berberine (Ber) and cognate DNA. These structures reveal each drug stacks against multiple aromatic residues with their positive charges most proximal to the carboxylate group of Glu-253 and that, unlike other multidrug binding pockets,more » that of BmrR is rigid. Substitution of Glu-253 with either alanine (E253A) or glutamine (E253Q) results in unpredictable binding affinities for R6G, Ber, and tetraphenylphosphonium. Moreover, these drug binding studies reveal that the negative charge of Glu-253 is not important for high affinity binding to Ber and tetraphenylphosphonium but plays a more significant, but unpredictable, role in R6G binding. In vitro transcription data show that E253A and E253Q are constitutively active, and structures of the drug-free E253A-DNA and E253Q-DNA complexes support a transcription activation mechanism requiring the expulsion of Tyr-152 from the multidrug binding pocket. In sum, these data delineate the mechanism by which BmrR binds lipophilic, monovalent cationic compounds and suggest the importance of the redundant negative electrostatic nature of this rigid drug binding pocket that can be used to discriminate against molecules that are not substrates of the Bmr multidrug efflux pump.« less

Biophysical characterization of the structural change of Nopp140, an intrinsically disordered protein, in the interaction with CK2α

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

Na, Jung-Hyun; Biomedical Research Institute, Korea Institute of Science and Technology, Seoul 02792; Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760

2016-08-19

Nucleolar phosphoprotein 140 (Nopp140) is a nucleolar protein, more than 80% of which is disordered. Previous studies have shown that the C-terminal region of Nopp140 (residues 568–596) interacts with protein kinase CK2α, and inhibits the catalytic activity of CK2. Although the region of Nopp140 responsible for the interaction with CK2α was identified, the structural features and the effect of this interaction on the structure of Nopp140 have not been defined due to the difficulty of structural characterization of disordered protein. In this study, the disordered feature of Nopp140 and the effect of CK2α on the structure of Nopp140 were examinedmore » using single-molecule fluorescence resonance energy transfer (smFRET) and electron paramagnetic resonance (EPR). The interaction with CK2α was increased conformational rigidity of the CK2α-interacting region of Nopp140 (Nopp140C), suggesting that the disordered and flexible conformation of Nopp140C became more rigid conformation as it binds to CK2α. In addition, site specific spin labeling and EPR analysis confirmed that the residues 574–589 of Nopp140 are critical for binding to CK2α. Similar technical approaches can be applied to analyze the conformational changes in other IDPs during their interactions with binding partners. - Highlights: • Nopp140 is intrinsically disordered protein (IDP). • Conformation of Nopp140 became more rigid conformation due to interaction with CK2α. • smFRET and EPR could be applied to analyze the structural changes of IDPs.« less

Chaotic sources of noise in machine acoustics

NASA Astrophysics Data System (ADS)

Moon, F. C., Prof.; Broschart, Dipl.-Ing. T.

1994-05-01

In this paper a model is posited for deterministic, random-like noise in machines with sliding rigid parts impacting linear continuous machine structures. Such problems occur in gear transmission systems. A mathematical model is proposed to explain the random-like structure-borne and air-borne noise from such systems when the input is a periodic deterministic excitation of the quasi-rigid impacting parts. An experimental study is presented which supports the model. A thin circular plate is impacted by a chaotically vibrating mass excited by a sinusoidal moving base. The results suggest that the plate vibrations might be predicted by replacing the chaotic vibrating mass with a probabilistic forcing function. Prechaotic vibrations of the impacting mass show classical period doubling phenomena.

Liquid-permeable electrode

DOEpatents

Folser, George R.

1980-01-01

Electrodes for use in an electrolytic cell, which are liquid-permeable and have low electrical resistance and high internal surface area are provided of a rigid, porous, carbonaceous matrix having activated carbon uniformly embedded throughout. The activated carbon may be catalyzed with platinum for improved electron transfer between electrode and electrolyte. Activated carbon is mixed with a powdered thermosetting phenolic resin and compacted to the desired shape in a heated mold to melt the resin and form the green electrode. The compact is then heated to a pyrolyzing temperature to carbonize and volatilize the resin, forming a rigid, porous structure. The permeable structure and high internal surface area are useful in electrolytic cells where it is necessary to continuously remove the products of the electrochemical reaction.

Light-Curing Adhesive Repair Tapes

NASA Technical Reports Server (NTRS)

Allred, Ronald; Haight, Andrea Hoyt

2009-01-01

Adhesive tapes, the adhesive resins of which can be cured (and thereby rigidized) by exposure to ultraviolet and/or visible light, are being developed as repair patch materials. The tapes, including their resin components, consist entirely of solid, low-outgassing, nonhazardous or minimally hazardous materials. They can be used in air or in vacuum and can be cured rapidly, even at temperatures as low as -20 C. Although these tapes were originally intended for use in repairing structures in outer space, they can also be used on Earth for quickly repairing a wide variety of structures. They can be expected to be especially useful in situations in which it is necessary to rigidize tapes after wrapping them around or pressing them onto the parts to be repaired.

Impact of inhomogeneity on SH-type wave propagation in an initially stressed composite structure

NASA Astrophysics Data System (ADS)

Saha, S.; Chattopadhyay, A.; Singh, A. K.

2018-02-01

The present analysis has been made on the influence of distinct form of inhomogeneity in a composite structure comprised of double superficial layers lying over a half-space, on the phase velocity of SH-type wave propagating through it. Propagation of SH-type wave in the said structure has been examined in four distinct cases of inhomogeneity viz. when inhomogeneity in double superficial layer is due to exponential variation in density only (Case I); when inhomogeneity in double superficial layers is due to exponential variation in rigidity only (Case II); when inhomogeneity in double superficial layer is due to exponential variation in rigidity, density and initial stress (Case III) and when inhomogeneity in double superficial layer is due to linear variation in rigidity, density and initial stress (Case IV). Closed-form expression of dispersion relation has been accomplished for all four aforementioned cases through extensive application of Debye asymptotic analysis. Deduced dispersion relations for all the cases are found in well-agreement to the classical Love-wave equation. Numerical computation has been carried out to graphically demonstrate the effect of inhomogeneity parameters, initial stress parameters as well as width ratio associated with double superficial layers in the composite structure for each of the four aforesaid cases on dispersion curve. Meticulous examination of distinct cases of inhomogeneity and initial stress in context of considered problem has been carried out with detailed analysis in a comparative approach.

Out-of-plane (SH) soil-structure interaction: a shear wall with rigid and flexible ring foundation

NASA Astrophysics Data System (ADS)

Le, Thang; Lee, Vincent W.; Luo, Hao

2016-02-01

Soil-structure interaction (SSI) of a building and shear wall above a foundation in an elastic half-space has long been an important research subject for earthquake engineers and strong-motion seismologists. Numerous papers have been published since the early 1970s; however, very few of these papers have analytic closed-form solutions available. The soil-structure interaction problem is one of the most classic problems connecting the two disciplines of earthquake engineering and civil engineering. The interaction effect represents the mechanism of energy transfer and dissipation among the elements of the dynamic system, namely the soil subgrade, foundation, and superstructure. This interaction effect is important across many structure, foundation, and subgrade types but is most pronounced when a rigid superstructure is founded on a relatively soft lower foundation and subgrade. This effect may only be ignored when the subgrade is much harder than a flexible superstructure: for instance a flexible moment frame superstructure founded on a thin compacted soil layer on top of very stiff bedrock below. This paper will study the interaction effect of the subgrade and the superstructure. The analytical solution of the interaction of a shear wall, flexible-rigid foundation, and an elastic half-space is derived for incident SH waves with various angles of incidence. It found that the flexible ring (soft layer) cannot be used as an isolation mechanism to decouple a superstructure from its substructure resting on a shaking half-space.

LS-align: an atom-level, flexible ligand structural alignment algorithm for high-throughput virtual screening.

PubMed

Hu, Jun; Liu, Zi; Yu, Dong-Jun; Zhang, Yang

2018-02-15

Sequence-order independent structural comparison, also called structural alignment, of small ligand molecules is often needed for computer-aided virtual drug screening. Although many ligand structure alignment programs are proposed, most of them build the alignments based on rigid-body shape comparison which cannot provide atom-specific alignment information nor allow structural variation; both abilities are critical to efficient high-throughput virtual screening. We propose a novel ligand comparison algorithm, LS-align, to generate fast and accurate atom-level structural alignments of ligand molecules, through an iterative heuristic search of the target function that combines inter-atom distance with mass and chemical bond comparisons. LS-align contains two modules of Rigid-LS-align and Flexi-LS-align, designed for rigid-body and flexible alignments, respectively, where a ligand-size independent, statistics-based scoring function is developed to evaluate the similarity of ligand molecules relative to random ligand pairs. Large-scale benchmark tests are performed on prioritizing chemical ligands of 102 protein targets involving 1,415,871 candidate compounds from the DUD-E (Database of Useful Decoys: Enhanced) database, where LS-align achieves an average enrichment factor (EF) of 22.0 at the 1% cutoff and the AUC score of 0.75, which are significantly higher than other state-of-the-art methods. Detailed data analyses show that the advanced performance is mainly attributed to the design of the target function that combines structural and chemical information to enhance the sensitivity of recognizing subtle difference of ligand molecules and the introduces of structural flexibility that help capture the conformational changes induced by the ligand-receptor binding interactions. These data demonstrate a new avenue to improve the virtual screening efficiency through the development of sensitive ligand structural alignments. http://zhanglab.ccmb.med.umich.edu/LS-align/. njyudj@njust.edu.cn or zhng@umich.edu. Supplementary data are available at Bioinformatics online.

Structure of an electric double layer containing a 2:2 valency dimer electrolyte

DOE PAGES

Silvestre-Alcantara, Whasington; Henderson, Douglas; Wu, Jianzhong; ...

2014-12-05

In this study, the structure of a planar electric double layer formed by a 2:2 valency dimer electrolyte in the vicinity of a uniformly charged planar hard electrode is investigated using density functional theory and Monte Carlo simulations. The dimer electrolyte consists of a mixture of charged divalent dimers and charged divalent monomers in a dielectric continuum. A dimer is constructed by two tangentially tethered rigid spheres, one of which is divalent and positively charged and the other neutral, whereas the monomer is a divalent and negatively charged rigid sphere. The density functional theory reproduces well the simulation results formore » (i) the singlet distributions of the various ion species with respect to the electrode, and (ii) the mean electrostatic potential. Lastly, comparison with earlier results for a 2:1/1:2 dimer electrolyte shows that the double layer structure is similar when the counterion has the same valency.« less

System among the corticosteroids: specificity and molecular dynamics

PubMed Central

Brookes, Jennifer C.; Galigniana, Mario D.; Harker, Anthony H.; Stoneham, A. Marshall; Vinson, Gavin P.

2012-01-01

Understanding how structural features determine specific biological activities has often proved elusive. With over 161 000 steroid structures described, an algorithm able to predict activity from structural attributes would provide manifest benefits. Molecular simulations of a range of 35 corticosteroids show striking correlations between conformational mobility and biological specificity. Thus steroid ring A is important for glucocorticoid action, and is rigid in the most specific (and potent) examples, such as dexamethasone. By contrast, ring C conformation is important for the mineralocorticoids, and is rigid in aldosterone. Other steroids that are less specific, or have mixed functions, or none at all, are more flexible. One unexpected example is 11-deoxycorticosterone, which the methods predict (and our activity studies confirm) is not only a specific mineralocorticoid, but also has significant glucocorticoid activity. These methods may guide the design of new corticosteroid agonists and antagonists. They will also have application in other examples of ligand–receptor interactions. PMID:21613285

Formation metrology and control for large separated optics space telescopes

NASA Technical Reports Server (NTRS)

Mettler, E.; Quadrelli, M.; Breckenridge, W.

2002-01-01

In this paper we present formation flying performance analysis initial results for a representative large space telescope composed of separated optical elements [Mett 02]. A virtual-structure construct (an equivalent rigid body) is created by unique metrology and control that combines both centralized and decentralized methods. The formation may be in orbit at GEO for super-resolution Earth observation, as in the case of Figure 1, or it may be in an Earth-trailing orbit for astrophysics, Figure 2. Extended applications are envisioned for exo-solar planet interferometric imaging by a formation of very large separated optics telescopes, Figure 3. Space telescopes, with such large apertures and f/10 to f/100 optics, are not feasible if connected by massive metering structures. Instead, the new virtual-structure paradigm of information and control connectivity between the formation elements provides the necessary spatial rigidity and alignment precision for the telescope.

Au133(SPh-tBu)52 Nanomolecules: X-ray Crystallography, Optical, Electrochemical, and Theoretical Analysis

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

Dass, Amala; Theivendran, Shevanuja; Nimmala, Praneeth Reddy

2015-04-15

Crystal structure determination has revolutionized modern science in biology, chemistry, and physics. However, the difficulty in obtaining periodic crystal lattices which are needed for X-ray crystal analysis has hindered the determination of atomic structure in nanomaterials, known as the “nanostructure problem”. Here, by using rigid and bulky ligands, we have overcome this limitation and successfully solved the X-ray crystallographic structure of the largest reported thiolated gold nanomolecule, Au133S52. The total composition, Au133(SPh-tBu)52, was verified using high resolution electrospray ionization mass spectrometry (ESI-MS). The experimental and simulated optical spectra show an emergent surface plasmon resonance that is more pronounced than inmore » the slightly larger Au144(SCH2CH2Ph)60. Theoretical analysis indicates that the presence of rigid and bulky ligands is the key to the successful crystal formation.« less

Au 133 (SPh - t Bu) 52 Nanomolecules: X-ray Crystallography, Optical, Electrochemical, and Theoretical Analysis

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

Dass, Amala; Theivendran, Shevanuja; Nimmala, Praneeth Reddy

2015-04-15

Crystal structure determination has revolutionized modern science in biology, chemistry, and physics. However, the difficulty in obtaining periodic crystal lattices which are needed for X-ray crystal analysis has hindered the determination of atomic structure in nanomaterials, known as the "nanostructure problem". Here, by using rigid and bulky ligands, we have overcome this limitation and successfully solved the X-ray crystallographic structure of the largest reported thiolated gold nanomolecule, Au133S52. The total composition, Au-133(SPh-tBu)(52), was verified using high resolution electrospray ionization mass spectrometry (ESI-MS). The experimental and simulated optical spectra show an emergent surface plasmon resonance that is more pronounced than inmore » the slightly larger Au-144(SCH2CH2Ph)(60). Theoretical analysis indicates that the presence of rigid and bulky ligands is the key to the successful crystal formation.« less

Rigidity and pH dependent Morphology of Beta-Lactoglobulin Spherulites

NASA Astrophysics Data System (ADS)

Gayetsky, Lisa; Armstead, Douglas

2008-03-01

Beta-Lactoglobulin is a milk protein that will denature in acidic solution (less than 2.0 pH) and if heated for extended periods (greater than 18 hours) it will form radial structures called Spherulites. Spherulites, along with the amyloid fibrils that compose them, are of practical importance because they form in the human body and cause the amyloidosis diseases. Different amyloidosis are caused by different types of denatured proteins occurring in different parts of the body. Since it is believed that Spherulite formation is a generic protein characteristic, Beta-Lactoglobulin is a legitimate and easy to use protein to study these structures. In this study we are quantifying the shape of Beta-Lactoglobulin Spherulites to determine if the pH of the protein solution has an impact on the morphology due to side chain interactions or other causes. We are also testing the rigidity of these structures to determine the relevance of small shape changes.

Bistable electroactive polymers (BSEP): large-strain actuation of rigid polymers

NASA Astrophysics Data System (ADS)

Yu, Zhibin; Niu, Xiaofan; Brochu, Paul; Yuan, Wei; Li, Huafeng; Chen, Bin; Pei, Qibing

2010-04-01

Reversible, large-strain, bistable actuation has been a lasting puzzle in the pursuit of smart materials and structures. Conducting polymers are bistable, but the achievable strain is small. Large deformations have been achieved in dielectric elastomers at the expense of mechanical strength. The gel or gel-like soft polymers generally have elastic moduli around or less than 10 MPa. The deformed polymer relaxes to its original shape once the applied electric field is removed. We report new, bistable electroactive polymers (BSEP) that are capable of electrically actuated strains as high as 335% area strain. The BSEP could be useful for constructing rigid structures. The structures can support high mechanical loads, and be actuated to large-strain deformations. We will present one unique application of the BSEP for Braille displays that can be quickly refreshed and maintain the displayed contents without a bias voltage.

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

Lee, Hak-Sung, E-mail: hslee@kims.re.kr; Park, Chanbum; Oh, Chang-Seok

Highlights: • We model the sample grain boundary of LiCoO2, one of important Li cathode materials. • Rigid body translation was found the asymmetric GB is more stable than symmetric GB. • The vacancy formation energy of Li and O was estimated with first principles calculations. • This model boundary can help to find a new dopant to improve Li diffusions. - Abstract: An atomic structure of LiCoO{sub 2} model grain boundary, Σ2 [1120](1102), is introduced and grain boundary energies with rigid body translations are investigated systematically to find the most stable interface structures. It is found that the coordinatedmore » structures of Co and O in the vicinity of grain boundary are strongly related to grain boundary energy. Examining nonstoichiometry at grain boundary, the defect energetics of Li and O site at grain boundary are estimated. In addition, the effect of grain boundary on Li diffusion is investigated to calculate Li diffusion across grain boundary.« less

Rigid-Docking Approaches to Explore Protein-Protein Interaction Space.

PubMed

Matsuzaki, Yuri; Uchikoga, Nobuyuki; Ohue, Masahito; Akiyama, Yutaka

Protein-protein interactions play core roles in living cells, especially in the regulatory systems. As information on proteins has rapidly accumulated on publicly available databases, much effort has been made to obtain a better picture of protein-protein interaction networks using protein tertiary structure data. Predicting relevant interacting partners from their tertiary structure is a challenging task and computer science methods have the potential to assist with this. Protein-protein rigid docking has been utilized by several projects, docking-based approaches having the advantages that they can suggest binding poses of predicted binding partners which would help in understanding the interaction mechanisms and that comparing docking results of both non-binders and binders can lead to understanding the specificity of protein-protein interactions from structural viewpoints. In this review we focus on explaining current computational prediction methods to predict pairwise direct protein-protein interactions that form protein complexes.

Au133(SPh-tBu)52 nanomolecules: X-ray crystallography, optical, electrochemical, and theoretical analysis.

PubMed

Dass, Amala; Theivendran, Shevanuja; Nimmala, Praneeth Reddy; Kumara, Chanaka; Jupally, Vijay Reddy; Fortunelli, Alessandro; Sementa, Luca; Barcaro, Giovanni; Zuo, Xiaobing; Noll, Bruce C

2015-04-15

Crystal structure determination has revolutionized modern science in biology, chemistry, and physics. However, the difficulty in obtaining periodic crystal lattices which are needed for X-ray crystal analysis has hindered the determination of atomic structure in nanomaterials, known as the "nanostructure problem". Here, by using rigid and bulky ligands, we have overcome this limitation and successfully solved the X-ray crystallographic structure of the largest reported thiolated gold nanomolecule, Au133S52. The total composition, Au133(SPh-tBu)52, was verified using high resolution electrospray ionization mass spectrometry (ESI-MS). The experimental and simulated optical spectra show an emergent surface plasmon resonance that is more pronounced than in the slightly larger Au144(SCH2CH2Ph)60. Theoretical analysis indicates that the presence of rigid and bulky ligands is the key to the successful crystal formation.

Coarse-Grained Structural Modeling of Molecular Motors Using Multibody Dynamics

PubMed Central

Parker, David; Bryant, Zev; Delp, Scott L.

2010-01-01

Experimental and computational approaches are needed to uncover the mechanisms by which molecular motors convert chemical energy into mechanical work. In this article, we describe methods and software to generate structurally realistic models of molecular motor conformations compatible with experimental data from different sources. Coarse-grained models of molecular structures are constructed by combining groups of atoms into a system of rigid bodies connected by joints. Contacts between rigid bodies enforce excluded volume constraints, and spring potentials model system elasticity. This simplified representation allows the conformations of complex molecular motors to be simulated interactively, providing a tool for hypothesis building and quantitative comparisons between models and experiments. In an example calculation, we have used the software to construct atomically detailed models of the myosin V molecular motor bound to its actin track. The software is available at www.simtk.org. PMID:20428469

Reduction of stresses on buried rigid highway structures using the imperfect ditch method and expanded polystyrene (Geofoam).

DOT National Transportation Integrated Search

2005-04-01

The study of earth pressure distribution on buried structures has a great practical importance in constructing highway embankments above pipes and culverts. Based on Spanglers research, the supporting strength of a conduit depends primarily on thr...

Spin Qubits in Germanium Structures with Phononic Gap

NASA Technical Reports Server (NTRS)

Smelyanskiy, V. N.; Vasko, F. T.; Hafiychuk, V. V.; Dykman, M. I.; Petukhov, A. G.

2014-01-01

We propose qubits based on shallow donor electron spins in germanium structures with phononic gap. We consider a phononic crystal formed by periodic holes in Ge plate or a rigid cover / Ge layer / rigid substrate structure with gaps approximately a few GHz. The spin relaxation is suppressed dramatically, if the Zeeman frequency omegaZ is in the phononic gap, but an effective coupling between the spins of remote donors via exchange of virtual phonons remains essential. If omegaZ approaches to a gap edge in these structures, a long-range (limited by detuning of omegaZ) resonant exchange interaction takes place. We estimate that ratio of the exchange integral to the longitudinal relaxation rate exceeds 10(exp 5) and lateral scale of resonant exchange 0.1 mm. The exchange contribution can be verified under microwave pumping through oscillations of spin echo signal or through the differential absorption measurements. Efficient manipulation of spins due to the Rabi oscillations opens a new way for quantum information applications.

Homogenization models for thin rigid structured surfaces and films.

PubMed

Marigo, Jean-Jacques; Maurel, Agnès

2016-07-01

A homogenization method for thin microstructured surfaces and films is presented. In both cases, sound hard materials are considered, associated with Neumann boundary conditions and the wave equation in the time domain is examined. For a structured surface, a boundary condition is obtained on an equivalent flat wall, which links the acoustic velocity to its normal and tangential derivatives (of the Myers type). For a structured film, jump conditions are obtained for the acoustic pressure and the normal velocity across an equivalent interface (of the Ventcels type). This interface homogenization is based on a matched asymptotic expansion technique, and differs slightly from the classical homogenization, which is known to fail for small structuration thicknesses. In order to get insight into what causes this failure, a two-step homogenization is proposed, mixing classical homogenization and matched asymptotic expansion. Results of the two homogenizations are analyzed in light of the associated elementary problems, which correspond to problems of fluid mechanics, namely, potential flows around rigid obstacles.

Augmented multivariate image analysis applied to quantitative structure-activity relationship modeling of the phytotoxicities of benzoxazinone herbicides and related compounds on problematic weeds.

PubMed

Freitas, Mirlaine R; Matias, Stella V B G; Macedo, Renato L G; Freitas, Matheus P; Venturin, Nelson

2013-09-11

Two of major weeds affecting cereal crops worldwide are Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass). Thus, development of new herbicides against these weeds is required; in line with this, benzoxazinones, their degradation products, and analogues have been shown to be important allelochemicals and natural herbicides. Despite earlier structure-activity studies demonstrating that hydrophobicity (log P) of aminophenoxazines correlates to phytotoxicity, our findings for a series of benzoxazinone derivatives do not show any relationship between phytotoxicity and log P nor with other two usual molecular descriptors. On the other hand, a quantitative structure-activity relationship (QSAR) analysis based on molecular graphs representing structural shape, atomic sizes, and colors to encode other atomic properties performed very accurately for the prediction of phytotoxicities of these compounds against wild oat and rigid ryegrass. Therefore, these QSAR models can be used to estimate the phytotoxicity of new congeners of benzoxazinone herbicides toward A. fatua L. and L. rigidum Gaud.

Attitude output feedback control for rigid spacecraft with finite-time convergence.

PubMed

Hu, Qinglei; Niu, Guanglin

2017-09-01

The main problem addressed is the quaternion-based attitude stabilization control of rigid spacecraft without angular velocity measurements in the presence of external disturbances and reaction wheel friction as well. As a stepping stone, an angular velocity observer is proposed for the attitude control of a rigid body in the absence of angular velocity measurements. The observer design ensures finite-time convergence of angular velocity state estimation errors irrespective of the control torque or the initial attitude state of the spacecraft. Then, a novel finite-time control law is employed as the controller in which the estimate of the angular velocity is used directly. It is then shown that the observer and the controlled system form a cascaded structure, which allows the application of the finite-time stability theory of cascaded systems to prove the finite-time stability of the closed-loop system. A rigorous analysis of the proposed formulation is provided and numerical simulation studies are presented to help illustrate the effectiveness of the angular-velocity observer for rigid spacecraft attitude control. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Advanced Rigid Ablative TPS

NASA Technical Reports Server (NTRS)

Gasch, Matthew J.

2011-01-01

NASA Exploration Systems Mission Directorate s (ESMD) Entry, Descent, and Landing (EDL) Technology Development Project (TDP) and the NASA Aeronautics Research Mission Directorate s (ARMD) Hypersonics Project are developing new advanced rigid ablators in an effort to substantially increase reliability, decrease mass, and reduce life cycle cost of rigid aeroshell-based entry systems for multiple missions. Advanced Rigid Ablators combine ablation resistant top layers capable of high heat flux entry and enable high-speed EDL with insulating mass-efficient bottom that, insulate the structure and lower the areal weight. These materials may benefit Commercial Orbital Transportation Services (COTS) vendors and may potentially enable new NASA missions for higher velocity returns (e.g. asteroid, Mars). The materials have been thermally tested to 400-450 W/sq cm at the Laser Hardened Materials Evaluation Lab (LHMEL), Hypersonics Materials Evaluation Test System (HyMETS) and in arcjet facilities. Tested materials exhibit much lower backface temperatures and reduced recession over the baseline materials (PICA). Although the EDL project is ending in FY11, NASA in-house development of advanced ablators will continue with a focus on varying resin systems and fiber/resin interactions.

A recursive approach to the equations of motion for the maneuvering and control of flexible multi-body systems

NASA Technical Reports Server (NTRS)

Kwak, Moon K.; Meirovitch, Leonard

1991-01-01

Interest lies in a mathematical formulation capable of accommodating the problem of maneuvering a space structure consisting of a chain of articulated flexible substructures. Simultaneously, any perturbations from the 'rigid body' maneuvering and any elastic vibration must be suppressed. The equations of motion for flexible bodies undergoing rigid body motions and elastic vibrations can be obtained conveniently by means of Lagrange's equations in terms of quasi-coordinates. The advantage of this approach is that it yields equations in terms of body axes, which are the same axes that are used to express the control forces and torques. The equations of motion are nonlinear hybrid differential quations. The partial differential equations can be discretized (in space) by means of the finite element method or the classical Rayleigh-Ritz method. The result is a set of nonlinear ordinary differential equations of high order. The nonlinearity can be traced to the rigid body motions and the high order to the elastic vibration. Elastic motions tend to be small when compared with rigid body motions.

Elasticity improves handgrip performance and user experience during visuomotor control

PubMed Central

Rinne, Paul; Liardon, Jean-Luc; Uhomoibhi, Catherine; Bentley, Paul; Burdet, Etienne

2017-01-01

Passive rehabilitation devices, providing motivation and feedback, potentially offer an automated and low-cost therapy method, and can be used as simple human–machine interfaces. Here, we ask whether there is any advantage for a hand-training device to be elastic, as opposed to rigid, in terms of performance and preference. To address this question, we have developed a highly sensitive and portable digital handgrip, promoting independent and repetitive rehabilitation of grasp function based around a novel elastic force and position sensing structure. A usability study was performed on 66 healthy subjects to assess the effect of elastic versus rigid handgrip control during various visuomotor tracking tasks. The results indicate that, for tasks relying either on feedforward or on feedback control, novice users perform significantly better with the elastic handgrip, compared with the rigid equivalent (11% relative improvement, 9–14% mean range; p < 0.01). Furthermore, there was a threefold increase in the number of subjects who preferred elastic compared with rigid handgrip interaction. Our results suggest that device compliance is an important design consideration for grip training devices. PMID:28386448

Elasticity improves handgrip performance and user experience during visuomotor control.

PubMed

Mace, Michael; Rinne, Paul; Liardon, Jean-Luc; Uhomoibhi, Catherine; Bentley, Paul; Burdet, Etienne

2017-02-01

Passive rehabilitation devices, providing motivation and feedback, potentially offer an automated and low-cost therapy method, and can be used as simple human-machine interfaces. Here, we ask whether there is any advantage for a hand-training device to be elastic, as opposed to rigid, in terms of performance and preference. To address this question, we have developed a highly sensitive and portable digital handgrip, promoting independent and repetitive rehabilitation of grasp function based around a novel elastic force and position sensing structure. A usability study was performed on 66 healthy subjects to assess the effect of elastic versus rigid handgrip control during various visuomotor tracking tasks. The results indicate that, for tasks relying either on feedforward or on feedback control, novice users perform significantly better with the elastic handgrip, compared with the rigid equivalent (11% relative improvement, 9-14% mean range; p  < 0.01). Furthermore, there was a threefold increase in the number of subjects who preferred elastic compared with rigid handgrip interaction. Our results suggest that device compliance is an important design consideration for grip training devices.

A Program Structure for Event-Based Speech Synthesis by Rules within a Flexible Segmental Framework.

ERIC Educational Resources Information Center

Hill, David R.

1978-01-01

A program structure based on recently developed techniques for operating system simulation has the required flexibility for use as a speech synthesis algorithm research framework. This program makes synthesis possible with less rigid time and frequency-component structure than simpler schemes. It also meets real-time operation and memory-size…

Evaluation of the deflected mode of the monolithic span pieces and preassembled slabs combined action

NASA Astrophysics Data System (ADS)

Roshchina, Svetlana; Ezzi, Hisham; Shishov, Ivan; Lukin, Mikhail; Sergeev, Michael

2017-10-01

In single-story industrial buildings, the cost of roof covering comprises 40-55% of the total cost of the buildings. Therefore, research, development and application of new structural forms of reinforced concrete rafter structures, that allow to reduce material consumption and reduce the sub-assembly weight of structures, are the main tasks in the field of improving the existing generic solutions. The article suggests a method for estimating the relieving effect in the rafter structure as the result of combined deformation of the roof slabs with the end arrises. Calculated and experimental method for determining the stress and strain state of the rafter structure upper belt and the roof slabs with regard to their rigid connection has been proposed. A model of a highly effective roof structure providing a significant reduction in the construction height of the roofing and the cubic content of the building at the same time allowing to include the end arrises and a part of the slabs shelves with the help of the monolithic concrete has been proposed. The proposed prefabricated monolithic concrete rafter structure and its rigid connection with ribbed slabs allows to reduce the consumption of the prestressed slabs reinforcement by 50%.

Numerical modeling of the exterior-to-interior transmission of impulsive sound through three-dimensional, thin-walled elastic structures

NASA Astrophysics Data System (ADS)

Remillieux, Marcel C.; Pasareanu, Stephanie M.; Svensson, U. Peter

2013-12-01

Exterior propagation of impulsive sound and its transmission through three-dimensional, thin-walled elastic structures, into enclosed cavities, are investigated numerically in the framework of linear dynamics. A model was developed in the time domain by combining two numerical tools: (i) exterior sound propagation and induced structural loading are computed using the image-source method for the reflected field (specular reflections) combined with an extension of the Biot-Tolstoy-Medwin method for the diffracted field, (ii) the fully coupled vibro-acoustic response of the interior fluid-structure system is computed using a truncated modal-decomposition approach. In the model for exterior sound propagation, it is assumed that all surfaces are acoustically rigid. Since coupling between the structure and the exterior fluid is not enforced, the model is applicable to the case of a light exterior fluid and arbitrary interior fluid(s). The structural modes are computed with the finite-element method using shell elements. Acoustic modes are computed analytically assuming acoustically rigid boundaries and rectangular geometries of the enclosed cavities. This model is verified against finite-element solutions for the cases of rectangular structures containing one and two cavities, respectively.

Secondary flow vortical structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

NASA Astrophysics Data System (ADS)

Najjari, Mohammad Reza; Plesniak, Michael W.

2018-01-01

Secondary flow structures in a 180∘ curved pipe model of an artery are studied using particle image velocimetry. Both steady and pulsatile inflow conditions are investigated. In planar curved pipes with steady flow, multiple (two, four, six) vortices are detected. For pulsatile flow, various pairs of vortices, i.e., Dean, deformed-Dean, Lyne-type, and split-Dean, are present in the cross section of the pipe at 90∘ into the bend. The effects of nonplanar curvature (torsion) and vessel dilatation on these vortical structures are studied. Torsion distorts the symmetric secondary flows (which exist in planar curvatures) and can result in formation of more complex vortical structures. For example, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together in pulsatile flow. The vortical structures in elastic vessels with dilatation (0.61%-3.23%) are also investigated and the results are compared with rigid model results. It was found that the secondary flow structures in rigid and elastic models are similar, and hence the local compliance of the vessel does not affect the morphology of secondary flow structures.

Developing Educational Programs: Overcoming the Hidden Curriculum.

ERIC Educational Resources Information Center

Giroux, Henry A.

1978-01-01

What students learn in school is determined more by the hidden curriculum of rigid classroom structures and power relationships than formal curriculum. A less alienating classroom environment must replace these traditional structures, such as tracking, grading, and student powerlessness, if education is really to be reformed. (SJL)

76 FR 9820 - Notice of Intent To Grant a Partially Exclusive License

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-22

... NATIONAL AERONAUTICS AND SPACE ADMINISTRATION [Notice (11-018)] Notice of Intent To Grant a Partially Exclusive License AGENCY: National Aeronautics and Space Administration. ACTION: Notice of intent... Integrating A Rigid Structure Into A Flexible Wall Of An Inflatable Structure'' to Bigelow Aerospace, having...

Resilient modulus and the fatigue properties of Kansas hot mix asphalt mixes

DOT National Transportation Integrated Search

2006-08-01

A new design guide for pavement structures, based on a mechanistic design method, could be adopted by AASHTO in the near future and will replace the current version used by KDOT in the structural design of flexible and rigid pavements. The mechanisti...

Performance evaluation of Arizona's LTPP SPS-2 project : strategic study of structural factors for rigid pavements.

DOT National Transportation Integrated Search

2015-10-01

As part of the Long Term Pavement Performance (LTPP) Program, Arizona Department of Transportation : (ADOT) constructed 21 Specific Pavement Studies 2 (SPS-2) test sections on Interstate 10 near Buckeye, : Arizona, to study a variety of structural se...

Efficient swimming of an assembly of rigid spheres at low Reynolds number.

PubMed

Felderhof, B U

2015-08-01

The swimming of an assembly of rigid spheres immersed in a viscous fluid of infinite extent is studied in low-Reynolds-number hydrodynamics. The instantaneous swimming velocity and rate of dissipation are expressed in terms of the time-dependent displacements of sphere centers about their collective motion. For small-amplitude swimming with periodically oscillating displacements, optimization of the mean swimming speed at given mean power leads to an eigenvalue problem involving a velocity matrix and a power matrix. The corresponding optimal stroke permits generalization to large-amplitude motion in a model of spheres with harmonic interactions and corresponding actuating forces. The method allows straightforward calculation of the swimming performance of structures modeled as assemblies of interacting rigid spheres. A model of three collinear spheres with motion along the common axis is studied as an example.

The rigidity and mobility of screw dislocations in a thin film

NASA Astrophysics Data System (ADS)

Wang, Fei

2018-07-01

An equation of screw dislocations in a thin film is derived for arbitrary boundary conditions. The boundary conditions can be the free surface, the fixed surface or the gradient loading imposed on the surface. The new equation makes it possible to study changes in the dislocation structure under various gradient stress applied to the surface. The rigidity and mobility of screw dislocations in a thin film are explored by using the equation. It is found that the screw dislocation core in a thin film is like a Hookean body with a specific shear stress applied to the surface. Free-surface effects on the Peierls stress are investigated and compared with previous studies. An abnormal behavior of the Peierls stress of screw dislocations in a soft-inclusion film between two rigid films is predicted theoretically.

Effect of the cellular structure on thermal conductivity of rigid closed-cell foam polymers during long-term aging

NASA Astrophysics Data System (ADS)

Dementyev, A. G.; Dementyev, M. A.; Zinger, P. A.; Metlyakova, I. R.

1999-03-01

The thermal conductivity of rigid closed-cell polyurethane foams during long-term aging has been studied. The similarity between the kinetics of changes in the physical and mechanical characteristics of PU foams on progressive aging is established, which is attributed to the effect of matrix destruction. It is found that rigid foams have cell walls of various strength, whose impact on the kinetics of changes in the physical characteristics of the foams during long-term aging is ascertained. The results of predicting the thermal conductivity of PU foams by the method of temperature-time analogy and establishing the limits of its application are discussed. The research presented is of interest both in determining the foam durability and in replacing freons by alternative, ecologically less harmful blowing agents.

Means for supporting fuel elements in a nuclear reactor

DOEpatents

Andrews, Harry N.; Keller, Herbert W.

1980-01-01

A grid structure for a nuclear reactor fuel assembly comprising a plurality of connecting members forming at least one longitudinally extending opening peripheral and inner fuel element openings through each of which openings at least one nuclear fuel element extends, said connecting members forming wall means surrounding said each peripheral and inner fuel element opening, a pair of rigid projections longitudinally spaced from one another extending from a portion of said wall means into said each peripheral and inner opening for rigidly engaging said each fuel element, respectively, yet permit individual longitudinal slippage thereof, and resilient means formed integrally on and from said wall means and positioned in said each peripheral and inner opening in opposed relationship with said projections and located to engage said fuel element to bias the latter into engagement with said rigid projections, respectively

Rigidity in Gender-Typed Behaviors in Early Childhood: A Longitudinal Study of Ethnic Minority Children

PubMed Central

Ruble, Diane; Tamis-LeMonda, Catherine; Shrout, Patrick E.

2014-01-01

A key prediction of cognitive theories of gender development concerns developmental trajectories in the relative strength or rigidity of gender typing. To examine these trajectories in early childhood, 229 children (African American, Mexican, Dominican) were followed annually from age 3 to 5 and gender-stereotypical appearance, dress-up play, toy play, and sex segregation were examined. High gender-typing was found across ethnic group, and most behaviors increased in rigidity, especially from age 3 to 4. In addressing controversy surrounding the stability and structure of gender-typing it was found that from year to year, most behaviors showed moderately stable individual differences. Behaviors were uncorrelated within age, but showed more concordance in change across time, suggesting that aspects of gender-typing are multidimensional but still show coherence. PMID:23432471

First order coupled dynamic model of flexible space structures with time-varying configurations

NASA Astrophysics Data System (ADS)

Wang, Jie; Li, Dongxu; Jiang, Jianping

2017-03-01

This paper proposes a first order coupled dynamic modeling method for flexible space structures with time-varying configurations for the purpose of deriving the characteristics of the system. The model considers the first time derivative of the coordinate transformation matrix between the platform's body frame and the appendage's floating frame. As a result it can accurately predict characteristics of the system even if flexible appendages rotate with complex trajectory relative to the rigid part. In general, flexible appendages are fixed on the rigid platform or forced to rotate with a slow angular velocity. So only the zero order of the transformation matrix is considered in conventional models. However, due to neglecting of time-varying terms of the transformation matrix, these models introduce severe error when appendages, like antennas, for example, rotate with a fast speed relative to the platform. The first order coupled dynamic model for flexible space structures proposed in this paper resolve this problem by introducing the first time derivative of the transformation matrix. As a numerical example, a central core with a rotating solar panel is considered and the results are compared with those given by the conventional model. It has been shown that the first order terms are of great importance on the attitude of the rigid body and dynamic response of the flexible appendage.

Rapid bonding of polydimethylsiloxane (PDMS) to various stereolithographically (STL) structurable epoxy resins using photochemically cross-linked intermediary siloxane layers

NASA Astrophysics Data System (ADS)

Wilhelm, Elisabeth; Neumann, Christiane; Sachsenheimer, Kai; Länge, Kerstin; Rapp, Bastian E.

2014-03-01

In this paper we present a fast, low cost bonding technology for combining rigid epoxy components with soft membranes made out of polydimethylsiloxane (PDMS). Both materials are commonly used for microfluidic prototyping. Epoxy resins are often applied when rigid channels are required, that will not deform if exposed to high pressure. PDMS, on the other hand, is a flexible material, which allows integration of membrane valves on the chip. However, the integration of pressure driven components, such as membrane valves and pumps, into a completely flexible device leads to pressure losses. In order to build up pressure driven components with maximum energy efficiency a combination of rigid guiding channels and flexible membranes would be advisable. Stereolithographic (STL) structuring would be an ideal fabrication technique for this purpose, because complex 3D-channels structures can easily be fabricated using this technology. Unfortunately, the STL epoxies cannot be bonded using common bonding techniques. For this reason we propose two UV-light based silanization techniques that enable plasma induced bonding of epoxy components. The entire process including silanization and corona discharge bonding can be carried out within half an hour. Average bond strengths up to 350 kPa (depending on the silane) were determined in ISO-conform tensile testing. The applicability of both techniques for microfluidic applications was proven by hydrolytic stability testing lasting more than 40 hours.

Degradation studies on highly oriented poly(glycolic acid) fibres with different lamellar structures.

PubMed

de Oca, Horacio Montes; Farrar, David F; Ward, Ian M

2011-04-01

Highly oriented poly(glycolic acid) (PGA) fibres with an initial tensile strength of 1.1 GPa and different lamellar morphologies were prepared and studied during degradation in aqueous media at 37°C. A combination of small- and wide-angle X-ray scattering was used to study the structural changes during degradation and to generate two structural models of highly oriented PGA fibres with different lamellar morphologies. It is shown that as a result of crystallisation during degradation PGA crystals grow preferentially along the (110) and (020) directions of the crystal lattice or perpendicular to the orientation direction of the fibres. (1)H nuclear magnetic resonance measurements revealed three phases within the fibres with different relaxation times: (1) a mobile amorphous phase with a short relaxation time; (2) a semi-rigid phase with an intermediate relaxation time; (3) a rigid crystalline phase with a longer relaxation time. It is shown that the mobile amorphous phase degrades very rapidly and that it plays only a small role in the tensile mechanical behaviour of the fibres during degradation. It is shown that semi-rigid chains connecting crystalline domains are responsible for transferring the stress between crystalline domains and carrying the tensile deformation. It is proposed that once these tie molecules degrade considerably the oriented fibres very rapidly lose their strength retention. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Hexagonal-structured epsilon-NbN. Ultra-incompressibility, high shear rigidity, and a possible hard superconducting material

DOE PAGES

Zou, Y.; Wang, X.; Chen, T.; ...

2015-06-01

Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂B S/∂P = 3.81(3) andmore » ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G 0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.« less

Hexagonal-structured epsilon-NbN. Ultra-incompressibility, high shear rigidity, and a possible hard superconducting material

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

Zou, Y.; Wang, X.; Chen, T.

Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂B S/∂P = 3.81(3) andmore » ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G 0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions.« less

Application of energy derivative method to determine the structural components' contribution to deceleration in crashes.

PubMed

Nagasaka, Kei; Mizuno, Koji; Thomson, Robert

2018-03-26

For occupant protection, it is important to understand how a car's deceleration time history in crashes can be designed using efficient of energy absorption by a car body's structure. In a previous paper, the authors proposed an energy derivative method to determine each structural component's contribution to the longitudinal deceleration of a car passenger compartment in crashes. In this study, this method was extended to 2 dimensions in order to analyze various crash test conditions. The contribution of each structure estimated from the energy derivative method was compared to that from a conventional finite element (FE) analysis method using cross-sectional forces. A 2-dimensional energy derivative method was established. A simple FE model with a structural column connected to a rigid body was used to confirm the validity of this method and to compare with the result of cross-sectional forces determined using conventional analysis. Applying this method to a full-width frontal impact simulation of a car FE model, the contribution and the cross-sectional forces of the front rails were compared. In addition, this method was applied to a pedestrian headform FE simulation in order to determine the influence of the structural and inertia forces of the hood structures on the deceleration of the headform undergoing planar motion. In an oblique impact of the simple column and rigid body model, the sum of the contributions of each part agrees with the rigid body deceleration, which indicates the validity of the 2-dimensional energy derivative method. Using the energy derivative method, it was observed that each part of the column contributes to the deceleration of the rigid body by collapsing in the sequence from front to rear, whereas the cross-sectional force at the rear of the column cannot detect the continuous collapse. In the full-width impact of a car, the contributions of the front rails estimated in the energy derivative method was smaller than that using the cross-sectional forces at the rear end of the front rails due to the deformation of the passenger compartment. For a pedestrian headform impact, the inertial and structural forces of the hood contributed to peaks of the headform deceleration in the initial and latter phases, respectively. Using the 2-dimensional energy derivative method, it is possible to analyze an oblique impact or a pedestrian headform impact with large rotations. This method has advantages compared to the conventional approach using cross-sectional forces because the contribution of each component to system deceleration can be determined.

Omnidirectional structured light in a flexible configuration.

PubMed

Paniagua, Carmen; Puig, Luis; Guerrero, José J

2013-10-14

Structured light is a perception method that allows us to obtain 3D information from images of the scene by projecting synthetic features with a light emitter. Traditionally, this method considers a rigid configuration, where the position and orientation of the light emitter with respect to the camera are known and calibrated beforehand. In this paper we propose a new omnidirectional structured light system in flexible configuration, which overcomes the rigidness of the traditional structured light systems. We propose the use of an omnidirectional camera combined with a conic pattern light emitter. Since the light emitter is visible in the omnidirectional image, the computation of its location is possible. With this information and the projected conic in the omnidirectional image, we are able to compute the conic reconstruction, i.e., the 3D information of the conic in the space. This reconstruction considers the recovery of the depth and orientation of the scene surface where the conic pattern is projected. One application of our proposed structured light system in flexible configuration consists of a wearable omnicamera with a low-cost laser in hand for visual impaired personal assistance.

The Present Status of Airship Construction, Especially of Airship-framing Construction

NASA Technical Reports Server (NTRS)

Ebner, Hans

1938-01-01

This work proposes to sketch, in broad outline, the status of airship construction in the various countries, at a time when commerce over great distances might be finally opened up to the airship through the performances of the "Graf Zeppelin." After a short historical review, a survey of the most important rigid and semirigid airships built since 1925, their differences and special problems, is made. In more detailed treatment, the framing construction of the more recent rigid airships and some especially interesting structural questions are investigated.

Engineering mechanics: statics and dynamics. [Textbook

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

Sandor, B.I.

1983-01-01

The purpose of this textbook is to provide engineering students with basic learning material about statics and dynamics which are fundamental engineering subjects. The chapters contain information on: an introduction to engineering mechanics; forces on particles, rigid bodies, and structures; kinetics of particles, particle systems, and rigid bodies in motion; kinematics; mechanical vibrations; and friction, work, moments of inertia, and potential energy. Each chapter contains introductory material, the development of the essential equations, worked-out example problems, homework problems, and, finally, summaries of the essential methods and equations, graphically illustrated where appropriate. (LCL)

Nonlinear complex dynamics and Keynesian rigidity: A short introduction

NASA Astrophysics Data System (ADS)

Jovero, Edgardo

2005-09-01

The topic of this paper is to show that the greater acceptance and intense use of complex nonlinear dynamics in macroeconomics makes sense only within the neoKeynesian tradition. An example is presented regarding the behavior of an open-economy two-sector growth model endowed with Keynesian rigidity. The Keynesian view that structural instability globally exists in the aggregate economy is put forward, and therefore the need arises for policy to alleviate this instability in the form of dampened fluctuations is presented as an alternative view for macroeconomic theorizing.

Bending spring rate investigation of nanopipette for cell injection.

PubMed

Shen, Yajing; Zhang, Zhenhai; Fukuda, Toshio

2015-04-17

Bending of nanopipette tips during cell penetration is a major cause of cell injection failure. However, the flexural rigidity of nanopipettes is little known due to their irregular structure. In this paper, we report a quantitative method to estimate the flexural rigidity of a nanopipette by investigating its bending spring rate. First nanopipettes with a tip size of 300 nm are fabricated from various glass tubes by laser pulling followed by focused ion beam (FIB) milling. Then the bending spring rate of the nanopipettes is investigated inside a scanning electron microscope (SEM). Finally, a yeast cell penetration test is performed on these nanopipettes, which have different bending spring rates. The results show that nanopipettes with a higher bending spring rate have better cell penetration capability, which confirms that the bending spring rate may well reflect the flexural rigidity of a nanopipette. This method provides a quantitative parameter for characterizing the mechanical property of a nanopipette that can be potentially taken as a standard specification in the future. This general method can also be used to estimate other one-dimensional structures for cell injection, which will greatly benefit basic cell biology research and clinical applications.

Bending spring rate investigation of nanopipette for cell injection

NASA Astrophysics Data System (ADS)

Shen, Yajing; Zhang, Zhenhai; Fukuda, Toshio

2015-04-01

Bending of nanopipette tips during cell penetration is a major cause of cell injection failure. However, the flexural rigidity of nanopipettes is little known due to their irregular structure. In this paper, we report a quantitative method to estimate the flexural rigidity of a nanopipette by investigating its bending spring rate. First nanopipettes with a tip size of 300 nm are fabricated from various glass tubes by laser pulling followed by focused ion beam (FIB) milling. Then the bending spring rate of the nanopipettes is investigated inside a scanning electron microscope (SEM). Finally, a yeast cell penetration test is performed on these nanopipettes, which have different bending spring rates. The results show that nanopipettes with a higher bending spring rate have better cell penetration capability, which confirms that the bending spring rate may well reflect the flexural rigidity of a nanopipette. This method provides a quantitative parameter for characterizing the mechanical property of a nanopipette that can be potentially taken as a standard specification in the future. This general method can also be used to estimate other one-dimensional structures for cell injection, which will greatly benefit basic cell biology research and clinical applications.

A numerical method for simulations of rigid fiber suspensions

NASA Astrophysics Data System (ADS)

Tornberg, Anna-Karin; Gustavsson, Katarina

2006-06-01

In this paper, we present a numerical method designed to simulate the challenging problem of the dynamics of slender fibers immersed in an incompressible fluid. Specifically, we consider microscopic, rigid fibers, that sediment due to gravity. Such fibers make up the micro-structure of many suspensions for which the macroscopic dynamics are not well understood. Our numerical algorithm is based on a non-local slender body approximation that yields a system of coupled integral equations, relating the forces exerted on the fibers to their velocities, which takes into account the hydrodynamic interactions of the fluid and the fibers. The system is closed by imposing the constraints of rigid body motions. The fact that the fibers are straight have been further exploited in the design of the numerical method, expanding the force on Legendre polynomials to take advantage of the specific mathematical structure of a finite-part integral operator, as well as introducing analytical quadrature in a manner possible only for straight fibers. We have carefully treated issues of accuracy, and present convergence results for all numerical parameters before we finally discuss the results from simulations including a larger number of fibers.

Glycerol in micellar confinement with tunable rigidity

NASA Astrophysics Data System (ADS)

Lannert, Michael; Müller, Allyn; Gouirand, Emmanuel; Talluto, Vincenzo; Rosenstihl, Markus; Walther, Thomas; Stühn, Bernd; Blochowicz, Thomas; Vogel, Michael

2016-12-01

We investigate the glassy dynamics of glycerol in the confinement of a microemulsion system, which is stable on cooling down to the glass transition of its components. By changing the composition, we vary the viscosity of the matrix, while keeping the confining geometry intact, as is demonstrated by small angle X-ray scattering. By means of 2H NMR, differential scanning calorimetry, and triplet solvation dynamics we, thus, probe the dynamics of glycerol in confinements of varying rigidity. 2H NMR results show that, at higher temperatures, the dynamics of confined glycerol is unchanged compared to bulk behavior, while the reorientation of glycerol molecules becomes significantly faster than in the bulk in the deeply supercooled regime. However, comparison of different 2H NMR findings with data from calorimetry and solvation dynamics reveals that this acceleration is not due to the changed structural relaxation of glycerol, but rather due to the rotational motion of essentially rigid glycerol droplets or of aggregates of such droplets in a more fluid matrix. Thus, independent of the matrix mobility, the glycerol dynamics remains unchanged except for the smallest droplets, where an increase of Tg and, thus, a slowdown of the structural relaxation is observed even in a fluid matrix.

Morphology and properties of poly vinyl alcohol (PVA) scaffolds: impact of process variables.

PubMed

Ye, Mao; Mohanty, Pravansu; Ghosh, Gargi

2014-09-01

Successful engineering of functional biological substitutes requires scaffolds with three-dimensional interconnected porous structure, controllable rate of biodegradation, and ideal mechanical strength. In this study, we report the development and characterization of micro-porous PVA scaffolds fabricated by freeze drying method. The impact of molecular weight of PVA, surfactant concentration, foaming time, and stirring speed on pore characteristics, mechanical properties, swelling ratio, and rate of degradation of the scaffolds was characterized. Results show that a foaming time of 60s, a stirring speed of 1,000 rpm, and a surfactant concentration of 5% yielded scaffolds with rigid structure but with interconnected pores. Study also demonstrated that increased foaming time increased porosity and swelling ratio and reduced the rigidity of the samples. Copyright © 2014 Elsevier B.V. All rights reserved.

APPLIED ORIGAMI. Origami of thick panels.

PubMed

Chen, Yan; Peng, Rui; You, Zhong

2015-07-24

Origami patterns, including the rigid origami patterns in which flat inflexible sheets are joined by creases, are primarily created for zero-thickness sheets. In order to apply them to fold structures such as roofs, solar panels, and space mirrors, for which thickness cannot be disregarded, various methods have been suggested. However, they generally involve adding materials to or offsetting panels away from the idealized sheet without altering the kinematic model used to simulate folding. We develop a comprehensive kinematic synthesis for rigid origami of thick panels that differs from the existing kinematic model but is capable of reproducing motions identical to that of zero-thickness origami. The approach, proven to be effective for typical origami, can be readily applied to fold real engineering structures. Copyright © 2015, American Association for the Advancement of Science.

Stability of binaries. Part 1: Rigid binaries

NASA Astrophysics Data System (ADS)

Sharma, Ishan

2015-09-01

We consider the stability of binary asteroids whose members are possibly granular aggregates held together by self-gravity alone. A binary is said to be stable whenever each member is orbitally and structurally stable to both orbital and structural perturbations. To this end, we extend the stability test for rotating granular aggregates introduced by Sharma (Sharma, I. [2012]. J. Fluid Mech., 708, 71-99; Sharma, I. [2013]. Icarus, 223, 367-382; Sharma, I. [2014]. Icarus, 229, 278-294) to the case of binary systems comprised of rubble members. In part I, we specialize to the case of a binary with rigid members subjected to full three-dimensional perturbations. Finally, we employ the stability test to critically appraise shape models of four suspected binary systems, viz., 216 Kleopatra, 25143 Itokawa, 624 Hektor and 90 Antiope.

First principles molecular dynamics of molten NaCl

NASA Astrophysics Data System (ADS)

Galamba, N.; Costa Cabral, B. J.

2007-03-01

First principles Hellmann-Feynman molecular dynamics (HFMD) results for molten NaCl at a single state point are reported. The effect of induction forces on the structure and dynamics of the system is studied by comparison of the partial radial distribution functions and the velocity and force autocorrelation functions with those calculated from classical MD based on rigid-ion and shell-model potentials. The first principles results reproduce the main structural features of the molten salt observed experimentally, whereas they are incorrectly described by both rigid-ion and shell-model potentials. Moreover, HFMD Green-Kubo self-diffusion coefficients are in closer agreement with experimental data than those predicted by classical MD. A comprehensive discussion of MD results for molten NaCl based on different ab initio parametrized polarizable interionic potentials is also given.

Experimentally biased model structure of the Hsc70/auxilin complex: Substrate transfer and interdomain structural change

PubMed Central

Gruschus, James M.; Greene, Lois E.; Eisenberg, Evan; Ferretti, James A.

2004-01-01

A model structure of the Hsc70/auxilin complex has been constructed to gain insight into interprotein substrate transfer and ATP hydrolysis induced conformational changes in the multidomain Hsc70 structure. The Hsc70/auxilin system, which is a member of the Hsp70/Hsp40 chaperone system family, uncoats clathrin-coated vesicles in an ATP hydrolysis-driven process. Incorporating previous results from NMR and mutant binding studies, the auxilin J-domain was docked into the Hsc70 ATPase domain lower cleft using rigid backbone/flexible side chain molecular dynamics, and the Hsc70 substrate binding domain was docked by a similar procedure. For comparison, J-domain and substrate binding domain docking sites were obtained by the rigid-body docking programs DOT and ZDOCK, filtered and ranked by the program ClusPro, and relaxed using the same rigid backbone/flexible side chain dynamics. The substrate binding domain sites were assessed in terms of conserved surface complementarity and feasibility in the context of substrate transfer, both for auxilin and another Hsp40 protein, Hsc20. This assessment favors placement of the substrate binding domain near D152 on the ATPase domain surface adjacent to the J-domain invariant HPD segment, with the Hsc70 interdomain linker in the lower cleft. Examining Hsc70 interdomain energetics, we propose that long-range electrostatic interactions, perhaps due to a difference in the pKa values of bound ATP and ADP, could play a major role in the structural change induced by ATP hydrolysis. Interdomain electrostatic interactions also appear to play a role in stimulation of ATPase activity due to J-domain binding and substrate binding by Hsc70. PMID:15273304

The structure of shock wave in a gas consisting of ideally elastic, rigid spherical molecules

NASA Technical Reports Server (NTRS)

Cheremisin, F. G.

1972-01-01

Principal approaches are examined to the theoretical study of the shock layer structure. The choice of a molecular model is discussed and three procedures are formulated. These include a numerical calculation method, solution of the kinetic relaxation equation, and solution of the Boltzmann equation.

49 CFR 238.123 - Emergency roof access.

Code of Federal Regulations, 2011 CFR

2011-10-01

... minimum opening of 26 inches longitudinally (i.e., parallel to the longitudinal axis of the car) by 24... be free of any rigid secondary structure (e.g., a diffuser or diffuser support, lighting back fixture... means of a structural weak point, it shall be permissible to cut through interior panels, liners, or...

Lightweight solar concentrator structures, phase 2

NASA Technical Reports Server (NTRS)

Williams, Brian E.; Kaplan, Richard B.

1993-01-01

This report summarizes the results of the program conducted by Ultramet under SBIR Phase 2 Contract NAS3-25418. The objective of this program was to develop lightweight materials and processes for advanced high accuracy Space Solar Concentrators using rigidized foam for the substrate structure with an integral optical surface.

Hacia la Nueva Reforma (Toward the New Reform).

ERIC Educational Resources Information Center

Ribeiro, Darcy

A new wave of reform is needed for Latin American universities suffering from structural rigidity, duplicity, inefficiency, and lack of community. The structural crisis in the university reflects the general social crisis in which society is pressured by opposing forces leading it toward either historical modernization or evolutionary…

Rigid aromatic linking moiety in cationic lipids for enhanced gene transfection efficiency.

PubMed

Wang, Bing; Zhao, Rui-Mo; Zhang, Ji; Liu, Yan-Hong; Huang, Zheng; Yu, Qing-Ying; Yu, Xiao-Qi

2017-08-18

Although numerous cationic lipids have been developed as non-viral gene vectors, the structure-activity relationship (SAR) of these materials remains unclear and needs further investigation. In this work, a series of lysine-derived cationic lipids containing linkages with different rigidity were designed and synthesized. SAR studies showed that lipids with rigid aromatic linkage could promote the formation of tight liposomes and enhance DNA condensation, which is essential for the gene delivery process. These lipids could give much higher transfection efficiency than those containing more flexible aliphatic linkage in various cell lines. Moreover, the rigid aromatic linkage also affords the material higher serum tolerance ability. Flow cytometry assay revealed that the target lipids have good cellular uptake, while confocal microscopy observation showed weaker endosome escape than Lipofectamine 2000. To solve such problem and further increase the transfection efficiency, some lysosomotropic reagents were used to improve the endosome escape of lipoplex. As expected, higher transfection efficiency than Lipofectamine 2000 could be obtained via this strategy. Cytotoxicity assay showed that these lipids have lower toxicity in various cell lines than Lipofectamine 2000, suggesting their potential for further application. This work demonstrates that a rigid aromatic linkage might distinctly improve the gene transfection abilities of cationic lipids and affords information to construct safe and efficient gene vector towards practical application. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Template-Based 3D Reconstruction of Non-rigid Deformable Object from Monocular Video

NASA Astrophysics Data System (ADS)

Liu, Yang; Peng, Xiaodong; Zhou, Wugen; Liu, Bo; Gerndt, Andreas

2018-06-01

In this paper, we propose a template-based 3D surface reconstruction system of non-rigid deformable objects from monocular video sequence. Firstly, we generate a semi-dense template of the target object with structure from motion method using a subsequence video. This video can be captured by rigid moving camera orienting the static target object or by a static camera observing the rigid moving target object. Then, with the reference template mesh as input and based on the framework of classical template-based methods, we solve an energy minimization problem to get the correspondence between the template and every frame to get the time-varying mesh to present the deformation of objects. The energy terms combine photometric cost, temporal and spatial smoothness cost as well as as-rigid-as-possible cost which can enable elastic deformation. In this paper, an easy and controllable solution to generate the semi-dense template for complex objects is presented. Besides, we use an effective iterative Schur based linear solver for the energy minimization problem. The experimental evaluation presents qualitative deformation objects reconstruction results with real sequences. Compare against the results with other templates as input, the reconstructions based on our template have more accurate and detailed results for certain regions. The experimental results show that the linear solver we used performs better efficiency compared to traditional conjugate gradient based solver.

Photo-crystallization in a-Se layer structures: Effects of film-substrate interface-rigidity

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

Lindberg, G. P.; Gross, N.; Weinstein, B. A.

Amorphous selenium (a-Se) films deposited on rigid substrates can undergo photo-induced crystallization (PC) even at temperatures (T) well below the glass transition, T{sub g} ∼ 313 K. Substrate-generated shear strain is known to promote the PC process. In the present work, we explore the influence of different substrates (Si and glass), and different film-layer-substrate combinations, on the PC in a variety of a-Se films and film-structures. The intermediate layers (indium tin oxide and polyimide) are chosen to promote conductivity and/or to be a buffer against interface strain in structures of interest for digital imaging applications. The PC characteristics in these samples are evaluatedmore » and compared using optical microscopy, atomic-force microscopy, Raman mapping, and T-dependent Raman spectroscopy. Both the presence of a soft intermediate layer, and the thermal softening that occurs for T increasing through T{sub g}, inhibit the tendency for the onset of PC. The extensive PC mapping results in the wide range of samples studied here, as well as the suppression of PC near T{sub g} in this array of samples, strongly support the generality of this behavior. As a consequence, one may expect that the stability of a-Se films against PC can be enhanced by decreasing the rigidity of the film-substrate interface. In this regard, advanced film structures that employ flexible substrates, soft intermediate layers, and/or are designed to be operated near T{sub g} should be explored.« less

Trajectory Control for Very Flexible Aircraft

DTIC Science & Technology

2006-10-30

aircraft are coupled with the aeroelastic equations that govern the geometrically nonlinear structural response of the vehicle. A low -order strain...nonlinear structural formulation, the finite state aerodynamic model, and the nonlinear rigid body equations together provide a low -order complete...nonlinear aircraft analysis tool. Due to the inherent flexibility of the aircraft modeling, the low order structural fre- quencies are of the same order

High-temperature zirconia insulation and method for making same

DOEpatents

Wrenn, G.E. Jr.; Holcombe, C.E. Jr.; Lewis, J. Jr.

The present invention is directed to a highly pure, partially stabilized, fibrous zirconia composite for use as thermal insulation in environments where temperatures up to about 2,000/sup 0/C are utilized. The composite of the present invention is fabricated into any suitable configuration such as a cone, cylinder dome or the like by vacuum molding an aqueous slurry of partially stabilized zirconia fibers into a desired configuration on a suitably shaped mandrel. The molded fibers are infiltrated with zirconyl nitrate and the resulting structure is then dried to form a rigid structure which may be removed and placed in a furnace. The structure is then heated in air to a temperature of about 600/sup 0/C for driving off the nitrate from the structure and for oxidizing the zirconyl ion to zirconia. Thereafter, the structure is heated to about 950/sup 0/ to 1,250/sup 0/C to fuse the zirconia fibers at their nexi in a matrix of zirconia. The composite produced by the present invention is self-supporting and can be readily machined to desired final dimensions. Additional heating to about 1800/sup 0/ to 2000/sup 0/C further improves structural rigidity.

High-temperature zirconia insulation and method for making same

DOEpatents

Wrenn, Jr., George E.; Holcombe, Jr., Cressie E.; Lewis, Jr., John

1988-01-01

The present invention is directed to a highly pure, partially stabilized, fibrous zirconia composite for use as thermal insulation in environments where temperatures up to about 2000.degree. C. are utilized. The composite of the present invention is fabricated into any suitable configuration such as a cone, cylinder, dome or the like by vacuum molding an aqueous slurry of partially stabilized zirconia fibers into a desired configuration on a suitably shaped mandrel. The molded fibers are infiltrated with zirconyl nitrate and the resulting structure is then dried to form a rigid structure which may be removed and placed in a furnace. The structure is then heated in air to a temperature of about 600.degree. C. for driving off the nitrate from the structure and for oxidizing the zirconyl ion to zirconia. Thereafter, the structure is heated to about 950.degree. to 1,250.degree. C. to fuse the zirconia fibers at their nexi in a matrix of zirconia. The composite produced by the present invention is self-supporting and can be readily machined to desired final dimensions. Additional heating to about 1800.degree. to 2000.degree. C. further improves structural rigidity.

Venus In Situ Explorer Mission design using a mechanically deployed aerodynamic decelerator

NASA Astrophysics Data System (ADS)

Smith, B.; Venkatapathy, E.; Wercinski, P.; Yount, B.; Prabhu, D.; Gage, P.; Glaze, L.; Baker, C.

The Venus In Situ Explorer (VISE) Mission addresses the highest priority science questions within the Venus community outlined in the National Research Council's Decadal Survey. The heritage Venus atmospheric entry system architecture, a 45° sphere-cone rigid aeroshell with a carbon phenolic thermal protection system, may no longer be the preferred entry system architecture compared to other viable alternatives being explored at NASA. A mechanically-deployed aerodynamic decelerator, known as the Adaptive Deployable Entry and Placement Technology (ADEPT), is an entry system alternative that can provide key operational benefits and risk reduction compared to a rigid aeroshell. This paper describes a mission feasibility study performed with the objectives of identifying potential adverse interactions with other mission elements and establishing requirements on decelerator performance. Feasibility is assessed through a launch-to-landing mission design study where the Venus Intrepid Tessera Lander (VITaL), a VISE science payload designed to inform the Decadal Survey results, is repackaged from a rigid aeroshell into the ADEPT decelerator. It is shown that ADEPT reduces the deceleration load on VITaL by an order of magnitude relative to a rigid aeroshell. The more benign entry environment opens up the VISE mission design environment for increased science return, reduced risk, and reduced cost. The ADEPT-VITAL mission concept of operations is presented and details of the entry vehicle structures and mechanisms are given. Finally, entry aerothermal analysis is presented that defines the operational requirements for a revolutionary structural-TPS material employed by ADEPT: three-dimensionally woven carbon cloth. Ongoing work to mitigate key risks identified in this feasibility study is presented.

Molecular dynamics simulation of framework flexibility effects on noble gas diffusion in HKUST-1 and ZIF-8

DOE PAGES

Parkes, Marie V.; Demir, Hakan; Teich-McGoldrick, Stephanie L.; ...

2014-03-28

Molecular dynamics simulations were used to investigate trends in noble gas (Ar, Kr, Xe) diffusion in the metal-organic frameworks HKUST-1 and ZIF-8. Diffusion occurs primarily through inter-cage jump events, with much greater diffusion of guest atoms in HKUST-1 compared to ZIF-8 due to the larger cage and window sizes in the former. We compare diffusion coefficients calculated for both rigid and flexible frameworks. For rigid framework simulations, in which the framework atoms were held at their crystallographic or geometry optimized coordinates, sometimes dramatic differences in guest diffusion were seen depending on the initial framework structure or the choice of frameworkmore » force field parameters. When framework flexibility effects were included, argon and krypton diffusion increased significantly compared to rigid-framework simulations using general force field parameters. Additionally, for argon and krypton in ZIF-8, guest diffusion increased with loading, demonstrating that guest-guest interactions between cages enhance inter-cage diffusion. No inter-cage jump events were seen for xenon atoms in ZIF-8 regardless of force field or initial structure, and the loading dependence of xenon diffusion in HKUST-1 is different for rigid and flexible frameworks. Diffusion of krypton and xenon in HKUST-1 depends on two competing effects: the steric effect that decreases diffusion as loading increases, and the “small cage effect” that increases diffusion as loading increases. Finally, a detailed analysis of the window size in ZIF-8 reveals that the window increases beyond its normal size to permit passage of a (nominally) larger krypton atom.« less

Permanent magnet design methodology

NASA Technical Reports Server (NTRS)

Leupold, Herbert A.

1991-01-01

Design techniques developed for the exploitation of high energy magnetically rigid materials such as Sm-Co and Nd-Fe-B have resulted in a revolution in kind rather than in degree in the design of a variety of electron guidance structures for ballistic and aerospace applications. Salient examples are listed. Several prototype models were developed. These structures are discussed in some detail: permanent magnet solenoids, transverse field sources, periodic structures, and very high field structures.

On the Propagation of Small Perturbations in Two Simple Aeroelastic Systems

NASA Technical Reports Server (NTRS)

Iollo, Angelo; Salas, Manuel D.

1998-01-01

In this paper we investigate the wave propagation patterns for two simple flow-structure problems. We focus on the study of the propagation speeds of the waves in the fluid and in the structure, as the rigidity of the structure and the Mach number of the undisturbed flow are changing. Some implications concerning the sound emission by inhomogeneities eventually present in the structure are discussed.

Effects of skeleton structure on necrosis targeting and clearance properties of radioiodinated dianthrones.

PubMed

Zhang, Dongjian; Jiang, Cuihua; Yang, Shengwei; Gao, Meng; Huang, Dejian; Wang, Xiaoning; Shao, Haibo; Feng, Yuanbo; Sun, Ziping; Ni, Yicheng; Zhang, Jian; Yin, Zhiqi

2016-01-01

Necrosis avid agents (NAAs) can be used for diagnose of necrosis-related diseases, evaluation of therapeutic responses and targeted therapeutics of tumor. In order to probe into the effects of molecular skeleton structure on necrosis targeting and clearance properties of radioiodinated dianthrones, four dianthrone compounds with the same substituents but different skeletal structures, namely Hypericin (Hyp), protohypericin (ProHyp), emodin dianthrone mesomer (ED-1) and emodin dianthrone raceme (ED-2) were synthesized and radioiodinated. Then radioiodinated dianthrones were evaluated in vitro for their necrosis avidity in A549 lung cancer cells untreated and treated with H2O2. Their biodistribution and pharmacokinetic properties were determined in rat models of induced necrosis. In vitro cell assay revealed that destruction of rigid skeleton structure dramatically reduced their necrosis targeting ability. Animal studies demonstrated that destruction of rigid skeleton structure dramatically reduced the necrotic tissue uptake and speed up the clearance from the most normal tissues for the studied compounds. Among these (131)I-dianthrones, (131)I-Hyp exhibited the highest uptake and persistent retention in necrotic tissues. Hepatic infarction could be clearly visualized by SPECT/CT using (131)I-Hyp as an imaging probe. The results suggest that the skeleton structure of Hyp is the lead structure for further structure optimization of this class of NAAs.

Progressive structure-based alignment of homologous proteins: Adopting sequence comparison strategies.

PubMed

Joseph, Agnel Praveen; Srinivasan, Narayanaswamy; de Brevern, Alexandre G

2012-09-01

Comparison of multiple protein structures has a broad range of applications in the analysis of protein structure, function and evolution. Multiple structure alignment tools (MSTAs) are necessary to obtain a simultaneous comparison of a family of related folds. In this study, we have developed a method for multiple structure comparison largely based on sequence alignment techniques. A widely used Structural Alphabet named Protein Blocks (PBs) was used to transform the information on 3D protein backbone conformation as a 1D sequence string. A progressive alignment strategy similar to CLUSTALW was adopted for multiple PB sequence alignment (mulPBA). Highly similar stretches identified by the pairwise alignments are given higher weights during the alignment. The residue equivalences from PB based alignments are used to obtain a three dimensional fit of the structures followed by an iterative refinement of the structural superposition. Systematic comparisons using benchmark datasets of MSTAs underlines that the alignment quality is better than MULTIPROT, MUSTANG and the alignments in HOMSTRAD, in more than 85% of the cases. Comparison with other rigid-body and flexible MSTAs also indicate that mulPBA alignments are superior to most of the rigid-body MSTAs and highly comparable to the flexible alignment methods. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

The integrated motion measurement simulation for SOFIA

NASA Astrophysics Data System (ADS)

Kaswekar, Prashant; Greiner, Benjamin; Wagner, Jörg

2014-07-01

The Stratospheric Observatory for Infrared Astronomy SOFIA consists of a B747-SP aircraft, which carries aloft a 2.7-meter reflecting telescope. The image stability goal for SOFIA is 0:2 arc-seconds rms. The performance of the telescope structure is affected by elastic vibrations induced by aeroacoustic and suspension disturbances. Active compensation of such disturbances requires a fast way of estimating the structural motion. Integrated navigation systems are examples of such estimation systems. However they employ a rigid body assumption. A possible extension of these systems to an elastic structure is shown by different authors for one dimensional beam structures taking into account the eigenmodes of the structural system. The rigid body motion as well as the flexible modes of the telescope assembly, however, are coupled among the three axes. Extending a special mathematical approach to three dimensional structures, the aspect of a modal observer based on integrated motion measurement is simulated for SOFIA. It is in general a fusion of different measurement methods by using their benefits and blinding out their disadvantages. There are no mass and stillness properties needed directly in this approach. However, the knowledge of modal properties of the structure is necessary for the implementation of this method. A finite-element model is chosen as a basis to extract the modal properties of the structure.

Finite element normal mode analysis of resistance welding jointed of dissimilar plate hat structure

NASA Astrophysics Data System (ADS)

Nazri, N. A.; Sani, M. S. M.

2017-10-01

Structural joints offer connection between structural element (beam, plate, solid etc.) in order to build a whole assembled structure. The complex behaviour of connecting elements plays a valuable role in characteristics of dynamic such as natural frequencies and mode shapes. In automotive structures, the trustworthiness arrangement of the structure extremely depends on joints. In this paper, top hat structure is modelled and designed with spot welding joint using dissimilar materials which is mild steel 1010 and stainless steel 304, using finite element software. Different types of connector elements such as rigid body element (RBE2), welding joint element (CWELD), and bar element (CBAR) are applied to represent real connection between two dissimilar plates. Normal mode analysis is simulated with different types of joining element in order to determine modal properties. Natural frequencies using RBE2, CBAR and CWELD are compared to equivalent rigid body method. Connection that gives the lowest percentage error among these three will be selected as the most reliable joining for resistance spot weld. From the analysis, it is shown that CWELD is better compared to others in term of weld joining among dissimilar plate materials. It is expected that joint modelling of finite element plays significant role in structural dynamics.

Making Home Sweet and Sturdy: Toxoplasma gondii ppGalNAc-Ts Glycosylate in Hierarchical Order and Confer Cyst Wall Rigidity.

PubMed

Tomita, Tadakimi; Sugi, Tatsuki; Yakubu, Rama; Tu, Vincent; Ma, Yanfen; Weiss, Louis M

2017-01-10

The protozoan intracellular parasite Toxoplasma gondii forms latent cysts in the central nervous system (CNS) and persists for the lifetime of the host. This cyst is cloaked with a glycosylated structure called the cyst wall. Previously, we demonstrated that a mucin-like glycoprotein, CST1, localizes to the cyst wall and confers structural rigidity on brain cysts in a mucin-like domain-dependent manner. The mucin-like domain of CST1 is composed of 20 units of threonine-rich tandem repeats that are O-GalNAc glycosylated. A family of enzymes termed polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts) initiates O-GalNAc glycosylation. To identify which isoforms of ppGalNAc-Ts are responsible for the glycosylation of the CST1 mucin-like domain and to evaluate the function of each ppGalNAc-T in the overall glycosylation of the cyst wall, all five ppGalNAc-T isoforms were deleted individually from the T. gondii genome. The ppGalNAc-T2 and -T3 deletion mutants produced various glycosylation defects on the cyst wall, implying that many cyst wall glycoproteins are glycosylated by T2 and T3. Both T2 and T3 glycosylate the CST1 mucin-like domain, and this glycosylation is necessary for CST1 to confer structural rigidity on the cyst wall. We established that T2 is required for the initial glycosylation of the mucin-like domain and that T3 is responsible for the sequential glycosylation on neighboring acceptor sites, demonstrating hierarchical glycosylation by two distinct initiating and filling-in ppGalNAc-Ts in an intact organism. Toxoplasma gondii is an obligate intracellular parasite that infects a third of the world's population. It can cause severe congenital disease and devastating encephalitis in immunocompromised individuals. We identified two glycosyltransferases, ppGalNAc-T2 and -T3, which are responsible for glycosylating cyst wall proteins in a hierarchical fashion. This glycosylation confers structural rigidity on the brain cyst. Our studies provide new insights into the mechanisms of O-GalNAc glycosylation in T. gondii. Copyright © 2017 Tomita et al.

Numerical study of rigid and flexible wing shapes in hover

NASA Astrophysics Data System (ADS)

Shahzad, Aamer; Tian, Fang-Bao; Young, John; Lai, Joseph C. S.

2017-04-01

This study is focused on evaluating the aerodynamic performance of rigid and isotropic flexible wing shapes defined by the radius of the first moment of wing area ({\\bar{r}}1) at Reynolds number of 6000. An immersed boundary method was used to solve the 3D, viscous, incompressible Navier-Stokes equations, and coupled with an in-house non-linear finite element solver for fluid structure interaction simulations. Numerical simulations of flexible {\\bar{r}}1=0.43,0.53{and}0.63 wing shapes performed with a single degree of freedom flapping shows that thrust and peak lift coefficients increase with {\\bar{r}}1. Higher thrust in the {\\bar{r}}1=0.63 wing is attributed to the large induced pitch angle, and higher peak lift (compared to the rigid counterpart) results from an increase in the stroke amplitude and spanwise deformation of the wing that anchors the leading edge vortex.

Rigid closed-cell polyimide foams for aircraft applications and foam-in-place technology

NASA Technical Reports Server (NTRS)

Gagliani, J.; Straub, P.; Gagliani, J., Jr.

1983-01-01

Significant accomplishments generated are summarized. Testing of closed cell foams, which has resulted in the characterization of compositions which produce rigid foams for use in galley structure applications is reported. It is shown that the density, compressive strength and shear strength of the foams are directly related to the concentrations of the microballoons. The same properties are also directly related to the resin loading. Prototype samples of rigid closed cell foams meeting the requirements of the program were submitted. Investigation of the apparatus to produce polyimide foams using foam in place techniques, resulted in the selection of a spray gun apparatus, capable to deliver a mixture of microballoons and resin binder on substrates which cures to yield a closed cell foam. It is found that the adhesion of the foam on aluminum, titanium and steel substrates is satisfactory. It is concluded that the material meets the mechanical and thermal requirements of the program.

Ab Initio Effective Rovibrational Hamiltonians for Non-Rigid Molecules via Curvilinear VMP2

NASA Astrophysics Data System (ADS)

Changala, Bryan; Baraban, Joshua H.

2017-06-01

Accurate predictions of spectroscopic constants for non-rigid molecules are particularly challenging for ab initio theory. For all but the smallest systems, ``brute force'' diagonalization of the full rovibrational Hamiltonian is computationally prohibitive, leaving us at the mercy of perturbative approaches. However, standard perturbative techniques, such as second order vibrational perturbation theory (VPT2), are based on the approximation that a molecule makes small amplitude vibrations about a well defined equilibrium structure. Such assumptions are physically inappropriate for non-rigid systems. In this talk, we will describe extensions to curvilinear vibrational Møller-Plesset perturbation theory (VMP2) that account for rotational and rovibrational effects in the molecular Hamiltonian. Through several examples, we will show that this approach provides predictions to nearly microwave accuracy of molecular constants including rotational and centrifugal distortion parameters, Coriolis coupling constants, and anharmonic vibrational and tunneling frequencies.

An efficient direct method for image registration of flat objects

NASA Astrophysics Data System (ADS)

Nikolaev, Dmitry; Tihonkih, Dmitrii; Makovetskii, Artyom; Voronin, Sergei

2017-09-01

Image alignment of rigid surfaces is a rapidly developing area of research and has many practical applications. Alignment methods can be roughly divided into two types: feature-based methods and direct methods. Known SURF and SIFT algorithms are examples of the feature-based methods. Direct methods refer to those that exploit the pixel intensities without resorting to image features and image-based deformations are general direct method to align images of deformable objects in 3D space. Nevertheless, it is not good for the registration of images of 3D rigid objects since the underlying structure cannot be directly evaluated. In the article, we propose a model that is suitable for image alignment of rigid flat objects under various illumination models. The brightness consistency assumptions used for reconstruction of optimal geometrical transformation. Computer simulation results are provided to illustrate the performance of the proposed algorithm for computing of an accordance between pixels of two images.

Rigidity in gender-typed behaviors in early childhood: a longitudinal study of ethnic minority children.

PubMed

Halim, May Ling; Ruble, Diane; Tamis-LeMonda, Catherine; Shrout, Patrick E

2013-01-01

A key prediction of cognitive theories of gender development concerns developmental trajectories in the relative strength or rigidity of gender typing. To examine these trajectories in early childhood, 229 children (African American, Mexican American, and Dominican American) were followed annually from age 3 to 5 years, and gender-stereotypical appearance, dress-up play, toy play, and sex segregation were examined. High gender-typing was found across ethnic groups, and most behaviors increased in rigidity, especially from age 3 to 4 years. In addressing controversy surrounding the stability and structure of gender-typing it was found that from year to year, most behaviors showed moderately stable individual differences. Behaviors were uncorrelated within age but showed more concordance in change across time, suggesting that aspects of gender-typing are multidimensional, but still show coherence. © 2013 The Authors. Child Development © 2013 Society for Research in Child Development, Inc.

In-plane inertial coupling in tuned and severely mistuned bladed disks

NASA Technical Reports Server (NTRS)

Crawley, E. F.

1982-01-01

A model has been developed and verified for blade-disk-shaft coupling in rotors due to the in-plane rigid body modes of the disk. An analytic model has been developed which couples the in-plane rigid body modes of the disk on an elastic shaft with the blade bending modes. Bench resonance test were carried out on the M.I.T. Compressor Rotor, typical of research rotors with flexible blades and a thick rigid disk. When the rotor was carefully tuned, the structural coupling of the blades by the disks was confined to zero and one nodal diameter modes, whose modal frequencies were greater than the blade cantilever frequency. In the case of the tuned rotor, and in two cases where severe mistuning was intentionally introduced, agreement between the predicted and observed natural frequencies is excellent. The analytic model was then extended to include the effects of constant angular rotation of the disk.

Modeling the interactions between a prosthetic socket, polyurethane liners and the residual limb in transtibial amputees using non-linear finite element analysis.

PubMed

Simpson, G; Fisher, C; Wright, D K

2001-01-01

Continuing earlier studies into the relationship between the residual limb, liner and socket in transtibial amputees, we describe a geometrically accurate non-linear model simulating the donning of a liner and then a socket. The socket is rigid and rectified and the liner is a polyurethane geltype which is accurately described using non-linear (Mooney-Rivlin) material properties. The soft tissue of the residual limb is modelled as homogeneous, non-linear and hyperelastic and the bone structure within the residual limb is taken as rigid. The work gives an indication of how the stress induced by the process of donning the rigid socket is redistributed by the liner. Ultimately we hope to understand how the liner design might be modified to reduce discomfort. The ANSYS finite element code, version 5.6 is used.

Development of aerial ultrasonic source using cylinder typed vibrating plate with axial nodal mode

NASA Astrophysics Data System (ADS)

Asami, Takuya; Miura, Hikaru

2018-07-01

We developed a high-power aerial ultrasonic source with a cylinder typed vibrating plate combined with two rigid walls that can be directly connected to a pipe in order to solve the difficulty in connecting an ultrasonic source to a pipe containing particles while preventing the particles from leaking. The structure of the vibrating plate combined with two rigid walls that do not vibrate and can obtain a high sound pressure in the space inside the vibrating plate was designed using the finite element method (FEM). We found that the aerial ultrasonic source using the designed vibrating plate slightly vibrates at the rigid walls as designed using FEM and can be connected to other devices. In addition, the obtained sound pressure was around 8.0 kPa (172 dB) at an input electrical power of 7 W.

Homogenized rigid body and spring-mass (HRBSM) model for the pushover analysis of out-of-plane loaded unreinforced and FRP reinforced walls

NASA Astrophysics Data System (ADS)

Bertolesi, Elisa; Milani, Gabriele

2017-07-01

The present paper is devoted to the discussion of a series of unreinforced and FRP retrofitted panels analyzed adopting the Rigid Body and Spring-Mass (HRBSM) model developed by the authors. To this scope, a total of four out of plane loaded masonry walls tested up to failure are considered. At a structural level, the non-linear analyses are conducted replacing the homogenized orthotropic continuum with a rigid element and non-linear spring assemblage by means of which out of plane mechanisms are allowed. FRP retrofitting is modeled adopting two noded truss elements whose mechanical properties are selected in order to describe possible debonding phenomenon or tensile rupture of the strengthening. The outcome provided numerically are compared to the experimental results showing a satisfactory agreement in terms of global pressure-deflection curves and failure mechanisms.

Analytic analysis of auxetic metamaterials through analogy with rigid link systems

NASA Astrophysics Data System (ADS)

Rayneau-Kirkhope, Daniel; Zhang, Chengzhao; Theran, Louis; Dias, Marcelo A.

2018-02-01

In recent years, many structural motifs have been designed with the aim of creating auxetic metamaterials. One area of particular interest in this subject is the creation of auxetic material properties through elastic instability. Such metamaterials switch from conventional behaviour to an auxetic response for loads greater than some threshold value. This paper develops a novel methodology in the analysis of auxetic metamaterials which exhibit elastic instability through analogy with rigid link lattice systems. The results of our analytic approach are confirmed by finite-element simulations for both the onset of elastic instability and post-buckling behaviour including Poisson's ratio. The method gives insight into the relationships between mechanisms within lattices and their mechanical behaviour; as such, it has the potential to allow existing knowledge of rigid link lattices with auxetic paths to be used in the design of future buckling-induced auxetic metamaterials.

Soft-rigid interaction mechanism towards a lobster-inspired hybrid actuator

NASA Astrophysics Data System (ADS)

Chen, Yaohui; Wan, Fang; Wu, Tong; Song, Chaoyang

2018-01-01

Soft pneumatic actuators (SPAs) are intrinsically light-weight, compliant and therefore ideal to directly interact with humans and be implemented into wearable robotic devices. However, they also pose new challenges in describing and sensing their continuous deformation. In this paper, we propose a hybrid actuator design with bio-inspirations from the lobsters, which can generate reconfigurable bending movements through the internal soft chamber interacting with the external rigid shells. This design with joint and link structures enables us to exactly track its bending configurations that previously posed a significant challenge to soft robots. Analytic models are developed to illustrate the soft-rigid interaction mechanism with experimental validation. A robotic glove using hybrid actuators to assist grasping is assembled to illustrate their potentials in safe human-robot interactions. Considering all the design merits, our work presents a practical approach to the design of next-generation robots capable of achieving both good accuracy and compliance.

A minimal length rigid helical peptide motif allows rational design of modular surfactants

NASA Astrophysics Data System (ADS)

Mondal, Sudipta; Varenik, Maxim; Bloch, Daniel Nir; Atsmon-Raz, Yoav; Jacoby, Guy; Adler-Abramovich, Lihi; Shimon, Linda J. W.; Beck, Roy; Miller, Yifat; Regev, Oren; Gazit, Ehud

2017-01-01

Extensive work has been invested in the design of bio-inspired peptide emulsifiers. Yet, none of the formulated surfactants were based on the utilization of the robust conformation and self-assembly tendencies presented by the hydrophobins, which exhibited highest surface activity among all known proteins. Here we show that a minimalist design scheme could be employed to fabricate rigid helical peptides to mimic the rigid conformation and the helical amphipathic organization. These designer building blocks, containing natural non-coded α-aminoisobutyric acid (Aib), form superhelical assemblies as confirmed by crystallography and microscopy. The peptide sequence is amenable to structural modularity and provides the highest stable emulsions reported so far for peptide and protein emulsifiers. Moreover, we establish the ability of short peptides to perform the dual functions of emulsifiers and thickeners, a feature that typically requires synergistic effects of surfactants and polysaccharides. This work provides a different paradigm for the molecular engineering of bioemulsifiers.

Quantitative computed tomography-based predictions of vertebral strength in anterior bending.

PubMed

Buckley, Jenni M; Cheng, Liu; Loo, Kenneth; Slyfield, Craig; Xu, Zheng

2007-04-20

This study examined the ability of QCT-based structural assessment techniques to predict vertebral strength in anterior bending. The purpose of this study was to compare the abilities of QCT-based bone mineral density (BMD), mechanics of solids models (MOS), e.g., bending rigidity, and finite element analyses (FE) to predict the strength of isolated vertebral bodies under anterior bending boundary conditions. Although the relative performance of QCT-based structural measures is well established for uniform compression, the ability of these techniques to predict vertebral strength under nonuniform loading conditions has not yet been established. Thirty human thoracic vertebrae from 30 donors (T9-T10, 20 female, 10 male; 87 +/- 5 years of age) were QCT scanned and destructively tested in anterior bending using an industrial robot arm. The QCT scans were processed to generate specimen-specific FE models as well as trabecular bone mineral density (tBMD), integral bone mineral density (iBMD), and MOS measures, such as axial and bending rigidities. Vertebral strength in anterior bending was poorly to moderately predicted by QCT-based BMD and MOS measures (R2 = 0.14-0.22). QCT-based FE models were better strength predictors (R2 = 0.34-0.40); however, their predictive performance was not statistically different from MOS bending rigidity (P > 0.05). Our results suggest that the poor clinical performance of noninvasive structural measures may be due to their inability to predict vertebral strength under bending loads. While their performance was not statistically better than MOS bending rigidities, QCT-based FE models were moderate predictors of both compressive and bending loads at failure, suggesting that this technique has the potential for strength prediction under nonuniform loads. The current FE modeling strategy is insufficient, however, and significant modifications must be made to better mimic whole bone elastic and inelastic material behavior.

Polymeric binder for explosives

NASA Technical Reports Server (NTRS)

Bissell, E. R.

1972-01-01

Chemical reaction for producing a polymer which can be mixed with explosives to produce a rigid material is discussed. Physical and chemical properties of polymers are described and chemical structure of the polymer is illustrated.

Effect of chain rigidity on network architecture and deformation behavior of glassy polymer networks

NASA Astrophysics Data System (ADS)

Knowles, Kyler Reser

Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of the polymer matrix in regards to strain storage and relaxation mechanisms which ultimately control composite performance throughout manufacturing and use. Through the use of a non-contact, full-field strain measurement technique known as digital image correlation (DIC), we describe and implement useful experiments which quantify matrix and composite parameters necessary for simulation efforts and failure models. The methods are compared to more traditional techniques and show excellent correlation. Further, we established relationships which represent matrix-fiber compatibility in regards to critical processing constraints. The second approach involves a systematic study of epoxy-amine networks which are chemically-similar but differ in chain segment rigidity. Prior research has investigated the isomer effect of glassy polymers, showing sizeable differences in thermal, volumetric, physical, and mechanical properties. This work builds on these themes and shows the apparent isomer effect is rather an effect of chain rigidity. Indeed, it was found that structurally-dissimilar polymer networks exhibit very similar properties as a consequence of their shared average network rigidity. Differences in chain packing, as a consequence of chain rigidity, were shown to alter the physical, volumetric, and mechanical properties of the glassy networks. Chain rigidity was found to directly control deformation mechanisms, which were related to the yielding behavior of the epoxy network series. The unique benefit to our approach is the ability to separate the role of rigidity - an intramolecular parameter - from intermolecular phenomena which otherwise influence network properties.

Computing the Free Energy along a Reaction Coordinate Using Rigid Body Dynamics.

PubMed

Tao, Peng; Sodt, Alexander J; Shao, Yihan; König, Gerhard; Brooks, Bernard R

2014-10-14

The calculations of potential of mean force along complex chemical reactions or rare events pathways are of great interest because of their importance for many areas in chemistry, molecular biology, and material science. The major difficulty for free energy calculations comes from the great computational cost for adequate sampling of the system in high-energy regions, especially close to the reaction transition state. Here, we present a method, called FEG-RBD, in which the free energy gradients were obtained from rigid body dynamics simulations. Then the free energy gradients were integrated along a reference reaction pathway to calculate free energy profiles. In a given system, the reaction coordinates defining a subset of atoms (e.g., a solute, or the quantum mechanics (QM) region of a quantum mechanics/molecular mechanics simulation) are selected to form a rigid body during the simulation. The first-order derivatives (gradients) of the free energy with respect to the reaction coordinates are obtained through the integration of constraint forces within the rigid body. Each structure along the reference reaction path is separately subjected to such a rigid body simulation. The individual free energy gradients are integrated along the reference pathway to obtain the free energy profile. Test cases provided demonstrate both the strengths and weaknesses of the FEG-RBD method. The most significant benefit of this method comes from the fast convergence rate of the free energy gradient using rigid-body constraints instead of restraints. A correction to the free energy due to approximate relaxation of the rigid-body constraint is estimated and discussed. A comparison with umbrella sampling using a simple test case revealed the improved sampling efficiency of FEG-RBD by a factor of 4 on average. The enhanced efficiency makes this method effective for calculating the free energy of complex chemical reactions when the reaction coordinate can be unambiguously defined by a small subset of atoms within the system.

Computing the Free Energy along a Reaction Coordinate Using Rigid Body Dynamics

PubMed Central

2015-01-01

The calculations of potential of mean force along complex chemical reactions or rare events pathways are of great interest because of their importance for many areas in chemistry, molecular biology, and material science. The major difficulty for free energy calculations comes from the great computational cost for adequate sampling of the system in high-energy regions, especially close to the reaction transition state. Here, we present a method, called FEG-RBD, in which the free energy gradients were obtained from rigid body dynamics simulations. Then the free energy gradients were integrated along a reference reaction pathway to calculate free energy profiles. In a given system, the reaction coordinates defining a subset of atoms (e.g., a solute, or the quantum mechanics (QM) region of a quantum mechanics/molecular mechanics simulation) are selected to form a rigid body during the simulation. The first-order derivatives (gradients) of the free energy with respect to the reaction coordinates are obtained through the integration of constraint forces within the rigid body. Each structure along the reference reaction path is separately subjected to such a rigid body simulation. The individual free energy gradients are integrated along the reference pathway to obtain the free energy profile. Test cases provided demonstrate both the strengths and weaknesses of the FEG-RBD method. The most significant benefit of this method comes from the fast convergence rate of the free energy gradient using rigid-body constraints instead of restraints. A correction to the free energy due to approximate relaxation of the rigid-body constraint is estimated and discussed. A comparison with umbrella sampling using a simple test case revealed the improved sampling efficiency of FEG-RBD by a factor of 4 on average. The enhanced efficiency makes this method effective for calculating the free energy of complex chemical reactions when the reaction coordinate can be unambiguously defined by a small subset of atoms within the system. PMID:25328492

Extreme mobility in the Late Pleistocene? Comparing limb biomechanics among fossil Homo, varsity athletes and Holocene foragers.

PubMed

Shaw, Colin N; Stock, Jay T

2013-04-01

Descriptions of Pleistocene activity patterns often derive from comparisons of long bone diaphyseal robusticity across contemporaneous fossilized hominins. The purpose of this study is to augment existing understanding of Pleistocene hominin mobility patterns by interpreting fossil variation through comparisons with a) living human athletes with known activity patterns, and b) Holocene foragers where descriptions of group-level activity patterns are available. Relative tibial rigidity (midshaft tibial rigidity (J)/midshaft humeral rigidity (J)) was compared amongst Levantine and European Neandertals, Levantine and Upper Palaeolithic Homo sapiens, Holocene foragers and living human athletes and controls. Cross-country runners exhibit significantly (p<0.05) greater relative tibial rigidity compared with swimmers, and higher values compared with controls. In contrast, swimmers displayed significantly (p<0.05) lower relative tibial rigidity than both runners and controls. While variation exists among all Holocene H. sapiens, highly terrestrially mobile Later Stone Age (LSA) southern Africans and cross-country runners display the highest relative tibial rigidity, while maritime Andaman Islanders and swimmers display the lowest, with controls falling between. All fossil hominins displayed relative tibial rigidity that exceeded, or was similar to, the highly terrestrially mobile Later Stone Age southern Africans and modern human cross-country runners. The more extreme skeletal structure of most Neandertals and Levantine H. sapiens, as well as the odd Upper Palaeolithic individual, appears to reflect adaptation to intense and/or highly repetitive lower limb (relative to upper limb) loading. This loading may have been associated with bipedal travel, and appears to have been more strenuous than that encountered by even university varsity runners, and Holocene foragers with hunting grounds 2000-3000 square miles in size. Skeletal variation among the athletes and foraging groups is consistent with known or inferred activity profiles, which support the position that the Pleistocene remains reflect adaptation to extremely active and mobile lives. Copyright © 2013 Elsevier Ltd. All rights reserved.

Torque balance, Taylor's constraint and torsional oscillations in a numerical model of the geodynamo

NASA Astrophysics Data System (ADS)

Dumberry, Mathieu; Bloxham, Jeremy

2003-11-01

Theoretical considerations and observations suggest that, to a first approximation, the Earth's dynamo is in a quasi-Taylor state, where the axial Lorentz torque on cylindrical surfaces co-axial with the rotation axis vanishes, except for the part involved in torsional oscillations. The latter are rigid azimuthal accelerations of cylindrical surfaces which oscillate with typical periods of decades. We present a solution of a numerical model of the geodynamo in which rigid accelerations of cylinder surfaces are observed. The underlying dynamic state in the model is not a Taylor state because the Reynolds stresses and viscous torque remain large and provide an effective way to balance a large Lorentz torque. This is a consequence of the limited parameter regime which can be attained numerically. Nevertheless, departures in the torque equilibrium are primarily counterbalanced by rigid accelerations of cylindrical surfaces, which, in turn, excite rigid azimuthal oscillations of the surfaces. We show that the azimuthal motion is indeed quasi-rigid, though the torsional oscillations that are produced in the model probably differ from those in the Earth's core because of the large influence of the Reynolds stresses on their dynamics. We also show that the continual excitation of rigid cylindrical accelerations is produced by the advection of the non-axisymmetric structure of the fields by a mean differential rotation of the cylindrical surfaces which produces disconnections and reconnections and continual fluctuations in the Lorentz torque and Reynolds stresses. We propose that the torque balance in Earth's core may evolve in a similar chaotic fashion, except that the influence of the Reynolds stresses is probably weaker. If this is the case, the Lorentz torque on a cylindrical surface is continually fluctuating, even though its time-averaged value vanishes and satisfies Taylor's constraint. Rigid accelerations of cylindrical surfaces are continually excited by the fluctuations in the Lorentz torque, and the torsional oscillations observed in the geomagnetic data are a mixture of forced and free oscillations.

Stability of non-Watson-Crick G-A/A-G base pair in synthetic DNA and RNA oligonucleotides.

PubMed

Ito, Yuko; Sone, Yumiko; Mizutani, Takaharu

2004-03-01

A non-Watson-Crick G-A/A-G base pair is found in SECIS (selenocysteine-insertion sequence) element in the 3'-untranslated region of Se-protein mRNAs and in the functional site of the hammerhead ribozyme. We studied the stability of G-A/A-G base pair (bold) in 17mer GT(U)GACGGAAACCGGAAC synthetic DNA and RNA oligonucleotides by thermal melting experiments and gel electrophoresis. The measured Tm value of DNA oligonucleotide having G-A/A-G pair showed an intermediate value (58 degrees C) between that of Watson-Crick G-C/C-G base pair (75 degrees C) and that of G-G/A-A of non-base-pair (40 degrees C). Similar thermal melting patterns were obtained with RNA oligonucleotides. This result indicates that the secondary structure of oligonucleotide having G-A/A-G base pair is looser than that of the G-C type Watson-Crick base pair. In the comparison between RNA and DNA having G-A/A-G base pair, the Tm value of the RNA oligonucleotide was 11 degrees C lower than that of DNA, indicating that DNA has a more rigid structure than RNA. The stained pattern of oligonucleotide on polyacrylamide gel clarified that the mobility of the DNA oligonucleotide G-A/A-G base pair changed according to the urea concentration from the rigid state (near the mobility of G-C/C-G oligonucleotide) in the absence of urea to the random state (near the mobility of G-G/A-A oligonucleotide) in 7 M urea. However, the RNA oligonucleotide with G-A/A-G pair moved at an intermediate mobility between that of oligonucleotide with G-C/C-G and of the oligonucleotide with G-G/A-A, and the mobility pattern did not depend on urea concentration. Thus, DNA and RNA oligonucleotides with the G-A/A-G base pair showed a pattern indicating an intermediate structure between the rigid Watson-Crick base pair and the random structure of non-base pair. RNA with G-A/A-G base pair has the intermediate structure not influenced by urea concentration. Finally, this study indicated that the intermediate rigidity imparted by Non-Watson-Crick base pair in SECIS element plays an important role in the selenocysteine expression by UGA codon.

Experimental method to account for structural compliance in nanoindentation measurements

Treesearch

Joseph E. Jakes; Charles R. Frihart; James F. Beecher; Robert J. Moon; D. S. Stone

2008-01-01

The standard Oliver–Pharr nanoindentation analysis tacitly assumes that the specimen is structurally rigid and that it is both semi-infinite and homogeneous. Many specimens violate these assumptions. We show that when the specimen flexes or possesses heterogeneities, such as free edges or interfaces between regions of different properties, artifacts arise...

29 CFR 1910.155 - Scope, application and definitions applicable to this subpart.

Code of Federal Regulations, 2014 CFR

2014-07-01

... moisture absorption (caking) as well as to provide proper flow capabilities. Dry chemical does not include... require formal classroom instruction. (15) Enclosed structure means a structure with a roof or ceiling and... a rigid shell, energy absorption system, and chin strap intended to be worn to provide protection...

29 CFR 1910.155 - Scope, application and definitions applicable to this subpart.

Code of Federal Regulations, 2013 CFR

2013-07-01

... moisture absorption (caking) as well as to provide proper flow capabilities. Dry chemical does not include... require formal classroom instruction. (15) Enclosed structure means a structure with a roof or ceiling and... a rigid shell, energy absorption system, and chin strap intended to be worn to provide protection...

29 CFR 1910.155 - Scope, application and definitions applicable to this subpart.

Code of Federal Regulations, 2011 CFR

2011-07-01

... moisture absorption (caking) as well as to provide proper flow capabilities. Dry chemical does not include... require formal classroom instruction. (15) Enclosed structure means a structure with a roof or ceiling and... a rigid shell, energy absorption system, and chin strap intended to be worn to provide protection...

29 CFR 1910.155 - Scope, application and definitions applicable to this subpart.

Code of Federal Regulations, 2012 CFR

2012-07-01

... moisture absorption (caking) as well as to provide proper flow capabilities. Dry chemical does not include... require formal classroom instruction. (15) Enclosed structure means a structure with a roof or ceiling and... a rigid shell, energy absorption system, and chin strap intended to be worn to provide protection...

Integrated Approach to the Dynamics and Control of Maneuvering Flexible Aircraft

NASA Technical Reports Server (NTRS)

Waszak, Martin R. (Technical Monitor); Meirovitch, Leonard; Tuzcu, Ilhan

2003-01-01

This work uses a fundamental approach to the problem of simulating the flight of flexible aircraft. To this end, it integrates into a single formulation the pertinent disciplines, namely, analytical dynamics, structural dynamics, aerodynamics, and controls. It considers both the rigid body motions of the aircraft, three translations (forward motion, sideslip and plunge) and three rotations (roll, pitch and yaw), and the elastic deformations of every point of the aircraft, as well as the aerodynamic, propulsion, gravity and control forces. The equations of motion are expressed in a form ideally suited for computer processing. A perturbation approach yields a flight dynamics problem for the motions of a quasi-rigid aircraft and an 'extended aeroelasticity' problem for the elastic deformations and perturbations in the rigid body motions, with the solution of the first problem entering as an input into the second problem. The control forces for the flight dynamics problem are obtained by an 'inverse' process and the feedback controls for the extended aeroservoelasticity problem are determined by the LQG theory. A numerical example presents time simulations of rigid body perturbations and elastic deformations about 1) a steady level flight and 2) a level steady turn maneuver.

Polyurethane rigid foam, a proven thermal insulating material for applications between +130°C and -196°C

NASA Astrophysics Data System (ADS)

Demharter, Anton

Polyurethanes are high molecular weight polymers based on the polyaddition of polyfunctional hydroxyl-group containing compounds and polyisocyanates. A wide variety of properties can be tailored to fulfil the requirements of different applications: soft to hard, plastic, elastic or thermoset, compact or foamed. Compared with other insulating materials, PUR rigid foam is highly competitive. There are five product-related advantages: lowest thermal conductivity, high mechanical and chemical properties at both high and low temperatures, all major international fire safety requirements can be satisfied, the ability to form sandwich structures with various facer materials, and the new generation of PUR is CFC-free and recyclable. Rigid polyurethane foams perform well in most areas of low-temperature insulations. Products in density ranging from approximately 30 to 200 kg m -3 withstand temperatures down to -196°C. Typical applications are: refrigerated vehicles, road and rail tankers, vessels for refrigerated cargo, pipelines, liquid gas tanks for LPG and LNG and cryogenic wind tunnels. The paper presents applications, corresponding properties of the rigid foams used, and also other insulating materials in competition to PUR are discussed.

Periodicity in Attachment Organelle Revealed by Electron Cryotomography Suggests Conformational Changes in Gliding Mechanism of Mycoplasma pneumoniae

PubMed Central

Kawamoto, Akihiro; Matsuo, Lisa; Kato, Takayuki; Yamamoto, Hiroki

2016-01-01

ABSTRACT Mycoplasma pneumoniae, a pathogenic bacterium, glides on host surfaces using a unique mechanism. It forms an attachment organelle at a cell pole as a protrusion comprised of knoblike surface structures and an internal core. Here, we analyzed the three-dimensional structure of the organelle in detail by electron cryotomography. On the surface, knoblike particles formed a two-dimensional array, albeit with limited regularity. Analyses using a nonbinding mutant and an antibody showed that the knoblike particles correspond to a naplike structure that has been observed by negative-staining electron microscopy and is likely to be formed as a complex of P1 adhesin, the key protein for binding and gliding. The paired thin and thick plates feature a rigid hexagonal lattice and striations with highly variable repeat distances, respectively. The combination of variable and invariant structures in the internal core and the P1 adhesin array on the surface suggest a model in which axial extension and compression of the thick plate along a rigid thin plate is coupled with attachment to and detachment from the substrate during gliding. PMID:27073090

The LATDYN user's manual

NASA Technical Reports Server (NTRS)

Housner, J. M.; Mcgowan, P. E.; Abrahamson, A. L.; Powell, M. G.

1986-01-01

The LATDYN User's Manual presents the capabilities and instructions for the LATDYN (Large Angle Transient DYNamics) computer program. The LATDYN program is a tool for analyzing the controlled or uncontrolled dynamic transient behavior of interconnected deformable multi-body systems which can undergo large angular motions of each body relative other bodies. The program accommodates large structural deformation as well as large rigid body rotations and is applicable, but not limited to, the following areas: (1) development of large flexible space structures; (2) slewing of large space structure components; (3) mechanisms with rigid or elastic components; and (4) robotic manipulations of beam members. Presently the program is limited to two dimensional problems, but in many cases, three dimensional problems can be exactly or approximately reduced to two dimensions. The program uses convected finite elements to affect the large angular motions involved in the analysis. General geometry is permitted. Detailed user input and output specifications are provided and discussed with example runstreams. To date, LATDYN has been configured for CDC/NOS and DEC VAX/VMS machines. All coding is in ANSII-77 FORTRAN. Detailed instructions regarding interfaces with particular computer operating systems and file structures are provided.

Computational multiobjective topology optimization of silicon anode structures for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Mitchell, Sarah L.; Ortiz, Michael

2016-09-01

This study utilizes computational topology optimization methods for the systematic design of optimal multifunctional silicon anode structures for lithium-ion batteries. In order to develop next generation high performance lithium-ion batteries, key design challenges relating to the silicon anode structure must be addressed, namely the lithiation-induced mechanical degradation and the low intrinsic electrical conductivity of silicon. As such this work considers two design objectives, the first being minimum compliance under design dependent volume expansion, and the second maximum electrical conduction through the structure, both of which are subject to a constraint on material volume. Density-based topology optimization methods are employed in conjunction with regularization techniques, a continuation scheme, and mathematical programming methods. The objectives are first considered individually, during which the influence of the minimum structural feature size and prescribed volume fraction are investigated. The methodology is subsequently extended to a bi-objective formulation to simultaneously address both the structural and conduction design criteria. The weighted sum method is used to derive the Pareto fronts, which demonstrate a clear trade-off between the competing design objectives. A rigid frame structure was found to be an excellent compromise between the structural and conduction design criteria, providing both the required structural rigidity and direct conduction pathways. The developments and results presented in this work provide a foundation for the informed design and development of silicon anode structures for high performance lithium-ion batteries.

Nanostructure Determination by Co-Refining Models to Multiple Datasets

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

Billinge, Simon J. L.

2011-05-31

The results of the work are contained in the publications resulting from the grant (which are listed below). Here I summarize the main findings from the last period of the award, 2006-2007: • Published a paper in Science with Igor Levin outlining the “Nanostructure Problem”, our inability to solve structure at the nanoscale. • Published a paper in Nature demonstrating the first ever ab-initio structure determination of a nanoparticle from atomic pair distribution function (PDF) data. • Published one book and 3 overview articles on PDF methods and the nanostructure problem. • Completed a project that sought to find amore » structural response to the presence of the so-called “intermediate phase” in network glasses which appears close to the rigidity percolation threshold in these systems. The main result was that we did not see convincing evidence for this, which drew into doubt the idea that Ge xSe 1-x glasses were a model system exhibiting rigidity percolation.« less

Structural singularities in Ge(x)Te(100-x) films.

PubMed

Piarristeguy, A A; Micoulaut, M; Escalier, R; Jóvári, P; Kaban, I; van Eijk, J; Luckas, J; Ravindren, S; Boolchand, P; Pradel, A

2015-08-21

Structural and calorimetric investigation of Ge(x)Te(100-x) films over wide range of concentration 10 < x < 50 led to evidence two structural singularities at x ∼ 22 at. % and x ∼ 33-35 at. %. Analysis of bond distribution, bond variability, and glass thermal stability led to conclude to the origin of the first singularity being the flexible/rigid transition proposed in the framework of rigidity model and the origin of the second one being the disappearance of the undercooled region resulting in amorphous materials with statistical distributions of bonds. While the first singularity signs the onset of the Ge-Ge homopolar bonds, the second is related to compositions where enhanced Ge-Ge correlations at intermediate lengthscales (7.7 Å) are observed. These two threshold compositions correspond to recently reported resistance drift threshold compositions, an important support for models pointing the breaking of homopolar Ge-Ge bonds as the main phenomenon behind the ageing of phase change materials.

Highly conductive transparent organic electrodes with multilayer structures for rigid and flexible optoelectronics.

PubMed

Guo, Xiaoyang; Liu, Xingyuan; Lin, Fengyuan; Li, Hailing; Fan, Yi; Zhang, Nan

2015-05-27

Transparent electrodes are essential components for optoelectronic devices, such as touch panels, organic light-emitting diodes, and solar cells. Indium tin oxide (ITO) is widely used as transparent electrode in optoelectronic devices. ITO has high transparency and low resistance but contains expensive rare elements, and ITO-based devices have poor mechanical flexibility. Therefore, alternative transparent electrodes with excellent opto-electrical performance and mechanical flexibility will be greatly demanded. Here, organics are introduced into dielectric-metal-dielectric structures to construct the transparent electrodes on rigid and flexible substrates. We show that organic-metal-organic (OMO) electrodes have excellent opto-electrical properties (sheet resistance of below 10 Ω sq(-1) at 85% transmission), mechanical flexibility, thermal and environmental stabilities. The OMO-based polymer photovoltaic cells show performance comparable to that of devices based on ITO electrodes. This OMO multilayer structure can therefore be used to produce transparent electrodes suitable for use in a wide range of optoelectronic devices.

Principal Effects of Axial Load on Moment-Distribution Analysis of Rigid Structures

NASA Technical Reports Server (NTRS)

James, Benjamin Wylie

1935-01-01

This thesis presents the method of moment distribution modified to include the effect of axial load upon the bending moments. This modification makes it possible to analyze accurately complex structures, such as rigid fuselage trusses, that heretofore had to be analyzed by approximate formulas and empirical rules. The method is simple enough to be practicable even for complex structures, and it gives a means of analysis for continuous beams that is simpler than the extended three-moment equation now in common use. When the effect of axial load is included, it is found that the basic principles of moment distribution remain unchanged, the only difference being that the factors used, instead of being constants for a given member, become functions of the axial load. Formulas have been developed for these factors, and curves plotted so that their applications requires no more work than moment distribution without axial load. Simple problems have been included to illustrate the use of the curves.

Tuning zinc(II) coordination architectures by rigid long bis(triazole) and different carboxylates: Synthesis, structures and fluorescence properties

NASA Astrophysics Data System (ADS)

Wang, Xiao-xiao; Li, Zuo-xi; Yu, Baoyi; Van Hecke, Kristof; Cui, Guang-hua

2015-10-01

Three metal-organic coordination polymers containing rigid bis(triazole) ligand, namely, [Zn1.5(btb)(nbta)(H2O)]n (1), {[Zn(btb)(3-nph)]·(H2O)}n (2) and [Zn(btb)(4-nph)]n (3) (btb = 4,4‧-bis(1,2,4-triazolyl-1-yl)-biphenyl, 3-H2nph = 3-nitrophthalic acid, H3nbta = 5-nitro-1,2,3-benzenetricarboxylic acid, and 4-H2nph = 4-nitrophthalic acid) were synthesized under hydrothermal conditions and structurally characterized by X-ray single-crystal diffraction. Complex 1 possesses an interesting 3D coordination framework with a rarely binodal (4,4)-connected frl topological structure. Complexes 2 and 3 exhibit similiar 2D (4,4) grid layers with different point symbol (44 · 64) in 2 and (44 · 62) in 3. Furthermore, thermal stability of these compounds has been discussed. Complexes 1-3 exhibit strong solid-state fluorescence at room temperature in solid state.

Dendrimer-protein interactions versus dendrimer-based nanomedicine.

PubMed

Shcharbin, Dzmitry; Shcharbina, Natallia; Dzmitruk, Volha; Pedziwiatr-Werbicka, Elzbieta; Ionov, Maksim; Mignani, Serge; de la Mata, F Javier; Gómez, Rafael; Muñoz-Fernández, Maria Angeles; Majoral, Jean-Pierre; Bryszewska, Maria

2017-04-01

Dendrimers are hyperbranched polymers belonging to the huge class of nanomedical devices. Their wide application in biology and medicine requires understanding of the fundamental mechanisms of their interactions with biological systems. Summarizing, electrostatic force plays the predominant role in dendrimer-protein interactions, especially with charged dendrimers. Other kinds of interactions have been proven, such as H-bonding, van der Waals forces, and even hydrophobic interactions. These interactions depend on the characteristics of both participants: flexibility and surface charge of a dendrimer, rigidity of protein structure and the localization of charged amino acids at its surface. pH and ionic strength of solutions can significantly modulate interactions. Ligands and cofactors attached to a protein can also change dendrimer-protein interactions. Binding of dendrimers to a protein can change its secondary structure, conformation, intramolecular mobility and functional activity. However, this strongly depends on rigidity versus flexibility of a protein's structure. In addition, the potential applications of dendrimers to nanomedicine are reviwed related to dendrimer-protein interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

Roll Damping Derivatives from Generalized Lifting-Surface Theory and Wind Tunnel Forced-Oscillation Tests

NASA Technical Reports Server (NTRS)

Pototzky, Anthony S; Murphy, Patrick C.

2014-01-01

Improving aerodynamic models for adverse loss-of-control conditions in flight is an area being researched under the NASA Aviation Safety Program. Aerodynamic models appropriate for loss of control conditions require a more general mathematical representation to predict nonlinear unsteady behaviors. As more general aerodynamic models are studied that include nonlinear higher order effects, the possibility of measurements that confound aerodynamic and structural responses are probable. In this study an initial step is taken to look at including structural flexibility in analysis of rigid-body forced-oscillation testing that accounts for dynamic rig, sting and balance flexibility. Because of the significant testing required and associated costs in a general study, it makes sense to capitalize on low cost analytical methods where possible, especially where structural flexibility can be accounted for by a low cost method. This paper provides an initial look at using linear lifting surface theory applied to rigid-body aircraft roll forced-oscillation tests.

Confined semiflexible polymers suppress fluctuations of soft membrane tubes.

PubMed

Mirzaeifard, Sina; Abel, Steven M

2016-02-14

We use Monte Carlo computer simulations to investigate tubular membrane structures with and without semiflexible polymers confined inside. At small values of membrane bending rigidity, empty fluid and non-fluid membrane tubes exhibit markedly different behavior, with fluid membranes adopting irregular, highly fluctuating shapes and non-fluid membranes maintaining extended tube-like structures. Fluid membranes, unlike non-fluid membranes, exhibit a local maximum in specific heat as their bending rigidity increases. The peak is coincident with a transition to extended tube-like structures. We further find that confining a semiflexible polymer within a fluid membrane tube reduces the specific heat of the membrane, which is a consequence of suppressed membrane shape fluctuations. Polymers with a sufficiently large persistence length can significantly deform the membrane tube, with long polymers leading to localized bulges in the membrane that accommodate regions in which the polymer forms loops. Analytical calculations of the energies of idealized polymer-membrane configurations provide additional insight into the formation of polymer-induced membrane deformations.

Experimental demonstrations in audible frequency range of band gap tunability and negative refraction in two-dimensional sonic crystal.

PubMed

Pichard, Hélène; Richoux, Olivier; Groby, Jean-Philippe

2012-10-01

The propagation of audible acoustic waves in two-dimensional square lattice tunable sonic crystals (SC) made of square cross-section infinitely rigid rods embedded in air is investigated experimentally. The band structure is calculated with the plane wave expansion (PWE) method and compared with experimental measurements carried out on a finite extend structure of 200 cm width, 70 cm depth and 15 cm height. The structure is made of square inclusions of 5 cm side with a periodicity of L = 7.5 cm placed inbetween two rigid plates. The existence of tunable complete band gaps in the audible frequency range is demonstrated experimentally by rotating the scatterers around their vertical axis. Negative refraction is then analyzed by use of the anisotropy of the equi-frequency surface (EFS) in the first band and of a finite difference time domain (FDTD) method. Experimental results finally show negative refraction in the audible frequency range.

Chaos in a restricted problem of rotation of a rigid body with a fixed point

NASA Astrophysics Data System (ADS)

Borisov, A. V.; Kilin, A. A.; Mamaev, I. S.

2008-06-01

In this paper, we consider the transition to chaos in the phase portrait of a restricted problem of rotation of a rigid body with a fixed point. Two interrelated mechanisms responsible for chaotization are indicated: (1) the growth of the homoclinic structure and (2) the development of cascades of period doubling bifurcations. On the zero level of the area integral, an adiabatic behavior of the system (as the energy tends to zero) is noted. Meander tori induced by the break of the torsion property of the mapping are found.

Gyre and gimble: a maximum-likelihood replacement for Patterson correlation refinement.

PubMed

McCoy, Airlie J; Oeffner, Robert D; Millán, Claudia; Sammito, Massimo; Usón, Isabel; Read, Randy J

2018-04-01

Descriptions are given of the maximum-likelihood gyre method implemented in Phaser for optimizing the orientation and relative position of rigid-body fragments of a model after the orientation of the model has been identified, but before the model has been positioned in the unit cell, and also the related gimble method for the refinement of rigid-body fragments of the model after positioning. Gyre refinement helps to lower the root-mean-square atomic displacements between model and target molecular-replacement solutions for the test case of antibody Fab(26-10) and improves structure solution with ARCIMBOLDO_SHREDDER.

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter deployment repeatability. Also, an interesting creep effect was discovered, that a hinges deployment error would decrease with time.

Structural analysis of hollow blades: Torsional stress analysis of hollow fan blades for aircraft jet engines

NASA Technical Reports Server (NTRS)

Ogawa, A.; Sofue, Y.; Isobe, T.

1979-01-01

A torsional stress analysis of hollow fans blades by the finite element method is presented. The fans are considered to be double circular arc blades, hollowed 30 percent, and twisted by a component of the centrifugal force by the rated revolution. The effects of blade hollowing on strength and rigidity are discussed. The effects of reinforcing webs, placed in the hollowed section in varying numbers and locations, on torsional rigidity and the convergence of stresses, are reported. A forecast of the 30 percent hollowing against torsional loadings is discussed.

Real-time 3D visualization of the thoraco-abdominal surface during breathing with body movement and deformation extraction.

PubMed

Povšič, K; Jezeršek, M; Možina, J

2015-07-01

Real-time 3D visualization of the breathing displacements can be a useful diagnostic tool in order to immediately observe the most active regions on the thoraco-abdominal surface. The developed method is capable of separating non-relevant torso movement and deformations from the deformations that are solely related to breathing. This makes it possible to visualize only the breathing displacements. The system is based on the structured laser triangulation principle, with simultaneous spatial and color data acquisition of the thoraco-abdominal region. Based on the tracking of the attached passive markers, the torso movement and deformation is compensated using rigid and non-rigid transformation models on the three-dimensional (3D) data. The total time of 3D data processing together with visualization equals 20 ms per cycle.In vitro verification of the rigid movement extraction was performed using the iterative closest point algorithm as a reference. Furthermore, a volumetric evaluation on a live subject was performed to establish the accuracy of the rigid and non-rigid model. The root mean square deviation between the measured and the reference volumes shows an error of  ±0.08 dm(3) for rigid movement extraction. Similarly, the error was calculated to be  ±0.02 dm(3) for torsional deformation extraction and  ±0.11 dm(3) for lateral bending deformation extraction. The results confirm that during the torso movement and deformation, the proposed method is sufficiently accurate to visualize only the displacements related to breathing. The method can be used, for example, during the breathing exercise on an indoor bicycle or a treadmill.

Dynamics, thermodynamics and structure of liquids and supercritical fluids: crossover at the Frenkel line

NASA Astrophysics Data System (ADS)

Fomin, Yu D.; Ryzhov, V. N.; Tsiok, E. N.; Proctor, J. E.; Prescher, C.; Prakapenka, V. B.; Trachenko, K.; Brazhkin, V. V.

2018-04-01

We review recent work aimed at understanding dynamical and thermodynamic properties of liquids and supercritical fluids. The focus of our discussion is on solid-like transverse collective modes, whose evolution in the supercritical fluids enables one to discuss the main properties of the Frenkel line separating rigid liquid-like and non-rigid gas-like supercritical states. We subsequently present recent experimental evidence of the Frenkel line showing that structural and dynamical crossovers are seen at a pressure and temperature corresponding to the line as predicted by theory and modelling. Finally, we link dynamical and thermodynamic properties of liquids and supercritical fluids by the new calculation of liquid energy governed by the evolution of solid-like transverse modes. The disappearance of those modes at high temperature results in the observed decrease of heat capacity.

The structure and evolution of coronal holes

NASA Technical Reports Server (NTRS)

Timothy, A. F.; Krieger, A. S.; Vaiana, G. S.

1975-01-01

Soft X-ray observations of coronal holes are analyzed to determine the structure, temporal evolution, and rotational properties of those features as well as possible mechanisms which may account for their almost rigid rotational characteristics. It is shown that coronal holes are open features with a divergent magnetic-field configuration resulting from a particular large-scale magnetic-field topology. They are apparently formed when the successive emergence and dispersion of active-region fields produce a swath of unipolar field founded by fields of opposite polarity, and they die when large-scale field patterns emerge which significantly distort the original field configuration. Two types of holes are described (compact and elongated), and three possible rotation mechanisms are considered: a rigidly rotating subphotospheric phenomenon, a linking of high and low latitudes by closed field lines, and an interaction between moving coronal material and open field lines.

Hydrodynamic Impact of a System with a Single Elastic Mode II : Comparison of Experimental Force and Response with Theory

NASA Technical Reports Server (NTRS)

Miller, Robert W; Merten, Kenneth F

1952-01-01

Hydrodynamic impact tests were made on an elastic model approximating a two-mass spring system to determine experimentally the effects of structural flexibility on the hydrodynamic loads encountered during seaplane landing impacts and to correlate the results with theory. A flexible seaplane was represented by a two-mass spring system consisting of a rigid prismatic float connected to a rigid upper mass by an elastic structure. The model had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. The tests were conducted in smooth water at fixed trims and included both high and low flight-path angles and a range of velocity. Theoretical and experimental comparisons indicated that the theoretical results agreed well with the experimental results.

Rigid Body Modes Influence On Microvibration Analysis-Application To Swarm

NASA Astrophysics Data System (ADS)

Laduree, G.; Fransen, S.; Baldesi, G.; Pflieger, I.

2012-07-01

Microvibrations are defined as low level mechanical disturbances affecting payload performance, generated by mobile parts or mechanism operating on-board the spacecraft, like momentum or reaction wheels, pointing mechanism, cryo-coolers or thrusters. The disturbances caused by these sources are transmitted through the spacecraft structure and excite modes of that structure or elements of the payload impacting its performance (e.g. Line of sight rotations inducing some image quality degradation). The dynamic interaction between these three elements (noise source, spacecraft structure and sensitive receiver) makes the microvibration prediction a delicate problem. Microvibration sources are generally of concern in the frequency range from a few Hz to 1000 Hz. However, in some specific cases, high stability at lower frequencies might be requested. This is the case of the SWARM mission, whose objectives are to provide the best ever survey of the geomagnetic field and its temporal evolution as well as supplementary information for studying the interaction of the magnetic field with other physical quantities describing the Earth system (e.g. ocean circulation). Among its instruments, SWARM is embarking a very sensitive 6-axis accelerometer in the low frequency range (10-8 m/s2 or rad/s2 between 10-4 and 0.1 Hz) located at its Centre of Gravity and an Absolute Scalar Magnetometer located at the tip of a boom far from the spacecraft body. The ASM performs its measurements by rotating an alternative magnetic field around its main axis thanks to a piezo-electric motor. This repeated disturbance might generate some pollution of the accelerometer science data. The objective of this work is to focus on the interaction of the rigid body mode calculation method with the elastic contribution of the normal modes excited by the noise source frequency content. It has indeed been reported in the past that NASTRAN Lanczos rigid body modes may lead to inaccurate rigid-body accelerations affecting steady state responses due to numerical roundoffs coming from the coupled mode shape extraction method and from the associated non numerical zeros frequencies. Geometric rigid body modes are usually the preferred solution for dynamic transient analysis but are not retained by NASTRAN when the chosen eigensolver is Lanczos, even using a SUPORT card. The SWARM microvibration problem described above has been considered as a benchmark case for various codes (NASTRAN, PERMAS, DCAP - multi-body software) and methods (direct or modal transients). A specific DMAP in NASTRAN has been written to overcome the limitation imposed by the Lanczos method and considerations on the conditioning of the FEM are discussed. An assessment on the accuracy of the different rigid body modes calculation methods is finally proposed.

A systematic analysis of scoring functions in rigid-body protein docking: The delicate balance between the predictive rate improvement and the risk of overtraining.

PubMed

Barradas-Bautista, Didier; Moal, Iain H; Fernández-Recio, Juan

2017-07-01

Protein-protein interactions play fundamental roles in biological processes including signaling, metabolism, and trafficking. While the structure of a protein complex reveals crucial details about the interaction, it is often difficult to acquire this information experimentally. As the number of interactions discovered increases faster than they can be characterized, protein-protein docking calculations may be able to reduce this disparity by providing models of the interacting proteins. Rigid-body docking is a widely used docking approach, and is often capable of generating a pool of models within which a near-native structure can be found. These models need to be scored in order to select the acceptable ones from the set of poses. Recently, more than 100 scoring functions from the CCharPPI server were evaluated for this task using decoy structures generated with SwarmDock. Here, we extend this analysis to identify the predictive success rates of the scoring functions on decoys from three rigid-body docking programs, ZDOCK, FTDock, and SDOCK, allowing us to assess the transferability of the functions. We also apply set-theoretic measure to test whether the scoring functions are capable of identifying near-native poses within different subsets of the benchmark. This information can provide guides for the use of the most efficient scoring function for each docking method, as well as instruct future scoring functions development efforts. Proteins 2017; 85:1287-1297. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Motor phenotype and magnetic resonance measures of basal ganglia iron levels in Parkinson's disease☆

PubMed Central

Bunzeck, Nico; Singh-Curry, Victoria; Eckart, Cindy; Weiskopf, Nikolaus; Perry, Richard J.; Bain, Peter G.; Düzel, Emrah; Husain, Masud

2013-01-01

Background In Parkinson's disease the degree of motor impairment can be classified with respect to tremor dominant and akinetic rigid features. While tremor dominance and akinetic rigidity might represent two ends of a continuum rather than discrete entities, it would be important to have non-invasive markers of any biological differences between them in vivo, to assess disease trajectories and response to treatment, as well as providing insights into the underlying mechanisms contributing to heterogeneity within the Parkinson's disease population. Methods Here, we used magnetic resonance imaging to examine whether Parkinson's disease patients exhibit structural changes within the basal ganglia that might relate to motor phenotype. Specifically, we examined volumes of basal ganglia regions, as well as transverse relaxation rate (a putative marker of iron load) and magnetization transfer saturation (considered to index structural integrity) within these regions in 40 individuals. Results We found decreased volume and reduced magnetization transfer within the substantia nigra in Parkinson's disease patients compared to healthy controls. Importantly, there was a positive correlation between tremulous motor phenotype and transverse relaxation rate (reflecting iron load) within the putamen, caudate and thalamus. Conclusions Our findings suggest that akinetic rigid and tremor dominant symptoms of Parkinson's disease might be differentiated on the basis of the transverse relaxation rate within specific basal ganglia structures. Moreover, they suggest that iron load within the basal ganglia makes an important contribution to motor phenotype, a key prognostic indicator of disease progression in Parkinson's disease. PMID:24025315

The Energy Landscape Analysis of Cancer Mutations in Protein Kinases

PubMed Central

Dixit, Anshuman; Verkhivker, Gennady M.

2011-01-01

The growing interest in quantifying the molecular basis of protein kinase activation and allosteric regulation by cancer mutations has fueled computational studies of allosteric signaling in protein kinases. In the present study, we combined computer simulations and the energy landscape analysis of protein kinases to characterize the interplay between oncogenic mutations and locally frustrated sites as important catalysts of allostetric kinase activation. While structurally rigid kinase core constitutes a minimally frustrated hub of the catalytic domain, locally frustrated residue clusters, whose interaction networks are not energetically optimized, are prone to dynamic modulation and could enable allosteric conformational transitions. The results of this study have shown that the energy landscape effect of oncogenic mutations may be allosteric eliciting global changes in the spatial distribution of highly frustrated residues. We have found that mutation-induced allosteric signaling may involve a dynamic coupling between structurally rigid (minimally frustrated) and plastic (locally frustrated) clusters of residues. The presented study has demonstrated that activation cancer mutations may affect the thermodynamic equilibrium between kinase states by allosterically altering the distribution of locally frustrated sites and increasing the local frustration in the inactive form, while eliminating locally frustrated sites and restoring structural rigidity of the active form. The energy landsape analysis of protein kinases and the proposed role of locally frustrated sites in activation mechanisms may have useful implications for bioinformatics-based screening and detection of functional sites critical for allosteric regulation in complex biomolecular systems. PMID:21998754

Active vibration suppression of self-excited structures using an adaptive LMS algorithm

NASA Astrophysics Data System (ADS)

Danda Roy, Indranil

The purpose of this investigation is to study the feasibility of an adaptive feedforward controller for active flutter suppression in representative linear wing models. The ability of the controller to suppress limit-cycle oscillations in wing models having root springs with freeplay nonlinearities has also been studied. For the purposes of numerical simulation, mathematical models of a rigid and a flexible wing structure have been developed. The rigid wing model is represented by a simple three-degree-of-freedom airfoil while the flexible wing is modelled by a multi-degree-of-freedom finite element representation with beam elements for bending and rod elements for torsion. Control action is provided by one or more flaps attached to the trailing edge and extending along the entire wing span for the rigid model and a fraction of the wing span for the flexible model. Both two-dimensional quasi-steady aerodynamics and time-domain unsteady aerodynamics have been used to generate the airforces in the wing models. An adaptive feedforward controller has been designed based on the filtered-X Least Mean Squares (LMS) algorithm. The control configuration for the rigid wing model is single-input single-output (SISO) while both SISO and multi-input multi-output (MIMO) configurations have been applied on the flexible wing model. The controller includes an on-line adaptive system identification scheme which provides the LMS controller with a reasonably accurate model of the plant. This enables the adaptive controller to track time-varying parameters in the plant and provide effective control. The wing models in closed-loop exhibit highly damped responses at airspeeds where the open-loop responses are destructive. Simulations with the rigid and the flexible wing models in a time-varying airstream show a 63% and 53% increase, respectively, over their corresponding open-loop flutter airspeeds. The ability of the LMS controller to suppress wing store flutter in the two models has also been investigated. With 10% measurement noise introduced in the flexible wing model, the controller demonstrated good robustness to the extraneous disturbances. In the examples studied it is found that adaptation is rapid enough to successfully control flutter at accelerations in the airstream of up to 15 ft/sec2 for the rigid wing model and 9 ft/sec2 for the flexible wing model.

Influence of Pre-Existing Structure on Sill Geometry in the San Rafael Volcanic Field, Central Utah

NASA Astrophysics Data System (ADS)

Ferwerda, B.; Wetmore, P. H.; Connor, C.; Kruse, S. E.; Kiyosugi, K.; Kiflu, H. G.

2011-12-01

Sills have been hypothesized to be formed at rigidity contrasts between layers or at the level of neutral buoyancy of the intruding magma body. Recent field observations of sills in the San Rafael Volcanic Field (SRVF) in central Utah conflict with both of these hypotheses, suggesting that something else may control the distribution of sills in the crust. This study examines the role pre-existing structure plays in determining the distribution and geometry of sills in the SRVF. Primarily, sills will be thickest in the hinge zone of synclines and thinnest towards the limbs. The SRVF consists of a series of dikes, conduits and sills intruded into the J-Kr strata of the western Colorado Plateau. The structure of the SRVF consists of a series of broad wavelength folds truncated by a major thrust fault as determined by a gravity profile across structure. There are several sill complexes in the area whose geometry and relationships with the host rock are unaccounted for by these hypotheses. At large scale, sills follow structural trends in the host rock. Sills are either oriented with regional dips, or follow the trends of folds in the area. One sill, in particular, intruded into a syncline and thins towards the limb of the fold. However, sills behave differently at smaller spatial scales. The smaller scale behavior is incongruent with sills forming at rigidity contrasts or at the level of neutral buoyancy. First, sills form tiered structures intruding at multiple stratigraphic levels within the field area, and in limited geographic extent. Geophysical surveys confirm tiered sill structures in the subsurface. Individual sills also change stratigraphic levels, sometimes, very abruptly, moving vertically up to 30 meters in short horizontal distances. Sills also form networks in anastomosing structures that cut across stratigraphy at varying angles. These observations suggest that neither the level of neutral buoyancy nor the rigidity contrasts between layers play a role in determining the distribution of sills in the crust. Broadly, sills follow pre-existing structure, but at smaller scales, sills behave drastically different, with little regard to bedding planes.

Effect of Porosity Content of Arc-Sprayed Alloy 625 Skins on the Flexural Behavior of Nickel Foam Core Sandwich Structures

NASA Astrophysics Data System (ADS)

Salavati, S.; Pershin, L.; Coyle, T. W.; Mostaghimi, J.

2015-01-01

Metallic foam core sandwich structures have been of particular interest for engineering applications in recent decades because of their unique mechanical and physical properties. Thermal spraying techniques have been recently introduced as a novel low-cost method for production of these structures with complex shapes. One of the potential applications of the metallic foam core sandwich structures prepared by thermal spray techniques is as heat shield devices. Open porosity in the microstructure of the coating may allow the cooling efficiency of the heat shield to be improved through the film cooling phenomenon. A modified twin wire-arc spraying process was employed to deposit high temperature resistant alloy 625 coatings with a high percentage of the open porosity. The effect of skin porosity on the mechanical properties (flexural rigidity) of the sandwich structures was studied using a four-point bending test. It was concluded from the four-point bending test results that increase in the porosity content of the coatings leads to decrease in the flexural rigidity of the sandwich panels. The ductility of the porous and conventional arc-sprayed alloy 625 coatings was improved after heat treatment at 1100 °C for 3 h.

The Structure of Neurexin 1[alpha] Reveals Features Promoting a Role as Synaptic Organizer

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

Chen, Fang; Venugopal, Vandavasi; Murray, Beverly

{alpha}-Neurexins are essential synaptic adhesion molecules implicated in autism spectrum disorder and schizophrenia. The {alpha}-neurexin extracellular domain consists of six LNS domains interspersed by three EGF-like repeats and interacts with many different proteins in the synaptic cleft. To understand how {alpha}-neurexins might function as synaptic organizers, we solved the structure of the neurexin 1{alpha} extracellular domain (n1{alpha}) to 2.65 {angstrom}. The L-shaped molecule can be divided into a flexible repeat I (LNS1-EGF-A-LNS2), a rigid horseshoe-shaped repeat II (LNS3-EGF-B-LNS4) with structural similarity to so-called reelin repeats, and an extended repeat III (LNS5-EGF-B-LNS6) with controlled flexibility. A 2.95 {angstrom} structure of n1{alpha}more » carrying splice insert SS3 in LNS4 reveals that SS3 protrudes as a loop and does not alter the rigid arrangement of repeat II. The global architecture imposed by conserved structural features enables {alpha}-neurexins to recruit and organize proteins in distinct and variable ways, influenced by splicing, thereby promoting synaptic function.« less

Exoskeletons of Bougainvilliidae and other Hydroidolina (Cnidaria, Hydrozoa): structure and composition

PubMed Central

Marian, José Eduardo A.R.; Migotto, Alvaro Esteves; Marques, Antonio Carlos

2017-01-01

The exoskeleton is an important source of characters for the taxonomy of Hydroidolina. It originates as epidermal secretions and, among other functions, protects the coenosarc of the polypoid stage. However, comparative studies on the exoskeletal tissue origin, development, chemical, and structural characteristics, as well as its evolution and homology, are few and fragmented. This study compares the structure and composition of the exoskeleton and underlying coenosarc in members of “Anthoathecata” and some Leptothecata, but does so mainly in bougainvilliid polyps histological analyses. We also studied the development of the exoskeleton under experimental conditions. We identified three types of glandular epidermal cells related to the origin of the exoskeleton and the secretion of its polysaccharides component. The exoskeleton of the species studied is either bilayered (perisarc and exosarc, especially in bougainvilliids) or corneous (perisarc). The exoskeleton varies in chemical composition, structural rigidity, thickness, extension, and coverage in the different regions of the colony. In bilayered exoskeletons, the exosarc is produced first and appears to be a key step in the formation of the rigid exoskeleton. The exoskeleton contains anchoring structures such as desmocytes and “perisarc extensions.” PMID:28224050

Construction patterns of birds' nests provide insight into nest-building behaviours.

PubMed

Biddle, Lucia; Goodman, Adrian M; Deeming, D Charles

2017-01-01

Previous studies have suggested that birds and mammals select materials needed for nest building based on their thermal or structural properties, although the amounts or properties of the materials used have been recorded for only a very small number of species. Some of the behaviours underlying the construction of nests can be indirectly determined by careful deconstruction of the structure and measurement of the biomechanical properties of the materials used. Here we examined this idea in an investigation of Bullfinch ( Pyrrhula pyrrhula ) nests as a model for open-nesting songbird species that construct a "twig" nest, and tested the hypothesis that materials in different parts of nests serve different functions. The quantities of materials present in the nest base, sides and cup were recorded before structural analysis. Structural analysis showed that the base of the outer nests were composed of significantly thicker, stronger and more rigid materials compared to the side walls, which in turn were significantly thicker, stronger and more rigid than materials used in the cup. These results suggest that the placement of particular materials in nests may not be random, but further work is required to determine if the final structure of a nest accurately reflects the construction process.

Supramolecular structure formation of Langmuir-Blodgett films of comblike precursor and polyimide

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

Goloudina, S. I., E-mail: goloudina@mail.ru; Luchinin, V. V.; Rozanov, V. V.

2013-03-15

The surface structure of Langmuir-Blodgett films of a comblike polyimide precursor-a rigid-chain polyamic acid alkylamine salt bearing multichains of tertiary amine-and films of the corresponding polyimide were studied by atomic force microscopy (AFM). An analysis of the images of the surface of three-layer films revealed a domain structure. It was found that the Langmuir-Blodgett film formation of the precursor occurs as a result of the layer-by-layer deposition of two-dimensional domains (composed of polyamic acid salt molecules on the water surface) onto a substrate. The formation of domains in a monolayer is associated with the chemical structure of the precursor, tomore » be more precise, with the rigidity of the main chain and the presence of closely spaced aliphatic side chains in the polymer chain, whose total cross-section area is close to the surface area of the projection onto the plane of the repeating unit of the main chain. Polyimide films inherit the domain structure of the precursor films; the inhomogeneity of the film thickness substantially decreases, whereas the domain size and character of their distribution in the film remain unchanged.« less

Structure of apo-CAP reveals that large conformational changes are necessary for DNA binding

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

Sharma, Hitesh; Yu, Shaoning; Kong, Jilie

2009-10-21

The binding of cAMP to the Escherichia coli catabolite gene activator protein (CAP) produces a conformational change that enables it to bind specific DNA sequences and regulate transcription, which it cannot do in the absence of the nucleotide. The crystal structures of the unliganded CAP containing a D138L mutation and the unliganded WT CAP were determined at 2.3 and 3.6 {angstrom} resolution, respectively, and reveal that the two DNA binding domains have dimerized into one rigid body and their two DNA recognition helices become buried. The WT structure shows multiple orientations of this rigid body relative to the nucleotide bindingmore » domain supporting earlier biochemical data suggesting that the inactive form exists in an equilibrium among different conformations. Comparison of the structures of the liganded and unliganded CAP suggests that cAMP stabilizes the active DNA binding conformation of CAP through the interactions that the N{sup 6} of the adenosine makes with the C-helices. These interactions are associated with the reorientation and elongation of the C-helices that precludes the formation of the inactive structure.« less

Development and modeling of self-deployable structures

NASA Astrophysics Data System (ADS)

Neogi, Depankar

Deployable space structures are prefabricated structures which can be transformed from a closed, compact configuration to a predetermined expanded form in which they are stable and can bear loads. The present research effort investigates a new family of deployable structures, called the Self-Deployable Structures (SDS). Unlike other deployable structures, which have rigid members, the SDS members are flexible while the connecting joints are rigid. The joints store the predefined geometry of the deployed structure in the collapsed state. The SDS is stress-free in both deployed and collapsed configurations and results in a self-standing structure which acquires its structural properties after a chemical reaction. Reliability of deployment is one of the most important features of the SDS, since it does not rely on mechanisms that can lock during deployment. The unit building block of these structures is the self-deployable structural element (SDSE). Several SDSE members can be linked to generate a complex building block such as a triangular or a tetrahedral structure. Different SDSE and SDS concepts are investigated in the research work, and the performance of SDS's are experimentally and theoretically explored. Triangular and tetrahedral prototype SDS have been developed and presented. Theoretical efforts include modeling the behavior of 2-dimensional SDSs. Using this design tool, engineers can study the effects of different packing configurations and deployment sequence; and perform optimization on the collapsed state of a structure with different external constraints. The model also predicts if any lockup or entanglement occurs during deployment.

Revealing Hidden Conformational Space of LOV Protein VIVID Through Rigid Residue Scan Simulations

NASA Astrophysics Data System (ADS)

Zhou, Hongyu; Zoltowski, Brian D.; Tao, Peng

2017-04-01

VIVID(VVD) protein is a Light-Oxygen-Voltage(LOV) domain in circadian clock system. Upon blue light activation, a covalent bond is formed between VVD residue Cys108 and its cofactor flavin adenine dinucleotide(FAD), and prompts VVD switching from Dark state to Light state with significant conformational deviation. However, the mechanism of this local environment initiated global protein conformational change remains elusive. We employed a recently developed computational approach, rigid residue scan(RRS), to systematically probe the impact of the internal degrees of freedom in each amino acid residue of VVD on its overall dynamics by applying rigid body constraint on each residue in molecular dynamics simulations. Key residues were identified with distinctive impacts on Dark and Light states, respectively. All the simulations display wide range of distribution on a two-dimensional(2D) plot upon structural root-mean-square deviations(RMSD) from either Dark or Light state. Clustering analysis of the 2D RMSD distribution leads to 15 representative structures with drastically different conformation of N-terminus, which is also a key difference between Dark and Light states of VVD. Further principle component analyses(PCA) of RRS simulations agree with the observation of distinctive impact from individual residues on Dark and Light states.

Numerically constructed internal-coordinate Hamiltonian with Eckart embedding and its application for the inversion tunneling of ammonia.

PubMed

Fábri, Csaba; Mátyus, Edit; Császár, Attila G

2014-02-05

It is shown that the use of an Eckart-frame embedding with a kinetic energy operator expressed in curvilinear internal coordinates becomes feasible and straightforward to implement for arbitrary molecular compositions and internal coordinates if the operator is defined numerically over a (discrete variable representation) grid. The algorithm proposed utilizes the transformation method of Dymarsky and Kudin to maintain the rotational Eckart condition. In order to demonstrate the applicability and flexibility of our approach the non-rigid ammonia molecule is considered and the corresponding rotational-vibrational energy levels and wave functions are computed using kinetic energy operators with three different embeddings. Two of them fulfill the Eckart conditions corresponding to a trigonal pyramidal (C3v) and a trigonal planar (D3h) reference structure and the third one is a non-Eckart frame. The computed energy levels are, of course, identical, and the structure of the three different wave-function representations are analyzed in terms of the rigid rotor functions for a symmetric top. The possible advantages of one frame representation over another are discussed concerning the interpretation of the rovibrational states in terms of the traditional rigid rotor labels. Copyright © 2013 Elsevier B.V. All rights reserved.

A 3D, fully Eulerian, VOF-based solver to study the interaction between two fluids and moving rigid bodies using the fictitious domain method

NASA Astrophysics Data System (ADS)

Pathak, Ashish; Raessi, Mehdi

2016-04-01

We present a three-dimensional (3D) and fully Eulerian approach to capturing the interaction between two fluids and moving rigid structures by using the fictitious domain and volume-of-fluid (VOF) methods. The solid bodies can have arbitrarily complex geometry and can pierce the fluid-fluid interface, forming contact lines. The three-phase interfaces are resolved and reconstructed by using a VOF-based methodology. Then, a consistent scheme is employed for transporting mass and momentum, allowing for simulations of three-phase flows of large density ratios. The Eulerian approach significantly simplifies numerical resolution of the kinematics of rigid bodies of complex geometry and with six degrees of freedom. The fluid-structure interaction (FSI) is computed using the fictitious domain method. The methodology was developed in a message passing interface (MPI) parallel framework accelerated with graphics processing units (GPUs). The computationally intensive solution of the pressure Poisson equation is ported to GPUs, while the remaining calculations are performed on CPUs. The performance and accuracy of the methodology are assessed using an array of test cases, focusing individually on the flow solver and the FSI in surface-piercing configurations. Finally, an application of the proposed methodology in simulations of the ocean wave energy converters is presented.

PPI4DOCK: large scale assessment of the use of homology models in free docking over more than 1000 realistic targets.

PubMed

Yu, Jinchao; Guerois, Raphaël

2016-12-15

Protein-protein docking methods are of great importance for understanding interactomes at the structural level. It has become increasingly appealing to use not only experimental structures but also homology models of unbound subunits as input for docking simulations. So far we are missing a large scale assessment of the success of rigid-body free docking methods on homology models. We explored how we could benefit from comparative modelling of unbound subunits to expand docking benchmark datasets. Starting from a collection of 3157 non-redundant, high X-ray resolution heterodimers, we developed the PPI4DOCK benchmark containing 1417 docking targets based on unbound homology models. Rigid-body docking by Zdock showed that for 1208 cases (85.2%), at least one correct decoy was generated, emphasizing the efficiency of rigid-body docking in generating correct assemblies. Overall, the PPI4DOCK benchmark contains a large set of realistic cases and provides new ground for assessing docking and scoring methodologies. Benchmark sets can be downloaded from http://biodev.cea.fr/interevol/ppi4dock/ CONTACT: guerois@cea.frSupplementary information: Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Consequences of Optimal Bond Valence on Structural Rigidity and Improved Luminescence Properties in Sr xBa 2-xSiO 4:Eu 2+ Orthosilicate Phosphors

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

Denault, Kristin A.; Brgoch, Jakoah; Gaultois, Michael W.

The orthosilicate phosphors Sr xBa 2–xSiO 4:Eu 2+ have now been known for over four decades and have found extensive recent use in solid-state white lighting. It is well-recognized in the literature and in practice that intermediate compositions in the solid-solutions between the orthosilicates Sr 2SiO 4 and Ba 2SiO 4 yield the best phosphor hosts when the thermal stability of luminescence is considered. We employ a combination of synchrotron X-ray diffraction, total scattering measurements, density functional theory calculations, and low-temperature heat capacity measurements, in conjunction with detailed temperature- and time-resolved studies of luminescence properties to understand the origins ofmore » the improved luminescence properties. We observe that in the intermediate compositions, the two cation sites in the crystal structure are optimally bonded as determined from bond valence sum calculations. Optimal bonding results in a more rigid lattice, as established by the intermediate compositions possessing the highest Debye temperature, which are determined experimentally from low-temperature heat capacity measurements. Greater rigidity in turn results in the highest luminescence efficiency for intermediate compositions at elevated temperatures.« less

Revealing Hidden Conformational Space of LOV Protein VIVID Through Rigid Residue Scan Simulations

PubMed Central

Zhou, Hongyu; Zoltowski, Brian D.; Tao, Peng

2017-01-01

VIVID(VVD) protein is a Light-Oxygen-Voltage(LOV) domain in circadian clock system. Upon blue light activation, a covalent bond is formed between VVD residue Cys108 and its cofactor flavin adenine dinucleotide(FAD), and prompts VVD switching from Dark state to Light state with significant conformational deviation. However, the mechanism of this local environment initiated global protein conformational change remains elusive. We employed a recently developed computational approach, rigid residue scan(RRS), to systematically probe the impact of the internal degrees of freedom in each amino acid residue of VVD on its overall dynamics by applying rigid body constraint on each residue in molecular dynamics simulations. Key residues were identified with distinctive impacts on Dark and Light states, respectively. All the simulations display wide range of distribution on a two-dimensional(2D) plot upon structural root-mean-square deviations(RMSD) from either Dark or Light state. Clustering analysis of the 2D RMSD distribution leads to 15 representative structures with drastically different conformation of N-terminus, which is also a key difference between Dark and Light states of VVD. Further principle component analyses(PCA) of RRS simulations agree with the observation of distinctive impact from individual residues on Dark and Light states. PMID:28425502

Automatic identification of mobile and rigid substructures in molecular dynamics simulations and fractional structural fluctuation analysis.

PubMed

Martínez, Leandro

2015-01-01

The analysis of structural mobility in molecular dynamics plays a key role in data interpretation, particularly in the simulation of biomolecules. The most common mobility measures computed from simulations are the Root Mean Square Deviation (RMSD) and Root Mean Square Fluctuations (RMSF) of the structures. These are computed after the alignment of atomic coordinates in each trajectory step to a reference structure. This rigid-body alignment is not robust, in the sense that if a small portion of the structure is highly mobile, the RMSD and RMSF increase for all atoms, resulting possibly in poor quantification of the structural fluctuations and, often, to overlooking important fluctuations associated to biological function. The motivation of this work is to provide a robust measure of structural mobility that is practical, and easy to interpret. We propose a Low-Order-Value-Optimization (LOVO) strategy for the robust alignment of the least mobile substructures in a simulation. These substructures are automatically identified by the method. The algorithm consists of the iterative superposition of the fraction of structure displaying the smallest displacements. Therefore, the least mobile substructures are identified, providing a clearer picture of the overall structural fluctuations. Examples are given to illustrate the interpretative advantages of this strategy. The software for performing the alignments was named MDLovoFit and it is available as free-software at: http://leandro.iqm.unicamp.br/mdlovofit.

Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading

PubMed Central

Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre

2016-01-01

Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted. PMID:28773522

Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading.

PubMed

Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre

2016-05-21

Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted.

Automatic Identification of Mobile and Rigid Substructures in Molecular Dynamics Simulations and Fractional Structural Fluctuation Analysis

PubMed Central

Martínez, Leandro

2015-01-01

The analysis of structural mobility in molecular dynamics plays a key role in data interpretation, particularly in the simulation of biomolecules. The most common mobility measures computed from simulations are the Root Mean Square Deviation (RMSD) and Root Mean Square Fluctuations (RMSF) of the structures. These are computed after the alignment of atomic coordinates in each trajectory step to a reference structure. This rigid-body alignment is not robust, in the sense that if a small portion of the structure is highly mobile, the RMSD and RMSF increase for all atoms, resulting possibly in poor quantification of the structural fluctuations and, often, to overlooking important fluctuations associated to biological function. The motivation of this work is to provide a robust measure of structural mobility that is practical, and easy to interpret. We propose a Low-Order-Value-Optimization (LOVO) strategy for the robust alignment of the least mobile substructures in a simulation. These substructures are automatically identified by the method. The algorithm consists of the iterative superposition of the fraction of structure displaying the smallest displacements. Therefore, the least mobile substructures are identified, providing a clearer picture of the overall structural fluctuations. Examples are given to illustrate the interpretative advantages of this strategy. The software for performing the alignments was named MDLovoFit and it is available as free-software at: http://leandro.iqm.unicamp.br/mdlovofit PMID:25816325

49 CFR 238.123 - Emergency roof access.

Code of Federal Regulations, 2010 CFR

2010-10-01

... be free of any rigid secondary structure (e.g., a diffuser or diffuser support, lighting back fixture... a hatch, it shall be possible to push interior panels or liners out of their retention devices and...

Typewriting--Less-Than-a-Semester Credit Basis

ERIC Educational Resources Information Center

Schramm, Dwayne

1974-01-01

Five advantages to be gained in teaching typing in a time structure less rigid than the traditional semester are itemized. The implications for typewriting teachers as a more individualized approach is used are considered. (AG)

I've Been Stung: What Should I Do?

MedlinePlus

... personnel at an annual convention of the Diving Equipment and Marketing Association that was held in Anaheim, ... which is easily torn from the rigid (abrasive) structure underneath, and thus deposited into the scrape or ...

Multi-Storey Air-Supported Building Construction

ERIC Educational Resources Information Center

Pohl, J. G.; Cowan, H. J.

1972-01-01

Multistory buildings, supported by internal air pressure and surrounded by a thin, flexible or rigid membrane acting both as structural container and external cladding, are feasible and highly economical for a number of building applications. (Author)

Ensemble-based evaluation for protein structure models.

PubMed

Jamroz, Michal; Kolinski, Andrzej; Kihara, Daisuke

2016-06-15

Comparing protein tertiary structures is a fundamental procedure in structural biology and protein bioinformatics. Structure comparison is important particularly for evaluating computational protein structure models. Most of the model structure evaluation methods perform rigid body superimposition of a structure model to its crystal structure and measure the difference of the corresponding residue or atom positions between them. However, these methods neglect intrinsic flexibility of proteins by treating the native structure as a rigid molecule. Because different parts of proteins have different levels of flexibility, for example, exposed loop regions are usually more flexible than the core region of a protein structure, disagreement of a model to the native needs to be evaluated differently depending on the flexibility of residues in a protein. We propose a score named FlexScore for comparing protein structures that consider flexibility of each residue in the native state of proteins. Flexibility information may be extracted from experiments such as NMR or molecular dynamics simulation. FlexScore considers an ensemble of conformations of a protein described as a multivariate Gaussian distribution of atomic displacements and compares a query computational model with the ensemble. We compare FlexScore with other commonly used structure similarity scores over various examples. FlexScore agrees with experts' intuitive assessment of computational models and provides information of practical usefulness of models. https://bitbucket.org/mjamroz/flexscore dkihara@purdue.edu Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

Ensemble-based evaluation for protein structure models

PubMed Central

Jamroz, Michal; Kolinski, Andrzej; Kihara, Daisuke

2016-01-01

Motivation: Comparing protein tertiary structures is a fundamental procedure in structural biology and protein bioinformatics. Structure comparison is important particularly for evaluating computational protein structure models. Most of the model structure evaluation methods perform rigid body superimposition of a structure model to its crystal structure and measure the difference of the corresponding residue or atom positions between them. However, these methods neglect intrinsic flexibility of proteins by treating the native structure as a rigid molecule. Because different parts of proteins have different levels of flexibility, for example, exposed loop regions are usually more flexible than the core region of a protein structure, disagreement of a model to the native needs to be evaluated differently depending on the flexibility of residues in a protein. Results: We propose a score named FlexScore for comparing protein structures that consider flexibility of each residue in the native state of proteins. Flexibility information may be extracted from experiments such as NMR or molecular dynamics simulation. FlexScore considers an ensemble of conformations of a protein described as a multivariate Gaussian distribution of atomic displacements and compares a query computational model with the ensemble. We compare FlexScore with other commonly used structure similarity scores over various examples. FlexScore agrees with experts’ intuitive assessment of computational models and provides information of practical usefulness of models. Availability and implementation: https://bitbucket.org/mjamroz/flexscore Contact: dkihara@purdue.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27307633

FUEL ELEMENT FOR A NUCLEAR REACTOR

DOEpatents

Davidson, J.K.

1963-11-19

A fuel element structure particularly useful in high temperature nuclear reactors is presented. Basically, the structure comprises two coaxial graphite sleeves integrally joined together by radial fins. Due to the high structural strength of graphite at high temperatures and the rigidity of this structure, nuclear fuel encased within the inner sleeve in contiguous relation therewith is supported and prevented from expanding radially at high temperatures. Thus, the necessity of relying on the usual cladding materials with relatively low temperature limitations for structural strength is removed. (AEC)

Structure of flexible and semiflexible polyelectrolyte chains in confined spaces of slit micro/nanochannels.

PubMed

Jeon, Jonggu; Chun, Myung-Suk

2007-04-21

Understanding the behavior of a polyelectrolyte in confined spaces has direct relevance in design and manipulation of microfluidic devices, as well as transport in living organisms. In this paper, a coarse-grained model of anionic semiflexible polyelectrolyte is applied, and its structure and dynamics are fully examined with Brownian dynamics (BD) simulations both in bulk solution and under confinement between two negatively charged parallel plates. The modeling is based on the nonlinear bead-spring discretization of a continuous chain with additional long-range electrostatic, Lennard-Jones, and hydrodynamic interactions between pairs of beads. The authors also consider the steric and electrostatic interactions between the bead and the confining wall. Relevant model parameters are determined from experimental rheology data on the anionic polysaccharide xanthan reported previously. For comparison, both flexible and semiflexible models are developed accompanying zero and finite intrinsic persistence lengths, respectively. The conformational changes of the polyelectrolyte chain induced by confinements and their dependence on the screening effect of the electrolyte solution are faithfully characterized with BD simulations. Depending on the intrinsic rigidity and the medium ionic strength, the polyelectrolyte can be classified as flexible, semiflexible, or rigid. Confined flexible and semiflexible chains exhibit a nonmonotonic variation in size, as measured by the radius of gyration and end-to-end distance, with changing slit width. For the semiflexible chain, this is coupled to the variations in long-range bond vector correlation. The rigid chain, realized at low ionic strength, does not have minima in size but exhibits a sigmoidal transition. The size of confined semiflexible and rigid polyelectrolytes can be well described by the wormlike chain model once the electrostatic effects are taken into account by the persistence length measured at long length scale.

Fluid-Structure Interactions with Flexible and Rigid Bodies

NASA Astrophysics Data System (ADS)

Daily, David Jesse

Fluid structure interactions occur to some extent in nearly every type of fluid flow. Understanding how structures interact with fluids and visa-versa is of vital importance in many engineering applications. The purpose of this research is to explore how fluids interact with flexible and rigid structures. A computational model was used to model the fluid structure interactions of vibrating synthetic vocal folds. The model simulated the coupling of the fluid and solid domains using a fluid-structure interface boundary condition. The fluid domain used a slightly compressible flow solver to allow for the possibility of acoustic coupling with the subglottal geometry and vibration of the vocal fold model. As the subglottis lengthened, the frequency of vibration decreased until a new acoustic mode could form in the subglottis. Synthetic aperture particle image velocimetry (SAPIV) is a three-dimensional particle tracking technique. SAPIV was used to image the jet of air that emerges from vibrating human vocal folds (glottal jet) during phonation. The three-dimensional reconstruction of the glottal jet found faint evidence of flow characteristics seen in previous research, such as axis-switching, but did not have sufficient resolution to detect small features. SAPIV was further applied to reconstruct the smaller flow characteristics of the glottal jet of vibrating synthetic vocal folds. Two- and four-layer synthetic vocal fold models were used to determine how the glottal jet from the synthetic models compared to the glottal jet from excised human vocal folds. The two- and four-layer models clearly exhibited axis-switching which has been seen in other 3D analyses of the glottal jet. Cavitation in a quiescent fluid can break a rigid structure such as a glass bottle. A new cavitation number was derived to include acceleration and pressure head at cavitation onset. A cavitation stick was used to validate the cavitation number by filling it with different depths and hitting the stick to cause fluid cavitation. Acceleration was measured using an accelerometer and cavitation bubbles were detected using a high-speed camera. Cavitation in an accelerating fluid occurred at a cavitation number of 1. Keywords: Fluid structure interaction, vocal folds, acoustics, SAPIV, cavitation, slightly compressible

Learning in Structured Connectionist Networks

DTIC Science & Technology

1988-04-01

the structure is too rigid and learning too difficult for cognitive modeling. Two algorithms for learning simple, feature-based concept descriptions...and learning too difficult for cognitive model- ing. Two algorithms for learning simple, feature-based concept descriptions were also implemented. The...Term Goals Recent progress in connectionist research has been encouraging; networks have success- fully modeled human performance for various cognitive

Vascularization of the trachea in the bottlenose dolphin: comparison with bovine and evidence for evolutionary adaptations to diving

NASA Astrophysics Data System (ADS)

Ballarin, Cristina; Bagnoli, Paola; Peruffo, Antonella; Cozzi, Bruno

2018-04-01

The rigid structure of the mammalian trachea is functional to maintain constant patency and airflow during breathing, but no gas exchange takes place through its walls. The structure of the organ in dolphins shows increased rigidity of the tracheal cartilaginous rings and the presence of vascular lacunae in the submucosa. However, no actual comparison was ever made between the size and capacity of the vascular lacunae of the dolphin trachea and the potentially homologous structures of terrestrial mammals. In the present study, the extension of the lacunae has been compared between the bottlenose dolphin and the bovine, a closely related terrestrial Cetartiodactyla. Our results indicate that the extension of the blood spaces in the submucosa of dolphins is over 12 times larger than in the corresponding structure of the bovines. Furthermore, a microscopic analysis revealed the presence of valve-like structures in the walls of the cetacean lacunae. The huge difference in size suggests that the lacunae are not merely a product of individual physiological plasticity, but may constitute a true adaptive evolutionary character, functional to life in the aquatic environment. The presence of valve-like structures may be related to the regulation of blood flow, and curtail excessive compression under baric stress at depth.

Comparative Analysis of the Reliability of Steel Structure with Pinned and Rigid Nodes Subjected to Fire

NASA Astrophysics Data System (ADS)

Kubicka, Katarzyna; Radoń, Urszula; Szaniec, Waldemar; Pawlak, Urszula

2017-10-01

The paper concerns the reliability analysis of steel structures subjected to high temperatures of fire gases. Two types of spatial structures were analysed, namely with pinned and rigid nodes. The fire analysis was carried out according to prescriptions of Eurocode. The static-strength analysis was conducted using the finite element method (FEM). The MES3D program, developed by Szaniec (Kielce University of Technology, Poland), was used for this purpose. The results received from MES3D made it possible to carry out the reliability analysis using the Numpress Explore program that was developed at the Institute of Fundamental Technological Research of the Polish Academy of Sciences [9]. The measurement of reliability of structures is the Hasofer-Lind reliability index (β). The reliability analysis was carried out according to approximation (FORM, SORM) and simulation (Importance Sampling, Monte Carlo) methods. As the fire progresses, the value of reliability index decreases. The analysis conducted for the study made it possible to evaluate the impact of node types on those changes. In real structures, it is often difficult to define correctly types of nodes, so some simplifications are made. The presented analysis contributes to the recognition of consequences of such assumptions for the safety of structures, subjected to fire.

Hierarchical Nanostructures Self-Assembled from a Mixture System Containing Rod-Coil Block Copolymers and Rigid Homopolymers

PubMed Central

Li, Yongliang; Jiang, Tao; Lin, Shaoliang; Lin, Jiaping; Cai, Chunhua; Zhu, Xingyu

2015-01-01

Self-assembly behavior of a mixture system containing rod-coil block copolymers and rigid homopolymers was investigated by using Brownian dynamics simulations. The morphologies of formed hierarchical self-assemblies were found to be dependent on the Lennard-Jones (LJ) interaction εRR between rod blocks, lengths of rod and coil blocks in copolymer, and mixture ratio of block copolymers to homopolymers. As the εRR value decreases, the self-assembled structures of mixtures are transformed from an abacus-like structure to a helical structure, to a plain fiber, and finally are broken into unimers. The order parameter of rod blocks was calculated to confirm the structure transition. Through varying the length of rod and coil blocks, the regions of thermodynamic stability of abacus, helix, plain fiber, and unimers were mapped. Moreover, it was discovered that two levels of rod block ordering exist in the helices. The block copolymers are helically wrapped on the homopolymer bundles to form helical string, while the rod blocks are twistingly packed inside the string. In addition, the simulation results are in good agreement with experimental observations. The present work reveals the mechanism behind the formation of helical (experimentally super-helical) structures and may provide useful information for design and preparation of the complex structures. PMID:25965726

Fast and anisotropic flexibility-rigidity index for protein flexibility and fluctuation analysis

NASA Astrophysics Data System (ADS)

Opron, Kristopher; Xia, Kelin; Wei, Guo-Wei

2014-06-01

Protein structural fluctuation, typically measured by Debye-Waller factors, or B-factors, is a manifestation of protein flexibility, which strongly correlates to protein function. The flexibility-rigidity index (FRI) is a newly proposed method for the construction of atomic rigidity functions required in the theory of continuum elasticity with atomic rigidity, which is a new multiscale formalism for describing excessively large biomolecular systems. The FRI method analyzes protein rigidity and flexibility and is capable of predicting protein B-factors without resorting to matrix diagonalization. A fundamental assumption used in the FRI is that protein structures are uniquely determined by various internal and external interactions, while the protein functions, such as stability and flexibility, are solely determined by the structure. As such, one can predict protein flexibility without resorting to the protein interaction Hamiltonian. Consequently, bypassing the matrix diagonalization, the original FRI has a computational complexity of O(N^2). This work introduces a fast FRI (fFRI) algorithm for the flexibility analysis of large macromolecules. The proposed fFRI further reduces the computational complexity to O(N). Additionally, we propose anisotropic FRI (aFRI) algorithms for the analysis of protein collective dynamics. The aFRI algorithms permit adaptive Hessian matrices, from a completely global 3N × 3N matrix to completely local 3 × 3 matrices. These 3 × 3 matrices, despite being calculated locally, also contain non-local correlation information. Eigenvectors obtained from the proposed aFRI algorithms are able to demonstrate collective motions. Moreover, we investigate the performance of FRI by employing four families of radial basis correlation functions. Both parameter optimized and parameter-free FRI methods are explored. Furthermore, we compare the accuracy and efficiency of FRI with some established approaches to flexibility analysis, namely, normal mode analysis and Gaussian network model (GNM). The accuracy of the FRI method is tested using four sets of proteins, three sets of relatively small-, medium-, and large-sized structures and an extended set of 365 proteins. A fifth set of proteins is used to compare the efficiency of the FRI, fFRI, aFRI, and GNM methods. Intensive validation and comparison indicate that the FRI, particularly the fFRI, is orders of magnitude more efficient and about 10% more accurate overall than some of the most popular methods in the field. The proposed fFRI is able to predict B-factors for α-carbons of the HIV virus capsid (313 236 residues) in less than 30 seconds on a single processor using only one core. Finally, we demonstrate the application of FRI and aFRI to protein domain analysis.

Fast and anisotropic flexibility-rigidity index for protein flexibility and fluctuation analysis

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

Opron, Kristopher; Xia, Kelin; Wei, Guo-Wei, E-mail: wei@math.msu.edu

Protein structural fluctuation, typically measured by Debye-Waller factors, or B-factors, is a manifestation of protein flexibility, which strongly correlates to protein function. The flexibility-rigidity index (FRI) is a newly proposed method for the construction of atomic rigidity functions required in the theory of continuum elasticity with atomic rigidity, which is a new multiscale formalism for describing excessively large biomolecular systems. The FRI method analyzes protein rigidity and flexibility and is capable of predicting protein B-factors without resorting to matrix diagonalization. A fundamental assumption used in the FRI is that protein structures are uniquely determined by various internal and external interactions,more » while the protein functions, such as stability and flexibility, are solely determined by the structure. As such, one can predict protein flexibility without resorting to the protein interaction Hamiltonian. Consequently, bypassing the matrix diagonalization, the original FRI has a computational complexity of O(N{sup 2}). This work introduces a fast FRI (fFRI) algorithm for the flexibility analysis of large macromolecules. The proposed fFRI further reduces the computational complexity to O(N). Additionally, we propose anisotropic FRI (aFRI) algorithms for the analysis of protein collective dynamics. The aFRI algorithms permit adaptive Hessian matrices, from a completely global 3N × 3N matrix to completely local 3 × 3 matrices. These 3 × 3 matrices, despite being calculated locally, also contain non-local correlation information. Eigenvectors obtained from the proposed aFRI algorithms are able to demonstrate collective motions. Moreover, we investigate the performance of FRI by employing four families of radial basis correlation functions. Both parameter optimized and parameter-free FRI methods are explored. Furthermore, we compare the accuracy and efficiency of FRI with some established approaches to flexibility analysis, namely, normal mode analysis and Gaussian network model (GNM). The accuracy of the FRI method is tested using four sets of proteins, three sets of relatively small-, medium-, and large-sized structures and an extended set of 365 proteins. A fifth set of proteins is used to compare the efficiency of the FRI, fFRI, aFRI, and GNM methods. Intensive validation and comparison indicate that the FRI, particularly the fFRI, is orders of magnitude more efficient and about 10% more accurate overall than some of the most popular methods in the field. The proposed fFRI is able to predict B-factors for α-carbons of the HIV virus capsid (313 236 residues) in less than 30 seconds on a single processor using only one core. Finally, we demonstrate the application of FRI and aFRI to protein domain analysis.« less

Analysis of Cracking in Jointed Plain Concrete Pavements

DOT National Transportation Integrated Search

2017-03-01

This paper investigates the trends of longitudinal and transverse cracking in jointed concrete pavements based on Long-Term Pavement Performance (LTPP) Program Strategic Study of Structural Factors for Rigid Pavements (SPS-2) data. The impacts of sla...

Bolt installation tool for tightening large nuts and bolts

NASA Technical Reports Server (NTRS)

Mcdougal, A. R.; Norman, R. M.

1974-01-01

Large bolts and nuts are accurately tightened to structures without damaging torque stresses. There are two models of bolt installation tool. One is rigidly mounted and one is hand held. Each model includes torque-multiplier unit.

Highly cross-linked nanoporous polymers

DOEpatents

Steckle, Jr., Warren P.; Apen, Paul G.; Mitchell, Michael A.

1998-01-01

Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes.

Highly cross-linked nanoporous polymers

DOEpatents

Steckle, Jr., Warren P.; Apen, Paul G.; Mitchell, Michael A.

1997-01-01

Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes.

49 CFR 587.19 - Mounting.

Code of Federal Regulations, 2010 CFR

2010-10-01

... structure attached thereto. The front of the fixed rigid barrier to which the deformable face is attached is... ground. These bolts are at least 8 mm (0.3 in) in diameter. Steel clamping strips are used for both the...

49 CFR 587.19 - Mounting.

Code of Federal Regulations, 2014 CFR

2014-10-01

... structure attached thereto. The front of the fixed rigid barrier to which the deformable face is attached is... ground. These bolts are at least 8 mm (0.3 in) in diameter. Steel clamping strips are used for both the...

49 CFR 587.19 - Mounting.

Code of Federal Regulations, 2013 CFR

2013-10-01

... structure attached thereto. The front of the fixed rigid barrier to which the deformable face is attached is... ground. These bolts are at least 8 mm (0.3 in) in diameter. Steel clamping strips are used for both the...

49 CFR 587.19 - Mounting.

Code of Federal Regulations, 2011 CFR

2011-10-01

... structure attached thereto. The front of the fixed rigid barrier to which the deformable face is attached is... ground. These bolts are at least 8 mm (0.3 in) in diameter. Steel clamping strips are used for both the...

49 CFR 587.19 - Mounting.

Code of Federal Regulations, 2012 CFR

2012-10-01

... structure attached thereto. The front of the fixed rigid barrier to which the deformable face is attached is... ground. These bolts are at least 8 mm (0.3 in) in diameter. Steel clamping strips are used for both the...

Vibration control by limiting the maximum axial forces in space trusses

NASA Technical Reports Server (NTRS)

Chawla, Vikas; Utku, Senol; Wada, Ben K.

1993-01-01

Proposed here is a method of vibration control based on limiting the maximum axial forces in the active members of an adaptive truss. The actuators simulate elastic rigid-plastic behavior and consume the vibrational energy as work. The method is applicable to both statically determinate as well as indeterminate truss structures. However, for energy efficient control of statistically indeterminate trusses extra actuators may be provided on the redundant bars. An energy formulation relating the various control parameters is derived to get an estimate of the control time. Since the simulation of elastic rigid-plastic behavior requires a piecewise linear control law, a general analytical solution is not possible. Numerical simulation by step-by-step integration is performed to simulate the control of an example truss structure. The problems of application to statically indeterminate trusses and optimal actuator placement are identified for future work.

Impact of scaffold rigidity on the design and evolution of an artificial Diels-Alderase

PubMed Central

Preiswerk, Nathalie; Beck, Tobias; Schulz, Jessica D.; Milovník, Peter; Mayer, Clemens; Siegel, Justin B.; Baker, David; Hilvert, Donald

2014-01-01

By combining targeted mutagenesis, computational refinement, and directed evolution, a modestly active, computationally designed Diels-Alderase was converted into the most proficient biocatalyst for [4+2] cycloadditions known. The high stereoselectivity and minimal product inhibition of the evolved enzyme enabled preparative scale synthesis of a single product diastereomer. X-ray crystallography of the enzyme–product complex shows that the molecular changes introduced over the course of optimization, including addition of a lid structure, gradually reshaped the pocket for more effective substrate preorganization and transition state stabilization. The good overall agreement between the experimental structure and the original design model with respect to the orientations of both the bound product and the catalytic side chains contrasts with other computationally designed enzymes. Because design accuracy appears to correlate with scaffold rigidity, improved control over backbone conformation will likely be the key to future efforts to design more efficient enzymes for diverse chemical reactions. PMID:24847076

Glass transition temperature of polymer nano-composites with polymer and filler interactions

NASA Astrophysics Data System (ADS)

Hagita, Katsumi; Takano, Hiroshi; Doi, Masao; Morita, Hiroshi

2012-02-01

We systematically studied versatile coarse-grained model (bead spring model) to describe filled polymer nano-composites for coarse-grained (Kremer-Grest model) molecular dynamics simulations. This model consists of long polymers, crosslink, and fillers. We used the hollow structure as the filler to describe rigid spherical fillers with small computing costs. Our filler model consists of surface particles of icosahedra fullerene structure C320 and a repulsive force from the center of the filler is applied to the surface particles in order to make a sphere and rigid. The filler's diameter is 12 times of beads of the polymers. As the first test of our model, we study temperature dependence of volumes of periodic boundary conditions under constant pressures through NPT constant Andersen algorithm. It is found that Glass transition temperature (Tg) decrease with increasing filler's volume fraction for the case of repulsive interaction between polymer and fillers and Tg weakly increase for attractive interaction.

Through-Space Ultrafast Photoinduced Electron Transfer Dynamics of a C 70 -Encapsulated Bisporphyrin Covalent Organic Polyhedron in a Low-Dielectric Medium

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

Ortiz, Michael; Cho, Sung; Niklas, Jens

Ultrafast photoinduced electron transfer (PIET) dynamics of a C 70-encapsulated bisporphyrin covalent organic polyhedron hybrid (C 70@COP-5) is studied in a nonpolar toluene medium with fluorescence and transient absorption spectroscopies. This structurally rigid donor (D)-acceptor (A) molecular hybrid offers a new platform featuring conformationally predetermined cofacial D-A orientation with a fixed edge-to-edge separation, R EE (2.8 Å), without the aid of covalent bonds. Sub-picosecond PIET (T ET ≤ 0.4 ps) and very slow charge recombination (T CR ≈ 600 ps) dynamics are observed. The origin of these dynamics is discussed in terms of enhanced D-A coupling (V = 675 cmmore » -1) and extremely small reorganization energy (λ ≈ 0.18 eV), induced by the intrinsic structural rigidity of the C 70@COP-5 complex.« less

Synthesis, Structure, and Rigid Unit Mode-like Anisotropic Thermal Expansion of BaIr 2 In 9

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

Calta, Nicholas P.; Han, Fei; Kanatzidis, Mercouri G.

2015-09-08

This Article reports the synthesis of large single crystals of BaIr 2In 9 using In flux and their characterization by variable-temperature single-crystal and synchrotron powder X-ray diffraction, resistivity, and magnetization measurements. The title compound adopts the BaFe 2Al 9-type structure in the space group P6/mmm with room temperature unit cell parameters a = 8.8548(6) angstrom and c = 4.2696(4) A. BaIr 2In 9 exhibits anisotropic thermal expansion behavior with linear expansion along the c axis more than 3 times larger than expansion in the ab plane between 90 and 400 K. This anisotropic expansion originates from a rigid unit mode-likemore » mechanism similar to the mechanism of zero and negative thermal expansion observed in many anomalous thermal expansion materials such as ZrW 2O 8 and ScF 3.« less

Synthesis, Structure, and Rigid Unit Mode-like Anisotropic Thermal Expansion of BaIr2In9.

PubMed

Calta, Nicholas P; Han, Fei; Kanatzidis, Mercouri G

2015-09-08

This Article reports the synthesis of large single crystals of BaIr2In9 using In flux and their characterization by variable-temperature single-crystal and synchrotron powder X-ray diffraction, resistivity, and magnetization measurements. The title compound adopts the BaFe2Al9-type structure in the space group P6/mmm with room temperature unit cell parameters a = 8.8548(6) Å and c = 4.2696(4) Å. BaIr2In9 exhibits anisotropic thermal expansion behavior with linear expansion along the c axis more than 3 times larger than expansion in the ab plane between 90 and 400 K. This anisotropic expansion originates from a rigid unit mode-like mechanism similar to the mechanism of zero and negative thermal expansion observed in many anomalous thermal expansion materials such as ZrW2O8 and ScF3.

Initial '80s Development of Inflated Antennas

NASA Technical Reports Server (NTRS)

Friese, G. J.; Bilyeu, G. D.; Thomas, M.

1983-01-01

State of the art technology was considered in the definition and documentation of a membrane surface suitable for use in a space reflector system for long durations in orbit. Requirements for a metal foil-plastic laminate structural element were determined and a laboratory model of a rigidized element to test for strength characteristics was constructed. Characteristics of antennas ranging from 10 meters to 1000 meters were determined. The basic antenna configuration studied consists of (1) a thin film reflector, (2) a thin film cone, (3) a self-rigidizing structural torus at the interface of the cone and reflector; and (4) an inflation system. The reflector is metallized and, when inflated, has a parabolic shape. The cone not only completes the enclosure of the inflatant, but also holds the antenna feed at its apex. The torus keeps the inflated cone-reflector from collapsing inward. Laser test equipment determined the accuracy of the inflated paraboloids.

Trans-pent-2-ene. Electron diffraction, vibrational analysis and molecular mechanics

NASA Astrophysics Data System (ADS)

Ter Brake, J. H. M.; Mijlhoff, F. C.

1981-12-01

The molecular structure of trans-pent-2-ene has been investigated, using electron diffraction, vibrational analysis and molecular mechanics. It is possible to Fit a model, describing trans-pent-2-ene as a semi-rigid molecule with one conformer only, to the electron diffraction data. However, molecular mechanics shows that trans-pent-2-ene is not a semi-rigid molecule. The large-amplitude motion is described, using all pseudo-conformers at 10° intervals around the circle of rotation. The resulting rα structure is: r[-C-C] = 148.4(1), r[-CC-] = 133.4(2), r[-C-C-] = 157.6(5), r[C-H] = 108.2(1)pm; ∠[-C-CC-] = 125.4(3), ∠[C-C-C-] = 115.6(6), ∠[-C-C-H] = 12.7(6), ∠[-CC-H] = 129(2)°. Standard deviations given in parentheses refer to the last significant digit.

Through-Space Ultrafast Photoinduced Electron Transfer Dynamics of a C 70 -Encapsulated Bisporphyrin Covalent Organic Polyhedron in a Low-Dielectric Medium

DOE PAGES

Ortiz, Michael; Cho, Sung; Niklas, Jens; ...

2017-03-13

Ultrafast photoinduced electron transfer (PIET) dynamics of a C 70-encapsulated bisporphyrin covalent organic polyhedron hybrid (C 70@COP-5) is studied in a nonpolar toluene medium with fluorescence and transient absorption spectroscopies. This structurally rigid donor (D)-acceptor (A) molecular hybrid offers a new platform featuring conformationally predetermined cofacial D-A orientation with a fixed edge-to-edge separation, R EE (2.8 Å), without the aid of covalent bonds. Sub-picosecond PIET (T ET ≤ 0.4 ps) and very slow charge recombination (T CR ≈ 600 ps) dynamics are observed. The origin of these dynamics is discussed in terms of enhanced D-A coupling (V = 675 cmmore » -1) and extremely small reorganization energy (λ ≈ 0.18 eV), induced by the intrinsic structural rigidity of the C 70@COP-5 complex.« less

Biophysical model of bacterial cell interactions with nanopatterned cicada wing surfaces.

PubMed

Pogodin, Sergey; Hasan, Jafar; Baulin, Vladimir A; Webb, Hayden K; Truong, Vi Khanh; Phong Nguyen, The Hong; Boshkovikj, Veselin; Fluke, Christopher J; Watson, Gregory S; Watson, Jolanta A; Crawford, Russell J; Ivanova, Elena P

2013-02-19

The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on their physical surface structure. The wings provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. We propose a biophysical model of the interactions between bacterial cells and cicada wing surface structures, and show that mechanical properties, in particular cell rigidity, are key factors in determining bacterial resistance/sensitivity to the bactericidal nature of the wing surface. We confirmed this experimentally by decreasing the rigidity of surface-resistant strains through microwave irradiation of the cells, which renders them susceptible to the wing effects. Our findings demonstrate the potential benefits of incorporating cicada wing nanopatterns into the design of antibacterial nanomaterials. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Quantification of regenerative potential in primary human mammary epithelial cells

PubMed Central

Linnemann, Jelena R.; Miura, Haruko; Meixner, Lisa K.; Irmler, Martin; Kloos, Uwe J.; Hirschi, Benjamin; Bartsch, Harald S.; Sass, Steffen; Beckers, Johannes; Theis, Fabian J.; Gabka, Christian; Sotlar, Karl; Scheel, Christina H.

2015-01-01

We present an organoid regeneration assay in which freshly isolated human mammary epithelial cells are cultured in adherent or floating collagen gels, corresponding to a rigid or compliant matrix environment. In both conditions, luminal progenitors form spheres, whereas basal cells generate branched ductal structures. In compliant but not rigid collagen gels, branching ducts form alveoli at their tips, express basal and luminal markers at correct positions, and display contractility, which is required for alveologenesis. Thereby, branched structures generated in compliant collagen gels resemble terminal ductal-lobular units (TDLUs), the functional units of the mammary gland. Using the membrane metallo-endopeptidase CD10 as a surface marker enriches for TDLU formation and reveals the presence of stromal cells within the CD49fhi/EpCAM− population. In summary, we describe a defined in vitro assay system to quantify cells with regenerative potential and systematically investigate their interaction with the physical environment at distinct steps of morphogenesis. PMID:26071498

Through-Space Ultrafast Photoinduced Electron Transfer Dynamics of a C70-Encapsulated Bisporphyrin Covalent Organic Polyhedron in a Low-Dielectric Medium.

PubMed

Ortiz, Michael; Cho, Sung; Niklas, Jens; Kim, Seonah; Poluektov, Oleg G; Zhang, Wei; Rumbles, Garry; Park, Jaehong

2017-03-29

Ultrafast photoinduced electron transfer (PIET) dynamics of a C 70 -encapsulated bisporphyrin covalent organic polyhedron hybrid (C 70 @COP-5) is studied in a nonpolar toluene medium with fluorescence and transient absorption spectroscopies. This structurally rigid donor (D)-acceptor (A) molecular hybrid offers a new platform featuring conformationally predetermined cofacial D-A orientation with a fixed edge-to-edge separation, R EE (2.8 Å), without the aid of covalent bonds. Sub-picosecond PIET (τ ET ≤ 0.4 ps) and very slow charge recombination (τ CR ≈ 600 ps) dynamics are observed. The origin of these dynamics is discussed in terms of enhanced D-A coupling (V = 675 cm -1 ) and extremely small reorganization energy (λ ≈ 0.18 eV), induced by the intrinsic structural rigidity of the C 70 @COP-5 complex.

Synthesis of nanostructured bio-related materials by hybridization of synthetic polymers with polysaccharides or saccharide residues.

PubMed

Kaneko, Yoshiro; Kadokawa, Jun-Ichi

2006-01-01

In the first part of this review, we describe the synthesis of nanostructured hybrid materials composed of polysaccharides and synthetic polymers. Amylose-synthetic polymer inclusion complexes were synthesized by amylose-forming polymerization using phosphorylase enzyme in the presence of synthetic polymers such as polyethers and polyesters. Alginate-polymethacrylate hybrid materials were prepared by free-radical polymerization of cationic methacrylate in the presence of sodium alginate. These methods allow the simultaneous control of the nanostructure with polymerization, giving well-defined hybrid materials. In the second part of this review, we describe the synthesis of novel glycopolymers with rigid structures. Polyaniline-based glycopolymers were synthesized by means of oxidative polymerization of N-glycosylaniline. Polysiloxane-based glycopolymers were prepared by means of introduction of sugar-lactone to the rodlike polysiloxane. These glycopolymers had regular higher-ordered structures due to their rigid polymer backbones, resulting in control of the three-dimensional array of sugar-residues.

Non-rigid molecule of copper(II) diiminate Cu[CF3C(NH)C(F)C(NH)CF3]2, its conformational polymorphism in crystal and structure in solutions (Raman, UV-vis and quantum chemistry study)

NASA Astrophysics Data System (ADS)

Bukalov, Sergey S.; Aysin, Rinat R.; Leites, Larissa A.; Kurykin, Mikhail A.; Khrustalev, Victor N.

2015-10-01

Calculation of potential energy surface (PES) of isolated molecule of copper(II) diiminate Cu[CF3С(NH)C(F)C(NH)CF3]2 (1) resulted a double-well curve with the minima corresponding to equivalent screwed conformations. The low barrier leads to molecular non-rigidity which seems to be the reason of conformational polymorphism in crystals, reported in [1]. For one of newly found polymorphs, the X-ray structure was determined. The differences in the Raman and UV-vis spectra between differently colored species and their solutions were revealed, they are determined by different geometries of Cu(II) coordination polyhedron and different systems of intermolecular interactions in crystals. Transformations of the polymorphs under thermal, mechanical and photo exposures were studied.

The dynamics and control of large flexible space structures-IV

NASA Technical Reports Server (NTRS)

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

1981-01-01

The effects of solar radiation pressure as the main environmental disturbance torque were incorporated into the model of the rigid orbiting shallow shell and computer simulation results indicate that within the linear range the rigid modal amplitudes are excited in proportion to the area to mass ratio. The effect of higher order terms in the gravity-gradient torque expressions previously neglected was evaluated and found to be negligible for the size structures under consideration. A graph theory approach was employed for calculating the eigenvalues of a large flexible system by reducing the system (stiffness) matrix to lower ordered submatrices. The related reachability matrix and term rank concepts are used to verify controllability and can be more effective than the alternate numerical rank tests. Control laws were developed for the shape and orientation control of the orbiting flexible shallow shell and numerical results presented.

Increased medial longitudinal arch mobility, lower extremity kinematics, and ground reaction forces in high-arched runners.

PubMed

Williams, D S Blaise; Tierney, Robin N; Butler, Robert J

2014-01-01

Runners with high medial longitudinal arch structure demonstrate unique kinematics and kinetics that may lead to running injuries. The mobility of the midfoot as measured by the change in arch height is also suspected to play a role in lower extremity function during running. The effect of arch mobility in high-arched runners is an important factor in prescribing footwear, training, and rehabilitating the running athlete after injury. To examine the effect of medial longitudinal arch mobility on running kinematics, ground reaction forces, and loading rates in high-arched runners. Cross-sectional study. Human movement research laboratory. A total of 104 runners were screened for arch height. Runners were then identified as having high arches if the arch height index was greater than 0.5 SD above the mean. Of the runners with high arches, 11 rigid runners with the lowest arch mobility (R) were compared with 8 mobile runners with the highest arch mobility (M). Arch mobility was determined by calculating the left arch height index in all runners. Three-dimensional motion analysis of running over ground. Rearfoot and tibial angular excursions, eversion-to-tibial internal-rotation ratio, vertical ground reaction forces, and the associated loading rates. Runners with mobile arches exhibited decreased tibial internal-rotation excursion (mobile: 5.6° ± 2.3° versus rigid: 8.0° ± 3.0°), greater eversion-to-tibial internal-rotation ratio (mobile: 2.1 ± 0.8 versus rigid: 1.5 ± 0.5), decreased second peak vertical ground reaction force values (mobile: 2.3 ± 0.2 × body weight versus rigid: 2.4 ± 0.1 × body weight), and decreased vertical loading rate values (mobile: 55.7 ± 14.1 × body weight/s versus rigid: 65.9 ± 11.4 × body weight/s). Based on the results of this study, it appears that runners with high arch structure but differing arch mobility exhibited differences in select lower extremity movement patterns and forces. Future authors should investigate the impact of arch mobility on running-related injuries.

High Resolution Quantification of Cellular Forces for Rigidity Sensing

NASA Astrophysics Data System (ADS)

Liu, Shuaimin

This thesis describes a comprehensive study of understanding the mechanism of rigidity sensing by quantitative analysis using submicron pillar array substrates. From mechanobiology perspective, we explore and study molecular pathways involved in rigidity and force sensing at cell-matrix adhesions with regard to cancer, regeneration, and development by quantification methods. In Chapter 2 and 3, we developed fabrication and imaging techniques to enhance the performance of a submicron pillar device in terms of spatial and temporal measurement ability, and we discovered a correlation of rigidity sensing forces and corresponding proteins involved in the early rigidity sensing events. In Chapter 2, we introduced optical effect arising from submicron structure imaging, and we described a technique to identify the correct focal plane of pillar tip by fabricating a substrate with designed-offset pillars. From calibration result, we identified the correct focal plane that was previously overlooked, and verified our findings by other imaging techniques. In Chapter 3, we described several techniques to selectively functionalize elastomeric pillars top and compared these techniques in terms of purposes and fabrication complexity. Techniques introduced in this chapter included direct labeling, such as stamping of fluorescent substances (organic dye, nano-diamond, q-dot) to pillars top, as well as indirect labeling that selectively modify the surface of molds with either metal or fluorescent substances. In Chapter 4, we examined the characteristics of local contractility forces and identified the components formed a sarcomere like contractile unit (CU) that cells use to sense rigidity. CUs were found to be assembled at cell edge, contain myosin II, alpha-actinin, tropomodulin and tropomyosin (Tm), and resemble sarcomeres in size (˜2 mum) and function. Then we performed quantitative analysis of CUs to evaluate rigidity sensing activity over ˜8 hours time course and found that density of CUs decrease with time after spreading on stiff substrate. However addition of EGF dramatically increased local contraction activity such that about 30% of the total contractility was in the contraction units. This stimulatory effect was only observed on stiff substrate not on soft. Moreover, we find that in the early interactions of cells with rigid substrates that EGFR activity is needed for normal spreading and the assembly of local contraction units in media lacking serum and any soluble EGF. In Chapter 5, we performed high temporal- and spatial-resolution tracking of contractile forces exerted by cells on sub-micron elastomeric pillars. We found that actomyosin-based sarcomere-like CUs simultaneously moved opposing pillars in net steps of ˜2.5 nm, independent of rigidity. What correlated with rigidity was the number of steps taken to reach a force level that activated recruitment of alpha-actinin to the CUs. When we removed actomyosin restriction by depleting tropomyosin 2.1, we observed larger steps and higher forces that resulted in aberrant rigidity sensing and growth of non-transformed cells on soft matrices. Thus, we conclude that tropomyosin 2.1 acts as a suppressor of growth on soft matrices by supporting proper rigidity sensing.

Electrode for electrochemical cell

DOEpatents

Kaun, T.D.; Nelson, P.A.; Miller, W.E.

1980-05-09

An electrode structure for a secondary electrochemical cell includes an outer enclosure defining a compartment containing electrochemical active material. The enclosure includes a rigid electrically conductive metal sheet with perforated openings over major side surfaces. The enclosure can be assembled as first and second trays each with a rigid sheet of perforated electrically conductive metal at major side surfaces and normally extending flanges at parametric margins. The trays can be pressed together with moldable active material between the two to form an expandable electrode. A plurality of positive and negative electrodes thus formed are arranged in an alternating array with porous frangible interelectrode separators within the housing of the secondary electrochemical cell.

Electrode for electrochemical cell

DOEpatents

Kaun, Thomas D.; Nelson, Paul A.; Miller, William E.

1981-01-01

An electrode structure for a secondary electrochemical cell includes an outer enclosure defining a compartment containing electrochemical active material. The enclosure includes a rigid electrically conductive metal sheet with perforated openings over major side surfaces. The enclosure can be assembled as first and second trays each with a rigid sheet of perforated electrically conductive metal at major side surfaces and normally extending flanges at parametric margins. The trays can be pressed together with moldable active material between the two to form an expandable electrode. A plurality of positive and negative electrodes thus formed are arranged in an alternating array with porous frangible interelectrode separators within the housing of the secondary electrochemical cell.

Theoretical study of solvent effects on the electronic coupling matrix elements in rigidly linked donor-acceptor systems

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

Cave, R.J.; Newton, M.D.; Kumar, K.

1995-12-07

The recently developed generalized Mulliken-Hush approach for the calculation of the electronic coupling matrix element for electron-transfer processes is applied to two rigidly linked donor-bridge-acceptor systems having dimethoxyanthracene as the donor and a dicarbomethoxycyclobutene unit as the acceptor. The dependence of the electronic coupling matrix element as a function of bridge type is examined with and without solvent molecules present. For clamp-shaped bridge structures solvent can have a dramatic effect on the electronic coupling matrix element. The behavior with variation of solvent is in good agreement with that observed experimentally for these systems. 23 refs., 2 tabs.

Effect of the chemical structure of the polymer matrix on the properties of foam polyurethanes at low temperatures

NASA Astrophysics Data System (ADS)

Yakushin, V. A.; Stirna, U. K.; Zhmud', N. P.

1999-07-01

The dependence of physical and mechanical properties of oligoether-based foam polyurethanes on the molecular mass (Mc) of polymer chains between the nodes of the polymer network and on the content of rigid segments in the polymer is investigated at 293 and 98K. The values of Mc at which the foam plastics have the best mechanical properties at low temperatures are determined. The content of rigid segments in the polymer at which foam polyurethanes have the best combination of the linear thermal expansion coefficient and mechanical properties in tension at a temperature of 98K is found.

The prevalence and structure of obsessive-compulsive personality disorder in Hispanic psychiatric outpatients

PubMed Central

Ansell, Emily B.; Pinto, Anthony; Crosby, Ross D.; Becker, Daniel F.; Añez, Luis M.; Paris, Manuel; Grilo, Carlos M.

2010-01-01

This study sought to confirm a multi-factor model of Obsessive-compulsive personality disorder (OCPD) in a Hispanic outpatient sample and to explore associations of the OCPD factors with aggression, depression, and suicidal thoughts. One hundred and thirty monolingual, Spanish-speaking participants were recruited from a community mental health center and were assessed by bilingual doctoral level clinicians. OCPD was highly prevalent (26%) in this sample. Multi-factor models of OCPD were tested and the two factors - perfectionism and interpersonal rigidity - provided the best model fit. Interpersonal rigidity was associated with aggression and anger while perfectionism was associated with depression and suicidal thoughts. PMID:20227063

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter linear deployment repeatability, and sub-degree angular deployment repeatability. Also, an interesting relaxation effect was discovered, as a hinges deployment error would decrease with time.

Coherent anti-Stokes Raman scattering rigid endoscope toward robot-assisted surgery.

PubMed

Hirose, K; Aoki, T; Furukawa, T; Fukushima, S; Niioka, H; Deguchi, S; Hashimoto, M

2018-02-01

Label-free visualization of nerves and nervous plexuses will improve the preservation of neurological functions in nerve-sparing robot-assisted surgery. We have developed a coherent anti-Stokes Raman scattering (CARS) rigid endoscope to distinguish nerves from other tissues during surgery. The developed endoscope, which has a tube with a diameter of 12 mm and a length of 270 mm, achieved 0.91% image distortion and 8.6% non-uniformity of CARS intensity in the whole field of view (650 μm diameter). We demonstrated CARS imaging of a rat sciatic nerve and visualization of the fine structure of nerve fibers.

Rigid polyurethane foam as an efficient material for shock wave attenuation

NASA Astrophysics Data System (ADS)

Komissarov, P. V.; Borisov, A. A.; Sokolov, G. N.; Lavrov, V. V.

2016-09-01

A new method for reducing parameters of blast waves generated by explosions of HE charges on ground is presented. Most of the traditional techniques reduce the wave parameters at a certain distance from the charge, i.e. as a matter of fact the damping device interacts with a completely formed shock wave. The proposed approach is to use rigid polyurethane foam coating immediately the explosive charge. A distributed structure of such a foam block that provides most efficient shock wave attenuation is suggested. Results of experimental shock wave investigations recorded in tests in which HE charges have been exploded with damping devices and without it are compared.

Large space erectable structures - building block structures study

NASA Technical Reports Server (NTRS)

Armstrong, W. H.; Skoumal, D. E.; Straayer, J. W.

1977-01-01

A modular planar truss structure and a long slender boom concept identified as building block approaches to construction of large spacecraft configurations are described. The concepts are compatible in weight and volume goals with the Space Transportation System, use standard structural units, and represent high on-orbit productivity in terms of structural area or beam length. Results of structural trade studies involving static and dynamic analyses of a single module and rigid body deployment analyses to assess kinetics and kinematics of automatic deployment of the building block modules are presented.

Rigid proteins and softening of biological membranes-with application to HIV-induced cell membrane softening.

PubMed

Agrawal, Himani; Zelisko, Matthew; Liu, Liping; Sharma, Pradeep

2016-05-06

A key step in the HIV-infection process is the fusion of the virion membrane with the target cell membrane and the concomitant transfer of the viral RNA. Experimental evidence suggests that the fusion is preceded by considerable elastic softening of the cell membranes due to the insertion of fusion peptide in the membrane. What are the mechanisms underpinning the elastic softening of the membrane upon peptide insertion? A broader question may be posed: insertion of rigid proteins in soft membranes ought to stiffen the membranes not soften them. However, experimental observations perplexingly appear to show that rigid proteins may either soften or harden membranes even though conventional wisdom only suggests stiffening. In this work, we argue that regarding proteins as merely non-specific rigid inclusions is flawed, and each protein has a unique mechanical signature dictated by its specific interfacial coupling to the surrounding membrane. Predicated on this hypothesis, we have carried out atomistic simulations to investigate peptide-membrane interactions. Together with a continuum model, we reconcile contrasting experimental data in the literature including the case of HIV-fusion peptide induced softening. We conclude that the structural rearrangements of the lipids around the inclusions cause the softening or stiffening of the biological membranes.

Rigid proteins and softening of biological membranes—with application to HIV-induced cell membrane softening

NASA Astrophysics Data System (ADS)

Agrawal, Himani; Zelisko, Matthew; Liu, Liping; Sharma, Pradeep

2016-05-01

A key step in the HIV-infection process is the fusion of the virion membrane with the target cell membrane and the concomitant transfer of the viral RNA. Experimental evidence suggests that the fusion is preceded by considerable elastic softening of the cell membranes due to the insertion of fusion peptide in the membrane. What are the mechanisms underpinning the elastic softening of the membrane upon peptide insertion? A broader question may be posed: insertion of rigid proteins in soft membranes ought to stiffen the membranes not soften them. However, experimental observations perplexingly appear to show that rigid proteins may either soften or harden membranes even though conventional wisdom only suggests stiffening. In this work, we argue that regarding proteins as merely non-specific rigid inclusions is flawed, and each protein has a unique mechanical signature dictated by its specific interfacial coupling to the surrounding membrane. Predicated on this hypothesis, we have carried out atomistic simulations to investigate peptide-membrane interactions. Together with a continuum model, we reconcile contrasting experimental data in the literature including the case of HIV-fusion peptide induced softening. We conclude that the structural rearrangements of the lipids around the inclusions cause the softening or stiffening of the biological membranes.

CT-derived indices of canine osteosarcoma-affected antebrachial strength.

PubMed

Garcia, Tanya C; Steffey, Michele A; Zwingenberger, Allison L; Daniel, Leticia; Stover, Susan M

2017-05-01

To improve the prediction of fractures in dogs with bone tumors of the distal radius by identifying computed tomography (CT) indices that correlate with antebrachial bone strength and fracture location. Prospective experimental study. Dogs with antebrachial osteosarcoma (n = 10), and normal cadaver bones (n=9). Antebrachia were imaged with quantitative CT prior to biomechanical testing to failure. CT indices of structural properties were compared to yield force and maximum force using Pearson correlation tests. Straight beam failure (Fs), axial rigidity, curved beam failure (Fc), and craniocaudal bending moment of inertia (MOICrCd) CT indices most highly correlated (0.77 > R > 0.57) with yield and maximum forces when iOSA-affected and control bones were included in the analysis. Considering only OSA-affected bones, Fs, Fc, and axial rigidity correlated highly (0.85 > R > 0.80) with maximum force. In affected bones, the location of minimum axial rigidity and maximum MOICrCd correlated highly (R > 0.85) with the actual fracture location. CT-derived axial rigidity, Fs, and MOICrCd have strong linear relationships with yield and maximum force. These indices should be further evaluated prospectively in OSA-affected dogs that do, and do not, experience pathologic fracture. © 2017 The American College of Veterinary Surgeons.

Generation of 3D templates of active sites of proteins with rigid prosthetic groups.

PubMed

Nebel, Jean-Christophe

2006-05-15

With the increasing availability of protein structures, the generation of biologically meaningful 3D patterns from the simultaneous alignment of several protein structures is an exciting prospect: active sites could be better understood, protein functions and protein 3D structures could be predicted more accurately. Although patterns can already be generated at the fold and topological levels, no system produces high-resolution 3D patterns including atom and cavity positions. To address this challenge, our research focuses on generating patterns from proteins with rigid prosthetic groups. Since these groups are key elements of protein active sites, the generated 3D patterns are expected to be biologically meaningful. In this paper, we present a new approach which allows the generation of 3D patterns from proteins with rigid prosthetic groups. Using 237 protein chains representing proteins containing porphyrin rings, our method was validated by comparing 3D templates generated from homologues with the 3D structure of the proteins they model. Atom positions were predicted reliably: 93% of them had an accuracy of 1.00 A or less. Moreover, similar results were obtained regarding chemical group and cavity positions. Results also suggested our system could contribute to the validation of 3D protein models. Finally, a 3D template was generated for the active site of human cytochrome P450 CYP17, the 3D structure of which is unknown. Its analysis showed that it is biologically meaningful: our method detected the main patterns of the cytochrome P450 superfamily and the motifs linked to catalytic reactions. The 3D template also suggested the position of a residue, which could be involved in a hydrogen bond with CYP17 substrates and the shape and location of a cavity. Comparisons with independently generated 3D models comforted these hypotheses. Alignment software (Nestor3D) is available at http://www.kingston.ac.uk/~ku33185/Nestor3D.html

Analytical solution and numerical study on water hammer in a pipeline closed with an elastically attached valve

NASA Astrophysics Data System (ADS)

Henclik, Sławomir

2018-03-01

The influence of dynamic fluid-structure interaction (FSI) onto the course of water hammer (WH) can be significant in non-rigid pipeline systems. The essence of this effect is the dynamic transfer of liquid energy to the pipeline structure and back, which is important for elastic structures and can be negligible for rigid ones. In the paper a special model of such behavior is analyzed. A straight pipeline with a steady flow, fixed to the floor with several rigid supports is assumed. The transient is generated by a quickly closed valve installed at the end of the pipeline. FSI effects are assumed to be present mainly at the valve which is fixed with a spring dash-pot attachment. Analysis of WH runs, especially transient pressure changes, for various stiffness and damping parameters of the spring dash-pot valve attachment is presented in the paper. The solutions are found analytically and numerically. Numerical results have been computed with the use of an own computer program developed on the basis of the four equation model of WH-FSI and the specific boundary conditions formulated at the valve. Analytical solutions have been found with the separation of variables method for slightly simplified assumptions. Damping at the dash-pot is taken into account within the numerical study. The influence of valve attachment parameters onto the WH courses was discovered and it was found the transient amplitudes can be reduced. Such a system, elastically attached shut-off valve in a pipeline or other, equivalent design can be a real solution applicable in practice.

Development of thin semi-rigid coaxial cables as low-pass filter using bilayer structure in center conductors

NASA Astrophysics Data System (ADS)

Kushino, Akihiro; Yamamoto, Yusei; Okuyama, Tetsuya; Kasai, Soichi

We have developed and evaluated thin semi-rigid coaxial cables as the noise filter for readout in low temperature experiments. The cables reported have 0.86 mm outer diameters consisting of seamless outer conductor, polytetrafluoroethylene (PTFE) dielectric, and center conductor made of superconducting niobium-titanium (NbTi). Each center conductor has surficial cladding made of normal conductor in different thickness. We had reported that we can adjust attenuation magnitude and cut-off frequency of the semi-rigid cable in the range about 100 500 MHz by controlling cable length and/or thickness of cladding. We newly manufactured this type of low-pass filter cables using stainless-steel (SUS304) as the material for cladding which has higher electrical resistivity than that of cupro-nickel (CuNi). It enables high filtering efficiency, i.e. large attenuation at the same frequency, compared to those made of conventional CuNi-based low-pass-filter cables.

Two-dimensional membrane as elastic shell with proof on the folds revealed by three-dimensional atomic mapping

NASA Astrophysics Data System (ADS)

Zhao, Jiong; Deng, Qingming; Ly, Thuc Hue; Han, Gang Hee; Sandeep, Gorantla; Rümmeli, Mark H.

2015-11-01

The great application potential for two-dimensional (2D) membranes (MoS2, WSe2, graphene and so on) aroused much effort to understand their fundamental mechanical properties. The out-of-plane bending rigidity is the key factor that controls the membrane morphology under external fields. Herein we provide an easy method to reconstruct the 3D structures of the folded edges of these 2D membranes on the atomic scale, using high-resolution (S)TEM images. After quantitative comparison with continuum mechanics shell model, it is verified that the bending behaviour of the studied 2D materials can be well explained by the linear elastic shell model. And the bending rigidities can thus be derived by fitting with our experimental results. Recall almost only theoretical approaches can access the bending properties of these 2D membranes before, now a new experimental method to measure the bending rigidity of such flexible and atomic thick 2D membranes is proposed.

Ethylene vinyl alcohol: a review of barrier properties for packaging shelf stable foods.

PubMed

Mokwena, K Khanah; Tang, Juming

2012-01-01

Ethylene vinyl alcohol (EVOH) is one of the best known flexible thermoplastic oxygen barrier materials in use today. It is especially important for refrigerated and shelf-stable foods where oxygen deteriorates the quality of packaged products and reduces their shelf life. EVOH accounts for a majority of thermoplastic barrier materials used for rigid or semi-rigid retortable food containers. However. it is of limited use in flexible packages or lid films for rigid trays used for packaging thermally processed shelf-stable low acid foods due to its moisture sensitivity. Nevertheless, current use of other oxygen barrier materials such as polyvinylidene chloride and aluminum foil creates environmental concerns. Innovations in food processing technologies provide opportunities for increased use of EVOH in food packaging. The aim of this review is to give an overview of research on the oxygen barrier properties of EVOH from the perspective of structure-barrier property relationships and the consequences of food processing conditions.

A DFFD simulation method combined with the spectral element method for solid-fluid-interaction problems

NASA Astrophysics Data System (ADS)

Chen, Li-Chieh; Huang, Mei-Jiau

2017-02-01

A 2D simulation method for a rigid body moving in an incompressible viscous fluid is proposed. It combines one of the immersed-boundary methods, the DFFD (direct forcing fictitious domain) method with the spectral element method; the former is employed for efficiently capturing the two-way FSI (fluid-structure interaction) and the geometric flexibility of the latter is utilized for any possibly co-existing stationary and complicated solid or flow boundary. A pseudo body force is imposed within the solid domain to enforce the rigid body motion and a Lagrangian mesh composed of triangular elements is employed for tracing the rigid body. In particular, a so called sub-cell scheme is proposed to smooth the discontinuity at the fluid-solid interface and to execute integrations involving Eulerian variables over the moving-solid domain. The accuracy of the proposed method is verified through an observed agreement of the simulation results of some typical flows with analytical solutions or existing literatures.

Self Assembled Bi-functional Peptide Hydrogels with Biomineralization-Directing Peptides

PubMed Central

Gungormus, Mustafa; Branco, Monica; Fong, Hanson; Schneider, Joel P.; Tamerler, Candan; Sarikaya, Mehmet

2014-01-01

A peptide-based hydrogel has been designed that directs the formation of hydroxyapatite. MDG1, a twenty-seven residue peptide, undergoes triggered folding to form an unsymmetrical β-hairpin that self-assembles in response to an increase in solution ionic strength to yield a mechanically rigid, self supporting hydrogel. The C-terminal portion of MDG1 contains a heptapeptide (MLPHHGA) capable of directing the mineralization process. Circular dichroism spectroscopy indicates that the peptide folds and assembles to form a hydrogel network rich in β-sheet secondary structure. Oscillatory rheology indicates that the hydrogel is mechanical rigid (G′ ∼ 2500 Pa) before mineralization. In separate experiments, mineralization was induced both biochemically and with cementoblast cells. Mineralization-domain had little effect on the mechanical rigidity of the gel. SEM and EDS show that MDG1 gels are capable of directing the formation of hydroxapatite. Control hydrogels, prepared by peptides either lacking the mineral-directing portion or reversing its sequence, indicated that the heptapeptide is necessary and its actions are sequence specific. PMID:20591477

Synthesis of rigid polyurethane foams from phosphorylated biopolyols.

PubMed

de Haro, Juan Carlos; López-Pedrajas, Daniel; Pérez, Ángel; Rodríguez, Juan Francisco; Carmona, Manuel

2017-08-18

Renewable resources are playing a key role on the synthesis of biodegradable polyols. Moreover, the incorporation of covalently linked additives is increasing in importance in the polyurethane (PU) market. In this work, previously epoxidized grape seed oil and methyl oleate were transformed into phosphorylated biopolyols through an acid-catalyzed ring-opening hydrolysis in the presence of H 3 PO 4 . The formation of phosphate polyesters was confirmed by FT-IR and 31 P-NMR. However, the synthesis of a high-quality PU rigid foam was not possible using exclusively these polyols attending to their low hydroxyl value. In that way, different rigid PU foams were prepared from the phosphorylated biopolyols and the commercial polyol Alcupol R4520. It was observed that phosphorylated biopolyols can be incorporated up to a 57 wt.% in the PU synthesis without significant structural changes with respect to the commercial foam. Finally, thermogravimetric and EDAX analyses revealed an improvement of thermal stability by the formation of a protective phosphorocarbonaceous char layer.

Sound absorption by clamped poroelastic plates.

PubMed

Aygun, H; Attenborough, K

2008-09-01

Measurements and predictions have been made of the absorption coefficient and the surface acoustic impedance of poroelastic plates clamped in a large impedance tube and separated from the rigid termination by an air gap. The measured and predicted absorption coefficient and surface impedance spectra exhibit low frequency peaks. The peak frequencies observed in the absorption coefficient are close to those predicted and measured in the deflection spectra of the clamped poroelastic plates. The influences of the rigidity of the clamping conditions and the width of the air gap have been investigated. Both influences are found to be important. Increasing the rigidity of clamping reduces the low frequency absorption peaks compared with those measured for simply supported plates or plates in an intermediate clamping condition. Results for a closed cell foam plate and for two open cell foam plates made from recycled materials are presented. For identical clamping conditions and width of air gap, the results for the different materials differ as a consequence mainly of their different elasticity, thickness, and cell structure.

Spectra of variations and cosmic ray anisotropy during GLE of June 11, 1991

NASA Astrophysics Data System (ADS)

Kravtsova, Marina; Sdobnov, Valeriy

2015-03-01

We have studied variation spectra and cosmic-ray (CR) anisotropy, using the ground-based and satellite observations of the CR intensity on the worldwide network of stations during the ground level enhancement (GLE) of June 11, 1991. The spectrographic global survey has been used. Variation spectra of primary CRs at different moments of the event are presented. Note that the CR variation spectra during this period are not described by a power or an exponential function of particle rigidity. The maximum rigidity, up to which the protons were accelerated on June 11, 1991, was ~2.8 GV (06:00 UT; i.e., two hours after GLE started). We show relative variations in the CR intensity in the geocentric solar ecliptic coordinate system during certain periods of the event under study. On June 11, 1991, the bidirectional anisotropy dominated in the distribution of particles with rigidity of 4 GV and 10 GV, which implies that the Earth passed the loop-like IMF structure.

Conformational rigidity in a lattice model of proteins.

PubMed

Collet, Olivier

2003-06-01

It is shown in this paper that some simulations of protein folding in lattice models, which use an incorrect implementation of the Monte Carlo algorithm, do not converge towards thermal equilibrium. I developed a rigorous treatment for protein folding simulation on a lattice model relying on the introduction of a parameter standing for the rigidity of the conformations. Its properties are discussed and its role during the folding process is elucidated. The calculation of thermal properties of small chains living on a two-dimensional lattice is performed and a Bortz-Kalos-Lebowitz scheme is implemented in the presented method in order to study kinetics of chains at very low temperature. The coefficients of the Arrhenius law obtained with this algorithm are found to be in excellent agreement with the value of the main potential barrier of the system. Finally, a scenario of the mechanisms, including the rigidity parameters, that guide a protein towards its native structure, at medium temperature, is given.

Role of isostaticity and load-bearing microstructure in the elasticity of yielded colloidal gels.

PubMed

Hsiao, Lilian C; Newman, Richmond S; Glotzer, Sharon C; Solomon, Michael J

2012-10-02

We report a simple correlation between microstructure and strain-dependent elasticity in colloidal gels by visualizing the evolution of cluster structure in high strain-rate flows. We control the initial gel microstructure by inducing different levels of isotropic depletion attraction between particles suspended in refractive index matched solvents. Contrary to previous ideas from mode coupling and micromechanical treatments, our studies show that bond breakage occurs mainly due to the erosion of rigid clusters that persist far beyond the yield strain. This rigidity contributes to gel elasticity even when the sample is fully fluidized; the origin of the elasticity is the slow Brownian relaxation of rigid, hydrodynamically interacting clusters. We find a power-law scaling of the elastic modulus with the stress-bearing volume fraction that is valid over a range of volume fractions and gelation conditions. These results provide a conceptual framework to quantitatively connect the flow-induced microstructure of soft materials to their nonlinear rheology.

71. Meadow Creek Culvert. This is an example of a ...

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

71. Meadow Creek Culvert. This is an example of a triple arch concrete box culvert with stone facing mimicking rigid frame structures. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

Optimization of thrie beam terminal end shoe connection.

DOT National Transportation Integrated Search

2017-04-01

Terminal thrie end shoes connect nested thrie beams to parapets or other bridge rail structure to provide a robust connectivity between a transition section and a rigid railing section. When connecting terminal end shoe to thrie beam transitions, the...

Rigid cable support for blind installations

NASA Technical Reports Server (NTRS)

Abbott, J. R.

1977-01-01

Mechanical support structure, originally designed for use with electrical cables, can support hydraulic, pneumatic, and cryogenic lines where bends are required, assemblies are inaccessible, and conduits are impractical. Support is also light in weight and offers means of damping vibration.

Highly cross-linked nanoporous polymers

DOEpatents

Steckle, W.P. Jr.; Apen, P.G.; Mitchell, M.A.

1998-01-20

Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes. 1 fig.

Computational Analysis of Effect of Transient Fluid Force on Composite Structures

DTIC Science & Technology

2013-12-01

as they well represent an E-glass fiber reinforced composite frequently used in research and industrial applications. The fluid domain was sized...provide unique perspectives on peak stress ratios . The two models both share increased structural rigidity. The cylinder is reinforced by... Poisson ratio of 0.3 and Young’s modulus of 20 GPa were added to the transient structural engineering data cell (Figure 69). 78 Figure 69. E-Glass

Surface Modification and Nanojunction Fabrication with Molecular Metal Wires

DTIC Science & Technology

2014-02-17

Title: Transition Metal Complexes of a Super Rigid Anthyridine Ligand: Structural, Magnetic and DFT Studies. Transition metal complexes of iron ( II ...Compounds with Masked Diazonium Capping Groups (J. Organomet. Chem. 2013, 745, 93). (3) New Diruthenium( II ,III) Compounds Bearing Terminal Olefin Groups...2012, 36, 2340). (2) Synthesis , Structure, Magnetism, and Single Molecular Conductance of Linear Trinickel String Complexes with Sulfur-Containing

Solar-Array Substrate From Glass-Reinforced Concrete

NASA Technical Reports Server (NTRS)

Eirls, J. L.

1985-01-01

Design elminiates glass superstrate and associated metal framing. Panel has two trapezoidal stiffening ribs for structural support. Strategic placement of ribs with embedded support tubes (standard PVC tubing) minimizes bending moments and resulting stresses produced by installation and windloads. Glass-reinforced concrete panel has smooth flat surface suitable for solar substrate and includes structural bracing for rigidity and design adaptable to mass production.

The influence of computational assumptions on analysing abdominal aortic aneurysm haemodynamics.

PubMed

Ene, Florentina; Delassus, Patrick; Morris, Liam

2014-08-01

The variation in computational assumptions for analysing abdominal aortic aneurysm haemodynamics can influence the desired output results and computational cost. Such assumptions for abdominal aortic aneurysm modelling include static/transient pressures, steady/transient flows and rigid/compliant walls. Six computational methods and these various assumptions were simulated and compared within a realistic abdominal aortic aneurysm model with and without intraluminal thrombus. A full transient fluid-structure interaction was required to analyse the flow patterns within the compliant abdominal aortic aneurysms models. Rigid wall computational fluid dynamics overestimates the velocity magnitude by as much as 40%-65% and the wall shear stress by 30%-50%. These differences were attributed to the deforming walls which reduced the outlet volumetric flow rate for the transient fluid-structure interaction during the majority of the systolic phase. Static finite element analysis accurately approximates the deformations and von Mises stresses when compared with transient fluid-structure interaction. Simplifying the modelling complexity reduces the computational cost significantly. In conclusion, the deformation and von Mises stress can be approximately found by static finite element analysis, while for compliant models a full transient fluid-structure interaction analysis is required for acquiring the fluid flow phenomenon. © IMechE 2014.

Towards accurate modeling of noncovalent interactions for protein rigidity analysis.

PubMed

Fox, Naomi; Streinu, Ileana

2013-01-01

Protein rigidity analysis is an efficient computational method for extracting flexibility information from static, X-ray crystallography protein data. Atoms and bonds are modeled as a mechanical structure and analyzed with a fast graph-based algorithm, producing a decomposition of the flexible molecule into interconnected rigid clusters. The result depends critically on noncovalent atomic interactions, primarily on how hydrogen bonds and hydrophobic interactions are computed and modeled. Ongoing research points to the stringent need for benchmarking rigidity analysis software systems, towards the goal of increasing their accuracy and validating their results, either against each other and against biologically relevant (functional) parameters. We propose two new methods for modeling hydrogen bonds and hydrophobic interactions that more accurately reflect a mechanical model, without being computationally more intensive. We evaluate them using a novel scoring method, based on the B-cubed score from the information retrieval literature, which measures how well two cluster decompositions match. To evaluate the modeling accuracy of KINARI, our pebble-game rigidity analysis system, we use a benchmark data set of 20 proteins, each with multiple distinct conformations deposited in the Protein Data Bank. Cluster decompositions for them were previously determined with the RigidFinder method from Gerstein's lab and validated against experimental data. When KINARI's default tuning parameters are used, an improvement of the B-cubed score over a crude baseline is observed in 30% of this data. With our new modeling options, improvements were observed in over 70% of the proteins in this data set. We investigate the sensitivity of the cluster decomposition score with case studies on pyruvate phosphate dikinase and calmodulin. To substantially improve the accuracy of protein rigidity analysis systems, thorough benchmarking must be performed on all current systems and future extensions. We have measured the gain in performance by comparing different modeling methods for noncovalent interactions. We showed that new criteria for modeling hydrogen bonds and hydrophobic interactions can significantly improve the results. The two new methods proposed here have been implemented and made publicly available in the current version of KINARI (v1.3), together with the benchmarking tools, which can be downloaded from our software's website, http://kinari.cs.umass.edu.

Towards accurate modeling of noncovalent interactions for protein rigidity analysis

PubMed Central

2013-01-01

Background Protein rigidity analysis is an efficient computational method for extracting flexibility information from static, X-ray crystallography protein data. Atoms and bonds are modeled as a mechanical structure and analyzed with a fast graph-based algorithm, producing a decomposition of the flexible molecule into interconnected rigid clusters. The result depends critically on noncovalent atomic interactions, primarily on how hydrogen bonds and hydrophobic interactions are computed and modeled. Ongoing research points to the stringent need for benchmarking rigidity analysis software systems, towards the goal of increasing their accuracy and validating their results, either against each other and against biologically relevant (functional) parameters. We propose two new methods for modeling hydrogen bonds and hydrophobic interactions that more accurately reflect a mechanical model, without being computationally more intensive. We evaluate them using a novel scoring method, based on the B-cubed score from the information retrieval literature, which measures how well two cluster decompositions match. Results To evaluate the modeling accuracy of KINARI, our pebble-game rigidity analysis system, we use a benchmark data set of 20 proteins, each with multiple distinct conformations deposited in the Protein Data Bank. Cluster decompositions for them were previously determined with the RigidFinder method from Gerstein's lab and validated against experimental data. When KINARI's default tuning parameters are used, an improvement of the B-cubed score over a crude baseline is observed in 30% of this data. With our new modeling options, improvements were observed in over 70% of the proteins in this data set. We investigate the sensitivity of the cluster decomposition score with case studies on pyruvate phosphate dikinase and calmodulin. Conclusion To substantially improve the accuracy of protein rigidity analysis systems, thorough benchmarking must be performed on all current systems and future extensions. We have measured the gain in performance by comparing different modeling methods for noncovalent interactions. We showed that new criteria for modeling hydrogen bonds and hydrophobic interactions can significantly improve the results. The two new methods proposed here have been implemented and made publicly available in the current version of KINARI (v1.3), together with the benchmarking tools, which can be downloaded from our software's website, http://kinari.cs.umass.edu. PMID:24564209

A stable partitioned FSI algorithm for rigid bodies and incompressible flow. Part I: Model problem analysis

NASA Astrophysics Data System (ADS)

Banks, J. W.; Henshaw, W. D.; Schwendeman, D. W.; Tang, Qi

2017-08-01

A stable partitioned algorithm is developed for fluid-structure interaction (FSI) problems involving viscous incompressible flow and rigid bodies. This added-mass partitioned (AMP) algorithm remains stable, without sub-iterations, for light and even zero mass rigid bodies when added-mass and viscous added-damping effects are large. The scheme is based on a generalized Robin interface condition for the fluid pressure that includes terms involving the linear acceleration and angular acceleration of the rigid body. Added-mass effects are handled in the Robin condition by inclusion of a boundary integral term that depends on the pressure. Added-damping effects due to the viscous shear forces on the body are treated by inclusion of added-damping tensors that are derived through a linearization of the integrals defining the force and torque. Added-damping effects may be important at low Reynolds number, or, for example, in the case of a rotating cylinder or rotating sphere when the rotational moments of inertia are small. In this first part of a two-part series, the properties of the AMP scheme are motivated and evaluated through the development and analysis of some model problems. The analysis shows when and why the traditional partitioned scheme becomes unstable due to either added-mass or added-damping effects. The analysis also identifies the proper form of the added-damping which depends on the discrete time-step and the grid-spacing normal to the rigid body. The results of the analysis are confirmed with numerical simulations that also demonstrate a second-order accurate implementation of the AMP scheme.

Analysis of forward scattering of an acoustical zeroth-order Bessel beam from rigid complicated (aspherical) structures

NASA Astrophysics Data System (ADS)

Li, Wei; Chai, Yingbin; Gong, Zhixiong; Marston, Philip L.

2017-10-01

The forward scattering from rigid spheroids and endcapped cylinders with finite length (even with a large aspect ratio) immersed in a non-viscous fluid under the illumination of an idealized zeroth-order acoustical Bessel beam (ABB) with arbitrary angles of incidence is calculated and analyzed in the implementation of the T-matrix method (TTM). Based on the present method, the incident coefficients of expansion for the incident ABB are derived and simplifying methods are proposed for the numerical accuracy and computational efficiency according to the geometrical symmetries. A home-made MATLAB software package is constructed accordingly, and then verified and validated for the ABB scattering from rigid aspherical obstacles. Several numerical examples are computed for the forward scattering from both rigid spheroids and finite cylinder, with particular emphasis on the aspect ratios, the half-cone angles of ABBs, the incident angles and the dimensionless frequencies. The rectangular patterns of target strength in the (β, θs) domain (where β is the half-cone angle of the ABB and θs is the scattered polar angle) and local/total forward scattering versus dimensionless frequency are exhibited, which could provide new insights into the physical mechanisms of Bessel beam scattering by rigid spheroids and finite cylinders. The ray diagrams in geometrical models for the scattering in the forward half-space and the optical cross-section theorem help to interpret the scattering mechanisms of ABBs. This research work may provide an alternative for the partial wave series solution under certain circumstances interacting with ABBs for complicated obstacles and benefit some related works in optics and electromagnetics.

Accelerating molecular Monte Carlo simulations using distance and orientation dependent energy tables: tuning from atomistic accuracy to smoothed “coarse-grained” models

PubMed Central

Lettieri, S.; Zuckerman, D.M.

2011-01-01

Typically, the most time consuming part of any atomistic molecular simulation is due to the repeated calculation of distances, energies and forces between pairs of atoms. However, many molecules contain nearly rigid multi-atom groups such as rings and other conjugated moieties, whose rigidity can be exploited to significantly speed up computations. The availability of GB-scale random-access memory (RAM) offers the possibility of tabulation (pre-calculation) of distance and orientation-dependent interactions among such rigid molecular bodies. Here, we perform an investigation of this energy tabulation approach for a fluid of atomistic – but rigid – benzene molecules at standard temperature and density. In particular, using O(1) GB of RAM, we construct an energy look-up table which encompasses the full range of allowed relative positions and orientations between a pair of whole molecules. We obtain a hardware-dependent speed-up of a factor of 24-50 as compared to an ordinary (“exact”) Monte Carlo simulation and find excellent agreement between energetic and structural properties. Second, we examine the somewhat reduced fidelity of results obtained using energy tables based on much less memory use. Third, the energy table serves as a convenient platform to explore potential energy smoothing techniques, akin to coarse-graining. Simulations with smoothed tables exhibit near atomistic accuracy while increasing diffusivity. The combined speed-up in sampling from tabulation and smoothing exceeds a factor of 100. For future applications greater speed-ups can be expected for larger rigid groups, such as those found in biomolecules. PMID:22120971

Focal adhesions, stress fibers and mechanical tension

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

Burridge, Keith, E-mail: Keith_Burridge@med.unc.edu; Guilluy, Christophe, E-mail: christophe.guilluy@univ-nantes.fr

Stress fibers and focal adhesions are complex protein arrays that produce, transmit and sense mechanical tension. Evidence accumulated over many years led to the conclusion that mechanical tension generated within stress fibers contributes to the assembly of both stress fibers themselves and their associated focal adhesions. However, several lines of evidence have recently been presented against this model. Here we discuss the evidence for and against the role of mechanical tension in driving the assembly of these structures. We also consider how their assembly is influenced by the rigidity of the substratum to which cells are adhering. Finally, we discussmore » the recently identified connections between stress fibers and the nucleus, and the roles that these may play, both in cell migration and regulating nuclear function. - Highlights: • The different types of stress fiber and focal adhesion are described. • We discuss the controversy about tension and assembly of these structures. • We describe the different models used to investigate assembly of these structures. • The influence of substratum rigidity is discussed. • Stress fiber connections to the nucleus are reviewed.« less

Dynamic and Structural Performances of a New Sailcraft Concept for Interplanetary Missions.

PubMed

Peloni, Alessandro; Barbera, Daniele; Laurenzi, Susanna; Circi, Christian

2015-01-01

Typical square solar-sail design is characterised by a central hub with four-quadrant sails, conferring to the spacecraft the classical X-configuration. One of the critical aspects related to this architecture is due to the large deformations of both membrane and booms, which leads to a reduction of the performance of the sailcraft in terms of thrust efficiency. As a consequence, stiffer sail architecture would be desirable, taking into account that the rigidity of the system strongly affects the orbital dynamics. In this paper, we propose a new solar-sail architecture, which is more rigid than the classical X-configuration. Among the main pros and cons that the proposed configuration presents, this paper aims to show the general concept, investigating the performances from the perspectives of both structural response and attitude control. Membrane deformations, structural offset, and sail vibration frequencies are determined through finite element method, adopting a variable pretensioning scheme. In order to evaluate the manoeuvring performances of this new solar-sail concept, a 35-degree manoeuvre is studied using a feedforward and feedback controller.

Inflatable habitation for the lunar base

NASA Technical Reports Server (NTRS)

Roberts, M.

1992-01-01

Inflatable structures have a number of advantages over rigid modules in providing habitation at a lunar base. Some of these advantages are packaging efficiency, convenience of expansion, flexibility, and psychological benefit to the inhabitants. The relatively small, rigid cylinders fitted to the payload compartment of a launch vehicle are not as efficient volumetrically as a collapsible structure that fits into the same space when packaged, but when deployed is much larger. Pressurized volume is a valuable resource. By providing that resource efficiently, in large units, labor intensive external expansion (such as adding additional modules to the existing base) can be minimized. The expansive interior in an inflatable would facilitate rearrangement of the interior to suite the evolving needs of the base. This large, continuous volume would also relieve claustrophobia, enhancing habitability and improving morale. The purpose of this paper is to explore some of the aspects of inflatable habitat design, including structural, architectural, and environmental considerations. As a specific case, the conceptual design of an inflatable lunar habitat, developed for the Lunar Base Systems Study at the Johnson Space Center, is described.

Engagement of Arginine Finger to ATP Triggers Large Conformational Changes in NtrC1 AAA+ ATPase for Remodeling Bacterial RNA Polymerase

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

Chen, Baoyu; Sysoeva, Tatyana A.; Chowdhury, Saikat

The NtrC-like AAA+ ATPases control virulence and other important bacterial activities through delivering mechanical work to {sigma}54-RNA polymerase to activate transcription from {sigma}54-dependent genes. We report the first crystal structure for such an ATPase, NtrC1 of Aquifex aeolicus, in which the catalytic arginine engages the {gamma}-phosphate of ATP. Comparing the new structure with those previously known for apo and ADP-bound states supports a rigid-body displacement model that is consistent with large-scale conformational changes observed by low-resolution methods. First, the arginine finger induces rigid-body roll, extending surface loops above the plane of the ATPase ring to bind {sigma}54. Second, ATP hydrolysismore » permits Pi release and retraction of the arginine with a reversed roll, remodeling {sigma}54-RNAP. This model provides a fresh perspective on how ATPase subunits interact within the ring-ensemble to promote transcription, directing attention to structural changes on the arginine-finger side of an ATP-bound interface.« less

Dynamic and Structural Performances of a New Sailcraft Concept for Interplanetary Missions

PubMed Central

Peloni, Alessandro; Barbera, Daniele; Laurenzi, Susanna; Circi, Christian

2015-01-01

Typical square solar-sail design is characterised by a central hub with four-quadrant sails, conferring to the spacecraft the classical X-configuration. One of the critical aspects related to this architecture is due to the large deformations of both membrane and booms, which leads to a reduction of the performance of the sailcraft in terms of thrust efficiency. As a consequence, stiffer sail architecture would be desirable, taking into account that the rigidity of the system strongly affects the orbital dynamics. In this paper, we propose a new solar-sail architecture, which is more rigid than the classical X-configuration. Among the main pros and cons that the proposed configuration presents, this paper aims to show the general concept, investigating the performances from the perspectives of both structural response and attitude control. Membrane deformations, structural offset, and sail vibration frequencies are determined through finite element method, adopting a variable pretensioning scheme. In order to evaluate the manoeuvring performances of this new solar-sail concept, a 35-degree manoeuvre is studied using a feedforward and feedback controller. PMID:26273697

Numerical and Experimental Studies on Impact Loaded Concrete Structures

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

Saarenheimo, Arja; Hakola, Ilkka; Karna, Tuomo

2006-07-01

An experimental set-up has been constructed for medium scale impact tests. The main objective of this effort is to provide data for the calibration and verification of numerical models of a loading scenario where an aircraft impacts against a nuclear power plant. One goal is to develop and take in use numerical methods for predicting response of reinforced concrete structures to impacts of deformable projectiles that may contain combustible liquid ('fuel'). Loading, structural behaviour, like collapsing mechanism and the damage grade, will be predicted by simple analytical methods and using non-linear FE-method. In the so-called Riera method the behavior ofmore » the missile material is assumed to be rigid plastic or rigid visco-plastic. Using elastic plastic and elastic visco-plastic material models calculations are carried out by ABAQUS/Explicit finite element code, assuming axisymmetric deformation mode for the missile. With both methods, typically, the impact force time history, the velocity of the missile rear end and the missile shortening during the impact were recorded for comparisons. (authors)« less

Rotationally Molded Liquid Crystalline Polymers

NASA Technical Reports Server (NTRS)

Rogers, Martin; Stevenson, Paige; Scribben, Eric; Baird, Donald; Hulcher, Bruce

2002-01-01

Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers advantages of low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semi-rigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers.

Molecular recognition principles and stationary-phase characteristics of topoisomer-selective chemoaffinity materials for chromatographic separation of circular plasmid DNA topoisomers.

PubMed

Mahut, Marek; Lindner, Wolfgang; Lämmerhofer, Michael

2012-01-18

We recently discovered the molecular recognition capability of a quinine carbamate ligand attached to silica as a powerful chemoaffinity material for the chromatographic separation of circular plasmid topoisomers of different linking numbers. In this paper we develop structure-selectivity relationship studies to figure out the essential structural features for topoisomer recognition. By varying different moieties of the original cinchonan-derived selector, it was shown that intercalation by the quinoline moiety of the ligand as assumed initially as the working hypothesis is not an essential feature for topoisomer recognition during chromatography. We found that the key elements for topoisomer selectivity are the presence of a rigid weak anion-exchange site and a H-donor site separated from each other in a defined distance by a 4-atom spacer. Additionally, incorporation of the weak anion-exchange site into a cyclic ring structure provides greater rigidity of the ligand molecule and turned out to be advantageous, if not mandatory, for (close to) baseline separation. © 2011 American Chemical Society

Rattler behavior in As skutterudites and oxy-skutterudites

NASA Astrophysics Data System (ADS)

Bridges, Frank; Car, Brad; Hoffman-Stapleton, Mikaela; Keiber, Trevor; Sutton, Logan; Maple, M. Brian

2014-03-01

We report EXAFS measurements for the series CeX4As12 (X = Fe, Ru, Os) and NdCu3Ru4O12 as a function of temperature for most elements in the structure. In each case the rare earth atom is a ``rattler'' atom, with a low Einstein temperature while the skutterudite cage structure is relatively stiff. From temperature dependencies of the correlated Debye model for the cage atoms, one can estimate the effective spring constant for various atom pairs. We also find for the oxy-skutterudites that the planar CuO4 sub-structure is very stiff, and likely vibrates as a rigid unit. We compare the behavior of the As-skutterudites with other skutterudites and with the oxy-skutterudites, and discuss in terms of the rigid cage model. The second neighbor pair Ce-X for the As-skutterudites is softer than expected while for the oxy-skutterudites the second neighbor Nd-Ru pair is stiffer than the nearest neighbor Nd-O pair. Models are need to explore this behavior. Support: NSF DMR1005568.

Control and dynamics of a flexible spacecraft during stationkeeping maneuvers

NASA Technical Reports Server (NTRS)

Liu, D.; Yocum, J.; Kang, D. S.

1991-01-01

A case study of a spacecraft having flexible solar arrays is presented. A stationkeeping attitude control mode using both earth and rate gyro reference signals and a flexible vehicle dynamics modeling and implementation is discussed. The control system is designed to achieve both pointing accuracy and structural mode stability during stationkeeping maneuvers. Reduction of structural mode interactions over the entire mode duration is presented. The control mode using a discrete time observer structure is described to show the convergence of the spacecraft attitude transients during Delta-V thrusting maneuvers without preloading thrusting bias to the onboard control processor. The simulation performance using the three axis, body stabilized nonlinear dynamics is provided. The details of a five body dynamics model are discussed. The spacecraft is modeled as a central rigid body having cantilevered flexible antennas, a pair of flexible articulated solar arrays, and to gimballed momentum wheels. The vehicle is free to undergo unrestricted rotations and translations relative to inertial space. A direct implementation of the equations of motion is compared to an indirect implementation that uses a symbolic manipulation software to generate rigid body equations.

Self-organization processes in polysiloxane block copolymers, initiated by modifying fullerene additives

NASA Astrophysics Data System (ADS)

Voznyakovskii, A. P.; Kudoyarova, V. Kh.; Kudoyarov, M. F.; Patrova, M. Ya.

2017-08-01

Thin films of a polyblock polysiloxane copolymer and their composites with a modifying fullerene C60 additive are studied by atomic force microscopy, Rutherford backscattering, and neutron scattering. The data of atomic force microscopy show that with the addition of fullerene to the bulk of the polymer matrix, the initial relief of the film surface is leveled more, the larger the additive. This trend is associated with the processes of self-organization of rigid block sequences, which are initiated by the field effect of the surface of fullerene aggregates and lead to an increase in the number of their domains in the bulk of the polymer matrix. The data of Rutherford backscattering and neutron scattering indicate the formation of additional structures with a radius of 60 nm only in films containing fullerene, and their fraction increases with increasing fullerene concentration. A comparative analysis of the data of these methods has shown that such structures are, namely, the domains of a rigid block and are not formed by individual fullerene aggregates. The interrelation of the structure and mechanical properties of polymer films is considered.

Equivalent-Continuum Modeling With Application to Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Odegard, Gregory M.; Gates, Thomas S.; Nicholson, Lee M.; Wise, Kristopher E.

2002-01-01

A method has been proposed for developing structure-property relationships of nano-structured materials. This method serves as a link between computational chemistry and solid mechanics by substituting discrete molecular structures with equivalent-continuum models. It has been shown that this substitution may be accomplished by equating the vibrational potential energy of a nano-structured material with the strain energy of representative truss and continuum models. As important examples with direct application to the development and characterization of single-walled carbon nanotubes and the design of nanotube-based devices, the modeling technique has been applied to determine the effective-continuum geometry and bending rigidity of a graphene sheet. A representative volume element of the chemical structure of graphene has been substituted with equivalent-truss and equivalent continuum models. As a result, an effective thickness of the continuum model has been determined. This effective thickness has been shown to be significantly larger than the interatomic spacing of graphite. The effective thickness has been shown to be significantly larger than the inter-planar spacing of graphite. The effective bending rigidity of the equivalent-continuum model of a graphene sheet was determined by equating the vibrational potential energy of the molecular model of a graphene sheet subjected to cylindrical bending with the strain energy of an equivalent continuum plate subjected to cylindrical bending.

Linking molecular models with ion mobility experiments. Illustration with a rigid nucleic acid structure

PubMed Central

D'Atri, Valentina; Porrini, Massimiliano; Rosu, Frédéric; Gabelica, Valérie

2015-01-01

Ion mobility spectrometry experiments allow the mass spectrometrist to determine an ion's rotationally averaged collision cross section ΩEXP. Molecular modelling is used to visualize what ion three-dimensional structure(s) is(are) compatible with the experiment. The collision cross sections of candidate molecular models have to be calculated, and the resulting ΩCALC are compared with the experimental data. Researchers who want to apply this strategy to a new type of molecule face many questions: (1) What experimental error is associated with ΩEXP determination, and how to estimate it (in particular when using a calibration for traveling wave ion guides)? (2) How to generate plausible 3D models in the gas phase? (3) Different collision cross section calculation models exist, which have been developed for other analytes than mine. Which one(s) can I apply to my systems? To apply ion mobility spectrometry to nucleic acid structural characterization, we explored each of these questions using a rigid structure which we know is preserved in the gas phase: the tetramolecular G-quadruplex [dTGGGGT]4, and we will present these detailed investigation in this tutorial. © 2015 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons Ltd. PMID:26259654

Construction patterns of birds’ nests provide insight into nest-building behaviours

PubMed Central

Goodman, Adrian M.

2017-01-01

Previous studies have suggested that birds and mammals select materials needed for nest building based on their thermal or structural properties, although the amounts or properties of the materials used have been recorded for only a very small number of species. Some of the behaviours underlying the construction of nests can be indirectly determined by careful deconstruction of the structure and measurement of the biomechanical properties of the materials used. Here we examined this idea in an investigation of Bullfinch (Pyrrhula pyrrhula) nests as a model for open-nesting songbird species that construct a “twig” nest, and tested the hypothesis that materials in different parts of nests serve different functions. The quantities of materials present in the nest base, sides and cup were recorded before structural analysis. Structural analysis showed that the base of the outer nests were composed of significantly thicker, stronger and more rigid materials compared to the side walls, which in turn were significantly thicker, stronger and more rigid than materials used in the cup. These results suggest that the placement of particular materials in nests may not be random, but further work is required to determine if the final structure of a nest accurately reflects the construction process. PMID:28265501